This report was funded by Luminex (Austin, TX). The authors thank Matthew Silverman PhD (Biomedical Publishing Solutions, Panama City, FL; mattsilver@yahoo.com) for analytical and scientific editing assistance. The authors also thank Harald Klein and Christoph von Eichel-Streiber of tgcBIOMICS GmbH (Bingen, Germany) for providing the Borrelia antigens used in the study. Human serum samples for technical assay validation and quality control were obtained from: 1) the Multilocal and Serial Prevalence Study on Antibodies against SARS-CoV-2 in Germany via the Department of Epidemiology, Helmholtz Centre for Infection Research, Braunschweig, Germany; and 2)the Department of Neurology, S&#228;chsisches Krankenhaus Rodewisch (Rodewisch, Germany). Approval for use of human samples was granted by the Ethics Committee of the Hannover Medical School, Germany (9086_BO_S_2020).

Appropriate Institutional Review Board/Ethics Committee approval was received for the use of human serum samples in this experimental series. Samples were anonymized residual materials from a German national study of SARS-CoV-2 seroprevalence14. Approval for the use of human samples was granted by the Ethics Committee of the Hannover Medical School, Germany (9086_BO_S_2020). A total of 21 human serum samples were used in the current study.
1. Ethical approval for the use of human samples
<ol>
	<li>Obtain appropriate ethical approvals for the use of human samples.</li>
</ol>
2. Reagents and equipment
<ol>
	<li>Human serum samples: Perform technical assay validation and quality control using serum samples from persons previously diagnosed with Lyme borreliosis or from demonstrated Borrelia-negative immune status12,14.</li>
	<li>Single-Reporter Instrumentation. Use a two-channel single-reporter instrument (Table of Materials) for the initial assay development and technical validation. 
	NOTE: The single-reporter system has two lasers: 1) identifies and quantifies bead set-specific fluorescence to discriminate different bead sets, if used (Classification Channel), and 2) detects and quantifies bead-bound target-specific phycoerythrin (PE) fluorescence (Reporter Channel; 532 nm excitation, &#34;orange&#34; 565-585 nm emission). Thus, only a single antibody isotype class (e.g., either IgG or IgM) can be analyzed at one time using the single Reporter Channel.
	<ol>
		<li>Perform initial validation studies to assess anti-Borrelia IgG and IgM separately, in a single-reporter 96-well format that uses PE-labeled detection reagents for both antibody classes. 
		NOTE: The current assay evaluates circulating IgGs specific for Borrelia antigen VlsE and two variants of DbpA, and circulating IgM specific for antigen OspC, as representative examples. The assay can be expanded to evaluate serum immunoreactivity against other anti-Borrelia antigens, as desired12.</li>
	</ol>
	</li>
	<li>Dual-Reporter Instrumentation. Use a three-channel dual-reporter instrument (Table of Materials) that allows concurrent IgG/IgM analysis in the same reaction, for the development and technical validation of the dual IgM/IgG assay (detailed below). This instrument has 3 total fluorescence-detecting channels, of which 2 are Reporter Channels that evaluate targeted Ig-associated signals. 
	&#8203;NOTE: The dual-reporter system has three lasers: 1) identifies and quantifies bead set-specific fluorescence (Classification Channel); 2) detects and quantifies target-specific phycoerythrin (PE) fluorescence (Reporter Channel 1; 532 nm excitation, &#34;orange&#34; 565-585 nm emission), and 3) evaluates target-specific Brilliant Violet 421 (BV421) fluorescence of a second target analyte (Reporter Channel 2; 405 nm excitation, &#34;blue&#34; 421-441 nm emission). The dual-reporter system is compatible with both 96-well and 384-well microtiter plate (semi-automated handling) assay formats. The general assay scheme is shown in Figure 1. The protocol steps are detailed below.</li>
</ol>
3. Antigen coupling
<ol>
	<li>Couple the Borrelia antigens to magnetic, carboxylated and fluorescent color-coded 6.5&#181;m microspheres (beads; Table of Materials) using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/sulfo-N-hydroxysuccinimide (sNHS) chemistry. 
	NOTE: A detailed description can be found in reference11and reference12. Find the coupling concentration of each antigen in Table 1. Coupled beads should be stored in the dark at 4 &#176;C until use. All buffers used in coupling and detection reactions are detailed in the Supplemental Materials.</li>
</ol>
4. Assay procedure: Single-reporter IgG or IgM serological assay: 96-well format
<ol>
	<li>Dilute the Sample in 2 steps (2 steps, both in 96-well plates; 200-fold serum sample dilution in assay buffer). 
	NOTE: The assay buffer composition is a 1:4 mixture of Low Cross Buffer: PBS containing 1% (w/v) bovine serum albumin. Tween-20 is added to the mixture to a final concentration of 0.05 % (v/v).
	<ol>
		<li>Sample dilution step 1: Mix 5 &#181;L of the serum sample with 120 &#181;L of the assay buffer (25-fold dilution).</li>
		<li>Sample dilution step 2: Dilute the 25-fold sample dilution additionally 8-fold by mixing 10 &#181;L of the dilution with 70 &#181;L of the assay buffer to make the final sample dilution 200-fold.</li>
	</ol>
	</li>
	<li>Magnetic bead mix dilution
	<ol>
		<li>Prepare a bead mix containing 1.0 &#215; 106 beads/mL per bead population (i.e., per unique target antigen).</li>
		<li>Dilute the prepared bead mix 25-fold in assay buffer to make the final bead concentration in this diluted suspension is now 4 &#215; 104 beads/mL per bead population (i.e., per unique target antigen).</li>
	</ol>
	</li>
	<li>Serum sample incubation with beads
	<ol>
		<li>Pipette 25 &#181;L of diluted coupled multiplex bead suspension (containing 4.0 &#215; 104 beads/set/mL) into assigned wells of a 96-well half-area microtiter plate (Table of Materials).</li>
		<li>Add 25 &#181;L of 200-fold diluted serum sample (from Step 4.1 above) into appropriate wells containing 25 &#181;L of coupled bead suspension. 
		NOTE: This produces an additional 2-fold dilution, so the final serum sample dilution in the well is 400-fold and the final bead count is 1000 beads/bead set/50-&#181;L reaction.</li>
		<li>Cover the 96-well reaction plate with a microplate seal (adhesive foil or plastic plate covers).</li>
		<li>Incubate plate for 2 h at 20 &#176;C, at 750 rpm on a plate shaker.</li>
	</ol>
	</li>
	<li>Bead washing
	<ol>
		<li>Remove the 96-well reaction plate from the plate shaker and carefully remove the adhesive plate seal.</li>
		<li>Put the 96-well reaction plate into a plate washer.</li>
		<li>Wash the beads three times with 100 &#181;L wash buffer (1&#215; PBS + 0.05% v/v Tween 20) using the automated magnetic plate washer.</li>
	</ol>
	</li>
	<li>Resuspend washed beads in 100 &#181;L of wash buffer, cover the plate with adhesive foil or plastic plate cover, and shake the plate on a plate shaker for 1 min at 20 &#176;C at 1000 rpm.</li>
	<li>Split the washed beads
	<ol>
		<li>Remove the 96-well reaction plate from the plate shaker and carefully remove the adhesive plate seal.</li>
		<li>Mix reactions by pipetting up and down five times and transfer 50 &#181;L of each 100-&#181;L reaction volume to each of two new 96-well reaction plates, one plate for IgG detection and one for IgM detection.</li>
	</ol>
	</li>
	<li>Detection antibody/reagent incubation 
	NOTE: At this point, target antigen-coupled beads have been incubated with serum samples to extract circulating antibodies in serum (if present) that react with the antigen(s). Reacted beads with bound immunoglobulin have been divided into two plates, and IgG and IgM are now detected and quantified in their separate plates using isotype-specific secondary antibodies with a PE label. Stagger plate handling by 20 min.
	<ol>
		<li>Aspirate the supernatant from the wells containing magnetic beads using the magnetic plate washer.</li>
		<li>For each plate, make the appropriate Ig Detection Reagent mix (either anti-IgG or anti-IgM), containing PE-conjugated goat anti-human IgG (3 &#181;g/mL) or PE-conjugated donkey anti-human IgM (5 &#181;g/mL) in the assay buffer. For each bead-containing well, 30 &#181;L of Detection Reagent is used. Prepare sufficient IgG and IgM Detection Reagent volumes for reaction wells, with sufficient extra to accommodate pipetting losses.</li>
		<li>Pipette 30 &#181;L of IgG Detection Reagent into each well containing reacted beads on the IgG plate and cover the 96-well reaction plate with a microplate seal.</li>
		<li>Pipette 30 &#181;L of IgM Detection Reagent into each well containing reacted beads on the IgM plate and cover the 96-well reaction plate with a microplate seal.</li>
		<li>Incubate for 45 min at 20 &#176;C while shaking at 750 rpm on a plate shaker.</li>
	</ol>
	</li>
	<li>Bead washing
	<ol>
		<li>Remove the 96-well reaction plate from the plate shaker and carefully remove the adhesive plate seal.</li>
		<li>Put the 96-well reaction plate into a magnetic plate washer.</li>
		<li>Wash the beads three times with 100 &#181;L wash buffer using the magnetic plate washer.</li>
	</ol>
	</li>
	<li>Resuspend beads in 100 &#181;L of wash buffer.</li>
	<li>Analyze the results on the single reporter instrument.
	<ol>
		<li>Cover the 96-well reaction plate with a microplate seal.</li>
		<li>Shake the 96-well reaction plate for 3 min at 20 &#176;C, at 1000 rpm on a plate shaker.</li>
		<li>Transfer the 96-well reaction plate from the plate shaker and put in a single-reporter flow analyzer instrument (Table of Materials).</li>
		<li>For each sample, analyze the median fluorescent intensity (MFI) using the following instrument settings: Uptake volume = 80 &#181;L, Count = 50/bead population, Timeout = 60s, Gating = 7,500-15,000)12,13.</li>
	</ol>
	</li>
</ol>
5. Assay procedure: Dual-reporter IgG and IgM serological assay: 96-well format
<ol>
	<li>Sample dilution (2 steps, both in 96-well plates; 200-fold serum sample dilution in assay buffer)
	<ol>
		<li>Sample dilution step 1: Mix 5 &#181;L serum sample with 120 &#181;L assay buffer (25-fold dilution).</li>
		<li>Sample dilution step 2: Dilute the 25-fold sample dilutions an additional 8-fold by mixing 10 &#181;L of the first dilution (25-fold diluted sample from Section 5.1.1) with 70 &#181;L assay buffer (8-fold dilution), to obtain final sample dilution to 200-fold.</li>
	</ol>
	</li>
	<li>Magnetic bead mix dilution
	<ol>
		<li>Prepare a bead mix containing 1.0 &#215; 106 target antigen-coupled beads/mL per bead population (i.e., per unique target antigen). 
		NOTE: In this experimental series, we evaluated both IgG and IgM immunoreactivity against four unique Borrelia antigens in each reaction.</li>
		<li>Dilute the prepared bead mix 50-fold in assay buffer. The bead concentration in this diluted suspension is now 2.0 &#215; 104 beads/mL per bead population. 
		NOTE: The number of beads in the duplex assay reaction is halved from that used in the single-reporter reaction to allow for direct comparability between the two assays and to conserve resources, after preliminary studies confirmed that the fluorescence signal was maintained within the linear range of quantification when using half the number of beads.</li>
	</ol>
	</li>
	<li>Serum sample incubation with beads
	<ol>
		<li>Pipette 25 &#181;L of diluted target antigen-coupled bead suspension (containing 2.0 &#215; 104 beads/set/mL) into pre-assigned wells of a 96-well half-area microtiter plate. The exact number of reaction wells and their placement on the plate depend upon the operator-determined&#160;total number of samples tested and whether single or replicate wells will be run per sample. 
		NOTE: The target antigen-coupled magnetic beads will be reacted with human serum samples. Both anti-Borrelia antigen immunoreactive IgG and IgM, if present in samples, will bind to and be immobilized on the same antigen-coupled beads. Secondary antibody quantification of bound IgG and IgM will then be performed on the same beads in the same reactions, using different fluorophores for IgG and IgM identification that allows their differentiation.</li>
		<li>Add 25 &#181;L of 200-fold diluted serum (from Step 5.1 above) into each well containing 25 &#181;L of mixed target antigen-coupled bead suspension (Step 5.2). 
		NOTE: This produces an additional 2-fold dilution, so the final serum sample dilution in the well is 400-fold, and the final bead count is 500 beads/bead set/50-&#181;L reaction.</li>
		<li>Cover the 96-well reaction plate with a microplate seal (adhesive foil or plastic plate cover).</li>
		<li>Incubate plate with beads for 2 h at 20 &#176;C, at 750 rpm on a plate shaker.</li>
	</ol>
	</li>
	<li>Bead washing (to remove&#160;excess serum sample)
	<ol>
		<li>Remove the 96-well reaction plate from the plate shaker and remove the adhesive plate seal.</li>
		<li>Put the 96-well reaction plate into a magnetic plate washer.</li>
		<li>Wash the beads three times with 100 &#181;L wash buffer using the magnetic plate washer.</li>
	</ol>
	</li>
	<li>Aspirate final wash volume from beads after the last washing step.</li>
	<li>Detection antibody (Incubation - Part I)
	<ol>
		<li>Make fresh IgG and IgM Dual Detection Reagent containing biotinylated goat anti-human IgG (1 &#181;g/mL) together with PE-conjugated donkey anti-human IgM (5 &#181;g/mL) in assay buffer. For each bead-containing well, 30 &#181;L of Dual Detection Reagent is used. Prepare sufficient IgG and IgM Dual Detection Reagent volumes for reaction wells, with sufficient extra to accommodate pipetting losses.</li>
		<li>Pipette 30 &#181;L of IgG and IgM Dual Detection Reagent into each assigned well and cover the 96-well reaction plate with a microplate seal.</li>
		<li>Incubate the plate for 45 min at 20 &#176;C while shaking at 750 rpm on a plate shaker.</li>
	</ol>
	</li>
	<li>Bead washing (to remove excess detection antibodies)
	<ol>
		<li>Remove the 96-well reaction plate from the plate shaker and carefully remove the adhesive plate seal.</li>
		<li>Put the 96-well reaction plate into an automated magnetic plate washer.</li>
		<li>Wash the beads three times with 100 &#181;L wash buffer using the automated magnetic plate washer.</li>
	</ol>
	</li>
	<li>Aspirate final wash volume from beads after the last washing step.</li>
	<li>Streptavidin-conjugated reporter (Incubation - Part II)
	<ol>
		<li>Dilute fresh BV421-labeled Streptavidin in assay buffer to a concentration of 0.2 &#181;g/mL. For each bead-containing well, 30 &#181;L of BV421-labeled Streptavidin is used. Prepare sufficient BV421-labeled Streptavidin volume for reaction wells, with sufficient extra to accommodate pipetting losses.</li>
		<li>Pipette 30 &#181;L of diluted BV421-Streptavidin into each reaction well and cover the 96well reaction plate with the microplate seal.</li>
		<li>Incubate the plate for 30 min at 20 &#176;C while shaking at 750 rpm on a plate shaker.</li>
	</ol>
	</li>
	<li>Wash beads (to remove excess BV421-Streptavidin)
	<ol>
		<li>Remove the 96-well reaction plate from the plate shaker and carefully remove the adhesive plate seal.</li>
		<li>Put the 96-well reaction plate into the magnetic plate washer.</li>
		<li>Wash the beads three times with 100 &#181;L wash buffer using the automated magnetic plate washer.</li>
	</ol>
	</li>
	<li>Resuspend beads within wells to a final volume of 100 &#181;L in wash buffer.</li>
	<li>Analyze results on the dual-reporter instrument
	<ol>
		<li>Cover the 96-well reaction plate with a microplate seal.</li>
		<li>Incubate the 96-well reaction plate for 3 min at 20 &#176;C, at 1000 rpm on a plate shaker.</li>
		<li>Transfer the 96-well reaction plate from the plate shaker to the dual-reporter flow analyzer instrument (Table of Materials).</li>
		<li>Evaluate sample median fluorescent intensity (MFI) according to manufacturer instructions (Instrument Settings: Dual-Reporter Mode, Uptake volume = 80 &#181;L, Count =&#160;50/bead population, Timeout = 60s, Gating = 7,500-15,000).</li>
	</ol>
	</li>
</ol>
6. Dual reporter IgG and IgM serological assay: 384-well semi-automated format
<ol>
	<li>Perform the dual-reporter assay in 384-well plate format using the assay steps detailed in section 5, but process samples using a pipetting robot and automated magnetic plate washer (Table of Materials). In 384-well format, shake plates during incubations and washes at 1450 rpm, and before measuring fluorescence, shake the plate for 5 min at 21 &#176;C and 1800 rpm.</li>
</ol>

Multiplex Immunoassay for Borrelia-Specific IgG and IgM in Serum

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The authors have nothing to disclose.

This report highlights the development of a two-reporter bead-based Borrelia immunoassay that reproducibly and sensitively determines anti-Borrelia immunoreactivity in serum samples12. The various pathogenic Borrelia species that cause Lyme borreliosis can be differentiated by variant-specific antigen heterogeneity6,7,8,9. The multiplexed assay concurrently evaluates IgG- and IgM-mediated anti-Borrelia immunoreactivity within the same reaction well, thereby conserving reagents, labor, and sample material otherwise needed to perform two singleplex assays separately. Comparing IgM and IgG responses over time may allow better tracking of disease progression as IgM-to-IgG seroconversion occurs after infection6.
The dual-reporter system uses two different detection antibody systems13,15. Related experiments demonstrated no significant detectable cross-reactivity between Borrelia anti-IgM and anti-IgG detection systems when both antibody classes were analyzed together in the same reaction well12. Considering the lower binding affinity of IgM versus IgG antibodies16,17, we chose a PE-conjugated detection antibody for IgM detection (the first reporter channel of the dual-reporter instrument) because PE is one of the strongest-emitting fluorophores routinely used in immunoassays18. For IgG evaluation, we used a biotinylated detection antibody that was subsequently illuminated with BV421-conjugated streptavidin (the second reporter channel of the instrument)19. Despite the additional 30 min incubation step compared to the single-reporter system, the dual-reporter system yields twice the information per reaction. Overall, the dual-reporter multiplexed assay requires less cumulative time and material inputs than running two single-reporter assays.
Strong performance and stability of the multiplexed Borrelia assay was exemplified by high reproducibility in intra- and inter-assay precision studies, and by demonstration of dilution linearity and dilution parallelism over a wide range of sample concentrations for both IgG and IgM assessment. We observed higher absolute fluorescence emission levels for the same fluorophores using the single-channel instrument versus the dual-channel system (&#8776;1.7&#215; higher with PE), attributable to differences in the optics and calibration settings between the two instruments (Figure 4). Nonetheless, fluorescence emission curves with both fluorophores remained within the linear range of both instruments at high and low sample dilution extremes, and any discrepancy in absolute fluorescence measured did not affect the classification of Borrelia exposure status.12
A major advantage of this bead-based Borrelia multiplex assay is the ease with which the assay can be modified or expanded to evaluate different or additional analytes, e.g., to detect antibodies against antigens of further Borrelia species. xMAP magnetic bead sets contain different dye combinations that can be distinguished in the instrument&#39;s Classification Channel and can theoretically be implemented into multiplex assays that can concurrently evaluate up to 500 unique analytes within the same sample. While the current study highlights four representative Borrelia antigens to demonstrate assay functionality and stability and to compare the single- and dual-reporter system, the final assay interrogates eight antigens that together can identify all five clinically-relevant Borrelia pathogens circulating throughout Europe and North America12.
High-throughput performance is possible using standard 384-well microtiter plates in a semi-automated assay format. Assay and instrument compatibility with both 96- and 384-well plates allows the Borrelia multiplex assay to be used as an efficient screening tool for rapidly analyzing large sample sets, such as national studies20. Manual performance of the assay remains possible for smaller sample sets using smaller 96-well plates.
Study limitations include the comparative evaluation of only a few Borrelia immunoreactivity targets in a small number of human serum samples. However, the original study did confirm that assay performance for both IgG and IgM was maintained when analyzing eight antigens from all five known Borrelia species within a larger sample set12. Also, the dual-reporter instrument can only assess two antibody isotypes simultaneously within each reaction, so complete isotype profiling would necessitate performing additional assay reactions13.
In conclusion, this report details the successful merger and conversion of bead-based single-reporter immunoassays into dual-reporter assays that can simultaneously evaluate pathogenic Borrelia-specific IgG and IgM antibodies in human serum samples. This combined approach saves total time, material, and labor inputs to generate the same data volume as two independent single-reporter assays. The multiplex assay can be scaled from 96-well to 384-well microtiter plate format and can be semi-automated by the use of robotic plate and liquid handling instrumentation, making it suitable for high-throughput applications such as large population surveys. Bead-based dual-reporter assay systems have previously demonstrated utility in evaluating, for instance, immune responses to other viral and bacterial pathogens13,21, assessing allogeneic antibody responses against HLA epitopes in organ transplantation22, and exploring mechanisms of autoimmune disease23. The current report detailed the use of multiplex technology to identify exposure to the Borrelia pathogens that cause Lyme disease, as an example of how laboratories can adapt this approach for exploring complex immune mechanisms in diverse pathologies.

An erratum was issued for:&#160;<a href="https://www.jove.com/t/65323">Simultaneous Detection of Different Antibody Classes in a Multiplexed Serological Test</a>. The Authors section was updated to correct an Affiliation. It was updated from:
Julia H&#228;ring1 
Tanja Michel1 
Matthias Becker1 
Daniel Junker1 
Tatia Tchitchagua2 
Olaf Leschnik2 
Berit Lange3,4 
Stefanie Castell3,4 
G&#233;rard Krause3,4 
Monika Strengert3 
Alex Dulovic1 
Nicole Schneiderhan-Marra1 
1NMI Natural and Medical Sciences Institute, University of T&#252;bingen 
2Department of Neurology, S&#228;chsisches Krankenhaus Rodewisch 
3Department of Epidemiology, Helmholtz Centre for Infection Research 
4German Centre for Infection Research (DZIF)
to:
Julia H&#228;ring1 
Tanja Michel1 
Matthias Becker1 
Daniel Junker1 
Tatia Tchitchagua2 
Olaf Leschnik2 
Berit Lange3,4 
Stefanie Castell3,4 
G&#233;rard Krause3,4 
Monika Strengert3 
Alex Dulovic1 
Nicole Schneiderhan-Marra1 
1NMI Natural and Medical Sciences Institute at the&#160;University of T&#252;bingen 
2Department of Neurology, S&#228;chsisches Krankenhaus Rodewisch 
3Department of Epidemiology, Helmholtz Centre for Infection Research 
4German Centre for Infection Research (DZIF)

An erratum was issued for:&#160;<a href="https://www.jove.com/t/65323">Simultaneous Detection of Different Antibody Classes in a Multiplexed Serological Test</a>. The Authors section was updated to correct an Affiliation.

Erratum: Simultaneous Detection of Different Antibody Classes in a Multiplexed Serological Test

Lyme borreliosis is the most common tick-borne infectious disease in moderate climates of the northern hemisphere1. It is caused by spirochete bacteria of the genus Borrelia, with five known human pathogens that vary in geographical distribution2. The main pathogenic Borrelia species in Europe are B. afzelii and B. garinii, with B. burgdorferi s.s., B. spielmanii and B. bavariensis implicated less frequently. In North America, B. burgdorferi s.s. is the sole causative agent of Lyme borreliosis2,3. Borrelia pathogens are transmitted by members of the tick genus Ixodes, with transmission able to occur within 24 hours of tick bite4.
Lyme borreliosis diagnosis is typically made by clinical symptoms and subsequently confirmed by serology. In both Europe and North America, diagnostic guidelines recommend a two-step testing series consisting of an enzyme-linked immunosorbent assay (ELISA) with a reflex immunoblot to evaluate antibody response against Borrelia specific antigens1,5,6,7,8,9. However, this approach lacks sensitivity and is suboptimal, particularly in the early phase of infection when seroconversion may be incomplete and anti-Borrelia IgG and IgM titers are too low6.
Multiplex immunoassays improve upon traditional immunoassays that measure only one target at a time, and can simultaneously evaluate multiple antibody isotype responses against one or more antigens10,11,12. Assays such as ELISAs are limited to identifying and quantifying a single analyte per reaction, in the current case&#160;either circulating IgG or IgM induced against a single bacterial antigen after infection with Borrelia. This report illustrates using bead-based analyte profiling technology for the development of a multiplex immunoassay that simultaneously detects both IgG and IgM antibodies against any of the herein chosen Borrelia antigens in human serum samples. We selected four antigens that together cover the most common pathogenic Borrelia species native in Europe (B. garinii, B. afzelii, B. burgdorferi s.s.) and North America (B. burgdorferi s.s.) (Table 1)2,3. This allows decisive pathogen identification and the ability to discern early IgM and later, more durable, IgG immunoreactivity in patient samples.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Target Isotype</td>
			<td>Reporter Channel</td>
			<td>Antigen</td>
			<td>Borrelia Species</td>
			<td>Strain</td>
			<td>Antigen Coupling Concentration</td>
		</tr>
		<tr>
			<td>IgM</td>
			<td>PE</td>
			<td>OspC</td>
			<td>B. garinii</td>
			<td>20047</td>
			<td>5.0 &#181;g/106 beads</td>
		</tr>
		<tr>
			<td>IgG</td>
			<td>BV421</td>
			<td>VlsE</td>
			<td>B. burgdorferi s.s</td>
			<td>B31</td>
			<td>1.25 &#181;g/106 beads</td>
		</tr>
		<tr>
			<td>IgG</td>
			<td>BV421</td>
			<td>DbpA</td>
			<td>B. burgdorferi s.s.</td>
			<td>ZS7</td>
			<td>10.0 &#181;g/106 beads</td>
		</tr>
		<tr>
			<td>IgG</td>
			<td>BV421</td>
			<td>DbpA</td>
			<td>B. afzelii</td>
			<td>PKo</td>
			<td>5.0 &#181;g/106 beads</td>
		</tr>
	</tbody>
</table>
Table 1: Representative Borrelia antigens used for multiplex assay development.
We initially developed a single-reporter immunoassay that detected either anti-Borrelia antigen IgG or IgM antibodies in two separate reactions and then merged these assays into a dual-reporter multiplex assay that measures both antibody isotypes in the same reaction mixture. Magnetic beads are coupled to a pathogen target antigen of interest, and then incubated with patient serum samples. The bead-coupled antigen gets recognized by, and captures, both circulating IgG and IgM in serum that is generated in an immune response against that pathogen antigen. Assay IgG versus IgM specificity is determined by the selection of a secondary antibody that binds to either IgG or IgM, each with a distinct fluorophore signal associated with the two secondary antibodies. Each fluorescent signal is detected in one of the instrument&#39;s two Reporter Channels (i.e., dual-reporter) that has a different excitation laser and emission capture specific for the single fluorophore used to detect either IgG or IgM (here Brilliant Violet 421 or phycoerythrin, respectively). The instrument Classification Channel identifies the color-coded dye that is inherent to different bead sets. Thus, multiple target antigens can be coupled to differently dyed beads, and the bead sets mixed together and used to comprehensively assess diverse anti-pathogen immunoreactivity in serum samples. The Classification Channel identifies each individual bead set (i.e., specific antigen) and measures the fluorescence associated with IgG or IgM against that antigen. The resulting multiplex assay saves time and resources versus less comprehensive classical testing and accurately catalogs Lyme immunoreactivity in limited sample volumes.&#160;Whereas a similar dual-reporter approach has been previously used to categorize immune responses in other pathologies such as SARS-CoV-2 infection13, this report details the application of multiplex fluorescent assay technology for characterizing immunoreactivity in Lyme borreliosis.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Antibodies and Detection Reagents</td>
			<td>Source</td>
			<td>Catalog Number</td>
			<td></td>
		</tr>
		<tr>
			<td>Biotinylated Goat Anti-Human IgG</td>
			<td>Jackson ImmunoResearch (Dianova)</td>
			<td>109-066-098&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Brilliant Violet 421-Streptavidin</td>
			<td>BD Biosciences</td>
			<td>563259</td>
			<td></td>
		</tr>
		<tr>
			<td>Donkey Anti-Human IgM&#160;</td>
			<td>Jackson ImmunoResearch (Dianova)</td>
			<td>709-116-073</td>
			<td></td>
		</tr>
		<tr>
			<td>Borrelia Antigens</td>
			<td>tgcBIOMICS (Bingen, Germany)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Coupling Reagents</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>1-Ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC)</td>
			<td>Thermo Scientific Pierce</td>
			<td>77149 ProteoChem (100 mg)</td>
			<td></td>
		</tr>
		<tr>
			<td>10x PBS</td>
			<td>Fisher Scientific</td>
			<td>BP399-4</td>
			<td></td>
		</tr>
		<tr>
			<td>BSA</td>
			<td>Carl Roth</td>
			<td>T844.3</td>
			<td></td>
		</tr>
		<tr>
			<td>MES (2-ethanesulfonic acid; zwitterionic buffer)</td>
			<td>Carl Roth</td>
			<td>4256.2</td>
			<td></td>
		</tr>
		<tr>
			<td>Na2HPO4</td>
			<td>Carl Roth</td>
			<td>4984.1</td>
			<td></td>
		</tr>
		<tr>
			<td>ProClin300</td>
			<td>Sigma</td>
			<td>48914-U</td>
			<td></td>
		</tr>
		<tr>
			<td>Sulfo-NHS (N-hydroxysulfosuccinimide)</td>
			<td>Thermo Scientific Pierce</td>
			<td>24510 (500 mg)</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Thermo Scientific</td>
			<td>85111</td>
			<td></td>
		</tr>
		<tr>
			<td>Instrumentation and Ancillary Lab Supplies</td>
			<td>Source</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>384-well plate</td>
			<td>Corning, Cat# 3570</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>96-well deep-well plates</td>
			<td>ThermoFisher Scientific, Cat# 95040450</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>96-well half-area plates&#160;</td>
			<td>Corning, Cat# 3690</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>BioTek 405 TS Plate Washer</td>
			<td>BioTek Instruments/Agilent Technologies, Santa Clara, CA&#160;</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>BioTek MultiFlo FX Plate Washer</td>
			<td>BioTek Instruments/Agilent Technologies, Santa Clara, CA&#160;</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>DynaMag Spin Magnet (for isolating beads in microcentrifuge tubes)</td>
			<td>ThermoFisher, Cat# 12320D</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Flexmap 3D (two-channel, single-reporter instrument)</td>
			<td>Luminex Corp., Austin, TX</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>KingFisher Magnetic Particle Processor (for isolating beads in 96-well plates)&#160;</td>
			<td>ThermoFisher, Cat# A31508</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MagPlex Microspheres (magnetic, fluorescent, 6.5-&#181;m-diameter beads)</td>
			<td>Luminex Corp., Austin, TX</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SmartBlock Plates</td>
			<td>Eppendorf, Cat# 5363000039</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ThermoMixer C</td>
			<td>Eppendorf, Cat# 5382000015</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ThermoTop</td>
			<td>Eppendorf, Cat# 5308000003</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>xMAP Intelliflex (three-channel, dual-reporter instrument)</td>
			<td>Luminex Corp., Austin, TX</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

simultaneous detection of different antibody classes in a multiplexed serological test

To monitor the progression of infectious diseases, it is useful to assess immunoreactivity against various antigenic determinants, and measure different antibody isotypes because they appear at different stages of the host immune response. With Lyme borreliosis, the pathogenic agent can be one of the multiple members of the Borrelia species. Therefore, correct sample classification requires evaluating the immunoreactivity against different antigens of different Borrelia species. Additionally, anti-pathogen IgG and IgM responses can have different elicitation time courses during disease progression. Here we demonstrate the development of a two-reporter multiplex immunoassay that has utility in identifying Borrelia-specific immune response in human serum samples by simultaneously evaluating both IgG and IgM immunoreactivity against different bacterial antigens in the same reaction well. This dual-reporter approach retains the analytical performance of single-reporter methods while conserving time and resources and reducing sample size requirements. This assay allows essentially double the serological information to be generated from a blood sample in half the time.

Experimental overview 
The general schemes for the single-reporter and dual-reporter bead-based Borrelia assays are shown in Figure 1. For single antibody targets (i.e., IgG or IgM) generated against a given Borrelia antigen, both antibody classes were evaluated independently in human serum samples using a PE-conjugated anti-isotype antibody for reporting. For the dual-reporter assay with simultaneous analysis of both IgG and IgM immunoreactivity, Borrelia antigen-specific IgG detection used a biotinylated anti-human IgG + BV421-labeled Streptavidin (blue fluorescence) reporter system, while retaining the PE-conjugated reporter (orange fluorescence) for IgM detection. The workflow of the dual-reporter assay is similar to the single-reporter assay, with the exception of an additional 30-minute detection system incubation with the second-channel fluorescence detection reagent BV421-Streptavidin.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/65323/65323fig01.jpg" /> 
Figure 1: Schematic of the single-reporter and dual-reporter bead-based Borrelia assays. (A) The single-reporter instrument was used to develop and initially validate the bead-based assay that characterized either anti-Borrelia IgG or IgM individually, both using a phycoerythritin (PE) fluorescent reporter label that emits signal in the &#34;orange&#34; spectra. Any desired Borrelia antigen can be coupled to the beads and used to capture and quantify either IgG or IgM present in serum samples. Two separate immunoassays are needed to evaluate both IgG and IgM reactivity against a given antigen. (B) The dual-reporter system allowed simultaneous analysis of serum samples for both IgG and IgM antibodies against any individual Borrelia antigen in the same well. This approach uses the same PE-conjugated detection antibody to target anti-Borrelia IgM, but replaces the IgG detection from a PE-based system to using a biotinylated primary detection antibody and BV421-labeled Streptavidin (a &#34;blue&#34; emitter) that needs an additional detection system incubation step of 30 minutes. <a href="https://www.jove.com/files/ftp_upload/65323/65323fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Intra-assay precision 
Spearman correlation analysis for three representative Borrelia antigens (Figure 2) demonstrated uniform reproducibility of MFI values when detecting anti-Borrelia antibodies present in human sera.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/65323/65323fig02.jpg" /> 
Figure 2: Intra-assay Precision of the dual-reporter bead-based Borrelia assay. Spearman&#39;s correlation analysis showed a high intra-assay precision of the dual-reporter assay when a PE detection system was used to detect Borrelia-specific IgM antibodies (A) and a BV421 detection system was used to detect Borrelia specific IgG antibodies (B, C). A total of 21 serum samples were analyzed in duplicates using a semi-automated procedure. In each graph, MFI signals were plotted against each other and analyzed by linear regression. A linear curve (x=y) shown as a red dashed line indicates identical MFI signals for detection systems. <a href="https://www.jove.com/files/ftp_upload/65323/65323fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Inter-assay precision 
Good assay-to-assay reproducibility was observed with the dual-reporter assay. Levey-Jennings charts (Figure 3) with MFI values of a quality control sample measured over seven independent runs demonstrated the high inter-assay precision for all representative antigens. The average percent Coefficient of Variation (CV% = standard deviation/mean &#215; 100) of the four representative Borrelia antigens was 5.3%.
Dilution linearity 
Because the original single-reporter assay and the new dual-reporter assay employ different flow cytometric platforms, we compared median fluorescence outputs of the same antigen immunoassay between the two flow cytometry instruments (Figure 4). Sample dilution series provided linear dilution curves for both IgM and IgG evaluation, with good parallelism of dose-response between instruments through the entire dilution range evaluated (1:100-1:12,800).
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/65323/65323fig03.jpg" /> 
Figure 3: Inter-assay precision of the dual-reporter bead-based Borrelia assay. For the evaluation of the inter-assay precision, Borrelia-specific IgM (A) and IgG (B-D) antibody response of a quality control sample was analyzed over seven independent runs, in duplicate wells each time. Assays were performed manually. MFI values were plotted in a Levey-Jennings chart. A green line gives the mean of all values. Two red dashed lines indicate the tolerance range of the inter-assay precision. This was calculated from the mean value &#177; 2.5 times the standard deviation (2.5 S.D.). <a href="https://www.jove.com/files/ftp_upload/65323/65323fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/65323/65323fig04.jpg" /> 
Figure 4: Dilution linearity of the dual-reporter bead-based Borrelia assay. At sample dilutions of 100-fold to 12,800-fold, the dilution curves for both IgM detection (A) and IgG detection (B) were similar when performed manually with the single-reporter instrument and the dual-reporter instrument. At all tested dilutions, MFI values were slightly higher using the single-reporter instrument (red symbols) than the dual-reporter instrument (blue symbols). Shown are dilution curves for 2 representative antigens, with each dilution point representing the average measurement of triplicate wells with standard deviation (SD *) indicated by error bars. Note: Small SDs are not visible at this scale. <a href="https://www.jove.com/files/ftp_upload/65323/65323fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Supplemental Materials. <a href="https://www.jove.com/files/ftp_upload/65323/Supplementary_FIle_Buffer_Compositions.zip" target="_blank">Please click here to download this File.</a>

Watch this Scientific Journal Video about Expanding the Scope of Multiplex Immunoassays for Lyme Borreliosis Diagnostics and Pathogen Research at JoVE.com

Author Spotlight: Expanding the Scope of Multiplex Immunoassays for Lyme Borreliosis Diagnostics and Pathogen Research 

A three-channel dual-reporter fluorescence flow analysis system was used to develop a bead-based multiplex immunoassay that simultaneously evaluates serum samples for IgG and IgM elicited against multiple antigens of different Borrelia species that cause Lyme borreliosis in Europe and North America.

Simultaneous Detection of Different Antibody Classes in a Multiplexed Serological Test

To monitor the progression of infectious diseases, it is useful to assess immunoreactivity against various antigenic determinants, and measure different ...

simultaneous-detection-different-antibody-classes-multiplexed

Research

JoVE Journal

Immunology and Infection

1.2K Views.  NMI Natural and Medical Sciences Institute at the University of Tübingen. A three-channel dual-reporter fluorescence flow analysis system was used to develop a bead-based multiplex immunoassay that simultaneously evaluates serum samples for IgG and IgM elicited against multiple antigens of different Borrelia species that cause Lyme borreliosis in Europe and North America.

Video: Author Spotlight: Expanding the Scope of Multiplex Immunoassays for Lyme Borreliosis Diagnostics and Pathogen Research 

Combination of Adhesive-tape-based Sampling and Fluorescence in situ Hybridization for Rapid Detection of Salmonella on Fresh Produce

This protocol describes a simple approach for adhesive-tape-based sampling of tomato and other fresh produce surfaces, followed by on-tape fluorescence in situ hybridization (FISH) for rapid culture-independent detection of Salmonella spp. Cell-charged tapes can also be placed face-down on selective agar for solid-phase enrichment prior to detection. Alternatively, low-volume liquid enrichments (liquid surface miniculture) can be performed on the surface of the tape in non-selective broth, followed by FISH and analysis via flow cytometry. To begin, sterile adhesive tape is brought into contact with fresh produce, gentle pressure is applied, and the tape is removed, physically extracting microbes present on these surfaces. Tapes are mounted sticky-side up onto glass microscope slides and the sampled cells are fixed with 10% formalin (30 min) and dehydrated using a graded ethanol series (50, 80, and 95%; 3 min each concentration). Next, cell-charged tapes are spotted with buffer containing a Salmonella-targeted DNA probe cocktail and hybridized for 15 - 30 min at 55&deg;C, followed by a brief rinse in a washing buffer to remove unbound probe. Adherent, FISH-labeled cells are then counterstained with the DNA dye 4',6-diamidino-2-phenylindole (DAPI) and results are viewed using fluorescence microscopy. For solid-phase enrichment, cell-charged tapes are placed face-down on a suitable selective agar surface and incubated to allow in situ growth of Salmonella microcolonies, followed by FISH and microscopy as described above. For liquid surface miniculture, cell-charged tapes are placed sticky side up and a silicone perfusion chamber is applied so that the tape and microscope slide form the bottom of a water-tight chamber into which a small volume (&le; 500 &mu;L) of Trypticase Soy Broth (TSB) is introduced. The inlet ports are sealed and the chambers are incubated at 35 - 37&deg;C, allowing growth-based amplification of tape-extracted microbes. Following incubation, inlet ports are unsealed, cells are detached and mixed with vigorous back and forth pipetting, harvested via centrifugation and fixed in 10% neutral buffered formalin. Finally, samples are hybridized and examined via flow cytometry to reveal the presence of Salmonella spp. As described here, our "tape-FISH" approach can provide simple and rapid sampling and detection of Salmonella on tomato surfaces. We have also used this approach for sampling other types of fresh produce, including spinach and jalape&ntilde;o peppers.

Combination of Adhesive-tape-based Sampling and Fluorescence in situ Hybridization for Rapid Detection of Salmonella on Fresh Produce

This protocol describes a simple adhesive-tape-based approach for sampling of tomato and other fresh produce surfaces, followed by rapid whole cell detection of Salmonella using fluorescence in situ hybridization (FISH).

This protocol describes a simple approach for adhesive-tape-based sampling of tomato and other fresh produce surfaces, followed by on-tape fluorescence in ...

Use of Artificial Sputum Medium to Test Antibiotic Efficacy Against Pseudomonas aeruginosa in Conditions More Relevant to the Cystic Fibrosis Lung

There is growing concern about the relevance of in vitro antimicrobial susceptibility tests when applied to isolates of P. aeruginosa from cystic fibrosis (CF) patients. Existing methods rely on single or a few isolates grown aerobically and planktonically. Predetermined cut-offs are used to define whether the bacteria are sensitive or resistant to any given antibiotic1. However, during chronic lung infections in CF, P. aeruginosa populations exist in biofilms and there is evidence that the environment is largely microaerophilic2. The stark difference in conditions between bacteria in the lung and those during diagnostic testing has called into question the reliability and even relevance of these tests3.
 Artificial sputum medium (ASM) is a culture medium containing the components of CF patient sputum, including amino acids, mucin and free DNA. P. aeruginosa growth in ASM mimics growth during CF infections, with the formation of self-aggregating biofilm structures and population divergence4,5,6. The aim of this study was to develop a microtitre-plate assay to study antimicrobial susceptibility of P. aeruginosa based on growth in ASM, which is applicable to both microaerophilic and aerobic conditions.
 An ASM assay was developed in a microtitre plate format. P. aeruginosa biofilms were allowed to develop for 3 days prior to incubation with antimicrobial agents at different concentrations for 24 hours. After biofilm disruption, cell viability was measured by staining with resazurin. This assay was used to ascertain the sessile cell minimum inhibitory concentration (SMIC) of tobramycin for 15 different P. aeruginosa isolates under aerobic and microaerophilic conditions and SMIC values were compared to those obtained with standard broth growth. Whilst there was some evidence for increased MIC values for isolates grown in ASM when compared to their planktonic counterparts, the biggest differences were found with bacteria tested in microaerophilic conditions, which showed a much increased resistance up to a &gt;128 fold, towards tobramycin in the ASM system when compared to assays carried out in aerobic conditions.
 The lack of association between current susceptibility testing methods and clinical outcome has questioned the validity of current methods3. Several in vitro models have been used previously to study P. aeruginosa biofilms7, 8. However, these methods rely on surface attached biofilms, whereas the ASM biofilms resemble those observed in the CF lung9 . In addition, reduced oxygen concentration in the mucus has been shown to alter the behavior of P. aeruginosa2 and affect antibiotic susceptibility10. Therefore using ASM under microaerophilic conditions may provide a more realistic environment in which to study antimicrobial susceptibility.

Use of Artificial Sputum Medium to Test Antibiotic Efficacy Against Pseudomonas aeruginosa in Conditions More Relevant to the Cystic Fibrosis Lung

Current diagnostic antimicrobial susceptibility testing relies on the planktonic growth of isolates in nutrient rich, aerobic conditions. Here, we employ an alternative artificial sputum medium to study antimicrobial susceptibility of Pseudomonas aeruginosa biofilms under both aerobic and microaerophilic conditions more representative of the cystic fibrosis lung.

There  is growing concern about the relevance of in vitro antimicrobial  susceptibility tests when applied to isolates of P. aeruginosa from  cystic ...

Bioluminescence Imaging of NADPH Oxidase Activity in Different Animal Models

NADPH oxidase is a critical enzyme that mediates antibacterial and antifungal host defense. In addition to its role in antimicrobial host defense, NADPH oxidase has critical signaling functions that modulate the inflammatory response 1. Thus, the development of a method to measure in "real-time" the kinetics of NADPH oxidase-derived ROS generation is expected to be a valuable research tool to understand mechanisms relevant to host defense, inflammation, and injury.
Chronic granulomatous disease (CGD) is an inherited disorder of the NADPH oxidase characterized by severe infections and excessive inflammation. Activation of the phagocyte NADPH oxidase requires translocation of its cytosolic subunits (p47phox, p67phox, and p40phox) and Rac to a membrane-bound flavocytochrome (composed of a gp91phox and p22phox heterodimer). Loss of function mutations in any of these NADPH oxidase components result in CGD. Similar to patients with CGD, gp91phox -deficient mice and p47phox-deficient mice have defective phagocyte NADPH oxidase activity and impaired host defense 2, 13. In addition to phagocytes, which contain the NADPH oxidase components described above, a variety of other cell types express different isoforms of NADPH oxidase.
Here, we describe a method to quantify ROS production in living mice and to delineate the contribution of NADPH oxidase to ROS generation in models of inflammation and injury. This method is based on ROS reacting with L-012 (an analogue of luminol) to emit luminescence that is recorded by a charge-coupled device (CCD). In the original description of the L-012 probe, L-012-dependent chemiluminescence was completely abolished by superoxide dismutase, indicating that the main ROS detected in this reaction was superoxide anion 14. Subsequent studies have shown that L-012 can detect other free radicals, including reactive nitrogen species 15, 16. Kielland et al. 16 showed that topical application of phorbol myristate acetate, a potent activator of NADPH oxidase, led to NADPH oxidase-dependent ROS generation that could be detected in mice using the luminescent probe L-012. In this model, they showed that L-012-dependent luminescence was abolished in p47phox-deficient mice.
We compared ROS generation in wildtype mice and NADPH oxidase-deficient p47phox-/- mice 2 in the following three models: 1) intratracheal administration of zymosan, a pro-inflammatory fungal cell wall-derived product that can activate NADPH oxidase; 2) cecal ligation and puncture (CLP), a model of intra-abdominal sepsis with secondary acute lung inflammation and injury; and 3) oral carbon tetrachloride (CCl4), a model of ROS-dependent hepatic injury. These models were specifically selected to evaluate NADPH oxidase-dependent ROS generation in the context of non-infectious inflammation, polymicrobial sepsis, and toxin-induced organ injury, respectively. Comparing bioluminescence in wildtype mice to p47phox-/- mice enables us to delineate the specific contribution of ROS generated by p47phox-containing NADPH oxidase to the bioluminescent signal in these models.
Bioluminescence imaging results that demonstrated increased ROS levels in wildtype mice compared to p47phox-/- mice indicated that NADPH oxidase is the major source of ROS generation in response to inflammatory stimuli. This method provides a minimally invasive approach for "real-time" monitoring of ROS generation during inflammation in vivo.

NADPH oxidase is the major source of reactive oxygen species (ROS) in phagocytes. Because of the ephemeral nature of ROS, it is difficult to measure and monitor ROS levels in living animals. A minimally invasive method for serial quantification of ROS in living mice is described.

NADPH oxidase is a critical enzyme that mediates antibacterial and antifungal host defense. In addition to its role in antimicrobial host defense, NADPH ...

Methods for Quantitative Detection of Antibody-induced Complement Activation on Red Blood Cells

Antibodies against red blood cells (RBCs) can lead to complement activation resulting in an accelerated clearance via complement receptors in the liver (extravascular hemolysis) or leading to intravascular lysis of RBCs. Alloantibodies (e.g. ABO) or autoantibodies to RBC antigens (as seen in autoimmune hemolytic anemia, AIHA) leading to complement activation are potentially harmful and can be - especially when leading to intravascular lysis - fatal1. Currently, complement activation due to (auto)-antibodies on RBCs is assessed in vitro by using the Coombs test reflecting complement deposition on RBC or by a nonquantitative hemolytic assay reflecting RBC lysis1-4. However, to assess the efficacy of complement inhibitors, it is mandatory to have quantitative techniques. Here we describe two such techniques. First, an assay to detect C3 and C4 deposition on red blood cells that is induced by antibodies in patient serum is presented. For this, FACS analysis is used with fluorescently labeled anti-C3 or anti-C4 antibodies. Next, a quantitative hemolytic assay is described. In this assay, complement-mediated hemolysis induced by patient serum is measured making use of spectrophotometric&#160;detection of the released hemoglobin. Both of these assays are very reproducible and quantitative, facilitating studies of antibody-induced complement activation.

Here we describe two assays for measuring complement activation induced by antibodies against red blood cells. The major advantage over the current assays is their quantitative and easy-to-interpret nature.

Antibodies against red blood cells (RBCs) can lead to complement activation resulting in an accelerated clearance via complement receptors in the liver ...

Generation of Two-color Antigen Microarrays for the Simultaneous Detection of IgG and IgM Autoantibodies

Autoantibodies, which are antibodies against self-antigens, are present in many disease states and can serve as markers for disease activity. The levels of autoantibodies to specific antigens are typically detected with the enzyme-linked immunosorbent assay (ELISA) technique. However, screening for multiple autoantibodies with ELISA can be time-consuming and requires a large quantity of patient sample. The antigen microarray technique is an alternative method that can be used to screen for autoantibodies in a multiplex fashion. In this technique, antigens are arrayed onto specially coated microscope slides with a robotic microarrayer. The slides are probed with patient serum samples and subsequently fluorescent-labeled secondary antibodies are added to detect binding of serum autoantibodies to the antigens. The autoantibody reactivities are revealed and quantified by scanning the slides with a scanner that can detect fluorescent signals. Here we describe methods to generate custom antigen microarrays. Our current arrays are printed with 9 solid pins and can include up to 162 antigens spotted in duplicate. The arrays can be easily customized by changing the antigens in the source plate that is used by the microarrayer. We have developed a two-color secondary antibody detection scheme that can distinguish IgG and IgM reactivities on the same slide surface. The detection system has been optimized to study binding of human and murine autoantibodies.

We describe here a method to generate customizable antigen microarrays that can be used for the simultaneous detection of serum IgG and IgM autoantibodies from humans and mice. These arrays allow for high-throughput and quantitative detection of antibodies against any antigens or epitopes of interest.

Autoantibodies, which are antibodies against self-antigens, are present in many disease states and can serve as markers for disease activity. The levels ...

Highly Multiplexed, Super-resolution Imaging of T Cells Using madSTORM

Imaging heterogeneous cellular structures using single molecule localization microscopy has been hindered by inadequate localization precision and multiplexing ability. Using fluorescent nano-diamond fiducial markers, we describe the drift correction and alignment procedures required to obtain high precision in single molecule localization microscopy. In addition, a new multiplexing strategy, madSTORM, is described in which multiple molecules are targeted in the same cell using sequential binding and elution of fluorescent antibodies. madSTORM is demonstrated on an activated T cell to visualize the locations of different components within a membrane-bound, multi-protein structure called the T cell receptor microcluster. In addition, application of madSTORM as a general tool for visualization of multi-protein structures is discussed.

We demonstrate a method to image multiple molecules within heterogeneous nano-structures at single molecule accuracy using sequential binding and elution of fluorescently labeled antibodies.

Imaging heterogeneous cellular structures using single molecule localization microscopy has been hindered by inadequate localization precision and ...

A Protein Microarray Assay for Serological Determination of Antigen-specific Antibody Responses Following Clostridium difficile Infection

We provide a detailed overview of a novel high-throughput protein microarray assay for the determination of anti-Clostridium difficile antibody levels in human sera and in separate preparations of polyclonal intravenous immunoglobulin (IVIg). The protocol describes the methodological steps involved in sample preparation, printing of arrays, assay procedure, and data analysis. In addition, this protocol could be further developed to incorporate diverse clinical samples including plasma and cell culture supernatants. We show how protein microarray can be used to determine a combination of isotype (IgG, IgA, IgM), subclass (IgG1, IgG2, IgG3, IgG4, IgA1, IgA2), and strain-specific antibodies to highly purified whole C. difficile toxins A and B (toxinotype 0, strain VPI 10463, ribotype 087), toxin B from a C. difficile toxin-B-only expressing strain (CCUG 20309), a precursor form of a B fragment of binary toxin, pCDTb, ribotype-specific whole surface layer proteins (SLPs; 001, 002, 027), and control proteins (tetanus toxoid and Candida albicans). During the experiment, microarrays are probed with sera from individuals with C. difficile infection (CDI), individuals with cystic fibrosis (CF) without diarrhea, healthy controls (HC), and from individuals pre- and post-IVIg therapy for the treatment of CDI, combined immunodeficiency disorder, and chronic inflammatory demyelinating polyradiculopathy. We encounter significant differences in toxin neutralization efficacies and multi-isotype specific antibody levels between patient groups, commercial preparations of IVIg, and sera before and following IVIg administration. Also, there is a significant correlation between microarray and enzyme-linked immunosorbent assay (ELISA) for antitoxin IgG levels in serum samples. These results suggest that microarray could become a promising tool for profiling antibody responses to C.difficile antigens in vaccinated or infected humans. With further refinement of antigen panels and a reduction in production costs, we anticipate that microarray technology may help optimize and select the most clinically useful immunotherapies for C. difficile infection in a patient-specific manner.

A Protein Microarray Assay for Serological Determination of Antigen-specific Antibody Responses Following Clostridium difficile Infection

This article describes a simple protein microarray method for profiling humoral immune responses to a 7-plex panel of highly purified Clostridium difficile antigens in human sera. The protocol can be extended for the determination of specific antibody responses in preparations of polyclonal intravenous immunoglobulin.

We provide a detailed overview of a novel high-throughput protein microarray assay for the determination of anti-Clostridium difficile antibody levels in ...

A High-throughput Platform for the Screening of Salmonella spp./Shigella spp.

Fecal-oral transmission of acute gastroenteritis occurs from time to time, especially when people who handled food and water are infected by Salmonella spp./Shigella spp. The gold standard method for the detection of Salmonella spp./Shigella spp. is direct culture but this is labor-intensive and time-consuming. Here, we describe a high-throughput platform for Salmonella spp./Shigella spp. screening, using real-time polymerase chain reaction (PCR) combined with guided culture. There are two major stages: real-time PCR and the guided culture. For the first stage (real-time PCR), we explain each step of the method: sample collection, pre-enrichment, DNA extraction and real-time PCR. If the real-time PCR result is positive, then the second stage (guided culture) is performed: selective culture, biochemical identification and serological characterization. We also illustrate representative results generated from it. The protocol described here would be a valuable platform for the rapid, specific, sensitive and high-throughput screening of Salmonella spp./Shigella spp.

A High-throughput Platform for the Screening of Salmonella spp./Shigella spp.

Salmonella spp./Shigella spp. are common pathogens attributed to diarrhea. Here, we describe a high-throughput platform for the screening of Salmonella spp./Shigella spp. using real-time PCR combined with guided culture.

Fecal-oral transmission of acute gastroenteritis occurs from time to time, especially when people who handled food and water are infected by Salmonella ...

Simultaneous Study of the Recruitment of Monocyte Subpopulations Under Flow In Vitro

The recruitment of monocytes from the blood to targeted peripheral tissues is critical to the inflammatory process during tissue injury, tumor development and autoimmune diseases. This is facilitated through a process of capture from free flow onto the luminal surface of activated endothelial cells, followed by their adhesion and transendothelial migration (transmigration) into the underlying affected tissue. However, the mechanisms that support the preferential and context-dependent recruitment of monocyte subpopulations are still not fully understood. Therefore, we have developed a method that allows the recruitment of different monocyte subpopulations to be simultaneously visualized and measured under flow. This method, based on time-lapse confocal imaging, allows for the unambiguous distinction between adherent and transmigrated monocytes. Here, we describe how this method can be used to simultaneously study the recruitment cascade of pro-angiogenic and non-angiogenic monocytes in vitro. Furthermore, this method can be extended to study the different steps of recruitment of up to three monocyte populations.

Here, we present an integrated protocol that measures monocyte subpopulation trafficking under flow in vitro by use of specific surface markers and confocal fluorescence microscopy. This protocol can be used to explore sequential recruitment steps as well as to profile other leukocyte subtypes using other specific surface markers.

The recruitment of monocytes from the blood to targeted peripheral tissues is critical to the inflammatory process during tissue injury, tumor development ...

Identification of Coding and Non-coding RNA Classes Expressed in Swine Whole Blood

The advent of innovative and increasingly powerful next generation sequencing techniques has opened new avenues into the ability to examine the underlying gene expression related to biological processes of interest. These innovations not only allow researchers to observe expression from the mRNA sequences that code for genes that effect cellular function, but also the non-coding RNA (ncRNA) molecules that remain untranslated, but still have regulatory functions. Although researchers have the ability to observe both mRNA and ncRNA expression, it has been customary for a study to focus on one or the other. However, when studies are interested in both mRNA and ncRNA expression, many times they use separate samples to examine either coding or non-coding RNAs due to the difference in library preparations. This can lead to the need for more samples which can increase time, consumables, and animal stress. Additionally, it may cause researchers to decide to prepare samples for only one analysis, usually the mRNA, limiting the number of biological questions that can be investigated. However, ncRNAs span multiple classes with regulatory roles that effect mRNA expression. Because ncRNA are important to fundamental biologic processes and disorder of these processes in during infection, they may, therefore, make attractive targets for therapeutics. This manuscript demonstrates a modified protocol for the generation mRNA and non-coding RNA expression libraries, including viral RNA, from a single sample of whole blood. Optimization of this protocol, improved RNA purity, increased ligation for recovery of methylated RNAs, and omitted&#160;size selection, to allow capture of more RNA species.

Here, we present a protocol optimized for the processing of coding (mRNA) and non-coding&#160;(ncRNA) globin reduced RNA-seq libraries from a single whole blood sample.

The advent of innovative and increasingly powerful next generation sequencing techniques has opened new avenues into the ability to examine the underlying ...