Name: detection of invasive pulmonary aspergillosis in haematological malignancy patients by using lateral-flow technology
Uploaded: 2012-03-22T12:00:00
Duration: 8 min 1 s
Description: Watch this Scientific Journal Video about Detection of Invasive Pulmonary Aspergillosis in Haematological Malignancy Patients by using Lateral-flow Technology at JoVE.com

Funding to Dr Thornton from Pfizer Limited is gratefully acknowledged.

1. Collection, Storage and Preparation of Serum and Bronchoalveolar Lavage Fluids
<ol>
	<li>Collect serum from untreated blood samples by allowing blood to clot at 4 &deg;C, and store serum as aliquots at -20 &deg;C prior to use. Bronchoalveolar lavage fluids (BAL) should also be stored as aliquots at -20 &deg;C. Note: Storage of serum and BAL as aliquots limits the potential for degradation of the target antigen by repeated freeze-thawing of samples during repeat testing.</li>
	<li>Thaw samples and mix the serum and BAL samples thoroughly by vortexing and centrifuge for 1 min at 14,000 rpm.</li>
	<li>For routine testing of human serum samples, dilute the serum 1:1 (v/v) with tissue culture medium (TCM). TCM consists of RPMI-1640 medium, 10% (v/v) fetal calf serum, 1% (v/v) of 200mM L-glutamine solution, and sodium azide (0.02% w/v) as preservative. The medium is prepared in advance and can be stored at 4 &deg;C for several months. Apply 100 &mu;l of the diluted serum to the LFD.</li>
	<li>For human BAL fluids, and for BAL fluids from animal models, apply 100 &mu;l of neat sample to the LFD, with no pre-treatment.</li>
	<li>For serum from animal models, dilute serum 1:2 (v/v) with phosphate buffered saline containing 4% (w/v) EDTA, heat for 3min in a boiling water bath, centrifuge for 5 min at 14,000 rpm, and apply 100 &mu;l of neat supernatant to the LFD device.</li>
</ol>
2. Application of Serum and BAL to the Lateral-flow Device
<ol>
	<li>Store the lateral-flow devices at room temperature (23 &deg;C). At this temperature, devices are stable for 12 months. Remove the devices from their pouches and place on a level surface.</li>
	<li>Using a sterile pipette tip, apply 100 &mu;l of pre-treated serum or neat BAL sample to the release port of the device.</li>
	<li>Allow the assay to run for 15 min at room temperature, at which time the results of the tests should be recorded. Note: Within seconds the fluid will be seen to migrate by capillary action along the nitrocellulose membrane in the observation window.</li>
</ol>
3. Recording and Interpreting LFD Results
<ol>
	<li>The LFD consists of an internal control line (indicated by the letter C on the plastic housing) and a test line (indicated by the letter T). The control line should always appear irrespective of Aspergillus antigen in the serum or BAL sample. This shows that the assay has run correctly.</li>
	<li>If the Aspergillus antigen is present in the serum or BAL sample, the test line will also appear within 15min of sample application. Because the intensity of the test line is proportional to the amount of Aspergillus antigen present in the sample, the test line can appear as a weak positive (+), a moderate positive (++) or as a strong positive (+++). However, any positive test line, regardless of intensity, would indicate the presence of Aspergillus antigen in the sample. In the absence of Aspergillus antigen, no test line will appear, and the result is recorded as negative (-).</li>
</ol>
4. Representative Results
Representative examples of negative, weak positive, moderate positive, and strong positive LFD results with BAL and serum samples are shown in Figure 1.
Results of antigen-positive LFD tests (weak and strong) or negative LFD tests using BAL fluids from acute myeloid leukemia (AML) patients diagnosed according to EORTC/MSG diagnostic criteria are shown in Table 1. Included in this table are the corresponding clinical and mycological (galactomannan and culture) data, and results of an Aspergillus-specific PCR test developed at St. Bartholomews Hospital8, for each patient. Diagnosis of disease was based on host factors (neutropenia, prolonged use of corticosteroids, treatment with other recognized T-cell immunosuppressants), clinical criteria and GM positivity for BAL (here defined as a GM index value &gt; 0.8). Under the 2002 EORTC/MSG guidelines10, patients 12, 13 and 16 were diagnosed with 'possible' IA on the basis of host factors and clinical criteria or GM positivity. According to the revised (2008) EORTC/MSG guidelines2, host factors and GM positivity alone or host factors and clinical criteria alone would not indicate 'possible' invasive fungal infection unless accompanied by supporting evidence from clinical data and mycology respectively. Patient 6 was diagnosed with 'probable' IA under both 2002 and 2008 guidelines because of host factors, major and minor clinical features and GM positivity. Note, that while neither the LFD nor PCR assays are currently included in EORTC/MSG guidelines, there is strong agreement between the two assays and the commercial galactomannan test indicating the presence of Aspergillus antigen and nucleic acid in the BAL samples of patients 6 and 12. Additional results of trials demonstrating the efficacy of the LFD and PCR assays in diagnosing IPA can be found in Johnson et al8.
<img alt="Figure 1" src="/files/ftp_upload/3721/3721fig1.jpg" /> 
Figure 1. Negative (control line only) and positive (control and test line) results of LFD tests using serum and BAL. The intensities of the test line reactions are proportional to the concentrations of the target antigen in the serum and BAL samples. Reactions typically range from weak (+) through moderate (++) to strong (+++). Regardless of test line intensity, all three serum positive reactions would indicate invasive pulmonary aspergillosis disease due to the presence of circulating Aspergillus antigen in the bloodstream. Positive BAL reactions (weak, moderate or strong) would indicate germination of spores and development of potentially pathogenic hyphae in the lungs.
<table border="1">
	<tbody>
		<tr>
			<td>Patient no.</td>
			<td>Patient information</td>
			<td>Clinical criteria1</td>
			<td>BAL culture2</td>
			<td>GM EIA index3</td>
			<td>EORTC / MSG (2002)4</td>
			<td>EORTC / MSG (2008)5</td>
			<td>Aspergillus PCR result</td>
			<td>LFD result</td>
		</tr>
		<tr>
			<td>6</td>
			<td>-</td>
			<td>Major CT signs (nodule and halo) and one minor</td>
			<td>Negative</td>
			<td>0.9 (positive)</td>
			<td>Probable</td>
			<td>Probable</td>
			<td>Positive</td>
			<td>Weak positive (+)</td>
		</tr>
		<tr>
			<td>12</td>
			<td>Presumed previous fungal infection</td>
			<td>No major, one minor</td>
			<td>Candida glabrata</td>
			<td>6.43 (strong positive)</td>
			<td>Possible</td>
			<td>None</td>
			<td>Positive</td>
			<td>Strong positive (+++)</td>
		</tr>
		<tr>
			<td>13</td>
			<td>Coagulase-negative Staphylococcus and E. coli in blood</td>
			<td>No major, two minor</td>
			<td>Negative</td>
			<td>0.25 (negative)</td>
			<td>Possible</td>
			<td>None</td>
			<td>Negative</td>
			<td>Negative (-)</td>
		</tr>
		<tr>
			<td>16</td>
			<td>Chest infection</td>
			<td>3 minor criteria including new infiltrate plus plural effusion</td>
			<td>Negative</td>
			<td>0.16 (negative)</td>
			<td>Possible</td>
			<td>None</td>
			<td>Negative</td>
			<td>Negative (-)</td>
		</tr>
	</tbody>
</table>
1 Nodules or halos on a computed tomography scan is suggestive of fungal infection 
2 Candida glabrata in BAL fluid would be regarded as a contaminant as it is the second most common yeast isolated as part of normal human flora9 
3 An index of &gt;0.8 in the GM EIA test of BAL is indicative of Aspergillus infection 
4 Based on the 2002 EORTC/MSG diagnostic criteria for 'possible', 'probable' or 'proven' invasive fungal disease10 
 5 Based on the revised (2008) EORTC/MSG diagnostic criteria for 'possible', 'probable' or 'proven' invasive fungal disease2
Table 1. Results of LFD tests of BAL samples from acute myeloid leukemia patients with probable IPA and from control AML patients (no evidence of infection), and EORTC/MSG diagnosis of infection.

<ol>
	<li>Thornton, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+invasive+aspergillosis.">Detection of invasive aspergillosis.</a> Adv. Appl. Microbiol. 70, 187-216 (2010).</li><li>De Pauw, B., Walsh, T. J., Donnelly, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Revised+definitions+of+invasive+fungal+disease+from+the+European+Organization+for+Research+and+Treatment+of+Cancer/Invasive+Fungal+Infections+Cooperative+Group+and+the+National+Institute+of+Allergy+and+Infectious+Diseases+Mycology+Study+Group+(EORTC/MSG)+concensus+group.">Revised definitions of invasive fungal disease from the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycology Study Group (EORTC/MSG) concensus group.</a> Clin. Infect. Dis. 46, 1813-1821 (2008).</li><li>Thornton, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tracking+the+emerging+human+pathogen+Pseudallescheria+boydii+by+using+highly+specific+monoclonal+antibodies.">Tracking the emerging human pathogen Pseudallescheria boydii by using highly specific monoclonal antibodies.</a> Clin. Vacc. Immunol. 16, 756-764 (2009).</li><li>Pickering, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+a+(1+->+3)-&#946;-D-glucan+assay+for+diagnosis+of+invasive+fungal+infections.">Evaluation of a (1 -> 3)-&#946;-D-glucan assay for diagnosis of invasive fungal infections.</a> J. Clin. Microbiol. 43, 5957-5962 (2005).</li><li>Thornton, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+an+immunochromatographic+lateral-flow+device+for+rapid+serodiagnosis+of+invasive+aspergillosis.">Development of an immunochromatographic lateral-flow device for rapid serodiagnosis of invasive aspergillosis.</a> Clin. Vacc. Immunol. 15, 1095-1105 (2008).</li><li>Verweij, P. E., Mennink-Kersten, M. A. S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Issues+with+galactomannan+testing.">Issues with galactomannan testing.</a> Med. Mycol. 44, 179-183 (2006).</li><li>Wiederhold, N. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+lateral+flow+technology+and+galactomannan+and+(1+->+3)-&#946;-D-glucan+assays+for+detection+of+invasive+pulmonary+aspergillosis.">Comparison of lateral flow technology and galactomannan and (1 -> 3)-&#946;-D-glucan assays for detection of invasive pulmonary aspergillosis.</a> Clin. Vacc. Immunol. 16, 1844-1846 (2009).</li><li>Johnson, G. L., Bibby, D., Bustin, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+Aspergillus+in+broncho-alveolar+lavage+fluid+using+two+biological+assays;+evidence+of+active+infection.">Detection of Aspergillus in broncho-alveolar lavage fluid using two biological assays; evidence of active infection.</a> Mycoses. 54, 130-131 (2011).</li><li>Malani, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Candida+glabrata+fungemia:+experience+in+a+tertiary+care+centre.">Candida glabrata fungemia: experience in a tertiary care centre.</a> Clin. Infect. Dis. 41, 975-981 (2005).</li><li>Ascioglu, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Defining+opportunistic+invasive+fungal+infection+in+immunocompromised+patients+with+cancer+and+hematopoietic+stem+cell+transplants:+an+international+concensus.">Defining opportunistic invasive fungal infection in immunocompromised patients with cancer and hematopoietic stem cell transplants: an international concensus.</a> Clin. Infect. Dis. 34, 71-74 (2002).</li><li>Denning, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early+diagnosis+of+invasive+aspergillosis.">Early diagnosis of invasive aspergillosis.</a> Lancet. 355, 423-424 (2000).</li><li>Greene, R., Shibuya, K., Ando, T., Latge, J. -. P., Steinbach, W. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Aspergillus fumigatus and Aspergillosis. , 353-363 (2009).</li><li>Klont, R. R., Mennink-Kersten, M. A. S. H., Verweij, P. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Utility+of+Aspergillus+antigen+detection+in+specimens+other+than+serum+samples.">Utility of Aspergillus antigen detection in specimens other than serum samples.</a> Clin. Infect. Dis. 39, 1467-1474 (2004).</li><li>Iweala, O. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HIV+diagnostic+tests:+an+overview.">HIV diagnostic tests: an overview.</a> Contraception. 70, 141-147 (2004).</li><li>Ketema, F., Zeh, C., Edelman, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+the+performance+of+a+rapid,+lateral+flow+assay+for+the+detection+of+antibodies+to+HIV.">Assessment of the performance of a rapid, lateral flow assay for the detection of antibodies to HIV.</a> J. Acquir. Immune Defic. Syndr. 27, 63-70 (2001).</li><li>Moody, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+diagnostic+tests+for+malaria+parasites.">Rapid diagnostic tests for malaria parasites.</a> Clin. Microbiol. Rev. 15, 66-78 (2002).</li><li>Parkash, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performance+of+a+lateral+flow+test+for+the+detection+of+leprosy+patients+in+India.">Performance of a lateral flow test for the detection of leprosy patients in India.</a> J. Med. Microbiol. 57, 130-132 (2008).</li><li>Sharma, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+lateral-flow+Clostridium+botulinum+neurotoxin+detection+kits+for+food+analysis.">Evaluation of lateral-flow Clostridium botulinum neurotoxin detection kits for food analysis.</a> Appl. Environ. Microbiol. 71, 3935-3941 (2005).</li><li>Smits, H. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lateral-flow+assay+for+rapid+serodiagnosis+of+human+leptospirosis.">Lateral-flow assay for rapid serodiagnosis of human leptospirosis.</a> Clin. Diagn. Lab. Immunol. 8, 166-169 (2001).</li><li>Faulstich, K., Wong, R., Tse, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Lateral Flow Immunoassay. , 157-185 (2009).</li></ol>

We have nothing to disclose.

Definitive identification of IPA can only truly be achieved by isolation of the etiologic agent from biopsy samples, but recovery of suitable samples is often not possible in very sick patients and Aspergillus is rarely recoverable from blood. While major advances have been made in the use of computed tomographic scanning of the chest in IPA diagnosis, characteristics that are suggestive of pulmonary IPA such as the "halo" or "air-crescent" signs are either transient or can be attributed to breathing artifacts or other fungal infections11,12. Such data are therefore supplemented with serological techniques that aim to identify signature molecules (GM and &beta;-glucan) from fungi that are circulating in the patient's serum or that are present in BAL fluids, sputum or urine samples13. While these tests display satisfactory sensitivity, they lack sufficient specificity or suffer from interference under certain conditions1,6.
The LFD test for IPA detection presented here enables the 'point-of-care' diagnosis of IPA and exploits technology that has been used to date in tests for the detection of viruses, bacteria, parasites and toxins14-19 and, most famously, for the home pregnancy tests first introduced by Unipath in 1988. In the Aspergillus LFD described here, the Aspergillus-specific MAb JF5 is immobilized to a capture zone (the test line) on a porous nitrocellulose membrane. Anti-mouse immunoglobulin immobilized to the membrane in a separate zone served as an internal control (control line). On addition of serum or BAL fluid to the release port, MAb JF5-colloidal gold conjugate in the release pad binds to the target antigen and the complex then passes along the porous membrane by capillary action. MAb JF5 immobilized in the capture zone binds to the JF5-colloidal gold-antigen complex resulting in a red test line. Any unbound JF5-colloidal gold conjugate binds to the internal control indicating that the assay has run correctly. This results in a red control line.
The test is quick, taking only 15 minutes to perform, is cheap compared to serum and BAL tests based on GM and &beta;-glucan detection, and does not require expensive equipment or extensive laboratory facilities to run. Furthermore, MAb JF5 does not cross-react with the drugs or contaminants that have been shown to cause false-positive reaction in the GM and &beta;-glucan tests1,4,6. An additional major advantage over current diagnostic tests is the LFDs ability to detect activity that is indicative of invasive growth of Aspergillus species.
A critical step in the LFD procedure is the need to read the results 15 min after application of the serum or BAL sample to the device. The test should not be left for longer than 15 min before recording the results, as this may bias result interpretation. A weak reaction will not be enhanced by extending the incubation period. Heat treatment of serum from animal models of infection has been found to improve assay sensitivity. A limitation of the test is that it is qualitative, and relies on the operator to make a subjective assessment of positivity. The intensity of the test line varies according to the antigen contents of serum and BAL samples (Figure 1). However, any positive reaction (determined by comparison to known negatives) indicates the presence of Aspergillus antigen and therefore infection. To limit the subjectivity of LFD assays, hand-held devices are available which allow quantification of LFD test line intensities and enable the establishment of threshold values for antigen detection20.
Future developments of the LFD include its commercialization and the development of a multiplex LFD that allows simultaneous detection of other invasive fungal pathogens using highly specific MAbs3.

<table border="1">
 <tbody>
 <tr>
 <td>Name of the reagent</td>
 <td>Company</td>
 <td>Catalogue number</td>
 <td>Comments </td>
 </tr>
 <tr>
 <td>Aspergillus LFD</td>
 <td>University of Exeter</td>
 <td>&nbsp;</td>
 <td>Available from the corresponding author on request</td>
 </tr>
 <tr>
 <td>RPMI-1640</td>
 <td>Sigma</td>
 <td>R0883</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>L-Glutamine</td>
 <td>Sigma</td>
 <td>G7513</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Fetal calf serum</td>
 <td>Biosera</td>
 <td>S9100</td>
 <td>Other sources of fetal calf serum can be used in the preparation of TCM</td>
 </tr>
 <tr>
 <td>EDTA</td>
 <td>Fisher Scientific</td>
 <td>BPE120-1</td>
 <td>&nbsp;</td>
 </tr>
 </tbody>
</table>

detection of invasive pulmonary aspergillosis in haematological malignancy patients by using lateral-flow technology

Invasive pulmonary aspergillosis (IPA) is a leading cause of morbidity and mortality in haematological malignancy patients and hematopoietic stem cell transplant recipients1. Detection of IPA represents a formidable diagnostic challenge and, in the absence of a 'gold standard', relies on a combination of clinical data and microbiology and histopathology where feasible. Diagnosis of IPA must conform to the European Organization for Research and Treatment of Cancer and the National Institute of Allergy and Infectious Diseases Mycology Study Group (EORTC/MSG) consensus defining "proven", "probable", and "possible" invasive fungal diseases2. Currently, no nucleic acid-based tests have been externally validated for IPA detection and so polymerase chain reaction (PCR) is not included in current EORTC/MSG diagnostic criteria.
Identification of Aspergillus in histological sections is problematic because of similarities in hyphal morphologies with other invasive fungal pathogens3, and proven identification requires isolation of the etiologic agent in pure culture. Culture-based approaches rely on the availability of biopsy samples, but these are not always accessible in sick patients, and do not always yield viable propagules for culture when obtained.
An important feature in the pathogenesis of Aspergillus is angio-invasion, a trait that provides opportunities to track the fungus immunologically using tests that detect characteristic antigenic signatures molecules in serum and bronchoalveolar lavage (BAL) fluids. This has led to the development of the Platelia enzyme immunoassay (GM-EIA) that detects Aspergillus galactomannan and a 'pan-fungal' assay (Fungitell test) that detects the conserved fungal cell wall component (1 &rarr;3)-&beta;-D-glucan, but not in the mucorales that lack this component in their cell walls1,4. Issues surrounding the accuracy of these tests1,4-6 has led to the recent development of next-generation monoclonal antibody (MAb)-based assays that detect surrogate markers of infection1,5.
Thornton5 recently described the generation of an Aspergillus-specific MAb (JF5) using hybridoma technology and its use to develop an immuno-chromatographic lateral-flow device (LFD) for the point-of-care (POC) diagnosis of IPA. A major advantage of the LFD is its ability to detect activity since MAb JF5 binds to an extracellular glycoprotein antigen that is secreted during active growth of the fungus only5. This is an important consideration when using fluids such as lung BAL for diagnosing IPA since Aspergillus spores are a common component of inhaled air. The utility of the device in diagnosing IPA has been demonstrated using an animal model of infection, where the LFD displayed improved sensitivity and specificity compared to the Platelia GM and Fungitell (1 &rarr; 3)-&beta;-D-glucan assays7.
Here, we present a simple LFD procedure to detect Aspergillus antigen in human serum and BAL fluids. Its speed and accuracy provides a novel adjunct point-of-care test for diagnosis of IPA in haematological malignancy patients.

Watch this Scientific Journal Video about Detection of Invasive Pulmonary Aspergillosis in Haematological Malignancy Patients by using Lateral-flow Technology at JoVE.com

Detection of Invasive Pulmonary Aspergillosis in Haematological Malignancy Patients by using Lateral-flow Technology

A rapid and accurate point-of-care test for invasive pulmonary aspergillosis is presented. It takes advantage of lateral-flow technology using a specific monoclonal antibody that binds to an Aspergillus antigen secreted during pulmonary infections. The assay is compatible with serum and brochoalveolar lavage and represents a novel adjunct test for disease diagnosis.

Invasive pulmonary aspergillosis (IPA) is a leading cause of morbidity and mortality in haematological malignancy patients and hematopoietic stem cell ...

detection-invasive-pulmonary-aspergillosis-haematological-malignancy

Research

JoVE Journal

Immunology and Infection

Non-invasive Imaging of Leukocyte Homing and Migration in vivo

Two-photon (2P) microscopy is a high resolution imaging technique that has been broadly adapted by biologists. The value of 2P microscopy is that it provides rich spatiotemporal information regarding cell behaviors within intact tissues and in live mice. Leukocyte recruitment plays a significant role in host defense against infection and when unchecked, can contribute to inflammatory and autoimmune diseases. Studying leukocyte recruitment in vivo is technically challenging since cells are moving rapidly within vessels located deep within light scattering tissues. To date, most intravital imaging studies require surgical preparation to expose the blood vessels and tissues. To avoid the tissue damage and inflammation induced by surgery itself, here, we describe a non-invasive single-cell imaging approach that can be used to study leukocyte trafficking in the mouse footpad and phalanges. We discuss the technical aspects of our 2P imaging preparation and walk the reader through a typical experiment from initial set up to execution and data collection.

Non-invasive Imaging of Leukocyte Homing and Migration in vivo

Here, we describe a non-invasive two-photon (2P) microscopy approach to study leukocyte homing in the mouse footpad. We discuss the technical aspects of our tissue imaging preparation and walk the reader through a typical experiment from initial set up to execution and data collection.

Two-photon (2P) microscopy is a high resolution imaging technique that has been broadly adapted by biologists.  The value of 2P microscopy is that it ...

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 ...

IgY Technology: Extraction of Chicken Antibodies from Egg Yolk by Polyethylene Glycol (PEG) Precipitation

Hens can be immunized by means of i.m. vaccination (Musculus pectoralis, left and right, injection volume 0.5-1.0 ml) or by means of Gene-Gun plasmid-immunization. Dependent on the immunogenicity of the antigen, high antibody-titres (up to 1:100,000 - 1:1,000,000) can be achieved after only one or 3 - 4 boost immunizations. Normally, a hen lays eggs continuously for about 72 weeks, thereafter the laying capacity decreases. This protocol describes the extraction of total IgY from egg yolk by means of a precipitation procedure (PEG. Polson et al. 1980). The method involves two important steps. The first one is the removal of lipids and the second is the precipitation of total IgY from the supernatant of step one. After dialysis against a buffer (normally PBS) the IgY-extract can be stored at -20&deg;C for more than a year. The purity of the extract is around 80 %, the total IgY per egg varies from 40-80 mg, dependent on the age of the laying hen. The total IgY content increases with the age of the hen from around 40 mg/egg up to 80 mg/egg (concerning PEG precipitation). The laying capacity of a hen per year is around 325 eggs. That means a total potential harvest of 20 g total IgY/year based on a mean IgY content of 60 mg total IgY/egg (see Table 1).

IgY Technology: Extraction of Chicken Antibodies from Egg Yolk by Polyethylene Glycol PEG Precipitation

This protocol describes in particular the extraction of total IgY from egg yolk by means of polyethylene glycol precipitation and gives general information about IgY technology.

Hens can be immunized by means of  i.m. vaccination (Musculus pectoralis, left and right, injection volume  0.5-1.0 ml) or by means of Gene-Gun ...

Detection of Bacteria Using Fluorogenic DNAzymes

Outbreaks linked to food-borne and hospital-acquired pathogens account for millions of deaths and hospitalizations as well as colossal economic losses each and every year. Prevention of such outbreaks and minimization of the impact of an ongoing epidemic place an ever-increasing demand for analytical methods that can accurately identify culprit pathogens at the earliest stage. Although there is a large array of effective methods for pathogen detection, none of them can satisfy all the following five premier requirements embodied for an ideal detection method: high specificity (detecting only the bacterium of interest), high sensitivity (capable of detecting as low as a single live bacterial cell), short time-to-results (minutes to hours), great operational simplicity (no need for lengthy sampling procedures and the use of specialized equipment), and cost effectiveness. For example, classical microbiological methods are highly specific but require a long time (days to weeks) to acquire a definitive result.1 PCR- and antibody-based techniques offer shorter waiting times (hours to days), but they require the use of expensive reagents and/or sophisticated equipment.2-4 Consequently, there is still a great demand for scientific research towards developing innovative bacterial detection methods that offer improved characteristics in one or more of the aforementioned requirements. Our laboratory is interested in examining the potential of DNAzymes as a novel class of molecular probes for biosensing applications including bacterial detection.5
DNAzymes (also known as deoxyribozymes or DNA enzymes) are man-made single-stranded DNA molecules with the capability of catalyzing chemical reactions.6-8 These molecules can be isolated from a vast random-sequence DNA pool (which contains as many as 1016 individual sequences) by a process known as "in vitro selection" or "SELEX" (systematic evolution of ligands by exponential enrichment).9-16 These special DNA molecules have been widely examined in recent years as molecular tools for biosensing applications.6-8
Our laboratory has established in vitro selection procedures for isolating RNA-cleaving fluorescent DNAzymes (RFDs; Fig. 1) and investigated the use of RFDs as analytical tools.17-29 RFDs catalyze the cleavage of a DNA-RNA chimeric substrate at a single ribonucleotide junction (R) that is flanked by a fluorophore (F) and a quencher (Q). The close proximity of F and Q renders the uncleaved substrate minimal fluorescence. However, the cleavage event leads to the separation of F and Q, which is accompanied by significant increase of fluorescence intensity.
More recently, we developed a method of isolating RFDs for bacterial detection.5 These special RFDs were isolated to "light up" in the presence of the crude extracellular mixture (CEM) left behind by a specific type of bacteria in their environment or in the media they are cultured (Fig. 1). The use of crude mixture circumvents the tedious process of purifying and identifying a suitable target from the microbe of interest for biosensor development (which could take months or years to complete). The use of extracellular targets means the assaying procedure is simple because there is no need for steps to obtain intracellular targets.
Using the above approach, we derived an RFD that cleaves its substrate (FS1; Fig. 2A) only in the presence of the CEM produced by E. coli (CEM-EC).5 This E. coli-sensing RFD, named RFD-EC1 (Fig. 2A), was found to be strictly responsive to CEM-EC but nonresponsive to CEMs from a host of other bacteria (Fig. 3).
Here we present the key experimental procedures for setting up E. coli detection assays using RFD-EC1 and representative results.

We have recently reported a novel approach for generating fluorogenic DNAzyme probes that can be applied to set up a simple, "mix-and-read" fluorescent assay for bacterial detection. These special DNA probes catalyze the cleavage of a chromophore-modified DNA-RNA chimeric substrate in the presence of crude extracellular mixture (CEM) produced by a specific bacterium, thereby translating bacterial detection into fluorescence signal generation. In this report we will describe key experimental procedures where a specific DNAzyme probe denoted "RFD-EC1" is employed for the detection of the model bacterium, Escherichia coli (E. coli).

Outbreaks linked to food-borne and hospital-acquired pathogens account for millions of deaths and hospitalizations as well as colossal economic losses ...

In Vivo Imaging Systems (IVIS) Detection of a Neuro-Invasive Encephalitic Virus

Modern advancements in imaging technology encourage further development and refinement in the way viral research is accomplished. Initially proposed by Russel and Burch in Hume's 3Rs (replacement, reduction, refinement), the utilization of animal models in scientific research is under constant pressure to identify new methodologies to reduce animal usage while improving scientific accuracy and speed. A major challenge to Hume's principals however, is how to ensure the studies are statistically accurate while reducing animal disease morbidity and overall numbers. Vaccine efficacy studies currently require a large number of animals in order to be considered statistically significant and often result in high morbidity and mortality endpoints for identification of immune protection. We utilized in vivo imaging systems (IVIS) in conjunction with a firefly bioluminescent enzyme to progressively track the invasion of the central nervous system (CNS) by an encephalitic virus in a murine model. Typically, the disease progresses relatively slowly, however virus replication is rapid, especially within the CNS, and can lead to an often, lethal outcome. Following intranasal infection of the mice with TC83-Luc, an attenuated Venezuelan equine encephalitis virus strain modified to expresses a luciferase gene; we are able to visualize virus replication within the brain at least three days before the development of clinical disease symptoms. Utilizing CNS invasion as a key encephalitic disease development endpoint we are able to quickly identify therapeutic and vaccine protection against TC83-Luc infection before clinical symptoms develop. With IVIS technology we are able to demonstrate the rapid and accurate testing of drug therapeutics and vaccines while reducing animal numbers and morbidity.

In Vivo Imaging Systems IVIS Detection of a Neuro-Invasive Encephalitic Virus

Utilizing luciferase and in vivo imaging systems (IVIS) as a novel means to identify disease endpoints before clinical developments occur. IVIS has allowed us to visualize in real time the invasion of encephalitic viruses over multiple days, providing a more accurate disease model for future study. It has also allowed us to identify the potential protective features of antivirals and vaccines faster than currently utilized animal models. The capability to utilize individual animals over multiple time points ensures reduced animal requirements, costs, and overall morbidity to the animals utilized ensuring a more humane and more scientific means of disease study.

Modern advancements in imaging technology encourage further development and refinement in the way viral research is accomplished. Initially proposed by ...

Detection of Human Leukocyte Antigen Biomarkers in Breast Cancer Utilizing Label-free Biosensor Technology

According to the American Cancer Society, more than 200,000 women will be diagnosed with invasive breast cancer each year and approximately 40,000 will die from the disease. The human leukocyte antigen (HLA) class I samples peptides derived from proteasomal degradation of cellular proteins and presents these fragments on the cell surface for interrogation by circulating cytotoxic T lymphocytes (CTL). Generation of T-cell receptor mimic (TCRm) monoclonal antibodies (mAbs) which recognize breast cancer specific peptide/HLA-A*02:01 complexes such as those derived from macrophage migration inhibitory factor (MIF19-27) and NY-ESO-1157-165 enable detection and destruction of breast cancer cells in the absence of an effective anti-tumor CTL response. Intact class I HLA/peptide complexes are shed by breast cancer cells and represent potentially relevant cancer biomarkers. In this work, a breakthrough biomarker screening system for cancer diagnostics incorporating T-cell receptor mimic monoclonal antibodies combined with a novel, label-free biosensor utilizing guided-mode resonance (GMR) sensor technology is presented. Detection of shed MIF/HLA-A*02:01 complexes in MDA-MB-231 cell supernatants, spiked human serum, and patient plasma is demonstrated. The impact of this work could revolutionize personalized medicine through development of companion disease diagnostics for targeted immunotherapies.

Intact class I HLA/peptide complexes are shed by cancer cells, representing a potential relevant cancer biomarker. Utilizing label-free sensor technology and T-cell receptor mimicking monoclonal antibodies, detection of shed MIF/HLA-A*02:01 complexes in MDA-MB-231 cell supernatants, spiked human serum, and patient plasma is demonstrated, enabling development of a novel cancer diagnostic platform.

According to the American Cancer Society, more than 200,000 women will be diagnosed with invasive breast cancer each year and approximately 40,000 will ...

High-throughput Detection of Respiratory Pathogens in Animal Specimens by Nanoscale PCR

Nanoliter scale real-time PCR uses spatial multiplexing to allow multiple assays to be run in parallel on a single plate without the typical drawbacks of combining reactions together. We designed and evaluated a panel based on this principle to rapidly identify the presence of common disease agents in dogs and horses with acute respiratory illness. This manuscript describes a nanoscale diagnostic PCR workflow for sample preparation, amplification, and analysis of target pathogen sequences, focusing on procedures that are different from microliter scale reactions. In the respiratory panel presented, 18 assays were each set up in triplicate, accommodating up to 48 samples per plate. A universal extraction and pre-amplification workflow was optimized for high-throughput sample preparation to accommodate multiple matrices and DNA and RNA based pathogens. Representative data are presented for one RNA target (influenza A matrix) and one DNA target (equine herpesvirus 1). The ability to quickly and accurately test for a comprehensive, syndrome-based group of pathogens is a valuable tool for improving efficiency and ergonomics of diagnostic testing and for acute respiratory disease diagnosis and management.

High-throughput testing of DNA and RNA based pathogens by nanoscale PCR is described using a syndromic canine and equine respiratory PCR panel.

Nanoliter scale real-time PCR uses spatial multiplexing to allow multiple assays to be run in parallel on a single plate without the typical drawbacks of ...

Generation of Murine Monoclonal Antibodies by Hybridoma Technology

Monoclonal antibodies are universal binding molecules and are widely used in biomedicine and research. Nevertheless, the generation of these binding molecules is time-consuming and laborious due to the complicated handling and lack of alternatives. The aim of this protocol is to provide one standard method for the generation of monoclonal antibodies using hybridoma technology. This technology combines two steps. Step 1 is an appropriate immunization of the animal and step 2 is the fusion of B lymphocytes with immortal myeloma cells in order to generate hybrids possessing both parental functions, such as the production of antibody molecules and immortality. The generated hybridoma cells were then recloned and diluted to obtain stable monoclonal cell cultures secreting the desired monoclonal antibody in the culture supernatant. The supernatants were tested in enzyme-linked immunosorbent assays (ELISA) for antigen specificity. After the selection of appropriate cell clones, the cells were transferred to mass cultivation in order to produce the desired antibody molecule in large amounts. The purification of the antibodies is routinely performed by affinity chromatography. After purification, the antibody molecule can be characterized and validated for the final test application. The whole process takes 8 to 12 months of development, and there is a high risk that the antibody will not work in the desired test system.

An optimized protocol is presented for the generation of monoclonal antibodies based on the hybridoma technology. Mice were immunized with an immunoconjugate. Spleen cells were fused by PEG and an electric impulse with immortal myeloma cells. Antibody-producing hybridoma cells were selected by HAT and antigen-specific ELISA screening.

Monoclonal antibodies are universal binding molecules and are widely used in biomedicine and research. Nevertheless, the generation of these binding ...

Detection of Enterohemorrhagic Escherichia Coli Colonization in Murine Host by Non-invasive In Vivo Bioluminescence System

Enterohemorrhagic E. coli (EHEC) O157:H7, which is a foodborne pathogen that causesdiarrhea, hemorrhagic colitis (HS), and hemolytic uremic syndrome (HUS), colonize to the intestinal tract of humans. To study the detailed mechanism of EHEC colonization in vivo, it is essential to have animal models to monitor and quantify EHEC colonization. We demonstrate here a mouse-EHEC colonization model by transforming the bioluminescent expressing plasmid to EHEC to monitor and quantify EHEC colonization in living hosts. Animals inoculated with bioluminescence-labeled EHEC show intense bioluminescent signals in mice by detection with a non-invasive in vivo imaging system. After 1 and 2 days post infection, bioluminescent signals could still be detected in infected animals, which suggests that EHEC colonize in hosts for at least 2 days. We also demonstrate that these bioluminescent EHEC locate to mouse intestine, specifically in the cecum and colon, from ex vivo images. This mouse-EHEC colonization model may serve as a tool to advance the current knowledge of the EHEC colonization mechanism.

Detection of Enterohemorrhagic Escherichia Coli Colonization in Murine Host by Non-invasive In Vivo Bioluminescence System

A detailed protocol of a mouse model for enterohemorrhagic E. coli (EHEC) colonization by using bioluminescence-labeled bacteria is presented. The detection of these bioluminescent bacteria by a non-invasive in vivo imaging system in live animals can advance our current understanding of EHEC colonization.

Enterohemorrhagic E. coli (EHEC) O157:H7, which is a foodborne pathogen that causesdiarrhea, hemorrhagic colitis (HS), and hemolytic uremic syndrome ...

Histological Quantification to Determine Lung Fungal Burden in Experimental Aspergillosis

The quantification of lung fungal burden is critical for the determination of the relative levels of immune protection and fungal virulence in mouse models of pulmonary fungal infection. Although multiple methods are used to assess fungal burden, quantitative polymerase chain reaction (qPCR) of fungal DNA has emerged as a technique with several advantages over previous culture-based methods. Currently, a comprehensive assessment of lung pathology, leukocyte recruitment, fungal burden, and gene expression in mice with invasive aspergillosis (IA) necessitates the use of a significant number of experimental and control animals. Here the quantification of lung histological staining to determine fungal burden using a reduced number of animals was examined in detail. Lung sections were stained to identify fungal structures with Gomori&#39;s modified methanamine silver (GMS) staining. Images were taken from the GMS-stained sections from 4 discrete fields of each formalin-fixed paraffin-embedded lung. The GMS stained areas within each image were quantified using an image analysis program, and from this quantification, the mean percentage of stained area was determined for each sample. Using this strategy, eosinophil-deficient mice exhibited decreased fungal burden and disease with caspofungin therapy, while wild-type mice with IA did not improve with caspofungin. Similarly, fungal burden in mice lacking &#947;&#948; T cells were also improved by caspofungin, as measured by qPCR and GMS quantification. GMS quantification is therefore introduced as a method for the determination of relative lung fungal burden that may ultimately reduce the quantity of experimental animals required for comprehensive studies of invasive aspergillosis.

Here we describe a protocol to determine pulmonary fungal burden in mice with invasive aspergillosis by quantification of Gomori&#39;s modified methanamine silver staining in histological sections. Use of this method resulted in comparable results with less animals compared to assessment of fungal burden by quantitative PCR of lung fungal DNA.

The quantification of lung fungal burden is critical for the determination of the relative levels of immune protection and fungal virulence in mouse ...