Name: expression of exogenous antigens in the mycobacterium bovis bcg vaccine via non-genetic surface decoration with the avidin-biotin system
Uploaded: 2018-01-31T13:00:00
Description: Watch this Scientific Journal Video about Expression of Exogenous Antigens in the Mycobacterium bovis BCG Vaccine via Non-genetic Surface Decoration with the Avidin-biotin System at JoVE.com

We thank Dr. R Stokes for the BCG Pasteur strain and A. Talal for technical support. We also thank GenScript for help with gene synthesis.

All animals were maintained in accordance with protocols approved by the Animal Care and Use Committees at the University of British Columbia. Experiments were approved by the Animal Care and Use Committees and performed according to the Canadian Council on Animal Care Guidelines. The animal assurance welfare number is A11-0247.
1. Generation of Monomeric Avidin Fusion Proteins Expressing Plasmids
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We reported in this study a non-genetic approach for rapid and effective display of exogenous proteins on BCG surface to add either specific antigens or specific functional properties expected to efficiently improve the bacterium&#39;s immunogenicity. We demonstrated that the BCG cell surface could be easily biotinylated for instantaneous surface decoration with avidin fusion proteins. The total procedure can be performed within 2 h, while genetic transformation and selection of positive clones requires 2 to 3 months of ...

Various strategies have been proposed to replace the current TB vaccine BCG, including protein adjuvant systems, viral vectored technologies, attenuated live M.tb strains, and genetically modified BCG strains, either to introduce genes over-expressing BCG antigens that are not sufficiently expressed during infection1 or Mtb-specific antigens not present in BCG2. Genetic engineering, however, faces many barriers including the uncertain level of safety, the time-consuming process, and the low efficiency of expression vectors4,5. With regards to improving BCG, an alternate approach is needed to improve immunogenicity without the need for uncertain genetic alternations.
In this study, we introduce a novel strategy for display of recombinant proteins of interest on the BCG cell surface that is based on the well-known high-affinity avidin interaction with biotin. This approach allows rapid and reproducible attachment of recombinant avidin fusion proteins on the surface of biotinylated BCG, which facilitates broad manipulations of BCG to achieve maximal improvement of its efficacy while maintaining its excellent safety record, observed over decades of use.
Avidin affinity for biotin is extremely high (Kd = 10&#8722;15 M) and once formed, the biotin-avidin complex is very stable and can only be disrupted under denaturing conditions6. However, for this type of interaction to serve as a gene transfer method alternative, long-term but reversible display of recombinant proteins is required. Thus, we introduced here a low affinity monomeric avidin (Kd = 10&#8722;7 M) that leads to the reversible release of protein from the surface decorated BCG once ingested inside antigen presenting cells. In order to provide a proof of concept, we tested this method using a monomeric avidin chimeric protein corresponding to a surrogate antigen derived from ovalbumin (OVA)7,8. The results showed that the BCG cell surface can be easily and rapidly decorated with monomeric avidin fusion proteins and that this binding to the BCG surface is stable and reproducible without detectable changes in bacterial growth and survival. Also, we found that BCG decorated with monomeric avidin fused with OVA (AviOVA) can induce an immune response similar to that induced by BCG genetically expressing the same antigen both in vitro and in vivo. This technology of reversible display of proteins of interest on the bacterial surface is therefore an effective replacement of traditional gene transfer approaches and can provide a platform for broad manipulations of BCG and further applications in vaccine development.

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			<td height="21" style="height:21px;">Wheaton boroscilicate glass vials</td>
			<td>Wheaton</td>
			<td style="width:119px;">&#160;VWR 66011-675</td>
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expression of exogenous antigens in the mycobacterium bovis bcg vaccine via non-genetic surface decoration with the avidin-biotin system

Tuberculosis (TB) is a serious infectious disease and the only available vaccine M. bovis bacillus Calmette-Gu&#233;rin (BCG) is safe and effective for protection against children&#39;s severe TB meningitis and some forms of disseminated TB, but fails to protect against pulmonary TB, which is the most prevalent form of the disease. Promising strategies to improve BCG currently rely either on its transformation with genes encoding immunodominant M. tuberculosis (Mtb)-specific antigens and/or complementation with genes encoding co-factors that would stimulate antigen presenting cells. Major limitations to these approaches include low efficiency, low stability, and the uncertain level of safety of expression vectors. In this study, we present an alternative approach to vaccine improvement, which consists of BCG complementation with exogenous proteins of interest on the surface of bacteria, rather than transformation with plasmids encoding corresponding genes. First, proteins of interest are expressed in fusion with monomeric avidin in standard E. coli expression systems and then used to decorate the surface of biotinylated BCG. Animal experiments using BCG surface decorated with surrogate ovalbumin antigen demonstrate that the modified bacterium is fully immunogenic and capable of inducing specific T cell responses. Altogether, the data presented here strongly support a novel and efficient method for reshaping the current BCG vaccine that replaces the laborious conventional approach of complementation with exogenous nucleic acids.

With the general procedures described above, the feasibility of BCG surface biotinylation and decoration with surrogate antigen OVA was examined. The immunogenicity of the modified BCG was then tested in vivo. The bacterial surface was easily labeled with biotin for rapid display of avidin chimeric antigens without any detectable changes in bacterial phenotypes. The resulting modified BCG is efficiently ingested by antigen presentation cells and can induce an OVA-specific immune ...

Watch this Scientific Journal Video about Expression of Exogenous Antigens in the Mycobacterium bovis BCG Vaccine via Non-genetic Surface Decoration with the Avidin-biotin System at JoVE.com

Expression of Exogenous Antigens in the Mycobacterium bovis BCG Vaccine via Non-genetic Surface Decoration with the Avidin-biotin System

A novel technique for rapid antigen display on a bacterial surface is presented, which involves surface biotinylation followed by exposure to proteins of interest in fusion with monomeric avidin. Loading BCG with selected antigens successfully improves its immunogenicity, suggesting that surface decoration can replace traditional genetic approaches.

Expression of Exogenous Antigens in the Mycobacterium bovis BCG Vaccine via Non-genetic Surface Decoration with the Avidin-biotin System

Tuberculosis (TB) is a serious infectious disease and the only available vaccine M. bovis bacillus Calmette-Gu&#233;rin (BCG) is safe and effective for ...

The overall goal of this procedure is to express surface proteins on mycobacterium using surface decoration with recombinant proteins as an alternative to traditional, genetic-based approaches. These methods can help answer important research questions in the field of mycobacteriology, especially in the area of hospital interactions and the vaccine developments. This technique can be used to screen for potential interference factors or antigen candidates.It can be the and rapidly compared to fastidious and time-consuming traditional genetic-based approaches. Demonstrating this procedure will be Amina Talal, a research assistant in my lab. This portion of the protocol begins with transforming P17 Aviden OVA plasmid into E.Coli BL21.To do so, induce 250 milliliters of E.Coli BL21 culture with IPTG for three hours at 37 degrees Celsius. After three hours, lyse the bacteria to solubilize the inclusion bodies by first pelleting the induced BL21 culture and discarding the supernatant. Then re-suspend the pellet in 10 milliliters of lysis buffer and allow the cells to be lysed for 15 minutes.Then continue the incubation at room temperature using a rotator for agitation, and let it go overnight. In the morning, centrifuge the mixture for half an hour. Then collect the supernatant containing the solubilized inclusion bodies.Next purify the Aviden OVA proteins using a nickel NTA column. First, dilute the supernatant one to two in lysis buffer and estimate the volume. Then prep%re a column containing four milliliters of nickel NTA resin per 250 milliliters of diluted supernatant and load the dilution onto the column.Next, wash the column three times using 10 milliliters of lysis buffer at pH seven per wash. To collect the recombinant protein, wash the column with lysis buffer containing imidazole and collect the eluate. If your recombinant protein is free from inclusion bodies, the following is procedure that will good for many proteins in our lab.First, adjust the pH of the refolding solution to be one unit above or below the protein's isoelectric point. Then, gradually vortex and dilute the protein to a 1 to 10 dilution in refolding solution. Then incubate the protein on a magnetic stirrer for 30 minutes at room temperature to complete the refolding process.Next, de-salt and buffer exchange the refolded proteins into PBS using a protein concentrator. Follow by centrifuging the column and store aloquats of soluble protein at 20 degrees Celsius. Work in a biosafety cabinet using personal protective equipment because BCG is a level 2 pathogen.To biotinylate the surface of BCG cells, first grow the cells on a shaker platform to the proper density. Collect about one billion cells and wash them three times using 500 microliters of ice-cold, endotoxin-free PBST. Then, spin down the cells, and suspend them in sterile, endotoxin-free PBS.Next, prepare fresh 10 millimolar sulfo-NHSSS biotin in sterile filtered water. Then incubate bacteria in one milliliter of broth containing 0.5 millimolar of sulfo-NHSSS Biotin. Perform the incubation at room temperature for 30 minutes.Next wash the now labeled bacteria three times with 500 microliters of ice-cold PBST, as before to remove the un-reacted re-agent. Then, re-suspend the pellet in one milliliter of PBST. To evaluate the biotinylation efficiency, stain an aloquat of 100 million biotinylated BCG with 25 microliters of Strepravidin-FITC.Then, briefly incubate the stained bacteria in para-formaldehyde, and then measure the level of biotinylation using flow cytometry. After assessing the growth of and survival of the biotinylated mycobacteria, proceed with binding the Aviden fusion protein to them. First, mix 500 million biotinylated BCGs with Aviden fusion protein for a final concentration of 10 micrograms of protein per milliliter.Let this reaction go for an hour at room temperature on a shaker. Next, wash the bacteria three times with 500 microliters of ice-cold PBST. Then stain the bacteria with rabbit anti-Aviden antibody for 20 minutes at room temperature.After 20 minutes, perform one wash step with 500 microliters of ice-cold PBST. Then, stain the bacteria with FITC-conjugated goat anti-rabbit IGG antibody. Next, wash the bacteria using 500 microliters of ice-cold PBST, and analyze the bacteria by flow cytometry to evaluate the surface decoration.After following the described protocol, cytology shows that there were minimal levels of OVA binding to non-biotinylated bacteria and significant levels of OVA binding to biotinylated bacteria. Importantly, the levels of Aviden OVA on the bacterial surface remained stable and detectable one month after lyophilization and storage at room temperature. Next, RAW cells and dsRed bacteria were used to perform a phagocytosis assay.Pleasingly, there was no deterrence in the macrophage phenotype. To exam Aviden OVA decorated BCGs fate within macrophages, adherent RAW cells were infected and examined by florescence microscopy. Aviden OVA was not just present on the bacterial surface, but also detached and trans-located to cytoplasm far from the bacteria.An immuno-gold staining experiment showed that Aviden OVA antigens can detach from the BCG surface, cross the phagosomal membrane and travel toward the cytosol. Macrophages infected with Aviden OVA BCG showed co-localization of Avi OVA with IA molecules. This suggests that Aviden fusion proteins detach and trans-locate to antigen presentation compartments to be loaded onto MHC2 molecules.Aviden OVA peptides also co-localized with class I molecules within BCG phagosomes, as shown by H2K staining. Thus, there is potential presentation of Avi OVA antigen to CD8 positive T-cells by the macrophage. After watching this video, you should have a good understanding of how to express proteins in mycobacteria, and this organism hard to manipulate with current genetic methods.After the technique, we use it successfully to load the vaccine with the mycobacteria antigen is at six. Then we showed that the modified vaccines was opportunity to use as specific immuno response in the mouse model. We are currently collaborating with to explore this approach in teratine We proposed to use BCG upgraded with selected antigen or immunobulators.

expression-exogenous-antigens-mycobacterium-bovis-bcg-vaccine-via-non

Research

JoVE Journal

Immunology and Infection

A Functional Whole Blood Assay to Measure Viability of Mycobacteria, using Reporter-Gene Tagged BCG or M.Tb (BCG lux/M.Tb lux)

Functional assays have long played a key role in measuring of immunogenicity of a given vaccine. This is conventionally expressed as serum bactericidal titers. Studies of serum bactericidal titers in response to childhood vaccines have enabled us to develop and validate cut-off levels for protective immune responses and such cut-offs are in routine use. No such assays have been taken forward into the routine assessment of vaccines that induce primarily cell-mediated immunity in the form of effector T cell responses, such as TB vaccines. In the animal model, the performance of a given vaccine candidate is routinely evaluated in standardized bactericidal assays, and all current novel TB-vaccine candidates have been subjected to this step in their evaluation prior to phase 1 human trials. The assessment of immunogenicity and therefore likelihood of protective efficacy of novel anti-TB vaccines should ideally undergo a similar step-wise evaluation in the human models now, including measurements in bactericidal assays.
Bactericidal assays in the context of tuberculosis vaccine research are already well established in the animal models, where they are applied to screen potentially promising vaccine candidates. Reduction of bacterial load in various organs functions as the main read-out of immunogenicity. However, no such assays have been incorporated into clinical trials for novel anti-TB vaccines to date.
Although there is still uncertainty about the exact mechanisms that lead to killing of mycobacteria inside human macrophages, the interaction of macrophages and T cells with mycobacteria is clearly required. The assay described in this paper represents a novel generation of bactericidal assays that enables studies of such key cellular components with all other cellular and humoral factors present in whole blood without making assumptions about their relative individual contribution. The assay described by our group uses small volumes of whole blood and has already been employed in studies of adults and children in TB-endemic settings. We have shown immunogenicity of the BCG vaccine, increased growth of mycobacteria in HIV-positive patients, as well as the effect of anti-retroviral therapy and Vitamin D on mycobacterial survival in vitro. Here we summarise the methodology, and present our reproducibility data using this relatively simple, low-cost and field-friendly model.
Note: Definitions/Abbreviations
BCG lux = M. bovis BCG, Montreal strain, transformed with shuttle plasmid pSMT1 carrying the luxAB genes from Vibrio harveyi, under the control of the mycobacterial GroEL (hsp60) promoter. 
CFU = Colony Forming Unit (a measure of mycobacterial viability).

A Functional Whole Blood Assay to Measure Viability of Mycobacteria, using Reporter-Gene Tagged BCG or M.Tb BCG lux/M.Tb lux

We describe an alternative approach to the enumeration of mycobacteria in vitro, which uses reporter-gene tagged mycobacteria instead of colony-forming units (CFU). &#x201C;Survival&#x201D; of organisms as well as host response-markers are measured simultaneously, providing a low-cost, versatile and functional system for studies of host/pathogen interactions in the context of tuberculosis.

Functional assays have long played a key role in measuring of immunogenicity of a given vaccine. This is conventionally expressed as serum bactericidal ...

Generation of Recombinant Arenavirus for Vaccine Development in FDA-Approved Vero Cells

The development and implementation of arenavirus reverse genetics represents a significant breakthrough in the arenavirus field 4. The use of cell-based arenavirus minigenome systems together with the ability to generate recombinant infectious arenaviruses with predetermined mutations in their genomes has facilitated the investigation of the contribution of viral determinants to the different steps of the arenavirus life cycle, as well as virus-host interactions and mechanisms of arenavirus pathogenesis 1, 3, 11 . In addition, the development of trisegmented arenaviruses has permitted the use of the arenavirus genome to express additional foreign genes of interest, thus opening the possibility of arenavirus-based vaccine vector applications 5 . Likewise, the development of single-cycle infectious arenaviruses capable of expressing reporter genes provides a new experimental tool to improve the safety of research involving highly pathogenic human arenaviruses 16 . The generation of recombinant arenaviruses using plasmid-based reverse genetics techniques has so far relied on the use of rodent cell lines 7,19 , which poses some barriers for the development of Food and Drug Administration (FDA)-licensed vaccine or vaccine vectors. To overcome this obstacle, we describe here the efficient generation of recombinant arenaviruses in FDA-approved Vero cells.

Rescue of recombinant arenaviruses from cloned cDNAs, an approach referred to as reverse genetics, allows researchers to investigate the role of specific viral gene products, as well as the contribution of their different specific domains and residues, to many different aspects of the biology of arenavirus. Likewise, reverse genetics techniques in FDA-approved cell lines (Vero) for vaccine development provides novel possibilities for the generation of effective and safe vaccines to combat human pathogenic arenaviruses.

The development and implementation of arenavirus reverse genetics represents a significant breakthrough in the arenavirus field  4. The use of cell-based ...

Expression of Functional Recombinant Hemagglutinin and Neuraminidase Proteins from the Novel H7N9 Influenza Virus Using the Baculovirus Expression System

The baculovirus expression system is a powerful tool for expression of recombinant proteins. Here we use it to produce correctly folded and glycosylated versions of the influenza A virus surface glycoproteins - the hemagglutinin (HA) and the neuraminidase (NA). As an example, we chose the HA and NA proteins expressed by the novel H7N9 virus that recently emerged in China. However the protocol can be easily adapted for HA and NA proteins expressed by any other influenza A and B virus strains. Recombinant HA (rHA) and NA (rNA) proteins are important reagents for immunological assays such as ELISPOT and ELISA, and are also in wide use for vaccine standardization, antibody discovery, isolation and characterization. Furthermore, recombinant NA molecules can be used to screen for small molecule inhibitors and are useful for characterization of the enzymatic function of the NA, as well as its sensitivity to antivirals. Recombinant HA proteins are also being tested as experimental vaccines in animal models, and a vaccine based on recombinant HA was recently licensed by the FDA for use in humans. The method we describe here to produce these molecules is straight forward and can facilitate research in influenza laboratories, since it allows for production of large amounts of proteins fast and at a low cost. Although here we focus on influenza virus surface glycoproteins, this method can also be used to produce other viral and cellular surface proteins.

Here we describe a way to express correctly folded and functional influenza virus surface antigens derived from the novel Chinese H7N9 virus in insect cells. The technique can be adapted to express ectodomains of any viral or cellular surface proteins.

The baculovirus expression system is a powerful tool for expression of  recombinant proteins. Here we use it to produce correctly folded and  glycosylated ...

In Vitro Analysis of Myd88-mediated Cellular Immune Response to West Nile Virus Mutant Strain Infection

An attenuated West Nile virus (WNV), a nonstructural (NS) 4B-P38G mutant, induced higher innate cytokine and T cell responses than the wild-type WNV in mice. Recently, myeloid differentiation factor 88 (MyD88) signaling was shown to be important for initial T cell priming and memory T cell development during WNV NS4B-P38G mutant infection. In this study, two flow cytometry-based methods &#8211; an in vitro T cell priming assay and an intracellular cytokine staining (ICS) &#8211; were utilized to assess dendritic cells (DCs) and T cell functions. In the T cell priming assay, cell proliferation was analyzed by flow cytometry following co-culture of DCs from both groups of mice with carboxyfluorescein succinimidyl ester (CFSE) - labeled CD4+ T cells of OTII transgenic mice. This approach provided an accurate determination of the percentage of proliferating CD4+ T cells with significantly improved overall sensitivity than the traditional assays with radioactive reagents. A microcentrifuge tube system was used in both cell culture and cytokine staining procedures of the ICS protocol. Compared to the traditional tissue culture plate-based system, this modified procedure was easier to perform at biosafety level (BL) 3 facilities. Moreover, WNV- infected cells were treated with paraformaldehyde in both assays, which enabled further analysis outside BL3 facilities. Overall, these in vitro immunological assays can be used to efficiently assess cell-mediated immune responses during WNV infection.

In Vitro Analysis of Myd88-mediated Cellular Immune Response to West Nile Virus Mutant Strain Infection

Two flow cytometry-based methods &#8211; an in vitro T cell priming assay and intracellular cytokine staining were utilized to measure antigen presenting capacity of dendritic cells and antigen-specific T cell responses to a West Nile virus mutant infection in mice.

An attenuated West Nile virus (WNV), a nonstructural (NS) 4B-P38G mutant, induced higher innate cytokine and T cell responses than the wild-type WNV in ...

Development of an in vitro model system for studying the interaction of Equus caballus IgE with its high-affinity receptor Fc&#949;RI

The interaction of IgE with its high-affinity Fc receptor (Fc&#949;RI) followed by an antigenic challenge is the principal pathway in IgE mediated allergic reactions. As a consequence of the high affinity binding between IgE and Fc&#949;RI, along with the continuous production of IgE by B cells, allergies usually persist throughout life, with currently no permanent cure available. Horses, especially race horses, which are commonly inbred, are a species of mammals that are very prone to the development of hypersensitivity responses, which can seriously affect their performance. Physiological responses to allergic sensitization in horses mirror that observed in humans and dogs. In this paper we describe the development of an in situ assay system for the quantitative assessment of the release of mediators of the allergic response pertaining to the equine system. To this end, the gene encoding equine Fc&#949;RI&#945; was transfected into and expressed onto the surface of parental Rat Basophil Leukemia (RBL-2H3.1) cells. The gene product of the transfected equine &#945;-chain formed a functional receptor complex with the endogenous rat &#946;- and &#947;-chains 1. The resultant assay system facilitated an assessment of the quantity of mediator secreted from equine Fc&#949;RI&#945; transfected RBL-2H3.1 cells following sensitization with equine IgE and antigenic challenge using &#946;-hexosaminidase release as a readout 2, 3. Mediator release peaked at 36.68% &#177; 4.88% at 100 ng ml-1 of antigen. This assay was modified from previous assays used to study human and canine allergic responses 4, 5. We have also shown that this type of assay system has multiple applications for the development of diagnostic tools and the safety assessment of potential therapeutic intervention strategies in allergic disease 6, 2, 3.

Development of an &lt;em&gt;in vitro&lt;/em&gt; model system for studying the interaction of &lt;em&gt;Equus&lt;/em&gt; &lt;em&gt;caballus&lt;/em&gt; IgE with its high-affinity receptor Fc&amp;#949;RI

The current study describes the development and applications of a genetically engineered assay system based on the transfection of rat basophilic leukemia cells with the equine Fc&#949;RI&#945; gene. Transfected cells express a functional receptor where the release of mediators of the allergic response can be activated by IgE and antigen.

The interaction of IgE with its high-affinity Fc receptor (Fc&#949;RI) followed by an antigenic challenge is the principal pathway in IgE mediated ...

A CFSE-based Assay to Study the Migration of Murine Skin Dendritic Cells into Draining Lymph Nodes During Infection with Mycobacterium bovis Bacille Calmette-Gu&#233;rin

Dendritic cells (DCs) are important for initiating immune responses, in part through their ability to acquire and shuttle antigen to the draining lymph node (DLN). The mobilization of DCs to the DLN is complex and remains to be fully elucidated during infection. Herein described is the use of an innovative, simple assay that relies on the fluorochrome 5- and 6-carboxyfluorescein diacetate succinimidyl ester (CFSE) to track the migration of DCs during footpad infection with Mycobacterium bovis Bacille Calmette-Gu&#233;rin (BCG) in C57BL/6 mice. This assay enables the characterization of skin DC sub-populations that actively relocate to the draining, popliteal LN in response to BCG. This protocol originates from a BCG model where migratory skin DCs were identified by flow cytometry. The assay is amiable to the study and identification of DCs or other cells that home to the popliteal LN after inoculation of microbes, their metabolites or other inflammatory stimuli in the footpad, and consequently to study factors that regulate the migration of these cells.

A CFSE-based Assay to Study the Migration of Murine Skin Dendritic Cells into Draining Lymph Nodes During Infection with &lt;em&gt;Mycobacterium bovis&lt;/em&gt; Bacille Calmette-Gu&amp;#233;rin

An assay in mice to track cell migration from skin to draining lymph node is described which enables the characterization of skin Dendritic cells mobilized to the lymph node after footpad infection with Bacille Calmette-Gu&#233;rin.

Dendritic cells (DCs) are important for initiating immune responses, in part through their ability to acquire and shuttle antigen to the draining lymph ...

Analysis of Lymphocyte Extravasation Using an In Vitro Model of the Human Blood-brain Barrier

Lymphocyte extravasation into the central nervous system (CNS) is critical for immune surveillance. Disease-related alterations of lymphocyte extravasation might result in pathophysiological changes in the CNS. Thus, investigation of lymphocyte migration into the CNS is important to understand inflammatory CNS diseases and to develop new therapy approaches. Here we present an in vitro model of the human blood-brain barrier to study lymphocyte extravasation. Human brain microvascular endothelial cells (HBMEC) are confluently grown on a porous polyethylene terephthalate transwell insert to mimic the endothelium of the blood-brain barrier. Barrier function is validated by zonula occludens immunohistochemistry, transendothelial electrical resistance (TEER) measurements as well as analysis of evans blue permeation. This model allows investigation of the diapedesis of rare lymphocyte subsets such as CD56brightCD16dim/- NK cells. Furthermore, the effects of other cells, cytokines and chemokines, disease-related alterations, and distinct treatment regimens on the migratory capacity of lymphocytes can be studied. Finally, the impact of inflammatory stimuli as well as different treatment regimens on the endothelial barrier can be analyzed.

Analysis of Lymphocyte Extravasation Using an In Vitro Model of the Human Blood-brain Barrier

Here, we describe a human blood-brain barrier model enabling to investigate lymphocyte transmigration into the central nervous system in vitro.

Lymphocyte extravasation into the central nervous system (CNS) is critical for immune surveillance. Disease-related alterations of lymphocyte ...

Purification of the Membrane Compartment for Endoplasmic Reticulum-associated Degradation of Exogenous Antigens in Cross-presentation

Dendritic cells (DCs) are highly capable of processing and presenting internalized exogenous antigens upon major histocompatibility class (MHC) I molecules also known as cross-presentation (CP). CP plays an important role not only in the stimulation of na&#239;ve CD8+ T cells and memory CD8+ T cells for infectious and tumor immunity but also in the inactivation of self-acting na&#239;ve T cells by T cell anergy or T cell deletion. Although the critical molecular mechanism of CP remains to be elucidated, accumulating evidence indicates that exogenous antigens are processed through endoplasmic reticulum-associated degradation (ERAD) after export from non-classical endocytic compartments. Until recently, characterizations of these endocytic compartments were limited because there were no specific molecular markers other than exogenous antigens. The method described here is a new vesicle isolation protocol, which allows for the purification of these endocytic compartments. Using this purified microsome, we reconstituted the ERAD-like transport, ubiquitination, and processing of the exogenous antigen in vitro, suggesting that the ubiquitin-proteasome system processed the exogenous antigen after export from this cellular compartment. This protocol can be further applied to other cell types to clarify the molecular mechanism of CP.

The method described here is a new vesicle isolation protocol, which allows for the purification of the cellular compartments where exogenous antigens are processed by endoplasmic reticulum-associated degradation in cross-presentation.

Dendritic cells (DCs) are highly capable of processing and presenting internalized exogenous antigens upon major histocompatibility class (MHC) I ...

Imaging Mycobacterium tuberculosis in Mice with Reporter Enzyme Fluorescence

Reporter enzyme fluorescence (REF) utilizes substrates that are specific for enzymes present in target organisms of interest for imaging or detection by fluorescence or bioluminescence. We utilize BlaC, an enzyme expressed constitutively by all M. tuberculosis strains. REF allows rapid quantification of bacteria in lungs of infected mice. The same group of mice can be imaged at many time points, greatly reducing costs, enumerating bacteria more quickly, allowing novel observations in host-pathogen interactions, and increasing statistical power, since more animals per group are readily maintained. REF is extremely sensitive due to the catalytic nature of the BlaC enzymatic reporter and specific due to the custom flourescence resonance energy transfer (FRET) or fluorogenic substrates used. REF does not require recombinant strains, ensuring normal host-pathogen interactions. We describe the imaging of M. tuberculosis infection using a FRET substrate with maximal emission at 800 nm. The wavelength of the substrate allows sensitive deep tissue imaging in mammals. We will outline aerosol infection of mice with M. tuberculosis, anesthesia of mice, administration of the REF substrate, and optical imaging. This method has been successfully applied to evaluating host-pathogen interactions and efficacy of antibiotics targeting M. tuberculosis.

Imaging Mycobacterium tuberculosis in Mice with Reporter Enzyme Fluorescence

We describe the optical imaging of mice infected with Mycobacterium tuberculosis (M. tuberculosis) using reporter enzyme fluorescence (REF). This protocol facilitates the sensitive and specific detection of M. tuberculosis in pre-clinical animal models for pathogenesis, therapeutics and vaccine research.

Reporter enzyme fluorescence (REF) utilizes substrates that are specific for enzymes present in target organisms of interest for imaging or detection by ...

Single-cell Quantitation of mRNA and Surface Protein Expression in Simian Immunodeficiency Virus-infected CD4+ T Cells Isolated from Rhesus macaques

Single-cell analysis is an important tool for dissecting heterogeneous populations of cells. The identification and isolation of rare cells can be difficult. To overcome this challenge, a methodology combining indexed flow cytometry and high-throughput multiplexed quantitative polymerase chain reaction (qPCR) was developed. The objective was to identify and characterize simian immunodeficiency virus (SIV)-infected cells present within rhesus macaques. Through quantitation of surface protein by fluorescence-activated cell sorting (FACS) and mRNA by qPCR, virus-infected cells are identified by viral gene expression, which is combined with host gene and protein measurements to create a multidimensional profile. We term the approach, targeted Single-Cell Proteo-transcriptional Evaluation, or tSCEPTRE. To perform the method, viable cells are stained with fluorescent antibodies specific for surface markers used for FACS isolation of a cell subset and/or downstream phenotypic analysis. Single cells are sorted followed by immediate lysis, multiplex reverse transcription (RT), PCR pre-amplification, and high throughput qPCR of up to 96 transcripts. FACS measurements are recorded at the time of sorting and subsequently linked to the gene expression data by well position to create a combined protein and transcriptional profile. To study SIV-infected cells directly ex vivo, cells were identified by qPCR detection of multiple viral RNA species. The combination of viral transcripts and the quantity of each provide a framework for classifying cells into distinct stages of the viral life cycle (e.g., productive versus non-productive). Moreover, tSCEPTRE of SIV+ cells were compared to uninfected cells isolated from the same specimen to assess differentially expressed host genes and proteins. The analysis revealed previously unappreciated viral RNA expression heterogeneity among infected cells as well as in vivo SIV-mediated post-transcriptional gene regulation with single-cell resolution. The tSCEPTRE method is relevant for the analysis of any cell population amenable to identification by expression of surface protein marker(s), host or pathogen gene(s), or combinations thereof.

Single-cell Quantitation of mRNA and Surface Protein Expression in Simian Immunodeficiency Virus-infected CD4+ T Cells Isolated from Rhesus macaques

Described is a methodology to quantitate the expression of 96 genes and 18 surface proteins by single cells ex vivo, allowing for the identification of differentially expressed genes and proteins in virus-infected cells relative to uninfected cells. We apply the approach to study SIV-infected CD4+ T cells isolated from rhesus macaques.