Identification and HLA restriction of naturally derived Th1-cell epitopes from the secreted Mycobacterium tuberculosis antigen 85B recognized by antigen-specific human CD4(+) T-cell lines

Mucosal and systemic immune responses after a single intranasal dose of nanoparticle and spore-based subunit vaccines in mice with pre-existing lung mycobacterial immunity

Tuberculosis (TB) is a major global health threat that claims more than one million lives annually. With a quarter of the global population harbouring latent TB, post-exposure vaccination aimed at high-risk populations that could develop active TB disease would be of great public health benefit. Mucosal vaccination is an attractive approach for a predominantly lung disease like TB because it elicits both local and systemic immunity. However, the immunological consequence of mucosal immunisation in the presence of existing lung immunity remains largely unexplored. Using a mycobacterial pre-exposure mouse model, we assessed whether pre-existing mucosal and systemic immune responses can be boosted and/or qualitatively altered by intranasal administration of spore- and nanoparticle-based subunit vaccines. Analysis of lung T cell responses revealed an increasing trend in the frequency of important CD4 and CD8 T cell subsets, and T effector memory cells with a Th1 cytokine (IFNγ and TNFα) signature among immunised mice. Additionally, significantly greater antigen specific Th1, Th17 and IL-10 responses, and antigen-induced T cell proliferation were seen from the spleens of immunised mice. Measurement of antigen-specific IgG and IgA from blood and bronchoalveolar lavage fluid also revealed enhanced systemic and local humoral immune responses among immunised animals. Lastly, peripheral blood mononuclear cells (PBMCs) obtained from the TB-endemic country of Mozambique show that individuals with LTBI showed significantly greater CD4 T cell reactivity to the vaccine candidate as compared to healthy controls. These results support further testing of Spore-FP1 and Nano-FP1 as post-exposure TB vaccines.

Peptide-Based Vaccines for Tuberculosis

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis. As a result of the coronavirus disease 2019 (COVID-19) pandemic, the global TB mortality rate in 2020 is rising, making TB prevention and control more challenging. Vaccination has been considered the best approach to reduce the TB burden. Unfortunately, BCG, the only TB vaccine currently approved for use, offers some protection against childhood TB but is less effective in adults. Therefore, it is urgent to develop new TB vaccines that are more effective than BCG. Accumulating data indicated that peptides or epitopes play essential roles in bridging innate and adaptive immunity and triggering adaptive immunity. Furthermore, innovations in bioinformatics, immunoinformatics, synthetic technologies, new materials, and transgenic animal models have put wings on the research of peptide-based vaccines for TB. Hence, this review seeks to give an overview of current tools that can be used to design a peptide-based vaccine, the research status of peptide-based vaccines for TB, protein-based bacterial vaccine delivery systems, and animal models for the peptide-based vaccines. These explorations will provide approaches and strategies for developing safer and more effective peptide-based vaccines and contribute to achieving the WHO's End TB Strategy.

Fusion Protein Vaccine Based on Ag85B and STEAP1 Induces a Protective Immune Response against Prostate Cancer

(1) Background: There are currently limited treatments for castration-resistant prostate cancer. Immunotherapy involving Sipuleucel-T has increasingly drawn attention for prostate cancer management. BCG plays a vital role in treating bladder cancer, mainly by inducing immune activation, but is rarely used for prostate cancer. (2) Methods: The TCGA database, PCR, and Western blotting were used to analyze the expression of STEAP1 in mouse and human tissues. Then, we constructed a fusion protein vaccine with Mycobacterium tuberculosis Ag85B and three repeated octapeptide epitopes of a six-transmembrane epithelial antigen of the prostate 1 (STEAP1_186-193), Ag85B-3×STEAP1_186-193. The uptake of the fusion protein vaccine by DCs was evaluated by confocal microscopy, and DC markers were detected using flow cytometry after incubation with the fusion protein. The immune response against prostate cancer was evaluated by the LDH assay and xenografts in vitro and in vivo. Then, the tumor microenvironment was determined using IHC and ELISA. In addition, the epitope was mutated using CRISPR-Cas9 to illustrate that the fusion protein elicited immunization against STEAP1. (3) Results: The TCGA database analysis, PCR, and Western blotting showed that STEAP1 was highly expressed in human and murine prostate cancer. After the uptake of the purified fusion protein vaccine by DCs, CD11c, CD80, CD86, and MHC II were upregulated and triggered a cytotoxic T lymphocyte (CTL) response against TRAMP-C1 and RM1 cells in vitro. Furthermore, the fusion protein vaccine inhibited tumor growth and improved the tumor microenvironment in vivo, with more CD3⁺ cells and fewer FOXP3⁺ cells in the tumor. Serum IFN-γ and IL-2 were significantly higher than in the control group, while IL-4 expression was lower, indicating that the fusion protein vaccine activated Th1 immunity. The immune response against prostate cancer was greatly suppressed when the antigen targets were knocked out using CRISPR-Cas9. (4) Conclusion: In summary, our results provide the first evidence that a vaccine based on a fusion protein consisting of Ag85B and a prostate cancer octapeptide epitope with complete Freund’s adjuvant (CFA), triggers a robust immune response and inhibits tumor growth in murine prostate cancer.

Secretory System Components as Potential Prophylactic Targets for Bacterial Pathogens

Bacterial secretory systems are essential for virulence in human pathogens. The systems have become a target of alternative antibacterial strategies based on small molecules and antibodies. Strategies to use components of the systems to design prophylactics have been less publicized despite vaccines being the preferred solution to dealing with bacterial infections. In the current review, strategies to design vaccines against selected pathogens are presented and connected to the biology of the system. The examples are given for Y. pestis, S. enterica, B. anthracis, S. flexneri, and other human pathogens, and discussed in terms of effectiveness and long-term protection.

Intranasal immunization with peptide-based immunogenic complex enhances BCG vaccine efficacy in a murine model of tuberculosis

Prime-boost immunization strategies are required to control the global tuberculosis (TB) pandemic, which claims approximately 3 lives every minute. Here, we have generated an immunogenic complex against Mycobacterium tuberculosis (M.tb), consisting of promiscuous T cell epitopes (M.tb peptides) and TLR ligands assembled in liposomes. Interestingly, this complex (peptide–TLR agonist–liposomes; PTL) induced significant activation of CD4⁺ T cells and IFN-γ production in the PBMCs derived from PPD⁺ healthy individuals as compared with PPD^– controls. Furthermore, intranasal delivery of PTL significantly reduced the bacterial burden in the infected mice by inducing M.tb-specific polyfunctional (IFN-γ⁺IL-17⁺TNF-α⁺IL-2⁺) immune responses and long-lasting central memory responses, thereby reducing the risk of TB recurrence in DOTS-treated infected animals. The transcriptome analysis of peptide-stimulated immune cells unveiled the molecular basis of enhanced protection. Furthermore, PTL immunization significantly boosted the Bacillus Calmette-Guerin–primed (BCG-primed) immune responses against TB. The greatly enhanced efficacy of the BCG-PTL vaccine model in controlling pulmonary TB projects PTL as an adjunct vaccine against TB.

Immunological Characterization of Proteins Expressed by Genes Located in Mycobacterium tuberculosis-Specific Genomic Regions Encoding the ESAT6-like Proteins

The 6 kDa early secreted antigen target (ESAT6) is a low molecular weight and highly immunogenic protein of Mycobacterium tuberculosis with relevance in the diagnosis of tuberculosis and subunit vaccine development. The gene encoding the ESAT6 protein is located in the M. tuberculosis-specific genomic region known as the region of difference (RD)1. There are 11 M. tuberculosis-specific RDs absent in all of the vaccine strains of BCG, and three of them (RD1, RD7, and RD9) encode immunodominant proteins. Each of these RDs has genes for a pair of ESAT6-like proteins. The immunological characterizations of all the possible proteins encoded by genes in RD1, RD7 and RD9 have shown that, besides ESAT-6 like proteins, several other proteins are major antigens useful for the development of subunit vaccines to substitute or supplement BCG. Furthermore, some of these proteins may replace the purified protein derivative of M. tuberculosis in the specific diagnosis of tuberculosis by using interferon-gamma release assays and/or tuberculin-type skin tests. At least three subunit vaccine candidates containing ESAT6-like proteins as antigen components of multimeric proteins have shown efficacy in phase 1 and phase II clinical trials in humans.

Fusion of Dendritic Cells Activating Rv2299c Protein Enhances the Protective Immunity of Ag85B-ESAT6 Vaccine Candidate against Tuberculosis

In Mycobacterium tuberculosis infection, naïve T cells that encounter mycobacterial antigens through dendritic cells (DCs) induce various CD4⁺ T-cell responses; therefore, appropriate DC activation is the key for protective immunity against tuberculosis. We previously found that Rv2299c-matured DCs induce Th1 differentiation with bactericidal activity. In this study, to prove that Rv2299c could enhance the protective immunity of other vaccine candidates comprising T-cell-stimulating antigens, Ag85B-ESAT6, a well-known vaccine candidate, was selected as a fusion partner of Rv2299c. Recombinant Rv2299c-Ag85B-ESAT6 protein induced DC maturation and activation. Furthermore, fusion of Rv2299c enhanced the protective efficacy of the Ag85B-ESAT6 vaccine in a mouse model and significantly higher production of TNF-α and IL-2 was detected in the lungs, spleen, and lymph nodes of the group immunized with the Rv2299c-fused protein than with Ag85B-ESAT6. In addition, fusion of Rv2299c enhanced the Ag85B-ESAT6-mediated expansion of multifunctional CD4⁺ T cells. These data suggested that the DC-activating protein Rv2299c may potentiate the protective immunity of the vaccine candidate comprising T cell antigens.

Nanoscale Peptide Self-assemblies Boost BCG-primed Cellular Immunity Against Mycobacterium tuberculosis

Bacillus Calmette-Guerin (BCG) is the only vaccine against TB and has limited protection efficacy, which wanes past adolescence. Multifunctional CD8+ T cells (IFN-γ+/TNF-α+/IL-2+) are associated with lower reactivation risk and enhanced control of active Mtb infection. Since boosting with BCG is contraindicated, booster vaccines that augment T cell immunity in the lungs of BCG-vaccinated individuals are urgently needed. We developed a vaccination strategy based on self-assembling peptide nanofibers presenting Mtb-specific CD8+ or CD4+ T cell epitopes that induce high frequency and antigen-specific effector memory T cells producing IFN-γ and IL-2. Intranasal immunization with peptide nanofibers was well tolerated in mice leading to increased antigen-specific CD8+ T cell population in the lungs. Co-assembled nanofibers of CD8+ T cell epitopes and toll-like receptor 2 (TLR2) agonists induced a 8-fold expansion in multifunctional CD8+ T cell populations in the lungs of vaccinated mice. Aerosol challenge with Mtb in BCG-primed and nanofiber-boosted mice provided an additional 0.5-log CFU reduction in lung bacterial load and indicating enhanced protection compared to BCG alone. Together, these data suggest that heterologous prime-boost with BCG and peptide nanofiber vaccines induces cell mediated immunity in the lung, reduces bacterial burden, and is a potentially safer alternative for boosting BCG-primed immunity.

Integrating Non-human Primate, Human, and Mathematical Studies to Determine the Influence of BCG Timing on H56 Vaccine Outcomes

Tuberculosis (TB) is the leading cause of death by an infectious agent, and developing an effective vaccine is an important component of the WHO's EndTB Strategy. Non-human primate (NHP) models of vaccination are crucial to TB vaccine development and have informed design of subsequent human trials. However, challenges emerge when translating results from animal models to human applications, and connecting post-vaccination immunological measurements to infection outcomes. The H56:IC31 vaccine is a candidate currently in phase I/IIa trials. H56 is a subunit vaccine that is comprised of 3 mycobacterial antigens: ESAT6, Ag85B, and Rv2660, formulated in IC31 adjuvant. H56, as a boost to Bacillus Calmette-Guérin (BCG, the TB vaccine that is currently used in most countries world-wide) demonstrates improved protection (compared to BCG alone) in mouse and NHP models of TB, and the first human study of H56 reported strong antigen-specific T cell responses to the vaccine. We integrated NHP and human data with mathematical modeling approaches to improve our understanding of NHP and human response to vaccine. We use a mathematical model to describe T-cell priming, proliferation, and differentiation in lymph nodes and blood, and calibrate the model to NHP and human blood data. Using the model, we demonstrate the impact of BCG timing on H56 vaccination response and reveal a general immunogenic response to H56 following BCG prime. Further, we use uncertainty and sensitivity analyses to isolate mechanisms driving differences in vaccination response observed between NHP and human datasets. This study highlights the power of a systems biology approach: integration of multiple modalities to better understand a complex biological system.

Integrating Non-human Primate, Human, and Mathematical Studies to Determine the Influence of BCG Timing on H56 Vaccine Outcomes

Background

Acute lung injury (ALI) is characterized by suppressed fibrinolytic activity in bronchoalveolar lavage fluid (BALF) attributed to elevated plasminogen activator inhibitor-1 (PAI-1). Restoring pulmonary fibrinolysis by delivering tissue-type plasminogen activator (tPA), urokinase plasminogen activator (uPA), and plasmin could be a promising approach.

Objectives

To systematically analyze the overall benefit of fibrinolytic therapy for ALI reported in preclinical studies.

Methods

We searched PubMed, Embase, Web of Science, and CNKI Chinese databases, and analyzed data retrieved from 22 studies for the beneficial effects of fibrinolytics on animal models of ALI.

Results

Both large and small animals were used with five routes for delivering tPA, uPA, and plasmin. Fibrinolytics significantly increased the fibrinolytic activity both in the plasma and BALF. Fibrin degradation products in BALF had a net increase of 408.41 ng/ml vs controls (P < 0.00001). In addition, plasma thrombin–antithrombin complexes increased 1.59 ng/ml over controls (P = 0.0001). In sharp contrast, PAI-1 level in BALF decreased 21.44 ng/ml compared with controls (P < 0.00001). Arterial oxygen tension was improved by a net increase of 15.16 mmHg, while carbon dioxide pressure was significantly reduced (11.66 mmHg, P = 0.0001 vs controls). Additionally, fibrinolytics improved lung function and alleviated inflammation response: the lung wet/dry ratio was decreased 1.49 (P < 0.0001 vs controls), lung injury score was reduced 1.83 (P < 0.00001 vs controls), and BALF neutrophils were lesser (3 × 10⁴/ml, P < 0.00001 vs controls). The mortality decreased significantly within defined study periods (6 h to 30 days for mortality), as the risk ratio of death was 0.2-fold of controls (P = 0.0008).

Conclusion

We conclude that fibrinolytic therapy may be effective pharmaceutic strategy for ALI in animal models.

Rational design, preparation and characterization of recombinant Ag85B variants and their glycoconjugates with T-cell antigenic activity against Mycobacterium tuberculosis

Tuberculosis is the deadliest infectious disease in the world. The variable efficacy of the current treatments highlights the need for more effective agents against this disease. In the past few years, we focused on the investigation of antigenic glycoconjugates starting from recombinant Ag85B (rAg85B), a potent protein antigen from Mycobacterium tuberculosis. In this paper, structural modifications were rationally designed in order to obtain a rAg85B variant protein able to maintain its immunogenicity after glycosylation. Lysine residues involved in the main T-epitope sequences (namely, K30 and K282) have been substituted with arginine to prevent their glycosylation by a lysine-specific reactive linker. The effectiveness of the mutation strategy and the detailed structure of resulting neo-glycoconjugates have been studied by intact mass spectrometry, followed by peptide and glycopeptide mapping. The effect of K30R and K282R mutations on the T-cell activity of rAg85B has also been investigated with a preliminary immunological evaluation performed by enzyme-linked immunospotting on the different variant proteins and their glycosylation products. After glycosylation, the two variant proteins with an arginine in position 30 completely retain the original T-cell activity, thus representing adequate antigenic carriers for the development of efficient glycoconjugate vaccines against tuberculosis.

A phase I, open-label trial on the safety and immunogenicity of the adjuvanted tuberculosis subunit vaccine H1/IC31® in people living in a TB-endemic area

BACKGROUND

H1/IC31® is a tuberculosis (TB) subunit vaccine candidate consisting of the fusion protein of Ag85B and ESAT-6 (H1) formulated with the IC31® adjuvant. Previous trials have reported on the H1/IC31® vaccine in M. tuberculosis (Mtb)-naïve, BCG-vaccinated and previously Mtb-infected individuals. In this trial, conducted between December 2008 and April 2010, the safety and immunogenicity of H1/IC31® was assessed in participants living in Ethiopia - a highly TB-endemic area.

METHODS

Healthy male participants aged 18-25 years were recruited into four groups. Participants in group 1 (N = 12) and group 2 (N = 12) were Tuberculin Skin Test (TST) negative and QuantiFERON-TB Gold in-tube test (QFT) negative (Mtb-naïve groups), participants in group 3 (N = 3) were TST positive and QFT negative (BCG group), and participants in group 4 (N = 12) were both TST and QFT positive (Mtb-infected group). H1 vaccine alone (group 1) or H1 formulated with the adjuvant IC31® (groups 2, 3 and 4) was administered intramuscularly on day 0 and day 56. Safety and immunogenicity parameters were evaluated for up to 32 weeks after day 0.

RESULTS

The H1/IC31®vaccine was safe and generally well tolerated. There was little difference among the four groups, with a tendency towards a higher incidence of adverse events in Mtb-infected compared to Mtb-naïve participants. Two serious adverse events were reported in the Mtb-infected group where a relationship to the vaccine could not be excluded. In both cases the participants recovered without sequelae within 72 h. Immunogenicity assays, evaluated in the 29 participants who received both vaccinations, showed a stronger response to TB antigens in the Mtb-naïve group vaccinated with the adjuvant.

CONCLUSION

The trial confirmed the need for an adjuvant for the vaccine to be immunogenic and highlighted the importance of early phase testing of a novel TB vaccine candidate in TB-endemic areas.

TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT01049282. Retrospectively registered on 14 January 2010.

Biosensor-based detection of tuberculosis

Tuberculosis (TB), caused byMycobacterium tuberculosis(M.tb.), is one of the most prevalent and serious infectious diseases worldwide with an estimated annual global mortality of 1.4 million in 2010.

First-in-human trial of the post-exposure tuberculosis vaccine H56:IC31 in Mycobacterium tuberculosis infected and non-infected healthy adults

BACKGROUND

H56:IC31 is a candidate tuberculosis vaccine comprising a fusion protein of Ag85B, ESAT-6 and Rv2660c, formulated in IC31 adjuvant. This first-in-human, open label phase I trial assessed the safety and immunogenicity of H56:IC31 in healthy adults without or with Mycobacterium tuberculosis (M.tb) infection.

METHODS

Low dose (15 μg H56 protein in 500 nmol IC31) or high dose (50 μg H56, 500 nmol IC31) vaccine was administered intramuscularly thrice, at 56-day intervals. Antigen-specific T cell responses were measured by intracellular cytokine staining and antibody responses by ELISA.

RESULTS

One hundred and twenty-six subjects were screened and 25 enrolled and vaccinated. No serious adverse events were reported. Nine subjects (36%) presented with transient cardiovascular adverse events. The H56:IC31 vaccine induced antigen-specific IgG responses and Th1 cytokine-expressing CD4(+) T cells. M.tb-infected vaccinees had higher frequencies of H56-induced CD4(+) T cells than uninfected vaccinees. Low dose vaccination induced more polyfunctional (IFN-γ(+)TNF-α(+)IL-2(+)) and higher frequencies of H56-specific CD4(+) T cells compared with high dose vaccination. A striking increase in IFN-γ-only-expressing CD4(+) T cells, displaying a CD45RA(-)CCR7(-) effector memory phenotype, emerged after the second high-dose vaccination in M.tb-infected vaccinees. TNF-α(+)IL-2(+) H56-specific memory CD4(+) T cells were detected mostly after low-dose H56 vaccination in M.tb-infected vaccinees, and predominantly expressed a CD45RA(-)CCR7(+) central memory phenotype. Our results support further clinical testing of H56:IC31.

Comparative evaluation of booster efficacies of BCG, Ag85B, and Ag85B peptides based vaccines to boost BCG induced immunity in BALB/c mice: a pilot study

Purpose

In the present study booster efficacies of Ag85 B, Bacillus Calmette-Guerin (BCG), and Ag85B peptides were evaluated using prime boost regimes in BALB/c mice.

Materials and Methods

Mice were primed with BCG vaccine and subsequently boosted with Ag85B, BCG and cocktail of Ag85B peptides.

Results

Based on analysis of immune response it was observed mice boosted with Ag85B peptides showed significant (p < 0.001) cytokines levels (interferon γ, interleukin 12) and BCG specific antibodies (anti-BCG and anti-purified protein derivative titre) compared to booster dose of BCG, Ag85B and BCG alone.

Conclusion

Our pilot results suggest that prime boost regimes with Ag85B peptides can boost waning BCG induced immunity and may improve immunogenicity of BCG vaccine. However, lot of work is further needed using experimental model of tuberculosis infection to justify the result.

The use of signal peptide domains as vaccine candidates

Signal peptide (SP) domains have a common motif but also sequence specific features. This knowledge was mainly ignored by immunologists who considered SP as generic, short-lived, targeting sequences. Consequently, while SP-derived MHC class I, class II and HLA-E epitopes have been isolated, their use as antigen-specific vaccine candidates (VCs) was mostly neglected. Recently we demonstrated the rational of selecting entire SP domains as multi-epitope long peptide VCs based on their high T and B-cell epitope densities. This review summarizes preclinical and clinical results demonstrating the various advantages of human SP domain VCs derived from both bacterial and tumor antigens. Such vaccine design provides for a straightforward, yet unique immunotherapeutic means of generating robust, non-toxic, diversified, combined antigen-specific CD4+/CD8+ T/B-cell immunity, irrespective of patient HLA repertoire also in disease associated transporter-associated with antigen processing (TAP) deficiencies. Subsequent clinical trials will further assess the full potential of this approach.

The Immunodominant T-Cell Epitopes of the Mycolyl-Transferases of the Antigen 85 Complex of M. tuberculosis

The Ag85 complex is a 30–32 kDa family of three proteins (Ag85A, Ag85B, and Ag85C), which all three possess enzymatic mycolyl-transferase activity involved in the coupling of mycolic acids to the arabinogalactan of the cell wall and in the biogenesis of cord factor. By virtue of their strong potential to induce Th1-type immune responses, important for the control of intracellular infections, members of the Ag85 family rank among the most promising TB vaccine candidate antigens. Ag85A and Ag85B, initially purified from Mycobacterium bovis bacillus Calmette–Guérin (BCG)/Mycobacterium tuberculosis culture filtrate respectively, induce strong T-cell proliferation and IFN-γ production in most healthy individuals latently infected with M. tuberculosis and in BCG-vaccinated mice and humans but not in tuberculosis patients. Members of the Ag85 complex are highly conserved in other mycobacterial species. Mice and humans infected with Mycobacterium ulcerans or cattle infected with M. bovis or Mycobacterium avium subsp. paratuberculosis also show strong T-cell responses to this protein family. Using synthetic overlapping peptides, bio-informatic prediction programs and tetramer-binding studies, a number of immunodominant CD4⁺ and CD8⁺ T-cell epitopes have been identified in experimental animal models as well as in humans, using proliferation and Th1 cytokine secretion as main read-outs. The results from these studies are summarized in this review.

In silico predicted mycobacterial epitope elicits in vitro T-cell responses

Epitope-based vaccines permit the selection of only a specific subset of epitopes to induce the necessary immune response, thus providing a rational alternative to conventional design approaches. Using a range of immunoinformatics tools, we identified a novel, contiguous 28 amino acid multi-epitope cluster within the highly conserved secretory protein Ag85B of Mycobacterium tuberculosis, the causative agent of TB. This cluster, named Ep85B, is composed of epitopes which bind to three HLA Class I and 15 Class II molecules, and harbors the potential to generate 99% population coverage in TB-endemic regions. We experimentally evaluated the capacity of Ep85B to elicit T-cell immune responses using whole blood cells and, as predicted, observed significant increases in populations of both CD4+ and memory CD4+ CD45RO+ T-cells. Our results demonstrate the practical utility of an epitope-based design methodology - a strategy that, following further evaluation, may serve as an additional tool for the development of novel vaccine candidates against TB and other diseases.

Cellular immune responses to recombinant Mycobacterium bovis BCG constructs expressing major antigens of region of difference 1 of Mycobacterium tuberculosis

Besides being the most widely used vaccine directed against tuberculosis (TB) worldwide, Mycobacterium bovis BCG is also the most controversial vaccine in current use. Its protective efficacy varies widely in different parts of the world. One approach to improving the current BCG vaccine might be to produce recombinant BCG strains that express major antigens encoded by genes that are present in the M. tuberculosis-specific region of difference 1 (RD1), such as pe35, cfp10, and esat6. In this study, pe35, cfp10, and esat6 genes were cloned into shuttle plasmid pDE22 to generate the recombinant plasmids PDE22-PE35, PDE22-CFP10, and PDE22-ESAT6, which were electroporated into BCG to generate recombinant BCGs (rBCGs). The cellular immune responses (antigen-induced proliferation and secretion of selected T helper 1 [Th1], Th2, and anti-inflammatory cytokines, i.e., gamma interferon [IFN-γ], interleukin 5 [IL-5], and IL-10, respectively) that are specific to the proteins of cloned genes were studied by using spleen cells from mice immunized with native BCGs and rBCGs and synthetic peptides covering the protein sequence of the cloned genes. The results showed that the spleen cells did not secrete IL-5, whereas IL-10 was secreted in response to peptides of all three proteins from mice immunized with rBCGs only, suggesting expression of the cloned genes and in vivo priming of spleen cells to the expressed proteins. However, in Th1 cell assays that correlate with protective cellular immune responses, i.e., antigen-induced proliferation and IFN-γ secretion, only mice immunized with rBCG-pDE22-PE35 yielded positive responses to the peptides of PE35. These results suggest that rBCG-PDE22-PE35 is the only one of the three vaccines used in this work that is worthy of consideration as a new vaccine candidate against TB.

Identification of T cell epitopes of Mycobacterium tuberculosis with biolistic DNA vaccination

Tuberculosis (TB) has been listed as one of the most prevalent and serious infectious diseases worldwide. The etiological pathogen of TB is Mycobacterium tuberculosis (Mtb), a facultative intracellular bacterium. Mycobacterium bovis bacillus Calmette-Guérin (BCG) is the only approved vaccine against TB to date. BCG has been widely used, but the efficacy is questionable, especially in adult pulmonary TB. Therefore, more effective, safe and reliable TB vaccines have been urgently needed. T cell-mediated cellular immune response is a key immune response for effective protective immunity against TB. DNA vaccines using Mtb antigens have been studied as promising future TB vaccines. Most TB DNA vaccine studies so far reported used intramuscular or intradermal injection with needles, as these methods tend to induce a type 1 helper T lymphocyte (Th1)-type immune response that is critical for the protective immunity. We have been using DNA vaccines with gene gun bombardment for T cell epitope identification of various Mtb antigens. We show here our strategy to identify precise Mtb T cell epitopes using DNA vaccines with gene gun bombardment.

In silico analysis and experimental validation of Mycobacterium tuberculosis -specific proteins and peptides of Mycobacterium tuberculosis for immunological diagnosis and vaccine development

Comparative analyses of the Mycobacterium tuberculosis genome with the genomes of other mycobacteria have led to the identification of several genomic regions of difference (RDs) between M. tuberculosis and M. bovis BCG. The identification of immunodominant and HLA-promiscuous antigens and peptides encoded by these RDs could be useful for diagnosis and the development of new vaccines against tuberculosis. The analysis of RD proteins and peptides by in silico methods (using computational programs to predict major and HLA-promiscuous antigenic proteins and peptides) and experimental validations (using peripheral blood mononuclear cells and sera from tuberculosis patients and BCG-vaccinated healthy subjects to assess antigen-specific cellular and humoral immune responses in vitro) identified several major antigens and peptides. To evaluate the in vivo potentials, the genes of immunodominant antigens were cloned and expressed in DNA vaccine vectors. Immunizations of experimental animals with the recombinant constructs induced antigen-specific cellular responses. Further experiments showed that each of these proteins had several T and B cell epitopes scattered throughout their sequence, which confirmed their strong immunogenicity. In conclusion, the bioinformatics-based in silico identification of promiscuous antigens and peptides of M. tuberculosis is a useful approach to identify new candidates important for diagnosis and vaccine applications.

Cytokines in response to proteins predicted in genomic regions of difference of Mycobacterium tuberculosis

Cellular immune responses are responsible for both protection and pathogenesis in tuberculosis, and are mediated/regulated by a complex network of pro-inflammatory, T helper (Th) type 1 and type 2 cytokines. In this study, the secretion of pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, IL-8 and IL-1β; Th1 cytokines interferon-gamma (IFN-γ), IL-2 and tumor necrosis factor-beta (TNF-β); and Th2 cytokines IL-4, IL-5 and IL-10 by the peripheral blood mononuclear cells (PBMCs) of pulmonary tuberculosis patients was studied. PBMCs were cultured in vitro in the absence and presence of complex mycobacterial antigens and peptides corresponding to 11 regions of difference (RD) of Mycobacterium tuberculosis that are deleted/absent in all vaccine strains of Mycobacterium bovis bacillus Calmette-Guérin (BCG). The culture supernatants were tested for secreted cytokines by FlowCytomix assay. PBMCs from the majority of patients (53-100%) spontaneously secreted detectable concentrations of all cytokines tested, except for IL2 (29%) and IL-10 (41%). The profiles of proinflammatory cytokines were largely similar for various complex antigens or RD peptides. However, with respect to Th1 and Th2 cytokines, the antigens could be divided into three groups; the first with Th1-bias (culture filtrate of M. tuberculosis, RD1, RD5, RD7, RD9 and RD10), the second with Th2-bias (whole cells and cell walls of M. tuberculosis, RD12, RD13 and RD15), and the third without Th1/Th2-bias (M. bovis BCG, RD4, RD6 and RD11). Complex mycobacterial antigens and RD proteins with Th1- and Th2-biases may have roles in protection and pathogenesis of tuberculosis, respectively.

Signal peptides and trans-membrane regions are broadly immunogenic and have high CD8+ T cell epitope densities: Implications for vaccine development

Cell mediated immune response has a major role in controlling the elimination of infectious agents. The rational design of sub-unit peptide vaccines against intracellular pathogens or cancer requires the use of antigenic sequence/s that can induce highly potent, long lasting and antigen-specific responses in the majority of the population. A promising peptide selection strategy is the detection of multi-epitope peptide sequences with an ability to bind multiple MHC alleles. While past research sought the best epitopes based on their specific antigenicity, we ask whether specific defined domains have high epitope densities. Signal peptides and trans-membrane domains were found to have exceptionally high epitope densities. The improved MHC binding of these domains relies on their hydrophobic nature and, in signal peptides, also on their specific sequence. The high epitope density of SP was computed using in-silico methods and corroborated by the high percentage of identified SP epitope in the IEDB (immune epitope database). The enhanced immunogenicity of SP was then experimentally confirmed using a panel of nine peptides derived from Mycobacterium tuberculosis (MTb) proteins used in human PBMC proliferation assays and T cell lines functional assays. Our results show the exceptionally high antigen specific response rates and population coverage to SP sequences compared with non-SP peptide antigens derived from the same proteins. The results suggest a novel scheme for the rational design of T cell vaccines using a domain based rather than an epitope based approach.

Field test of a novel detection device for Mycobacterium tuberculosis antigen in cough

Background

Tuberculosis is a highly infectious disease that is spread from person to person by infected aerosols emitted by patients with respiratory forms of the disease. We describe a novel device that utilizes immunosensor and bio-optical technology to detect M. tuberculosis antigen (Ag85B) in cough and demonstrate its use under field conditions during a pilot study in an area of high TB incidence.

Methods

The TB Breathalyzer device (Rapid Biosensor Systems Ltd) was field tested in the outpatient clinic of Adama Hospital, Ethiopia. Adults seeking diagnosis for respiratory complaints were tested. Following nebulization with 0.9% saline patients were asked to cough into a disposable collection device where cough aerosols were deposited. Devices were then inserted into a portable instrument to assess whether antigen was present in the sample. Demographic and clinical data were recorded and all patients were subjected to chest radiogram and examination of sputum by Ziehl-Nielsen microscopy. In the absence of culture treatment decisions were based on smear microscopy, chest x-ray and clinical assessment. Breathalyzer testing was undertaken by a separate physician to triage and diagnostic assessment.

Results

Sixty individuals were each subjected to a breathalyzer test. The procedure was well tolerated and for each patient the testing was completed in less than 10 min. Positive breath test results were recorded for 29 (48%) patients. Of 31 patients with a diagnosis of tuberculosis 23 (74%; 95% CI 55-87) were found positive for antigen in their breath and 20 (64%; 95% CI 45-80) were smear positive for acid fast bacilli in their sputum. Six patients provided apparent false positive breathalyzer results that did not correlate with a diagnosis of tuberculosis.

Conclusions

We propose that the breathalyzer device described warrants further investigation as a tool for studying exhalation of M. tuberculosis. The portability, simplicity of use and speed of the test device suggest it may also find use as a tool to aid early identification of infectious cases. We recommend studies be undertaken to determine the diagnostic sensitivity and specificity of the device when compared to microbiological and clinical indicators of tuberculosis disease.

Identification of HLA-DR4-restricted T-cell epitope on MPT51 protein, a major secreted protein derived from Mycobacterium tuberculosis using MPT51 overlapping peptides screening and DNA vaccination

We identified a novel HLA-DR4-restricted CD4+ T-cell epitope on a secreted antigen of Mycobacterium tuberculosis, MPT51, in 004149-MM HLA-DR4-transgenic mice which express HLA-DRB1*0401, but not murine MHC class II molecules. The mice were immunized with plasmid DNA encoding MPT51 using gene gun and interferon (IFN)-gamma production from the immune splenocytes was analyzed. In response to overlapping synthetic peptides covering the mature MPT51 sequence, only one peptide, p191-210, stimulated the splenocytes to produce IFN-gamma. Further analysis using flow cytometry and computer-assisted algorithm, ProPred, narrowed down the region of CD4+ T-cell epitope to p191-202. The CD4+ T-cell epitope would be feasible for vaccine design against tuberculosis as well as for analysis of MPT51-specific T-cells in M. tuberculosis infection.

Characterization of human cellular immune responses to Mycobacterium tuberculosis proteins encoded by genes predicted in RD15 genomic region that is absent in Mycobacterium bovis BCG

RD15 is a genomic region of difference (RD) present in Mycobacterium tuberculosis H37Rv but absent in all strains of Mycobacterium bovis BCG. RD15 contains genes encoding proteins of mammalian cell entry (Mce3A-F), important for the invasion and survival of M. tuberculosis in host cells. In this study, we have evaluated cellular immune responses to RD15 proteins using peripheral blood mononuclear cells (PBMC) from pulmonary tuberculosis patients and M. bovis BCG-vaccinated healthy subjects. PBMC were tested for T-helper (Th) type 1 [antigen-induced proliferation and interferon (IFN)-gamma secretion] and anti-inflammatory [interleukin (IL)-10 secretion] responses to complex mycobacterial antigens and peptides corresponding to proteins of RD1 and RD15. In Th1 assays, complex mycobacterial antigens induced strong responses in both donor groups, and RD1 induced strong responses in tuberculosis patients and moderate responses in healthy subjects, whereas RD15 induced weak responses in tuberculosis patients and strong to moderate responses in healthy subjects. IL-10 secretion in both donor groups was strong to moderate in response to complex mycobacterial antigens, but weak in response to RD1 and RD15. Analysis of IFN-gamma : IL-10 ratios showed strong Th1 biases to complex mycobacterial antigens and RD1 in both donor groups, and to RD15 and RD1504 (Mce3A) in healthy subjects only. These results suggest that RD1504 is the best Th1-stimulating antigen present in RD15, and therefore may be a potential vaccine candidate against TB.

Mycobacterium tuberculosis origin of replication and the promoter for immunodominant secreted antigen 85B are the targets of MtrA, the essential response regulator

Efficient proliferation of Mycobacterium tuberculosis (Mtb) inside macrophage requires that the essential response regulator MtrA be optimally phosphorylated. However, the genomic targets of MtrA have not been identified. We show by chromatin immunoprecipitation and DNase I footprinting that the chromosomal origin of replication, oriC, and the promoter for the major secreted immunodominant antigen Ag85B, encoded by fbpB, are MtrA targets. DNase I footprinting analysis revealed that MtrA recognizes two direct repeats of GTCACAgcg-like sequences and that MtrA approximately P, the phosphorylated form of MtrA, binds preferentially to these targets. The oriC contains several MtrA motifs, and replacement of all motifs or of a single select motif with TATATA compromises the ability of oriC plasmids to maintain stable autonomous replication in wild type and MtrA-overproducing strains, indicating that the integrity of the MtrA motif is necessary for oriC replication. The expression of the fbpB gene is found to be down-regulated in Mtb cells upon infection when these cells overproduce wild type MtrA but not when they overproduce a nonphosphorylated MtrA, indicating that MtrA approximately P regulates fbpB expression. We propose that MtrA is a regulator of oriC replication and that the ability of MtrA to affect apparently unrelated targets, i.e. oriC and fbpB, reflects its main role as a coordinator between the proliferative and pathogenic functions of Mtb.

Immunoprophylaxis of tuberculosis: an update of emerging trends

Developing effective prophylactics to combat tuberculosis is currently in an exploratory stage. The HIV pandemic and emergence of multi- and extensively drug-resistant strains of Mycobacterium tuberculosis indicate that the current preventive measures against this ever-evolving pathogen are inadequate. The currently available vaccine BCG in its present form affords variable protection which usually wanes with aging. Various reasons have been cited to explain the discrepancies in the efficacy of BCG, including generic differences in the different BCG vaccine strains used in immunization program throughout the world. The low efficacy of BCG vaccine has promoted the search for novel vaccines for tuberculosis. The search strategies aim at completely replacing the existing vaccine and/or augmenting/improving the current BCG vaccine. Among new vaccine candidates are live attenuated M. tuberculosis vaccines, recombinant BCG, DNA vaccines, subunit vaccine, and fusion protein-based vaccines. More than 200 new vaccine candidates have been developed as a result of research work over the past few years. To date, at least eight vaccine candidates are undergoing clinical evaluation, with a few of them successfully qualifying in the first phase of clinical testing. These recent advances present an optimistic insight whereby a new tuberculosis vaccine might be expected to be available for public use in the next few years.

Immunological memory transferred with CD4 T cells specific for tuberculosis antigens Ag85B-TB10.4: persisting antigen enhances protection

Background

High levels of death and morbidity worldwide caused by tuberculosis has stimulated efforts to develop a new vaccine to replace BCG. A number of Mycobacterium tuberculosis (Mtb)-specific antigens have been synthesised as recombinant subunit vaccines for clinical evaluation. Recently a fusion protein of TB antigen Ag85B combined with a second immunodominant TB antigen TB10.4 was emulsified with a novel non-phospholipid-based liposomal adjuvant to produce a new subunit vaccine, investigated here. Currently, there is no consensus as to whether or not long-term T cell memory depends on a source of persisting antigen. To explore this and questions regarding lifespan, phenotype and cytokine patterns of CD4 memory T cells, we developed an animal model in which vaccine-induced CD4 memory T cells could transfer immunity to irradiated recipients.

Methodology/Principal Findings

The transfer of protective immunity using Ag85B-TB10.4-specific, CD45RB^low CD62L^low CD4 T cells was assessed in sub-lethally irradiated recipients following challenge with live BCG, used here as a surrogate for virulent Mtb. Donor T cells also carried an allotype marker allowing us to monitor numbers of antigen-specific, cytokine-producing CD4 T cells in recipients. The results showed that both Ag85B-TB10.4 and BCG vaccination induced immunity that could be transferred with a single injection of 3×10⁶ CD4 T cells. Ten times fewer numbers of CD4 T cells (0.3×10⁶) from donors immunised with Ag85B-TB10.4 vaccine alone, transferred equivalent protection. CD4 T cells from donors primed by BCG and boosted with the vaccine similarly transferred protective immunity. When BCG challenge was delayed for 1 or 2 months after transfer (a test of memory T cell survival) recipients remained protected. Importantly, recipients that contained persisting antigen, either live BCG or inert vaccine, showed significantly higher levels of protection (p<0.01). Overall the numbers of IFN-γ-producing CD4 T cells were poorly correlated with levels of protection.

Conclusions/Significance

The Ag85B-TB10.4 vaccine, with or without BCG-priming, generated TB-specific CD4 T cells that transferred protective immunity in mice challenged with BCG. The level of protection was enhanced in recipients containing a residual source of specific antigen that could be either viable or inert.

Non-clinical efficacy and safety of HyVac4:IC31 vaccine administered in a BCG prime-boost regimen

Despite the extensive success with the introduction of M. bovis Bacille Calmette-Guérin (BCG), tuberculosis (TB) remains a major global epidemic infecting between 8 and 9 million people annually with an estimated 1.7 million deaths each year. However, because of its demonstrated effectiveness against some of the most severe forms of childhood TB, it is now realized that BCG vaccination of newborns is unlikely to be replaced. Therefore, BCG or an improved BCG will continue to be used as a prime TB vaccine and there is a need to develop effective boost vaccines that would enhance and prolong the protective immunity induced by BCG prime immunization. We report on a heterologous booster approach using two highly immunogenic TB antigens comprising Ag85B and TB10.4 (HyVac4) delivered as a fusion molecule and formulated in the proprietary adjuvant IC31. This vaccine was found to be immunogenic and demonstrated greater protection in the more stringent guinea pig model of pulmonary tuberculosis than BCG alone when used in a prime/boost regimen. Significant difference in lung involvement was observed for all animals in the HyVac4 boosted group compared to BCG alone regardless of time to death or sacrifice. A vaccine toxicology study of the HyVac4:IC31 regimen was performed and it was judged safe to advance the vaccine into clinical trials. Therefore, all non-clinical data supports the suitability of HyVac4 as a safe, immunogenic, and effective vaccination in a prime-boost regimen with BCG.

Identification of Mycobacterium tuberculosis vaccine candidates using human CD4+ T-cells expression cloning

To identify Mycobacterium tuberculosis (Mtb) antigens as candidates for a subunit vaccine against tuberculosis (TB), we have employed a CD4+ T-cell expression screening method. Mtb-specific CD4+ T-cell lines from nine healthy PPD positive donors were stimulated with different antigenic substrates including autologous dendritic cells (DC) infected with Mtb, or cultured with culture filtrate proteins (CFP), and purified protein derivative of Mtb (PPD). These lines were used to screen a genomic Mtb library expressed in Escherichia coli and processed and presented by autologous DC. This screening led to the recovery of numerous T-cell antigens, including both novel and previously described antigens. One of these novel antigens, referred to as Mtb9.8 (Rv0287), was recognized by multiple T-cell lines, stimulated with either Mtb-infected DC or CFP. Using the mouse and guinea pig models of TB, high levels of IFN-gamma were produced, and solid protection from Mtb challenge was observed following immunization with Mtb9.8 formulated in either AS02A or AS01B Adjuvant Systems. These results demonstrate that T-cell screening of the Mtb genome can be used to identify CD4+ T-cell antigens that are candidates for vaccine development.

Characterization of human cellular immune responses to novel Mycobacterium tuberculosis antigens encoded by genomic regions absent in Mycobacterium bovis BCG

Comparative genomics has identified several regions of differences (RDs) between the infectious Mycobacterium tuberculosis and the vaccine strains of Mycobacterium bovis BCG. We aimed to evaluate the cellular immune responses induced by antigens encoded by genes predicted in 11 RDs. Synthetic peptides covering the sequences of RD1, RD4 to RD7, RD9 to RD13, and RD15 were tested for antigen-induced proliferation and secretion of Th1 cytokine, gamma interferon (IFN-gamma), by peripheral blood mononuclear cells (PBMC) obtained from culture-proven pulmonary tuberculosis (TB) patients and M. bovis BCG-vaccinated healthy subjects. Among the peptide pools, RD1 induced the best responses in both donor groups and in both assays. In addition, testing of TB patients' PBMC for secretion of proinflammatory cytokines (tumor necrosis factor alpha [TNF-alpha], interleukin 6 [IL-6], IL-8, and IL-1beta), Th1 cytokines (IFN-gamma, IL-2, and TNF-beta), and Th2 cytokines (IL-4, IL-5, and IL-10) showed differential effects of RD peptides in the secretion of IFN-gamma and IL-10, with high IFN-gamma/IL-10 ratios (32 to 5.0) in response to RD1, RD5, RD7, RD9, and RD10 and low IFN-gamma/IL-10 ratios (<1.0) in response to RD12, RD13, and RD15. Peptide-mixing experiments with PBMC from healthy subjects showed that secretion of large quantities of IL-10 in response to RD12 and RD13 correlated with inhibition of Th1 responses induced by RD1 peptides. In conclusion, our results suggest that M. tuberculosis RDs can be divided into two major groups--one group that activates PBMC to preferentially secrete IFN-gamma and another group that activates preferential secretion of IL-10--and that these two groups of RDs may have roles in protection against and pathogenesis of TB, respectively.

Efficient testing of large pools of Mycobacterium tuberculosis RD1 peptides and identification of major antigens and immunodominant peptides recognized by human Th1 cells

Comparative genomics has identified several regions of difference (RDs) of Mycobacterium tuberculosis that are deleted or absent in Mycobacterium bovis BCG vaccines. To determine their relevance for diagnostic and vaccine applications, it is imperative that efficient methods are developed to test the encoded proteins for immunological reactivity. In this study, we have used 220 synthetic peptides covering sequences of 12 open reading frames (ORFs) of RD1 and tested them as a single pool (RD1(pool)) with peripheral blood mononuclear cells obtained from pulmonary tuberculosis (TB) patients and M. bovis BCG-vaccinated healthy subjects in Th1 cell assays that measure antigen-induced proliferation and IFN-gamma secretion. The results showed that RD1(pool) induced strong responses in both TB patients and BCG-vaccinated healthy subjects. The subsequent testing of peptide pools of individual ORFs revealed that all ORFs induced positive responses in a portion of donors, but PPE68, CFP10, and ESAT6 induced strong responses in TB patients and PPE68 induced strong responses in BCG-vaccinated healthy subjects. In addition, HLA-DR and -DQ typing of donors and HLA-DR binding prediction analysis of proteins suggested HLA-promiscuous presentation of PPE68, CFP10, and ESAT6. Further testing of individual peptides showed that a single peptide of PPE68 (121-VLTATNFFGINTIPIALTEMDYFIR-145) was immunodominant. The search for sequence homology revealed that a part of this peptide, 124-ATNFFGINTIPIAL-137, was present in several PPE family proteins of M. tuberculosis and M. bovis BCG vaccines. Further experiments limited the promiscuous and immunodominant epitope region to the 10-amino-acid cross-reactive sequence 127-FFGINTIPIA-136.

Influence of HLA-DRB1 alleles on Th1 and Th2 cytokine response to Mycobacterium tuberculosis antigens in pulmonary tuberculosis

The influence of human leukocyte antigens (HLA) on the immune response is well established. We investigated the regulatory role of HLA-DRB1 alleles on cytokine response to live M. tuberculosis and its culture filtrate antigen (CFA) in normal healthy subjects (NHS) and pulmonary tuberculosis (PTB) patients. Th1 (IFN-gamma and IL-12p40), Th2 (IL-4 and IL-5), pro-inflammatory (IL-6 and IL-8) and anti-inflammatory (TGF-beta and IL-10) cytokines were measured by ELISA in 72-h-old peripheral blood mononuclear cell culture supernatants from 58 NHS and 48 PTB patients. HLA-DRB1 genotyping was carried out by polymerase chain reaction and dot-blot hybridization with biotinylated sequence-specific oligonucleotide probes and detection by chemiluminescence. In response to live M. tuberculosis and CFA, significantly increased levels of IL-6, IL-8 and TGF-beta and decreased IFN-gamma, IL-12p40 and IL-10 were seen in PTB patients compared to NHS. We observed a significantly increased IFN-gamma response in HLA-DRB1*03-positive NHS (p=0.03) and decreased IFN-gamma response in HLA-DRB1*15-positive patients (p=0.04) than respective allele-negative individuals. An increased level of IL-12p40 in DRB1*10 (p=0.02) and IL-10 in DRB1*12- (p=0.03) positive NHS and an increased level of IL-6 in DRB1*04- (p=0.02) positive patients were observed. The study suggests that HLA-DRB1 alleles differentially modulate the various cytokine responses to M. tuberculosis antigens, which may influence the cellular and humoral immune responses to M. tuberculosis infection in a susceptible host.

Validation of peptide epitope microarray experiments and extraction of quality data

INTRODUCTION

Within the last decade, the development of antigen microarray slides has enabled the simultaneous measurement of serum reactivity to hundreds of peptides in a single biological sample. Despite this considerable scientific progress, many issues remain regarding the quality, analysis and interpretation of the data these slides produce. There is currently no accepted approach to guide data analysis, and researchers use a wide variety of statistical methods and software tools. We designed and implemented a laboratory experiment to assess the reliability and range of measurement of peptide microarray data, and present graphical and statistical procedures for pre-processing so that quality data can be extracted for addressing biological hypotheses.

METHODS

Synthetic peptides spanning the proteins Ag85A, Ag85B, CFP10, MPT51/MPB51, TB10.4 and ESAT-6 were chosen as a paradigm to screen for serum reactivity to Mycobacteria tuberculosis (MTB). We explored various quantitative and graphical methods for presenting the responses from a slide. We replicated assays of samples from five TB-positive individuals to examine reproducibility, and used linear mixed models to investigate the various sources of variability, and to assess the range of measurement. We use our methods to extract data from the five TB-positive individuals and five healthy controls, and analyse the "normalized" responses using the freely available SAM package.

RESULTS

The ratio of foreground to background signal (on a log scale) provides an appropriate response index. A two-dimensional graphical display clearly illustrates the responses from the control and peptide features on a slide. Mixed model analysis of the replicated slides found a high reproducibility of the assay between operators, days and experiments. The range of measurement was also satisfactory. Our analysis of the normalized responses from the five TB-positive patients and five healthy controls suggested that 10 of the 363 peptides assessed had significantly higher responses in the TB-positive group.

CONCLUSIONS

Carefully designed laboratory experiments and rigorous statistical analysis can enable the removal of technical artefacts to produce quality peptide array data for addressing biological hypotheses. These instruments, which enable valid comparisons across slides and/or batches of slides, will escort future comparative analyses targeting high content serum reactivity profiling against a broad array of B-cell epitopes.

Mycobacterium tuberculosis Antigen 85A induces Th-1 immune responses in systemic sarcoidosis

Sarcoidosis is a granulomatous disease of unknown etiology, characterized by a Th-1 immunophenotype. Although humoral immune responses by sarcoidosis subjects to mycobacterial proteins have been detected, mycobacterial antigens capable of inducing cellular immune responses in sarcoidosis subjects have not been reported. We used the enzyme-linked immunospot assay to assess for recognition of the Mycobacterium tuberculosis mycolyl transferase, Antigen 85A, by peripheral blood mononuclear cells from 25 sarcoidosis subjects, 22 PPD- (purified protein derivative) healthy volunteers, and 16 PPD+ healthy subjects. Reactivity to Ag85A whole protein was observed in 15 of 25 sarcoidosis subjects compared to 2 of 22 PPD- subjects (p=0.0006, Fisher's exact test) and to 14 of 16 PPD+ subjects (p=0.084, Fisher's exact test). Monoclonal antibody against HLA-DR inhibited recognition. In addition to immune recognition of Ag85A whole protein, peptide-mapping studies identified four immunogenic Ag85A peptides, which induced Th-1 immune responses in individual sarcoidosis subjects, suggesting that multiple epitopes from a mycobacterial protein may have a role in sarcoidosis immunopathogenesis.

TB vaccine strategies--what is needed to solve a complex problem?

An estimated 2 billion people are latently infected with Mycobacterium tuberculosis, the majority of which are already BCG vaccinated and repeatedly sensitized to mycobacterial strains from the environment. To be successful in the high endemic regions, any future TB vaccine strategy will have to be tailored in accordance with the resulting complexity of the TB infection and anti-mycobacterial immune response. In this review we will discuss some of the most advanced attempts to address this challenge.

HLA homozygosity does not adversely affect measles vaccine-induced cytokine responses

The association between HLA homozygosity and measles-specific Th(1) (IFN-gamma, IL-2 and IL-12p40) and Th(2) (IL-4 and IL-10) cytokine responses were assessed in a group of 339 healthy schoolchildren 12-18 years of age previously immunized with two doses of live-attenuated measles virus vaccine. No associations were observed between class I HLA homozygosity and measles-specific cytokine levels. Children who were homozygous at the class II DRB1, DQA1, DPA1 and DPB1 loci had higher median IFN-gamma secretion levels compared with children who were heterozygous for DRB1 (77.7 vs. 39.5 pg/ml, p=0.05), DQA1 (60.9 vs. 36.6 pg/ml, p=0.03), DPA1 (46.1 vs. 27.1 pg/ml, p=0.01) and DPB1 (61.5 vs. 36.0 pg/ml, p=0.01) loci, respectively. Homozygosity at increasing numbers of HLA loci ( >or=4) was associated with increased IFN-gamma secretion levels (test for trend p-value=0.01). Our results suggest that HLA homozygosity showed no disadvantage for measles-specific cytokine responses and instead was associated with increased IFN-gamma levels.

The immunology of bovine tuberculosis and progression toward improved disease control strategies

Failure to remove cattle diseased with Mycobacterium bovis has immense financial implications for disease control, animal health and agricultural trade as well as the zoonotic risk to human health. Current disease control strategies based on DTH skin testing fail to detect all diseased cattle and additional measures are urgently needed to improve detection of disease and to prevent naïve animals becoming exposed to infection. Experimental models of bovine TB traditionally based on intra-nasal instillation, intra-tracheal inoculation or placed in-contact with infected cattle, have been further developed using aerosolised bacteria delivered to the respiratory tract, allowing field-like bovine TB to be recreated under controlled, experimental conditions. Experimental infection models have already been used to improve diagnostic tests. Specificity of DTH skin testing can be improved under experimental conditions, using recombinant ESAT-6, while laboratory assays such as IFN-gamma release have benefited from the use of defined proteins to improve assay specificity. In combination, antigen cocktails may also improve test sensitivity. There is a concerted international effort to evaluate vaccines for use in cattle populations and to define vaccination strategies which will eliminate disease from infected herds. DNA, protein and genetically modified vaccines inoculated in a single dose, given as prime-boost or injected concurrently, will elicit significant protection against challenge with M. bovis under controlled conditions. However, vaccines and vaccination strategies require evaluation under field conditions. Furthermore, complementary strategies are under development to differentiate immune responses that follow vaccination from those following disease. This paper describes those recent advances which may lead to the introduction of improved disease control strategies.