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Vaccination of cattle with a commercial human tuberculosis (TB) vaccine,Mycobacterium bovisbacillus Calmette-Guérin (BCG) Danish, at a dose equivalent to 5 human doses of BCG has protected these animals against TB in field and experimental trials. There is interest in determining whether a 10-fold-lower dose could still protect cattle but not induce a tuberculin intradermal test response. Two groups of calves (n= 9/group) were vaccinated subcutaneously with a lyophilized BCG Danish vaccine containing either 0.5 (1 × 105to 4 × 105CFU) or 5 (1 × 106to 4 × 106CFU) human doses of BCG Danish, with an additional group of 10 calves serving as nonvaccinated controls. Fifteen weeks after vaccination, these animals were challenged intratracheally with 5 × 103CFU of virulentM. bovisand another 15 weeks later were slaughtered and examined for the presence of tuberculous lesions. Vaccination of the calves with either 0.5 or 5 equivalent human doses of BCG Danish induced similar levels of protection against challenge withM. bovis, with both groups showing significant reductions in the pathological and microbiological parameters compared to those for the the control group (P< 0.05). Vaccination with either of the two BCG doses induced similar numbers of animals responding to the tuberculin intradermal test at 11 weeks postvaccination. Vaccination with a 0.5 equivalent human dose of a commercial lyophilized BCG vaccine can protect cattle against challenge withM. bovis.

T helper 17 (Th17)-associated cytokines are integral to the immune responses to tuberculosis, initiating both protective and harmful inflammatory responses. The aim of the present study was to evaluate applied aspects of interleukin-17 (IL-17) biology in the context of Mycobacterium bovis infection of cattle. Using transcriptome sequencing (RNA-Seq), numerous Th17-associated cytokine genes (including IL-17A, IL-17F, IL-22, IL-19, and IL-27) were upregulated >9-fold in response to purified protein derivative stimulation of peripheral blood mononuclear cells from experimentally M. bovis -infected cattle. Protective vaccines elicited IL-17A, IL-17F, IL-22, and IL-27 responses. Reduced IL-17A responses by vaccine recipients, compared to nonvaccinated animals, at 2.5 weeks after M. bovis challenge correlated with reduced disease burdens. Additionally, IL-17A and interferon gamma (IFN-γ) responses were highly correlated and exhibited similar diagnostic capacities. The present findings support the use of Th17-associated cytokines as biomarkers of infection and protection in the immune responses to bovine tuberculosis.

This is the first efficacy study using the experimental goat model, a natural host of tuberculosis (TB), to evaluate the efficacy of heterologousMycobacterium bovisbacillus Calmette-Guérin (BCG) prime followed by boosting with a replication-deficient adenovirus expressing the antigen Ag85A (AdAg85A). Three experimental groups of 11 goat kids each were used: BCG vaccinated, BCG vaccinated and AdAg85A boosted, and nonvaccinated. Twenty-two goat kids were vaccinated with ∼5 × 105CFU of BCG (week 0), and 11 of them were boosted at week 8 with 109PFU of AdAg85A. At week 14, all goats were challenged by the endobronchial route with ∼1.5 × 103CFU ofMycobacterium caprae. The animals were euthanized at week 28. Cellular and humoral immunity induced by vaccination andM. capraeinfection was measured throughout the study. After challenge BCG-AdAg85A-vaccinated animals exhibited reduced pathology compared to BCG-vaccinated animals in lungs and in pulmonary lymph nodes. There were significant reductions in bacterial load in both groups of vaccinated goats, but the reduction was more pronounced in prime-boosted animals. Antigen-specific gamma interferon (IFN-γ) and humoral responses were identified as prognostic biomarkers of vaccination outcome depending on their correlation with pathological and bacteriological results. As far as we know, this is the first report using multidetector computed tomography (MDCT) to measure vaccine efficacy against pulmonary TB in an animal model. The use in vaccine trials of animals that are natural hosts of TB may improve research into human TB vaccines.

Results of previous studies utilizing bioinformatic approaches in antigen-mining experiments revealed that secreted proteins are among the most frequently recognized antigens fromMycobacterium bovis. Thus, we hypothesized that the analysis of secreted proteins is likely to reveal additional immunogenic antigens that can be used to increase the specificity of diagnostic tests or be suitable vaccination candidates for mycobacterial infections. To test this hypothesis, 382 pools of overlapping peptides spanning 119M. bovissecreted and potentially secreted proteins were screened for the ability to stimulate a gamma interferon responsein vitrousing whole blood from tuberculin-positive reactor (TB reactor) cattle. Of the 119 proteins screened, 70 (59%) induced positive responses in the TB reactor animals to various degrees. Strikingly, all but one of the 15 ESAT-6 proteins tested were recognized by at least 30% of the TB reactor animals, with 12 of the 22 most commonly recognized antigens belonging to this protein family. Further analysis of these data demonstrated that there was no significant difference in immunogenicity between the ESAT-6 proteins that were components of potentially intact ESX secretory systems and those corresponding to additional partialesxloci. Importantly for vaccine design, antigenic epitopes in some highly conserved regions shared by numerous ESAT-6 proteins were identified. However, despite this considerable homology, peptide-mapping experiments also revealed that immunodominant peptides were located in regions of amino acid variability.

Priming neonatal calves at birth with a Mycobacterium bovis bacillus Calmette-Guérin (BCG) vaccine and boosting with a DNA vaccine consisting of plasmids encoding mycobacterial antigens Hsp65, Hsp70, and Apa or the reverse prime-boost sequence induced similar levels of protection against experimental challenge with Mycobacterium bovis . When M. bovis was isolated from a thoracic lymph node following challenge, the two groups of calves given the prime-boost regimen had significantly lower numbers of M. bovis isolates than those vaccinated with BCG alone. These observations suggest that the exact sequence of administration of a prime-boost vaccination regimen in a neonatal animal model is not critical to the development of immunity.

The development of a subunit protein vaccine for bovine tuberculosis which could be used either in combination withMycobacterium bovisBCG (to improve the efficacy of that vaccine) or alone would offer significant advantages over currently available strategies. A study was conducted with cattle to determine the protective efficacy of a strategy based on concurrent immunization with anM. bovisculture filtrate (CFP) vaccine and BCG compared to vaccination with either vaccine alone. One group of calves (10 animals per group) was vaccinated subcutaneously with CFP formulated with Emulsigen and combined with a CpG oligodeoxynucleotide (ODN). A second group was vaccinated with both the CFP vaccine and BCG injected at adjacent sites (CFP-BCG). One further group was vaccinated subcutaneously with BCG, while another group served as nonvaccinated control animals. Vaccination with CFP-BCG induced levels of antigen-specific gamma interferon (IFN-γ) and interleukin-2 (IL-2) in whole-blood cultures that were higher than those induced by vaccination with BCG alone. The combination of CFP and BCG did not enhance the production of antibodies toM. bovisCFP compared to vaccination with CFP alone. Vaccination with CFP alone led to delayed antigen-specific IFN-γ and IL-2 responses. Vaccination with CFP-BCG induced a high level of protection against an intratracheal challenge with virulentM. bovis, based on a significant enhancement of six pathological and microbiological parameters of protection compared with the nonvaccinated group. In contrast, vaccination with BCG alone induced a significant enhancement of protection in only one parameter, while CFP alone induced no protection. These results suggest that a combination of a CpG ODN-formulated protein vaccine and BCG offers better protection against bovine tuberculosis than does BCG alone.

Vaccine development and the understanding of the pathology of bovine tuberculosis in cattle would be greatly facilitated by the definition of immunological correlates of protection and/or pathology. To address these questions, cattle were vaccinated withMycobacterium bovisbacillus Calmette-Guérin (BCG) and were then challenged with virulentM. bovis. Applying a semiquantitative pathology-scoring system, we were able to demonstrate that BCG vaccination imparted significant protection by reducing the disease severity on average by 75%. Analysis of cellular immune responses followingM. bovischallenge demonstrated that proliferative T-cell and gamma interferon (IFN-γ) responses towards theM. bovis-specific antigen ESAT-6, whose gene is absent from BCG, were generally low in vaccinated animals but were high in all nonvaccinated calves. Importantly, the amount of ESAT-6-specific IFN-γ measured by enzyme-linked immunosorbent assay afterM. bovischallenge, but not the frequency of responding cells, correlated positively with the degree of pathology found 18 weeks after infection. Diagnostic reagents based on antigens not present in BCG, like ESAT-6 and CFP-10, were still able to distinguish BCG-vaccinated, diseased animals from BCG-vaccinated animals without signs of disease. In summary, our results suggest that the determination of ESAT-6-specific IFN-γ, while not a direct correlate of protection, constitutes nevertheless a useful prognostic immunological marker predicting both vaccine efficacy and disease severity.

We describe here the application of a novel bovine interleukin-2 (IL-2) enzyme-linked immunosorbent assay (ELISA) for the measurement of antigen-specific IL-2 in cattle naturally infected withMycobacterium bovisand in cattle vaccinated withMycobacterium bovisBCG and then experimentally challenged with pathogenicM. bovis. Supernatants from whole-blood cultures stimulated with mycobacterial antigen (bovine purified protein derivative [PPDB] or the peptide cocktail ESAT6-CFP10) were assessed using a sandwich ELISA consisting of a new recombinant monoclonal fragment capture antibody and a commercially available polyclonal anti-bovine-IL-2. The production of IL-2 was compared to the production of gamma interferon (IFN-γ) in the same antigen-stimulated whole-blood supernatants. The data show that cattle infected withM. bovisproduced quantifiable levels of antigen-specific IL-2, while IL-2 levels in cattle vaccinated withM. bovisBCG did not. Furthermore, cattle vaccinated withM. bovisBCG and then challenged with pathogenicM. bovisdisplayed a more rapid induction of IL-2 but ultimately had lower levels of infection-induced IL-2 than did unvaccinated challenge control cattle. These data suggest that IL-2 responses are not detectable post-BCG vaccination and that these responses may require infection with virulentM. bovisto develop. This may be useful to differentiate infected cattle from uninfected or BCG-vaccinated cattle, although the overall sensitivity is relatively low, particularly in single intradermal comparative cervical tuberculin (SICCT)-negative infected animals. Furthermore, the strength of the IL-2 response may correlate with pathology, which poses interesting questions on the immunobiology of bovine tuberculosis in contrast to human tuberculosis, which is discussed.

Cattle were vaccinated with an adenovirus expressing the mycobacterial antigen 85A (rAd85A), with Mycobacterium bovis BCG followed by rAd85A heterologous boosting, or with rAd85A followed by BCG boosting. BCG/rAd85A resulted in the highest direct gamma interferon responses. Cultured enzyme-linked immunospot assay analysis demonstrated that memory responses were induced by all three protocols but were strongest after BCG/rAd85A and rAd85A/BCG vaccination.

Caprine tuberculosis (TB) has increased in recent years, highlighting the need to address the problem the infection poses in goats. Moreover, goats may represent a cheaper alternative for testing of prototype vaccines in large ruminants and humans. With this aim, a Mycobacterium caprae infection model has been developed in goats. Eleven 6-month-old goats were infected by the endobronchial route with 1.5 × 10 3 CFU, and two other goats were kept as noninfected controls. The animals were monitored for clinical and immunological parameters throughout the experiment. After 14 weeks, the goats were euthanized, and detailed postmortem analysis of lung lesions was performed by multidetector computed tomography (MDCT) and direct observation. The respiratory lymph nodes were also evaluated and cultured for bacteriological analysis. All infected animals were positive in a single intradermal comparative cervical tuberculin (SICCT) test at 12 weeks postinfection (p.i.). Gamma interferon (IFN-γ) antigen-specific responses were detected from 4 weeks p.i. until the end of the experiment. The humoral response to MPB83 was especially strong at 14 weeks p.i. (13 days after SICCT boost). All infected animals presented severe TB lesions in the lungs and associated lymph nodes. M. caprae was recovered from pulmonary lymph nodes in all inoculated goats. MDCT allowed a precise quantitative measure of TB lesions. Lesions in goats induced by M. caprae appeared to be more severe than those induced in cattle by M. bovis over a similar period of time. The present work proposes a reliable new experimental animal model for a better understanding of caprine tuberculosis and future development of vaccine trials in this and other species.

Mycobacterial lipids play an important role in the modulation of the immune response upon contact with the host. Using novel methods, we have isolated highly purified phosphatidylinositol mannoside (PIM) molecules (phosphatidylinositol dimannoside [PIM2], acylphosphatidylinositol dimannoside [AcPIM2], diacyl-phosphatidylinositol dimannoside [Ac2PIM2], acylphosphatidylinositol hexamannoside [AcPIM6], and diacylphosphatidylinositol hexamannoside [Ac2PIM6]) from virulent Mycobacterium tuberculosis to assess their potential to stimulate peripheral blood mononuclear cell (PBMC) responses in Mycobacterium bovis-infected cattle. Of these molecules, one (AcPIM6) induced significant levels of gamma interferon (IFN-γ) in bovine PBMCs. Three PIM molecules (AcPIM6, Ac2PIM2, and Ac2PIM6) were shown to drive significant proliferation in bovine PBMCs. AcPIM6 was subsequently used to phenotype the proliferating cells by flow cytometry. This analysis demonstrated that AcPIM6 was predominantly recognized by CD3(+) CD335(+) NKT cells. In conclusion, we have identified PIM lipid molecules that interact with bovine lymphocyte populations, and these lipids may be useful as future subunit vaccines or diagnostic reagents. Further, these data demonstrate, for the first time, lipid-specific NKT activation in cattle.

The aim of this work was to determine the minimum infective dose of Mycobacterium bovis necessary to stimulate specific immune responses and generate pathology in cattle. Four groups of calves (20 animals) were infected by the intratracheal route with 1,000, 100, 10, or 1 CFU of M. bovis . Specific immune responses (gamma interferon [IFN-γ] and interleukin-4 [IL-4] responses) to mycobacterial antigens were monitored throughout the study, and the responses to the tuberculin skin test were assessed at two times. Rigorous post mortem examinations were performed to determine the presence of pathology, and samples were taken for microbiological and histopathological confirmation of M. bovis infection. One-half of the animals infected with 1 CFU of M. bovis developed pulmonary pathology typical of bovine tuberculosis. No differences in the severity of pathology were observed for the different M. bovis doses. All animals that developed pathology were skin test positive and produced specific IFN-γ and IL-4 responses. No differences in the sizes of the skin test reactions, the times taken to achieve a positive IFN-γ result, or the levels of the IFN-γ and IL-4 responses were observed for the different M. bovis doses, suggesting that diagnostic assays (tuberculin skin test and IFN-γ test) can detect cattle soon after M. bovis infection regardless of the dose. This information should be useful in modeling the dynamics of bovine tuberculosis in cattle and in assessing the risk of transmission.

Mycobacterium tuberculosis is a significant threat to global health. Mycobacterium bovis BCG vaccine provides only partial protection, and the skin test reagent used to aid diagnosis of both active and latent tuberculosis, purified protein derivative (PPD), lacks specificity and sensitivity. The use of genetically detoxified Bordetella pertussis adenylate cyclase toxin (CyaA) as a delivery system for two immunodominant proteins of M. tuberculosis that are of greater specificity than PPD, early-secreted antigenic target 6-kDa protein (ESAT-6) and culture filtrate protein 10 (CFP-10), was therefore investigated. CyaA toxoids incorporating these antigens were able to restimulate T cells from more than 91% tuberculosis patients and healthy sensitized donors. Delivery of antigen by CyaA decreased by 10-fold the amount of ESAT-6 and CFP-10 required to restimulate T cells, and in low responders, the overall frequency of gamma interferon-producing cells detected by enzyme-linked immunospot assay was increased ( P < 0.01 for both antigens). Delivery of ESAT-6 and CFP-10 by CyaA enabled the detection of both CD4 + and CD8 + T cells: these responses could be blocked by inhibition of major histocompatibility complex class II or class I, respectively. Covalent linkage of antigen to the CyaA vector was required for enhancement to occur, as a mixture of mock CyaA toxoid plus recombinant ESAT-6 did not lead to enhancement. In a simplified whole-blood model to detect tuberculosis infection, the frequency of positive responses to CFP-10 was increased by CyaA delivery, a potentially important attribute that could facilitate the identification of latent infection.

Leprosy research has predominantly been concerned with the dichotomy between immunological events in tuberculoid leprosy and lepromatous leprosy. Thus, distinct cytokine-secreting profiles have been reported for cloned CD4 and CD8 T cells (30), and lepromatous leprosy patients were found to respond to some purified antigens while remaining anergic to whole mycobacterial extracts (21, 26, 34). Analysis of the specificity of “split anergy” at the level of individual antigenic determinants showed skewing of T-cell responses toward Mycobacterium tuberculosis-specific epitopes, accompanied by relative anergy to the cross-reactive common mycobacterial peptides (13). However, consistent differences in either the specificities or phenotypes of T cells between the sensitized healthy contacts and tuberculoid leprosy patients have so far not been revealed. Previous studies of HLA associations reported the association of tuberculoid leprosy with DR2 in India (18, 37), Japan (11, 23), Thailand (31), and Korea (16); with DR3 in Venezuela and Surinam (36); or with DQ1 (11, 23, 31). On the basis of molecular modelling, the presence of arginine (R) and absence of negatively charged amino acids at positions 13 or 70–71 in pocket 4 of the DRB1 alleles (e.g., DR15) has been associated with susceptibility to tuberculoid leprosy (40), but the molecular source of the corresponding peptide specificity has not been identified. Proteins with a molecular mass of 10 to 12 kDa from Mycobacterium leprae (10) and M. tuberculosis (22) were originally found to carry separate species-specific epitopes identified with monoclonal antibodies. Their sequence analysis showed 90% identity between M. leprae and M. tuberculosis and 44% homology with the GroES heat shock protein of Escherichia coli (1, 20, 33), and the protein was localized to the cell wall and cytosol of M. leprae (29). The protein induced strong DTH and Th1 cytokine production, and limiting cell dilution analysis showed a high frequency of responding T cells from blood or from lepromin-induced Mitsuda reactions (17, 19, 35), but it also reacted with human “suppressor” T-cell clones (27) and was reported either to suppress (32) or to induce (9) DTH responses in lepromatous leprosy patients. This study was performed at the level of individual peptide determinants, with additional emphasis on the analysis of HLA class II genetic associations. Using a comprehensive set of GroES peptides of the M. leprae and M. tuberculosis sequences, the aim of this study has been to identify any differences in the proliferation of blood mononuclear cells between paucibacillary or multibacillary leprosy patients and healthy leprosy contacts or medical staff in Thailand. Possible HLA associations were ascertained on the basis of typing for HLA-DR and -DQ alleles and by peptide binding to purified DR molecules.