Intranasal boosting with an adenovirus-vectored vaccine markedly enhances protection by parenteral Mycobacterium bovis BCG immunization against pulmonary tuberculosis

Recombinant Salmonella Expressing Burkholderia mallei LPS O Antigen Provides Protection in a Murine Model of Melioidosis and Glanders

Burkholderia pseudomallei and Burkholderia mallei are the etiologic agents of melioidosis and glanders, respectively. These bacteria are highly infectious via the respiratory route and can cause severe and often fatal diseases in humans and animals. Both species are considered potential agents of biological warfare; they are classified as category B priority pathogens. Currently there are no human or veterinary vaccines available against these pathogens. Consequently efforts are directed towards the development of an efficacious and safe vaccine. Lipopolysaccharide (LPS) is an immunodominant antigen and potent stimulator of host immune responses. B. mallei express LPS that is structurally similar to that expressed by B. pseudomallei, suggesting the possibility of constructing a single protective vaccine against melioidosis and glanders. Previous studies of others have shown that antibodies against B. mallei or B. pseudomallei LPS partially protect mice against subsequent lethal virulent Burkholderia challenge. In this study, we evaluated the protective efficacy of recombinant Salmonella enterica serovar Typhimurium SL3261 expressing B. mallei O antigen against lethal intranasal infection with Burkholderia thailandensis, a surrogate for biothreat Burkholderia spp. in a murine model that mimics melioidosis and glanders. All vaccine-immunized mice developed a specific antibody response to B. mallei and B. pseudomallei O antigen and to B. thailandensis and were significantly protected against challenge with a lethal dose of B. thailandensis. These results suggest that live-attenuated SL3261 expressing B. mallei O antigen is a promising platform for developing a safe and effective vaccine.

Age at Mycobacterium bovis BCG Priming Has Limited Impact on Anti-Tuberculosis Immunity Boosted by Respiratory Mucosal AdHu5Ag85A Immunization in a Murine Model

Tuberculosis (TB) remains a global pandemic despite the use of Bacillus Calmette-Guérin (BCG) vaccine, partly because BCG fails to effectively control adult pulmonary TB. The introduction of novel boost vaccines such as the human Adenovirus 5-vectored AdHu5Ag85A could improve and prolong the protective immunity of BCG immunization. Age at which BCG immunization is implemented varies greatly worldwide, and research is ongoing to discover the optimal stage during childhood to administer the vaccine, as well as when to boost the immune response with potential novel vaccines. Using a murine model of subcutaneous BCG immunization followed by intranasal AdHu5Ag85A boosting, we investigated the impact of age at BCG immunization on protective efficacy of BCG prime and AdHu5Ag85A boost immunization-mediated protection. Our results showed that age at parenteral BCG priming has limited impact on the efficacy of BCG prime-AdHu5Ag85A respiratory mucosal boost immunization-enhanced protection. However, when BCG immunization was delayed until the maturity of the immune system, longer sustained memory T cells were generated and resulted in enhanced boosting effect on T cells of AdHu5Ag85A respiratory mucosal immunization. Our findings hold implications for the design of new TB immunization protocols for humans.

Prime-boost vaccination with Bacillus Calmette Guerin and a recombinant adenovirus co-expressing CFP10, ESAT6, Ag85A and Ag85B of Mycobacterium tuberculosis induces robust antigen-specific immune responses in mice

Tuberculosis (TB) remains to be a prevalent health issue worldwide. At present, Mycobacterium bovis Bacillus Calmette Guerin (BCG) is the singular anti-TB vaccine available for the prevention of disease in humans; however, this vaccine only provides limited protection against Mycobacterium tuberculosis (Mtb) infection. Therefore, the development of alternative vaccines and strategies for increasing the efficacy of vaccination against TB are urgently required. The present study aimed to evaluate the ability of a recombinant adenoviral vector (Ad5-CEAB) co-expressing 10-kDa culture filtrate protein, 6-kDa early-secreted antigenic target, antigen 85 (Ag85)A and Ag85B of Mtb to boost immune responses following primary vaccination with BCG in mice. The mice were first subcutaneously primed with BCG and boosted with two doses of Ad5-CEAB via an intranasal route. The immunological effects of Ad5-CEAB boosted mice primed with BCG were then evaluated using a series of immunological indexes. The results demonstrated that the prime-boost strategy induced a potent antigen-specific immune response, which was primarily characterized by an enhanced T cell response and increased production of cytokines, including interferon-γ, tumor necrosis factor-α and interleukin-2, in mice. In addition, this vaccination strategy was demonstrated to have an elevated humoral response with increased concentrations of antigen-specific bronchoalveolar lavage secretory immunoglobulin (Ig)A and serum IgG in mice compared with those primed with BCG alone. These data suggested that the regimen of subcutaneous BCG prime and mucosal Ad5-CEAB boost was a novel strategy for inducing a broad range of antigen-specific immune responses to Mtb antigens in vivo, which may provide a promising strategy for further development of adenoviral-based vaccine against Mtb infection.

Aerosol immunisation for TB: matching route of vaccination to route of infection

TB remains a very significant global health burden. There is an urgent need for better tools for TB control, which include an effective vaccine. Bacillus Calmette-Guérin (BCG), the currently licensed vaccine, confers highly variable protection against pulmonary TB, the main source of TB transmission. Replacing BCG completely or boosting BCG with another vaccine are the two current strategies for TB vaccine development. Delivering a vaccine by aerosol represents a way to match the route of vaccination to the route of infection. This route of immunisation offers not only the scientific advantage of delivering the vaccine directly to the respiratory mucosa, but also practical and logistical advantages. This review summarises the state of current TB vaccine candidates in the pipeline, reviews current progress in aerosol administration of vaccines in general and evaluates the potential for TB vaccine candidates to be administered by the aerosol route.

Plant-derived recombinant immune complexes as self-adjuvanting TB immunogens for mucosal boosting of BCG

Progress with protein-based tuberculosis (TB) vaccines has been limited by poor availability of adjuvants suitable for human application. Here, we developed and tested a novel approach to molecular engineering of adjuvanticity that circumvents the need for exogenous adjuvants. Thus, we generated and expressed in transgenic tobacco plants the recombinant immune complexes (RICs) incorporating the early secreted Ag85B and the latency-associated Acr antigen of Mycobacterium tuberculosis, genetically fused as a single polypeptide to the heavy chain of a monoclonal antibody to Acr. The RICs were formed by virtue of the antibody binding to Acr from adjacent molecules, thus allowing self-polymerization of the complexes. TB-RICs were purified from the plant extracts and shown to be biologically active by demonstrating that they could bind to C1q component of the complement and also to the surface of antigen-presenting cells. Mice immunized with BCG and then boosted with two intranasal immunizations with TB-RICs developed antigen-specific serum IgG antibody responses with mean end-point titres of 1 : 8100 (Acr) and 1 : 24 300 (Ag85B) and their splenocytes responded to in vitro stimulation by producing interferon gamma. 25% of CD4+ proliferating cells simultaneously produced IFN-γ, IL-2 and TNF-α, a phenotype that has been linked with protective immune responses in TB. Importantly, mucosal boosting of BCG-immunized mice with TB-RICs led to a reduced M. tuberculosis infection in their lungs from log10 mean = 5.69 ± 0.1 to 5.04 ± 0.2, which was statistically significant. We therefore propose that the plant-expressed TB-RICs represent a novel molecular platform for developing self-adjuvanting mucosal vaccines.

Safety and immunogenicity of a candidate tuberculosis vaccine MVA85A delivered by aerosol in BCG-vaccinated healthy adults: a phase 1, double-blind, randomised controlled trial

Background

Intradermal MVA85A, a candidate vaccine against tuberculosis, induces high amounts of Ag85A-specific CD4 T cells in adults who have already received the BCG vaccine, but aerosol delivery of this vaccine might offer immunological and logistical advantages. We did a phase 1 double-blind trial to compare the safety and immunogenicity of aerosol-administered and intradermally administered MVA85A

Methods

In this phase 1, double-blind, proof-of-concept trial, 24 eligible BCG-vaccinated healthy UK adults were randomly allocated (1:1) by sequentially numbered, sealed, opaque envelopes into two groups: aerosol MVA85A and intradermal saline placebo or intradermal MVA85A and aerosol saline placebo. Participants, the bronchoscopist, and immunologists were masked to treatment assignment. The primary outcome was safety, assessed by the frequency and severity of vaccine-related local and systemic adverse events. The secondary outcome was immunogenicity assessed with laboratory markers of cell-mediated immunity in blood and bronchoalveolar lavage samples. Safety and immunogenicity were assessed for 24 weeks after vaccination. Immunogenicity to both insert Ag85A and vector modified vaccinia virus Ankara (MVA) was assessed by ex-vivo interferon-γ ELISpot and serum ELISAs. Since all participants were randomised and vaccinated according to protocol, our analyses were per protocol. This trial is registered with ClinicalTrials.gov, number NCT01497769.

Findings

Both administration routes were well tolerated and immunogenic. Respiratory adverse events were rare and mild. Intradermal MVA85A was associated with expected mild local injection-site reactions. Systemic adverse events did not differ significantly between the two groups. Three participants in each group had no vaccine-related systemic adverse events; fatigue (11/24 [46%]) and headache (10/24 [42%]) were the most frequently reported symptoms. Ag85A-specific systemic responses were similar across groups. Ag85A-specific CD4 T cells were detected in bronchoalveolar lavage cells from both groups and responses were higher in the aerosol group than in the intradermal group. MVA-specific cellular responses were detected in both groups, whereas serum antibodies to MVA were only detectable after intradermal administration of the vaccine.

Interpretation

Further clinical trials assessing the aerosol route of vaccine delivery are merited for tuberculosis and other respiratory pathogens.

Funding

The Wellcome Trust and Oxford Radcliffe Hospitals Biomedical Research Centre.

A novel murine cytomegalovirus vaccine vector protects against Mycobacterium tuberculosis

Tuberculosis remains a global health problem so that a more effective vaccine than bacillus Calmette–Guérin is urgently needed. Cytomegaloviruses persist lifelong in vivo and induce powerful immune and increasing (“inflationary”) responses, making them attractive vaccine vectors. We have used an m1–m16-deleted recombinant murine CMV (MCMV) expressing Mycobacterium tuberculosis Ag 85A to show that infection of mice with this recombinant significantly reduces the mycobacterial load after challenge with M. tuberculosis, whereas control empty virus has a lesser effect. Both viruses induce immune responses to H-2^d–restricted epitopes of MCMV pp89 and M18 Ags characteristic of infection with other MCMVs. A low frequency of 85A-specific memory cells could be revealed by in vivo or in vitro boosting or after challenge with M. tuberculosis. Kinetic analysis of M. tuberculosis growth in the lungs of CMV-infected mice shows early inhibition of M. tuberculosis growth abolished by treatment with NK-depleting anti–asialo ganglio-N-tetraosylceramide Ab. Microarray analysis of the lungs of naive and CMV-infected mice shows increased IL-21 mRNA in infected mice, whereas in vitro NK assays indicate increased levels of NK activity. These data indicate that activation of NK cells by MCMV provides early nonspecific protection against M. tuberculosis, potentiated by a weak 85A-specific T cell response, and they reinforce the view that the innate immune system plays an important role in both natural and vaccine-induced protection against M. tuberculosis.

Aerosol vaccination with AERAS-402 elicits robust cellular immune responses in the lungs of rhesus macaques but fails to protect against high-dose Mycobacterium tuberculosis challenge

Development of a vaccine against pulmonary tuberculosis may require immunization strategies that induce a high frequency of Ag-specific CD4 and CD8 T cells in the lung. The nonhuman primate model is essential for testing such approaches because it has predictive value for how vaccines elicit responses in humans. In this study, we used an aerosol vaccination strategy to administer AERAS-402, a replication-defective recombinant adenovirus (rAd) type 35 expressing Mycobacterium tuberculosis Ags Ag85A, Ag85B, and TB10.4, in bacillus Calmette-Guérin (BCG)-primed or unprimed rhesus macaques. Immunization with BCG generated low purified protein derivative-specific CD4 T cell responses in blood and bronchoalveolar lavage. In contrast, aerosolized AERAS-402 alone or following BCG induced potent and stable Ag85A/b-specific CD4 and CD8 effector T cells in bronchoalveolar lavage that largely produced IFN-γ, as well as TNF and IL-2. Such responses induced by BCG, AERAS-402, or both failed to confer overall protection following challenge with 275 CFUs M. tuberculosis Erdman, although vaccine-induced responses associated with reduced pathology were observed in some animals. Anamnestic T cell responses to Ag85A/b were not detected in blood of immunized animals after challenge. Overall, our data suggest that a high M. tuberculosis challenge dose may be a critical factor in limiting vaccine efficacy in this model. However, the ability of aerosol rAd immunization to generate potent cellular immunity in the lung suggests that using different or more immunogens, alternative rAd serotypes with enhanced immunogenicity, and a physiological challenge dose may achieve protection against M. tuberculosis.

Recent developments in tuberculosis vaccines

Substantial efforts have been made over the past decade to develop vaccines against tuberculosis. We review recent developments in tuberculosis vaccines in the global portfolio, including those designed for use in a prophylactic setting, either alone or as boosts to Bacille Calmette-Guérin, and therapeutic vaccines designed to improve chemotherapy. While there is no doubt that progress is still being made, there are limitations to our animal model screening processes, which are further amplified by the lack of understanding of the immunological responses involved and the precise type of long-lived immunity that new vaccines need to induce. The challenge ahead is to optimize the planning for advanced clinical trials in poor endemic settings, which could be greatly facilitated by identifying correlates of protection.

A Mycobacterium bovis BCG-naked DNA prime-boost vaccination strategy induced CD4⁺ and CD8⁺ T-cell response against Mycobacterium tuberculosis immunogens

Mycobacterium tuberculosis infection is still a major global public health problem. Presently the only tuberculosis (TB) vaccine available is Bacille Calmette-Guérin (BCG), although it fails to adequately protect against pulmonary TB in adults. To solve this problem, the development of a new effective vaccine is urgently desired. BCG-prime DNA-booster vaccinations strategy has been shown to induce greater protection against tuberculosis (TB) than BCG alone. Some studies have demonstrated that the two genes (Rv1769 and Rv1772) are excellent T-cell antigens and could induce T-cell immune responses. In this research, we built BCG-C or BCG-P prime-recombination plasmid PcDNA3.1-Rv1769 or PcDNA3.1-Rv1772 boost vaccinations strategy to immunize BALB/c mice and evaluated its immunogenicity. The data suggests that the BCG-C+3.1-72 strategy could elicit the most long-lasting and strongest Th1-type cellular immune responses and the BCG-C+3.1-69 strategy could induce the high level CD8+ T-cell response at certain time points. These findings support the ideas that the prime-boost strategy as a combination of vaccines may be better than a single vaccine for protection against tuberculosis.

Effect of dose and route of immunisation on the immune response induced in cattle by heterologous Bacille Calmette-Guerin priming and recombinant adenoviral vector boosting

BCG is used experimentally as a vaccine against tuberculosis (TB), induced by Mycobacterium bovis, in cattle (bTB). However, the efficacy of BCG is variable in humans, cattle and guinea pigs. An adenoviral vector expressing Antigen 85A (Ad5Ag85A) has enhanced protection against TB in mice when used in combination with BCG for prime-boost experiments. However, the route of immunisation affects the degree of protection seen. This work examines the immunogenicity of a new vectored vaccine (Ad5-TBF) that expresses Ag85A, Rv0287, Rv0288 and Rv0251c to explore the effects of dose of adenoviral boost and route of inoculation on immunogenicity. We found that 2×10(9) infectious units (iu) delivered intradermally conferred the most consistent and strongest responses of the different regimes tested.

Vaccine against tuberculosis: what's new?

Background

one of the World Health Organization Millennium Development Goal is to reduce tuberculosis incidence by 2015. However, more of 8.5 million tuberculosis cases have been reported in 2011, with an increase of multidrug-resistant strains. Therefore, the World Health Organization target cannot be reach without the help of a vaccine able to limit the spread of tuberculosis. Nowadays, bacille Calmette-Guérin is the only vaccine available against tuberculosis. It prevents against meningeal and disseminated tuberculosis in children, but its effectiveness against pulmonary form in adolescents and adults is argued.

Method

a systematic review was performed by searches of Pubmed, references of the relevant articles and Aeras and ClinicalTrial.gov websites.

Results

100 articles were included in this review. Three viral vectored booster vaccines, five protein adjuvant booster vaccines, two priming vaccines and two therapeutic vaccines have been analyzed.

Conclusions

Several vaccines are in the pipeline, but further studies on basic research, clinical trial and mass vaccination campaigns are needed to achieve the TB eradication target by 2050.

Harnessing local and systemic immunity for vaccines against tuberculosis

The lung is the portal of entry for Mycobacterium tuberculosis (Mtb) and animal experimental evidence indicates that local immune defense mechanisms are crucial for protective immunity. Immunization via the lower respiratory tract efficiently induces a dividing, activated, antigen-dependent, lung-resident, memory T-cell population, which is partly recoverable by bronchoalveolar lavage. These cells can inhibit the growth of Mtb in the lungs immediately after infection. Delivery of appropriate signals to the lung innate immune system is critical for induction of effective local immunity. In contrast after parenteral immunization, antigen-specific cells may be found in lung tissue but few are recoverable by lavage and inhibition of mycobacterial growth is delayed. Harnessing both local and systemic immunity can provide highly effective protection in animal models and the evidence suggests that taken in aggregate, multiple animal models may predict the success of novel vaccine strategies in humans.

A multi-antigenic adenoviral-vectored vaccine improves BCG-induced protection of goats against pulmonary tuberculosis infection and prevents disease progression

The “One world, one health” initiative emphasizes the need for new strategies to control human and animal tuberculosis (TB) based on their shared interface. A good example would be the development of novel universal vaccines against Mycobacterium tuberculosis complex (MTBC) infection. This study uses the goat model, a natural TB host, to assess the protective effectiveness of a new vaccine candidate in combination with Bacillus Calmette-Guerin (BCG) vaccine.

Thirty-three goat kids were divided in three groups: Group 1) vaccinated with BCG (week 0), Group 2) vaccinated with BCG and boosted 8 weeks later with a recombinant adenovirus expressing the MTBC antigens Ag85A, TB10.4, TB9.8 and Acr2 (AdTBF), and Group 3) unvaccinated controls. Later on, an endobronchial challenge with a low dose of M. caprae was performed (week 15). After necropsy (week 28), the pulmonary gross pathology was quantified using high resolution Computed Tomography. Small granulomatous pulmonary lesions (< 0.5 cm diameter) were also evaluated through a comprehensive qualitative histopathological analysis. M. caprae CFU were counted from pulmonary lymph nodes.

The AdTBF improved the effects of BCG reducing gross lesion volume and bacterial load, as well as increasing weight gain. The number of Ag85A-specific gamma interferon-producing memory T-cells was identified as a predictor of vaccine efficacy. Specific cellular and humoral responses were measured throughout the 13-week post-challenge period, and correlated with the severity of lesions.

Unvaccinated goats exhibited the typical pathological features of active TB in humans and domestic ruminants, while vaccinated goats showed only very small lesions. The data presented in this study indicate that multi-antigenic adenoviral vectored vaccines boosts protection conferred by vaccination with BCG.

Protection against tuberculosis with homologous or heterologous protein/vector vaccine approaches is not dependent on CD8+ T cells

Considerable effort has been directed to develop Mycobacterium tuberculosis vaccines to boost bacille Calmette-Guérin or for those who cannot be immunized with bacille Calmette-Guérin. We hypothesized that CD4(+) and CD8(+) T cell responses with a heterologous prime/boost vaccine approach could induce long-lived vaccine efficacy against M. tuberculosis in C57BL/6 mice. We produced an adenovirus vector expressing ID93 (Ad5-ID93) for induction of CD8 T cells to use with our candidate tuberculosis vaccine, ID93/glucopyranosyl lipid adjuvant (GLA)-stable emulsion (SE), which induces potent Th1 CD4 T cells. Ad5-ID93 generates ID93-specific CD8(+) T cell responses and induces protection against M. tuberculosis. When Ad5-ID93 is administered in a prime-boost strategy with ID93/GLA-SE, both CD4(+) and CD8(+) T cells are generated and provide protection against M. tuberculosis. In a MHC class I-deficient mouse model, all groups including the Ad5-ID93 group elicited an Ag-specific CD4(+) T cell response and significantly fewer Ag-specific CD8(+) T cells, but were still protected against M. tuberculosis, suggesting that CD4(+) Th1 T cells could compensate for the loss of CD8(+) T cells. Lastly, the order of the heterologous immunizations was critical. Long-lived vaccine protection was observed only when Ad5-ID93 was given as the boost following an ID93/GLA-SE prime. The homologous ID93/GLA-SE prime/boost regimen also induced long-lived protection. One of the correlates of protection between these two approaches was an increase in the total number of ID93-specific IFN-γ-producing CD4(+) T cells 6 mo following the last immunization. Our findings provide insight into the development of vaccines not only for tuberculosis, but other diseases requiring T cell immunity.

Differentially imprinted innate immunity by mucosal boost vaccination determines antituberculosis immune protective outcomes, independent of T-cell immunity

Homologous and heterologous parenteral prime-mucosal boost immunizations have shown great promise in combating mucosal infections such as tuberculosis and AIDS. However, their immune mechanisms remain poorly defined. In particular, it is still unclear whether T-cell and innate immunity may be independently affected by these immunization modalities and how it impacts immune protective outcome. Using two virus-based tuberculosis vaccines (adenovirus (Ad) and vesicular stomatitis virus (VSV) vectors), we found that while both homologous (Ad/Ad) and heterologous (Ad/VSV) respiratory mucosal boost immunizations elicited similar T-cell responses in the lung, they led to drastically different immune protective outcomes. Compared with Ad-based boosting, VSV-based boosting resulted in poorly enhanced protection against tuberculosis. Such inferior protection was associated with differentially imprinted innate phagocytes, particularly the CD11c(+)CD11b(+/-) cells, in the lung. We identified heightened type 1 interferon (IFN) responses to be the triggering mechanism. Thus, increased IFN-β severely blunted interleukin-12 responses in infected phagocytes, which in turn impaired their nitric oxide production and antimycobacterial activities. Our study reveals that vaccine vectors may differentially imprint innate cells at the mucosal site of immunization, which can impact immune-protective outcome, independent of T-cell immunity, and it is of importance to determine both T-cell and innate cell immunity in vaccine studies.

Prime-boost approaches to tuberculosis vaccine development

Four individuals die from active TB disease each minute, while at least 2 billion are latently infected and at risk for disease reactivation. BCG, the only licensed TB vaccine, is effective in preventing childhood forms of TB; however its poor efficacy in adults, emerging drug-resistant TB strains and tedious chemotherapy regimes, warrant the development of novel prophylactic measures. Designing safe and effective vaccines against TB will require novel approaches on several levels, including the administration of rationally selected mycobacterial antigens in efficient delivery vehicles via optimal immunization routes. Given the primary site of disease manifestation in the lungs, development of mucosal immunization strategies to generate protective immune responses both locally, and in the circulation, may be important for effective TB prophylaxis. This review focuses on prime-boost immunization strategies currently under investigation and highlights the potential of mucosal delivery and rational vaccine design based on systems biology.

Optimising immunogenicity with viral vectors: mixing MVA and HAdV-5 expressing the mycobacterial antigen Ag85A in a single injection

The Bacillus Calmette - Guerin (BCG) vaccine provides a critical but limited defense against Mycobacterium tuberculosis (M.tb). More than 60 years after the widespread introduction of BCG, there is an urgent need for a better vaccine. A large body of pre-clinical research continues to support ongoing clinical trials to assess whether viral vectors expressing M.tb antigens that are shared by BCG and M.tb, can be used alongside BCG to enhance protection. A major focus involves using multiple unique viral vectors to limit anti-vector immunity and thereby enhance responses to the insert antigen delivered. The successful introduction of viral vector vaccines to target M.tb and other pathogens will be reliant on reducing the costs when using multiple vectors and inhibiting the development of unwanted anti-vector responses that interfere with the response to insert antigen. This study examines methods to reduce the logistical costs of vaccination by mixing different viral vectors that share the same insert antigen in one vaccine; and whether combining different viral vectors reduces anti-vector immunity to improve immunogenicity to the insert antigen. Here we show that a homologous prime-boost regimen with a mixture of MVA (Modified Vaccinia virus Ankara) and Ad5 (human adenovirus type 5) vectors both expressing Ag85A in a single vaccine preparation is able to reduce anti-vector immunity, compared with a homologous prime-boost regimen with either vector alone. However, the level of immunogenicity induced by the homologous mixture remained comparable to that induced with single viral vectors and was less immunogenic than a heterologous Ad5 prime-MVA-boost regimen. These findings advance the understanding of how anti-vector immunity maybe reduced in viral vector vaccination regimens. Furthermore, an insight is provided to the impact on vaccine immunogenicity from altering vaccination methods to reduce the logistical demands of using separate vaccine preparations in the field.

Vaccination against tuberculosis: how can we better BCG?

Tuberculosis remains one of the most significant human diseases of the developing world, accounting for 3800 worldwide deaths per day. Although we currently have a vaccine for tuberculosis, BCG, this is insufficient at protecting from adult pulmonary tuberculosis in the parts of the world where a good vaccine is most needed. This has prompted the search for new vaccination strategies that can protect better than BCG, or can boost BCG-induced immunity. We discuss these subjects in line with what is known of the immune responses to BCG and Mycobacterium tuberculosis - the etiological agent of the disease, as well as the particular difficulties facing development of new vaccines against tuberculosis. A greater understanding of the factors constituting optimal protection against Mycobacterium tuberculosis infection, as well as which pathogenic factors facilitate active disease, will accelerate the delivery of safe vaccines able to restrict active tuberculosis and thus impede contagion.

Lipidated promiscuous peptides vaccine for tuberculosis-endemic regions

Despite nine decades of Bacillus Calmette--Guérin (BCG) vaccination, tuberculosis continues to be a major global health challenge. Clinical trials worldwide have proved the inadequacy of the BCG vaccine in preventing the manifestation of pulmonary tuberculosis in adults. Ironically, the efficacy of BCG is poorest in tuberculosis endemic areas. Factors such as nontuberculous or environmental mycobacteria and helminth infestation have been suggested to limit the efficacy of BCG. Hence, in high TB-burden countries, radically novel strategies of vaccination are urgently required. Here we showcase the properties of lipidated promiscuous peptide vaccines that target and activate cells of the innate and adaptive immune systems by employing a Toll-like receptor-2 agonist, S-[2,3-bis(palmitoyloxy)propyl]cysteine (Pam2Cys). Such a strategy elicits robust protection and enduring memory responses by type 1 T helper cells (Th1). Consequently, lipidated peptides may yield a better vaccine than BCG.

Immunogenicity and protective efficacy of heterologous prime-boost regimens with mycobacterial vaccines and recombinant adenovirus- and poxvirus-vectored vaccines against murine tuberculosis

OBJECTIVES

To evaluate regimens using bacillus Calmette-Guérin (BCG) or recombinant BCG (rBCG) overexpressing Ag85B for priming, followed by boosting with a modified vaccinia virus Ankara strain (MVA) and/or adenovirus vector (AD) expressing an Ag85B-ESAT6 fusion protein.

METHODS

Cellular and humoral immune responses were determined after subcutaneous vaccination, which was employed to trigger systemic immunity against intravenous infection in a mouse model of tuberculosis (TB). Bacterial loads and lung histology were evaluated.

RESULTS

The relative IgG2a and IgG1 antibody levels indicated that the viral-vectored vaccines generated a T-helper type 1 (Th1)-biased response after two doses of viral boost vaccinations. Boosting BCG-primed mice with viral vaccines induced a Th1 immune response that included both CD4 and CD8 T-cells generating antigen-specific interferon-gamma (IFN-γ) and CD8 T cytotoxic activity. Only mice vaccinated with two different viral boosters after BCG priming exhibited a significant reduction in bacterial burden in the lung after challenge. Histology examinations confirmed the attenuation of lung damage and more compact granulomas. After mycobacteria priming, boosting with AD85B-E6 followed by MVA85B-E6 afforded better protection than the reverse order of administration of the viral vectors.

CONCLUSIONS

This study demonstrates the potential of multiple heterologous viral booster vaccines, although the exact correlates of protection and optimal regimens should be further investigated for the rational design of future vaccine strategies.

Immunogenicity comparison of the intradermal or endobronchial boosting of BCG vaccinates with Ad5-85A

Experiments in small animal models have indicated that intranasal vaccination confers a greater degree of protection against TB than other routes such as intradermal (i.d.) or intramuscular. In this work, using a prime-boost vaccination strategy, we have compared in cattle vaccinated with BCG as a priming vaccine the boosting capabilities of Ad5-85A delivered either via the endobronchial (e.b.) or i.d. route. We show that Ad5-85A delivered through either route induced comparable peripheral blood antigen specific responses, and that both i.d. and e.b. routes induced bronchioalveolar lavage cells (BALC) that produced antigen-specific IFNgamma. We also show that, regardless of the route of boosting, the kinetics of peripheral blood and BALC responses, as assessed by antigen specific IFNgamma production, are different with systemic responses being detectable earlier than mucosal responses. These results contribute to our understanding on how different vaccination strategies may affect different compartments of the immune response and in turn to the development of safer and more effective vaccines.

Goats primed with Mycobacterium bovis BCG and boosted with a recombinant adenovirus expressing Ag85A show enhanced protection against tuberculosis

This is the first efficacy study using the experimental goat model, a natural host of tuberculosis (TB), to evaluate the efficacy of heterologous Mycobacterium bovis bacillus 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 × 10(5) CFU of BCG (week 0), and 11 of them were boosted at week 8 with 10(9) PFU of AdAg85A. At week 14, all goats were challenged by the endobronchial route with ∼1.5 × 10(3) CFU of Mycobacterium caprae. The animals were euthanized at week 28. Cellular and humoral immunity induced by vaccination and M. caprae infection 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.

Tuberculosis vaccine development: strength lies in tenacity

The past decade has witnessed a tremendous increase in the development of novel vaccines against tuberculosis (TB). In mice, each of these vaccine candidates stimulates an immune response that reduces the bacillary load, reflecting control but not sterilization of infection. Yet, the immune mechanisms underlying vaccine efficacy are only partially understood. In parallel to clinical assessment of current candidates, the next generation of vaccine candidates still needs to be developed. This requires basic research on how to induce the most efficacious immune response. Equally important is the dissection of immune responses in patients, latently infected healthy individuals, and participants of clinical vaccine trials. Amalgamation of this information will foster the way towards more efficacious vaccination strategies that not only prevent disease, but prevent or abolish infection.

Robust immune response elicited by a novel and unique Mycobacterium tuberculosis protein using an optimized DNA/protein heterologous prime/boost protocol

An efficacious tuberculosis (TB) vaccine will probably need to induce both CD4 and CD8 T-cell responses specific to a protective Mycobacterium tuberculosis antigen(s). To achieve this broad cellular immune response we tested a heterologous DNA/protein combination vaccine strategy. We used a purified recombinant protein preparation of a unique M. tuberculosis antigen (rMT1721) found in the urine of TB patients, an optimized plasmid DNA expressing this protein (DNA-MT1721), and a Toll-like receptor 4 agonist adjuvant. We found that priming mice with DNA-MT1721 and subsequently boosting with rMT1721 elicited high titres of specific IgG1 and IgG2a antibodies as well as high magnitude and polyfunctional CD4(+) T-cell responses. However, no detectable CD8(+) T-cell response was observed using this regimen of immunization. In contrast, both CD4(+) and CD8(+) T-cell responses were detected after a prime/boost vaccination regimen using rMT1721 as the priming antigen and DNA-MT1721 as the boosting immunogen. These findings support the exploration of heterologous DNA/protein immunization strategies in vaccine development against TB and possibly other infectious diseases.

Preclinical evidence for implementing a prime-boost vaccine strategy for tuberculosis

In this review, published peer-reviewed preclinical studies using prime-boost tuberculosis (TB) vaccine regimens in animal challenge models for tuberculosis have been evaluated. These studies have been divided into groups that describe prime-boost vaccine combinations that performed better than, equivalent to, or worse than the currently used BCG vaccine. Review of the data has revealed interesting findings, including that more than half of the published studies using BCG as a prime combined with a novel boost vaccine give better efficacy than BCG alone and that the greatest reduction in Mycobacterium tuberculosis (M.tb.) colonization of animal tissues is provided by viral vectored vaccines delivered intranasally. Careful evaluation of these data should assist in defining the value of prime-boost regimens for advancement into human TB vaccine trials and stimulate the development of criteria for choosing which vaccine candidates should be studied further.

Simultaneous immunization against tuberculosis

Background

BCG, the only licensed vaccine against tuberculosis, provides some protection against disseminated disease in infants but has little effect on prevention of adult pulmonary disease. Newer parenteral immunization prime boost regimes may provide improved protection in experimental animal models but are unproven in man so that there remains a need for new and improved immunization strategies.

Methods and Findings

Mice were immunized parenterally, intranasally or simultaneously by both routes with BCG or recombinant mycobacterial antigens plus appropriate adjuvants. They were challenged with Mycobacterium tuberculosis (Mtb) and the kinetics of Mtb growth in the lungs measured. We show that simultaneous immunization (SIM) of mice by the intranasal and parenteral routes is highly effective in increasing protection over parenteral BCG administration alone. Intranasal immunization induces local pulmonary immunity capable of inhibiting the growth of Mtb in the early phase (the first week) of infection, while parenteral immunization has a later effect on Mtb growth. Importantly, these two effects are additive and do not depend on priming and boosting the immune response. The best SIM regimes reduce lung Mtb load by up to 2 logs more than BCG given by either route alone.

Conclusions

These data establish SIM as a novel and highly effective immunization strategy for Mtb that could be carried out at a single clinic visit. The efficacy of SIM does not depend on priming and boosting an immune response, but SIM is complementary to prime boost strategies and might be combined with them.

Recombinant BCG coexpressing Ag85B, CFP10, and interleukin-12 induces multifunctional Th1 and memory T cells in mice

Mycobacterium tuberculosis (MTB) continues to be a leading cause of human deaths due to an infectious agent. Current efforts are focused on making better TB vaccines. We describe the generation and immunological characterization of recombinant BCG (rBCG). This rBCG was generated by incorporating an expression plasmid encoding two mycobacterial antigens (Ag85B and CFP10) and human interleukin (IL)-12 into a BCG strain. Immunogenicity studies in mice showed that rBCG coexpressing Ag85B, CFP10, and IL-12 (rBCG::Ag85B-CFP10-IL-12) induces a robust immune response in mice. The rBCG vaccine promotes a T-cell response against MTB that is characterized by a high proportion of polyfunctional and memory T cells in spleen and lung. Our results showed strong immunogenicity and mycobacterial growth inhibition of rBCG::Ag85B-CFP10 plus IL-12 than that of BCG vaccine.

Development of vaccines against burkholderia pseudomallei

Burkholderia pseudomallei is a Gram-negative bacterium which is the causative agent of melioidosis, a disease which carries a high mortality and morbidity rate in endemic areas of South East Asia and Northern Australia. At present there is no available human vaccine that protects against B. pseudomallei, and with the current limitations of antibiotic treatment, the development of new preventative and therapeutic interventions is crucial. This review considers the multiple elements of melioidosis vaccine research including: (i) the immune responses required for protective immunity, (ii) animal models available for preclinical testing of potential candidates, (iii) the different experimental vaccine strategies which are being pursued, and (iv) the obstacles and opportunities for eventual registration of a licensed vaccine in humans.

Control of pathogenic CD4 T cells and lethal immunopathology by signaling immunoadaptor DAP12 during influenza infection

Immunopathology is a major cause of influenza-associated morbidity and mortality worldwide. However, the role and regulatory mechanisms of CD4 T cells in severe lung immunopathology following acute influenza infection are poorly understood. In this paper, we report that the emergence of immunopathogenic CD4 T cells is under the control of a transmembrane immunoadaptor DAP12 pathway during influenza infection. We find that the mice lacking DAP12 have unaltered viral clearance but easily succumb to influenza infection as a result of uncontrolled immunopathology. Such immunopathology is associated with markedly increased CD4 T cells displaying markedly increased cytotoxicity and Fas ligand expression. Furthermore, the immunopathogenic property of these CD4 T cells is transferrable. Thus, depletion of CD4 T cells or abrogation of Fas/Fas ligand signaling pathway improves survival and immunopathology. We further find that DAP12 expressed by dendritic cells plays an important role in controlling the immunopathogenic CD4 T cells during influenza infection. Our findings identify a novel pathway that controls the level of immune-pathogenic CD4 T cells during acute influenza infection.

Preclinical development of an in vivo BCG challenge model for testing candidate TB vaccine efficacy

There is an urgent need for an immunological correlate of protection against tuberculosis (TB) with which to evaluate candidate TB vaccines in clinical trials. Development of a human challenge model of Mycobacterium tuberculosis (M.tb) could facilitate the detection of such correlate(s). Here we propose a novel in vivo Bacille Calmette-Guérin (BCG) challenge model using BCG immunization as a surrogate for M.tb infection. Culture and quantitative PCR methods have been developed to quantify BCG in the skin, using the mouse ear as a surrogate for human skin. Candidate TB vaccines have been evaluated for their ability to protect against a BCG skin challenge, using this model, and the results indicate that protection against a BCG skin challenge is predictive of BCG vaccine efficacy against aerosol M.tb challenge. Translation of these findings to a human BCG challenge model could enable more rapid assessment and down selection of candidate TB vaccines and ultimately the identification of an immune correlate of protection.

Single dose adenovirus vectored vaccine induces a potent and long-lasting immune response against rabbit hemorrhagic disease virus after parenteral or mucosal administration

Rabbit hemorrhagic disease virus (RHDV) is the etiological agent of a lethal and contagious disease of rabbits that remains as a serious problem worldwide. As this virus does not replicate in cell culture systems, the capsid protein gene has been expressed in heterologous hosts or inserted in replication-competent viruses in order to obtain non-conventional RHDV vaccines. However, due to technological or safety issues, current RHDV vaccines are still prepared from organs of infected rabbits. In this work, two human type 5 derived replication-defective adenoviruses encoding the rabbit hemorrhagic disease virus VP60 capsid protein were constructed. The recombinant protein was expressed as a multimer in mouse and rabbit cell lines at levels that ranged from approximately 120 to 160 mg/L of culture. Mice intravenously or subcutaneously inoculated with a single 10(8) gene transfer units (GTU) dose of the AdVP60 vector (designed for VP60 intracellular expression) seroconverted at days 7 and 14 post-immunization, respectively. This vector generated a stronger response than that obtained with a second vector (AdVP60sec) designed for VP60 secretion. Rabbits were then immunized by parenteral or mucosal routes with a single 10(9)GTU dose of the AdVP60 and the antibody response was evaluated using a competition ELISA specific for RHDV or RHDVa. Protective hemagglutination inhibition (HI) titers were also promptly detected and IgG antibodies corresponding with inhibition percentages over 85% persisted up to one year in all rabbits, independently of the immunization route employed. These levels were similar to those elicited with inactivated RHDV or with VP60 obtained from yeast or insect cells. IgA specific antibodies were only found in saliva of rabbits immunized by intranasal instillation. The feasibility of VP60 production and vaccination of rabbits with replication-defective adenoviral vectors was demonstrated.

Tuberculosis vaccines in clinical trials

Effective prophylactic and/or therapeutic vaccination is a key strategy for controlling the global TB epidemic. The partial effectiveness of the existing TB vaccine, bacille Calmette-Guérin (BCG), suggests effective vaccination is possible and highlights the need for an improved vaccination strategy. Clinical trials are evaluating both modifications to the existing BCG immunization methods and also novel TB vaccines, designed to replace or boost BCG. Candidate vaccines in clinical development include live mycobacterial vaccines designed to replace BCG, subunit vaccines designed to boost BCG and therapeutic vaccines designed as an adjunct to chemotherapy. There is a great need for validated animal models, identification of immunological biomarkers of protection and field sites with the capacity for large-scale efficacy testing in order to develop and license a novel TB vaccine or regimen.

Prospects for a new, safer and more effective TB vaccine

Tuberculosis in infants and young children remains an all too common cause of morbidity and mortality in high burden countries, despite the fact that the majority of these children receive vaccination with BCG in infancy. BCG confers incomplete and variable protection against pulmonary tuberculosis [PTB] and is unsafe in HIV positive persons. Newer TB vaccines, which, it is hoped, will either replace or complement BCG are being developed and a number of these have reached the stage of clinical trials, with two booster vaccines going into Phase IIB trials in 2009. Prospects for at least one new licensed TB vaccine within the next 5-10 years appear reasonable. This article explores some of the issues around the development of new vaccines against TB and details the leading candidates.

Immunogenicity and protective efficacy against murine tuberculosis of a prime-boost regimen with BCG and a DNA vaccine expressing ESAT-6 and Ag85A fusion protein

Heterologous prime-boost regimens utilizing BCG as a prime vaccine probably represent the best hope for the development of novel tuberculosis (TB) vaccines. In this study, we examined the immunogenicity and protective efficacy of DNA vaccine (pcD685A) expressing the fusion protein of Ag85A and ESAT-6 (r685A) and its booster effects in BCG-immunized mice. The recombinant r685A fusion protein stimulated higher level of antigen-specific IFN-γ release in tuberculin skin test- (TST-) positive healthy household contacts of active pulmonary TB patients than that in TST-negative population. Vaccination of C57BL/6 mice with pcD685A resulted in significant protection against challenge with virulent Mycobacterium tuberculosis H37Rv when compared with the control group. Most importantly, pcD685A could act as a BCG booster and amplify Th1-type cell-mediated immunity in the lung of BCG-vaccinated mice as shown the increased expression of IFN-γ. The most significant reduction in bacterial load of both spleen and lung was obtained in mice vaccinated with BCG prime and pcD685A DNA booster when compared with BCG or pcD685A alone. Thus, our study indicates that pcD685A may be an efficient booster vaccine against TB with a strong ability to enhance prior BCG immunity.

Update on vaccination of cattle and wildlife populations against tuberculosis

In this review, the status of vaccination strategies to reduce bovine tuberculosis of cattle and wildlife reservoirs of the disease is discussed, with a focus on recent developments. Recent work in vaccines to protect humans against tuberculosis has been followed by a similar surge of interest in developing vaccines against bovine tuberculosis. The human vaccine, bacille Calmette-Guérin (BCG) affords protection against tuberculosis in cattle, but this protection is variable. In addition, vaccination with BCG compromises control strategies based on skin testing animals. In general, no single vaccine approach has shown itself to be significantly superior to BCG alone, however, vaccine combinations of BCG and vaccinating moiety such as adjuvanted subunit, virus vectored or DNA vaccines have been shown to induce protection superior to that achieved by BCG alone. Vaccinating wildlife species against tuberculosis is also an area which has been subjected to scrutiny. Recent work has focused on vaccinating wildlife orally, via the use of BCG formulated in baits consumed by these species. Results from trials in a number of animal species indicate that oral BCG vaccination can reduce disease severity following experimental challenge with Mycobacterium bovis and in a recent field trial, oral BCG vaccination was shown to prevent infection of wild possums following natural exposure to M. bovis. In conclusion, recent studies in cattle and wildlife have demonstrated the practicality and effectiveness of vaccinating animals against tuberculosis and provide much impetus for future use of vaccines.

Production of adenovirus vectors and their use as a delivery system for influenza vaccines

IMPORTANCE OF THE FIELD

With the emergence of highly pathogenic avian influenza H5N1 viruses that have crossed species barriers and are responsible for lethal infections in humans in many countries, there is an urgent need for the development of effective vaccines which can be produced in large quantities at a short notice and confer broad protection against these H5N1 variants. In order to meet the potential global vaccine demand in a pandemic scenario, new vaccine-production strategies must be explored in addition to the currently used egg-based technology for seasonal influenza.

AREAS COVERED IN THIS REVIEW

Adenovirus (Ad) based influenza vaccines represent an attractive alternative/supplement to the currently licensed egg-based influenza vaccines. Ad-based vaccines are relatively inexpensive to manufacture, and their production process does not require either chicken eggs or labor-intensive and time-consuming processes necessitating enhanced biosafety facilities. Most importantly, in a pandemic situation, this vaccine strategy could offer a stockpiling option to reduce the response time before a strain-matched vaccine could be developed.

WHAT THE READER WILL GAIN

This review discusses Ad-vector technology and the current progress in the development of Ad-based influenza vaccines.

TAKE HOME MESSAGE

Ad vector-based influenza vaccines for pandemic preparedness are under development to meet global vaccine demand.

Respiratory mucosal immunization with adenovirus gene transfer vector induces helper CD4 T cell-independent protective immunity

BACKGROUND

Virus-vectored vaccine is a powerful activator of CD8 T cell-mediated immunity and is especially amenable to respiratory mucosal immunization, offering hopes for use in humans with diminished helper CD4 T cell function. However, whether virus-mediated mucosal immunization can produce immune protective CD8 T cells without the CD4 T cell help remains to be investigated.

METHODS

We used a replication-deficient adenovirus vector expressing an Mycobacterium tuberculosis antigen Ag85A for intranasal vaccination and evaluated its effect on CD8 T cell activation and protection in mice depleted of CD4 T cells.

RESULTS

Intranasal vaccination of CD4 T cell-depleted mice led to suboptimal generation of Ag-specific tetramer(+) or interferon (IFN)-gamma-producing CD8 T cells in the lung and spleen but this was observed mainly at the early time after vaccination. Reduced CD8 T cell priming was also accompanied by decreased CD8 T cell responses (CTL). Nevertheless, the ratio of Ag-specific CD8 T cells to IFN-gamma-producing CD8 T cells in CD4 T cell-depleted hosts remained comparable to that in CD4 T cell-competent hosts. Furthermore, the 'unhelped' CD8 T cells also displayed a similar immune phenotype as the 'helped' counterparts. The animals with 'unhelped' CD8 T cells were as well-protected from pulmonary M. tuberculosis challenge as those with 'helped' CD8 T cells in the absence of CD4 T cells.

CONCLUSIONS

The data obtained in the present study suggest that the fully immune protective CD8 T cells can still be generated by respiratory mucosal viral-mediated immunization without CD4 T cells and that CD8 T cells, 'helped' or 'unhelped', can confer significant protection against pulmonary tuberculosis independent of CD4 T cells.

Toward novel vaccines against tuberculosis: current hopes and obstacles

Approximately 2 million people die of tuberculosis (TB) each year. The current vaccine, Bacille Calmette-Guérin (BCG), albeit widely employed, does not protect against adult pulmonary disease, and new vaccines are urgently needed to reduce the incidence of TB worldwide. New insights into the cellular and molecular mechanisms that underlie the interactions between Mycobacterium tuberculosis and its host have been exploited to develop novel vaccine candidates that recently have entered clinical trials. This review provides a brief overview of different approaches toward a new vaccination strategy and summarizes major challenges for the next decade.

Future vaccination strategies against tuberculosis: thinking outside the box

With almost a dozen vaccine candidates in clinical trials, tuberculosis (TB) research and development is finally reaping the first fruits of its labors. Vaccine candidates in clinical trials may prevent TB disease reactivation by efficiently containing the pathogen Mycobacterium tuberculosis (Mtb). Future research should target vaccines that achieve sterile eradication of Mtb or even prevent stable infection. These are ambitious goals that can be reached only by highly cooperative engagement of basic immunologists, vaccinologists, and clinical researchers--or in other words, by translation from basic immunology to vaccine research and development, as well as reverse translation of insights from clinical trials back to hypothesis-driven research in the basic laboratory. Here, we review current and future strategies toward the rational design of novel vaccines against TB, as well as the progress made thus far, and the hurdles that need to be overcome in the near and distant future.

Characterization of immune responses following intranasal immunization with the Mycobacterium bovis CFP-10 protein expressed by attenuated Salmonella typhimurium

Culture filtrate protein 10 (CFP-10) from Mycobacterium bovis or Mycobacterium tuberculosis (MTB) is an immunodominant T-cell antigen expressed during the early stages of infection. Because lungs are most commonly associated with primary M. bovis infections, specific immunity at this site is desirable for protection. Therefore, in this study, immune responses generated in mouse lung, spleen and Peyer's patches were examined following intranasal (i.n.) immunization with Salmonella typhimurium- expressing CFP-10. Cells harvested from the lungs and Peyer's patches of immunized mice and then stimulated with CFP-10 produced significant levels of IFN-γ and these mice developed elevated serum IgG and lung IgA anti-CFP-10 responses, suggesting that this approach induced potent anti-CFP-10 mucosal immunity. Our study demonstrates that i.n. administration of CFP-10 expressed by S. typhimurium represents an effective way to induce efficient immune response to M. bovis antigen.

Chemokine gene expression in lung CD8 T cells correlates with protective immunity in mice immunized intra-nasally with Adenovirus-85A

Background

Immunization of BALB/c mice with a recombinant adenovirus expressing Mycobacterium tuberculosis (M. tuberculosis) antigen 85A (Ad85A) protects against aerosol challenge with M. tuberculosis only when it is administered intra-nasally (i.n.). Immunization with Ad85A induces a lung-resident population of activated CD8 T cells that is antigen dependent, highly activated and mediates protection by early inhibition of M. tuberculosis growth. In order to determine why the i.n. route is so effective compared to parenteral immunization, we used microarray analysis to compare gene expression profiles of pulmonary and splenic CD8 T cells after i.n. or intra-dermal (i.d.) immunization.

Method

Total RNA from CD8 T cells was isolated from lungs or spleens of mice immunized with Ad85A by the i.n. or i.d. route. The gene profiles generated from each condition were compared. Statistically significant (p ≤ 0.05) differentially expressed genes were analyzed to determine if they mapped to particular molecular functions, biological processes or pathways using Gene Ontology and Panther DB mapping tools.

Results

CD8 T cells from lungs of i.n. immunized mice expressed a large number of chemokines chemotactic for resting and activated T cells as well as activation and survival genes. Lung lymphocytes from i.n. immunized mice also express the chemokine receptor gene Cxcr6, which is thought to aid long-term retention of antigen-responding T cells in the lungs. Expression of CXCR6 on CD8 T cells was confirmed by flow cytometry.

Conclusions

Our microarray analysis represents the first ex vivo study comparing gene expression profiles of CD8 T cells isolated from distinct sites after immunization with an adenoviral vector by different routes. It confirms earlier phenotypic data indicating that lung i.n. cells are more activated than lung i.d. CD8 T cells. The sustained expression of chemokines and activation genes enables CD8 T cells to remain in the lungs for extended periods after i.n. immunization. This may account for the early inhibition of M. tuberculosis growth observed in Ad85A i.n. immunized mice and explain the effectiveness of i.n. compared to parenteral immunization with this viral vector.