Virus Ankara Expressing Antigen 85A Research Articles

Safety, immunogenicity, and efficacy of the candidate tuberculosis vaccine MVA85A in healthy adults infected with HIV-1: a randomised, placebo-controlled, phase 2 trial

SummaryBackgroundHIV-1 infection is associated with increased risk of tuberculosis and a safe and effective vaccine would assist control measures. We assessed the safety, immunogenicity, and efficacy of a candidate tuberculosis vaccine, modified vaccinia virus Ankara expressing antigen 85A (MVA85A), in adults infected with HIV-1.MethodsWe did a randomised, double-blind, placebo-controlled, phase 2 trial of MVA85A in adults infected with HIV-1, at two clinical sites, in Cape Town, South Africa and Dakar, Senegal. Eligible participants were aged 18–50 years, had no evidence of active tuberculosis, and had baseline CD4 counts greater than 350 cells per μL if they had never received antiretroviral therapy or greater than 300 cells per μL (and with undetectable viral load before randomisation) if they were receiving antiretroviral therapy; participants with latent tuberculosis infection were eligible if they had completed at least 5 months of isoniazid preventive therapy, unless they had completed treatment for tuberculosis disease within 3 years before randomisation. Participants were randomly assigned (1:1) in blocks of four by randomly generated sequence to receive two intradermal injections of either MVA85A or placebo. Randomisation was stratified by antiretroviral therapy status and study site. Participants, nurses, investigators, and laboratory staff were masked to group allocation. The second (booster) injection of MVA85A or placebo was given 6–12 months after the first vaccination. The primary study outcome was safety in all vaccinated participants (the safety analysis population). Safety was assessed throughout the trial as defined in the protocol. Secondary outcomes were immunogenicity and vaccine efficacy against Mycobacterium tuberculosis infection and disease, assessed in the per-protocol population. Immunogenicity was assessed in a subset of participants at day 7 and day 28 after the first and second vaccination, and M tuberculosis infection and disease were assessed at the end of the study. The trial is registered with ClinicalTrials.gov, number NCT01151189.FindingsBetween Aug 4, 2011, and April 24, 2013, 650 participants were enrolled and randomly assigned; 649 were included in the safety analysis (324 in the MVA85A group and 325 in the placebo group) and 645 in the per-protocol analysis (320 and 325). 513 (71%) participants had CD4 counts greater than 300 cells per μL and were receiving antiretroviral therapy; 136 (21%) had CD4 counts above 350 cells per μL and had never received antiretroviral therapy. 277 (43%) had received isoniazid prophylaxis before enrolment. Solicited adverse events were more frequent in participants who received MVA85A (288 [89%]) than in those given placebo (235 [72%]). 34 serious adverse events were reported, 17 (5%) in each group. MVA85A induced a significant increase in antigen 85A-specific T-cell response, which peaked 7 days after both vaccinations and was primarily monofunctional. The number of participants with negative QuantiFERON-TB Gold In-Tube findings at baseline who converted to positive by the end of the study was 38 (20%) of 186 in the MVA85A group and 40 (23%) of 173 in the placebo group, for a vaccine efficacy of 11·7% (95% CI −41·3 to 44·9). In the per-protocol population, six (2%) cases of tuberculosis disease occurred in the MVA85A group and nine (3%) occurred in the placebo group, for a vaccine efficacy of 32·8% (95% CI −111·5 to 80·3).InterpretationMVA85A was well tolerated and immunogenic in adults infected with HIV-1. However, we detected no efficacy against M tuberculosis infection or disease, although the study was underpowered to detect an effect against disease. Potential reasons for the absence of detectable efficacy in this trial include insufficient induction of a vaccine-induced immune response or the wrong type of vaccine-induced immune response, or both.FundingEuropean & Developing Countries Clinical Trials Partnership (IP.2007.32080.002), Aeras, Bill & Melinda Gates Foundation, Wellcome Trust, and Oxford-Emergent Tuberculosis Consortium.

Roles for Treg expansion and HMGB1 signaling through the TLR1-2-6 axis in determining the magnitude of the antigen-specific immune response to MVA85A.

A better understanding of the relationships between vaccine, immunogenicity and protection from disease would greatly facilitate vaccine development. Modified vaccinia virus Ankara expressing antigen 85A (MVA85A) is a novel tuberculosis vaccine candidate designed to enhance responses induced by BCG. Antigen-specific interferon-γ (IFN-γ) production is greatly enhanced by MVA85A, however the variability between healthy individuals is extensive. In this study we have sought to characterize the early changes in gene expression in humans following vaccination with MVA85A and relate these to long-term immunogenicity. Two days post-vaccination, MVA85A induces a strong interferon and inflammatory response. Separating volunteers into high and low responders on the basis of T cell responses to 85A peptides measured during the trial, an expansion of circulating CD4+ CD25+ Foxp3+ cells is seen in low but not high responders. Additionally, high levels of Toll-like Receptor (TLR) 1 on day of vaccination are associated with an increased response to antigen 85A. In a classification model, combined expression levels of TLR1, TICAM2 and CD14 on day of vaccination and CTLA4 and IL2Rα two days post-vaccination can classify high and low responders with over 80% accuracy. Furthermore, administering MVA85A in mice with anti-TLR2 antibodies may abrogate high responses, and neutralising antibodies to TLRs 1, 2 or 6 or HMGB1 decrease CXCL2 production during in vitro stimulation with MVA85A. HMGB1 is released into the supernatant following atimulation with MVA85A and we propose this signal may be the trigger activating the TLR pathway. This study suggests an important role for an endogenous ligand in innate sensing of MVA and demonstrates the importance of pattern recognition receptors and regulatory T cell responses in determining the magnitude of the antigen specific immune response to vaccination with MVA85A in humans.

Evaluation of the Safety and Immunogenicity of a Candidate Tuberculosis Vaccine, MVA85A, Delivered by Aerosol to the Lungs of Macaques

Tuberculosis (TB) is a reemerging disease. The only available vaccine, Mycobacterium bovis BCG, is delivered intradermally and confers highly variable efficacy against pulmonary disease. There is an urgent need for improved vaccination strategies. Murine studies suggest that immunizations delivered directly to the respiratory mucosa might be a more effective route of vaccination. This study compared the immunogenicity of a leading candidate tuberculosis (TB) vaccine, modified vaccinia virus Ankara expressing antigen 85A (MVA85A), in rhesus macaques, delivered either as an aerosol or as an intradermal boost immunization 12 weeks after an intradermal BCG prime vaccine. Aerosol vaccination was well tolerated. MVA85A delivered by aerosol or by intradermal injection induced antigen-specific immune responses in the periphery and the lung, with a trend toward the highest response when the compartment and route of delivery were matched. The ability of poxvirus-vectored vaccines delivered by the systemic route to induce responses in the mucosal immune compartment in macaques is in contrast to the independent compartmentalization of mucosal and systemic immune systems described in mice. Unlike intradermal vaccination, aerosol vaccination did not induce a detectable serum anti-vector antibody response. The delivery of vaccines to the lungs might provide an immunization strategy that limits the induction of systemic anti-vector immunity, which would be extremely useful in the development of improved vaccine strategies. This is the first study to show a recombinant MVA-vectored vaccine to be highly immunogenic when delivered by the aerosol route to nonhuman primates. These results provide important safety and proof-of-concept data for further evaluation of this route of immunization for use in human clinical trials.

Effect of vaccine dose on the safety and immunogenicity of a candidate TB vaccine, MVA85A, in BCG vaccinated UK adults

PurposeA non-randomised, open-label, Phase I safety and immunogenicity dose-finding study to assess the safety and immunogenicity of the candidate TB vaccine Modified Vaccinia virus Ankara expressing Antigen 85A (MVA85A) from Mycobacterium tuberculosis (MTB) in healthy adult volunteers previously vaccinated with BCG. MethodsHealthy BCG-vaccinated volunteers were vaccinated with either 1×107 or 1×108PFU of MVA85A. All adverse events were documented and antigen specific T cell responses were measured using an ex vivo IFN-γ ELISPOT assay. Safety and immunogenicity were compared between the 2 dose groups and with a previous trial in which a dose of 5×107PFU MVA85A had been administered. ResultsThere were no serious adverse events recorded following administration of either 1×107 or 1×108PFU of MVA85A. Systemic adverse events were more frequently reported following administration of 1×108PFU of MVA85A when compared to either 5×107 or 1×107PFU of MVA85A but were mild or moderate in severity and resolved completely within 7days of immunisation. Antigen specific T cell responses as measured by the IFN-γ ELISPOT were significantly higher following immunisation in adults receiving 1×108PFU compared to the 5×107 and 1×107 doses. Additionally, a broader range of Ag85A epitopes are detected following 1×108PFU of MVA85A. ConclusionA higher dose of 1×108PFU of MVA85A is well-tolerated, increases the frequency of IFN-γ secreting T cells detected following immunisation and broadens the range of Ag85A epitopes detected.

Th1/Th17 Cell Induction and Corresponding Reduction in ATP Consumption following Vaccination with the Novel Mycobacterium tuberculosis Vaccine MVA85A

Vaccination with Bacille Calmette-Guérin (BCG) has traditionally been used for protection against disease caused by the bacterium Mycobacterium tuberculosis (M.tb). The efficacy of BCG, especially against pulmonary tuberculosis (TB) is variable. The best protection is conferred in temperate climates and there is close to zero protection in many tropical areas with a high prevalence of both tuberculous and non-tuberculous mycobacterial species. Although interferon (IFN)-γ is known to be important in protection against TB disease, data is emerging on a possible role for interleukin (IL)-17 as a key cytokine in both murine and bovine TB vaccine studies, as well as in humans. Modified Vaccinia virus Ankara expressing Antigen 85A (MVA85A) is a novel TB vaccine designed to enhance responses induced by BCG. Antigen-specific IFN-γ production has already been shown to peak one week post-MVA85A vaccination, and an inverse relationship between IL-17-producing cells and regulatory T cells expressing the ectonucleosidease CD39, which metabolises pro-inflammatory extracellular ATP has previously been described. This paper explores this relationship and finds that consumption of extracellular ATP by peripheral blood mononuclear cells from MVA85A-vaccinated subjects drops two weeks post-vaccination, corresponding to a drop in the percentage of a regulatory T cell subset expressing the ectonucleosidase CD39. Also at this time point, we report a peak in co-production of IL-17 and IFN-γ by CD4+ T cells. These results suggest a relationship between extracellular ATP and effector responses and unveil a possible pathway that could be targeted during vaccine design.

MVA.85A Boosting of BCG and an Attenuated, phoP Deficient M. tuberculosis Vaccine Both Show Protective Efficacy Against Tuberculosis in Rhesus Macaques

BackgroundContinuous high global tuberculosis (TB) mortality rates and variable vaccine efficacy of Mycobacterium bovis Bacille Calmette-Guérin (BCG) motivate the search for better vaccine regimes. Relevant models are required to downselect the most promising vaccines entering clinical efficacy testing and to identify correlates of protection.Methods and FindingsHere, we evaluated immunogenicity and protection against Mycobacterium tuberculosis in rhesus monkeys with two novel strategies: BCG boosted by modified vaccinia virus Ankara expressing antigen 85A (MVA.85A), and attenuated M. tuberculosis with a disrupted phoP gene (SO2) as a single-dose vaccine. Both strategies were well tolerated, and immunogenic as evidenced by induction of specific IFNγ responses. Antigen 85A-specific IFNγ secretion was specifically increased by MVA.85A boosting. Importantly, both MVA.85A and SO2 treatment significantly reduced pathology and chest X-ray scores upon infectious challenge with M. tuberculosis Erdman strain. MVA.85A and SO2 treatment also showed reduced average lung bacterial counts (1.0 and 1.2 log respectively, compared with 0.4 log for BCG) and significant protective effect by reduction in C-reactive protein levels, body weight loss, and decrease of erythrocyte-associated hematologic parameters (MCV, MCH, Hb, Ht) as markers of inflammatory infection, all relative to non-vaccinated controls. Lymphocyte stimulation revealed Ag85A-induced IFNγ levels post-infection as the strongest immunocorrelate for protection (spearman's rho: −0.60).ConclusionsBoth the BCG/MVA.85A prime-boost regime and the novel live attenuated, phoP deficient TB vaccine candidate SO2 showed significant protective efficacy by various parameters in rhesus macaques. Considering the phylogenetic relationship between macaque and man and the similarity in manifestations of TB disease, these data support further development of these primary and combination TB vaccine candidates.

Immunisation with BCG and recombinant MVA85A induces long-lasting, polyfunctional Mycobacterium tuberculosis-specific CD4+ memory T lymphocyte populations.

In the search for effective vaccines against intracellular pathogens such as HIV, tuberculosis and malaria, recombinant viral vectors are increasingly being used to boost previously primed T cell responses. Published data have shown prime-boost vaccination with BCG-MVA85A (modified vaccinia virus Ankara expressing antigen 85A) to be highly immunogenic in humans as measured by ex vivo IFN-gamma ELISPOT. Here, we used polychromatic flow cytometry to investigate the phenotypic and functional profile of these vaccine-induced Mycobacterium tuberculosis (M.tb) antigen 85A-specific responses in greater detail. Promisingly, antigen 85A-specific CD4(+) T cells were found to be highly polyfunctional, producing IFN-gamma, TNF-alpha, IL-2 and MIP-1beta. Surface staining showed the responding CD4(+) T cells to be relatively immature (CD45RO(+) CD27(int)CD57(-)); this observation was supported by the robust proliferative responses observed following antigenic stimulation. Furthermore, these phenotypic and functional properties were independent of clonotypic composition and epitope specificity, which was maintained through the different phases of the vaccine-induced immune response. Overall, these data strongly support the use of MVA85A in humans as a boosting agent to expand polyfunctional M.tb-specific CD4(+) T cells capable of significant secondary responses.

Boosting BCG with MVA85A: the first candidate subunit vaccine for tuberculosis in clinical trials

There is an urgent need for an improved vaccine against tuberculosis. Heterologous prime-boost immunization regimes induce higher levels of cellular immunity than homologous boosting with the same vaccine. Using BCG as the priming immunization in such a regime allows for the retention of the beneficial protective effects of BCG against disseminated disease in childhood. Recombinant poxviruses are powerful boosting agents, for both CD4+ and CD8+ T cells. Here we review the preclinical data from a BCG prime-recombinant modified vaccinia virus Ankara expressing antigen 85A (MVA85A) boost strategy. MVA85A is now in clinical trials in the UK and Africa and the design of these trials, including the ethical and regulatory issues are discussed.

Erratum: Recombinant modified vaccinia virus Ankara expressing antigen 85A boosts BCG-primed and naturally acquired antimycobacterial immunity in humans

Erratum: Recombinant modified vaccinia virus Ankara expressing antigen 85A boosts BCG-primed and naturally acquired antimycobacterial immunity in humans

Recombinant modified vaccinia virus Ankara expressing antigen 85A boosts BCG-primed and naturally acquired antimycobacterial immunity in humans

Protective immunity against Mycobacterium tuberculosis depends on the generation of a T(H)1-type cellular immune response, characterized by the secretion of interferon-gamma (IFN-gamma) from antigen-specific T cells. The induction of potent cellular immune responses by vaccination in humans has proven difficult. Recombinant viral vectors, especially poxviruses and adenoviruses, are particularly effective at boosting previously primed CD4(+) and CD8(+) T-cell responses against a number of intracellular pathogens in animal studies. In the first phase 1 study of any candidate subunit vaccine against tuberculosis, recombinant modified vaccinia virus Ankara (MVA) expressing antigen 85A (MVA85A) was found to induce high levels of antigen-specific IFN-gamma-secreting T cells when used alone in bacille Calmette-Guerin (BCG)-naive healthy volunteers. In volunteers who had been vaccinated 0.5-38 years previously with BCG, substantially higher levels of antigen-specific IFN-gamma-secreting T cells were induced, and at 24 weeks after vaccination these levels were 5-30 times greater than in vaccinees administered a single BCG vaccination. Boosting vaccinations with MVA85A could offer a practical and efficient strategy for enhancing and prolonging antimycobacterial immunity in tuberculosis-endemic areas.