Vaccine protection against acquisition of neutralization-resistant SIV challenges in rhesus monkeys.

Preclinical studies of human immunodeficiency virus type 1 (HIV-1) vaccine candidates have typically shown post-infection virological control, but protection against acquisition of infection has previously only been reported against neutralization-sensitive virus challenges. Here we demonstrate vaccine protection against acquisition of fully heterologous, neutralization-resistant simian immunodeficiency virus (SIV) challenges in rhesus monkeys. Adenovirus/poxvirus and adenovirus/adenovirus-vector-based vaccines expressing SIV(SME543) Gag, Pol and Env antigens resulted in an 80% or greater reduction in the per-exposure probability of infection against repetitive, intrarectal SIV(MAC251) challenges in rhesus monkeys. Protection against acquisition of infection showed distinct immunological correlates compared with post-infection virological control and required the inclusion of Env in the vaccine regimen. These data demonstrate the proof-of-concept that optimized HIV-1 vaccine candidates can block acquisition of stringent, heterologous, neutralization-resistant virus challenges in rhesus monkeys.

Safety and Immunogenicity of Adenovirus 35 Tuberculosis Vaccine Candidate in Adults with Active or Previous Tuberculosis. A Randomized Trial.

RATIONALE: Administration of tuberculosis (TB) vaccines in participants with previous or current pulmonary TB may have the potential for causing harmful postvaccination immunologic (Koch-type) reactions. OBJECTIVES: To assess the safety and immunogenicity of three dose levels of the AERAS-402 live, replication-deficient adenovirus 35-vectored TB candidate vaccine, containing three mycobacterial antigens, in individuals with current or previous pulmonary TB. METHODS: We performed a phase II randomized, placebo-controlled, double-blinded dose-escalation study in an HIV-negative adult South African cohort (n = 72) with active pulmonary TB (on treatment for 1-4 mo) or pulmonary TB treated at least 12 months before study entry and considered cured. Safety endpoints included clinical assessment, flow volume curves, diffusing capacity of the lung for carbon monoxide, pulse oximetry, chest radiograph, and high-resolution thoracic computerized tomography scans. Cytokine expression by CD4 and CD8 T cells, after stimulation with Ag85A, Ag85B, and TB10.4 peptide pools, was examined by intracellular cytokine staining. MEASUREMENTS AND MAIN RESULTS: No apparent temporal or dose-related changes in clinical status (specifically acute, Koch phenomenon-like reactions), lung function, or radiology attributable to vaccine were observed. Injection site reactions were mild or moderate. Hematuria (by dipstick only) occurred in 25 (41%) of 61 AERAS-402 recipients and 3 (27%) of 11 placebo recipients, although no gross hematuria was reported. AERAS-402 induced robust CD8+ and moderate CD4+ T-cell responses, mainly to Ag85B in both vaccine groups. CONCLUSIONS: Administration of the AERAS-402 candidate TB vaccine to participants with current or previous pulmonary TB induced a robust immune response and is not associated with clinically significant pulmonary complications. Clinical trial registered with www.clinicaltrials.gov (NCT 02414828) and in the South African National Clinical Trials Register ( www.sanctr.gov.za DOH 27-0808-2060).

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.

Induction and regulation of T-cell immunity by the novel tuberculosis vaccine M72/AS01 in South African adults.

RATIONALE: Tuberculosis (TB) is a major cause of morbidity and mortality worldwide, thus there is an urgent need for novel TB vaccines. OBJECTIVES: We investigated a novel TB vaccine candidate, M72/AS01, in a phase IIa trial of bacille Calmette-Guérin-vaccinated, HIV-uninfected, and Mycobacterium tuberculosis (Mtb)-infected and -uninfected adults in South Africa. METHODS: Two doses of M72/AS01 were administered to healthy adults, with and without latent Mtb infection. Participants were monitored for 7 months after the first dose; cytokine production profiles, cell cycling, and regulatory phenotypes of vaccine-induced T cells were measured by flow cytometry. MEASUREMENTS AND MAIN RESULTS: The vaccine had a clinically acceptable safety profile, and induced robust, long-lived M72-specific T-cell and antibody responses. M72-specific CD4 T cells produced multiple combinations of Th1 cytokines. Analysis of T-cell Ki67 expression showed that most vaccination-induced T cells did not express Th1 cytokines or IL-17; these cytokine-negative Ki67(+) T cells included subsets of CD4 T cells with regulatory phenotypes. PD-1, a negative regulator of activated T cells, was transiently expressed on M72-specific CD4 T cells after vaccination. Specific T-cell subsets were present at significantly higher frequencies after vaccination of Mtb-infected versus -uninfected participants. CONCLUSIONS: M72/AS01 is clinically well tolerated in Mtb-infected and -uninfected adults, induces high frequencies of multifunctional T cells, and boosts distinct T-cell responses primed by natural Mtb infection. Moreover, these results provide important novel insights into how this immunity may be appropriately regulated after novel TB vaccination of Mtb-infected and -uninfected individuals.Clinical trial registered with www.clinicaltrials.gov (NCT 00600782).

Genetic immunization in the lung induces potent local and systemic immune responses.

Successful vaccination against respiratory infections requires elicitation of high levels of potent and durable humoral and cellular responses in the lower airways. To accomplish this goal, we used a fine aerosol that targets the entire lung surface through normal respiration to deliver replication-incompetent recombinant adenoviral vectors expressing gene products from several infectious pathogens. We show that this regimen induced remarkably high and stable lung T-cell responses in nonhuman primates and that it also generated systemic and respiratory tract humoral responses of both IgA and IgG isotypes. Moreover, strong immunogenicity was achieved even in animals with preexisting antiadenoviral immunity, overcoming a critical hurdle to the use of these vectors in humans, who commonly are immune to adenoviruses. The immunogenicity profile elicited with this regimen, which is distinct from either intramuscular or intranasal delivery, has highly desirable properties for protection against respiratory pathogens. We show that it can be used repeatedly to generate mucosal humoral, CD4, and CD8 T-cell responses and as such may be applicable to other mucosally transmitted pathogens such as HIV. Indeed, in a lethal challenge model, we show that aerosolized recombinant adenoviral immunization completely protects ferrets against H5N1 highly pathogenic avian influenza virus. Thus, genetic immunization in the lung offers a powerful platform approach to generating protective immune responses against respiratory pathogens.

Optimizing HIV-1-specific CD8+ T-cell induction by recombinant BCG in prime-boost regimens with heterologous viral vectors.

The desire to induce HIV-1-specific responses soon after birth to prevent breast milk transmission of HIV-1 led us to propose a vaccine regimen which primes HIV-1-specific T cells using a recombinant Mycobacterium bovis bacillus Calmette-Guérin (rBCG) vaccine. Because attenuated live bacterial vaccines are typically not sufficiently immunogenic as stand-alone vaccines, rBCG-primed T cells will likely require boost immunization(s). Here, we compared modified Danish (AERAS-401) and Pasteur lysine auxotroph (222) strains of BCG expressing the immunogen HIVA for their potency to prime HIV-1-specific responses in adult BALB/c mice and examined four heterologous boosting HIVA vaccines for their immunogenic synergy. We found that both BCG.HIVA(401) and BCG.HIVA(222) primed HIV-1-specific CD8(+) T-cell-mediated responses. The strongest boosts were delivered by human adenovirus-vectored HAdV5.HIVA and sheep atadenovirus-vectored OAdV7.HIVA vaccines, followed by poxvirus MVA.HIVA; the weakest was plasmid pTH.HIVA DNA. The prime-boost regimens induced T cells capable of efficient in vivo killing of sensitized target cells. We also observed that the BCG.HIVA(401) and BCG.HIVA(222) vaccines have broadly similar immunologic properties, but display a number of differences mainly detected through distinct profiles of soluble intercellular signaling molecules produced by immune splenocytes in response to both HIV-1- and BCG-specific stimuli. These results encourage further development of the rBCG prime-boost regimen.

Safety and immunogenicity of novel recombinant BCG and modified vaccinia virus Ankara vaccines in neonate rhesus macaques.

Although major inroads into making antiretroviral therapy available in resource-poor countries have been made, there is an urgent need for an effective vaccine administered shortly after birth, which would protect infants from acquiring human immunodeficiency virus type 1 (HIV-1) through breast-feeding. Bacillus Calmette-Guérin (BCG) is given to most infants at birth, and its recombinant form could be used to prime HIV-1-specific responses for a later boost by heterologous vectors delivering the same HIV-1-derived immunogen. Here, two groups of neonate Indian rhesus macaques were immunized with either novel candidate vaccine BCG.HIVA(401) or its parental strain AERAS-401, followed by two doses of recombinant modified vaccinia virus Ankara MVA.HIVA. The HIVA immunogen is derived from African clade A HIV-1. All vaccines were safe, giving local reactions consistent with the expected response at the injection site. No systemic adverse events or gross abnormality was seen at necropsy. Both AERAS-401 and BCG.HIVA(401) induced high frequencies of BCG-specific IFN-gamma-secreting lymphocytes that declined over 23 weeks, but the latter failed to induce detectable HIV-1-specific IFN-gamma responses. MVA.HIVA elicited HIV-1-specific IFN-gamma responses in all eight animals, but, except for one animal, these responses were weak. The HIV-1-specific responses induced in infants were lower compared to historic data generated by the two HIVA vaccines in adult animals but similar to other recombinant poxviruses tested in this model. This is the first time these vaccines were tested in newborn monkeys. These results inform further infant vaccine development and provide comparative data for two human infant vaccine trials of MVA.HIVA.

Novel recombinant Mycobacterium bovis BCG, ovine atadenovirus, and modified vaccinia virus Ankara vaccines combine to induce robust human immunodeficiency virus-specific CD4 and CD8 T-cell responses in rhesus macaques.

Mycobacterium bovis bacillus Calmette-Guérin (BCG), which elicits a degree of protective immunity against tuberculosis, is the most widely used vaccine in the world. Due to its persistence and immunogenicity, BCG has been proposed as a vector for vaccines against other infections, including HIV-1. BCG has a very good safety record, although it can cause disseminated disease in immunocompromised individuals. Here, we constructed a recombinant BCG vector expressing HIV-1 clade A-derived immunogen HIVA using the recently described safer and more immunogenic BCG strain AERAS-401 as the parental mycobacterium. Using routine ex vivo T-cell assays, BCG.HIVA(401) as a stand-alone vaccine induced undetectable and weak CD8 T-cell responses in BALB/c mice and rhesus macaques, respectively. However, when BCG.HIVA(401) was used as a priming component in heterologous vaccination regimens together with recombinant modified vaccinia virus Ankara-vectored MVA.HIVA and ovine atadenovirus-vectored OAdV.HIVA vaccines, robust HIV-1-specific T-cell responses were elicited. These high-frequency T-cell responses were broadly directed and capable of proliferation in response to recall antigen. Furthermore, multiple antigen-specific T-cell clonotypes were efficiently recruited into the memory pool. These desirable features are thought to be associated with good control of HIV-1 infection. In addition, strong and persistent T-cell responses specific for the BCG-derived purified protein derivative (PPD) antigen were induced. This work is the first demonstration of immunogenicity for two novel vaccine vectors and the corresponding candidate HIV-1 vaccines BCG.HIVA(401) and OAdV.HIVA in nonhuman primates. These results strongly support their further exploration.

Recombinant yellow fever vaccine virus 17D expressing simian immunodeficiency virus SIVmac239 gag induces SIV-specific CD8+ T-cell responses in rhesus macaques.

Here we describe a novel vaccine vector for expressing human immunodeficiency virus (HIV) antigens. We show that recombinant attenuated yellow fever vaccine virus 17D expressing simian immunodeficiency virus SIVmac239 Gag sequences can be used as a vector to generate SIV-specific CD8(+) T-cell responses in the rhesus macaque. Priming with recombinant BCG expressing SIV antigens increased the frequency of these SIV-specific CD8(+) T-cell responses after recombinant YF17D boosting. These recombinant YF17D-induced SIV-specific CD8(+) T cells secreted several cytokines, were largely effector memory T cells, and suppressed viral replication in CD4(+) T cells.

The novel tuberculosis vaccine, AERAS-402, induces robust and polyfunctional CD4+ and CD8+ T cells in adults.

RATIONALE: AERAS-402 is a novel tuberculosis vaccine designed to boost immunity primed by bacillus Calmette-Guérin (BCG), the only licensed vaccine. OBJECTIVES: We investigated the safety and immunogenicity of AERAS-402 in healthy Mycobacterium tuberculosis-uninfected BCG-vaccinated adults from a tuberculosis-endemic region of South Africa. METHODS: Escalating doses of AERAS-402 vaccine were administered intramuscularly to each of three groups of healthy South African BCG-vaccinated adults, and a fourth group received two injections of the maximal dose. Participants were monitored for 6 months, with all adverse effects documented. Vaccine-induced CD4(+) and CD8(+) T-cell immunity was characterized by an intracellular cytokine staining assay of whole blood and peripheral blood mononuclear cells. MEASUREMENTS AND MAIN RESULTS: AERAS-402 was well tolerated, and no vaccine-related serious adverse events were recorded. The vaccine induced a robust CD4(+) T-cell response dominated by cells coexpressing IFN-gamma, tumor necrosis factor-alpha, and IL-2 ("polyfunctional" cells). AERAS-402 also induced a potent CD8(+) T-cell response, characterized by cells expressing IFN-gamma and/or tumor necrosis factor-alpha, which persisted for the duration of the study. CONCLUSIONS: Vaccination with AERAS-402 is safe and immunogenic in healthy adults. The immunity induced by the vaccine appears promising: polyfunctional T cells are thought to be important for protection against intracellular pathogens such as Mycobacterium tuberculosis, and evidence is accumulating that CD8(+) T cells are also important. AERAS-402 induced a robust and durable CD8(+) T-cell response, which appears extremely promising. Clinical trial registered with www.sanctr.gov.za (NHREC no. 1381).

Update on research and development pipeline: tuberculosis vaccines.

Current tuberculosis (TB)-control methods, which do not include an adequate vaccine, do not effectively block transmission of TB. Modeling studies show that mass vaccination campaigns using new vaccines could prevent 85.9 million new cases and 14.5 million deaths from 2015 through 2050 in southern Asia alone. After a dearth of many years, the development pipeline now includes 7 vaccine candidates that are being tested in humans. Two nonreplicating viral vectored vaccines have very recently entered the first phase IIb efficacy trial in infants (the first such trial in 80 years) and in human immunodeficiency virus-infected adults. Science is moving forward, but the scientific advancements need to be accompanied by political mobilization to ensure that the resources are available to develop, manufacture, and distribute the new vaccines and, thus, save millions of lives.

Advances in tuberculosis vaccine strategies.

Tuberculosis (TB), an ancient human scourge, is a growing health problem in the developing world. Approximately two million deaths each year are caused by TB, which is the leading cause of death in HIV-infected individuals. Clearly, an improved TB vaccine is desperately needed. Heterologous prime-boost regimens probably represent the best hope for an improved vaccine regimen to prevent TB. This first generation of new vaccines might also complement drug treatment regimens and be effective against reactivation of TB from the latent state, which would significantly enhance their usefulness.

Evaluation of cellular immune responses in subjects chronically infected with HIV type 1.

The importance of host cellular immune responses, particularly CD8(+) cytotoxic T-lymphocyte (CTL) responses, in control of human immunodeficiency virus type 1 (HIV-1) infection has been demonstrated in many clinical studies. These studies, along with vaccination challenge studies in rhesus macaques, indicate the importance of cellular immune responses against HIV-1. Toward this end, we evaluated anti-HIV-1 cellular immune responses in a cohort of 54 subjects who were chronically infected with HIV-1. By validation of IFN-gamma ELISpot assay, we established a dual cut-off criterion for scoring a positive response. The magnitude and frequency of cellular immune responses were measured against HIV-1 antigens (Gag, Pol, Nef, Rev, and Tat), using synthetic peptides as antigens in ELISpot assay. Here we showed that HIV-1 Gag, Pol, and Nef were frequent targets of T cell responses in these subjects, whereas Tat and Rev were less frequently recognized. We further evaluated the possible association between host cellular immune responses and corresponding plasma viral loads in this cohort. By performing ranking correlation analysis, we demonstrated a positive correlation between host viral loads and ELISpot responses of HIV Gag and Pol in untreated subjects. For the subjects under antiviral regimens, however, we did not find any significant association. Our findings suggest that the high levels of ELISpot responses in chronically infected subjects were reflective of their persistent viral infection.

The role of "go no-go" decisions in TB vaccine development.

"Go no-go" decisions play a critical role in the product development plan of any TB vaccine at several points. Go no-go decisions are designed to serve the fundamental maxim in vaccine development that killing a bad vaccine project as early as possible is the hallmark of a successful overall program; in development, unlike in basic research, costs and skilled manpower requirements rise exponentially as the program proceeds. The opportunity costs in resources, manpower and equipment utilized on bad vaccine projects are unavailable to other vaccine programs. The go no-go decision is a fundamental piece of the process that balances risk, time and resources. An example of a go no-go decision development program is presented.

Protective efficacy of a second pneumococcal conjugate vaccine against pneumococcal acute otitis media in infants and children: randomized, controlled trial of a 7-valent pneumococcal polysaccharide-meningococcal outer membrane protein complex conjugate vaccine in 1666 children.

To assess the efficacy of a 7-valent pneumococcal polysaccharide-meningococcal outer membrane protein complex conjugate vaccine (PncOMPC) against acute otitis media (AOM), 1666 infants were randomly assigned to receive either PncOMPC or control vaccine (hepatitis B vaccine) at 2, 4, 6, and 12 months of age. Of the 835 children assigned to receive PncOMPC, 187 received a 23-valent pneumococcal polysaccharide vaccine (PncPS) at 12 months of age instead. Whenever AOM was diagnosed, middle ear fluid was aspirated for bacterial culture. In the PncOMPC and control groups, there were 110 and 250 AOM episodes, respectively, in children between 6.5 and 24 months of age that could be attributed to vaccine serotypes, which indicates a vaccine efficacy of 56% (95% confidence interval, 44%-66%). The serotype-specific efficacy ranged from 37% for 19F to 82% for 9V. The 2 boosters seemed to provide equal protection against AOM, but PncPS induced markedly higher antibody concentrations. The efficacy of PncOMPC was comparable to that of the recently licensed pneumococcal conjugate vaccine.

Inverse relationship between six week postvaccination varicella antibody response to vaccine and likelihood of long term breakthrough infection.

BACKGROUND: We used the large clinical database that supported the development of Oka/ Merck varicella vaccine to study the relationship between the primary varicella antibody response, as determined by gpELISA, an enzyme-linked immunosorbent assay that detects antibodies to varicella-zoster virus (VZV) glycoprotein, and the subsequent risk of postvaccination breakthrough varicella. METHODS: We vaccinated 1,164 healthy children with a single dose of varicella vaccine containing 2900 to 9000 plaque-forming units/dose. The primary immune response to vaccination was determined by gpELISA 6 weeks after vaccination. Subjects were followed annually for 7 years to ascertain cases of breakthrough varicella. RESULTS: The estimated vaccine efficacy among children with a 6-week postvaccination antibody titer of > or = 5 gpELISA units was 95.5% (95% confidence interval, 94.2%, 96.8%) compared with 83.5% (95% confidence interval, 76.9%, 89.5%) for subjects with a titer of <5 gpELISA units. Children with a 6-week postvaccination antibody titer of <5 gpELISA units were 3.5 times more likely than those with a titer of > or = 5 gpELISA units to develop breakthrough varicella. CONCLUSIONS: We identified a 6-week postvaccination antibody titer of > or = 5 gpELISA units as an approximate correlate of protection. In addition we established an accelerated failure time model based on log normal hazard that predicted varicella breakthrough rates based on the distribution of 6-week postvaccination varicella antibody titers.

A nonhuman primate toxicology and immunogenicity study evaluating aerosol delivery of AERAS-402/Ad35 vaccine: Evidence for transient t cell responses in peripheral blood and robust sustained responses in the lungs.

Bacille Calmette-Guérin (BCG), the only licensed vaccine for the prevention of tuberculosis (TB), provides only limited protection against certain forms of Mycobacterium tuberculosis (Mtb) infection. While infection with Mtb can be treated with antibiotics, the therapy is expensive, toxic, and requires several months for treatment. In addition, the emergence of drug resistant strains limits the impact of antibiotics and underlines the importance of developing a more effective vaccine to control this disease. Given that pulmonary TB is the most common form of the disease, a vaccine capable of inducing lung-resident immunity may be advantageous for combating this infection. New advances in pulmonary delivery make this route of vaccination feasible and affordable. Here, we evaluate the safety and immunogenicity of an aerosolized Ad35-based vaccine, AERAS-402, delivered to the lungs in nonhuman primates as part of a GLP acute and chronic toxicology and safety study. In this study, animals received three high doses (1 x 10(11) vp) of AERAS-402 by inhalation via a nebulizer at 1-week intervals. Aerosol delivery of AERAS-402 resulted in an increase in relative lung weights as well as microscopic findings in the lungs, mediastinal lymph nodes, bronchus-associated lymphatic tissue, and the naso-oropharynx that were consistent with the induction of an immune response during the acute phase. These findings resolved by the chronic phase and were considered to be non-adverse. Furthermore, we observed transient vaccine-specific immune responses in the peripheral blood as well as sustained high-level polyfunctional CD4(+) and CD8(+) T cell responses in the bronchoalveolar lavage fluid of vaccinated nonhuman primates. The data suggest that pulmonary delivery of Ad35-based vaccines can be safe and can induce potent lung-resident immunity.

The novel tuberculosis vaccine, AERAS-402, is safe in healthy infants previously vaccinated with BCG, and induces dose-dependent CD4 and CD8T cell responses.

BACKGROUND: Efforts to reduce risk of tuberculosis disease in children include development of effective vaccines. Our aim was to test safety and immunogenicity of the new adenovirus 35-vectored tuberculosis vaccine candidate AERAS-402 in infants, administered as a boost following a prime with the Bacille Calmette-Guerin vaccine. METHODS: In a phase 1 randomised, double-blind, placebo-controlled, dose-escalation trial, BCG-vaccinated infants aged 6-9 months were sequentially assigned to four study groups, then randomized to receive an increasing dose-strength of AERAS-402, or placebo. The highest dose group received a second dose of vaccine or placebo 56 days after the first. The primary study outcome was safety. Whole blood intracellular cytokine staining assessed immunogenicity. RESULTS: Forty-two infants received AERAS-402 and 15 infants received placebo. During follow-up of 182 days, an acceptable safety profile was shown with no serious adverse events or discontinuations related to the vaccine. AERAS-402 induced a specific T cell response. A single dose of AERAS-402 induced CD4T cells predominantly expressing single IFN-γ whereas two doses induced CD4T cells predominantly expressing IFN-γ, TNF-α and IL-2 together. CD8T cells were induced and were more likely to be present after 2 doses of AERAS-402. CONCLUSIONS: AERAS-402 was safe and immunogenic in healthy infants previously vaccinated with BCG at birth. Administration of the highest dose twice may be the most optimal vaccination strategy, based on the induced immunity. Multiple differences in T cell responses when infants are compared with adults vaccinated with AERAS-402, in the same setting and using the same whole blood intracellular cytokine assay, suggest specific strategies may be important for vaccination for each population.

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

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