The TB vaccine development pathway - An innovative approach to accelerating global TB vaccine development.

Two proof of concept clinical trials with TB vaccines demonstrate that new approaches can prevent sustained TB infection in adolescents (BCG revaccination) and TB disease in adults (M72/ASO1E) (Nemes et al., 2018; Tait et al., 2019) [1,2]. Both approaches are in late stage development and provide motivation and rationale to invest into a global TB vaccine pipeline. This pipeline needs to be diverse to address TB-specific challenges including variation in target populations, uncertainties in animal model predictivity and lack of immune correlates of protection. It requires that individual vaccine candidates must be advanced rationally and that the global pipeline must be managed in the most nimble and resource-efficient way, especially in the current constrained funding environment. The TB Vaccine Development Pathway is a webtool which has been developed as an offer to the field to provide a source of information and guidance covering vaccine development from discovery to implementation. It is underpinned by generic and TB vaccine-specific guidelines, regulatory frameworks and best practice, and was compiled by a multi-disciplinary team of scientific and technical experts with the input of the TB vaccine community. The Pathway is a unique tool to guide and accelerate the development of TB vaccine candidates and may be useful for other vaccine development fields.

Evaluation of heterologous prime-boost vaccination strategies using chimpanzee adenovirus and modified vaccinia virus for TB subunit vaccination in rhesus macaques.

Tuberculosis (TB) still is the principal cause of death from infectious disease and improved vaccination strategies are required to reduce the disease burden and break TB transmission. Here, we investigated different routes of administration of vectored subunit vaccines based on chimpanzee-derived adenovirus serotype-3 (ChAd3) for homologous prime-boosting and modified vaccinia virus Ankara (MVA) for heterologous boosting with both vaccine vectors expressing the same antigens from Mycobacterium tuberculosis (Ag85B, ESAT6, Rv2626, Rv1733, RpfD). Prime-boost strategies were evaluated for immunogenicity and protective efficacy in highly susceptible rhesus macaques. A fully parenteral administration regimen was compared to exclusive respiratory mucosal administration, while parenteral ChAd3-5Ag prime-boosting and mucosal MVA-5Ag boosting were applied as a push-and-pull strategy from the periphery to the lung. Immune analyses corroborated compartmentalized responses induced by parenteral versus mucosal vaccination. Despite eliciting TB-specific immune responses, none of the investigational regimes conferred a protective effect by standard readouts of TB compared to non-vaccinated controls, while lack of protection by BCG underpinned the stringency of this non-human primate test modality. Yet, TB manifestation after full parenteral vaccination was significantly less compared to exclusive mucosal vaccination.

Final Analysis of a Trial of M72/AS01E Vaccine to Prevent Tuberculosis.

BACKGROUND: Results of an earlier analysis of a trial of the M72/AS01E candidate vaccine against Mycobacterium tuberculosis showed that in infected adults, the vaccine provided 54.0% protection against active pulmonary tuberculosis disease, without evident safety concerns. We now report the results of the 3-year final analysis of efficacy, safety, and immunogenicity. METHODS: From August 2014 through November 2015, we enrolled adults 18 to 50 years of age with M. tuberculosis infection (defined by positive results on interferon-γ release assay) without evidence of active tuberculosis disease at centers in Kenya, South Africa, and Zambia. Participants were randomly assigned in a 1:1 ratio to receive two doses of either M72/AS01E or placebo, administered 1 month apart. The primary objective was to evaluate the efficacy of M72/AS01E to prevent active pulmonary tuberculosis disease according to the first case definition (bacteriologically confirmed pulmonary tuberculosis not associated with human immunodeficiency virus infection). Participants were followed for 3 years after the second dose. Participants with clinical suspicion of tuberculosis provided sputum samples for polymerase-chain-reaction assay, mycobacterial culture, or both. Humoral and cell-mediated immune responses were evaluated until month 36 in a subgroup of 300 participants. Safety was assessed in all participants who received at least one dose of M72/AS01E or placebo. RESULTS: A total of 3575 participants underwent randomization, of whom 3573 received at least one dose of M72/AS01E or placebo, and 3330 received both planned doses. Among the 3289 participants in the according-to-protocol efficacy cohort, 13 of the 1626 participants in the M72/AS01E group, as compared with 26 of the 1663 participants in the placebo group, had cases of tuberculosis that met the first case definition (incidence, 0.3 vs. 0.6 cases per 100 person-years). The vaccine efficacy at month 36 was 49.7% (90% confidence interval [CI], 12.1 to 71.2; 95% CI, 2.1 to 74.2). Among participants in the M72/AS01E group, the concentrations of M72-specific antibodies and the frequencies of M72-specific CD4+ T cells increased after the first dose and were sustained throughout the follow-up period. Serious adverse events, potential immune-mediated diseases, and deaths occurred with similar frequencies in the two groups. CONCLUSIONS: Among adults infected with M. tuberculosis, vaccination with M72/AS01E elicited an immune response and provided protection against progression to pulmonary tuberculosis disease for at least 3 years. (Funded by GlaxoSmithKline Biologicals and Aeras; ClinicalTrials.gov number, NCT01755598.).

Diagnostic Accuracy of Early Secretory Antigenic Target-6-Free Interferon-gamma Release Assay Compared to QuantiFERON-TB Gold In-tube.

BACKGROUND: Early secretory antigenic target-6 (ESAT-6) is an immunodominant Mycobacterium tuberculosis (M.tb) antigen included in novel vaccines against tuberculosis (TB) and in interferon-gamma (IFN-γ) release assays (IGRAs). Therefore, the availability of an ESAT-6-free IGRA is essential to determine M.tb infection status following vaccination with ESAT-6-containing vaccines. We aimed to qualify a recently developed ESAT-6-free IGRA and to assess its diagnostic performance in comparison to QuantiFERON-TB Gold In-tube (QFT). METHODS: Participants with different levels of M.tb exposure and TB disease were enrolled to determine the ESAT-6-free IGRA cutoff, test assay performance in independent cohorts compared to standard QFT, and perform a technical qualification of antigen-coated blood collection tubes. RESULTS: ESAT-6-free IGRA antigen recognition was evaluated in QFT-positive and QFT-negative South African adolescents. The ESAT-6-free IGRA cutoff was established at 0.61 IU/mL, based on receiver operating characteristic analysis in M.tb-unexposed controls and microbiologically confirmed pulmonary TB patients. In an independent cohort of healthy adolescents, levels of IFN-γ released in QFT and ESAT-6-free IGRA were highly correlated (P < .0001, r = 0.83) and yielded comparable positivity rates, 41.5% and 43.5%, respectively, with 91% concordance between the tests (kappa = 0.82; 95% confidence interval, 0.74-0.90; McNemar test P = .48). ESAT-6-free IGRA blood collection tubes had acceptable lot-to-lot variability, precision, and stability. CONCLUSIONS: The novel ESAT-6-free IGRA had diagnostic accuracy comparable to QFT and is suitable for use in clinical trials to assess efficacy of candidate TB vaccines to prevent established M.tb infection.

Optimization and Interpretation of Serial QuantiFERON Testing to Measure Acquisition of Mycobacterium tuberculosis Infection.

RATIONALE: Conversion from a negative to positive QuantiFERON-TB test is indicative of Mycobacterium tuberculosis (Mtb) infection, which predisposes individuals to tuberculosis disease. Interpretation of serial tests is confounded by immunological and technical variability. OBJECTIVES: To improve the consistency of serial QuantiFERON-TB testing algorithms and provide a data-driven definition of conversion. METHODS: Sources of QuantiFERON-TB variability were assessed, and optimal procedures were identified. Distributions of IFN-γ response levels were analyzed in healthy adolescents, Mtb-unexposed control subjects, and patients with pulmonary tuberculosis. MEASUREMENTS AND MAIN RESULTS: Individuals with no known Mtb exposure had IFN-γ values less than 0.2 IU/ml. Among individuals with IFN-γ values less than 0.2 IU/ml, 0.2-0.34 IU/ml, 0.35-0.7 IU/ml, and greater than 0.7 IU/ml, tuberculin skin test positivity results were 15%, 53%, 66%, and 91% (P < 0.005), respectively. Together, these findings suggest that values less than 0.2 IU/ml were true negatives. In short-term serial testing, "uncertain" conversions, with at least one value within the uncertainty zone (0.2-0.7 IU/ml), were partly explained by technical assay variability. Individuals who had a change in QuantiFERON-TB IFN-γ values from less than 0.2 to greater than 0.7 IU/ml had 10-fold higher tuberculosis incidence rates than those who maintained values less than 0.2 IU/ml over 2 years (P = 0.0003). By contrast, "uncertain" converters were not at higher risk than nonconverters (P = 0.229). Eighty-seven percent of patients with active tuberculosis had IFN-γ values greater than 0.7 IU/ml, suggesting that these values are consistent with established Mtb infection. CONCLUSIONS: Implementation of optimized procedures and a more rigorous QuantiFERON-TB conversion definition (an increase from IFN-γ <0.2 to >0.7 IU/ml) would allow more definitive detection of recent Mtb infection and potentially improve identification of those more likely to develop disease.

TNFerade Biologic: preclinical toxicology of a novel adenovector with a radiation-inducible promoter, carrying the human tumor necrosis factor alpha gene.

TNFerade Biologic (TNFerade) is a second-generation (E1-, E3-, and E4-deleted) replication-deficient adenovector carrying the transgene encoding for human tumor necrosis factor alpha (TNFalpha), regulated by the radiation-sensitive promoter Early Growth Response (Egr-1). We hypothesized that intratumoral injection of TNFerade followed by radiation would result in potentially therapeutic levels of TNFalpha with minimal toxicity. Three preclinical studies were conducted, the purpose of which was to characterize the toxicity and pharmacokinetics of TNFerade in conjunction with radiation in nude as well as immune-competent (Balb/c) mice. A total of 80 mice in the nude mouse toxicology study, all bearing human squamous cell carcinoma xenografts, 120 mice in the Balb/c study, and 33 nude mice in the pharmacokinetic study were used. Doses ranging from 4x10(9) to 4x10(10) particle units (pu) (4x10(11) pu in the Balb/c study) were explored, with and without radiation. In the nude mice studies, TNFerade was injected intratumorally, whereas in the Balb/c study, TNFerade was administered by subcutaneous injection. TNFerade was well tolerated. In the nude mice studies, no significant toxicity occurred in any dose group. In the Balb/c study, 6/40 mice at the top dose (4x10(11) pu) were sacrificed in moribund condition (5/20 in the TNFerade+radiation group, 1/20 in the TNFerade alone group). Necropsy showed local necrosis and ulceration at the site of the injection. No deaths or significant toxicity were observed at the lower dose levels (4x10(9) and 4x10(10) pu), indicating a large safety margin for initial studies in humans. The pharmacokinetic study demonstrated high sustained levels of TNFalpha in the tumor homogenate with no "spillover" to plasma, where TNFalpha levels were below the level of detection. Radiation increased intratumoral levels of TNFalpha by a factor of 12 (from 0.998 to 11.55 ng/g). In conclusion, a gene therapy approach with TNFerade, in combination with radiation, represents a potential way to utilize the potent anticancer activity of TNFalpha without systemic toxicity.