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High Sequence Variability of the ppE18 Gene of Clinical Mycobacterium tuberculosis Complex Strains Potentially Impacts Effectivity of Vaccine Candidate M72/AS01E.

ABSTRACT: The development of an effective vaccine is urgently needed to fight tuberculosis (TB) which is still the leading cause of death from a single infectious agent worldwide. One of the promising vaccine candidates M72/AS01E consists of two proteins subunits PepA and PPE18 coded by Rv0125 and Rv1196. However, preliminary data indicate a high level of sequence variability among clinical Mycobacterium tuberculosis complex (MTBC) strains that might have an impact on the vaccine efficacy. To further investigate this finding, we determined ppE18 sequence variability in a well-characterized reference collection of 71 MTBC strains from 23 phylogenetic lineages representing the global MTBC diversity. In total, 100 sequence variations consisting of 96 single nucleotide polymorphisms (SNPs), three insertions and one deletion were detected resulting in 141 variable positions distributed over the entire gene. The majority of SNPs detected were non-synonymous (n = 68 vs. n = 28 synonymous). Strains from animal adapted lineages, e.g., M. bovis, showed a significant higher diversity than the human pathogens such as M. tuberculosis Haarlem. SNP patterns specific for different lineages as well as for deeper branches in the phylogeny could be identified. The results of our study demonstrate a high variability of the ppE18 gene even in the N-terminal domains that is normally highly conserved in ppe genes. As the N-terminal region interacts with TLR2 receptor inducing a protective anti-inflammatory immune response, genetic heterogeneity has a potential impact on the vaccine efficiency, however, this has to be investigated in future studies.

SUBMITTER: Homolka S

PROVIDER: S-EPMC4806982 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Abstract Background An effective tuberculosis (TB) vaccine is urgently needed to support the End TB Strategy to reduce the number of new TB cases by 80% by 2030. M72/AS01E candidate vaccine is an adjuvanted recombinant fusion protein derived from Mycobacterium tuberculosis Mtb32A and Mtb39A proteins. Methods We conducted a randomized, double-blind, placebo-controlled phase 2b trial (NCT01755598) in Southern and Eastern Africa to assess M72/AS01E’s efficacy against bacteriologically confirmed pulmonary TB disease in HIV-seronegative (HIV–) adults aged 18–50 years infected with Mtb (defined by a positive IFN-? release assay). Participants were randomized 1:1 to receive M72/AS01E or placebo at day D0 and D30. Reactogenicity, safety, immunogenicity were assessed, and incident TB disease measured from D30 postdose 2 up to ?24 months for this analysis (follow-up ongoing up to 37 months). Efficacy against various TB disease case definitions (Figure 1) was estimated. Primary objective: efficacy against culture- or PCR-confirmed pulmonary TB disease in HIV– adults (case definition 1; success criterion: lower limit of 90% 2-sided CI >0%, power: 80%). Results Demographic characteristics were similar between M72/AS01E (1786) and placebo (1787) recipients. Efficacy against pulmonary TB disease case definition 1 was 54.0% (90% CI: 13.9, 75.4; P = 0.042); efficacy against other case definitions and a sensitivity analysis are shown in Figure 1. Leading solicited symptoms were pain, fatigue, and headache (Figure 2). In all recipients, unsolicited symptoms (D0–29) were more frequent after M72/AS01E (67.4%) than placebo (45.4%), mainly attributable to increased injection site reactions and flu-like symptoms. Serious adverse events (D0–month 7) incidences were similar between groups (M72/AS01E: 1.6%; placebo: 1.8%). During the study, 24 adults died (14 due to traumatic events); all deaths were unrelated to the trial. Conclusion M72/AS01E presents a clinically acceptable safety profile and significantly reduces bacteriologically confirmed pulmonary TB disease incidence in HIV– adults with latent Mtb infection. Funding. BMGF; Aeras; DFID UK; DGIS; AusAID; GlaxoSmithKline Biologicals SA. Disclosures O. Van Der Meeren, GSK: Employee and Shareholder, Salary. M. Hatherill, Aeras: Investigator, Research grant. R. J. Wilkinson, GSK: Grant Investigator, indirect funding. H. M. Ayles, GSK: Grant Investigator, Research grant. G. Henostroza, Aeras: Investigator, Grant recipient. M. A. Demoitié, GSK: owns stocks and is named inventor on patent applications relating to certain uses of M72/AS01E, Salary. T. Singh, GSK: Employee and Shareholder, Salary. E. J. Akite, GSK: Employee, Salary. A. K. Azam, GSK: Employee, Salary. A. Bollaerts, GSK: Employee, Salary. A. M. Ginsberg, GSK: Collaborator, Research support. BMGF: Grant Investigator, Grant recipient. UK DFID: Grant Investigator, Grant recipient. P. Gillard, GSK: Employee and Shareholder, Salary and stock. D. R. Tait, Aeras: Employee, Salary. GSK: Shareholder, Salary.

Project description:ObjectivesTo assess the long-term safety and immunogenicity of the M72/ Adjuvant System (AS01E) candidate tuberculosis (TB) vaccine up to 3 years post-dose 2 (Y3) in human immunodeficiency virus (HIV)-positive (HIV+) and HIV-negative (HIV-) Indian adults.MethodsThis phase II, double-blind, randomised, controlled clinical trial (NCT01262976) was conducted at YRG CARE Medical Centre, in Chennai, India, between January 2011 and June 2015.Three cohorts (HIV+ participants stable on antiretroviral therapy [ART; HIV+ART+], HIV+ ART-naïve [HIV+ART-], and HIV- participants) were randomised (1:1) to receive 2 doses of M72/AS01E (M72/AS01E groups) or saline (control groups) 1 month apart and were followed up toY3. Latent TB infection was assessed at screening using an interferon-gamma (IFN-γ) release assay (IGRA). Safety and immunogenicity results up to Y1 post-vaccination were reported elsewhere. Here, we report serious adverse events (SAEs), humoral and cell-mediated immune (CMI) responses to M72 recorded at Y2 and Y3.ResultsOf 240 enrolled and vaccinated participants, 214 completed the long-term follow-up part of the study.In addition to SAEs previously described, between Y1 and Y2 1 M72/AS01E recipient in the HIV+ART+ cohort reported 2 SAEs (sinus cavernous thrombosis and gastroenteritis) that were not considered as causally related to the study vaccine.Vaccination elicited persistent humoral immune responses against M72. At Y3, seropositivity rates were 97.1%, 66.7%, and 97.3% and geometric mean concentrations (GMCs) were 22.0 ELISA units (EU)/mL, 4.9 EU/mL, and 24.3 EU/mL in the HIV+ART+, HIV+ART-, and HIV- cohorts, respectively. Humoral immune response was lowest in the HIV+ART- cohort.In M72/AS01E recipients, no notable decrease in the frequency of M72-specific CD4 T-cells expressing ≥2 immune markers among interleukin-2 (IL-2), IFN-γ, tumour necrosis factor alpha (TNF-α) and CD40 ligand (CD40L) was observed at Y3 post-vaccination. Median values (interquartile range) of 0.35% (0.13-0.49), 0.05% (0.01-0.10), and 0.15% (0.09-0.22) were recorded in the HIV+ART+, HIV+ART- and HIV- cohorts, respectively. CD4 T-cell response was lowest in the HIV+ART- cohort.No CD8 T-cell response was observed.ConclusionThe cellular and humoral immune responses induced by M72/AS01E in HIV+ and HIV- adults persisted up to Y3 post-vaccination. No safety concerns were raised regarding administration of M72/AS01E to HIV+ adults.Clinical trial registrationNCT01262976 (www.clinicaltrials.gov).

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High Sequence Variability of the ppE18 Gene of Clinical Mycobacterium tuberculosis Complex Strains Potentially Impacts Effectivity of Vaccine Candidate M72/AS01E.

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