Dataset Information

Novel vaccine potential of Rv3131, a DosR regulon-encoded putative nitroreductase, against hyper-virulent Mycobacterium tuberculosis strain K.

ABSTRACT: Accumulating evidence indicates that latency-associated Mycobacterium tuberculosis (Mtb)-specific antigens from the dormancy survival regulator regulon (DosR) may be promising novel vaccine target antigens for the development of an improved tuberculosis vaccine. After transcriptional profiling of DosR-related genes in the hyper-virulent Beijing Mtb strain K and the reference Mtb strain H37Rv, we selected Rv3131, a hypothetical nitroreductase, as a vaccine antigen and evaluated its vaccine efficacy against Mtb K. Mtb K exhibited stable and constitutive up-regulation of rv3131 relative to Mtb H37Rv under three different growth conditions (at least 2-fold induction) including exponential growth in normal culture conditions, hypoxia, and inside macrophages. Mice immunised with Rv3131 formulated in GLA-SE, a well-defined TLR4 adjuvant, displayed enhanced Rv3131-specific IFN-γ and serum IgG2c responses along with effector/memory T cell expansion and remarkable generation of Rv3131-specific multifunctional CD4⁺ T cells co-producing TNF-α, IFN-γ and IL-2 in both spleen and lung. Following challenge with Mtb K, the Rv3131/GLA-SE-immunised group exhibited a significant reduction in bacterial number and less extensive lung inflammation accompanied by the obvious persistence of Rv3131-specific multifunctional CD4⁺ T cells. These results suggest that Rv3131 could be an excellent candidate for potential use in a multi-antigenic Mtb subunit vaccine, especially against Mtb Beijing strains.

SUBMITTER: Kwon KW

PROVIDER: S-EPMC5341159 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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Novel vaccine potential of Rv3131, a DosR regulon-encoded putative nitroreductase, against hyper-virulent Mycobacterium tuberculosis strain K.

Kwon Kee Woong KW Kim Woo Sik WS Kim Hongmin H Han Seung Jung SJ Hahn Mi-Young MY Lee Jong Seok JS Nam Ki Taek KT Cho Sang-Nae SN Shin Sung Jae SJ

Scientific reports 20170308

Accumulating evidence indicates that latency-associated Mycobacterium tuberculosis (Mtb)-specific antigens from the dormancy survival regulator regulon (DosR) may be promising novel vaccine target antigens for the development of an improved tuberculosis vaccine. After transcriptional profiling of DosR-related genes in the hyper-virulent Beijing Mtb strain K and the reference Mtb strain H37Rv, we selected Rv3131, a hypothetical nitroreductase, as a vaccine antigen and evaluated its vaccine effica ...[more]

PMID: 28272457

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Project description:The DosR regulon, a set of 48 genes normally expressed in Mycobacterium tuberculosis under conditions that inhibit aerobic respiration, is controlled via the DosR-DosS/DosT two-component system. While the regulon requires induction in most M. tuberculosis isolates, for members of the Beijing lineage, its expression is uncoupled from the need for signaling. In our attempts to understand the mechanistic basis for this uncoupling in the Beijing background, we previously reported the identification of two synonymous single-nucleotide polymorphisms (SNPs) within the adjacent Rv3134c gene. In the present study, we have interrogated the impact of these SNPs on dosR expression in wild-type strains, as well as a range of dosR-dosS-dosT mutants, for both Beijing and non-Beijing M. tuberculosis backgrounds. In this manner, we have unequivocally determined that the C601T dosR promoter SNP is the sole requirement for the dramatic shift in the pattern of DosR regulon expression seen in this globally important lineage. Interestingly, we also show that DosT is completely nonfunctional within these strains. Thus, a complex series of evolutionary steps has led to the present-day Beijing DosR phenotype that, in turn, potentially confers a fitness advantage in the face of some form of host-associated selective pressure. Mycobacterium tuberculosis strains of the Beijing lineage have been described as being of enhanced virulence compared to other lineages, and in certain regions, they are associated with the dramatic spread of multidrug-resistant tuberculosis (TB). In terms of trying to understand the functional basis for these broad epidemiological phenomena, it is interesting that, in contrast to the other major lineages, the Beijing strains all constitutively overexpress members of the DosR regulon. Here, we identify the mutational events that led to the evolution of this unique phenotype. In addition, our work highlights the fact that important phenotypic differences exist between distinct M. tuberculosis lineages, with the potential to impact the efficacy of diagnosis, vaccination, and treatment programs.

Project description:Mycobacterium tuberculosis is a strict aerobe capable of prolonged survival in the absence of oxygen. We investigated the ability of anaerobic M. tuberculosis to counter challenges to internal pH homeostasis in the absence of aerobic respiration, the primary mechanism of proton efflux for aerobic bacilli. Anaerobic M. tuberculosis populations were markedly impaired for survival under a mildly acidic pH relative to standard culture conditions. An acidic environmental pH greatly increased the susceptibilities of anaerobic bacilli to the collapse of the proton motive force by protonophores, to antimicrobial compounds that target entry into the electron transport system, and to small organic acids with uncoupling activity. However, anaerobic bacilli exhibited high tolerance against these challenges at a near-neutral pH. At a slightly alkaline pH, which was near the optimum intracellular pH, the addition of protonophores even improved the long-term survival of bacilli. Although anaerobic M. tuberculosis bacilli under acidic conditions maintained 40% lower ATP levels than those of bacilli under standard culture conditions, ATP loss alone could not explain the drop in viability. Protonophores decreased ATP levels by more than 90% regardless of the extracellular pH but were bactericidal only under acidic conditions, indicating that anaerobic bacilli could survive an extreme ATP loss provided that the external pH was within viable intracellular parameters. Acidic conditions drastically decreased the anaerobic survival of a DosR mutant, while an alkaline environment improved the survival of the DosR mutant. Together, these findings indicate that intracellular acidification is a primary challenge for the survival of anaerobic M. tuberculosis and that the DosR regulon plays a critical role in sustaining internal pH homeostasis.IMPORTANCE During infection, M. tuberculosis bacilli are prevalent in environments largely devoid of oxygen, yet the factors that influence the survival of these severely growth-limited and metabolically limited bacilli remain poorly understood. We determined how anaerobic bacilli respond to fluctuations in environmental pH and observed that these bacilli were highly susceptible to stresses that promoted internal acidic stress, whereas conditions that promoted an alkaline internal pH promoted long-term survival even during severe ATP depletion. The DosR regulon, a major regulator of general hypoxic stress, played an important role in maintaining internal pH homeostasis under anaerobic conditions. Together, these findings indicate that in the absence of aerobic respiration, protection from internal acidification is crucial for long-term M. tuberculosis survival.

Dataset Information

Novel vaccine potential of Rv3131, a DosR regulon-encoded putative nitroreductase, against hyper-virulent Mycobacterium tuberculosis strain K.

Publications

Novel vaccine potential of Rv3131, a DosR regulon-encoded putative nitroreductase, against hyper-virulent Mycobacterium tuberculosis strain K.

Similar Datasets

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