Secretory Phosphatases Deficient Mutant of Mycobacterium tuberculosis Imparts Protection at the Primary Site of Infection in Guinea Pigs

Abstract

BackgroundThe failure of Mycobacterium bovis Bacille Calmette-Guérin to impart satisfactory protection against adult pulmonary tuberculosis has necessitated the development of more effective TB vaccines. The assumption that the vaccine strain should be antigenically as similar as possible to the disease causing pathogen has led to the evaluation of M.tuberculosis mutants as candidate tuberculosis vaccines.Methods/Principal FindingsIn this study, we have generated a mutant of M.tuberculosis (Mtb∆mms) by disrupting 3 virulence genes encoding a mycobacterial secretory acid phosphatase (sapM) and two phosphotyrosine protein phosphatases (mptpA and mptpB) and have evaluated its protective efficacy in guinea pigs. We observed that Mtb∆mms was highly attenuated in THP-1 macrophages. Moreover, no bacilli were recovered from the lungs and spleens of guinea pigs after 10 weeks of Mtb∆mms inoculation, although, initially, the mutant exhibited some growth in the spleens. Subsequently, when Mtb∆mms was evaluated for its protective efficacy, we observed that similar to BCG vaccination, Mtb∆mms exhibited a significantly reduced CFU in the lungs of guinea pigs when compared with the unvaccinated animals at 4 weeks after challenge. In addition, our observations at 12 weeks post challenge demonstrated that Mtb∆mms exhibited a more sustainable and superior protection in lungs as compared to BCG. However, the mutant failed to control the hematogenous spread as the splenic bacillary load between Mtb∆mms vaccinated and sham immunized animals was not significantly different. The gross pathological observations and histopathological observations corroborated the bacterial findings. Inspite of disruption of phosphatase genes in MtbΔmms, the lipid profiles of M.tuberculosis and MtbΔmms were identical indicating thereby that the phenotype of the mutant was ascribed to the loss of phosphatase genes and the influence was not related to any alteration in the lipid composition.Conclusions/SignificanceThis study highlights the importance of M.tuberculosis mutants in imparting protection against pulmonary TB.

Expression of Mycobacterium tuberculosis Protein Tyrosine Phosphatase B in Escherichia coli and Its Recovery from Inclusion Body

“…It has been described that Mtb bacteria defect in PtpB are not capable of developing latent Mtb infection in Guinea pig ten weeks post inoculation (Chauhan et al, 2013). This report underlines the important role of PtpB in the development of LBTI.…”

Mycobacterial Protein Tyrosine Phosphatases A and B Inhibitors Augment the Bactericidal Activity of the Standard Anti-tuberculosis Regimen

“…Based on their mechanism of action, mPTP inhibitors would likely have no activity against such organisms. Finally, it is possible that functional deficiency of mPTPA and/or mPTPB may be compensated by alternative Mtb phosphatases, such as SapM 15 . Recently, Chauhan et al generated an Mtb mutant (MtbΔmms) by disrupting the genes encoding PtpA, PtpB and SapM.…”

“…Recently, Chauhan et al generated an Mtb mutant (MtbΔmms) by disrupting the genes encoding PtpA, PtpB and SapM. After ten weeks of infection, guinea pigs infected with MtbΔmms showed a 4.69 log 10 reduction in lung CFU relative to those infected with the isogenic wild-type strain 15 . This mutant was more attenuated in the guinea pig model of chronic TB relative to an Mtb mutant lacking only PtpB 10 .…”

“…The importance of PTPs in cellular physiology is further underscored by the fact that they are often exploited and subverted by pathogenic bacteria to cause infection. The PTPs mPTPA and mPTPB from Mtb are required for optimal bacillary survival within host macrophages 10–14 and in animal models 10, 15 . Although Mtb itself lacks endogenous protein tyrosine phosphorylation, mPTPA and mPTPB support Mtb infection by acting on macrophage proteins to modulate host-pathogen interactions.…”

Bacterial Virulence Factors: Secreted for Survival

“…It was observed that SapM was indispensable for Mtb growth and that the infection with MtbDsapM mutant caused a significant reduction in pathological damage in the host [26]. The same group carried out another study to understand the effect of vaccination with the triple knockout mutant MtbDmptpADmptpBDsapM (MtbDmms) versus BCG on the survival and pathogenesis of Mtb [28]. They reported that the vaccination with MtbDmms mutant restricted the growth of Mtb at primary site of infection quite in comparison to BCG.…”