Mycobacterium tuberculosis Rv3402c Enhances Mycobacterial Survival within Macrophages and Modulates the Host Pro-Inflammatory Cytokines Production via NF-Kappa B/ERK/p38 Signaling

Abstract

Intracellular survival plays a central role in the pathogenesis of Mycobacterium tuberculosis, a process which depends on an array of virulence factors to colonize and replicate within the host. The M. tuberculosis iron regulated open reading frame (ORF) rv3402c, encoding a conserved hypothetical protein, was shown to be up-regulated upon infection in both human and mice macrophages. To explore the function of this ORF, we heterologously expressed the rv3402c gene in the non-pathogenic fast-growing Mycobacterium smegmatis strain, and demonstrated that Rv3402c, a cell envelope-associated protein, was able to enhance the intracellular survival of recombinant M. smegmatis. Enhanced growth was not found to be the result of an increased resistance to intracellular stresses, as growth of the Rv3402c expressing strain was unaffected by iron depletion, H2O2 exposure, or acidic conditions. Colonization of macrophages by M. smegmatis expressing Rv3402c was associated with substantial cell death and significantly greater amount of TNF-α and IL-1β compared with controls. Rv3402c-induced TNF-α and IL-1β production was found to be mediated by NF-κB, ERK and p38 pathway in macrophages. In summary, our study suggests that Rv3402c delivered in a live M. smegmatis vehicle can modify the cytokines profile of macrophage, promote host cell death and enhance the persistence of mycobacterium within host cells.

Mycobacterium tuberculosis PE_PGRS41 Enhances the Intracellular Survival of M. smegmatis within Macrophages Via Blocking Innate Immunity and Inhibition of Host Defense

“…4). The increased survival within the macrophage cannot be attributed to the increased resistance to any of the tested stresses38, as PE_PGRS41 promoted M. smegmatis is more sensitive to in vitro stress (Fig. 3).…”

The Mycobacterium tuberculosis complex has a pathway for the biosynthesis of 4‐formamido‐4,6‐dideoxy‐d‐glucose

“…Although Rv3402c clearly does not play a role in iron metabolism, it was postulated that M. tuberculosis might alter its membrane structure under iron‐limiting conditions such as those found during intracellular growth or infection. Rv3402c was also found to enhance mycobacterial survival within macrophages and to modulate host pro‐inflammatory cytokine production . Indeed, heterologous expression of the rv3402c gene in the non‐pathogenic M. smegmatis strain showed that Rv3402c enhanced its intracellular survival in human and mice macrophages.…”

“…This particular gene has been shown to be upregulated in M. tuberculosis cultures deficient in iron . In addition, a recent report has demonstrated that the Rv3402c protein, when expressed in Mycobacterium smegmatis , enhances the organism's intracellular persistence within macrophages …”

“…5 In addition, a recent report has demonstrated that the Rv3402c protein, when expressed in Mycobacterium smegmatis, enhances the organism's intracellular persistence within macrophages. 6 We recently demonstrated that another protein, Rv3404c from M. tuberculosis H37Rv, functions as a sugar N-formyltransferase by transferring a formyl group from N 10 -formyltetrahydrofolate to dTDP-4amino-4,6-dideoxy-D-glucose. 7 Our results were especially intriguing given that there have been no reports in the literature regarding the existence of N-formylated sugars in M. tuberculosis.…”

Mycobacterium massiliense Type II genotype leads to higher level of colony forming units and TNF‐α secretion from human monocytes than Type I genotype

“…Generally, mycobacterial strains of high pathogenic potential have been reported to have TNF-a secretion capacity in monocytes/macrophages (33)(34)(35)(36). Particularly, in M. abscessus strains, the R morphotype is reported to induce higher levels of TNF-a secretion capacity in macrophages than the S morphotype (16).…”