Mycobacterium tuberculosis senses host Interferon-γ via the membrane protein MmpL10

Abstract

Mycobacterium tuberculosis (Mtb) is one of the most successful human pathogens. Several cytokines are known to increase virulence of bacterial pathogens, leading us to investigate whether Interferon-γ (IFN-γ), a central regulator of the immune defense against Mtb, has a direct effect on the bacteria. We found that recombinant and T-cell derived IFN-γ rapidly induced a dose-dependent increase in the oxygen consumption rate (OCR) of Mtb, consistent with increased bacterial respiration. This was not observed in attenuated Bacillus Calmette–Guérin (BCG), and did not occur for other cytokines tested, including TNF-α. IFN-γ binds to the cell surface of intact Mtb, but not BCG. Mass spectrometry identified mycobacterial membrane protein large 10 (MmpL10) as the transmembrane binding partner of IFN-γ, supported by molecular modelling studies. IFN-γ binding and the OCR response was absent in Mtb Δmmpl10 strain and restored by complementation with wildtype mmpl10. RNA-sequencing and RT-PCR of Mtb exposed to IFN-γ revealed a distinct transcriptional profile, including genes involved in virulence. In a 3D granuloma model, IFN-γ promoted Mtb growth, which was lost in the Mtb Δmmpl10 strain and restored by complementation, supporting the involvement of MmpL10 in the response to IFN-γ. Finally, IFN-γ addition resulted in sterilization of Mtb cultures treated with isoniazid, indicating clearance of phenotypically resistant bacteria that persist in the presence of drug alone. Together our data are the first description of a mechanism allowing Mtb to respond to host immune activation that may be important in the immunopathogenesis of TB and have use in novel eradication strategies.

Mycobacterium tuberculosis strain with deletions in menT3 and menT4 is attenuated and confers protection in mice and guinea pigs

“…In addition to these, the transcript levels of Erdman_0321 (Rv0287, esxG ), a protein involved in the inhibition of phagosome maturation and pathogenesis of M. tuberculosis , were also reduced in the Δ menT4 Δ T3 strain (Supplementary Data 1 ) 40 . As shown in Supplementary Data 1 , the levels of transcripts encoding for proteins essential for growth (Erdman_3437 (Rv3137), Erdman_3739 (Rv3418c), stress adaptation (Erdman_0630 (Rv0574c), Erdman_2884 (Rv2624c)) and interaction with host Interferon-γ (IFN-γ) (Erdman_1325, Rv1183) were also reduced in Δ menT4 Δ T3 strain relative to the parental strain 36 , 41 – 44 . Several studies have reported that replacing an open reading frame with an antibiotic selection marker might affect the expression of neighboring genes due to the polar effect.…”

Monitoring host–pathogen interactions using chemical proteomics

“…For example, some bacterial pathogens are capable of directly sensing and responding to host cytokines to facilitate their survival and transmission. 186,187 IL-1b is reported to accelerate the growth of virulent E. coli, 188 and human IFN-g can activate a virulent phenotype of P. aeruginosa. 189 Since the incorporation of unnatural amino acids into proteins or larger peptides has become more accessible by genetic code expansion or site-specific modification, the elucidation of protein-based host-pathogen interaction is now more easily accessible.…”

Latent Tuberculosis Patients Have an Increased Frequency of IFN-γ-Producing CD5+ B Cells, Which Respond Efficiently to Mycobacterial Proteins

“…This study demonstrated that the CD5+ B cell subset is increased in LTB compared to HD and ATB. Moreover, LTB increases the frequency of IFN-γ-producing CD5+ B cells in response to proteins from Mtb, suggesting that the subpopulation CD5+ cells play an important role during the defense against Mtb, probably by the production of IFN-γ, a cytokine that is well-known for its capacity to activate the bactericide mechanism [ 31 , 32 ].…”

“…Thus, we evaluated the CD23 expression on B cells, and it did not show differences (Figure S2A), following the CD23 expression assessed on the CD5+ B subset (Figure 6E). Despite the IL-10 and IL-4 production by the CD5+ B cell subset, the frequency of the CD5+CD23+ subpopulation was decreased in UC and LTB patients stimulated with TP [UC: unstimulated, 52 (44-65); TP, 19 , p < 0.0285; LTB: unstimulated, 59 (57-59); TP, 25 (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36), p < 0.0372]. On the contrary, DR-TB patients increased the CD5+ CD23+ B cells frequency in both TP and TL stimuli [unstimulated: 46 (32-60); TP: 77 (65-94), p < 0.0324; TL: 83 (73-88), p < 0.0267] (Figure 6F).…”