The function of TLR2 and the microbiome in macrophage-dependent dissemination of nontuberculous mycobacterial gut infection

ABSTRACT: Nontuberculous mycobacteria (NTM) infections are increasing in incidence and mortality worldwide. This study investigates the roles of Toll-like receptor 2 (TLR2) and the microbiome in orchestrating immune responses in NTM infection. Using a zebrafish larval model, we studied uptake of two NTM strains (Mycobacterium avium and M. marinum) through the gastrointestinal (GI) tract. We performed bacterial immersion experiments with these patho-gens using tlr2 mutant and wild-type zebrafish larvae in both germ-free (GF) and microbiome-colonized conditions. In wild-type microbiome-colonized larvae, M. avium predominantly localizes in the posterior gut, in contrast to an anterior-biased distribution for M. marinum. We found that both M. avium and M. marinum disseminate to posteri-or tissues after 2.5 days of immersion infection. Robotic gut microinjection confirms the protective roles of TLR2 and the microbiome against proliferation of M. avium and M. marinum. Expression analysis of downstream genes indicate that patterns of TLR2-dependent gene regulation differ between the two NTM species and show that the presence or absence of the microbiome differentially influences specific transcriptional responses to infection. Macrophage ablation studies show that macrophages facilitate dissemination of gut bacteria to distal tissues. Quantification of macrophages containing bacteria throughout the body show that the uptake of bacteria by mac-rophages depends on TLR2, but not on the microbiome. Using the same approach, TLR2 chemical antagonist treatment confirms the results observed in tlr2 mutant larvae. Live imaging of macrophage trajectories after bacte-rial gut microinjection show that macrophage motility after infection is impaired in tlr2 mutant larvae compared to the wild type. Notably, the effect of TLR2 on macrophage motility differs between GF and microbiome-colonized conditions. Our findings provide new insights into the coordinated roles of TLR2 signaling and the microbiome in controlling infection of mycobacteria via the gut and underscore the importance of TLR2 in macrophage function during mycobacterial gut infection

SUBMITTER: Herman P Spaink 

PROVIDER: S-BIAD2093 | bioimages |

SECONDARY ACCESSION(S):

REPOSITORIES: bioimages