Mycobacterium chelonae sensitisation induces CD4(+)-mediated cytotoxicity against BCG.
Significant variability in efficacy of live Mycobacterium bovis BCG as a tuberculosis vaccine is observed globally. Effects of pre-vaccination sensitisation to non-tuberculous environmental mycobacteria (Env) are suspected to underlie this phenomenon, but the mechanisms remain unclear. We postulated that it could be due to Env-specific T cells exerting cytotoxicity against BCG-infected host cells. After murine sensitisation with heat-killed antigens of different Env species, splenocytes from M. chelonae (CHE)-sensitised mice exerted the strongest cytotoxicity against autologous BCG-infected macrophages. This cytotoxicity was correlated with reduced BCG viability. The cytotoxicity was reduced by the depletion of CD4(+), but not CD8(+) or CD56(+) cells, and CD4(+) cells showed higher percentage of cytotoxicity than CD4(-) cells, supporting a role for CD4(+) cells in CHE-induced, BCG-specific cytotoxicity. Additionally, this cytotoxicity was IFN-gamma, perforin and FasL dependent. After CHE-sensitisation and subsequent BCG intranasal infection, there was significant expansion of lung CD4(+) cells, the main cell type producing IFN-gamma. This was associated with 2- and 6-fold reductions in lung BCG counts 1 and 3 wk, respectively post- infection, relative to non-sensitised mice. This is the first report describing cytotoxicity against BCG-infected cells as a mechanism underlying the influence of Env sensitisation on subsequent BCG responses.
Ho
Peiying
P
Department of Microbiology and Immunology Programme, National University of Singapore, Singapore.
Zhang
Lin
L
Wei
Xing
X
Seah
Geok Teng
GT
D000818:Animals; D000906:Antibodies / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D019002:CD56 Antigen / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D003602:Cytotoxicity, Immunologic / Q000276:immunology*; D053222:Fas Ligand Protein / Q000276:immunology / Q000378:metabolism; D005434:Flow Cytometry; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism; D016753:Interleukin-10 / Q000276:immunology / Q000378:metabolism; D008168:Lung / Q000276:immunology / Q000382:microbiology / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D009163:Mycobacterium bovis / Q000276:immunology*; D016926:Mycobacterium chelonae / Q000276:immunology*; D054353:Perforin / Q000276:immunology / Q000378:metabolism; D014376:Tuberculosis / Q000276:immunology* / Q000382:microbiology / Q000662:veterinary
D000906:Antibodies; D019002:CD56 Antigen; D053222:Fas Ligand Protein; D054353:Perforin; D016753:Interleukin-10; D007371:Interferon-gamma