Virulent Mycobacterium fortuitum restricts NO production by a gamma interferon-activated J774 cell line and phagosome-lysosome fusion.
The virulence of different isolates of Mycobacterium has been associated with two morphologically distinguishable colonial variants: opaque (SmOp) and transparent (SmTr). In this report we used an in vitro assay to compare macrophage (Mphi) responses to SmOp and SmTr Mycobacterium fortuitum variants, taking advantage of the fact that these variants were derived from the same isolate. Cells preactivated or not with gamma interferon (IFN-gamma) were infected with SmOp or SmTr M. fortuitum. We showed that SmOp and SmTr induced different levels of nitric oxide (NO) production by IFN-gamma-stimulated Mphi. Indeed, the amount of IFN-gamma-induced NO production by J774 cells was 4.8 to 9.0 times higher by SmOp (23.1 to 37.7 micro M) compared to SmTr infection (3.9 to 4.8 micro M) (P = 0.0332), indicating that virulent SmTr bacilli restricted NO production. In addition, IFN-gamma-induced NO production by Mphi was higher when correlated with reduction of only avirulent SmOp bacillus viability. SNAP (S-nitroso-N-acetyl-DL-penicillamine)-induced NO production did not modify SmTr viability, indicating its resistance to nitrogen radicals. Electron microscopy studies were performed to evaluate the capacity of phagosomes to fuse with lysosomes labeled with bovine serum albumin-colloidal gold particles. By 24 h postinfection, 69% more phagosome-containing SmOp variant had fused with lysosomes compared to the SmTr-induced phagosomes. In conclusion, these data indicate that virulent SmTr bacilli may escape host defense by restricting IFN-gamma-induced NO production, resisting nitrogen toxic radicals, and limiting phagosome fusion with lysosomes.
Da Silva
Tânia Regina Marques
TR
Laboratório de Patologia e Biologia Celular, CPqGM, FIOCRUZ/BA, Universidade Federal da Bahia, Brazil.
De Freitas
Juliana Ribeiro
JR
Silva
Queilan Chagas
QC
Figueira
Cláudio Pereira
CP
Roxo
Eliana
E
Leão
Sylvia Cardoso
SC
De Freitas
Luiz Antônio Rodrigues
LA
Veras
Patrícia Sampaio Tavares
PS
D000818:Animals; D002460:Cell Line; D014644:Genetic Variation; D007371:Interferon-gamma / Q000494:pharmacology*; D008247:Lysosomes / Q000382:microbiology / Q000502:physiology* / Q000648:ultrastructure; D008262:Macrophage Activation / Q000187:drug effects; D008264:Macrophages / Q000382:microbiology* / Q000502:physiology* / Q000648:ultrastructure; D008561:Membrane Fusion; D051379:Mice; D008854:Microscopy, Electron; D019907:Mycobacterium fortuitum / Q000302:isolation & purification / Q000472:pathogenicity* / Q000502:physiology; D009569:Nitric Oxide / Q000096:biosynthesis*; D010588:Phagosomes / Q000382:microbiology / Q000502:physiology* / Q000648:ultrastructure; D011994:Recombinant Proteins; D014774:Virulence / Q000235:genetics
D011994:Recombinant Proteins; D009569:Nitric Oxide; D007371:Interferon-gamma