Dissection of ESAT-6 system 1 of Mycobacterium tuberculosis and impact on immunogenicity and virulence.
The dedicated secretion system ESX-1 of Mycobacterium tuberculosis encoded by the extended RD1 region (extRD1) assures export of the ESAT-6 protein and its partner, the 10-kDa culture filtrate protein CFP-10, and is missing from the vaccine strains M. bovis BCG and M. microti. Here, we systematically investigated the involvement of each individual ESX-1 gene in the secretion of both antigens, specific immunogenicity, and virulence. ESX-1-complemented BCG and M. microti strains were more efficiently engulfed by bone-marrow-derived macrophages than controls, and this may account for the enhanced in vivo growth of ESX-1-carrying strains. Inactivation of gene pe35 (Rv3872) impaired expression of CFP-10 and ESAT-6, suggesting a role in regulation. Genes Rv3868, Rv3869, Rv3870, Rv3871, and Rv3877 encoding an ATP-dependent chaperone and translocon were essential for secretion of ESAT-6 and CFP-10 in contrast to ppe68 Rv3873 and Rv3876, whose inactivation did not impair secretion of ESAT-6. A strict correlation was found between ESAT-6 export and the generation of ESAT-6 specific T-cell responses in mice. Furthermore, ESAT-6 secretion and specific immunogenicity were almost always correlated with enhanced virulence in the SCID mouse model. Only loss of Rv3865 and part of Rv3866 did not affect ESAT-6 secretion or immunogenicity but led to attenuation. This suggests that Rv3865/66 represent a new virulence factor that is independent from ESAT-6 secretion. The present study has allowed us to identify new aspects of the extRD1 region of M. tuberculosis and to explore its role in the pathogenesis of tuberculosis.
Brodin
Priscille
P
Unité de Génétique Moléculaire Bactérienne, Institut Pasteur, 25-28 Rue du Docteur Roux, 75724 Paris Cedex 15, France.
Majlessi
Laleh
L
Marsollier
Laurent
L
de Jonge
Marien I
MI
Bottai
Daria
D
Demangel
Caroline
C
Hinds
Jason
J
Neyrolles
Olivier
O
Butcher
Philip D
PD
Leclerc
Claude
C
Cole
Stewart T
ST
Brosch
Roland
R
D000818:Animals; D000942:Antigens, Bacterial / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism; D005260:Female; D008264:Macrophages / Q000276:immunology / Q000382:microbiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016513:Mice, SCID; D009163:Mycobacterium bovis / Q000276:immunology; D009169:Mycobacterium tuberculosis / Q000254:growth & development / Q000276:immunology* / Q000472:pathogenicity*; D014158:Transcription, Genetic / Q000276:immunology; D014774:Virulence / Q000276:immunology
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C117940:CFP-10 protein, Mycobacterium tuberculosis; C093276:ESAT-6 protein, Mycobacterium tuberculosis