Expression of the PE_PGRS 33 protein in Mycobacterium smegmatis triggers necrosis in macrophages and enhanced mycobacterial survival.
Research on mycobacteria-specific PE_PGRS genes indicates that they code for cell surface proteins that may influence virulence and the infection of host cells by mycobacteria. In the studies presented here, we have expressed the PE_PGRS 33 gene in a non-pathogenic fast-growing Mycobacterium smegmatis strain and demonstrated that it survives better in macrophage cultures, in vitro as well as in mice after intraperitoneal administration, than the parental strain containing the vector only or a strain expressing only the PE domain of PE_PGRS 33. In macrophages, enhanced colonization by the M. smegmatis expressing PE_PGRS 33 was associated with macrophage aggregation and clearance of macrophage monolayers, visible cell necrosis and significantly greater levels of TNF (TNF-alpha) in the cultures compared with controls. The presence of macrophage cell necrosis was confirmed by measurement of significantly greater levels of lactate dehydrogenase and nucleosomes in the supernatants of the macrophage cultures infected with M. smegmatis expressing PE_PGRS 33. Antibodies directed against TNF partially reduced cytolysis, suggesting that this cytokine is critical but not sufficient for the observed macrophage necrosis and enhanced mycobacterial survival. These results extend earlier observations, which suggested that PE_PGRS proteins may have a role in the pathogenesis of mycobacterial disease and that there may be a specific role for these proteins in influencing host cell responses to infection.
Dheenadhayalan
Veerabadran
V
Laboratory of Mycobacterial Diseases and Cellular Immunology, Center for Biologics Evaluation and Research, Food and Drug Administration, Building 29, Room 503, HFM-431, 29 Lincoln Drive, Bethesda, MD 20892, USA. Dheenadhayalan@cber.fda.gov
Delogu
Giovanni
G
Brennan
Michael J
MJ
D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008099:Liver / Q000382:microbiology; D008168:Lung / Q000382:microbiology; D008264:Macrophages / Q000382:microbiology* / Q000473:pathology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009165:Mycobacterium Infections, Nontuberculous / Q000382:microbiology; D020102:Mycobacterium smegmatis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009336:Necrosis; D013154:Spleen / Q000382:microbiology; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D008565:Membrane Proteins; C440642:PE-PGRS protein, Mycobacterium; D014409:Tumor Necrosis Factor-alpha; D007770:L-Lactate Dehydrogenase