Role of protease inhibitor 9 in survival and replication of Mycobacterium tuberculosis in mononuclear phagocytes from HIV-1-infected patients.
OBJECTIVE
Predisposition to opportunistic infections by Mycobacterium tuberculosis (MTB) is a concomitant of HIV-1 infection and occurrence of tuberculosis is independent of circulating CD4(+) T-cell count in HIV-1-infected patients. Infection of mononuclear phagocytes from healthy individuals by virulent MTB is associated with expression of the antiapoptotic molecule protease inhibitor 9 (PI-9), and PI-9 contributes to successful parasitism of macrophages by MTB. Here we studied the contribution of PI-9 to successful MTB infection of monocytes from HIV-1-infected patients.


METHODS
Blood monocytes obtained from HAART-treated HIV-1-infected patients (HIV+) and healthy controls were assessed for support of MTB H37Rv growth by assessment of MTB 16S ribosomal (r)RNA in cell lysates on day 1 and day 7 by real-time reverse transcription-PCR. PI-9 expression in monocyte cell lysates was assessed by ELISA and by reverse transcription-PCR. Inhibition of intracellular PI-9 was achieved by siRNA to PI-9 and compared to control constructs.


RESULTS
Monocytes from HIV-infected patients supported higher MTB growth [MTB 16S rRNA (d7/d1)] as compared with monocytes from healthy controls. Both PI-9 protein and mRNA were significantly higher in monocytes from HIV-infected patients as compared with healthy controls. PI-9 protein levels prior to MTB infection correlated with MTB replication on day 7, and with plasma soluble CD14 levels. Silencing of PI-9 by transfection of monocytes from HIV-1-infected patients with PI-9-specific siRNA prior to infection improved intracellular containment of MTB.


CONCLUSIONS
Increased intracellular PI-9 activity in mononuclear phagocytes from HIV-infected patients contributes to successful intracellular infection by virulent MTB.
aDivision of Infectious Diseases bDivision of Pulmonary, Critical Care and Sleep Medicine, Case Western Reserve University School of Medicine cLouis Stokes Cleveland Department of Veterans Affairs Medical Center dUniversity Hospitals Case Medical Center, Cleveland, Ohio, USA eDepartment of Immunopathology, Sanquin Research at CLB and Landsteiner Laboratory, Academic Medical Center, Amsterdam, The Netherlands.
Zahra
Z
Toossi
Mianda
M
Wu
Shigou
S
Liu
Christina S
CS
Hirsch
Jessica
J
Walrath
Marieke
M
van Ham
Richard F
RF
Silver
D000328:Adult; D000368:Aged; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D015658:HIV Infections / Q000276:immunology*; D054884:Host-Pathogen Interactions; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000382:microbiology*; D008297:Male; D050296:Microbial Viability; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000254:growth & development / Q000276:immunology* / Q000502:physiology*; D012336:RNA, Ribosomal, 16S / Q000032:analysis / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015843:Serpins / Q000378:metabolism*
D012336:RNA, Ribosomal, 16S; C102316:SERPINB9 protein, human; D015843:Serpins