Mycobacterium tuberculosis and Human Immunodeficiency Virus Type 1 Cooperatively Modulate Macrophage Apoptosis via Toll Like Receptor 2 and Calcium Homeostasis

PLoS One. 2015 Jul 1;10(7):e0131767. doi: 10.1371/journal.pone.0131767. eCollection 2015.

Abstract

The emergence of drug resistant strains of Mycobacterium tuberculosis (M. tuberculosis) together with reports of co-infections with the human immunodeficiency virus (HIV) has renewed interest to better understand the intricate mechanisms prevalent during co-infections. In this study we report a synergistic effect of M. tuberculosis and HIV-1, and their antigens Rv3416 and Nef, respectively, in inhibiting apoptosis of macrophages. This inhibition involves the TLR2 pathway and second messengers that play complementing and contrasting roles in regulating apoptosis. Interestingly, the route of calcium influx into cells differentially regulates apoptosis during antigenic co-stimulation. While calcium released from intracellular stores was anti-apoptotic, calcium influx from the external milieu was pro-apoptotic. Further, molecular sensors of intracellular calcium release aid in antigen mediated inhibition of apoptosis. A cross-regulation between oxidative burst and differential routing of calcium influx governed apoptosis. Interestingly, the HIV-1 Nef supported anti-apoptotic responses in macrophages whereas Vpu had no significant effect. These results point to a synergistic liaison between M. tuberculosis and HIV-1 in regulating macrophage apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens / metabolism
  • Apoptosis*
  • Bacterial Proteins / metabolism
  • Calcium / metabolism*
  • Cells, Cultured
  • Coinfection
  • Cytochromes c / metabolism
  • Gene Expression Regulation
  • HEK293 Cells
  • HIV Infections / complications
  • HIV-1*
  • Homeostasis
  • Humans
  • Leukocytes, Mononuclear / cytology
  • Macrophages / metabolism*
  • Macrophages / microbiology
  • Macrophages / virology
  • Membrane Potential, Mitochondrial
  • Mycobacterium tuberculosis*
  • RNA, Small Interfering / metabolism
  • Respiratory Burst
  • Signal Transduction
  • Toll-Like Receptor 2 / metabolism*
  • Tuberculosis / complications
  • nef Gene Products, Human Immunodeficiency Virus / metabolism

Substances

  • Antigens
  • Bacterial Proteins
  • RNA, Small Interfering
  • TLR2 protein, human
  • Toll-Like Receptor 2
  • nef Gene Products, Human Immunodeficiency Virus
  • nef protein, Human immunodeficiency virus 1
  • Cytochromes c
  • Calcium

Grants and funding

This work was supported by grants from the Department of Biotechnology, Ministry of Science and Technology, Government of India to KN and SJ and grants from the University of Delhi to KN. BT/PR/5352/MED/29/478/2012. SM is a recipient of CSIR-Senior Research Fellowship (File No 09/045(1014)/2010-EMR-1).