Caspase-dependent inhibition of mousepox replication by gzmB

• Published in: PloS one 2009-10, Vol.4 (10), p.e7512-e7512
• Main Authors: Pardo, Julián, Gálvez, Eva María, Koskinen, Aulikki, Simon, Markus M, Lobigs, Mario, Regner, Matthias, Müllbacher, Arno
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Bax protein; bcl-2-Associated X Protein - metabolism; Calreticulin - metabolism; Caspase; Caspase 3 - metabolism; Caspase 7 - metabolism; Caspase-3; Caspases - metabolism; Cell Biology/Cellular Death and Stress Responses; Cytokines; Cytotoxicity; Ectromelia virus; Ectromelia virus - genetics; Ectromelia, Infectious - virology; Fibroblasts - metabolism; Granulocytes; Granzyme B; Granzymes - metabolism; Health aspects; Immunology; Infection; Infections; Inhibition; Ligands; Lymphocytes B; Male; Medical research; Mice; Mice, Inbred C57BL; Mice, Transgenic; Pathways; Peptides; Physiological aspects; Physiology; Proteases; Replication; Serine; Smallpox; T-Lymphocytes, Cytotoxic - metabolism; T-Lymphocytes, Cytotoxic - virology; Virology/Host Antiviral Responses; Virology/Immune Evasion; Virus diseases; Viruses
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0007512

Ectromelia virus is a natural mouse pathogen, causing mousepox. The cytotoxic T (Tc) cell granule serine-protease, granzyme B, is important for its control, but the underlying mechanism is unknown. Using ex vivo virus immune Tc cells, we have previously shown that granzyme B is able to activate several independent pro-apoptotic pathways, including those mediated by Bid/Bak/Bax and caspases-3/-7, in target cells pulsed with Tc cell determinants. Here we analysed the physiological relevance of those pro-apoptotic pathways in ectromelia infection, by incubating ectromelia-immune ex vivo Tc cells from granzyme A deficient (GzmB(+) Tc cells) or granzyme A and granzyme B deficient (GzmAxB(-/-) Tc cell) mice with ectromelia-infected target cells. We found that gzmB-induced apoptosis was totally blocked in ectromelia infected or peptide pulsed cells lacking caspases-3/-7. However ectromelia inhibited only partially apoptosis in cells deficient for Bid/Bak/Bax and not at all when both pathways were operative suggesting that the virus is able to interfere with apoptosis induced by gzmB in case not all pathways are activated. Importantly, inhibition of viral replication in vitro, as seen with wild type cells, was not affected by the lack of Bid/Bak/Bax but was significantly reduced in caspase-3/-7-deficient cells. Both caspase dependent processes were strictly dependent on gzmB, since Tc cells, lacking both gzms, neither induced apoptosis nor reduced viral titers. Out findings present the first evidence on the biological importance of the independent gzmB-inducible pro-apoptotic pathways in a physiological relevant virus infection model.