M-T2: a poxvirus TNF receptor homologue with dual activities.

Poxviruses are experts at manipulating and evading the host's immune response. They have acquired a number of open reading frames which specifically confer direct anti-immune properties, either by mimicking cytokine receptors and growth factors or by disarming cytokine regulatory cascades. The Myxoma T2 protein (M-T2), a TNF receptor homologue, is secreted from virus infected cells and can bind TNF-alpha with high affinity, and thereby inhibit TNF-alpha-mediated cytotoxicity. M-T2 also acts to inhibit virus-induced lymphocyte apoptosis by an as yet undefined mechanism. As such, T2 constitutes a significant virulence factor for poxviruses, influencing the outcome of infection, both in vitro and in vivo.