Poxvirus phosphatase alters interferon gamma regulated gene expression in macrophages

Abstract

Poxviruses including Variola (small pox), and Vaccinia, which is used to vaccinate against small pox have developed numerous methods for altering and/or evading an immune response. One such way is by the ability of the viral VH1 phosphatase to alter signaling cascades, which is vital for viral replication and may play a key role in the invasion of host defense during infection. Our studies focus on understanding if either the Vaccinia or Variola VH1 protein blocks interferon-gamma induced STAT1 regulated gene expression in macrophages. It is our hypothesis that the Variola protein will function more efficiently than Vaccinia in blocking STAT 1 function and may contribute to the pathogenicity of the smallpox virus. We first wanted to show that VH1 is present in the virus prior to infection. Results using RT-PCR showed that VH1 was expressed in Vaccinia virus that was used to infect cells. Next, a comparison of transfection reagents showed that Gene Porter 2 was optimal for our experiments in the macrophage cell P388D1. A series of co-transfection experiments showed that transfection of a VH1 expression plasmid reduced the STAT1 regulated reporter gene expression of the TAP-1 promoter. These data suggest that VH1 in the virus may prevent the induction of interferon-gamma regulated genes in macrophages during viral infection. Supported in part by NIH R25 GM067592-02 and P01 AI56097-02S1.