The interferon gamma binding protein which allows the virus to replicate has been studied and its structure and action were published in a paper by researchers at St. Louis University and University of Alabama at Birmingham. This paper focuses on how this protein immobilized interferon, something that was previously not understood.
Saint Louis University. "How Poxviruses such as smallpox evade the Immune System" Science Daily 1 February 2008. 1 Feburary 2008