VT-310 is a novel secreted glycoprotein recently identified in the genomes of the primate poxviruses that have evolved to subvert the primate (human) immune system.  VT-310 is a homologue of human IL-10.  IL-10 is one of the body's natural mechanisms used to limit, and ultimately terminate, an ongoing inflammatory response. IL-10 suppresses T-cell responses directly by reducing T cells production of IL-2, TNF- α and IL-5, and indirectly suppresses T-cell response by inhibiting antigen presentation by reducing the expression of MHC and co-stimulatory molecules by antigen presenting cells.