Recombinant Viral HCMV IL-10 Protein

Interleukin-10 (IL-10) is a pleiotropic cytokine that plays a crucial role in regulating immune and inflammstory responses (1). It has closely related homologs in the genome of several viruses including the human cytomegalovirus (HCMV), a prevalent pathogen that can remain in humans as a latent infection (2). Viruses use multiple strategies to avoid detection and clearance by the host immune system. One of these strategies is to express virus-encoded host cytokine homologs, such as IL-10, to modulate the host immune system to the virus’ advantage. HCMV IL-10 is encoded from noncontiguous stretches in the viral genome and is transcribed early during infection. It shares 27% amino acid sequence identity with the endogenous human IL-10. Despite its low homology with the human protein, it can bind to the human IL-10 receptor complex and induces signal transduction. HCMV IL-10 has been shown to suppress cytokine production and inhibit proliferation of mitogen-stimulated human peripheral blood mononuclear cells. HCMV IL-10 can also down regulate the antigen-presenting and accessory cell functions of human monocytes. These immunosuppressive properties of HCMV IL-10 likely contribute to immune evasion during virus infection (3).