The results have potentially wide-reaching implications for immune research. Humans and other mammals have spent millions of years living and evolving with latent viral infections, Virgin notes, and the new results imply that infections may have altered our immune systems at a fundamental level. This could mean the virus-free animal models scientists use to study vaccines, autoimmune diseases, and other immune system issues have the potential to produce misleading results.
"Chronic virus infections may in part define what a normal human immune response is," says Virgin, who is the Edward Mallinckrodt Professor of Pathology and Immunology. "We may need to think about that as we consider the implications animal model results hold for human diseases."
Scientists have recognized for years that many types of bacteria and other microorganisms live in the human gut to the advantage of both the microbes and their human hosts. The results from the Virgin lab are among the first to suggest the potential for symbiotic benefits from viral infections that live in areas beyond epithelial surfaces like the skin, throat or intestines.
For the new research, Virgin's group worked with strains of mouse herpes virus closely related to human Epstein-Barr virus, Kaposi's sarcoma-associated herpes virus and cytomegalovirus. During studies of how mouse herpes viruses transition from acute to latent infections, Virgin made a discovery that piqued his interest in the possibility that latent infections might confer unrecognized benefits.
"We found evidence that the mouse immune system controls latent herpes infections in part by increasing production of a protein hormone called interferon gamma," Virgin says. "This is a signaling hormone that in effect puts some immune system soldiers on
Source:Washington University School of Medicine