Scientists can't prove it yet, but they suspect the missing immune system component, a group of molecules known as the Major Histocompatibility Complex (MHC) Class Ia, has a previously unrecognized backup that is similar enough to step in and fill the void left by its absence. If so, that backup may become a new focus for efforts to design antiviral vaccines.

"This surprising finding contradicts a long-held belief about control of viral infection: that the immune system must have MHC Class I molecules to recognize and destroy virus-infected cells," says senior author Skip Virgin, M.D., Ph.D., professor of pathology and immunology and of molecular microbiology. "It also suggests that we may need to take a more extensive look at what immune system elements play a role in controlling chronic viral infections."

The study will be published in the May issue of Public Library of Science Pathogens.

In chronic herpes virus infections, the body brings the invader under control, reducing its replication and spread, but is unable to completely eliminate it, resulting in lifelong infection.

The mice in the study were injected with murine gamma herpes virus 68, a herpes virus that infects mice and is closely related to the human gamma herpes viruses Epstein-Barr virus (EBV, the cause of mononucleosis) and Kaposi's sarcoma-associated herpes virus (KSHV, the cause of a form of cancer known as Kaposi's sarcoma). Other herpes viruses that infect humans include the alpha herpes viruses herpes simplex virus 1 and 2, which cause cold sores and genital herpes, and varicella zoster virus, which causes chickenpox. Infection with gamma herpes viruses such as EBV and KSHV increases the risk of some cancers, especially in persons with
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Contact: Michael Purdy
purdym@wustl.edu
314-286-0122
Washington University School of Medicine
26-May-2006