Radiation Prolongs, Activates Viral Infections
Gamma radiation can prolong viral infections and even reactivate viruses in mice, demonstrating that the effect of such exposures on the immune system will have important implications for space flight, said Baylor College of Medicine scientists working as part of the National Space Biomedical Research Institute in a report in this month's issue of the Journal of Allergy and Clinical Immunology.
Predicting immune responses in space flight is one of the important long-term goals of preparing for interplanetary travel because the immune system protects organisms from infection and cancer, said Dr. William T. Shearer, professor of pediatrics at Baylor.
In this study, he and colleagues show that an initial dose of gamma irradiation in mice prolongs a primary infection with murine polyoma virus and a second dose of radiation, two months later, reactivates the virus from latency. Immune studies of the animals' spleen cells show radiation decreases the proliferation of T lymphocytes and decreased production of the virus fighting cytokine protein, interferon gamma, demonstrating that when radiation weakens immune response, replication of primary and latent virus infection occurs. The same situation occurs when humans harboring latent virus receive immunosuppressants or radiation as treatment.
Using this method of quantitating the amounts of radiation and virus infection in animals, it may be possible to predict the degree of immunosuppression that leads to reactivation of latent virus infections and possibly the appearance of latent virus-driven malignancies in humans in space.
HOUSTON - (June 15, 2005)