Transient impaired cell-mediated tumor immunity after acute infection with lymphocytic choriomeningitis virus.

Intraperitoneal injection of nononcogenic lymphocytic choriomeningitis (LCM) virus in adult C3H mice causes a symptomless infection but stimulates specific cell-mediated and humoral immune responses. However, median survival time of virus-infected mice inoculated with syngeneic tumor cells was significantly shortened, and growth of semiallogeneic tumors was significantly enhanced. Cell-mediated cytotoxicity measured as chromium-51 release from labeled tumor cells was significantly suppressed but was recovered within 55 days after infection. The suppressed immune responsiveness could be conferreo on a normal spleen cell population when activated in virus-infected recipients. Chronically LCM virus-infected mice showed an unimpaired cell-mediated immune response to tumor allografts.