Immune therapy of a persistent and disseminated viral infection.

The mechanism of viral clearance was studied by using the mouse model of chronic infection with lymphocytic choriomeningitis virus. Distinct patterns of viral clearance and histopathology were observed in different organs after adoptive immune therapy of persistently infected (carrier) mice. Clearance from the liver occurred within 30 days and was accompanied by extensive mononuclear cell infiltrates and necrosis of hepatocytes. Infectious virus and viral antigen were eliminated concurrently. This pattern of viral clearance was also seen in most other tissues (i.e., lung, spleen, lymph nodes, pancreas, etc.). In contrast, a different pattern of clearance was observed in the brain. Infectious virus was eliminated within 30 days, but viral antigen persisted in the central nervous systems of treated carrier mice for up to 90 days. The urinary system was the most resistant to immune therapy. Elimination of infectious virus and viral antigen from the kidney took greater than 200 days and even then was not complete; trace levels of infectious virus were still present in the kidneys of some treated carrier mice. After immune therapy, viral antigen in the kidney was located within renal tubules that costained for intracellular mouse immunoglobulin G. This unusual staining pattern, coupled with the observation of large numbers of plasma cells within the kidney, suggests that virus-immunoglobulin G complexes found in the tubules may represent in situ immune complex formation as opposed to deposition of circulating immune complexes. In conclusion, these results suggest that the site (organ) of viral persistence is an important consideration in developing treatment strategies for controlling chronic viral infections.