Histopathology of Lymphocytic Choriomeningitis in Mice Spared by Amethopterin

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Abstract
Mice infected with lymphocytic choriomeningitis (LCM) virus in intracerebral doses which were otherwise universally fatal were spared by the intraperitoneal administration of amethopterin. Detailed histological examinations and virus titrations were performed on such spared animals at intervals ranging from 5 to 57 days. Greatly modified objective evidence of disease was found in the majority of 34 animals examined. In the acute 5-20 day stage, 82% of mice showed no disease or extremely modified lesions of LCM. In the chronic 21-57 day stage, 33% showed similarly modified LCM. The remaining mice in both groups showed lesions of active LCM, even as late as 56 days after inoculation. Practically all spared mice gave evidence of multiplication of the virus in the central nervous system. The treatment appeared to delay, rather than suppress the inflammatory reaction. Amelioration of the pathological process was not essential for survival, and the sparing effect was not attributable to eradication or diminution of the virus in the central nervous system. It appeared more probable that the effect was due to interference with cellular or humoral responses of the host, rather than to modification of viral activity.