Role of substrains in persistent lymphocytic choriomeningitis virus infection.

Two plaque-type mutants, a wild strain MB(1), and a slow-growing non-plaque-forming variant of LCM virus were compared in L cell cultures. The cultures were monitored at biweekly intervals following infection for plaque-forming virus titre and cytoplasmic and membrane specific immunofluorescence of the cells. Different patterns were obtained in each case and the relevance of these results to LCM persistence is discussed. While the LM variant continually produced virus for 35 transfers, with a cycling titre, the SC variant stopped producing detectable virus after 30 transfers. Thereafter this culture remained fluorescent and resembled the one infected with the slow-growing variant. The degree of specific immunofluorescence of both continued to cycle. The MB(1) strain stopped producing virus after the 18th transfer.