Some biological and serological properties of large and small plaque variants of Getah virus.

Two plaque types of Getah virus were isolated on BHK-21 cells from an emulsion of suckling mouse brain infected with strain AMM-2021 and were designated as large plaque (LP) and small plaque (SP) strains. Some of the properties of LP and SP strains were studied with the following results. The difference in plaque size of the LP and SP strains was quite distinct on BHK-21 cells and there was little difference in size at the 3rd--8th serial passage level in suckling mouse brain. The LP strain showed high hemagglutinating activity but the SP strain produced no detectable HA activity. The LP strain was shown to be more virulent than the SP strain to suckling mice by intracerebral or intraperitoneal inoculation. The LP strain was not neutralized as effectively as the SP strain with antisera to original, LP and SP strains. An enhancement of infectivity was observed when the LP strain was senstized with either anti-LP or anti-SP hyerimmune mouse sera. This phenomenon was not pronounced withe the SP strain.