[Studies on the adaptation of various strains of orthomyxovirus type A, subtype A/equi 2, passaged either on bovine kidney cells or on chicken fibroblasts or on RK-13 cells or by those passages alternating with "in ovo" passages].

The Authors have researched to adapt Orthomyxovirus, subtype A/equi-2 (Naples/213/67, Andria/60/68 and Miami/63), by serial passages on kidney calf cells, chick embryo cells and RK-13 cell line or by one or two passages on these colture media alternated with one passage "in ovo". The results obtained show that only kidney calf cells are most suitable because the viruses replicate for eleven passages. On the chick embryo cells and RK-13 cell line the viruses replicate only for two passages and these results are not modified when one or two passages are alternated with one passage "in ovo". The Authors have observed the production of infectious but not haemadsorbing and haemagglutining virus. The phenomenon is discussed and integrated with collateral tests.