Study of coxsackievirus group A. I. Serological variation of coxsackieviruses group A isolated in Gifu Prefecture

: Forty four isolated strains of Coxsackievirus group A were tested for antigenic variation with antiserum against each prototype strain by neutralization test. Isolates of type 2, type 4, type 5, type 8 and type 10 of Coxsackievirus group A, were not confirmed antigenic variation by neutralization test with immune sera to the prototype virus strain. However, 57.1% of type 9 isolates of Coxsackievirus A group were confirmed as variants. In isolates of Coxsackievirus group A type 16, the isolate in 1982 was neutralized with antiserum against the prototype strain, but the isolates after 1984 were neutralized to low titer or not at all by immune sera to the prototype virus strain. Therefore, the isolated strains were tested with immune sera against the isolated strain in 1988. So that, the isolated strains in 1982 and after 1984, were neutralized with the serum against the isolate in 1988, and moreover, the neutralizing titer of prototype strain was a third of the isolate. So that, for identification of type 16 of Coxsackievirus group A, it is necessary to use the immune sera against recently isolated strains.