Helen H. Ho

Observations on Antigenic Variants of Echovirus Type 11.

Summary Strains of echovirus type 11 isolated in this laboratory since 1962 appear to have a broader antigenic spectrum than the prototype Gregory strain. The isolates were neutralized to low titer or not at all by immune serum to the Gregory strain, but immune serum to a representative isolate (Silva) neutralized both the prototype and homologous strains, as well as the other isolates. Results of cross hemagglutination inhibition and complement fixation tests, as well as im-munodiffusion tests, confirmed the relationship of these isolates to echovirus type 11. Sera of patients from whom the antigenic variants were recovered showed significant neutralizing antibody responses to both the prototype echovirus type 11 strain and the Silva “prime” strain.

ANTIGENIC RELATIONSHIP BETWEEN ECHOVIRUS TYPES 29 AND 32.

Summary An antigenic relationship has been demonstrated between the newly classified echovirus types 29 and 32. The amount of crossing seen in conventional tube neutralization tests was relatively minor, but fairly high reciprocal titers were observed in plaque reduction neutralization tests. In cross hemagglutination-inhibition and complement fixation tests these two viral types were virtually indistinguishable. The question arises as to whether these two new echovirus types should be classified as distinct immunotypes or whether they represent antigenic variants of a single viral type.