PERSISTENT ANTIGENIC VARIATION OF INFLUENZA A VIRUSES AFTER INCOMPLETE NEUTRALIZATION IN OVO WITH HETEROLOGOUS IMMUNE SERUM

TLDR

Influenza A virus strains generate antigenic variants when serially passaged in eggs in the presence of heterologous immune serum. The authors demonstrate that both the long‑passaged PR8 strain and recent isolates can be readily engineered into antigenic variants by serial egg passage with heterologous immune serum, that these variants retain their new antigenic patterns after passage without serum, and that passage without serum or with non‑cross‑reactive serum fails to produce variants.

Abstract

Antigenic variants of influenza A virus strains emerge on serial passage in ovo in the presence of immune serum against different but related strains. An old laboratory strain (PR8) which had been through hundreds of animal passages was as readily modified by this procedure as recently recovered strains. Such variants apparently can be obtained at will and show antigenic patterns which are reproducible and appear to be predictable in terms of the immune serum used for their selection. Variant strains retain their new antigenic patterns on serial passage in ovo in the absence of immune serum. Limited serial passage in ovo of strains in the absence of immune serum did not result in the emergence of antigenic variants. Similarly, serial passages of strains in ovo in the presence of immune serum against widely different strains, which failed to show significant cross-neutralization, did not lead to the appearance of antigenic variants.