The Serological Comparison of Strains of Influenza Virus

Abstract

The antigens of 8 strains of influenza virus were compared by a simple and economical complement-fixation technique in which drops on Perspex (transparent plastic) sheets replaced larger volumes of reagents in racks of tubes. By this means more extensive tests were made with a limited supply of material than by standard tube techniques. The specific antisera were prepared in mice, thus avoiding the elaborate isolation precautions neccessary for ferrets, and sera from large groups were pooled to minimize individual variations between animals. The antigens were standardized in terms of the amt. of complement fixed in the presence of excess homologous antiserum. The comparison of the strains is presented in the form of index numbers, ranging from 0 to 1; 1 represents complete identity of 2 strains, while the smaller numbers are taken to represent the degree of antigenic relationship between strains. Of the 6 strains examined which were isolated in different yrs., all were serologieally distinct though the 2 B strains were closely similar and 2 of the A strains were fairly closely related. On the other hand, the 3 strains of influenza A virus isolated in 1947, 2 in London and 1 in the U. S. A., were identical.