Search

We have determined a major antigenic site for virus neutralization on the capsid protein VP1 of poliovirus type 3. Antigenic mutant viruses selected for resistance to individual monoclonal antibodies had point mutations concentrated in a region 277–294 bases downstream from the start of the region of viral RNA coding for VP1. These findings provide the basis for an improved understanding of the molecular basis of virus neutralization.

Influenza is unique among the viruses in its capacity to vary. Because of antigenic variation, it has proved impossible to control influenza by vaccination, and variation in virulence, host range and transmissibility influence the spread and severity of influenza epidemics. This variation is caused by sequence changes in the genes of the virus and this review summarizes recent information on the structure of the genes and their products, the way in which these vary and the effects of the changes on the biological activities of the virus.

INFLUENZA A viruses of human and avian origin have a common (type-specific), ribonucleoprotein antigen which is located in the virus particle. Haemagglutination-inhibition (HI) tests and strain specific complement-fixation (CF) tests on some eighty avian influenza strains studied at the World Influenza Centre, London1–3, indicated a wide range of antigenic variation in the antigens of their outer envelopes (subtype-specific antigens). Limited attempts to demonstrate antigenic similarities in the surface antigens of avian and human influenza viruses using similar tests produced negative results, with the exception of cross-reactions demonstrated between A2/Singapore/1/57 and A/turkey/Massachusetts/65 (refs. 4 and 5). Closer studies on the antigenic structure of these latter agents using neuraminidase-inhibition (NI) and immunoprecipitation tests6,7indicated that A/turkey/Massachusetts/65 virus contained a neuraminidase which was antigenically identical to that of the human A2 virus strain, whereas its haemagglutinin was unrelated to that of human influenza viruses. NI tests, immunoprecipitation tests as well as HI tests have thus been used in the study of avian influenza A viruses sent to this laboratory for identification. We describe here studies on a virus isolated from ducks in 1968 which indicated close antigenic similarities between its neuraminidase and that of human A0 and A1 virus strains.