Human trials with wild-type H1N1 and recombinant H3N2-H1N1 influenza A viruses of 1977-1978

Abstract

A series of trials was conducted in which wild-type A/USSR/90/77 (H1N1) influenza A virus and a few of its antigenic variants were inoculated into volunteers. Infections readily occurred in people of all ages who had initial low antibody titers, but clinical effects were generally mild in comparison with those of the previously tested subtypes, HON1, H1N1, H2N2 and H3N2. There was an inverse relationship between severity of symptoms and age of volunteers, although the incidence of virus excretion and of increase in anti-hemagglutinin was apparently not age related. Naturally occurring recombinant viruses with H3 hemagglutinin and 1 or more genes of A/USSR/90/77-like strains were studied in volunteers. These clones produced mild symptoms, providing evidence of an attenuating effect on H3N2 viruses by the substitution of some of its genes with the genes of an H1N1 virus.