Study of recombinants derived from autochthonous influenza virus type A strains

Simultaneous inoculation of chick embryos with a standard laboratory influenza virus--A/PR8/34 (H0N1)--and with an autochthonous epidemic strain--belonging to the antigenic subtype A(H1N1) of A(H3N2), respectively--resulted in the isolation of two genetic recombinants, designated R1IVN (H1N1) and R2IVN (H3N2). Each recombinant was antigenically identical to its wild-type parent and exhibited a hemagglutinating titer in chick embryos about 4-fold greater than that of the autochthonous parental strain.