[Neurotropic influenza type A viruses].

Influenza A/turkey/England/63 is neurotropic for mice. Substitution of the hemagglutinin gene of this virus by the corresponding gene of A/FPV/ Rostok /34 virus results in the loss of the neurotropic properties of the original virus. Examination of recombinants produced by hybridization of parental strains nonpathogenic (or weakly pathogenic) for newborn mice revealed recombinants highly virulent for this host. A correlation between constellation of genes and neurovirulence for mice was established. After intranasal administration neurovirulent viruses were shown to be able to penetrate into the brain of the infected animal along the trigeminal nerve escaping the blood stream.