A Genetic Approach to Variation in Influenza Viruses 4. Recombination of Characters Between the Influenza Virus A

SUMMARY: Mice were inoculated intracerebrally with mixtures of the influenza virus strain NWS and the serologically distinct non-neurotropic strains MEL, OcI and SW. From mouse brains removed about the 5th or 6th day virus strains were obtained which, after at least two passages at limiting infective dilution, showed active encephalitogenic power with the serological character of the second strain of the original mixture. These are regarded as recombinants. The strains in general show in vitro characters close to those of the serologically similar ‘parent’. They have, however, diminished enzymic action on ovomucin and do not readily elute from red cells; in this they resemble the strain NWS. They are more readily converted to the indicator state than either of the original strains. The process by which these unusual types arise is discussed in the light of recent views that intracellular multiplication of bacterial viruses and of some animal viruses takes place not by binary fission but by the breaking down of the infective unit into smaller particles which are the replicating units. It is concluded that the recom-binants arise by reconstitution of infective particles from the pool of replicatin