CORRELATION OF PATHOGENICITY AND GENE CONSTELLATION OF INFLUENZA-A VIRUSES .2. HIGHLY NEUROVIRULENT RECOMBINANTS DERIVED FROM NON-NEUROVIRULENT OR WEAKLY NEUROVIRULENT PARENT VIRUS-STRAINS

Mixed infections with various nonneurovirulent or weakly neurovirulent influenza A strains yielded recombinants that were highly neurovirulent for mice. A correlation was detected between gene constellation and neurovirulence of these recombinants. For the recombination pair FPV/A2-England the Pol 1 and Ptra genes had to be derived from the human strain; while the HA and/or M gene has to be from FPV in order to obtain highly neurovirulent recombinants. For the FPV/PR8 pair only the Pol 1 gene needs to be derived from PR8 while the HA gene had to be from FPV in order to get highly neurovirulent recombinants. The derivation of the other genes does not appear to be important in this respect. Recombinants between FPV and the A2-Singapore influenza strain do not exhibit significant neurovirulence suggesting that at least one parent strain should be adapted to grow in mice in order to obtain neurovirulent recombinants. In addition, there is a correlation between pneumovirulence and growth in mouse kidney cells, but neurovirulence for mice and pathogenicity for chickens was not correlated. The data presented here demonstrate in principle the possiblity of an increase in pathogenicity in recombinants derived from less or nonpathogenic parent viruses. © 1979.