MUTANTS AND REVERTANTS OF AN AVIAN INFLUENZA-A VIRUS WITH TEMPERATURE-SENSITIVE DEFECTS IN THE NUCLEOPROTEIN AND PB2

ts19 is a temperature-sensitive (ts) mutant of the influenza A fowl plague virus with a defect in the nucleoprotein (NP). In ts19-infected chicken embryo cells all viral components are synthesized in normal yields at the nonpermissive temperature, but infectious virus is not formed. Under these conditions the migration of the NP and M of tsl9 from the cell nucleus to the cytoplasm is affected. This is defect is due to a single amino acid replacement (R162K) in a completely conserved region of the NP. Another mutant with a different defect in the NP is ts81. After infection with ts81 at 40° no vRNA is being synthesized. By backcross of a revenant derived from ts81 many isolates with a is defect in the PB2 protein were obtained. This is defect seems to extragenically suppress the is defect in the NP gene and to be dominant in a wild-type background. © 1991.