Biochemical characteristics of fowl plague virus ts mutants

Five fowl plague virus ts mutants belonging to five different complementation groups were studied. In one mutant ( ts 131) the virion RNA-polymerase was defective in vitro at the nonpermissive temperature and the later stages of replication in vivo (synthesis of RNA, polypeptides, and RNP) were found to be defective. One of the mutants studied ( ts 5) under nonpermissive conditions showed no disorders in the function of virion RNA-polymerase or in vivo synthesis of RNA, polypeptides, functionally active hemagglutinin and neuraminidase or RNP production, however, no formation of infectious virions or virion-like structures occurred under these conditions. In three mutants ( ts 43, ts 166, and ts29) the virion RNA-polymerase was capable of functioning in vitro at the nonpermissive temperature but no RNA synthesis in vivo was observed when tested 4 hr after infection. In these mutants, synthesis of virus-specific polypeptides at nonpermissive and optimal temperatures under the conditions of the experiment was similar both qualitatively and quantitatively. Despite the fact that in the cells infected with ts 43, ts 166, and ts 29 mutants synthesis of both polypeptides hemagglutinin precursors was observed at the nonpermissive temperature, no functionally active hemagglutinin was produced under these conditions. The data are discussed with reference to the mechanisms of reproduction of orthomyxoviruses.