ABSTRACT
Defective interfering (DI) particles of Indiana serotype of vesicular stomatitis virus (VSVInd) are capable of interfering with the replication of both homotypic VSVInd and heterotypic New Jersey serotype (VSVNJ) standard virus. In contrast, DI particles from VSVNJ do not interfere with the replication of VSVInd standard virus but do interfere with VSVNJ replication. The differences in the interfering activities of VSVInd DI particles and VSVNJ DI particles against heterotypic standard virus were investigated. We examined the utilization of homotypic and heterotypic VSV proteins by DI particle genomic RNAs for replication and maturation into infectious DI particles. Here we show that the RNA-nucleocapsid protein (N) complex of one serotype does not utilize the polymerase complex (P and L) of the other serotype for RNA synthesis, while DI particle genomic RNAs of both serotypes can utilize the N, P, and L proteins of either serotype without serotypic restriction but with differing efficiencies as long as all three proteins are derived from the same serotype. The genomic RNAs of VSVInd DI particles assembled and matured into DI particles by using either homotypic or heterotypic viral proteins. In contrast, VSVNJ DI particles could assemble only with homotypic VSVNJ viral proteins, although the genomic RNAs of VSVNJ DI particles could be replicated by using heterotypic VSVInd N, P, and L proteins. Thus, we concluded that both efficient RNA replication and assembly of DI particles are required for the heterotypic interference by VSV DI particles.