ENHANCED INFECTION OF A NUCLEAR POLYHEDROSIS-VIRUS IN LARVAE OF THE ARMYWORM, PSEUDALETIA-SEPARATA, BY A FACTOR IN THE SPHEROIDS OF AN ENTOMOPOXVIRUS

Spheroids of an entomopoxvirus (EPV) enhanced the infectivity of a nuclear polyhedrosis virus (NPV) for larvae of the armyworm, Pseudaletia separata. When larvae were perorally administered a mixture of the spheroids and polyhedra, there was a direct increase in the number of larvae infected with the NPV as the dose of the spheroids increased. A proteinaceous factor within the spheroid was responsible for the enhancement. The factor retained its enhancing activity when dissolved with a mixture of Na2CO3, sodium thioglycolate and EDTA. The supernatant fraction of solubilized spheroids, which had been obtained by centrifugation at 48,000g, was more active than the pellet fraction in enhancing the NPV infectivity. Further fractionation of the supernatant on a sephacryl column revealed that the enhancing activity was present in one of the three proteinaceous peaks. The factor was 38 kDa in molecular mass and serologically unrelated to a synergistic factor of a P. unipuncta granulosis virus in double-diffusion tests. The replication of the EPV was hampered by the NPV in multiple infections. © 1992.