Study On A Novel Enhancing Protein Of Autographa Californica Multicapsid Nucleopolyhedrovirus

In this report we desceibe Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) enhanced infectivity of Pseudaletia separata entomopoxvirus (PsEPV) in Mythimna separata larvae.The bioassay results showed that there were a 95.00% mortality of 3rd instar larvae perorally administered a mixture with a concentration of 1.0×10~4AcMNPV and 1.0×10~7 PsEPV per larva. No larvae died in a high concentration of AcMNPV(1.0×l0~7OBs) alone, however, a 46.33% mortality was-obtained with a concentration of PsEPV(1.0×l0~7OBs) per larvaWhen larvae were perorally treated with a mixture of 1.0×10~6spheroids adding polyhedra and virions, there were mortalities of about 41.67% and 36.67% in infection with PsEPV, respectively. But no infected larvae were obtained when the larvae were perorally administered with the same dosage as indicated above in PsEPV without polyhedrin or virions. The results indicated that the factors from AcMNPV polyhedra and virions were responsible for the enhancement.In order to ravel the enhancive mechanism of AcMNPV enhancing PsEPV, we fed the 5th instar larvae perorally with a concentration of 1.0 × 10~7 PsEPV, 1.0 × 10~4 AcMNPV and a mixture with a concentration of 1.0×10~7 PsEPV and 1.0 ×10~4 AcMNPV. Each concentration was treated for 30min, 8h and 36h respectively, and then the peritrophic membranes (PMs) of Mythimna separata were extracted for SDS-PAGE analysis. The results of SDS-PAGE indicated that when there was no change with PM proteins treated for 30min;when treated for 8h, the straps of 106.00kDa and 54.20kDa disappeared;when treated for 36h, the PM remained the same with treated for 8h. Obviously, the diversification in PM treated with PsEPV solely was light. But when PsEPV mixed with AcMNPV, the PM was seriously destroyed. When treated for 30min, the straps of 106.00kDa and 54.20kDa disappeared;when treated for 8h, the straps of 170kDa, 106.00kDa, 54.20kDa, 51.80kDa and 23.65kDa disappeared;when treated for 36h, the straps of 170kDa, 106.00kDa, 54.20kDa, 51.80kDa, 23.65kDa and 21.00kDa disappeared.PMs of healthy Mythimna separata were treated in vitro with a concentration of 1.0 × 10~4OBs AcMNPV/PM for 30min, 8h and 36h respectively.SDS-PAGE.analysis showedthat the straps of 170kDa, 106.00kDa, 54.20kDa, 51.80kDa and 21.00kDa disappeared. The in-vivo treated results were the same as the in-vitro.When Mythimna separate larvae were infected by a mixture of PsEPV and AcMNPV, the mortality of larvae was increased. It inferred that AcMNPV increased the infectivity of PsEPV by destroying the PM proteins of larvae.