Elimination of A7 MNRs of AcMNPV fp25k delayed FP development and improved virion occlusion

Background: Insect specific DNA baculoviruses have been widely used for biological control of insect pests to reduce cancers caused by chemical application in agriculture and forestry and as vectors for high yield exogenous protein expression. The most extensively studied and widely used baculovirus is the Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) due to its ability to replicate in many permissive cells with high virus titer. During serial passage of AcMNPV in permissive insect cells at high MOI, the fp25k mutates at a high frequency leading to the development of the few polyhedra (FP) phenotype with reduced polyhedra production and few virion occlusions in polyhedra resulting in poor infectivity to insects. Method and results: We used site-directed mutagenesis on wild type AcMNPV (AcP3) fp25k gene to eliminate these hypermutable sites and produced a recombinant virus AcP3-FPSDM and performed restriction fragment length polymorphism (RFLP, as well as Western blot analysis to understand virion occlusion efficacy. We compared fp25k stability between AcP3 and AcP3-FPSDM in Hi5 cells. Our experimental results showed that AcP3-FPSDM performed better in virion occlusion efficiency. Conclusion: We showed that AcP3-FPSDM is a better virus for researchers to apply in agriculture and forestry to reduce chemical usage, thus cancer cases.