Construction of a shortened autographa californica multiple nucleopolyhedrovirus genome as protein expression vector.

The baculovirus expression system (BEVS) is a powerful tool for protein production in insect cells, and the most widely used virus vector in the BEVS is Autographa californica multiple nucleopolyhedrovirus (AcMNPV), whose genome contains 155 open reading frames (ORFs), nearly half of which are nonessential for viral replication in vitro. Our previous studies have shown that deletion of some large nonessential fragments from the AcMNPV genome can significantly improve the efficiency of production of foreign proteins and that the viral vector can be shortened by more than 10 kb. Using a previously described shortened vector, four additional fragments containing multiple nonessential genes (ac58-61, ac110-114, ac116-119, and ac121-124) were removed from the AcMNPV genome, and the effects on baculovirus replication and foreign protein expression were examined. The results showed that deletion of one of the nonessential fragments did not affect virus replication. For the expression of foreign proteins, removal of ac110-114 and ac116-119 was beneficial for protein production, deletion of ac121-124 apparently did not affect protein production, and deletion of ac58-61 severely impaired protein expression. Simultaneous deletion of two fragments from the AcMNPV genome significantly influenced exogenous protein expression and/or virus replication. Finally, by injection into Spodoptera frugiperda larvae, it was shown that the three shortened AcMNPVs that had maintained their infectivity and ability to express foreign proteins in cultured cells also retained their infectivity in vivo. The three shortened baculovirus expression vectors obtained in this study were 127-129 kb in length, representing a further reduction of 1.4-2.3% in genome size compared to the previously shortened vector, further optimizing it for protein production in the BEVS.