Expression of the Cydia pomonella granulovirus matrix metalloprotease enhances Autographa californica multiple nucleopolyhedrovirus virulence and can partially substitute for viral cathepsin

- Cydia pomonella granulovirus matrix metalloprotease (CpGV-MMP) is a functional enzyme in vitro.
- CpGV-MMP expressed from AcMNPV promotes larval melanization.
- AcMNPV expressing CpGV-MMP caused accelerated mortality of insect larvae.

The Cydia pomonella granulovirus open reading frame 46 (CpGV-ORF46) contains predicted domains found in matrix metalloproteases (MMPs), a family of zinc-dependent endopeptidases that degrade extracellular matrix proteins. We showed that CpGV-MMP was active in vitro. Autographa californica multiple nucleopolyhedrovirus (AcMNPV) expressing CpGV-ORF46 replicated similarly to a control virus lacking CpGV-ORF46 in cultured cells. The effects of AcMNPV expressing CpGV-MMP on virus infection in cultured cells and Trichoplusia ni larvae in the presence or absence of other viral degradative enzymes, cathepsin and chitinase, were evaluated. In the absence of cathepsin and chitinase or cathepsin alone, larval time of death was significantly delayed. This delay was compensated by the expression of CpGV-MMP. CpGV-MMP was also able to promote larvae melanization in the absence of cathepsin and chitinase. In addition, CpGV-MMP partially substituted for cathepsin in larvae liquefaction when chitinase, which is usually retained in the endoplasmic reticulum, was engineered to be secreted.