The inhibitor of apoptosis gene (iap-3) of Anticarsia gemmatalis multicapsid nucleopolyhedrovirus (AgMNPV) encodes a functional IAP.

Programmed cell death or apoptosis is one of the defense mechanisms used by insect cells in response to baculovirus infection. Baculoviruses harbour antiapoptotic genes to prevent apoptosis and to maintain the normal course of infection. In this work, we showed that, like other baculoviruses, Anticarsia gemmatalis multicapsid nucleopolyhedrovirus (AgMNPV) has a functional inhibitor of apoptosis gene (iap-3). The iap-3 gene was cloned, sequenced and its transcription confirmed by RT-PCR. The putative iap-3 gene of the baculovirus AgMNPV has 864 nucleotides and codes an ORF of 287 amino acids. We have found two BIR motifs (baculoviral iap repeats) at the amino-terminal region and a carboxi-terminal RING finger motif. The IAP-3 protein of AgMNPV is closely related to IAP-3 proteins of baculoviruses and lepidopteran IAPs, with most amino acid identity (75%) with the IAP-3 protein of CfDefNPV (Choristoneura fumiferana DEF nucleopolyhedrovirus). Transcriptional analysis of the AgMNPV iap-3 gene showed that iap-3-specific transcripts could be detected early and late in the infection. The iap-3 gene of AgMNPV was shown to encode a functional IAP since insect cells transfected with increasing amounts of a plasmid containing the iap-3 of AgMNPV showed increased resistance to apoptosis induced by a AgMNPV mutant virus.

Production of viral progeny in insect cells undergoing apoptosis induced by a mutant Anticarsia gemmatalis nucleopolyhedrovirus.

The Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) is the most successful viral biopesticide in use worldwide. We have demonstrated that despite widespread apoptosis and no protein synthesis at 48 h p.i., UFL-AG-286 cells infected with a mutant of AgMNPV (vApAg), produced significant amounts of budded virus (BVs) and viral DNA late in infection. However, a different susceptible cell line (BTI-Tn5B 1-4) showed no signs of apoptosis and produced 3.5 times more budded virus when infected with vApAg. A comparison of DNA from AgMNPV and vApAg digested with the same restriction enzymes showed differences in the restriction pattern, indicating that the vApAg phenotype might be due to a mutation in a gene or genes responsible for directly or indirectly inhibiting apoptosis in UFL-AG-286 cells.