Baculoviruses: Apoptosis Inhibitors

Abstract

The ability to inhibit apoptosis is important for many viruses to successfully replicate and be transmitted to new susceptible hosts. In particular, many DNA viruses including adenoviruses, herpesviruses, and poxviruses carry multiple genes that can inhibit apoptosis through different mechanisms. The arthropod-specific baculoviruses are no exception. Baculoviruses have been found to contain two types of apoptosis inhibitors, called p35 and iap (inhibitor of apoptosis) genes. Although p35 genes were discovered first, they are less common, having been identified in only a handful of baculoviruses (and recently, an entomopoxvirus). The iap genes are more widespread, with one or more iap genes being found in nearly all of the ∼30 baculovirus genomes sequenced to date, and in several other invertebrate viruses as well. P35 and IAP proteins inhibit apoptosis through different mechanisms, but both yield the same end result, which is keeping the host cell alive long enough for the baculovirus to complete its replication cycle. The expression of apoptosis inhibitors is important for baculovirus infectivity and virulence in the insect host.