Functional analysis of the Autographa californica nucleopolyhedrovirus IAP1 and IAP2

Abstract

The Autographa californica nucleopolyhedrovirus (AcMNPV) contains three apoptosis suppressor genes: p35, iap1 and iap2. AcMNPV P35 functions as a pancaspase inhibitor, but the function of IAP1 and IAP2 has not been entirely resolved. In this paper, we analyze the function of IAP1 and IAP2 in detail. AcMNPV with p35-deletion inhibited the apoptosis of BTI-Tn-5B1-4 (Tn-Hi5) cells induced by a Helicoverpa armigera single nucleocapsid NPV (HearNPV) infection and rescued the replication of HearNPV and BV production in these cells. Transient-expression experiments indicated that both IAP1 and IAP2 suppress apoptosis of Tn-Hi5 cells during HearNPV infection. Recombinant HearNPVs expressing AcMNPV iap1, iap2 and p35, respectively, not only prevented apoptosis but also allowed HearNPV to replicate in Tn-Hi5 cells. However, the iap1, iap2 and p35 genes when expressed in HearNPV were unable to rescue BV production. These results indicate that both AcMNPV iap1 and iap2 function independently as apoptosis inhibitors of and are potential host range factors.

Viral IAPs, then and now

“…Similarly, HycuNPV IAP-1 and -2 [36], as well as HearNPV IAP-2 [37] were also reported to lack anti-apoptotic activity. In contrast, both AcMNPV IAP-1 and IAP-2 were reported to be able to inhibit apoptosis induced by HearNPV in the T. ni cell line Tn-Hi5, which is resistant to most apoptotic signals [43]. EppoNPV IAP-2 was reported to block apoptosis in SF-21 cells, while IAP-1 from this virus delayed apoptosis [38].…”

Ubiquitins of Bombyx mori nucleopolyhedrovirus and Helicoverpa armigera nucleopolyhedrovirus show distinct subcellular localization in infected cells

“…One pathway regulates the process of viral DNA replication, since IE2 and PE38 act as stimulators for the DNA replication (Kool et al, 1994). Another one is associated with a host insect cell apoptosis, because IAP2 acts as an inhibitor of apoptosis (Zeng et al, 2009). Although much effort is paid to these processes, their mechanisms remain elusive.…”

Generating a host range-expanded recombinant baculovirus

“…The cell line TUAT-SpLi221 (SpLi-221) is derived from the tobacco cutworm ( S. litura )15. The BTI-Tn-5B1-4 (Hi5) cell strain is derived from the cabbage looper ( T. ni )1536. These cells were maintained at 27 °C in TNM-FH medium (Invitrogen Life Technologies) supplemented with 10% fetal bovine serum (FBS), penicillin (100 μg/ml), and streptomycin (30 μg/ml).…”