In vitro host range of Autographa californica nucleopolyhedrovirus recombinants lacking functional p35, iap1 or iap2.

Abstract

We have examined the host range in different insect cell lines of Autographa californica nucleopolyhedrovirus (AcMNPV) recombinants lacking p35, iap1 or iap2. These genes encode, or are predicted to encode, anti-apoptotic proteins. Abrogation of p35 reduced the ability of AcMNPV to replicate in permissive cell lines derived from Spodoptera frugiperda insects by inducing apoptosis. In semi-permissive cell lines, such as Lymantria dispar and Spodoptera littoralis cells, we observed cytopathic effects after infection with AcMNPV but little virus production. Infection of these cells by AcMNPV lacking p35 resulted in apoptosis. However, p35-deficient viruses were still able to replicate normally in Trichoplusia ni, Mamestra brassicae and Panolis flammea cell lines. Disruption of AcMNPV iap1 and iap2 was found not to affect virus replication in any of the cell lines. It was also possible to disrupt both iap1 and iap2 in the same virus without loss of infectivity. A virus without iap1 and p35 demonstrated identical growth characteristics and host range to a virus lacking p35. We conclude that in cells which respond to AcMNPV infection by initiating programmed cell death, the p35 gene product alone is sufficient to inhibit apoptosis. Removal of iap1 or iap2 has no effect on virus replication, even in cell lines which do not undergo apoptosis in response to AcMNPV infection. Our results with two semi-permissive cell lines further indicate that whilst p35 is important in blocking block apoptosis, other factors are involved in restricting AcMNPV replication within these cells.

Silencing of the Baculovirus Op- iap3 Gene by RNA Interference Reveals that It Is Required for Prevention of Apoptosis during Orgyia pseudotsugata M Nucleopolyhedrovirus Infection of Ld652Y Cells

“…Op-iap3, like several other baculovirus iap genes, has been studied rather extensively outside of the context of infection by its native virus, but it had not been previously shown that any baculovirus iap gene is required to prevent apoptosis during a natural infection. Indeed, mutational analysis of the Ac-iap1 gene indicated that it is not required to prevent AcMNPVinduced apoptosis (21,39), although Ac-iap1 also lacks the ability to block apoptosis induced by other stimuli (14,27,31). Our findings demonstrate that Op-iap3 is important for preventing apoptosis during OpMNPV infection, indicating that other baculovirus iap genes that have the ability to block apoptosis outside of the context of virus infection are probably also required to prevent apoptosis during infection with their native virus.…”

Heliothis zea Nudivirus 1 Gene hhi1 Induces Apoptosis Which Is Blocked by the Hz-iap2 Gene and a Noncoding Gene, pag1

“…Since viruses should retain only genes that they need, it is interesting to speculate on the possible roles of these iap genes (9). In this paper, we found that iap2 of both HzNV-1 (8) and AcMNPV (3,15) can effectively suppress apoptosis induced by hhi1.…”

Identification and functional analysis of the putative anti-apoptotic gene iap4 of Spodoptera litura nucleopolyhedrovirus

“…One possibility is that the genes have some functions irrelative to apoptosis. When infected with baculoviruses, many insect cells, such as AcMNPV-infected Ld652Y cells [32] or SpltNPV-infected SpLi-221 cells, show evident cytopathic effects including cell rounding and clumping in contrast to normal cells. Another study showed that deletion of Ac-iap1 resulted in a competitive advantage for AcMNPV replication in a Trichoplusia ni cell line, but not in a S. frugiperda cell line [33].…”