Baculovirus per os infectivity factors are involved in HearNPV ODVs infection of HzAM1 cells in vitro

Baculoviruses produce two viral phenotypes, the budded virus (BV) and the occlusion-derived virus (ODV). ODVs are released from occlusion bodies in the midgut where they initiate a primary infection. Due to the lack of an in vitro system, the molecular mechanism of ODV infection is still unclear. Here we present data demonstrating that Helicoverpa armigera nucleopolyhedrovirus (HearNPV) ODV infected cultured Hz-AM1 cells in a pH dependent manner. The optimal pH for ODV infection was 8.5, which is same to that in the microvilli of midgut epithelial cells, the ODV native infection sites. Antibodies neutralization analysis indicated that four HearNPV oral infection essential genes p74, pif-1, pif-2 and pif-3 are also essential for HearNPV ODV infection in vitro. Thus, HearNPV-HzAM1 system can be used to analyze the mechanism of ODV entry. Foundation items: National Nature Science Foundations of China (30325002, 30470075); National Basic Research Priorities Program of China (2003CB1140).