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-l, 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.
The Baculoviridae are a large family of enveloped DNA viruses exclusively pathogenic to arthropods. Baculoviruses have been extensively used in insect cell-based recombinant protein expression system and as biological pesticides. They have been deomostrated to be safe to mammals, birds and fish. Recently, baculoviruses has been shown to transduce different mammalian cells in spite of the fact that they cannot replicate in mammalian cells (11, 73, 76). This has resulted in the development of baculoviruses as mammalian expression systems and even as vestors for gene therapy.
Nucleopolyhedrovirus(NPV) is divided into Group I and Group II based on the phy-logenetic analysis.It has been reported that Group I NPVs such as Autographa californica multiple NPV(AcMNPV) can transduce mammalian cells,while Group II NPVs such as Helicoverpa armigera single NPV(HaSNPV) cannot.Here we report that AcMNPV was capable of stimulating antiviral ac-tivity in human hepatoma cells(SMMC-7721) manifested by inhibition of Vesicular Stomatitis virus(VSV) replication.In contrast,the HaSNPV and the Spodoptera exigua multiple NPV(SeMNPV) of group II had no inhibitory effect on VSV.Recombinant AcMNPV was shown to induce interferons al-pha/beta even in the absence of transgene expression in human SMMC-7721 cells,while it mediated transgene expression in BHK and L929 mammalian cells without an ensuing antiviral activity.
LIANG Changyong1,2,SONG Jianhua1,2,HU Zhihong1 & CHEN Xinwen1 1.State Key Laboratory of Virology,Wuhan Institute of Virology,Chinese Academy of Sciences,Wuhan 430071,China
