Construction Of Bovine Foamy Virus Infectious Clone And The Function Of Accessory Proteins

Foamy viruses (FVs), also as known as spumaretroviruse, compose the only genus in the Spumaretrovirinae subfamily of Retroviridae. FVs are type of complex viruses with similar genome construction as human immunodeficiency virus type1(HIV-1) and human T-cell leukemia virus (HTLV). Within the field of FVs, most research focus on simian foamy virus, and few on non-simian foamy virus which mainly associated with feline foamy virus (FFV) and bovine foamy viurs (BFV).BFV strain3026(BFV3026) was isolated from the peripheral blood mononuclear cells of an infected cow by our lab in Zhangjiakou, China. In order to obtain more information on BFV research, the full-length clone of BFV3026was constructed using the viruses which were cultured for several years in our lab. Then the factors that might affect the replication ability of BFV was discussed; In addition, the function of the accessory proteins of BFV, BTas and BBet, were briefly characterized in this study; At last, cell-free supernatant BFV was passaged in BFV indicator cell line (BICL) which was hopefully to be used in the research of BFV molecular biology.The results of this study are remarkable:1. The viral genomic DNA is extracted from the Cf2Th cells which infected with BFV3026, and the proviral full-length genomic DNA clone (pBS-BFV) is constructed;2. It is reported that the transactivation ability of BTas is important for the replication of pBS-BFV; The amino acid (aa) at position108is important in DNA binding domain of BTas. It could obviously enhance the interaction between BTas and the Tas response element when the Asp108was changed into Asn, and the same as the transactivation ability of BTas, without any effect on the subcellular location, homodimerization or the activation ability in NF-κB signaling pathway;3. BFV3026was adapted to cell-free transmission (～1×104TCID50/mL) using BICL cells by serial passage with cell-free culture supernatant;4. There is BBet protein expression during BFV3026infection, and it is shown that BBet could negatively regulate BFV3026replication. Collectively, in this study, we successfully obtain the full-length DNA infectious clone of BFV3026with higher replication ability and the cell-free BFV3026particles, which prepare good materials for the further research of BFV3026molecular biology; The functions of BFV3026acessary proteins, BTas and BBet, during virus infection are briefly characterized, which will help us learn more about the relationship between foamy virus and the hosts.