ABSTRACT
In order to improve the accuracy for quantitating the bovine foamy virus(BFV)in vitro,we developed a baby hamster kidney cell(BHK)-21-derived indicator cell line containing a plasmid that encodes the firefly luciferase driven by the BFV long terminal repeat promoter(LTR,from -7 to 1012). The BFV titer could be determined by detecting the luciferase expression since the viral trans-activator BTas protein activates the promoter activity of the LTR. One clone,designated BFVL,was selected from ten neomycin-resistant clones.BFVL showed a specific and inducible dose-and time-dependent luciferase activity in response to BFV infection.Although the changes in luciferase activity of BFVL peaked at 84 h post infection,it was possible to differentiate infected and uninfected cells at 48 h post infection. A linear relationship was established between the multiplicity of infection(MOI)of BFV and the activated ratio of luciferase expression in BFVL. Moreover,the sensitivity of the BFVL-based assay for detecting infectious BFV was 10,000 times higher than the conventional CPE-based assay at 48 h post infection. These findings suggest that the BFVL-based assay is rapid,easy,sensitive,quantitative and specific for detection of BFV infection.
ABSTRACT
In order to quantitate the bovine immunodeficiency virus (BIV) infection in vitro, a BIV indicator cell line (BIVL) was established by transfecting baby hamster kidney cells with reporter plasmids containing the firefly luciferase gene driven by a BIV long terminal repeat promoter. The BIV activates promoter activity of the LTR to express luciferase upon infection. BIV infection could therefore by quantified by detection of luciferase activity. Compared to standard assays used to detect BIV infection, the BIVL-based assay is 10 times more sensitive than the the CPE-based assay, and has similar sensitivity with the viral capsid protein Western blot assay. BIV indicator cell line could detect BIV infection specifically. Luciferase activity of BIV infected BIVL cells showed a time dependent manner, and 60 h post infection is the optimal time to detect BIV infection. Luciferase activity of BIVL cells correlates with the BIV capsid protein expression. Moreover, a linear relationship was found between MOI and the activated intensity of luciferase expression. In brief, the BIV indicator cell line is an easy, robust and quantitive method for monitoring BIV infection.