Establishment and application of human papillomavirus type 16 pseudovirions neutralization assay / 生物工程学报

Human papillomaviruses (HPV) are causally associated with cervical cancer and genital warts. Lack of permissive and productive cell cultures for HPV has hindered the study of HPV and evaluation of virus-neutralizing antibodies. So generation of infectious virions in vitro is highly desirable. In this report, we got high titer infectious HPV16 pseudovirions by calcium phosphate co-transfection of codon optimized HPV16 capsid genes L1 and L2 and reporter plasmids into 293FT cell line. Electron micrograph indicated that the pseudovirions were morphologically similar with the intact HPV16 virions. To evaluate the feasibility of using the pseudovirions to identify neutralizing monoclonal antibodies (mAbs), pseudovirions were incubated with 2-fold gradient dilution of the well identified mAbs V5, E70, U4 and D9 and then used to infect 293FT cells preplated in 96-well tissue culture plate. The infection of pseudovirions could be inhibited by neutralizing mAbs V5, E70 and U4 that recognize surface conformational epitopes on L1 VLP, but not by mAb D9 that is reactive to a linear epitope buried in VLP, which indicated that the pseudovirions could be used to evaluate the neutralization efficiency of mono- and polyclonal antibodies. The pseudovirions were then employed to identify neutralizing mAbs from 18 mAbs generated previously in our lab, 8 of which were conformational and 10 were linear. PD1 and 3D10, both of which recognized conformational epitopes on L1 VLP, had obviously strong neutralizing efficiency, with the neutralizing titer reached 81,920 and 20,480 respectively, while none of the linear mAbs were neutralizing, which reflected that rare linear mAbs have neutralization activity. The mechanism of PD1 and 3D10 block the infection of HPV16 pseudovirions need to be further studied. The technologies about generation of HPV16 pseudovirions and screening neutralizing mAb in our report are economical and efficient, can be easily used in large scale. They pave the way for rapid and precise evaluation of the protection efficiency of our prophylactic HPV vaccine being developed now.

Mammalian gene-transfer and expression efficiencies of baculovirus bacV-CMV-EGFPA / 生物工程学报

It has been reported that baculoviruses could serve as a new gene-transfer vehicle for mammalian cells. We have previously constructed recombinant baculovirus BacV-CMV-EGFPA and have proven that mammalian cells could be effectively infected by the recombinant baculovirus. In this report, we studied the efficiency of baculovirus to deliver exogenous gene into twenty mammalian cells, including twelve human cell lines (WI-38, Hela, HepG2, 293, PLC/PRF/5, 143B, MCF-7, BGC-223, DMS 114, CNE, Raji, LCL-cm), seven murine cell lines (BNL 1ME A.7R.1, CHO-K1, L-929, JC, PT67, NIH3T3, P815) and one monkey cell line (CV1). Results showed that most mammalian cell lines could be transduced by the recombinant baculovirus, the transduction efficiencies of the human and monkey cell lines were markedly higher than that of murine cell lines, and the transduction efficiencies in adherent culture cell lines higher than that of suspend culture cell lines, implying that the infection efficiency of the baculovirus may be correlative with the organism used and the growth properties of the cell lines. The plasmid pcDNA3. 1-EGFP, which contains the CMV promoter and EGFP reporter gene, was next transfected by LipofectAMINE into a number of mammalian cells, especially those cells that were low in the baculovirus transfection. Results showed that the CMV promoter could effectively direct the expression of the reporter gene in these mammalian cells. Therefore the gene-expression efficiencies in different mammalian cell lines by the recombinant baculovirus which contains the same CMV promoter were dictated by the ability of the baculovirus to enter the cell lines. This study suggested that the recombinant baculovirus vector is more suitable for gene expression in primate adherent culture cells than in murine cells and suspend culture cells.