Encapsidating artificial human papillomavirus-16 mE7 protein in human papillomavirus-6b L1/L2 virus like particles

Background Human papillomaviruses （HPVs） can infect squamous or mucosal epithelia and cause cervical cancer or genital warts. Coinfection with multiple HPV types is a common finding of many epidemiological studies. Therefore, it is necessary to develop a vaccine, which can eradicate established HPV infections and prevent other HPV infections. In this study, we generated chimeric virus like particles （cVLPs） composed of HPV-6b L1, HPV-6b L2 and one artificial HPV-16 mE7 proteins. Methods The artificial HPV-16 mE7 gene was designed by codon modification, point mutation and gene shuffling then chemically synthesized and subcloned behind HPV-6b L2. HPV-6b L1 and L2-mE7 were expressed in insect cells by using Bac-to-Bac system. The generated cVLPs were purified by CsCI gradient ultracentrifuge and analyzed by immunoblot, electron microscope and haemagglutination assay. Results The HPV-6b L1 and L2-mE7 proteins were well expressed in insect cells and could selfassemble into cVLPs, whose diameter was about 55 nm and similar to that of HPV-6b L1/L2 VLPs. Intact cVLPs could be recognized by H6.M48 neutralizing monoclonal antibody and HPV-6b L2 polyclonal antibody, while the denatured cVLPs, but not the intact cVLPs, were reactive to HPV-16 E7 polyclonal antibody. HPV-6b LI/L2-mE7 cVLPs haemaggiutinated mouse erythrocytes as efficiently as HPV-6b L1/L2 VLPs did. Conclusions The insertion of the 158 amino acid HPV-16 mE7 protein behind L2 did not disrupt the correct assembling of cVLPs. The morphological characteristics and haemagglutinating activity of cVLPs were similar to those of HPV-6b LI/L2 VLPs. The cVLPs retained conformational B cell epitopes of HPV-6 VLPs and HPV-16 mE7 protein had an internal location in the cVLPs. Therefore, large modified E7 protein with higher immunogenicity could be incorporated into cVLPs by fusing to the C-terminus of L2, which would help to improve the therapeutic effects of LI/L2-E7 cVLPs.

Construction and Production of FluorescentPapillom avirus-like Particles

The green fluorescent protein (GFP) from the jellyfish Aequorea victoria has attracted widespread interest since it was demonstrated to be fluorescent in vivo when expressed in other organisms. In order to investigate papillomavirus life cycle which hampered by the unavailability of conventional cell culture system, we constructed a chimeric bovine papillomavirus (BPV) type 1 virus like particles (VLPs) containing GFP. It was found that fluorescent VLPs could be assembled from L2 protein in which GFP is inserted into the N terminal region of L2 (aa 88). The fluorescent VLPs could also be assembled from a GFP/L2 fusion protein in which part of the L2 sequence had been deleted. In vitro , fluorescent VLPs could bind to CV 1 cells, and this VLP/cell interaction could be analyzed by FACS assay. These results demonstrated that GFP could incorporate into BPV1 VLPs without disruption of the VLP structure. Fluorescent VLPs might be a useful tool for study of papillomavirus virus/cell interaction.

Expression and self-assembly of HCV structural proteins into virus-like particles and their immunogenicity

Background The synthesis of virus-like particles (VLPs) provides an important tool to determine the structural requirements for viral particle assembly and virus-host interactions. Our purpose was to express simultaneously all three structural proteins of hepatitis C virus (HCV) in insect cells to investigate the proteins assembly into VLPs and the immunogenicity of these particles KH*2/5DMethods HCV gene sequences encoding the structural proteins C, E1, and E2 were amplified with PCR, and recombinant baculoviruses were constructed using recombinant DNA techniques The expression of HCV structural proteins in insect cells was analyzed by immunofluoresceoce and SDS-PAGE The interaction of expressed structural proteins was investigated by immunoprecipitation and immunoblotting The VLPs in the insect cells were visualized by electron microscopy (EM) VLPs were then purified by sucrose gradient centrifugation and used to immunize BALB/c mice Antibodies against HCV were tested for in mouse serum samples by an ELISA assay Results The recombinant baculoviruses reBV/C and reBV/E1-E2 were constructed successfully Insect cells co-infected with reBV/C and reBV/E1-E2 expressed HCV C, E1, and E2 proteins with the expected molecular weights of 20kD, 35kD, and 66kD, respectively The results of immunoprecipitation and immunoblotting assays revealed the coimmunoprecipitation of C, E1, and E2 proteins, indicating association of the three structural proteins Electron microscopy of insect cells co-infected with reBV/C and reBV/E1-E2 demonstrated spherical particles (40 to 60 nm in diameter) similar to the HCV virions from serum samples or hepatic tissue samples of HCV infected humans The VLPs were partially purified Antibodies to HCV were detectable in the serum of mice immunized with VLPs Conclusion HCV structural proteins simultaneously expressed in insect cells can interact with each other and assemble into HCV-like particles, which are shown to be immunogenic in mice