title: Yeast coexpression of human papillomavirus types 6 and 16 capsid proteins.
abstract: The L1 and L2 capsid proteins of animal and human papillomaviruses (HPVs) can self-assemble into virus-like particles (VLPs) that closely resemble native virions. The use of different animal models shows that VLPs can be very efficient at inducing a protective immune response. However, studies with infectious HPV virions and VLPs of different HPV types indicate that the immune response is predominantly type-specific. We have generated a diploid yeast strain that coexpresses the L1 and L2 capsid proteins of both HPV-6b and HPV-16, and we have purified fully assembled VLPs banding in a cesium chloride gradient at the expected density of 1.29-1.3 mg/ml. Experimental evidence strongly indicated that the four proteins coassembled into VLPs. Western blot analysis, using anti-HPV-6 and anti-HPV-16 L1-specific monoclonal antibodies and type-specific L2 antisera, demonstrated that all four proteins copurified. Most importantly, immunoprecipitation experiments, carried out using type-specific anti-L1 monoclonals and either total yeast cell extracts or purified VLPs, confirmed the interaction and the formation of covalent disulfide bonds between the two L1 proteins. Finally, HPV-6/16 VLPs administered to mice induced conformational antibodies against both L1 protein types. These results suggest that coexpression of different capsid proteins may provide new tools for the induction of antibodies directed against multiple HPV types.
authors.affiliation: Department of Molecular Biology, IRIS, Chiron S.p.A., Via Fiorentina 1, 53100 Siena, Italy.
authors.forename: Daniela Tornese
authors.initials: DT
authors.lastname: Buonamassa
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Greer
authors.forename: Sabrina
authors.initials: S
authors.lastname: Capo
authors.forename: T S Benedict
authors.initials: TS
authors.lastname: Yen
authors.forename: Cesira L
authors.initials: CL
authors.lastname: Galeotti
authors.forename: Giuliano
authors.initials: G
authors.lastname: Bensi
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002213:Capsid / Q000235:genetics* / Q000276:immunology; D036022:Capsid Proteins; D002586:Cesium; D002712:Chlorides; D005260:Female; D015870:Gene Expression; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009856:Oncogene Proteins, Viral / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D027383:Papillomaviridae / Q000276:immunology; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D014170:Transformation, Genetic; D014764:Viral Proteins; D019065:Virus Assembly
chemical_list: D036022:Capsid Proteins; D002712:Chlorides; D009856:Oncogene Proteins, Viral; D014764:Viral Proteins; D002586:Cesium; C091560:L1 protein, Human papillomavirus type 6; C063317:L1 protein, Human papillomavirus type 16; C028019:cesium chloride