title: Chimeric L1-L2 virus-like particles as potential broad-spectrum human papillomavirus vaccines.
abstract: The amino (N) terminus of the human papillomavirus (HPV) minor capsid protein L2 can induce low-titer, cross-neutralizing antibodies. The aim of this study was to improve immunogenicity of L2 peptides by surface display on highly ordered, self-assembled virus-like particles (VLP) of major capsid protein L1, and to more completely characterize neutralization epitopes of L2. Overlapping peptides comprising amino acids (aa) 2 to 22 (hereafter, chimera or peptide 2-22), 13 to 107, 18 to 31, 17 to 36, 35 to 75, 75 to 112, 115 to 154, 149 to 175, and 172 to 200 of HPV type 16 (HPV16) L2 were genetically engineered into the DE surface loop of bovine papillomavirus type 1 L1 VLP. Except for chimeras 35-75 and 13-107, recombinant fusion proteins assembled into VLP. Vaccination of rabbits with Freund's adjuvanted native VLP induced higher L2-specific antibody titers than vaccination with corresponding sodium dodecyl sulfate-denatured proteins. Immune sera to epitopes within residues 13 to 154 neutralized HPV16 in pseudovirion neutralization assays, whereas chimera 17-36 induced additional cross-neutralization to divergent high-risk HPV18, -31, -45, -52, and -58; low-risk HPV11; and beta-type HPV5 (titers of 50 to 10,000). Aluminum hydroxide-monophosphoryl lipid A (Alum-MPL)-adjuvanted VLP induced similar patterns of neutralization in both rabbits and mice, albeit with 100-fold-lower titers than Freund's adjuvant. Importantly, Alum-MPL-adjuvanted immunization with chimeric HPV16L1-HPV16L2 (peptide 17-36) VLP induced neutralization or cross-neutralization of HPV16, -18, -31, -45, -52, and -58; HPV6 and -11; and HPV5 (titers of 50 to 100,000). Immunization with HPV16 L1-HPV16 L2 (chimera 17-36) VLP in adjuvant applicable for human use induces broad-spectrum neutralizing antibodies against HPV types evolutionarily divergent to HPV16 and thus may protect against infection with mucosal high-risk, low-risk, and beta HPV types and associated disease.
authors.affiliation: Laboratory of Viral Oncology, Division of Immunology, Allergy and Infectious Diseases, Department of Dermatology, Medical University Vienna, Austria.
authors.forename: Christina
authors.initials: C
authors.lastname: Schellenbacher
authors.forename: Richard
authors.initials: R
authors.lastname: Roden
authors.forename: Reinhard
authors.initials: R
authors.lastname: Kirnbauer
mesh_terms: D000818:Animals; D016367:Baculoviridae / Q000378:metabolism*; D002213:Capsid / Q000737:chemistry; D036022:Capsid Proteins / Q000378:metabolism*; D000939:Epitopes / Q000737:chemistry; D051379:Mice; D008807:Mice, Inbred BALB C; D046529:Microscopy, Electron, Transmission / Q000379:methods; D009856:Oncogene Proteins, Viral / Q000378:metabolism*; D053918:Papillomavirus Vaccines / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry; D017434:Protein Structure, Tertiary; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012306:Risk
chemical_list: D036022:Capsid Proteins; D000939:Epitopes; C099170:L2 protein, Human papillomavirus type 18; D009856:Oncogene Proteins, Viral; D053918:Papillomavirus Vaccines; D010455:Peptides; D011993:Recombinant Fusion Proteins; C480565:L1 protein, Human papillomavirus type 18