Phylogenetic Considerations in Designing a Broadly Protective Multimeric L2 Vaccine

Abstract

While the oncogenic human papillomavirus (HPV) types with the greatest medical impact are clustered within the ␣9 and ␣7 species, a significant fraction of cervical cancers are caused by ␣5, ␣6, and ␣11 viruses. Benign genital warts are caused principally by the ␣10 viruses HPV6 and HPV11. In an effort to achieve broad protection against both cervical cancer-and genital wart-associated types, we produced at high levels in bacteria a multimeric protein (␣11-88x8) fusing eight polypeptides corresponding to a protective domain comprising L2 residues ϳ11 to 88 derived from HPV6 (␣10), HPV16 (␣9), HPV18 (␣7), HPV31 (␣9), HPV39 (␣7), HPV51 (␣5), HPV56 (␣6), and HPV73 (␣11) and a truncated derivative with the last three units deleted (␣11-88x5). Mice were immunized three times with ␣11-88x8 or ␣11-88x5 adjuvanted with alum or the licensed HPV vaccines and challenged intravaginally with HPV6, HPV16, HPV26, HPV31, HPV33, HPV35, HPV45, HPV51, HPV56, HPV58, or HPV59 pseudovirions. The ␣11-88x5 and ␣11-88x8 vaccines induced similarly robust protection against each HPV type tested and indistinguishable HPV16-neutralizing antibody titers. Passive transfer of ␣11-88x8 antisera was protective. Further, rabbit antisera to ␣11-88x8 and ␣11-88x5 similarly neutralized native HPV18 virions. These findings suggest that immunologic competition between units is not a significant issue and that it is not necessary to include a unit of L2 derived from each species to achieve broader protection against diverse medically significant HPV types than is achieved with the licensed HPV vaccines.

Seroepidemiology of Human Papillomavirus 16 (HPV16) L2 and Generation of L2-Specific Human Chimeric Monoclonal Antibodies

“…The key neutralizing epitopes of HPV16 L2 have been mapped to its first 88 residues (40). However, none of the fulllength HPV16 L2-reactive sera reacted in an ELISA with the L2␣ 11-88x5, an antigen composed of amino acids 11 to 88 from the L2 of HPV6/16/18/31/39 (17). This negative ELISA result was consistent with the inability of these sera to neutralize HPV16 pseudovirions (Table 2) despite their reactivity toward full-length HPV16 L2 by ELISA and Western blot.…”

“…The neutralizing monoclonal antibodies WW-1 (29) and MAb24B (39) are particularly broadly reactive. WW-1 is a rat monoclonal IgG2a antibody that binds to HPV16 L2 [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] but neutralizes more HPV genotypes than the first-generation mouse monoclonal antibody RG-1 (29). The mouse monoclonal antibody MAb24B developed by Nakao et al (39) neutralizes several genital HPV types and recognizes HPV16 L2 residues 58 to 64.…”

“…Immobilon plates (Nunc) were coated with 500 ng/well purified baculovirus-derived HPV16/18 L1 VLPs (36), HPV16/31/45/58 pseudovirions (PsVs), or bacterially expressed and 6His-tagged HPV16 L2 (37), or L2␣ 11-88x5 multimer polypeptide (17). The plates were incubated overnight at 4°C.…”

“…Design and generation of JWW-1 and JWW-2 expression plasmids. The rat monoclonal antibody WW-1 is broadly neutralizing and reactive with HPV16 L2 [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] (29). The WW-1 heavy-and light-chain sequences were obtained by sequencing the hybridoma cDNA (Aldevron, Fargo, MN, USA).…”

“…Therefore, we and others have sought to enhance cross-protection by either the concatenation of L2 epitopes derived from several HPV types or the display of L2 epitopes on VLPs. Both approaches can provide broad protection in vaccinated animals against experimental challenge with diverse HPV types (15)(16)(17)(18)(19).…”