Durable immunity to oncogenic human papillomaviruses elicited by adjuvanted recombinant Adeno-associated virus-like particle immunogen displaying L2 17–36 epitopes

Abstract

Vaccination with the minor capsid protein L2, notably the 17–36 neutralizing epitope, induces broadly protective antibodies, although the neutralizing titers attained in serum are substantially lower than for the licensed L1 VLP vaccines. Here we examine the impact of other less reactogenic adjuvants upon the induction of durable neutralizing serum antibody responses and protective immunity after vaccination with HPV16 and HPV31 L2 amino acids 17–36 inserted at positions 587 and 453 of VP3, respectively, for surface display on Adeno-Associated Virus 2-like particles [AAVLP (HPV16/31L2)]. Mice were vaccinated three times subcutaneously with AAVLP (HPV16/31L2) at two week intervals at several doses either alone or formulated with alum, alum and MPL, RIBI adjuvant or Cervarix. The use of adjuvant with AAVLP (HPV16/31L2) was necessary in mice for the induction of L2-specific neutralizing antibody and protection against vaginal challenge with HPV16. While use of alum was sufficient to elicit durable protection (>3 months after the final immunization), antibody titers were increased by addition of MPL and RIBI adjuvants. To determine the breadth of immunity, rabbits were immunized three times with AAVLP (HPV16/31L2) either alone, formulated with alum ± MPL, or RIBI adjuvants, and after serum collection, the animals were concurrently challenged with HPV16/31/35/39/45/58/59 quasivirions or cottontail rabbit papillomavirus (CRPV) at 6 or 12 months post-immunization. Strong protection against all HPV types was observed at both 6 and 12 months post-immunization, including robust protection in rabbits receiving the vaccine without adjuvant. In summary, vaccination with AAVLP presenting HPV L2 17–36 epitopes at two sites on their surface induced cross-neutralizing serum antibody, immunity against HPV16 in the genital tract, and long-term protection against skin challenge with the 7 most common oncogenic HPV types when using a clinically relevant adjuvant.

Broad Cross-Protection Is Induced in Preclinical Models by a Human Papillomavirus Vaccine Composed of L1/L2 Chimeric Virus-Like Particles

“…2A). The HPV-18 L1/L2 chimera induced an anti-HPV-33 L2 [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] antibody GMT that was 3.7-fold higher (P Ͻ 0.05) than that induced by the HPV-18 L1 chimera containing L2 [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] at the C terminus [HPV-18 L1/L2 CT (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)…”

“…This strategy is supported by evidence that vaccines based on L2 peptides can confer broad protection in mouse or rabbit HPV challenge models and elicit neutralizing antibodies against a wide range of HPVs (27,(29)(30)(31)(32)(33). However, during natural infection, the immunogenicity of L2 epitopes appears subdominant relative to L1 epitopes, probably because the density of L2 exposed on the capsid surface with respect to L1 is low and/or because L2 is buried within the HPV capsid and may be only transiently exposed after receptor engagement on the cell surface (34).…”

“…An alternative strategy to broaden the protection of HPV vaccines that is also being considered is to use conserved epitopes from the L2 minor capsid protein incorporated into HPV L1 VLPs (22)(23)(24)(25)(26)(27)(28)(29). This strategy is supported by evidence that vaccines based on L2 peptides can confer broad protection in mouse or rabbit HPV challenge models and elicit neutralizing antibodies against a wide range of HPVs (27,(29)(30)(31)(32)(33).…”

“…Therefore, one way to render L2 epitopes immunogenic for vaccination is to insert L2 peptides into immunogenic HPV L1 VLPs (22-24, 27, 35, 36). One L2 epitope (consisting of amino acid residues 17 to 36; L2 [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] ), recognized as a linear neutralizing epitope (RG1 epitope) (30)(31)(32), has been incorporated into the capsid surface DE loop of HPV-16 L1 or HPV-18 L1 to create chimeric L1/L2 VLP vaccines (24,25,27). Both L1/L2 vaccines (based on either HPV-16 or HPV-18 L1) provided protection in a mouse challenge model against a broad range of high-risk HPVs (25,27) and generated L2-specific neutralizing antibodies together with L1-specific neutralizing antibodies (24,25,27).…”

“…The antigens were constructed by inserting the well-conserved L2 [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] and L2 56 -75 neutralizing epitopes within the DE loop and/or C-terminal arm of HPV-16 or HPV-18 L1 proteins. The immunogenicity and/or efficacy of the different formulations was compared using mouse and rabbit models.…”