BackgroundVaccination with minor capsid protein L2 induces antibodies that cross-neutralize diverse papillomavirus types. However, neutralizing antibody titers against the papillomavirus type from which the L2 vaccine was derived are generally higher than the titers against heterologous types, which could limit effectiveness against heterologous types. We hypothesized that vaccination with concatenated multitype L2 fusion proteins derived from known cross-protective epitopes of several divergent human papillomavirus (HPV) types might enhance immunity across clinically relevant HPV genotypes.MethodsAntibody responses of mice (n = 120) and rabbits (n = 23) to vaccination with HPV-16 amino-terminal L2 polypeptides or multitype L2 fusion proteins, namely, 11-200 × 3 (HPV types 6, 16, 18), 11-88 × 5 (HPV types 1, 5, 6, 16, 18), or 17-36 × 22 (five cutaneous, two mucosal low-risk, and 15 oncogenic types), that were formulated alone or in GPI-0100, alum, or 1018 ISS adjuvants were compared with vaccination with L1 virus-like particles (VLPs), including Gardasil, a licensed quadrivalent HPV L1 vaccine, and a negative control. Mice were challenged with HPV-16 pseudovirions 4 months after vaccination. Statistical tests were two-sided.ResultsThe HPV-16 L2 polypeptides generated robust HPV-16–neutralizing antibody responses, albeit lower than those to HPV-16 L1 VLPs, and lower responses against other HPVs. In contrast, vaccination with the multitype L2 fusion proteins 11-200 x 3 and 11-88 x 5 induced high serum neutralizing antibody titers against all heterologous HPVs tested. 11-200 × 3 formulated in GPI-0100 adjuvant or alum with 1018 ISS protected mice against HPV-16 challenge (reduction in HPV-16 infection vs phosphate-buffered saline control, P < .001) 4 months after vaccination as well as HPV-16 L1 VLPs, but 11-200 × 3 alone or formulated with either alum or 1018 ISS was less effective (reduction in HPV-16 infection, P < .001).ConclusionConcatenated multitype L2 proteins in adjuvant have potential as pan-oncogenic HPV vaccines.

A stabilized form of the respiratory syncytial virus (RSV) fusion (F) protein has been explored as a vaccine to prevent viral infection because it presents several potent neutralizing epitopes. Here, we used a structure-based rational design to optimize antigen presentation and focus antibody (Ab) responses to key epitopes on the pre-fusion (pre-F) protein. This protein was fused to ferritin nanoparticles (pre-F-NP) and modified with glycans to mask nonneutralizing or poorly neutralizing epitopes to further focus the Ab response. The multimeric pre-F-NP elicited durable pre-F–specific Abs in nonhuman primates (NHPs) after >150 days and elicited potent neutralizing Ab (NAb) responses in mice and NHPs in vivo, as well as in human cells evaluated in the in vitro MIMIC system. This optimized pre-F-NP stimulated a more potent Ab response than a representative pre-F trimer, DS-Cav1. Collectively, this pre-F vaccine increased the generation of NAbs targeting the desired pre-F conformation, an attribute that facilitates the development of an effective RSV vaccine.

We sought to define the protective epitopes within the amino terminus of human papillomavirus (HPV) type 16 minor capsid protein L2. Passive transfer of mice with rabbit antisera to HPV16 L2 peptides 17–36, 32–51 and 65–81 provided significant protection against vaginal HPV16 challenge, whereas antisera to 47–66, 108–120 or 373–392 did not. Vaccination with L1 virus-like particles induces a high titer, but generally type-restricted neutralizing antibody response. Conversely, vaccination with L2 11–88, especially multimers thereof, induces antibodies that neutralize a broad range of papillomavirus types, albeit at lower titers than for L1 VLP. With the intent of enhancing the immunogenicity and the breadth of protection by focusing the immune response to the key protective epitopes, we designed L2 fusion proteins consisting of residues ∼11–88 of eight divergent mucosal HPV types 6, 16, 18, 31, 39, 51, 56, 73 (11–88×8) or residues ∼13–47 of fifteen HPV types (13–47×15). The 11–88×8 was significantly more immunogenic than 13–47×15 in Balb/c mice regardless of the adjuvant used, suggesting the value of including the 65–81 protective epitope in the vaccine. Since the L2 47–66 peptide antiserum failed to elicit significant protection, we generated an 11–88×8 construct deleted for this region in each subunit (11–88×8Δ). Mice were vaccinated with 11–88×8 and 11–88×8Δ to determine if deletion of this non-protective epitope enhanced the neutralizing antibody response. However, 11–88×8Δ was significantly less immunogenic than 11–88×8, and even the addition of a known T helper epitope, PADRE, to the construct (11–88×8ΔPADRE) failed to recover the immunogenicity of 11–88×8 in C57BL/6 mice, suggesting that while L2 47–66 is not a critical protective or T helper epitope, it nevertheless contributes to the immunogenicity of the L2 11–88×8 multimer vaccine.

Emergency use authorization of COVID vaccines has brought hope to mitigate pandemic of coronavirus disease 2019 (COVID-19). However, there remains a need for additional effective vaccines to meet the global demand and address the potential new viral variants. mRNA technologies offer an expeditious path alternative to traditional vaccine approaches. Here we describe the efforts to utilize an mRNA platform for rational design and evaluations of mRNA vaccine candidates based on the spike (S) glycoprotein of SARS-CoV-2. Several mRNA constructs of S-protein, including wild type, a pre-fusion stabilized mutant (2P), a furin cleavage-site mutant (GSAS) and a double mutant form (2P/GSAS), as well as others, were tested in animal models for their capacity to elicit neutralizing antibodies (nAbs). The lead 2P/GSAS candidate was further assessed in dose-ranging studies in mice and Cynomolgus macaques, and for efficacy in a Syrian golden hamster model. The selected 2P/GSAS vaccine formulation, designated MRT5500, elicited potent nAbs as measured in neutralization assays in all three preclinical models and more importantly, protected against SARS-CoV-2-induced weight loss and lung pathology in hamsters. In addition, MRT5500 elicited TH1-biased responses in both mouse and non-human primate (NHP), thus alleviating a hypothetical concern of potential vaccine-associated enhanced respiratory diseases known associated with TH2-biased responses. These data position MRT5500 as a viable vaccine candidate for entering clinical development.

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.