Robust In Vitro and In Vivo Neutralization against Multiple High-Risk HPV Types Induced by a Thermostable Thioredoxin-L2 Vaccine

Abstract

Current prophylactic virus-like particle (VLP) human papillomavirus (HPV) vaccines are based on the L1 major capsid protein and provide robust but virus type-restricted protection. Moreover, VLP vaccines have a high production cost, require cold-chain storage, and are thus not readily implementable in developing countries, which endure 85% of the cervical cancer-related death burden worldwide. In contrast with L1, immunization with minor capsid protein L2 elicits broad cross-neutralization, and we previously showed that insertion of a peptide spanning amino acids 20-38 of L2 into bacterial thioredoxin (Trx) greatly enhances its immunogenicity. Building on this finding, we use, here, four different neutralization assays to demonstrate that low doses of a trivalent Trx-L2 vaccine, incorporating L2(20-38) epitopes from HPV16, HPV31 and HPV51, and formulated in a human-compatible adjuvant, induce broadly protective responses. Specifically, we show that this vaccine, which uses a far-divergent archaebacterial thioredoxin as scaffold and is amenable to an easy onestep thermal purification, induces robust cross-neutralization against 12 of the 13 known oncogenic HPV types. Immune performance measured with two different in vitro neutralization assays was corroborated by the results of mouse cervico-vaginal challenge and passive transfer experiments indicating robust cross-protection also in vivo. Altogether, our results attest to the potential of Trx-L2 as a thermostable second-generation HPV vaccine particularly well suited for low-resource countries. Cancer Prev Res; 8(10); 932-41. Ó2015 AACR.

Developments in L2-based human papillomavirus (HPV) vaccines

“…Although differences in the spectrum and robustness of L2 specific antibodies in varying animal species and depending on the antigen formulation have been reported (our personal observation;(Kondo et al, 2008; Seitz et al, 2015)), the phenomenon of broad protection induced by L2 vaccines is consistent. However, there is only very limited data in humans that demonstrate weak L2 specific antibody responses and these were in response to vaccination with full-length HPV L2 protein or distinct HPV16 L2 peptides (Kawana et al, 2003; Wang et al, 2014b).…”

“…Of note the phage vaccine has been shown to retain immunogenicity following spray-drying and rehydration, a potential advantage for eventual vaccine distribution in the absence of a cold-chain in underdeveloped countries (Tumban et al, 2015). In addition, a thermostable Thioredoxin-L2 vaccine that has been shown to induce robust neutralization against multiple hrHPV types is close to cGMP production for a planned human trial ((Seitz et al, 2015); Martin Müller, personal communication).…”

“…A trivalent Trx-L2 vaccine based on Pyrococcus furiosus Trx (which has low cross-reactivity to human Trx), incorporating L2 (aa 20-38) epitopes from HPV16, HPV31 and HPV51 and formulated in human-compatible alum + MPL adjuvant, induced broadly cross-neutralizing and cross-protective antibody responses in mice and guinea pigs (Seitz et al, 2015). Of note, P. furiosus Trx-L2 is a thermostable formulation that would be particularly suited for low-resource countries without functional cold chain and in addition allows for one step purification from expressed bacteria.…”

Virus-like Particle-Based L2 Vaccines against HPVs: Where Are We Today?

“…For example, immunizations with an L2 peptide conjugated to thioredoxin [44,45], immunizations with concatemers of L2 protein fused to a self-adjuvanting protein (flagellin) [46,47] as well as immunizations with a concatemer of L2 proteins derived from different HPV types [48,49] have been used. More recently, an L2 polypeptide and a heptamerizing coiled-coil polypeptide OVX313 fused to a nanoparticle derived from a thermostable thioredoxin has been used [50][51][52]. These approaches have enhanced the immunogenicity of L2 peptides, especially immunization with the nanoparticle thioredoxin-L2-OVX313 candidate vaccine.…”

Progress and prospects for L2-based human papillomavirus vaccines

“…However, neutralization was strongest in constructs including only 3 and 9 copies of L2, indicating there is a constraining capacity that could limit multimeric and multitype L2 display [81]. However, a trivalent archebacterial Trx-L2 vaccine incorporating 3 proteins displaying L2 20-38 of HPV16, 31 and 51 respectively shows a promising spectrum of protection and its heat stability offers a rapid method of purification and sterilization [83, 84]. …”