Gonococcal peptide vaccine candidate display using HPV virus-like particles

摘要

ABSTRACT About 87 million new cases of gonorrhea occur globally, annually. In 2018, 583,405 cases were reported in the U.S, an 82.6% increase in disease incidence since the historic low in 2009. Human papillomaviruses (HPVs) are the causative agents of cervical cancer, the 4th most common cancer in women globally, resulting in ~567,000 cases and 311,000 deaths every year. About 80% of these cases occur in resource-poor developing countries. There are currently three licensed effective prophylactic HPV vaccines. Despite the great success of these vaccines, the cervical cancer burden remains high, particularly in developing countries, as these vaccines are expensive and type-specific. Neisseria gonorrhoeae (Ng), the causative agent of gonorrhea, has become resistant to almost every antibiotic in clinical use and portends an era of untreatable gonorrhea. Development of a safe and effective vaccine against gonorrhea is a global public health priority. Lipooligosaccharide (LOS) is the most abundant molecule on the gonococcal surface and plays multifaceted roles in bacterial virulence. A LOS epitope recognized by mAb 2C7 (therefore called the 2C7 epitope) is expressed by >95% of Ng in vivo; Ng mutants that do not express the 2C7 epitope are attenuated in mice. This is because the 2C7 LOS epitope can be modified with sialic acid, which increases resistance of the bacteria to complement-dependent killing and engages Siglec receptors to down-regulate host inflammation. We have developed a peptide mimic (mimitope) of the 2C7 epitope, which when configured as a multi-antigen peptide (MAP) elicits bactericidal Abs and attenuates Ng colonization in mice in a complement-dependent manner. This project will leverage the HPV virus-like particle (VLP) platform to deliver the 2C7 mimitope. VLPs are an excellent platform to enhance immunogenicity of peptides. We have already produced HPV VLPs that express the Ng mimitope peptide (called HPV-Ng) in tobacco plants and in mammalian cells on a small scale. Production in tobacco plant expression could reduce costs, an important consideration for vaccines against STIs that disproportionately affect socio-economically underprivileged populations. In Aim 1 we will test the immunogenicity and in vitro function of antibodies (Abs) elicited by HPV-Ng. We will measure Ab responses in male and female BALB/c, C57BL/6 and CD1 mice against i) the 2C7 LOS epitope and ii) against HPV16. An intact complement system is necessary and sufficient for activity in vivo of Ab against the 2C7epitope. Therefore, we will test complement-dependent bactericidal activity of immune Ab against Ng. The ability of anti-HPV Ab to neutralize pseudovirions (PsVs) – an in vitro measure of efficacy against HPV – will be measured. In Aim 2, the efficacy of HPV-Ng against Ng will be tested in a gonococcal vaginal colonization model in mice that express human complement inhibitors, to better simulate the complement system of humans and provide a more stringent test of vaccine efficacy. Efficacy of HPV-Ng against HPV16 will be tested in a HPV PsV cervicovaginal model in mice.