A novel vaccine against multidrug-resistant gonorrhea

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ABSTRACT Gonorrhea is the second most common bacterial sexually transmitted infection – the most common is chlamydia, which often coinfects with gonorrhea. About 80 million new cases of gonorrhea occur worldwide annually. Over 450,000 cases are reported yearly in the U.S. Serious sequelae of gonorrhea in women includes infertility, ectopic pregnancy and chronic pelvic pain. Neisseria gonorrhoeae (Ng), the causative agent of gonorrhea, has become resistant to almost every antibiotic in clinical use. Resistance to ceftriaxone and azithromycin – the recommended first-line of treatment –portends an era of untreatable gonorrhea. The CDC has listed Ng as a microorganism with a threat level of “Urgent”. Development of a safe and effective vaccine against gonorrhea is a public health priority. Furthermore, Ng and chlamydia coinfection is a frequent event and a successful gonococcal vaccine will prevent infection even when chlamydia infection is present. We identified a monoclonal antibody (mAb) called 2C7 that recognizes a lipooligosaccharide (LOS) epitope expressed by >95% of Ng in vivo and is critical for virulence in mice. mAb 2C7 is bactericidal and significantly reduces the duration and burden of Ng infection in mice. Its ubiquitous expression, key role in virulence, and the bactericidal nature of Ab against the 2C7 epitope makes it an attractive vaccine antigen. To circumvent limitations of LOS as a vaccine antigen, we identified a peptide mimic of the 2C7 epitope, which when configured as a multi-antigen peptide (MAP), elicited bactericidal Abs and attenuated Ng infection in mice. A Product Development Plan overseen by NIAID/NIH partnered us with ABL Inc., Peptides International and the Infectious Diseases Research Institute (IDRI). The objectives of the PDP have been met and has resulted in design of a novel tetra-MAP structure (TMCP2) and identification of GLA-SE as the optimal adjuvant based on immunogenicity in mice. In Aim 1, Peptides International will produce TMCP2, perform stability testing and transfer technology to the cGMP manufacturer. In Aim 2 (UMass), mice and non-human primates will be immunized with development-grade TMCP2 plus GLA-SE to evaluate i) immunogenicity and ii) functionality of elicited Ab in Ng infected or (separately) in Ng/chlamydia co-infected mice. Ng bind the complement inhibitors, factor H (FH) and C4b-binding protein (C4BP) in a human-specific manner, which dampens activity of vaccine Ab. Therefore, we will test vaccine efficacy in novel transgenic mice that express human FH and C4BP to simulate conditions in humans. Anti-LOS Ab purified from immunized Rhesus macaques will be assayed for bactericidal activity and for its ability to attenuate colonization in single Ng and Ng/chlamydia coinfected mice. ABL Inc. will qualify ELISAs and SBAs. A GLP-grade safety and toxicology study in New Zealand White Rabbits (ABL, Inc.) which is essential for product development will be performed in Aim 3. Pre-IND enabling studies will be carried out in Aim 4. Successful completion of these Aims will ready our vaccine candidate for human studies