Preclinical Efficacy of a Lipooligosaccharide Peptide Mimic Candidate Gonococcal Vaccine Sunita Gulati, a Michael W. Pennington, b Andrzej Czerwinski, c Darrick Carter, d Bo Zheng, a Nancy A. Nowak, a Rosane B. DeOliveira, a Jutamas Shaughnessy, a George W. Reed, a Sanjay Ram, a Peter A. Rice a a Department of Medicine, Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, USA b AmbioPharm, Inc., North Augusta, South Carolina, USA c Peptides International Inc., Louisville, Kentucky, USA d Infectious Diseases Research Institute, Seattle, Washington, USA ABSTRACT The global spread of multidrug-resistant strains of Neisseria gonorrhoeae constitutes a public health emergency. With limited antibiotic treatment options, there is an urgent need for development of a safe and effective vaccine against gonorrhea. Previously, we constructed a prototype vaccine candidate comprising a peptide mimic (mimitope) of a glycan epitope on gonococcal lipooligosaccharide (LOS), recognized by monoclonal antibody 2C7. The 2C7 epitope is (i) broadly ex- pressed as a gonococcal antigenic target in human infection, (ii) a critical require- ment for gonococcal colonization in the experimental setting, and (iii) a virulence determinant that is maintained and expressed by gonococci. Here, we have synthe- sized to 95% purity through a relatively facile and economical process a tetrapep- tide derivative of the mimitope that was cyclized through a nonreducible thioether bond, thereby rendering the compound homogeneous and stable. This vaccine can- didate, called TMCP2, when administered at 0, 3, and 6 weeks to BALB/c mice at ei- ther 50, 100 or 200 g/dose in combination with glucopyranosyl lipid A-stable oil-in- water nanoemulsion (GLA-SE; a Toll-like receptor 4 and T H 1-promoting adjuvant), elicited bactericidal IgG and reduced colonization levels of gonococci in experimen- tally infected mice while accelerating clearance by each of two different gonococcal strains. Similarly, a 3-dose biweekly schedule (50 g TMCP2/dose) was also effective in mice. We have developed a gonococcal vaccine candidate that can be scaled up and produced economically to a high degree of purity. The candidate elicits bacteri- cidal antibodies and is efficacious in a preclinical experimental infection model. IMPORTANCE Neisseria gonorrhoeae has become resistant to most antibiotics. The incidence of gonorrhea is also sharply increasing. A safe and effective antigonococ- cal vaccine is urgently needed. Lipooligosaccharide (LOS), the most abundant outer membrane molecule, is indispensable for gonococcal pathogenesis. A glycan epitope on LOS that is recognized by monoclonal antibody (MAb) 2C7 (called the 2C7 epitope) is expressed almost universally by gonococci in vivo. Previously, we identi- fied a peptide mimic (mimitope) of the 2C7 epitope, which when configured as an octamer and used as an immunogen, attenuated colonization of mice by gonococci. Here, a homogenous, stable tetrameric derivative of the mimitope, when combined with a T H 1-promoting adjuvant and used as an immunogen, also effectively attenu- ates gonococcal colonization of mice. This candidate peptide vaccine can be pro- duced economically, an important consideration for gonorrhea, which affects socio- economically underprivileged populations disproportionately, and represents an important advance in the development of a gonorrhea vaccine. KEYWORDS Neisseria gonorrhoeae, vaccine, peptide, antibody function, experimental infection, immunization/vaccine Citation Gulati S, Pennington MW, Czerwinski A, Carter D, Zheng B, Nowak NA, DeOliveira RB, Shaughnessy J, Reed GW, Ram S, Rice PA. 2019. Preclinical efficacy of a lipooligosaccharide peptide mimic candidate gonococcal vaccine. mBio 10:e02552-19. https://doi.org/10.1128/ mBio.02552-19. Editor Joanna B. Goldberg, Emory University School of Medicine Copyright © 2019 Gulati et al. This is an open- access article distributed under the terms of the Creative Commons Attribution 4.0 International license. Address correspondence to Peter A. Rice, peter.rice@umassmed.edu. This article is a direct contribution from Peter A. Rice, a Fellow of the American Academy of Microbiology, who arranged for and secured reviews by David Stephens, Emory University, and Scott Gray-Owen, University of Toronto. Received 3 October 2019 Accepted 8 October 2019 Published RESEARCH ARTICLE Therapeutics and Prevention November/December 2019 Volume 10 Issue 6 e02552-19 ® mbio.asm.org 1 5 November 2019 on June 2, 2020 by guest http://mbio.asm.org/ Downloaded from