Integrated Bioinformatic Analyses and Immune Characterization of New Neisseria gonorrhoeae Vaccine Antigens Expressed during Natural Mucosal Infection

Abstract

There is an increasingly severe trend of antibiotic-resistant Neisseria gonorrhoeae strains worldwide and new therapeutic strategies are needed against this sexually-transmitted pathogen. Despite the urgency, progress towards a gonococcal vaccine has been slowed by a scarcity of suitable antigens, lack of correlates of protection in humans and limited animal models of infection. N. gonorrhoeae gene expression levels in the natural human host does not reflect expression in vitro, further complicating in vitro-basedvaccine analysis platforms. We designed a novel candidate antigen selection strategy (CASS), based on a reverse vaccinology-like approach coupled with bioinformatics. We utilized the CASS to mine gonococcal proteins expressed during human mucosal infection, reported in our previous studies, and focused on a large pool of hypothetical proteins as an untapped source of potential new antigens. Via two discovery and analysis phases (DAP), we identified 36 targets predicted to be immunogenic, membrane-associated proteins conserved in N. gonorrhoeae and suitable for recombinant expression. Six initial candidates were produced and used to immunize mice. Characterization of the immune responses indicated cross-reactive antibodies and serum bactericidal activity against different N. gonorrhoeae strains. These results support the CASS as a tool for the discovery of new vaccine candidates.

Beyond the pan-genome: current perspectives on the functional and practical outcomes of the distributed genome hypothesis

“…For a vaccine against the more complex Streptococcus agalactiae , reverse vaccinology using the supragenome/pan-genome was employed for the first time [ 153 ]. Somewhat later reverse vaccinology was used to compare pathogenic and nonpathogenic strains of the same species to find antigens that truly affect pathogenesis These successes led to application of reverse vaccinology to other pathogens including N. gonorrheae and Mycoplasma pneumoniae [ 154 , 155 ]. It is important to point out that reverse vaccinology and microbiome-sparing vaccine approaches are still susceptible to the evolution of vaccine escape mutants.…”

The Neisseria gonorrhoeae Vaccine Candidate NHBA Elicits Antibodies That Are Bactericidal, Opsonophagocytic and That Reduce Gonococcal Adherence to Epithelial Cells

“…The SBA titres ranged from 50 to 1600 for the different vaccine antigens and formulations against different strains. A wide range of SBA titers have been reported for other antigens tested against various N. gonorrhoeae strains, for example MetQ and MsrAB have SBA titres of 320 and 100, respectively, against strain 1291 [28,30], NGO0690 has a SBA titre of 10 against strain FA1090, and NGO1701 has a SBA titre of 40 against strain F62 [37]. However, assays are not standardised which makes direct comparisons difficult.…”

Omics and Bioinformatics Approaches to Identify Novel Antigens for Vaccine Investigation and Development

“…This is also the case of the sexually-transmitted Neisseria gonorrhoeae , for which the development of protective vaccines is hampered, among other factors, by suitable antigen scarcity and adequate animal models of infection. Zhu et al designed a new strategy for antigen identification based on reverse vaccinology and bioinformatics, termed the candidate antigen selection strategy (CASS) [ 13 ]. Using previously identified pools of proteins expressed by N. gonorrhoeae during human mucosal infections, the authors identified 36 membrane-associated proteins that were conserved in N. gonorrhoeae and predicted as immunogenic [ 13 ].…”

“…Zhu et al designed a new strategy for antigen identification based on reverse vaccinology and bioinformatics, termed the candidate antigen selection strategy (CASS) [ 13 ]. Using previously identified pools of proteins expressed by N. gonorrhoeae during human mucosal infections, the authors identified 36 membrane-associated proteins that were conserved in N. gonorrhoeae and predicted as immunogenic [ 13 ]. Out of the 36 candidates, 6 were used to immunize mice, and were shown to be capable of inducing cross-reactive antibodies and serum bactericidal activity.…”

“…Out of the 36 candidates, 6 were used to immunize mice, and were shown to be capable of inducing cross-reactive antibodies and serum bactericidal activity. The results suggest the CASS strategy as a useful tool in vaccine candidate identification [ 13 ].…”