Gonococci – Pathogens of Growing Importance. Part 2. Virulence Factors, Antimicrobial Resistance and Vaccine Development

Abstract

Neisseria gonorrhoeae (gonococcus) is a human pathogen, the aetiological agent of gonorrhoea, which is the second most common bacterial sexually transmitted disease (STD) in the world. The structure of N. gonorrhoeae cell wall is typical of Gram-negative bacteria, poses variable antigens porin B (PorB), and opacity-associated proteins (Opa proteins), lipooligosaccharide (LOS) and type IV pili (TFP) playing an essential role in pathogenesis. In addition to adhesins, gonococcus presents other virulence factors such as reducing modifiable protein (Rmp), iron transporters, membrane pumps, and IgA peptidase. The pathogen produces outer membrane vesicles (OMVs), releases peptidoglycan (PG) fragments and is well adapted to develop infection in diverse niches of the female and male reproductive tracts. The characteristic genotypic trait of N. gonorrhoeae is the state of natural competence, which allows DNA uptake from the environment. The antigenic and phase variability is essential to gonococcal defence against the human immune system. Because of the increasing antimicrobial resistance (AMR) of N. gonorrhoeae and the high incidence rate of gonococcal infections, developing an antigonococcal vaccine has become an urgent need. Vaccine development difficulties are mainly due to the gonococcal ability of immune evasion, the lack of an animal model, and the limited understanding of protective immune response mechanisms.