Host Cell Invasion by Pathogenic Neisseriae

Abstract

Neisseria gonorrhoeae and Neisseria meningitidis have become exquisitely adapted to life within humans, their only natural host. Both species possess the ability to colonize human mucosal tissues without generating any detectable clinical manifestations, and this carrier state likely contributes to their maintenance within the population. They are, however, also capable of persisting during the massive inflammatory responses, representing a hallmark of neisserial diseases. Despite their close evolutionary relationship (Tinsley and Nassif, 1996), N. gonorrhoeae primarily infects the uro- or anorectal mucosa following intimate sexual contact, while N. meningitidis colonizes the nasopharynx after the inhalation of infected respiratory droplets. This association is at least partially the result of their respective modes of transmission rather than a tropism restricted to these loci, since gonococcal pharyngitis and meningococcal anogenital infections have both also been described (Janda et al., 1980; Givan et al., 1977). Nasopharyngeal and fallopian tube organ cultures, and ureteral tissue models of infection indicate that both species penetrate to submucosal layers in vitro (Mosleh et al., 1997; McGee et al., 1983), and this is consistent with the detection of sloughed epithelial cells containing intracellular gonococci in urethral exudates obtained from men with symptomatic gonorrhea (Apicella et al., 1996). Complications arising from the spread of gonococci from the primary loci of infection can result in significant morbidity and, potentially, sterility. Similarly, although localized meningococcal infection of the mucosa is typically asymptomatic, dissemination from this site can lead to the rapidly advancing and often fatal meningococcal meningitis and/or meningococcemia.