Host defense against oropharyngeal and vaginal candidiasis: Site-specific differences.

Mucosal candidiasis is extremely common in immunocompromised patients. However, the prevalence of site-specific infection (i.e., oropharyngeal, vaginal, and esophageal candidiasis) can be quite variable depending on the immune status of the host. While vulvovaginal candidiasis is common in normal healthy women, oropharyngeal and esophageal candidiasis are more frequently encountered under immunocompromised states. Candida albicans, the causative agent in most cases of candidiasis, is a commensal organism of the gastrointestinal and lower female reproductive tracts. Thus, most healthy individuals have demonstrable Candida-specific immunity in the peripheral circulation. The pathogenic state is often precipitated by a deficiency or dysfunction in this immunity. Studies from animal models, women with recurrent vulvovaginal candidiasis, and HIV-infected individuals, however, suggest that distinct host defense mechanisms may function against oropharyngeal and vulvovaginal candidiasis. While cell-mediated immunity (CMI) appears important for protection against oropharyngeal candidiasis (OPC), there is little evidence to indicate that T cell-mediated immunity is protective against vulvovaginal candidiasis (VVC). Furthermore, whereas both local and systemically derived immune defenses appear important for protection against OPC, host defenses that protect against VVC appear limited to the local tissue and possibly restricted to innate mechanisms. Thus, current evidence suggests that VVC, unlike OPC, may not represent a strict opportunistic infection.