Oral Opportunistic Infections in HIV-Positive Individuals: Review and Role of Mucosal Immunity

Oral opportunistic infections in the HIV-positive individual have been documented since the first reports of the epidemic, with many lesions associated with reduced CD4⁺ T lymphocyte cell count. The most common oral lesions seen in HIV disease prior to the advent of highly active antiretroviral therapy (HAART) were oropharyngeal candidiasis and oral hairy leukoplakia. However, since the advent of HAART while many oral lesions have decreased significantly the incidence of oral warts has surprisingly increased. Despite the correlation of diminished CD4⁺ T lymphocyte count to the occurrence of these lesions, it is rare for the lesions to occur concurrently suggesting that each pathologic lesion type is associated with distinct host immune dysfunctions. To date, the oral opportunistic infection most frequently investigated is oropharyngeal candidiasis, where data suggests that both systemic and local immunity is important for protection against infection. In contrast, recent investigations into the host responses associated with oral hairy leukoplakia and oral warts show little to no evidence of systemic or mucosal immune responsiveness despite the presumed competence of several types of leukocytes other than CD4⁺ T cells. Together these data are suggesting that susceptibility to oropharyngeal candidasis in HIV-positive persons is predominantly immune-based, whereas protection or susceptibility to oral hairy leukoplakia and oral warts may be more associated with factors other than mucosal immune function.