[Protective immunity against HIV infection]

The clinical manifestation of HIV infection varies among HIV-exposed individuals. Most HIV infected people will develop AIDS after 8-10-yr exposure. However, long-term nonprogressors (LTNP) can remain asymptomatic and keep normal CD4 cell in the absence of treatment even after more than 10-yr of infection. In addition there are some exposed yet uninfected individuals (EU) despite repeated exposure of HIV among high risk group. Although HIV-specific IgG antibodies and small amount of viral RNA could be observed among the former LTNP group, no HIV-specific IgG and virions could be detected in the latter EU cohort. In contrast, the fact that cellular immune responses, in particular HIV-specific CD8+ CTL immunity could be seen in both groups strongly indicates their importance for the establishment of protective immunity. Together with the cellular immunity, the effect of mucosal immune components such as secretory IgA, gamma delta T cells and dendritic cells toward HIV infection will be discussed.