The high frequency of HIV type 1-specific cellular immune responses in seronegative individuals with parenteral and/or heterosexual HIV type 1 exposure.

Some individuals remain HIV seronegative despite repeated unprotected exposure to the virus. Recent observations led to a concept that acquired immunity plays a role in protection or at least in altered susceptibility to HIV-1 infection in highly exposed seronegative (ESN) individuals. Our aim was to study HIV-specific cellular immune responses induced in parenterally and/or heterosexually ESN individuals.