*5.3.1. Highly Exposed Persistently Seronegatives (HEPSs)*

They are individuals who are repeatedly exposed to HIV through different routes of exposure but persistently remain seronegative (do not develop antibody to HIV).

#### *5.3.2. Long-Term Nonprogressors (LTNPs)*

About 5–10 % of HIV-infected people remain asymptomatic for about 7–20 years after infection despite being on no antiretroviral therapy. Their immune function is well controlled with CD4+ lymphocytes counts above 6000/mm3 coupled with a low plasma HIV RNA. Initially, these were based primarily on immunologic control, i.e. maintenance of high CD4 count, but currently LTNPs are known as elite controllers based on viral load calculations/standards. Those with undetectable viremia (HIV RNA<50 copies/ml) are elite controllers, while those with low but detectable viral load (HIV RNA <2000 copies/ml) are known as viremic controllers [51, 52]. These individuals are referred to as LTNP or elite controllers (ECs) [47]. Other subgroups include typical progressors (TPs) where about 80 % of HIV-infected individuals develop AIDS within the median time of ten years [53] and rapid progressors (RPs) which develop within 2–3 years of infection and exist in 10 % of the population [54].
