It has been found that infection of target cells with the CC chemokine receptor 5-restricted (R5) human immunodeficiency virus type 1 (HIV-1) isolate requires the presence of CD4 and CCR5 molecules on the surface of target cells. We observed that R5 HIV-1 primary isolates from long term survivors replicate less efficiently than the same variants from AIDS progressors in Th1 and Th2 lymphocytes. Real-time quantitative polymerase chain reaction (RQ-PCR) of reverse transcribed messenger RNA, revealed approximately 2 times higher level of CCR5 transcript in Th1 than Th2 cells. Nevertheless we found that R5 HIV-1 primary isolates from long-term survivors and AIDS progressors replicated more efficiently in Th2 than Th1 lymphocytes. These findings correlated with lower-level biosynthesis of regulated upon activation, normal T-cell expressed and secreted (RANTES), and macrophage inflammatory protein-1alpha and -1beta (MIP-1alpha, MIP-1beta), in Th2 than Th1 lymphocytes. Our data indicates that Th0/Th2 cell orientation in HIV-infected individuals and a higher replication of R5 HIV-1 primary isolates in AIDS progressors than long term-survivors can be associated with progression to AIDS.