Both memory and CD45RA(+)/CD62L(+) naive CD4(+) T cells are infected in human immunodeficiency virus type 1-infected individuals

Cellular activation is critical for the propagation of human immunodeficien cy virus type 1 (HIV-1) infection. It has been suggested that truly naive C D4(+) T cells are resistant to productive HIV-1 infection because of their constitutive resting state. Memory and naive CD4(+) T-cell subsets from 11 HIV-1-infected individuals were isolated ex vivo by a combination of magnet ic bead depletion and fluorescence-activated cell sorting techniques with s tringent criteria of combined expression of CD45RA and CD62L to identify na ive CD4(+) T-cell subsets. In all patients HIV-1 provirus could be detected within naive CD45RA(+)/CD62L(+) CD4(+) T cells; in addition, replication-c ompetent HIV-1 was isolated from these cells upon CD4(+) T-cell stimulation in tissue cultures. Memory CD4(+) T cells had a median of fourfold more re plication-competent virus and a median of sixfold more provirus than naive CD4(+) T cells. Overall, there was a median of 16-fold more integrated prov irus identified in memory CD4(+) T cells than in naive CD4(+) T cells withi n a given patient. Interestingly, there was a trend toward equalization of viral loads in memory and naive CD4(+) T-cell subsets in those patients who harbored CXCR4-using (syncytium-inducing) viruses. Within any given patien t, there was no selective usage of a particular coreceptor by virus isolate d from memory versus naive CD4(+) T cells. Our findings suggest that naive CD4(+) T cells may be a significant viral reservoir for HIV, particularly i n those patients harboring CXCR4-using viruses.