Spontaneous proliferation of memory (CD45RO+) and naive (CD45RO-) subsets of CD4 cells and CD8 cells in human T lymphotropic virus (HTLV) infection: distinctive patterns for HTLV-I versus HTLV-II.

Spontaneous lymphocyte proliferation (SLP) in vitro is a characteristic feature of about 50% of individuals infected with HTLV-I or HTLV-II. Both CD4 cells and CD8 cells contribute to SLP in HTLV-I infection, whereas SLP in HTLV-II infection is usually restricted to CD8 cells. In this study, we asked if SLP was restricted to the memory (CD45RO+) cell subset of CD4 and CD8 cells in HTLV infection. Purified CD4 and CD8 cells were separated into CD45RO+ and CD45RO- populations by a modified panning technique, and spontaneous proliferation (SP) of the cell subsets was assessed. For all five HTLV-I-infected persons whose mononuclear cell cultures were SLP+, only CD45RO+ cells, but not CD45RO- cells, within CD4 and CD8 subsets showed SP. In contrast, five of six SLP+ HTLV-II+ individuals showed SP in both the CD45RO+ and the CD45RO- subsets of CD4 cells, and 10 of 12 SLP+ HTLV-II+ individuals showed SP of both the CD45RO+ and CD45RO- subsets of CD8 cells. Polymerase chain reaction studies showed that proviral genome was generally present in both CD45RO+ and CD45RO- subsets of CD4 and CD8 cells, regardless of HTLV type and SP activity. These findings show that SP of both CD4 and CD8 cells in HTLV-I infection is usually restricted to CD45RO+ memory cells, whereas in HTLV-II infection, both CD45RO+ memory and CD45RO- naive subsets of CD4 and CD8 cells may exhibit SP. It thus appears that HTLV-I infection and HTLV-II infection exhibit distinctive dysregulatory effects on memory and naive T cell subpopulations.