Effect of long-term infection with nef-defective attenuated HIV type 1 on CD4+ and CD8+ T lymphocytes:: Increased CD45RO+CD4+ T lymphocytes and limited activation of CD8+ T lymphocytes

Members of the Sydney Blood Bank Cohort (SBBC) have been infected with an attenuated strain of HIV-1 with a natural nef/LTR mutation and have maintained relatively stable CD4(+) T lymphocyte counts for 14-18 years. Flow cytometric analysis was used to examine the phenotype of CD4(+) and CD8(+) T lymphocytes in these subjects, including the immunologically important naive (CD45RA(+)CD62L(+)), primed (CD45RO(+)), and activated (CD38(+)HLA-DR+ and CD28(-)) subsets. The median values were compared between the SBBC and control groups, comprising age-, sex-, and transfusion-matched HIV-1-uninfected subjects; transfusion-acquired HIV-1-positive LTNPs; and sexually acquired HIV-1-positive LTNPs. Members of the SBBC not only had normal levels of naive CD4(+) and CD8(+) T lymphocytes, but had primed CD45RO(+) CD4(+) T lymphocytes at or above normal levels. Furthermore, these primed cells expressed markers suggesting recent exposure to specific antigen. SBBC members exhibited variable activation of CD8(+) T lymphocytes. In particular, SBBC members with undetectable plasma HIV-1. RNA had normal levels of activated CD8(+) T lymphocytes. Therefore, the result of long-term infection with natural nef/LTR mutant HIV-1 in these subjects suggests a decreased cytopathic effect of attenuated HIV-1 on susceptible activated CD4(+) T lymphocyte subsets in vivo, and minimal activation of CD8(+) T lymphocytes.