Suppression of HIV replication by lymphoid tissue CD8+ cells correlates with the clinical state of HIV-infected individuals

Abstract

Lymphoid tissues from asymptomatic HIV-infected individuals, as compared with symptomatic HIV-infected subjects, show limited histopathological changes and lower levels of HIV expression. In this report we correlate the control of HIV replication in lymph nodes to the non-cytolytic anti-HIV activity of lymphoid tissue CD8+ cells. Five subjects at different stages of HIV-related disease were studied and the ability of their CD8+ cells, isolated from both lymphoid tissue and peripheral blood, to inhibit HIV replication was compared. CD8+ cells from lymphoid tissue and peripheral blood of two HIV-infected long-term survivors suppressed HIV replication at a low CD8+:CD4+ cell ratio of 0.1. The CD8+ cells from the lymphoid tissue of a third asymptomatic subject suppressed HIV replication at a CD8+:CD4+ cell ratio of 0.25; the subject's peripheral blood CD8+ cells showed this antiviral response at a lower ratio of 0.05. The lymphoid tissue CD8+ cells from two AIDS patients were not able to suppress HIV replication, and the peripheral blood CD8+ cells of only one of them suppressed HIV replication. The plasma viremia, cellular HIV load as well as the extent of pathology and virus expression in the lymphoid tissue of the two long-term survivors, were reduced compared with these parameters in the three other subjects. The data suggest that the extent of anti-HIV activity by CD8+ cells from lymphoid tissue relative to peripheral blood correlates best with the clinical state measured by lymphoid tissue pathology and HIV burden in lymphoid tissues and blood. The results add further emphasis to the importance of this cellular immune response in controlling HIV pathogenesis.

Figure 1

In situ hybridization to detect HIV RNA in lymphoid tissues. (A) The lymph node of the long-term survivor, subject 1, showing a single HIV RNA signal in the germinal center. (B) The lymph node of the long-term survivor, subject 2, showing individual HIV RNA positive cells. (C) The tonsil tissue of subject 3 reveals many germinal centers harboring several individual cells containing HIV RNA. (D) The lymphoid tissue of subject 4 (which showed late-stage follicular lysis consistent with progression of HIV-related disease) shows HIV trapped by residual FDCs and some cells within the germinal centers containing HIV RNA.