The unenlarged lymph nodes of HIV-1-infected, asymptomatic patients with high CD4 T cell counts are sites for virus replication and CD4 T cell proliferation. The impact of highly active antiretroviral therapy

Abstract

The efficacy of triple drug therapy for HIV-1 infection encourages its early use to prevent damage to the immune system. We monitored the effects of such therapy on 12 patients with 14-75-mo histories of minimal disease, i.e., CD4+ counts constantly >500/microl and little or no lymph node enlargement. In this way, we could first determine the extent of viral replication and immunoarchitectural changes in unenlarged nodes early in disease, and second follow the response to triple therapy in plasma and lymphoid tissue in tandem. As is known for lymph nodes with more advanced disease, the germinal centers showed productively infected T cells, i.e., CD4+CD1a-CD68- cells labeling intensely for HIV-1 RNA after in situ hybridization. The unenlarged nodes also showed extensive HIV-1 RNA retention on a well-preserved, follicular dendritic cell (FDC) network, and the follicles were abnormal. There were numerous CD8+ cells, many expressing TIA-1 granule antigen. Also, in contrast to normal follicles, CD4+ T cell proliferation was active, with marked increases in the number of cycling, Ki-67+CD4+CD45R0+ cells. After 28 d and 3 mo of therapy, productively infected T cells decreased dramatically and often were not apparent. The labeling of the FDC network for viral RNA also decreased, but not for gag protein. We conclude that HIV-1 replicates and accumulates in lymphoid organs before damage of the immune system, that at this stage of disease de novo production of T cells occurs in the lymphoid tissue, and that the infection is sensitive to triple drug therapy in both plasma and lymph nodes.

Figure 1

Methodological aspects of HIV-1 RNA detection. Adjacent lymph node sections were treated by boiling in a pressure cooker (right) or with proteinase K (left), and then hybridized with radiolabeled antisense RNA probes. The autoradiograms were photographed under bright field microscopy. The boiled sections contained more numerous, discretely labeled, productively infected or hot cells (arrows, right), and tissue preservation was better. Proteinase K–treated sections, in contrast, exhibited a more heavily labeled FDC network of RNA (arrow, left).

Figure 2

Direct relationship between the number of productively infected cells in lymph node sections and the level of plasma RNA (correlation coefficient: 0.65). The data are mean numbers of hot GC cells per lymph node section.

Figure 3

Architecture and immunolabeling of infected lymph nodes. (a) CD4⁺ T cells (red) were abundant in the T cell area (T), but were also found in the B cell follicle, as is typical of normal lymph nodes. (b) However, in HIV-1 infection, CD4⁺ T cells (red) showed an increase in the extent of labeling for Ki-67 (blue; arrows, double positive cells). (c) In HIV-1 infection, CD8⁺ T cells (brown, arrow) were abundant in GCs (B) that were full of Ki-67⁺ B blasts (blue). (d) The FDC network (arrows) was visualized with the Ki-Mp4 monoclonal antibody.

Figure 4

Effect of triple drug therapy on lymph node HIV-1 RNA. (a and b) The in situ hybridization signal for viral RNA in the FDC network is shown by reflected light (turquoise, arrow) before (a) and after (b) 28 d of therapy. (c and d) The immunolabeling signal for viral p24 or gag protein in the FDC network is shown (red) together with the in situ hybridization for viral RNA (turquoise). Before therapy (c), the red p24 (arrow) was obscured by the silver grains over viral RNA. After therapy (d), p24 persisted and was readily visible because the viral RNA signal was so weak.