Identifying the immunologic and virologic consequences of discontinuing antiretroviral therapy in HIV-infected patients is of major importance in developing long-term treatment strategies for patients with HIV-1 infection. We designed a trial to characterize these parameters after interruption of highly active antiretroviral therapy (HAART) in patients who had maintained prolonged viral suppression on antiretroviral drugs. Eighteen patients with CD4 ؉ T cell counts > 350 cells͞l and viral load below the limits of detection for >1 year while on HAART were enrolled prospectively in a trial in which HAART was discontinued. Twelve of these patients had received prior IL-2 therapy and had low frequencies of resting, latently infected CD4 cells. Viral load relapse to >50 copies͞ml occurred in all 18 patients independent of prior IL-2 treatment, beginning most commonly during weeks 2-3 after cessation of HAART. The mean relapse rate constant was 0.45 (0.20 log 10 copies) day ؊1 , which was very similar to the mean viral clearance rate constant after drug resumption of 0.35 (0.15 log 10 copies) day ؊1 (P ‫؍‬ 0.28). One patient experienced a relapse delay to week 7. All patients except one experienced a relapse burden to >5,000 RNA copies͞ml. Ex vivo labeling with BrdUrd showed that CD4 and CD8 cell turnover increased after withdrawal of HAART and correlated with viral load whereas lymphocyte turnover decreased after reinitiation of drug treatment. Virologic relapse occurs rapidly in patients who discontinue suppressive drug therapy, even in patients with a markedly diminished pool of resting, latently infected CD4 ؉ T cells.HIV-1 infection ͉ antiretroviral drugs ͉ viral load ͉ relapse ͉ CD4

Despite years of plasma HIV-RNA levels <40 copies per milliliter during combination antiretroviral therapy (cART), the majority of HIV-infected patients exhibit persistent seropositivity to HIV-1 and evidence of immune activation. These patients also show persistence of proviruses of HIV-1 in circulating peripheral blood mononuclear cells. Many of these proviruses have been characterized as defective and thus thought to contribute little to HIV-1 pathogenesis. By combining 5′LTR-to-3′LTR single-genome amplification and direct amplicon sequencing, we have identified the presence of “defective” proviruses capable of transcribing novel unspliced HIV-RNA (usHIV-RNA) species in patients at all stages of HIV-1 infection. Although these novel usHIV-RNA transcripts had exon structures that were different from those of the known spliced HIV-RNA variants, they maintained translationally competent ORFs, involving elements of gag, pol, env, rev, and nef to encode a series of novel HIV-1 chimeric proteins. These novel usHIV-RNAs were detected in five of five patients, including four of four patients with prolonged viral suppression of HIV-RNA levels <40 copies per milliliter for more than 6 y. Our findings suggest that the persistent defective proviruses of HIV-1 are not “silent,” but rather may contribute to HIV-1 pathogenesis by stimulating host-defense pathways that target foreign nucleic acids and proteins.

A SIGNIFICANT proportion (up to 70%) of individuals experience an acute clinical syndrome of varying severity associated with primary infection with the human immunodeficiency virus (HIV). We report here studies on six individuals who showed an acute HIV syndrome which generally resolved within four weeks, concomitant with a dramatic downregulation of viraemia. To characterize the T-cell-mediated primary immune response to HIV, we used combined semiquantitative polymerase chain reaction assay and cytofluorometry to analyse the T-cell antigen receptor repertoire in sequential peripheral blood mononuclear cells from the patients. We found major oligoclonal expansions in a restricted set of variable-domain beta-chain (V beta) families. Cells expressing the expanded V beta s predominantly expressed the CD8 T-cell differentiation antigen and mediated HIV-specific cytotoxicity. Major oligoclonal expansions of these CD8+ T lymphocytes may represent an important component of the primary immune response to viral infections and may help to clarify both the immunopathogenic and the protective mechanisms of HIV infection.

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The effects of HIV infection upon the thymus and peripheral T cell turnover have been implicated in the pathogenesis of AIDS. In this study, we investigated whether decreased thymic output, increased T cell proliferation, or both can occur in HIV infection. We measured peripheral blood levels of TCR rearrangement excision circles (TREC) and parameters of cell proliferation, including Ki67 expression and ex vivo bromodeoxyuridine incorporation in 22 individuals with early untreated HIV disease and in 15 HIV-infected individuals undergoing temporary interruption of therapy. We found an inverse association between increased T cell proliferation with rapid viral recrudescence and a decrease in TREC levels. However, during early HIV infection, we found that CD45RO−CD27high (naive) CD4+ T cell proliferation did not increase, despite a loss of TREC within naive CD4+ T cells. A possible explanation for this is that decreased thymic output occurs in HIV-infected humans. This suggests that the loss of TREC during HIV infection can arise from a combination of increased T cell proliferation and decreased thymic output, and that both mechanisms can contribute to the perturbations in T cell homeostasis that underlie the pathogenesis of AIDS.

We examined the effects of human immunodeficiency virus infection on the turnover of CD4 and CD8 T lymphocytes in 17 HIV-infected patients by 30 min in vivo pulse labeling with bromodeoxyuridine (BrdU). The percentage of labeled CD4 and CD8 T lymphocytes was initially higher in lymph nodes than in blood. Labeled cells equilibrated between the two compartments within 24 h. Based on mathematical modeling of the dynamics of BrdU-labeled cells in the blood, we identified rapidly and slowly proliferating subpopulations of CD4 and CD8 T lymphocytes. The percentage, but not the decay rate, of labeled CD4 or CD8 cells in the rapidly proliferating pool correlated significantly with plasma HIV RNA levels for both CD4 (r = 0.77, P < 0.001) and CD8 (r = 0.81, P < 0.001) T cells. In six patients there was a geometric mean decrease of greater than 2 logs in HIV levels within 2 to 6 mo after the initiation of highly active antiretroviral therapy; this was associated with a significant decrease in the percentage (but not the decay rate) of labeled cells in the rapidly proliferating pool for both CD4 (P = 0.03) and CD8 (P < 0.001) T lymphocytes. Neither plasma viral levels nor therapy had an effect on the decay rate constants or the percentage of labeled cells in the slowly proliferating pool. Monocyte production was inversely related to viral load (r = −0.56, P = 0.003) and increased with therapy (P = 0.01). These findings demonstrate that HIV does not impair CD4 T cell production but does increase CD4 and CD8 lymphocyte proliferation and death by inducing entry into a rapidly proliferating subpopulation of cells.

No abstract

To evaluate the effects of HIV infection on T cell turnover, we examined levels of DNA synthesis in lymph node and peripheral blood mononuclear cell subsets by using ex vivo labeling with BrdUrd. Compared with healthy controls (n ‫؍‬ 67), HIV-infected patients (n ‫؍‬ 57) had significant increases in the number and fraction of dividing CD4 ؉ and CD8 ؉ T cells. Higher percentages of dividing CD4 ؉ and CD8 ؉ T cells were noted in patients with the higher viral burdens. No direct correlation was noted between rates of T cell turnover and CD4 ؉ T cell counts. Marked reductions in CD4 ؉ and CD8 ؉ T cell proliferation were seen in 11͞11 patients 1-12 weeks after initiation of highly active antiretroviral therapy (HAART). These reductions persisted for the length of the study (16 -72 weeks). Decreases in naïve T cell proliferation correlated with increases in the levels of T cell receptor rearrangement excision circles. Division of CD4 ؉ and CD8 ؉ T cells increased dramatically in association with rapid increases in HIV-1 viral loads in 9͞9 patients 5 weeks after termination of HAART and declined to pre-HAART-termination levels 8 weeks after reinitiation of therapy. These data are consistent with the hypothesis that HIV-1 infection induces a viral burden-related, global activation of the immune system, leading to increases in lymphocyte proliferation.AIDS ͉ proliferation ͉ immune activation ͉ T cell receptor rearrangement excision circles H IV-1 infection is associated with a failure in T cell homeostasis, resulting in a gradual decline in CD4 ϩ T cell numbers. Studies examining lymphocyte turnover rates during infection with HIV or simian immunodeficiency virus have generated mixed results. Most of these discrepancies are likely the result of differences in the methods used to measure turnover rates, the use of longitudinal as opposed to cross-sectional cohorts, or the sensitivity and specificity of the assays used.An initial study of lymphocyte turnover rates using 3 Hthymidine to label CD4 ϩ and CD8 ϩ T cells found increased turnover rates in patients with HIV-1 infection (1). Studies of lymphocyte turnover derived through analysis of immediate changes in CD4 ϩ T cell counts in the blood after highly active antiretroviral therapy (HAART) also led to estimates of high rates of CD4 turnover (2-4), although others have suggested that lymphocyte redistribution may be the major cause for CD4 increases immediately after HAART (5-8). Measurements of lymphocyte proliferation using Ki-67, BrdUrd, and 2 H-glucose have yielded varying results (9-19); however, the general consensus is that T cell proliferation is increased in HIV͞simian immunodeficiency virus-infected subjects. Variations in these studies may be caused by the difference in sample numbers, cross-sectional versus longitudinal studies, patient cohort composition, and whether one is measuring the absolute or fractional level of cell division.To gain better insight into the immunopathogenic effects of HIV-1 infection, and to attempt to resolve some of the controversy...