Peripheral blood natural killer cell reconstitution after highly active antiretroviral therapy.

Abstract

The concentration of natural killer (NK) cells is lower in HIV-infected patients than in HIV-seronegative individuals, and a low concentration of NK cells in the blood has been associated with rapid disease progression [1]. In addition, increased plasma HIV-1 RNA level is related to low levels of NK cytotoxicity and low NK cell activity, both of which are associated with a high risk of progression to a CD4 T lymphocyte count of less than 100 × 106 and to death in HIV-infected patients [2]. However, the effect of HAART on NK cells is not fully defined. We studied the number of CD16 NK cells in a series of 66 consecutive HIV-infected patients (age 38 ± 8 years; 55 men, 11 women), in whom the viral load remained below 200 copies/ml after treatment with highly active antiretroviral therapy (HAART) (lamivudine plus stavudine plus saquinavir in 15 patients, lamivudine plus stavudine plus indinavir in 25 patients, 11 other HAART combinations in the other 26 patients). As a control group, we evaluated 10 patients, matched for age and sex, with the same risk practices but showing an unsatisfactory response to HAART. Lymphocyte subsets were determined by flow cytometry (Orthocytoron, Raritan, NJ, USA) using TRIO reagents (OKT4A-FITC/OKT8-PE/OKT3CyP and NK-FITC/OKT319APE/OKT3CyP). Plasma HIV-1 RNA was measured using the Amplicor HIV-1 monitor (Roche, Branchburg, NJ, USA), with 200 copies/ml as the lower limit of detection. Lymphocyte subsets and HIV-1 RNA were monitored at the outset and at 4, 12, 24, 36 and 48 weeks after treatment. The basal conditions (mean ± SD) were: CD4 cells: 215 ± 64.5 cells/μl (range 4–729); CD8 cells: 796 ± 573.6 cells/μl (range 81–3023); CD19 B cells: 102 ± 97.02 cells/μl (range 8–606); CD16 NK cells: 60.45 ± 43.05 (range 7–205); and viral load (log10 RNA copies/ml): 4.48 ± 1.17 (range 2.0–6.6). For statistical analysis, Wilcoxon, Spearman's and Kruskal–Wallis tests were performed. Our results (Fig. 1) did not show a statistical increase in CD16 NK cells at 4 weeks after HAART. However, peripheral blood CD16 NK cells increased at 12 weeks of HAART in HIV-1-infected patients in whom the viral load after treatment was below 200 copies/ml. This increase was maintained at 24, 36 and 48 weeks. Taking into account the whole treatment period, a positive correlation between both CD4 lymphocytes and NK cell levels was found in the HIV-1-treated patients. The NK cell number was not significantly different in the control group of HIV-1 individuals, whose viral load did not descend below detectable levels (data not shown).Fig. 1.: Levels of CD4 cells, CD8 cells, CD16 natural killer cells and HIV-1 viral load in patients who have received highly active antiretroviral therapy over 12 months.Previously, changes in NK levels were not observed in patients with HAART [3]. However, the follow-up of the patients in our study was 12 months and was restricted to those patients with a viral load that remained under detectable levels, whereas the NK cell number analysis in Lederman et al. [3] was at 12 weeks and only 17 out of 40 patients achieved HIV-1 RNA levels below 100 copies/ml. Very little is known about the survival, proliferation kinetics and distribution of NK cells after HAART. It could be postulated that the NK cell reconstitution after HAART presented here is directly related to the decreased virus burden and subsequent cessation of NK cell destruction, or to NK cell expansion secondary to an amelioration of the T cell compartment. In this respect, it is likely that normalized levels of cytokines after CD4 T cell reconstitution support NK cell differentiation. However, the possibility of a peripheral expansion of the pre-existing mature NK cell pool, as was suggested for T cells, cannot be excluded. This hypothesis is supported by the observation reported in this study, that the CD4 T cell increase precedes the CD16 NK increase by 2 months. It is also possible that an effective control of virus replication by potent drug combinations offers hope of effective therapeutic assistance to non-major histocompatibility complex restricted cytotoxicity in controlling HIV infection. Further studies will be necessary to elucidate these questions and clarify the effect of HAART on NK functional capacity. José Luis Villanuevaa Javier Caballeroa Marta Del Nozala Berta Sanchezb Pompeyo Vicianaa Arístides Alarcóna José Peñac