Dynamics of immune reconstitution and activation markers in HIV+ treatment-naïve patients treated with raltegravir, tenofovir disoproxil fumarate and emtricitabine

Abstract

Background: The dynamics of CD4+ T cell reconstitution and changes in immune activation and inflammation in HIV-1 disease following initiation of antiretroviral therapy (ART) are incompletely defined and their underlying mechanisms poorly understood.

Methods: Thirty-nine treatment-naïve patients were treated with raltegravir, tenofovir DF and emtricitabine. Immunologic and inflammatory indices were examined in persons with sustained virologic control during 48 weeks of therapy.

Results: Initiation of ART increased CD4+ T cell numbers and decreased activation and cell cycle entry among CD4+ and CD8+ T cell subsets, and attenuated markers of coagulation (D-dimer levels) and inflammation (IL-6 and TNFr1). These indices decayed at different rates and almost all remained elevated above levels measured in HIV-seronegatives through 48 weeks of viral control. Greater first and second phase CD4+ T cell restoration was related to lower T cell activation and cell cycling at baseline, to their decay with treatment, and to baseline levels of selected inflammatory indices, but less so to their changes on therapy.

Conclusions: ART initiation results in dynamic changes in viral replication, T cell restoration, and indices of immune activation, inflammation, and coagulation. These findings suggest that determinants of T cell activation/cycling and inflammation/coagulation may have distinguishable impact on immune homeostasis.

Trial registration: Clinicaltrials.gov NCT00660972.

Figure 1. Initiation of antiretroviral therapy (ART) results in an increase in the number of CD4+T cells and a decrease in the number of CD8+ T cells.

Absolute CD4+ and CD8+ T cell counts were obtained in real time on fresh whole blood samples. Lymphocytes were identified by flow cytometry based on size and granularity; T cell subsets were identified by positive expression of CD4 or CD8. The numbers of circulating A) CD4+ and B) CD8+ T cells within this HIV-1 infected patient population changed significantly from baseline by day 2 (p<0.001 and p<0.002, respectively), but did not reach levels seen in healthy controls within 48 weeks of ART treatment. C) naïve (CD45RA+ CCR7+) and D) central memory (CM, CD45RA-CCR7+) CD4+ T cell numbers increased significantly by day 2 (p<0.001) and day 7 (p=0.001) respectively. Symbols used in the figure: N = Normal controls (in blue). 0 = Baseline. D = Day (The two tick-marks between “0” and “D14” are Day 2 and Day 7). W = Week. * = Change from baseline significantly different from 0 (Wilcoxon signed rank p ≤0.05) . x = Significant difference from the normal controls (Wilcoxon rank sum p ≤0.05). - Horizontal bars represent 25^th (Q1), 50^th (Median), and 75^th percentiles. … Dotted line (in red) connects the medians over time.

Figure 2. Proportions of activated (CD38+HLA-DR+) and cycling (Ki67+) CD4+ and CD8+ T cells decreased following initiation of ART.

Among both A) CD4+ and B) CD8+ T cell populations, initiation of raltegravir plus emtricitabine/tenofovir resulted in a significant decrease from baseline in the proportion of activated cells by 2 days and 7 days (p= 0.05 and 0.015, respectively). By week 48, the proportions of activated CD4+ and CD8+ T cells in these patients did not approach the proportions measured in healthy controls. Also among both C) CD4+ and D) CD8+ T cell populations, initiation of ART significantly decreased the proportions of Ki67+ cells by week 8 and by day 7 respectively (p<0.001 and p=0.028). E) Naïve CD4+ T cells (CD4+,CD45RA+, CCR7+) and F) CM CD4+ T cells (CD4+,CD45RA-, CCR7+) that express Ki67 were significantly reduced from baseline by week 8 (p=0.005 and p=0.001, respectively). In all four T cell subsets, proportions of Ki67+ cells did not approach the proportions seen in healthy controls by week 48 of the study. Symbols used in the figure: N = Normal controls (in blue). 0 = Baseline. D = Day (The two tick-marks between “0” and “D14” are Day 2 and Day 7). W = Week. * = Change from baseline significantly different from 0 (Wilcoxon signed rank p ≤0.05) . x = Significant difference from the normal controls (Wilcoxon rank sum p ≤0.05). - Horizontal bars represent 25^th (Q1), 50^th (Median), and 75^th percentiles. … Dotted line (in red) connects the medians over time.

Figure 3. Markers of inflammation and coagulation are reduced following initiation of ART.

Plasma samples were thawed and levels of A) interleukin-6 (IL-6) B) tumor necrosis factor receptor type 1 (TNFr1) C) D-dimers D) Lipopolysaccharide (LPS) and E) CD14 (sCD14) were measured. Initiation of ART resulted in significant decreases from baseline in plasma levels of IL-6 and TNFr1 by week 4 (p=0.002 and p=0.038) D-dimer levels were significantly reduced by day 7 (p=0.031). Levels of sCD14 were significantly reduced by day 2 following initiation of therapy (p<0.001). LPS levels were significantly reduced from baseline 24 weeks after initiation of ART (p<0.001). None of these markers, except for IL-6, consistently reached the levels seen in healthy controls by the end of the study. Symbols used in the figure: N = Normal controls (in blue). 0 = Baseline. D = Day (The two tick-marks between “0” and “D14” are Day 2 and Day 7). W = Week. * = Change from baseline significantly different from 0 (Wilcoxon signed rank p ≤0.05) . x = Significant difference from the normal controls (Wilcoxon rank sum p ≤0.05). - Horizontal bars represent 25^th (Q1), 50^th (Median), and 75^th percentiles. … Dotted line (in red) connects the medians over time.