Enhanced T cell recovery in HIV-1-infected adults through IL-7 treatment

Abstract

HIV infection results in CD4+ T cell deficiency, but efficient combination antiretroviral therapy (c-ART) restores T cells and decreases morbidity and mortality. However, immune restoration by c-ART remains variable, and prolonged T cell deficiency remains in a substantial proportion of patients. In a prospective open-label phase I/IIa trial, we evaluated the safety and efficacy of administration of the T cell regulator IL-7. The trial included 13 c-ART-treated HIV-infected patients whose CD4+ cell counts were between 100 and 400 cells/microl and plasma HIV RNA levels were less than 50 copies/ml. Patients received a total of 8 subcutaneous injections of 2 different doses of recombinant human IL-7 (rhIL-7; 3 or 10 microg/kg) 3 times per week over a 16-day period. rhIL-7 was well tolerated and induced a sustained increase of naive and central memory CD4+ and CD8+ T cells. In the highest dose group, 4 patients experienced transient increases in viral replication. However, functional assays showed that the expanded T cells responded to HIV antigen by producing IFN-gamma and/or IL-2. In conclusion, in lymphopenic HIV-infected patients, rhIL-7 therapy induced substantial functional and quantitative changes in T cells for 48 weeks. Therefore, patients may benefit from intermittent therapy with IL-7 in combination with c-ART.

Figure 1. Effects of rhIL-7 therapy on peripheral blood lymphocyte subsets.

The absolute lymphocyte count from complete blood counts and flow cytometry–based frequency were used to determine evolution of (A) absolute counts of CD3⁺ T cells, CD3⁺CD4⁺ T cells, and CD3⁺CD8⁺ T cells; (B) absolute counts of mature B cells and percentages of pro-B and transitional B cells; (C) absolute counts of NK and NKT cells; and (D) fold increase from baseline of CD4⁺ and CD8⁺ T cells expressing CD127. Mean ± SEM for each cohort is shown. *P < 0.05 versus 0 d; Wilcoxon test.

Figure 2. CD4⁺ T cell count prior to rhIL-7 treatment predicts the magnitude of CD4⁺ T cell increase after rhIL-7 treatment.

The linear correlation between CD4⁺ T cell count before treatment at 0 d and 12 wk relative to rhIL-7 treatment initiation at each dose is shown. Overall regression using a Spearman test showed a significant correlation between CD4⁺ T cell counts at entry CD4⁺ T cell responses in both groups and in the global population of IL-7–treated patients.

Figure 3. rhIL-7 therapy induces a preferential increase of naive and central memory CD4⁺ and CD8⁺ T cells.

(A) Representative flow cytometry analysis of CD4⁺ and CD8⁺ T cell populations from a single representative subject treated at the 3-μg/kg dose. Numbers within the plots indicate the percent of each T cell population: naive (N; CD45RA⁺CD27⁺), central memory (CM; CD45RA^–CD27⁺), effector memory and effector (EM+E; CD45RA^–CD27^–), terminally differentiated effector (TE; CD45RA⁺CD27^–), and RTE (CD45RA⁺CD31^hi). (B) Time evolution of CD4⁺ and CD8⁺ T cell subsets. Mean ± SEM for each cohort is shown. *P < 0.05 versus 0 d; Wilcoxon test.

Figure 4. rhIL-7 therapy is not associated with T cell activation, but increases T cell cycling.

Analyses were performed in patients treated with the 10-μg/kg dose of rhIL-7. (A and B) Percent cells in CD4⁺ (A) and CD8⁺ (B) T cell subpopulations expressing Ki67 via flow cytometry. Mean ± SEM for each T cell subset is shown. Ki67 expression significantly increased at 14 d. (C) Percent CD4⁺ and CD8⁺ activated T cells (HLA-DR⁺CD38⁺). Error bars denote SD. *P versus 0 d; Wilcoxon test.

Figure 5. rhIL-7 expanded T cells respond to polyclonal and antigenic stimulation.

PBMCs were collected at the indicated time points, cryopreserved, and then thawed before analysis. (A) Proliferation in response to TCR stimulation (anti-CD3 plus anti-CD28) was measured by [³H] incorporation. Similar proliferation levels were observed at each time point. Error bars denote SD. (B) Both CD4⁺ and CD8⁺ T cells produced IFN-γ and IL-2 in response to SEB at levels comparable to baseline 28 d and 12 wk after rhIL-7 therapy. Analyses were performed in patients treated with 10 μg/kg rhIL-7. Error bars denote SD. (C) rhIL-7 therapy increased the capacity of CD4⁺ T cells to respond to HIV Gag and CMV antigens by secreting IFN-γ and/or IL-2. All 7 patients treated with 10 μg/kg rhIL-7 were analyzed.