Interleukin-7 promotes HIV persistence during antiretroviral therapy

Abstract

HIV persists in latently infected memory CD4(+) T cells during antiretroviral therapy (ART). When administered to HIV-infected subjects receiving suppressive ART, interleukin-7 (IL-7) increases the number of CD4(+) T cells by promoting their survival and proliferation. However, little is known about the impact of IL-7 on HIV persistence during ART. By isolating large numbers of CD4(+) T cells from HIV-infected subjects, we demonstrate that IL-7 enhances viral production in productively infected cells but does not disrupt viral latency in latently infected cells. When administered to virally suppressed subjects, IL-7 led to the rapid proliferation of memory CD4(+) T cells, which resulted in a 70% increase in the absolute number of circulating CD4(+) T cells harboring integrated HIV DNA 4 weeks after therapy. The genetic diversity of the viral reservoir increased transiently in the majority of the subjects studied before returning to baseline values. Altogether, our results indicate that IL-7 promotes the mechanisms of HIV persistence during ART by enhancing residual levels of viral production and inducing proliferation of latently infected cells, and suggest that IL-7 does not represent a suitable candidate therapeutic strategy for HIV eradication. This trial was registered at www.clinicaltrials.gov as #NCT00099671 (AIDS Clinical Trials Group protocol 5214).

Figure 1

IL-7 shows minimal effect on viral production in CD4⁺ T cells from virally suppressed subjects. (A) Viral production in cell-culture supernatants of CD4⁺ T cells isolated from subjects receiving ART and stimulated with 10 ng/mL IL-7 or with antibodies to CD3/CD28 for 6 days in the presence of ARVs. Viral release was measured by ultrasentitive RT-PCR in the supernatant. (B) Viral production in CD4⁺ T cells from IL-7 nonresponders and IL-7 responders in media alone or after IL-7 stimulation, relative to the positive control (CD3/CD28). (C) Expression of the IL-7 receptor (CD127) in CD4⁺ T cells after stimulation with IL-7 or with antibodies to CD3/CD28 was measured by flow cytometry. (D) Effect of IL-7 on the expression of activation and proliferation markers. CD4⁺ T cells from 13 virally suppressed subjects were stimulated with 10 ng/mL IL-7 or with antibodies to CD3/CD28 for 6 days. The levels of expression of Ki67, HLA-DR, and PD-1 on live CD4⁺ T cells were measured by flow cytometry.

Figure 2

IL-7 enhances viral production in productively infected cells but does not disrupt HIV latency. (A) Quantification of viral production in cell-culture supernatants of CD4⁺ T cells isolated from 7 viremic untreated HIV-infected subjects. Similar methods than in Figure 1A were used. (B) Correlation between the levels of spontaneous viral production and viral production induced by IL-7 in CD4⁺ T cells isolated from 7 viremic subjects. (C) Viral production in total CD4⁺ T cells and highly pure resting memory CD4⁺ T cells following stimulation with IL-7 and CD3/CD28 in 4 virally suppressed subjects.

Figure 3

IL-7 administration increases the absolute number of CD4⁺ T cells harboring integrated HIV DNA. (A) Fold changes in the frequencies of CD4⁺ T cells expressing Ki67, PD-1, and HLA-DR, 4 and 28 days following IL-7 administration as measured by flow cytometry. (B) Frequency of CD4⁺ T cells harboring integrated HIV DNA at baseline and 28 days after IL-7 administration. (C) Number of CD4⁺ T cells harboring integrated HIV DNA per milliliter of blood at baseline and 28 days after IL-7 administration. (D) Change from baseline in the absolute number of integrated HIV DNA copies per milliliter of blood in subjects who received IL-7 and in placebo controls. (E) Correlation between the change in CD4⁺ T-cell numbers and the increase in the frequency of cells harboring HIV integrated DNA per milliliter of blood.

Figure 4

IL-7 administration transiently increases the genetic diversity of the HIV reservoir. (A) Neighbor-joining trees derived from HIV sequences obtained from 4 virally suppressed subjects who received IL-7. CD4⁺ T cells from samples collected at baseline (green dots) and after 4 (blue dots) and 28 days (red dots) following IL-7 therapy were sorted, and a minimum of 20 clones were sequenced in each case. The numbers near nodes indicate the percentage of bootstrap replicates. The scale refers to the distance between sequences. (B) HIV genetic diversities at baseline and 4 and 28 days after IL-7 administration. Each dot represents the mean genetic distance between one given clone and the entire population. The horizontal bar represents the mean and is reflecting the genetic diversity of the viral population at the different time points.