Maintenance of Intestinal Th17 Cells and Reduced Microbial Translocation in SIV-infected Rhesus Macaques Treated with Interleukin (IL)-21

Abstract

In pathogenic HIV and SIV infections of humans and rhesus macaques (RMs), preferential depletion of CD4+ Th17 cells correlates with mucosal immune dysfunction and disease progression. Interleukin (IL)-21 promotes differentiation of Th17 cells, long-term maintenance of functional CD8+ T cells, and differentiation of memory B cells and antibody-secreting plasma cells. We hypothesized that administration of IL-21 will improve mucosal function in the context of pathogenic HIV/SIV infections. To test this hypothesis, we infected 12 RMs with SIVmac239 and at day 14 post-infection treated six of them with rhesus rIL-21-IgFc. IL-21-treatment was safe and did not increase plasma viral load or systemic immune activation. Compared to untreated animals, IL-21-treated RMs showed (i) higher expression of perforin and granzyme B in total and SIV-specific CD8+ T cells and (ii) higher levels of intestinal Th17 cells. Remarkably, increased levels of Th17 cells were associated with reduced levels of intestinal T cell proliferation, microbial translocation and systemic activation/inflammation in the chronic infection. In conclusion, IL-21-treatment in SIV-infected RMs improved mucosal immune function through enhanced preservation of Th17 cells. Further preclinical studies of IL-21 may be warranted to test its potential use during chronic infection in conjunction with antiretroviral therapy.

Interleukin-21 combined with ART reduces inflammation and viral reservoir in SIV-infected macaques

“…The IL-21-treated RMs received 2 cycles of 6 weekly doses -1 at the time of ART initiation and 1 later on while on ART -plus 4 additional weekly doses at the time of ART interruption (orange arrows in Figure 1). The weekly dose regimen was selected on the basis of our previous study of IL-21 administration during acute SIV infection of RMs (16), as well as of our experience with in vivo administration of other cytokines in nonhuman primates (NHPs), in which weekly doses were better tolerated and showed a better response profile than did more frequent dosages (18)(19)(20). The remaining 8 RMs were treated only with ART and served as controls.…”

“…As such, numerous concepts and products are aggressively being explored as novel interventions to be added to standard ART in order to reduce or possibly eliminate these immunological and/or virological aspects of residual HIV disease on ART. In the current study, we administered IL-21, a potent immunomodulatory cytokine, to ART-treated, (16). Last, IL-21 is currently being evaluated in several phase I and II cancer clinical trials, with limited toxicity and encouraging single-agent activity (17,(47)(48)(49).…”

“…To the best of our knowledge, these are the first in vivo data directly supporting a causal link between residual immune activation and virus persistence during ART. While, on the basis of our data, we propose increased mucosal integrity as a key contributor to the reduced residual immune activation during ART in IL-21-treated RMs, the mechanisms by which a reduction of immune activation can limit virus persistence under ART may be very complex and may include (a) a reduction in the number of activated CD4 + T cells that serve as targets for the infection and that may become a persistent reservoir, and (b) a better maintenance and/or restoration of HIV/SIV-specific immune responses, thus resulting in a better clearance of productively infected cells and/or latently infected cells in which virus infection has been following in vitro stimulation with PMA and ionomycin (16). PBMC-, LN-, and RB-derived cells, isolated as described above, were resuspended to 3 × 10 6 cells/ml in complete RPMI 1640 medium.…”

“…Remarkably, in IL-21-treated animals, the frequencies of Th17 cells on days 85 and 135 p.i. were IgFc fusion protein during acute SIV infection of RMs results in the preservation of intestinal Th17 cells, improved mucosal immune function, and reduced microbial translocation (16).…”

“…The levels of blood (percentages and counts), LN (percentages), and RB (percentages) CD8 + T cells (Supplemental Figure 2) and their subsets (data not shown) were overall very similar in IL-21-treated and control RMs, with no significant differences between the 2 groups at any single experimental time point. Previous studies showed that IL-21 stimulates the production of cytotoxic molecules in CD8 + T cells in humans in vitro (21) and in acutely SIV-infected RMs in vivo (16). Hence, we sought to determine by flow cytometry the longitudinal expression of intracellular perforin, granzyme B (GrB), and T-bet in blood and LN CD8 + T cells.…”