Title

Dual therapy of Interleukin-21 and anti-α4β7 antibody administration during ART-treated SIV promotes immunological responses and ameliorates dysbiosis in rhesus macaques

Presenter

Samuel D. Johnson

Authors

S.D. Johnson^1,2, M. Pino³, A. Acharya¹, K. Nguyen³, F. Villinger⁴, M. Paiardini^3,5, S.N. Byrareddy^1,6,7

Institutions

¹University of Nebraska Medical Center, Department of Pharmacology and Experimental Neuroscience, Omaha, United States, ²University of Nebraska Medical Center, Department of Pathology and Microbiology, Omaha, United States, ³Emory National Primate Research Center, Emory University, Division of Microbiology and Immunology, Atlanta, United States, ⁴University of Louisiana at Lafayette, New Iberia Research Center, New Iberia, United States, ⁵Emory University School of Medicine, Department of Pathology and Laboratory Medicine, Atlanta, United States, ⁶University of Nebraska Medical Center, Department of Genetics, Cell Biology and Anatomy, Omaha, United States, ⁷University of Nebraska Medical Center, Department of Biochemistry and Molecular Biology, Omaha, United States

BACKGROUND: Despite effective antiretroviral therapies (ART), a cure for HIV remains elusive, necessitating new therapeutic strategies. Further, intestinal epithelium damage, mucosal immune depletion, and HIV-associated dysbiosis contribute to chronic immune activation and resultant sequelae, even during ART. Both IL-21 and anti-a4ß7 administration modulate gut lymphocyte milieu improving mucosal barrier function, thus limiting inflammation and plasma viral loads (VLs). We hypothesized that combining these interventions would synergistically further improve outcomes.
METHODS: Sixteen rhesus macaques (RMs) were inoculation with 300 TCID50 SIVmac239. Six weeks post acquisition (p.a.), ART (TDF+FTC+DTG) was initiated and administered until interruption at week 72 p.a. (ATI). Starting week 64 p.a., the experimental group (n=7; one excluded for remaining viremic during ART) was administered seven rounds of 100 µg/kg subcutaneous IL-21-IgFc weekly and 50 mg/kg intravenous anti-a4ß7 antibody every three weeks. Animals were sacrificed at week 92 pa. VLs, intact proviral DNA assays in CD4+ T-cells, flow cytometry, and fecal 16S rRNA sequencing were performed longitudinally.
RESULTS: All RMs rebounded after ATI. Controls experienced progressive increases in VL reaching pre-ART setpoints after day 100 ATI. In contrast, and despite higher initial rebound, dual-treated RMs controlled viral replication better compared to pre-ART setpoints, with log₁₀ 2.2 copies/mL lower VLs by sacrifice (P<0.0001). At endpoint, dual-treated RMs had log₁₀ 1.4 copies/mL lower VLs than controls. Reservoir size was not different between groups. Following ATI, controls experienced increases in PD-1 expression on CD4+ TCMs (P<0.0001), with no significant changes in dual-treated RMs. Notably, reservoir size at dual therapy baseline correlated with PD-1+ TCMs (P=0.04) and predicted VLs ATI (P=0.007). Finally, dual therapy facilitated SIV-associated dysbiosis recovery (increased Firmicutes (P=0.001), decreased Spirochaetes (P=0.02), decreased Proteobacteria (P=0.02)) compared to controls (week 72 p.a.). Roseburia (a butyrate-producing Firmicute) abundance was predictive of PD-1+ TCMs after therapy (P=0.004) and subsequent viral loads (P=0.004).
CONCLUSIONS: We demonstrate that combining IL-21 and anti-a4ß7 treatments inhibits PD-1 expression on CD4+ TCMs, ameliorates dysbiosis, and limits VLs after ATI. These findings highlight the importance of targeting PD-1 and microbiome composition for improving immune responses against SIV and provide a roadmap for future mucosal immunotherapies in ongoing cure efforts.

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