Selective activation and expansion of regulatory T cells using lipid encapsulated mRNA encoding a long-acting IL-2 mutein

Interleukin-2 (IL-2) is critical for regulatory T cell (Treg) function and homeostasis. At low doses, IL-2 can suppress immune pathologies by expanding Tregs that constitutively express the high affinity IL-2Rα subunit. However, even low doses IL-2, signaling through the IL2-Rβ/γ complex, may lead to the activation of proinflammatory, non-Treg T cells, so improving specificity toward Tregs may be desirable. Here we used messenger RNAs (mRNA) to encode a half-life-extended human IL-2 mutein (HSA-IL2m) with mutations promoting reliance on IL-2Rα. Our data show that IL-2 mutein subcutaneous delivery in lipid-encapsulated mRNA nanoparticles selectively activates and expands Tregs in mice and non-human primates, as well as reduces disease severity in mouse models of acute graft versus host disease and experimental autoimmune encephalomyelitis. Single cell RNA sequencing of murine splenic CD4+ T cells identifies multiple Treg states with distinct response dynamics following IL-2 mutein treatment. Our results thus demonstrate the potential of mRNA-encoded HSA-IL2m immunotherapy to treat autoimmune diseases. Spleens were collected from C57BL/6 female mice dosed with HSA-IL2wt or HSA-IL2m at 0.05mpk at 2 days and 4 days post injection (n = 3 mice each condition and timepoints) and from untreated mice for baseline comparison (n = 2). Each spleen was homogenized by mechanical disruption and CD4 T cells were isolated using a negative selection magnetic enrichment kit (StemCell). CD4 T cells collected from each treatment condition were pooled across individual mice, resulting in five single-cell suspensions. For each sample, the purity exceeded 98% purity and viability exceeded 99%. Each sample was diluted to a 1 million cells per mL. Library preparation. 10x Genomics 3’ Library and Gel Bead Kit (Chromium Next GEM v3.1 516 1000128, 1000157, 1000213) and Single Cell Chip G kit (Chromium Next GEM 1000127) were used to prepare libraries using the 10x Genomics Chromium Controller according to the manufacture’s guidelines (CG00052 Rev D). Two chips were used with a target 10,000 cells collected in each lane. The five pooled samples were each split into technical replicates and distributed to the two chips as follows: The untreated pooled sample was split into four technical replicates with two replicates distributed to each chip. For the treated conditions, each pooled sample was split into three technical replicates, with one replicate from Day 2 and two replicates from Day 4 on Chip 1, and two replicates from Day 2 and one replicate from day 4 on Chip 2.