The SARS-CoV-2 pandemic highlighted the potential of mRNA vaccines in rapidly responding to emerging pathogens. However, immunity induced by conventional mRNA vaccines wanes quickly, requiring frequent boosters. Self-amplifying RNA (saRNA) vaccines, which extend antigen expression via self-replication, offer a promising strategy to induce more durable immune responses. In this study, we developed an saRNA vaccine encoding Zika virus (ZIKV) membrane and envelope proteins and evaluated its efficacy in mice. A single vaccination elicited strong humoral and cellular immune responses and reduced viral loads but only for 28 days. By day 84, antibody titers and T cell responses had significantly declined, resulting in reduced efficacy. To address this, we evaluated agonist antibodies targeting the T cell costimulatory molecules OX40 and 4-1BB. Coadministration of agonist antibodies enhanced CD8+ T cell responses to vaccination, resulting in sustained immunity and reduced viral loads at day 84. Depletion and passive transfer studies verified that long-term antiviral immunity was primarily CD8+ T cell dependent, with minimal contributions from antibody responses. These findings suggest that agonists targeting members of the tumor necrosis receptor superfamily, such as OX40 and 4-1BB, might enhance the durability of saRNA vaccine-induced protection, addressing a key limitation of current mRNA vaccine platforms.

Stem-like T cells selectively contribute to autoimmunity, but the activities that promote their pathogenicity are incompletely understood. Here, we identify the transcription coregulator OCA-B as a driver of the pathogenic maturation of stem-like CD4+ T cell to promote autoimmune demyelination. Using two human multiple sclerosis (MS) datasets, we show that POU2AF1, the gene encoding OCA-B, is elevated in CD4+ T cells from MS patients. We show that T cell-intrinsic OCA-B loss protects mice from experimental autoimmune encephalomyelitis (EAE) while preserving responses to viral CNS infection. In EAE models driven by antigen reencounter, OCA-B deletion nearly eliminates CNS infiltration, proinflammatory cytokine production and clinical disease. OCA-B-expressing CD4+ T cells of mice primed with autoantigen express an encephalitogenic gene program and preferentially confer disease. In a relapsing-remitting EAE model, OCA-B loss protects mice specifically at relapse. During remission, OCA-B promotes the expression of Tcf7, Slamf6, and Sell in proliferating CNS T cell populations. At relapse timepoints, OCA-B loss results in both the accumulation of an immunomodulatory CD4+ T cell population expressing Ccr9 and Bach2, and loss of pro-inflammatory gene expression from Th17 cells. These results identify OCA-B as a driver of pathogenic CD4+ T cells.

The continuing evolution of SARS-CoV-2 variants challenges the durability of existing spike (S)-based COVID-19 vaccines. We hypothesized that vaccines composed of both S and nucleocapsid (N) antigens would increase the durability of protection by strengthening and broadening cellular immunity compared with S-based vaccines. To test this, we examined the immunogenicity and efficacy of wild-type SARS-CoV-2 S- and N-based DNA vaccines administered individually or together to K18-hACE2 mice. S, N, and S + N vaccines all elicited polyfunctional CD4+ and CD8+ T cell responses and provided short-term cross-protection against Beta and Omicron BA.2 variants, but only co-immunization with S + N vaccines provided long-term protection against Omicron BA.2. Depletion of CD4+ and CD8+ T cells reduced the long-term efficacy, demonstrating a crucial role for T cells in the durability of protection. These findings underscore the potential to enhance long-lived protection against SARS-CoV-2 variants by combining S and N antigens in next-generation COVID-19 vaccines.
© 2024. The Author(s).

A hallmark feature of pancreatic ductal adenocarcinoma (PDAC) is massive intratumoral fibrosis, designated as desmoplasia. Desmoplasia is characterized by the expansion of cancer-associated fibroblasts (CAFs) and a massive increase in extracellular matrix (ECM). During fibrogenesis, distinct genes become reactivated specifically in fibroblasts, e.g., the disintegrin metalloprotease, ADAM12. Previous studies have shown that immunotherapeutic ablation of ADAM12+ cells reduces fibrosis in various organs. In preclinical mouse models of PDAC, we observe ADAM12 expression in CAFs as well as in tumor cells but not in healthy mouse pancreas. Therefore, we tested prophylactic and therapeutic vaccination against ADAM12 in murine PDAC and observed delayed tumor growth along with a reduction in CAFs and tumor desmoplasia. This is furthermore associated with vascular normalization and alleviated tumor hypoxia. The ADAM12 vaccine induces a redistribution of CD8+ T cells within the tumor and cytotoxic responses against ADAM12+ cells. In summary, vaccination against the endogenous fibroblast target ADAM12 effectively depletes CAFs, reduces desmoplasia and delays the growth of murine PDACs. These results provide proof-of-principle for the development of vaccination-based immunotherapies to treat tumor desmoplasia.
© 2024. The Author(s).

Innate lymphoid cells (ILCs) are critical for intestinal adaptation to microenvironmental challenges, and the gut mucosa is characterized by low oxygen. Adaptation to low oxygen is mediated by hypoxia-inducible transcription factors (HIFs), and the HIF-1α subunit shapes an ILC phenotype upon acute colitis that contributes to intestinal damage. However, the impact of HIF signaling in NKp46+ ILCs in the context of repetitive mucosal damage and chronic inflammation, as it typically occurs during inflammatory bowel disease, is unknown. In chronic colitis, mice lacking the HIF-1α isoform in NKp46+ ILCs show a decrease in NKp46+ ILC1s but a concomitant rise in neutrophils and Ly6Chigh macrophages. Single-nucleus RNA sequencing suggests enhanced interaction of mesenchymal cells with other cell compartments in the colon of HIF-1α KO mice and a loss of mucus-producing enterocytes and intestinal stem cells. This was, furthermore, associated with increased bone morphogenetic pathway-integrin signaling, expansion of fibroblast subsets, and intestinal fibrosis. In summary, this suggests that HIF-1α-mediated ILC1 activation, although detrimental upon acute colitis, protects against excessive inflammation and fibrosis during chronic intestinal damage.
© 2024 Nelius et al.