Newly approved subunit and mRNA vaccines for respiratory syncytial virus (RSV) demonstrate effectiveness in preventing severe disease, with protection exceeding 80% primarily through the generation of antibodies. An alternative vaccine platform called self-amplifying RNA (saRNA) holds promise in eliciting humoral and cellular immune responses. We evaluate the immunogenicity of a lipid nanoparticle (LNP)-formulated saRNA vaccine called SMARRT.RSV.preF, encoding a stabilized form of the RSV fusion protein, in female mice and in non-human primates (NHPs) that are either RSV-naïve or previously infected. Intramuscular vaccination with SMARRT.RSV.preF vaccine induces RSV neutralizing antibodies and cellular responses in naïve mice and NHPs. Importantly, a single dose of the vaccine in RSV pre-exposed NHPs elicits a dose-dependent anamnestic humoral immune response comparable to a subunit RSV preF vaccine. Notably, SMARRT.RSV.preF immunization significantly increases polyfunctional RSV.F specific memory CD4+ and CD8+ T-cells compared to RSV.preF protein vaccine. Twenty-four hours post immunization with SMARRT.RSV.preF, there is a dose-dependent increase in the systemic levels of inflammatory and chemotactic cytokines associated with the type I interferon response in NHPs, which is not observed with the protein vaccine. We identify a cluster of analytes including IL-15, TNFα, CCL4, and CXCL10, whose levels are significantly correlated with each other after SMARRT.RSV.preF immunization. These findings suggest saRNA vaccines have the potential to be developed as a prophylactic RSV vaccine based on innate, cellular, and humoral immune profiles they elicit.
© 2024. The Author(s).

A key barrier to the development of vaccines that induce broadly neutralizing antibodies (bnAbs) against human immunodeficiency virus (HIV) and other viruses of high antigenic diversity is the design of priming immunogens that induce rare bnAb-precursor B cells. The high neutralization breadth of the HIV bnAb 10E8 makes elicitation of 10E8-class bnAbs desirable; however, the recessed epitope within gp41 makes envelope trimers poor priming immunogens and requires that 10E8-class bnAbs possess a long heavy chain complementarity determining region 3 (HCDR3) with a specific binding motif. We developed germline-targeting epitope scaffolds with affinity for 10E8-class precursors and engineered nanoparticles for multivalent display. Scaffolds exhibited epitope structural mimicry and bound bnAb-precursor human naive B cells in ex vivo screens, protein nanoparticles induced bnAb-precursor responses in stringent mouse models and rhesus macaques, and mRNA-encoded nanoparticles triggered similar responses in mice. Thus, germline-targeting epitope scaffold nanoparticles can elicit rare bnAb-precursor B cells with predefined binding specificities and HCDR3 features.
© 2024. The Author(s).

Prime-2-CoV_Beta is a novel Orf virus (ORFV)-based COVID-19 vaccine candidate expressing both the nucleocapsid and spike proteins of SARS-CoV-2 with the receptor-binding domain (RBD) of the Beta strain. This candidate was shown to be safe and immunogenic in a first-in-human Phase I clinical trial. With the shift in the immune landscape toward the Omicron variant and the widespread vaccine- and/or infection-derived immunity, further pre-clinical research was needed to characterize Prime-2-CoV. Here, we quantified the humoral and cellular response to Prime-2-CoV_Beta in pre-immunized mice and compared the protective efficacy of mono- and bivalent variant-based Prime-2-CoV vaccine candidates in hamsters. Prime-2-CoV_Beta induced robust humoral and cellular immune responses in naïve animals but did not further boost antibody titers in the tested setting when given as repeat booster at short interval. We furthermore showed that Prime-2-CoV_Beta-based mono- and bivalent immunization strategies produced comparable immunogenicity and protection from infection. Our results highlight the potential of the Orf virus as a vaccine platform against SARS-CoV-2 and potentially other infectious viruses.

Due to the intracellular expression of Foxp3 it is impossible to purify viable Foxp3+ cells on the basis of Foxp3 staining. Consequently CD4+Foxp3+ regulatory T cells (Tregs) in mice have mostly been characterized using CD4+CD25+ T cells or GFP-Foxp3 reporter T cells. However, these two populations cannot faithfully represent Tregs as the expression of CD25 and Foxp3 does not completely overlap and GFP+Foxp3+ reporter T cells have been reported to be functionally altered. The aim of this study was to characterize normal Tregs without separating Foxp3+ and Foxp3- cells for the expression of the main functional molecules and proliferation behaviors by flow cytometry and to examine their gene expression characteristics through differential gene expression. Our data showed that the expressions of Foxp3, CD25, CTLA-4 (both intracellular and cell surface) and PD-1 was mostly confined to CD4+ T cells and the expression of Foxp3 did not completely overlap with the expression of CD25, CTLA-4 or PD-1. Despite higher levels of expression of the T cell inhibitory molecules CTLA-4 and PD-1, Tregs maintained higher levels of Ki-67 expression in the homeostatic state and had greater proliferation in vivo after allo-activation than Tconv. Differential gene expression analysis revealed that resting Tregs exhibited immune activation markers characteristic of activated Tconv. This is consistent with the flow data that the T cell activation markers CD25, CTLA-4, PD-1, and Ki-67 were much more strongly expressed by Tregs than Tconv in the homeostatic state.
Copyright © 2024 Liu, Baines, Niessen, Heer, Clark, Bishop and Trevillian.

Cancer cells can evade immune elimination by activating immunosuppressive signaling pathways in the tumor microenvironment (TME). Targeting immunosuppressive signaling pathways to promote antitumor immunity has become an attractive strategy for cancer therapy. Aurora-A is a well-known oncoprotein that plays a critical role in tumor progression, and its inhibition is considered a promising strategy for treating cancers. However, targeting Aurora-A has not yet got a breakthrough in clinical trials. Recent reports have indicated that inhibition of oncoproteins may reduce antitumor immunity, but the role of tumor-intrinsic Aurora-A in regulating antitumor immunity remains unclear. In this study, we demonstrated that in tumors with high lymphocyte infiltration (hot tumors), higher tumor-intrinsic Aurora-A expression is associated with a better prognosis in CRC patients. Mechanically, tumor-intrinsic Aurora-A promotes the cytotoxic activity of CD8+ T cells in immune hot CRC via negatively regulating interleukin-16 (IL-16), and the upregulation of IL-16 may impair the therapeutic effect of Aurora-A inhibition. Consequently, combination treatment with IL-16 neutralization improves the therapeutic response to Aurora-A inhibitors in immune hot CRC tumors. Our study provides evidence that tumor-intrinsic Aurora-A contributes to anti-tumor immunity depending on the status of lymphocyte infiltration, highlighting the importance of considering this aspect in cancer therapy targeting Aurora-A. Importantly, our results suggest that combining Aurora-A inhibitors with IL-16-neutralizing antibodies may represent a novel and effective approach for cancer therapy, particularly in tumors with high levels of lymphocyte infiltration.
© 2024. The Author(s).