Spike substitution T813S increases Sarbecovirus fusogenicity by enhancing the usage of TMPRSS2.

SARS-CoV Spike (S) protein shares considerable homology with SARS-CoV-2 S, especially in the conserved S2 subunit (S2). S protein mediates coronavirus receptor binding and membrane fusion, and the latter activity can greatly influence coronavirus infection. We observed that SARS-CoV S is less effective in inducing membrane fusion compared with SARS-CoV-2 S. We identify that S813T mutation is sufficient in S2 interfering with the cleavage of SARS-CoV-2 S by TMPRSS2, reducing spike fusogenicity and pseudoparticle entry. Conversely, the mutation of T813S in SARS-CoV S increased fusion ability and viral replication. Our data suggested that residue 813 in the S was critical for the proteolytic activation, and the change from threonine to serine at 813 position might be an evolutionary feature adopted by SARS-2-related viruses. This finding deepened the understanding of Spike fusogenicity and could provide a new perspective for exploring Sarbecovirus' evolution.

CircRNA based multivalent neuraminidase vaccine induces broad protection against influenza viruses in mice.

Developing broad-spectrum influenza vaccines is crucial for influenza control and potential pandemic preparedness. Here, we reported a novel vaccine design utilizing circular RNA (circRNA) as a delivery platform for multi-subtype neuraminidases (NA) (influenza A N1, N2, and influenza B Victoria lineage NA) immunogens. Individual NA circRNA lipid nanoparticles (LNP) elicited robust NA-specific antibody responses with neuraminidase inhibition activity (NAI), preventing the virus from egressing and infecting neighboring cells. Additionally, the administration of circRNA LNP induced cellular immunity in mice. To achieve a universal influenza vaccine, we combined all three subtypes of NA circRNA-LNPs to generate a trivalent circRNA vaccine. The trivalent vaccine elicited a balanced antibody response against all three NA subtypes and a Th1-biased immune response in mice. Moreover, it protected mice against the lethal challenge of matched and mismatched H1N1, H3N2, and influenza B viruses, encompassing circulating and ancestral influenza virus strains. This study highlights the potential of delivering multiple NA antigens through circRNA-LNPs as a promising strategy for effectively developing a universal influenza vaccine against diverse influenza viruses.

Cold to Hot: Binary Cooperative Microneedle Array-Amplified Photoimmunotherapy for Eliciting Antitumor Immunity and the Abscopal Effect.

In this study, an ingenious core-shell structure microneedle (CSMN) array was designed to synergistically boost robust immune response by the intralesional codelivery of photosensitizer and indoleamine 2,3-dioxygenase (IDO) blockade. Photosensitizer indocyanine green was encapsulated into chitosan nanoparticles (ICG-NPs), followed by concentrating on the tip shell of microneedles. 1-Methyl-tryptophan was loaded into the cross-linked poly(vinyl pyrrolidone) and poly(vinyl alcohol) gel as the microneedle core. Through the direct deposition of the ICG-NP-loaded tips into the tumor site with uniform spatial distribution, the CSMNs effectively converted the near-infrared laser into heat to ablate primary tumors, generated tumor-associated antigens and damage-associated molecular patterns, and promoted the maturation of dendritic cells and the secretion of immunostimulatory cytokines. The IDO blockade further reversed the IDO-mediated immunosuppression, ultimately arousing an effective systematic immune response. The in vivo results showed that 80% of the melanoma tumor was eradicated, followed by a relapse-free survival in more than 120 days. Of note, this synergistic strategy significantly inhibited lung metastasis and controlled the development of already metastasized tumors. Our work provides a new, generalizable framework for using the microneedle-based photothermal therapy to initiate antitumor immunity and sensitize tumors to IDO blockade.