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Abstract: Current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines are effective against severe disease and death, but do not prevent viral infections, probably due to the limited mucosal immunity induced by intramuscular administration of the vaccine. Fusion of SARS-CoV-2 subunit immunogens with a human IgG Fc backbone can be used as a mucosal vaccine but its effectiveness in delivery in animal models, and its immunogenicity and the vaccine-induced protection against viral infections requires further studies. Here we investigate a bivalent RBD-Fc vaccine that includes the spike receptor-binding domains (RBDs) of the ancestral and BQ.1.1 variant of SARS-CoV-2. Ex vivo fluorescent imaging demonstrates that this vaccine can be effectively delivered to the lungs of mice through intranasal administration, with enhancement of retention in the nasal cavity and lung parenchyma. In mice, the vaccine elicited potent and broad-spectrum antibody responses against different variants including KP.3 which could persist for at least 3 months after booster. Importantly, it was able to induce RBD-specific mucosal IgA responses. Further, heterologous intranasal immunisation with adeno-vectored Chadv1 and RBD-Fc elicited both potent neutralising antibody and T cell responses. Immunised BALB/c and K18-hACE2-transgenic mice were also protected against viral challenge of XBB.1 and viral transmission was effectively limited in hamsters through intranasal immunisation. This work thus demonstrates the potential of RBD-Fc antigens as mucosal vaccines for prevention of breakthrough infections and onward transmission. Moreover, Fc-fusion proteins can be used as an effective mucosal vaccine strategy which can be used either alone or in combination with other vaccine technology to constitute heterologous immunisations, enabling strong protection against SARS-CoV-2 and other respiratory viruses.

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Abstract: Toll-like receptor (TLR) agonists are of interest in immunotherapy and cancer vaccines. The most common agonists of TLR2 are based on Pam2Cys or Pam3Cys. In the former, two palmitoyl (Pam) fatty acids are linked to a glycerylcysteine motif by ester linkages. Pam3Cys is analogous but contains an extra Pam group on the α-amine. Here, we compare the self-assembly in aqueous solution of the parent Pam2CysOH and Pam3Cys amino acid conjugates to that of Pam2CysSK4 and Pam3CysSK4 which are potent TLR2 agonists bearing the CysSK4 peptide sequence. All four conjugates exhibit a critical aggregation concentration above which self-assembled structures are formed. We find through a combination of small-angle X-ray scattering (SAXS), cryogenic transmission electron microscopy (cryo-TEM), and confocal fluorescence microscopy remarkable differences in self-assembled nanostructures. Pam2CysOH and Pam3CysOH both form unilamellar vesicles, although these are larger for the latter compound, an effect ascribed to enhanced membrane rigidity. This is in contrast to previously reported morphologies for Pam2CysSK4 and Pam3CysSK4, which are spherical micelles or predominantly wormlike micelles, respectively [Hamley, I. W.; et al. Toll-like Receptor Agonist Lipopeptides Self-Assemble into Distinct Nanostructures. Chem. Comm. 2014, 50, 15948-15951]. We also examine the effect of introduction in the bulky N-terminal Fmoc [fluorenylmethoxycarbonyl] group on the self-assembly of Fmoc-Pam2CysOH. This compound also forms vesicles (above a critical aggregation concentration, determined from dye probe fluorescence experiments) in aqueous solution, larger than those for Pam2CysOH and with a population of perforated/compound vesicles. The carboxyl-coated (and amino-coated for Pam2CysOH) vesicles demonstrated here represent a promising system for future development toward bionanotechnology applications such as immune therapies. Conjugates Pam2CysOH, Pam2CysSK4, and Pam3CysSK4 show good cytocompatibility at low concentrations, and in fact, the cell compatibility extends over a wider concentration range for Pam2CysOH. The TLR2/6 agonist activity was assessed using an assay that probes secreted alkaline phosphatase (SEAP) in NF-κB-SEAP reporter HEK293 cells expressing human TLR2 and TLR6, and Pam2CySOH shows significant activity, although not to the extent of Pam2CysSK4 or Pam3CysSK4. Thus, Pam2CysOH in particular is of interest as a vesicle-forming TLR2/6 agonist and stimulator of immune response.

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Abstract: The success of the poliovirus (PV) vaccines has enabled the near-eradication of wild PV, however, their continued use post-eradication poses concerns, due to the potential for virus escape during vaccine manufacture. Recombinant virus-like particles (VLPs) that lack the viral genome remove this risk. Here, we demonstrate the production of PV VLPs for all three serotypes by controlled fermentation using Pichia pastoris. We determined the cryo-EM structure of a new PV2 mutant, termed SC5a, in comparison to PV2-SC6b VLPs described previously and investigated the immunogenicity of PV2-SC5a VLPs. Finally, a trivalent immunogenicity trial using bioreactor-derived VLPs of all three serotypes in the presence of Alhydrogel adjuvant, showed that these VLPs outperform the current IPV vaccine in the standard vaccine potency assay, offering the potential for dose-sparing. Overall, these results provide further evidence that yeast-produced VLPs have the potential to be a next-generation polio vaccine in a post-eradication world.

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Abstract: The storage and distribution of vital protein therapeutics presents several complex challenges. Many medicines and vaccines need stable, temperature-controlled environments and chemical additives (excipients) such as preservatives to keep them effective and safe for use. This requires cold storage infrastructure and reliable energy sources which not only puts the responsibility on the user but causes accessibility and affordability challenges, especially in developing countries where resources are limited. Fig. 1 Fig. 1 Now researchers from the UK Universities of Manchester, Glasgow and Warwick have designed the world’s first hydrogel technology for the storage and distribution of crucial medicines and other biopharmaceuticals without the need for refrigeration or chemical additives. The aim is to provide more robust and equitable storage and delivery systems, benefitting everyone worldwide.

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Abstract: Nipah virus (NiV) is a highly pathogenic paramyxovirus capable of causing severe respiratory and neurologic disease in humans. Currently, there are no licensed vaccines or therapeutics against NiV, underscoring the urgent need for the development of countermeasures. The NiV surface-displayed glycoproteins, NiV-G and NiV-F, mediate host cell attachment and fusion, respectively, and are heavily targeted by host antibodies. Here, we describe a vaccination-derived neutralizing monoclonal antibody, mAb92, that targets NiV-F. Structural characterization of the Fab region bound to NiV-F (NiV-F–Fab92) by cryo-electron microscopy analysis reveals an epitope in the DIII domain at the membrane distal apex of NiV-F, an established site of vulnerability on the NiV surface. Further, prophylactic treatment of hamsters with mAb92 offered complete protection from NiV disease, demonstrating beneficial activity of mAb92 in vivo. This work provides support for targeting NiV-F in the development of vaccines and therapeutics against NiV.