Existing mRNA COVID-19 vaccines have shown efficacy in reducing severe cases and fatalities. However, their effectiveness against infection caused by emerging SARS-CoV-2 variants has waned considerably, necessitating the development of variant vaccines. Ideally, next-generation vaccines will be capable of eliciting broader and more sustained immune responses to effectively counteract new variants. Additionally, in vitro assays that more closely represent virus neutralization in humans would greatly assist in the analysis of protective vaccine-induced antibody responses. Here, we present findings from a SARS-CoV-2 VLP vaccine encompassing three key structural proteins: Spike (S), Envelope (E), and Membrane (M). The VLP vaccine effectively produced neutralizing antibodies as determined by surrogate virus neutralization test, and induced virus-specific T-cell responses: predominantly CD4⁺, although CD8⁺ T cell responses were detected. T cell responses were more prominent with vaccine delivered with AddaVax compared to vaccine alone. The adjuvanted vaccine was completely protective against live virus challenge in mice. Furthermore, we utilized air–liquid-interface (ALI)-differentiated human nasal epithelium (HNE) as an in vitro system, which authentically models human SARS-CoV-2 infection and neutralization. We show that immune sera from VLP-vaccinated mice completely neutralized SARS-CoV-2 virus infection, demonstrating the potential of ALI-HNE to assess vaccine induced Nab.

Protein C is a critical regulator of haemostasis, exerting anticoagulant, anti-inflammatory and cytoprotective effects through tightly coordinated interact

Adenoviruses, adenoviral vector vaccines, and gene delivery systems have been implicated in thrombosis/thrombocytopenia syndrome. The underlying cause remains unknown. We have previously hypothesized that infection of megakaryocytes (MKs), the progenitor cells of platelets, plays a central role in adenovirus- or adenoviral vector-induced thrombosis/thrombocytopenia. Further, recent work has highlighted that the MK population comprises multiple subsets, including cells with immune function, and we propose that this MK subset is involved in adenoviral infection and the subsequent response. To determine whether MKs are permissive to infection by recombinant adenovirus encoding the SARS-CoV-2 spike protein, and whether infection is associated with phenotypic changes. In this work, we generated adenovirus vectors based on the adenovirus 5 strain, with a green fluorescence protein reporter gene and encoding or not the SARS-CoV-2 Spike protein. Megakaryoblastic cell lines and MKs derived from mouse bone marrow and differentiated with thrombopoietin were exposed to adenoviral vectors, and infection was analyzed using flow cytometry and fluorescence microscopy. The primary finding of this study is that MKs were permissive to infection by recombinant adenoviruses carrying the Spike gene of ß-SARS-CoV-2, with higher rates of infection in mature MKs. Furthermore, the effect of adenoviral infection on the cell surface proteins CD41, CD42, and CXCR4 was investigated. Cell cultures stimulated with bacterial lipopolysaccharide, with and without concurrent adenoviral infection, demonstrated that lipopolysaccharide stimulation and adenoviral infection at moderate multiplicity of infection drove increased surface expression of the α chemokine receptor CXCR4, whereas adenoviral infection at a high multiplicity of infection reduced CXCR4 expression. We found that adenoviral infection was higher in higher-ploidy CD41⁺CD42⁺ and CXCR4^hi MKs, implicating these receptors in the MK response to adenoviral infection.