Coronavirus spike protein fragment-containing chimeric virus-like particles stimulate human dendritic cell maturation

Introduction. Viral capsid proteins can assemble into virus-like particles lacking infectivity and bearing parental virus antigens or artificially introduced antigens from other pathogens. At least some of such particles are highly immunogenic and could serve as a platform for promising vaccines. In this work, we assessed an effect of virus-like particles decorated with a SARS-CoV-2 spike protein fragment on human dendritic cell phenotype and functional properties. Materials and methods. The virus-like particles were assembled using chimeric molecules obtained by fusing genetic sequences encoding a norovirus major capsid protein VP1 fragment and a coronavirus spike protein fragment, including the receptor-binding domain. Dendritic cells were obtained from monocytes in vitro. Results. Incubation of immature dendritic cells with virus-like particles induced their phenotypic and functional maturation. The former was revealed by significantly increased expression of HLA-DR, CD80, CD86 and CD83. Dendritic cell phenotype after incubation with virus-like particles at the maximum concentration of 10 μg/ml did not differ significantly from that of mature dendritic cells in positive control. Along with phenotypic maturation, virus-like particles caused a manifold increase in the production of pro-inflammatory tumor necrosis factor-α, anti-inflammatory interleukin-10, as well as interleukin-6, which can stimulate both antibody synthesis and cellular pro-inflammatory reactions. The pronounced stimulation of dendritic cells by virus-like particles coated with coronavirus antigens evidence about successful particle recognition. Finally, we discuss plausible mechanisms for recognition of such virus-like particles by dendritic cell receptors. Conclusion. It has been shown that chimeric virus-like particles induced phenotypic and functional dendritic cell maturation, which is manifested by markedly elevated expression of functionally important membrane molecules, as well as a manifold rise in production of cytokines with a wide functional range. In our opinion, the data obtained indicate a promise of using virus-like particles based on norovirus proteins to display SARS-CoV-2 antigens.