Sein, C. E. | Search bioRxiv

bioRxiv2022

Development of SARS-CoV-2 mRNA vaccines encoding spike N-terminal and receptor binding domains

With the success of mRNA vaccines against coronavirus disease 2019 (COVID-19), strategies can now focus on improving vaccine potency, breadth, and stability. We present the design and preclinical evaluation of domain-based mRNA vaccines encoding the wild-type spike-protein receptor-binding (RBD) and/or N-terminal domains (NTD). An NTD-RBD linked candidate vaccine, mRNA-1283, showed improved antigen expression, antibody responses, and stability at refrigerated temperatures (2-8{degrees}C) compared with the clinically available mRNA-1273, which encodes the full-length spike protein. In mice administered mRNA-1283 as a primary series, booster, or variant-specific booster, similar or greater immune responses and protection from viral challenge were observed against wild-type, beta, delta, or omicron (BA. 1) compared with mRNA-1273 immunized mice, especially at lower vaccine dosages. These results support clinical assessment of mRNA-1283 (NCT05137236). One Sentence SummaryA domain-based mRNA vaccine, mRNA-1283, is immunogenic and protective against SARS-CoV-2 and emerging variants in mice.

immunology↗

bioRxiv2018

DivIVA concentrates mycobacterial cell envelope assembly for initiation and stabilization of polar growth

In many model organisms, diffuse patterning of cell wall peptidoglycan synthesis by the actin homolog MreB enables the bacteria to maintain their characteristic rod shape. In Caulobacter crescentus and Escherichia coli, MreB is also required to sculpt this morphology de novo. Mycobacteria are rod-shaped but expand their cell wall from discrete polar or sub-polar zones. In this genus, the tropomyosin-like protein DivIVA is required for the maintenance of cell morphology. DivIVA has also been proposed to direct peptidoglycan synthesis to the tips of the mycobacterial cell. The precise nature of this regulation is unclear, as is its role in creating rod shape from scratch. We find that DivIVA localizes nascent cell wall and covalently associated mycomembrane but is dispensable for the assembly process itself. Mycobacterium smegmatis rendered spherical by peptidoglycan digestion or by DivIVA depletion are able to regain rod shape at the population level in the presence of DivIVA. At the single cell level, there is a close spatiotemporal correlation between DivIVA foci, rod extrusion and concentrated cell wall synthesis. Thus, although the precise mechanistic details differ from other organisms, M. smegmatis also establish and propagate rod shape by cytoskeleton-controlled patterning of peptidoglycan. Our data further support the emerging notion that morphology is a hardwired trait of bacterial cells.

microbiology↗