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Microscopy core facilities are critical to modern research, providing access to advanced microscopy applications and expert support. Despite this, global benchmarking data on facility operations, staffing and sustainability remain limited. We conducted the first truly global international survey of microscopy facilities, capturing 196 responses across 34 countries and six continents. The survey includes 74 questions covering facility leaders, facilities, optical microscopy, electron microscopy and image analysis. The results reveal distinct benchmarking data and operational trends on a global and continent basis. This will enable facility leaders, institutions and policymakers to strengthen their microscopy infrastructure, optimise facility staffing and operations, and ensure equitable access to advanced microscopy applications.
Abstract Circular RNA (circRNA) is an emerging vaccine modality that is proposed to improve stability, reduce reactogenicity and extend antigen expression compared with linear mRNA. However, the relative contributions to vaccine performance of its covalently closed structure, its purity, and of nucleotide modifications remain poorly described. Here, we systematically dissected these parameters in vivo across two antigen systems. We identified RNA quality as a major determinant of circRNA reactogenicity, with differences in innate immune activation tracking with the presence of residual RNA species in less refined preparations. In contrast, highly purified circRNA exhibited markedly reduced reactogenicity compared with linear mRNA, independent of nucleotide modification. Despite these differences, circRNA and mRNA vaccines elicited comparable antibody titres and T cell responses, indicating that reduced innate activation does not enhance adaptive immune magnitude. Notably, incorporating N 6 -methyladenosine (m 6 A) did not affect reactogenicity or antigen expression but selectively enhanced antibody quality, increasing binding affinity and neutralisation capacity. CircRNA vaccination also altered the anatomical distribution of germinal centre responses, reducing splenic antigen-specific germinal centre B cells while preserving lymph node responses. Together, these findings show that circRNA vaccine performance is governed by RNA preparation quality and epitranscriptomic tuning rather than innate activation alone.
Vaccines capable of eliciting broadly neutralizing antibodies (bnAbs) are a major goal for pandemic preparedness. A challenge across vaccine fields is how to deliberately recruit the rare B cell clones that recognize conserved epitopes shared across diverse viral variants. BnAbs have been known to frequently emerge through extensive somatic hypermutation during affinity maturation, here we describe an alternative mechanism for bnAb selection. We designed an mRNA vaccine in which two antigenically distinct (severe acute respiratory syndrome coronavirus 2) SARS-CoV-2 variant’s (Omicron and Delta; O-Δ) receptor binding domains (RBDs) are physically fused on a single polypeptide. This design is predicted to favor B cell antigen receptors capable of engaging conserved epitopes on both RBDs with enhanced avidity. A matched nondivergent tandem RBD (Delta-Delta; Δ-Δ) served as a control. In mice, immunization elicited potent antibody responses and increased the frequency of cross-reactive B cells, recognizing Delta, Omicron, and the 2002 pandemic strain SARS-CoV RBDs. Using multicolor RBD tetramers and single-cell B cell receptor sequencing, we show that breadth arises via two distinct pathways. The divergent vaccine preferentially enriches clonally distinct cross-reactive B cells (not present within non-cross-reactive B cell pools) with low levels of somatic hypermutation, consistent with selection of germline-biased precursors. In contrast, the matched control vaccine yields cross-reactivity primarily within existing clonal lineages (clonal overlap between cross-reactive and non-cross-reactive cells) and at higher mutational burdens, consistent with affinity-maturation-driven acquisition of breadth. This work establishes a simple, modular antigen-design principle in which juxtaposing appropriately divergent antigens on a single scaffold promotes the enrichment of bnAb-prone B cells.
