Small Fish, Big Insights: A Zebrafish Tale of Tulane Virus Tropism

Sahaana Chandran, University of Arkansas, Fayetteville

Sahaana Chandran - Department of Food Science, Center for Food Safety, University of Arkansas System Division of Agriculture, Fayetteville, AR, USA Kristen E. Gibson - Department of Food Science, Center for Food Safety, University of Arkansas System Division of Agriculture, Fayetteville, AR, USA

Structure & Pathogenesis

Human norovirus (HuNoV), the leading cause of acute gastroenteritis globally, replicates in zebrafish embryo and larvae model. However, due to limited availability of HuNoV positive stool specimens for research, demonstrating replication of Tulane virus (TuV), a surrogate of HuNoV, in zebrafish embryo and larvae model is valuable to study HuNoV infection mechanisms. Three nL of TuV (9 log RNA copies/mL) was microinjected into either fertilized zebrafish eggs (within 4-hours post-fertilization [hpf]) or the yolk of 3-day post-fertilization larvae. Daily, 10 embryos or larvae were pooled into a single sample, with two samples collected per day up to 5 days post-infection (dpi). Viral RNA was extracted and quantified using droplet digital PCR. While TuV replicated in zebrafish embryos, with a 2.5 log increase by 4 dpi, no replication was observed in zebrafish larvae. This may be explained by the developmental regulation of sialylated glycans in zebrafish. Zebrafish embryos express α-2,6-linked sialic acid (SA) residues, which decrease from 6 to 48 hpf, while α-2,3 sialylation increases later. Tulane virus has been shown to specifically bind to α-2,6-linked SA but not to α-2,3-linked SA, potentially explaining the absence of replication in larvae. Ongoing studies aim to validate this hypothesis by microinjecting embryos with Sambucus nigra lectin, which binds α-2,6-linked SA, followed by TuV microinjection to assess whether blocking these residues inhibits viral replication. The findings from this study would help understand the role of glycan expression in viral tropism and demonstrate the utility of the zebrafish model for elucidating HuNoV strain-specific receptor interactions.