Live imaging of largemouth bass virus dissemination in zebrafish

Introduction Understanding how viruses infect and spread within a living host is an attractive yet formidable goal. However, our understanding of these processes relies primarily on in vitro imaging studies conducted in cell culture models. Methods Here, we developed a zebrafish model of Largemouth bass virus (LMBV) infection, enabling for the first time real-time tracing of iridovirus spread in vivo . Results LMBV infected zebrafish exhibited typical histopathological changes and reduced locomotor activity, culminating in 86.7% mortality. In representative live-imaging time-lapse sequences, LMBV (fluorescent puncta) first appeared in the tail-fin region and then propagated to the eye region. Concurrently, reporter-positive neutrophils and macrophages exhibited directed migration toward sites of viral fluorescence following exposure to fluorescently labeled LMBV. Subsequently, macrophages were observed moving toward regions containing fluorescent puncta, with some fluorescent puncta spatially overlapping with macrophage-associated fluorescence. In addition, fluorescent puncta was detected in the embryo region following viral exposure, and the fluorescence signal increased with exposure duration and viral dose. Discussion Our findings have enabled direct visualization of LMBV’s infection route in vivo , offering a real-time perspective on the viral infection process in teleosts.