Analysis of striped bass (Morone saxatilis) and white bass (M. chrysops) spleenic transcriptome following Streptococcus iniae infection

Authors: Andersen, Linnea; Abernathy, Jason; Farmer, Bradley; Lange, Miles; SANKAPPA, NITHIN - Orise Fellow; McEntire, Matthew; Rawles, Steven

Submitted to: Marine Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2025
Publication Date: 2/17/2025
Citation: Andersen, L.K., Abernathy, J.W., Farmer, B.D. et al. Analysis of Striped Bass (Morone saxatilis) and White Bass (M. chrysops) Splenic Transcriptome Following Streptococcus iniae Infection. Mar Biotechnol 27, 51 (2025).
DOI: https://doi.org/10.1007/s10126-025-10431-2

Interpretive Summary: Streptococcal disease results in major mortality events of both marine and freshwater fishes worldwide. Streptococcus iniae is among the prominent causative bacterial strains as it has been found to cause a higher incidence of mortality and act as a zoonotic pathogen. In this study, we examine the susceptibility of two important aquaculture species in the United States, striped bass (Morone saxatilis) and white bass (Morone chrysops), to S. iniae. A high incidence of mortality was observed in both species, although striped bass succumbed more rapidly than white bass. We then examined the global gene expression changes in the spleen tissue during an active infection. We identified significant differences and similarities in gene expression profiles between the two species in response to S. iniae, especially among known immune responsive genes. These results will be useful in the identification of candidate genes and potential biomarkers associated associated with resistance to S. iniae.

Technical Abstract: Streptococcal disease results in major mortality events of both marine and freshwater fishes worldwide. Streptococcus iniae is among the prominent causative bacterial strains as it has been found to cause a higher incidence of mortality and act as a zoonotic pathogen. Here we examine the susceptibility of two important aquaculture species in the United States, striped bass (Morone saxatilis) and white bass (Morone chrysops), to S. iniae. A high incidence of mortality was observed in both species, although striped bass succumbed more rapidly than white bass. Spleen gene expression at three time points following infection was analyzed to further elucidate the mechanisms underlying these observations. The down-regulation of gene transcripts associated with pathogen detection (tlr1, tlr8, tlr9), antigen processing (cd74a), immune cell recruitment and migration (ccr6b, ccr7), macrophage function (csf1ra), T-cell signaling and NF-kB activation (card11, fyna, tirap) was detected in both species. These findings potentially indicate impairment in these critical early immune system processes such that both species were ultimately highly susceptible to S. iniae infection despite the detected up-regulation of transcripts typically associated with effective immune response, such as cytokines (il1ß, il8, il12b2, il17rc, tnfa) and hepcidins (hamp, hamp2). The presented results collectively identify several candidate genes and associated pathways for further investigation to characterize the vulnerability of striped bass and white bass to S. iniae and that may be considered for selective breeding efforts, biotechnological intervention, and/or exploitation in the development of vaccines and alternative treatments.