Spatiotemporal Dynamics of Acute Phase Response Related Molecules in Micropterus salmoides During Streptococcus Agalactiae Infection

Acute phase response related molecules are a class of proteins whose concentration changes rapidly and significantly in response to abnormal conditions such as injury, infection, and inflammation. The levels of acute phase response related molecules can reflect abnormalities in the body, but related studies in teleost fish are still relatively limited. In this study, Cp, Hap, Hep, Hx, IL-1β, and IL-6 of largemouth bass (Micropterus salmoides) were identified, the spatiotemporal dynamics of these six acute phase response related molecules in blood, liver, spleen, and brain tissues of largemouth bass before and after infection with Streptococcus agalactiae were analyzed, and they were compared and analyzed for their potential use as indicators to detect S. agalactiae infection. The results showed that in healthy largemouth bass, the distribution of acute phase response related molecules (except IL-6) was highest in the liver. All the examined genes exhibited significant changes in their transcription levels across the tested tissues after infection. Furthermore, most genes exhibit higher expression levels in the spleen compared with other tissues. Hep and IL-1β genes in spleen tissue and Hx and IL-6 in brain tissue showed significant increase from 0 to 72 h post infection (hpi) compared with the control group. Among these, IL-1β is the only acute phase response related molecule whose expression levels were more than 150-fold, reaching 165-fold to 270-fold from 6 to 24 h post infection in the spleen. This study explores the temporal correlation between several acute phase response related molecules and streptococcal infection in largemouth bass, providing insights and references for subsequent research on early infection response proteins.