Differences in inflammatory responses of rainbow trout infected by two genotypes of the myxozoan parasite Ceratonova shasta

Dev Comp Immunol. 2021 Jan;114:103829. doi: 10.1016/j.dci.2020.103829. Epub 2020 Aug 23.

Abstract

Two genotypes of the intestinal parasite Ceratonova shasta infect Oncorhynchus mykiss: genotype 0 results in a chronic infection with low mortality while genotype IIR causes disease with high mortality. We determined parasite load and the relative expression of six immune factors (IgT, IgM, IL-6, IL-8, IL-10, IFNG) in fish infected with either genotype over 29 days post-exposure. In genotype IIR infections the host responded with upregulation of inflammatory and regulatory cytokines. In contrast, genotype 0 infection did not elicit an inflammatory response and expression of IFNG and IL-10 was lower. Antibody expression was upregulated in both infections but appeared to have limited efficacy in the virulent genotype IIR infections. Histologically, in genotype 0 infections the parasite migrated through the tissue layers causing inflammation but minimal damage to the mucosal epithelium, which contrasts with the severe pathology found in genotype IIR infections.

Keywords: Cytokine; Fish disease; Immunoglobulin; Intestine; Salmonid.