Antioxidant capacity, non-specific immunity, histopathological analysis and immune-related genes expression in Nile tilapia Oreochromis niloticus infected with Aeromonas schubertii

Abstract Aeromonas schubertii is a conditional pathogen widely distributed in aquatic environments, yet it was only recently reported as a causative pathogen in fish. This study investigated antioxidant capacity, non-specific immunity, histopathology and immune-related gene expression profiles in Nile tilapia Oreochromis niloticus injected with A. schubertii. The results show that A. schubertii infection stimulated the activation of antioxidant activity and non-specific immunity in Nile tilapia. Histopathological analysis revealed that inflammation existed in the liver, spleen, head kidney, brain and intestine of the infected fish. Quantitative real-time PCR was performed to measure mRNA expression levels of six immune-related genes (interleukin-1β, tumor necrosis factor-α, cyclooxygenase-2, transforming growth factor beta, interleukin-10 and heat shock protein 70) in the intestine and head kidney at different timepoints after experimental infection. The results demonstrated clear transcriptional activation of these immune-related genes in the intestine and head-kidney tissues. To our knowledge, this is the first study to investigate the host response to A. schubertii infection in a fish. These results will contribute to further understanding of the pathogenesis and host defense system in fishes following infection with A. schubertii.