Spleen and head kidney differential gene expression patterns in trout infected with Lactococcus garvieae correlate with spleen granulomas

Abstract

Lactococcus garvieae is a significant pathogen in aquaculture with a potential zoonotic risk. To begin to characterize the late immune response of trout to lactococcosis, we selected infected individuals showing clinical signs of lactococcosis. At the time lactococcosis clinical signs appeared, infection by L. garvieae induced a robust inflammatory response in the spleen of rainbow trout, which correlated with abundant granulomatous lesions. The response in kidney goes in parallel with that of spleen, and most of the gene regulations are similar in both organs. A correlation existed between the early inflammatory granulomas in spleen (containing macrophages with internalized L. garvieae ) and up-regulated gene sets, which defined the presence of macrophages and neutrophils. This is the first analysis of the immune transcriptome of rainbow trout following L. garvieae infection during the initiation of adaptive immune mechanisms and shows a transcriptome induction of antibody response by both IgM (+) and IgT (+) spleen B cells to respond to systemic infection. These results increase our understanding of lactococcosis and pave the way for future research to improve control measures of lactococcosis on fish farms. Electronic supplementary material The online version of this article (10.1186/s13567-019-0649-8) contains supplementary material, which is available to authorized users.

Antimicrobial Peptides of Salmonid Fish: From Form to Function

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“…(P erez-Arellano & del Pozo 2013). These bacteria have been subject to further study, identified and used in experimental models to explain the underlying mechanisms in granulomatous processes; however, other bacteria apart of these can be also found in literature as etiological agents of granulomatuos diseases (Table 1); for example, Lactococcus garvieae, which is associated with fatal haemorrhagic septicaemia in farmed rainbow trout (Shahi et al 2018), can also produce spleen granulomas while inducing antibody response by both IgM (+) and IgT (+) spleen B cells (Castro et al 2019).…”