Anti-nodavirus potential activity of R.A73 Enterococcus faecium strain, isolated from Tunisian freshwater fish mucus

Abstract

R.A73 Enterococcus faecium (HG937697) was tested for investigating anti-nodaviral activity and immunomodulatory properties on E-11 fish cells. Non R.A73-related toxicity was confirmed. Likewise, in-vitro inhibition of nodavirus replication and gene expression of nodavirus capsid protein gene in addition to CCR3, IL-10 and TNFα genes were evaluated using qPCR. A preventive treatment of E-11 cells by the bacterial suspension generated a remarkable reduction in virus loads (RQ values from 0.1 to 0.9) at day 7. Interestingly, R.A73 E. faecium showed a significant gene expression upregulation of proinflammatory IL-10 cytokine whereas it did not significantly enhance CCR3 nor TNF-α immune gene expression in E-11 cells. Therefore, add-on its probiotic potential, R.A73 E. faecium is able to stimulate the immune system in the preventive phase throughout the differential expression of main inflammatory genes. This study provides the first evidence that R.A73 E. faecium strain can prevents effectively nodavirus replication, in vitro.