Título: ANTI-betanodavirus ACTIVITY OF NATURAL SUBSTANCES OBTAINED FROM BACTERIA AND ALGAE
Resumen: Nervous necrosis virus (NNV) infects a wide range of fish species, causing high mortality rates in cultured fish. A prophylactic practise to enhance the natural resistance of farmed fish to viral infections is the use of functional food. Extracellular products (ECPs) from probiotic bacteria represent a valid and safe strategy for providing beneficial effects against microorganisms in fish. Algae are also sources of substances with potential activity to improve resistance to infections. The objective of this study was to evaluate the antiviral activity of ECPs from the probiotic bacteria Shewanella putrefaciens Pdp11 and Bacillus pumilus UMA169, as well as of extracts and polysaccharides from Ulva rigida against a RGNNV isolate, the most prevalent genotype in Mediterranean outbreaks.
E11 cells were inoculated at 0.05 MOI, and the cellular survival rate was calculated using the MTT reduction assay at 5 days post-infection. The substances tested were: (i) ECPs from B. pumilus UMA169 and S. putrefaciens Pdp11 (both cultured on TSAs at 15 ºC for 48 h) at 50 μg of protein·mL-1, (ii) extracts of U. rigida at 100 and 500 μg·mL-1 and (iii) ulvan polysaccharides from U. rigida at 50 μg·mL-1.
ECPs from B. pumilus UMA169 and Pdp11, exhibited antiviral activity against RGNNV. Actually, both ECPs conferred full protection to the cells. Furthermore, when E11 cells were inoculated with these two ECPs, a higher number of cells was recorded, thus suggesting that these compounds could stimulate cell growth.
Regarding extracts and polysaccharides from U. rigida, a clear protection effect was recorded in cells treated with ulvan polysaccharides, although the protection was lower than the observed with ECPs. In contrast, extracts of U. rigida showed the opposite effect, that is, cellular survival of RGNNV infected cells was lower in the presence of the extract than in control cells.
ECPs and ulvans are promising candidates to be used as protective substances against RGNNV. Actually, their effect on viral replication and infective viral particles production, will also be evaluated. An in vivo assay will also be performed.
Congreso: 22nd International Conference on Diseases of Fish and Shellfish, Heraklion, Grecia
