[Determination of the antiviral activity of a naturally occurring sulfated xylomannan under various experimental conditions].

The effects of different experimental conditions on the antiviral activity of the sulphated xylomannan F6, isolated from the red seaweed Nothogenia fastigiata, against the replication of herpes simplex virus type 1 and 2 (HSV-1 and HSV-2) were studied. The compound was equally effective against several strains of HSV-1 (F, KOS, B-2006 and Field) and HSV-2 (G) in different cell lines (Vero, HEp-2 and BHK-21). Furthermore, the antiviral activity of F6 was independent of the method employed to determine the 50% inhibitory concentration (IC50) (virus yield or plaque reduction tests). The value of the IC50 against HSV-1 was not significantly affected by the initial virus concentration since a variation in the multiplicity of infection from 0.0001 to 0.1 UFP/cell only increased twofold the IC50 from 0.61 to 1.35 micrograms/ml, respectively. The potent inhibitory effect of F6 against high doses of HSV-1 represents a significant advantage for this sulphated polysaccharide with respect to other compounds only active against low viral inocula.