Antiviral effect of red microalgal polysaccharides on Herpes simplex and Varicella zoster viruses

The cell-wall sulphated polysaccharide of the red microalga Porphyridium sp . has impressive antiviral activity against Herpes simplex viruses types 1 and 2 (HSV 1, 2) and Varicella zoster virus (VZV). Treatment of cells with 1 mug mL(-1) polysaccharide resulted in 50% inhibition of HSV-infection as measured by the plaque assay. Inhibition of the production of new virus par ticles was also shown when pre-infected cell cultures were treated with the polysaccharide. In addition, there was indirect evidence for a strong inte raction between the polysaccharide and HSV and a weak interaction with the cell surface. Depending on the concentration, the polysaccharide completely inhibited or slowed down the development of the cytopathic effect in HSV o r VZV preinfected cells, but did not show any cytotoxic effects on Vero cel ls even when a concentration as high as 250 mug mL(-1) was used. It seems t herefore that the polysaccharide is able to inhibit viral infection by prev enting adsorption of virus into the host cells and/or by inhibiting the pro duction of new viral particles inside the host cells. Thus, this alga seems to be a good candidate for the development of an antiviral drug.