In vitro and in vivo immunomodulatory activity of sulfated polysaccharides from red seaweed Nemalion helminthoides.

Water-soluble sulfated polysaccharides from the red seaweed Nemalion helminthoides: two xylomannan fractions (N3 and N4) and a mannan fraction (N6) were investigated to determine their in vitro and in vivo immunomodulatory activities. N3 and N4 induced in vitro proliferation of macrophages of the murine cell line RAW 264.7 and significantly stimulated the production of nitric oxide (NO) and cytokines (IL-6 and TNF-α) in the same cells, whereas this response was not observed with the mannan N6. The cytokine production was also stimulated by sulfated xylomannans in vivo in BALB/c mice inoculated intravenously with these polysaccharides. Remarkably, when mice were treated with N3 and N4 for 1 h before being infected with Herpes simplex virus type 2, they remained asymptomatic with no signs of disease. The in vitro and in vivo results suggest that sulfated xylomannans could be strong immunomodulators.