Immunomodulating effect of (1→3, 1→4) β-glucan, derived from oats, in mice infected with eimeria vermiformis
Yun, Cheol Heui
Coccidiosis, caused mainly by Eimeria spp., is controlled primarily by chemotherapy. Emergence of drug resistance increases the need to develop vaccines and immunostimulants to control this disease. Beta-glucan (1→3, 1→6) from yeast and fungi non-specifically enhances host resistance to bacterial, viral, protozoan and fungal infections. β-glucan (1→3, 1→4) is present in oats and its immunostimulating properties are unclear. In experiment I oat β-glucan, in a dose and time dependent manner, stimulated release of IL-1 and, to a much lesser degree, TNF-α from murine macrophages in vitro and induced release of IL-2, IL4 and IFN-γ from cultured murine primary spleen cells. Injection of oat glucan (500 μg/0.2 ml) ip in CD-1 mice increased (P<0.01) the number of macrophages in peritoneal fluid. Survival of CD-1 mice challenged with Staphylococcus aureus was improved (P<0.05) by oat β-glucan ip 3 days pre-challenge. In experiment II oat glucan treatment sc (500 μg/0.1 ml) or ig (3 mg/0.3 ml) daily for 10 days in C57BL/6 mice immunosuppressed with dexamethasone (100 μg/d) and infected with E. vermiformis reduced fecal oocyst excretion by 23 and 34%, respectively. Oat β-glucan ip or ig reduced (P<0.001) mortality in infected, immunosuppressed mice. Oat β-glucan treatments generally increased total antibody concentrations, and anti-sporozoite and anti-merozoite IgG (P<0.05). In experiment III a single dose of oat β-glucan sc given on days -2, 0 or 2, but not 6, relative to infection with E. vermiformis on day 0, reduced (P<0.05) oocyst shedding in C57BL/6 mice. Proliferative responses of spleen cells to sporozoite antigen were increased (P<0.05) in mice treated on days -2 and 0. Oat β-glucan increased (P<0.01) the percentage of CD4⁺ T cells in MLN on day 12, and reduced the percentage of CD8⁺ cells in spleen on day 19. In conclusion, oat β-glucan showed immunostimulatory properties through enhancement of non-specific and specific humoral and cellular immune responses. Oat β-glucan treatment enhanced resistance to E. vermiformis infection in mice. These findings suggest that oat β-glucan has potential for use in livestock as an immunostimulant and for the prevention and treatment of coccidiosis.