The fungal cell wall component b-1,3-glucan has an adjuvant effect on the allergic response to ovalbumin in mice

Abstract

The polyglucose b -1,3-D-glucan is a major structural component of the cell wall of yeasts and fungi. In the present study, the adjuvant activity of b-1,3-glucan from the fungus Sclerotinia sclerotiorum (SSG) on the response to the model allergen ovalbumin (OA) was studied, using the popliteal lymph node assay (PLNA) in BALB/c mice. The adjuvant activity on the local cellular response was determined by measuring the weight, cell number, and proliferation of the extracted PLNs. The levels of OA-specific immunoglobulin (Ig)E, IgG1, and IgG2a in serum were measured by enzyme-linked immunosorbent assay (ELISA). Groups of 8 mice were given either SSG + OA, SSG alone, or OA alone on d 0. Thereafter they were exsanguinated on d 20, or reinjected with OA on d 21, before exsanguination on d 26 or 33. Only on d 26 was SSG + OA found to significantly increase the PLN weight and cell numbers, but not cell proliferation (thymidine incorporation), compared with OA or SSG alone. SSG + OA was also found to significantly increase both the anti-OA IgE and IgG1 levels on d 20, 26, and 33 compared to OA alone. Compared to SSG alone, SSG + OA increased the OA-specific IgE and IgG1 levels significantly on d 26 and 33, but not on d 20. A similar increase was not found for IgG2a. Our results show that b -1,3-D-glucan provides a clear Th2-dependent (allergic) immune response to OA, indicated by elevated levels of IgE and IgG1 and not IgG2a, in the mouse model used.