ISOLATION, CHARACTERIZATION AND IMMUNOCHEMICAL STUDIES ON FIBROUS PROTEINS FROM COWRY SHELL (CYPRAEA MONETA, LINNAEUS)

BACKGROUND

Biomaterials are non-drug substances used to treat, enhance or replace functions of body tissues or organs. Natural sources of biomaterials have recently become the focus of several research activities. Cowry shell constitutes one of the most promising natural sources of biomaterials because of its chemical stability, biodegradability and biocompatibility in the body. However, its applications may be limited due to immunogenic and toxic responses that may occur following implantation, hence this study.

MATERIALS AND METHODS

Crude fibrous protein extracted with citrate buffer from pulverised cowry shells (Cypraea moneta (L)), was resolved into two components (CSP1 and CSP2) by gel filtration. Immunological studies were performed with antisera obtained from rabbits by double immunodiffusion and immunoelectrophoresis techniques. Mice treated with the proteins were observed for signs of toxicity and their liver, kidney, lungs and spleen were processed histologically.

RESULTS

The native molecular weight of CSP1 and CSP2 determined by gel filtration were 91kDa and 33kDa respectively. CSP1 and CSP2 displayed single bands on SDS-PAGE with subunit molecular weight values of 19kDa and 19.5kDa respectively. Antisera obtained from rabbits immunised with the crude citrate buffer extracts precipitated the antigen in double immunodiffusion tests. Histopathological examinations revealed a dose-dependent damaging effect of the shell proteins on liver, kidney, lung and spleen tissues of the treated mice.

CONCLUSION

This study showed that cowry shells contain fibrous proteins which are immunogenic and toxic in mice at relatively high concentrations, causing visible organ damage without concurrent physical manifestations.

Antibody to gp39, the ligand for CD40 significantly inhibits the humoral response from Graves' thyroid tissues xenografted into severe combined immunodeficient (SCID) mice

Experimental evidence suggests that interference with gp39-CD40 interactions may have therapeutic potential in prevention of certain autoimmune disorders (i.e., collagen-induced rheumatoid arthritis). The binding between CD40 expressed on mature B cells and CD40 ligand (CD40L, gp39) transiently expressed on activated T helper cells (Th) further stabilizes the interactions (between Th and B cells) and co-ordinates the responses of the interacting cells during antigen presentation, and is essential for thymus-dependent humoral immunity. Graves' disease is the most common form of hyperthyroidism, in which hyperactivity of the thyroid gland is due to an autoantibody directed against the thyrotropin receptor (TSHR). The main objective of our study was to determine the role of interactions between gp39 and CD40 in "an established" human Graves' disease (GD). Severe combined immunodeficient (SCID) mouse served as a vehicle for human Graves' thyroid tissue. This experimental setting allows us to study, observe, and immunomodulate human autoimmune tissue in so called in vivo condition. We studied the effects of ip administration of anti-gp39 mAb on humoral response, thyroid function tests, expression of adhesion molecules, and HLA-DR on human thyrocytes and histopathological changes from human GD thyroid tissue xenografts. GD thyroid tissue from 4 patients was xenografted into 20 SCID mice (0.8 g/mouse). Human immunoglobulin G (IgG) levels became detectable in SCID mice 1 week after xenograftment. Ten SCID mice were sequentially administered anti-gp39 mAb (250 micrograms/mouse/ dose) ip every 4 days until the end of the experiment. Ten control animals were injected with vehicle (PBS) in similar fashion. Blood samples were taken every 2 weeks from the tail veins for measurement of the humoral response [human IgG, thyroid-stimulating antibody (TSAb), antithyroperoxidase (anti-TPO), and antithyroglobulin (anti-Tg), Abs], and thyroid function tests. After 8 weeks, animals were sacrificed and thyroid tissue was examined histologically. The humoral response from the intrathyroidal lymphocytes was measured and the tissue morphology of GD was preserved during the 8-week period in phosphate-buffered saline (PBS)-treated SCID mice xenografted with GD xenografts. However, administration of anti-gp39 mAb completely blocked or significantly decreased the humoral response in all treated animals. On the other hand, no significant histological changes were associated with the administration of anti-gp39 mAb. The degree of lymphocytic infiltration in thyroid tissue xenografts was comparable in both groups. Serum thyroxine values were normal in both groups. In spite of a profound immunosuppressive effect on the humoral response by directly blocking CD40-gp39 interactions in vivo, this did not result in complete deletion of the responding Th in the thyroid specimens.