Serum-specific antibodies in rabbits naturally infected with Trichophyton mentagrophytes.

Abstract

In the present study, we investigated the humoral immune response of rabbits to Trichophyton mentagrophytes (sensu lato) proteins obtained from keratin-rich media in vitro. The test rabbits were naturally infected with T. mentagrophytes. The production of keratinolytic enzymes in T. mentagrophytes was stimulated by growing cultures with keratin as a sole nitrogen source. The proteins were isolated from a protein extract prepared from the fungal mat. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) showed three bands. Bands with Mr 20 and 30 kDa were glycosylated, whereas a band of 18 kDa was not. The rabbits' humoral immune responses to the total protein extract of T. mentagrophytes and to the proteins with keratinolytic activity was studied by immunoblotting. IgG from infected rabbits' sera revealed eight dominant bands with apparent molecular weights between 20 and 75 kDa. Bands of 20, 30 and 33 kDa appeared with a frequency rate of 76% only on immunoblots of infected rabbit serum. Using an indirect enzyme-linked immunosorbent assay (ELISA), we observed a significant increase in specific antibodies in a group of infected rabbits compared to a control group (P < 0.001). The ELISA exhibited 95% sensitivity and 83% specificity at the optimal cut-off value, with 90% predictive values of a positive and a negative result. Under these conditions, it could be used in the accurate detection of specific antibodies in sera of infected rabbits.