SDS-PAGE separation of dermatophyte antigens, and western immunoblotting in feline dermatophytosis.

Water-soluble antigens liberated from the disrupted mycelium of nine dermatophytes (seven isolates of Microsporum canis, one each of Microsporum gypseum and Trichophyton mentagrophytes) were compared by analytical slab SDS-PAGE. No substantial differences were observed between the protein bands of the M. Canis isolates, but certain distinctive bands were apparent in the other two species examined. Western immunoblotting using M. canis-derived antigens separated by SDS-PAGE was used to investigate the humoral immune response in 79 cats with naturally-occurring dermatophytosis (72 with M. canis, six with M. gypseum and one with T. mentagrophytes) and this information was compared to results of immunoblots from 46 control (non-dermatophyte exposed) cats. Seven dominant bands (bands which occurred frequently and stained heavily) were identified in immunoblots from the dermatophyte-infected cats with apparent molecular weights varying between 39 and 120 kD. None of these bands were totally specific markers for dermatophytosis as a variable proportion of the control cats showed reactivity to all these proteins. However, most (73%) of the dermatophyte-infected cats showed reactivity to six or seven of the identified bands whereas most (80%) of the control cats showed reactivity to between zero and three of these bands (p < 0.005). Western immunoblotting could be used to select individual immunodominant antigens for further evaluation of protective (cell-mediated) immunity.