FC-6 Four isoforms of exfoliative toxin produced by Staphylococcus hyicus abolished immunofluorescence for desmoglein 1 in pig skin

Western immunoblotting studies of canine sera using Malassezia pachydermatis extracts have shown that infected dogs commonly have antibodies that recognize multiple antigens. However, reported patterns of immunoreactivity vary between different laboratories. Since culture duration influences the antigenic composition of lipid-dependent Malassezia when probed with human sera, we investigated whether the in vitro growth phase of M. pachydermatis influences immunoreactivity to canine sera. Extracts of M. pachydermatis CBS1879 grown in Sabouraud's liquid medium at 37°C for 2, 4, 6, 8 and 10 days were prepared by mechanical disruption, centrifugation, dialysis and lyophilization. Yeast growth phase was assessed by sequential colony counts and optical density measurements. Patterns of IgG immunoreactivity in high ( n  = 3) and low ( n  = 3) titre sera were compared using extracts prepared at each time point by SDS-PAGE and western immunoblotting. Protein bands of 62 and 49 kDa were recognized by all sera, and five sera recognized 98 and 68 kDa bands. Proteins of 188, 66, 58, 57, 38, 28 and 17 kDa were only recognized by high titre sera. All high titre sera recognized more bands in exponential phase (day 2) extracts when compared with decline phase (days 8–10) extracts, and two of these sera showed most bands in stationary phase (days 4–6) extracts. Bands of 62 and 57 kDa were primarily detected in exponential and early stationary phase extracts. Antigenic variation in extracts of M. pachydermatis prepared during different growth phases might explain discrepancies between previous laboratory studies of immunity to this yeast.
Funding: Government of Malaysia.