A recombinant 31.5 kDa keratinase and a crude exo-antigen from Microsporum canis fail to protect against a homologous experimental infection in guinea pigs

A Microsporum canis recombinant 31.5 kDa keratinase and a M. canis crude exo-antigen were tested as vaccines in an experimental infection model in guinea pigs. Animals were vaccinated subcutaneously three times at two-week intervals with either the keratinase, the exo-antigen or the adjuvant alone. Cutaneous challenge was performed blindly. Both humoral and cellular-specific immune responses to M. canis antigens were evaluated every 14 days, while a blind evaluation of clinical lesion development and fungal persistency in skin were monitored weekly. Vaccination induced very high and significant (P < 0.01) antibody responses towards both antigens. High cell-mediated immune responses to both immunogens were also induced by vaccination. After challenge, however, scores reflecting the severity of dermatophytic lesions did not differ significantly between vaccinated and control groups at any time after challenge. These results suggest that, in the guinea pig, the induction of specific immune responses against the M. canis-secreted antigens used in this study are not protective against challenge exposure.