The Immune Response toMicrosporum canisInduced by a Fungal Cell Wall Vaccine*

Abstract—An experimental infection model was used to assess induction of specific immunity againstMicrosporum canisin cats with anM. caniscell wall vaccine preparation. Kittens 8–9 weeks old (n= 12) received five doses of either vaccine or placebo at biweekly intervals. Specific immunity was monitored via plasma anti‐dermatophyte antibody titers and lymphocyte blastogenesis (LB) to dermatophyte antigens. After vaccination, cats were challenged with viableM. canisspores, and lesion development was monitored. Vaccinated cats developed higher anti‐dermatophyte IgG, but not IgM, titers than controls, beginning after the second dose of vaccine (P< 0.001). During the vaccination period, specific cellular immunity as measured by LB was absent in control cats, but developed to a limited degree in vaccinated cats (P< 0.05). After challenge with 105fungal spores per cat, both control and vaccinated cats developed active infections. The vaccine appeared to induce an antibody titer quantitatively similar to that produced by infection, but less measured cellular immunity than was seen with infection and recovery. These results suggest that induction of high titers of serum IgG or IgM antibody againstMicrosporum canisis not protective against challenge exposure.