Humoral and cellular immune response to a crude exo-antigen and purified keratinase of Microsporum canis in experimentally infected guinea pigs

Abstract

In order to understand better the host–parasite relationship and to compare with previous observations in Microsporum canis naturally infected cats, the humoral and cellular immune responses to both a crude exo‐antigen and a 31·5 kDa purified keratinase were evaluated in 12 M. canis experimentally infected guinea pigs. Humoral and cellular responses were assessed by ELISA from days 0 to 56 postinfection (PI) and by measurement of delayed‐type hypersensitivity (DTH) responses on days 14 and 57 PI, respectively. Additionally, immunohistochemical staining was performed and demonstrated that the keratinase was produced in infected guinea pig skin, as previously reported in cats. Despite a marked interindividual variation, all the guinea pigs produced specific IgG to the crude exo‐antigen from day 21 PI onwards, but no anti‐keratinase IgG was detected. Strongly positive DTH responses to the exo‐antigen were observed on both dates, whereas the keratinase elicited no and weak DTH on days 14 and 57 PI, respectively. These results are in agreement with those previously described for naturally infected cats, and indicate that the 31·5 kDa keratinase is not a major antigen in M. canis infection.

Secreted dipeptidyl peptidases as potential virulence factors forMicrosporum canis

“…Skin tests were performed 30 days after experimental infection, on 12 infected and three noninfected guinea‐pigs. Tested antigens were DppV (4 μg per site) and a crude M. canis exoantigen (10 μg per site) shown previously to elicit DTH skin responses in guinea‐pigs following M. canis infection (Mignon et al , 1999). Both antigens were heat‐inactivated and injected intradermally in 100 μL of 50 μM ammonium bicarbonate.…”

Assessment of the cutaneous immune response duringArthroderma benhamiaeandA. vanbreuseghemiiinfection using an experimental mouse model

“…Therefore, the establishment of an animal model of dermatophytosis is required. Currently, the most frequently used animal model is the guinea pig but the inbred nature, and the genetic and immunological tools available in the mouse species, support the use of a model in the study of immune response against dermatophytes . Only a few mouse models of dermatophytoses are available.…”

Use of western blot to study Microsporum canis antigenic proteins in canine dermatophytosis

“…Past ELISA studies indicate that, in both dogs 12 and cats, 13,20 serology can detect either active or prior dermatophyte infection because high antibody levels can persist for variable periods beyond clinical and mycological recovery. The elimination of fungal infection normally results from the development of a cellular immune response and is not tied to the Ig trend 12–14,19–21 . Given these considerations, serological positivity (ELISA or WB) should be interpreted with caution in animals with a history of either confirmed or suspected dermatophytosis, as well as in animals with no available clinical history.…”

“…An analogous immune response may be presumed in cats as subjects recovered from dermatophytosis have been shown to have larger DTH reactions to M. canis antigenic extracts than unexposed cats and cats with active infection 30 . Concerning M. canis , a 31.5 kD keratinolytic serine protease (Sub3) and 43.5 kD keratinolytic metalloprotease (Mep3) have been shown to be important fungal virulence factors involved in disease pathogenesis in cats and guinea pigs, particularly invasion of the hair and stratum corneum, adherence to corneocytes and induction of the humoral and cellular immune responses 13,21,31–34 . Because such antigens have been shown to elicit strong in vitro and in vivo cellular immune responses, they represent good candidates for vaccine trials.…”

“…In this study, antigen was prepared by mechanical disruption of the fungal mycelium, which was also the procedure performed in the previous study of cats 15 . Most of the above‐cited, virulence‐associated, factors have been shown to be secreted both in vitro and in vivo in the microenvironment 13,21,31–34 . Because we did not use culture filtrates for antigenic preparation, we cannot know if some or all the proteins that we described were also secreted.…”