A recombinant 31.5 kDa keratinase and a crude exo‐antigen fromMicrosporum canisfail to protect against a homologous experimental infection in guinea pigs

Abstract

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.

Secreted subtilisin Sub3 from Microsporum canis is required for adherence to but not for invasion of the epidermis

“…35 Each animal was infected with both the control strain on one flank and the SUB3 silenced strain on the other flank in order to avoid the considerable variation in lesion intensity observed among animals, as reported in previous experiments. 13,21,32,33 In addition to Sub3, M. canis can secrete multiple other subtilisins 11 and other keratinolytic metalloproteases of the fungalysin family. 9,10,36 Redundancy in activity of the different keratinolytic proteases is likely.…”

“…We used a guinea pig experimental infection model that has been widely used as a model to study M. canis dermatophytosis. 13,21,32,33 As the SUB3 silenced strain failed to adhere to skin, adherence was artificially promoted using poloxamer 407 as excipient. The thermal gelation of poloxamer 407 in contact with skin allows the formation of a deposit increasing the contact time, which allows bypassing of the adherence step of arthroconidia to skin.…”

Secreted Proteases from Dermatophytes

“…Antibody response was observed towards Mep3, but not towards Sub3 except for one out of fourteen animals. Although being immunogenic, both proteases were not protective against M. canis experimental infection in guinea pigs in a vaccination trial [42,43].…”

Assessment of immunogenicity and protective efficacy of Microsporum canis secreted components coupled to monophosphoryl lipid-A adjuvant in a vaccine study using guinea pigs

“…In cats, several attempts have been made to develop vaccines using characterized antigens from M. canis. The protective efficacy of a crude exo-antigen and two recombinant proteases, the subtilisin rSub3, a fungal endopeptidase involved in adherence of M. canis to human and animal epidermis (Baldo et al, 2010;Bagut et al, 2012), and the metalloprotease rMep3 have been tested in experimentally induced M. canis infections in guinea pig with inconclusive results (Descamps et al, 2003;Vermout et al, 2004). The development of safe and effective vaccines requires the use of both appropriate antigens and adjuvants.…”