Detection of circulating antibodies to purified keratinolytic proteinase in sera from guinea pigs infected with Microsporum canis by enzyme-linked immunosorbent assay

Remarkable Phenotypic Virulence Factors of Microsporum canis and Their Associated Genes: A Systematic Review

Microsporum canis is a widely distributed dermatophyte, which is among the main etiological agents of dermatophytosis in humans and domestic animals. This fungus invades, colonizes and nourishes itself on the keratinized tissues of the host through various virulence factors. This review will bring together the known information about the mechanisms, enzymes and their associated genes relevant to the pathogenesis processes of the fungus and will provide an overview of those virulence factors that should be better studied to establish effective methods of prevention and control of the disease. Public databases using the MeSH terms "Microsporum canis", "virulence factors" and each individual virulence factor were reviewed to enlist a series of articles, from where only original works in English and Spanish that included relevant information on the subject were selected. Out of the 147 articles obtained in the review, 46 were selected that reported virulence factors for M. canis in a period between 1988 and 2023. The rest of the articles were discarded because they did not contain information on the topic (67), some were written in different languages (3), and others were repeated in two or more databases (24) or were not original articles (7). The main virulence factors in M. canis are keratinases, fungilisins and subtilisins. However, less commonly reported are biofilms or dipeptidylpeptidases, among others, which have been little researched because they vary in expression or activity between strains and are not considered essential for the infection and survival of the fungus. Although it is known that they are truly involved in resistance, infection and metabolism, we recognize that their study could strengthen the knowledge of the pathogenesis of M. canis with the aim of achieving effective treatments, as well as the prevention and control of infection.

Humoral immune response against soluble and fractionate antigens in experimental sporotrichosis

Sporotrichosis is a chronic granulomatous mycosis caused by the dimorphic fungus Sporothrix schenckii, which is widely distributed in nature, and presents a saprophytic mycelial form on plant debris and soil. The immunological mechanisms involved in the prevention and control of sporotrichosis are not yet fully understood. In this study, mice were studied after infection with Sporothrix schenckii. In the first week after infection, fungal loading increased and thence decreased drastically 14 days after infection. Analysis by immunoblotting showed that the sera of all mice tested had antibodies reacting only with a 70 kDa antigen, with predominance of IgG1 and IgG3. Taken together, our results show that antigens from S. schenckii induced a specific humoral response in infected mice.

Production of extracellular enzymes by Microsporum canis and their role in its virulence

Microsporum canis is the most prevalent dermatophyte of domestic animals. Several enzymes produced by dermatophytes, particularly keratinases, are considered to play a role in the virulence of this fungus. To investigate the possible relationship between the clinical status of M. canis infection and enzymatic activity of isolates, we studied the relationship between keratinase, elastase, lipase and DNase levels produced in vitro by different isolates and virulence as expressed in a guinea pig model. Samples isolated from symptomatic dogs and cats showed a statistically significantly (P < 0.05) higher keratinase activity than samples isolated from asymptomatic animals. Experimental infection of guinea pigs showed that a strain with high in vitro keratinase activity induced acute infection, which resolved clinically and mycologically faster than the infection induced by a strain with low keratinase activity. This suggested a strong correlation between high keratinase activity and the development of symptoms. The same correlation was not observed for other enzymes tested.

Expression of PZ-peptidases by cultures of several pathogenic fungi. Purification and characterization of a collagenase from Trichophyton schoenleinii

Peptidolytic activity was studied in the broken-cell extracts of 17 isolates of pathogenic fungi tested with phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-Arg (PZ-PLGPA) as a substrate. All the fungi studied except Candida spp., Cryptococcus neoformans and two actinomycetes hydrolyzed the substrate and therefore contained a so-called PZ-peptidase activity. Of all the positive strains, Trichophyton schoenleinii, a pathogenic fungus showed the highest activity and was therefore chosen as a source for PZ-peptidase purification. The four chromatographic steps, a 'negative' dye column, a 'positive' dye column, hydroxyapatite Ultrogel, and modified TSK (HW 55), gave a highly purified peptidase with a 12% overall yield. Inhibitor studies suggested that the 82 000 M(r) PZ-peptidase is a metalloproteinase. Moreover it cleaved native rat type I collagen. Partial peptide sequencing showed a strong sequence homology to regions of two metalloproteinases previously identified in the yeast Saccharomyces cerevisiae and in rat.

Enzyme patterns of dermatophytes

Exoenzymes produced by common dermatophytes, in addition to their ability to cause cutaneous inflammation, are thought to contribute to fungal spread. To investigate the patterns of enzymes released by common dermatophytes as well as Scopulariopsis brevicaulis, the fungi were grown in liquid media containing either hair, stratum corneum, neopeptone or lipids, or in RPMI medium. Enzymes recovered from the culture supernatants were compared using the Api-zyme test. As a result, the widest range of enzymes was seen in protein-containing media, with a maximum of 13 enzymes stimulated by growth on hair. Dermatophytes in all protein media produced high levels of alkaline phosphatase, esterases and leucine arylamidase. In these media the highest total enzymatic activity was released by Microsporum canis, whereas the lowest was released by Epidermophyton floccosum. Although RPMI broth stimulated luxuriant growth of all species, recovery was limited to a maximum of six enzymes. In lipid medium E. floccosum and M. canis failed to grow. When comparing the various nutrients, Scopulariopsis released fewer enzymes than the dermatophytes and only minor quantities of alkaline phosphatase. We conclude that alkaline phosphatase, esterases and leucine arylamidase may be important for the parasitic growth of dermatophytes. The total enzymatic activity of dermatophytes appears to be correlated with the intensity of cutaneous inflammation. Furthermore, enzyme measurements may be helpful for species identification.

Detection of keratinolytic proteinase in skin tissues from guinea pigs infected with Microsporum canis by an immunoperoxidase technique

An immunoperoxidase technique was performed to detect keratinolytic proteinase (KPase) in sections of the skin taken from guinea pigs infected with Microsporum canis and in cultured M. canis using polyclonal antisera to purified KPase. Of tissue samples from guinea pigs infected with M. canis, all sections of erythematous lesions showed positive staining mainly in the horny layer and the hair follicles. Positive depositions were seen only at the level of the outer and inner root sheaths of the hair follicles in sections of skin lesions showing scales and crusts. However, sections from areas of alopecia following desquamation of the crust showed no depositions of bright red reaction products. The patterns of deposition of KPase according to the clinical course of experimental dermatophytosis were consistent with the existence of organisms observed by PAS and methenamine silver stains. These results suggest that KPase may be produced during infection with M. canis after the development of erythema and before desquamation of the crust.

Immunoblot analysis of antibody responses to Sporothrix schenckii

The serologic response to Sporothrix schenckii was investigated in patients with sporotrichosis by solid-phase enzyme-linked immunosorbent assays (ELISAs) and Western immunoblot techniques. A soluble antigen preparation derived from an S. schenckii isolate contained 15 protein staining components ranging in molecular size from 22 to 70 kilodaltons (kDa) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Sera from 40 patients with sporotrichosis demonstrated Sporothrix immunoglobulin G antibody by ELISA with titers between 128 and 65,200. No sera from 300 healthy individuals or 100 patients with various systemic mycoses other than sporotrichosis had ELISA titers greater than 64. By Western immunoblotting of the antigens separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, sera from 10 patients with cutaneous sporotrichosis reacted with 8 to 10 antigen components (range, 40 to 70 kDa), while sera from 15 patients with extracutaneous sporotrichosis reacted with a greater number of antigen components (15 to 20 bands) over a wider range of molecular sizes (22 to 70 kDa). Antibody to 40- and 70-kDa antigen components was detected by immunoblots in all sera tested from patients with sporotrichosis. Antibody to 22- to 36-kDa antigen components was present in sera from 13 of 15 patients with extracutaneous sporotrichosis, but these lower-molecular-weight components were not detected by sera from patients with cutaneous sporotrichosis. Antibody to these components was not detected by Western blotting in sera from 19 of 20 patients with other fungal diseases or from 30 healthy individuals. Purification of these specific antigen fractions could provide the basis of a sensitive and specific serodiagnostic test to indicate the presence and activity of extracutaneous sporotrichosis.