RNA silencing in the dermatophyteMicrosporum canis

Dermatomycoses caused by Microsporum canis are frequent in domestic animals and easily transmissible to humans. Several proteases secreted by this fungus were identified as potential virulence factors, but the construction of deficient strains is required to investigate their role in the pathogenesis of the disease. Using target genes encoding two of these proteases, a first evaluation of the utility of RNA-mediated silencing as a reverse genetic tool in dermatophytes was carried out. SUB3 and DPPIV, respectively coding for a subtilisin and a dipeptidyl peptidase, were both down-regulated, by means of two plasmid constructs designed to express an RNA hairpin that corresponds to part of their respective sequence. The degree of attenuation was evaluated by enzymatic assay of the transformants culture supernatants, and by real-time reverse transcriptase-polymerase chain reaction. Enzymatic activities and expression levels varied from less than 5% to 100% of that of control transformants obtained with plasmid without hairpin inserts. Inhibition was globally more efficient for SUB3 than for DPPIV. These results show that RNA silencing can be used for functional genomics in M. canis, and particularly to circumvent the limits and technical difficulties of conventional disruption methods.

Actividad proteolítica extracelular y análisis molecular de cepas de Microsporum canis aisladas de gatos con y sin sintomatología

Microsporum canis is the main zoophylic dermatophyte in dogs and cats, and it is also an important zoonotic agent. The literature showed that cats are asymptomatic carriers of M. canis. This is apparently due to host resistance and/or the presence of strains with lower virulence. This study was aimed to evaluate the keratinolytic, elastinolytic and collagenolytic activities of M. canis strains and their relationship with symptomatic and asymptomatic cats. In addition, these strains were analysed by RFLP. The strains isolated from cats with clinical dermatophytosis had higher keratinase and elastase activity than those isolated from asymptomatic animals (p minus than 0.05). There were not differences in RFLP patterns based on Hind III digestion.

[A study of the growth and enzymatic activity of Microsporum gypseum and Trichophyton ajelloi isolates from sewage sludge]

The study was to compare growth and enzymatic activity of Microsporum gypseum and Trichophyton ajelloi isolates from sewage sludge. Agar media and the API-ZYM test were used. The isolates showed weak gelatinase, catalase and urease activities and did not produce cellulase, pectate lyase and polygalacturonase. In some strains poor amylase and DNA-se activities were observed. No strain was able to hydrolyze casein. The strains were found to hydrolyze tributyrin, rapeseed oil and Biodiesel oil and to grow on Diesel oil medium. On the medium containing tributyrin and on the media with rapeseed oil and Biodiesel oil additions, inhibition and stimulation of fungal growth was observed, respectively. Diesel oil did not affect the growth of these fungi. The growth and enzymatic activity of M. gypseum was found to be better than the growth and activity of T. ajelloi. Higher enzymatic activity can be associated with the pathogenicity of M. gypseum.

In vitro antifungal and anti-elastase activity of some aliphatic aldehydes from Olea europaea L. fruit

Olea europaea preparations are traditionally employed in a variety of troubles, including skin infections. Olive extracts and some of their pure compounds have shown antimicrobial activity in vitro. The present study deals with the antifungal activity of some aliphatic aldehydes from olive fruit [hexanal, nonanal, (E)-2-hexenal, (E)-2-heptenal, (E)-2-octenal, (E)-2-nonenal] against Tricophyton mentagrophytes (6 strains), Microsporum canis (1 strains) and Candida spp. (7 strains). The capability of these substances to inhibit elastase, a virulence factor essential for the dermatophytes colonization, and their cytotoxicity on cultures of reconstructed human epidermis, are also described. Aldehydes tested, inhibited the growth of T. mentagrophytes and M. canis in the range of concentration between <1.9 and 125 microg/ml; the unsaturated aldehydes showed the most broad spectrum of activity in that inhibited all strains tested. None of the aldehydes exhibited activity against Candida spp. strains. (E)-2-octenal and (E)-2-nonenal inhibited the elastase activity in a concentration-dependent manner; the anti-elastase activity suggests an additional target of the antimicrobial activity of these compounds. Aldehydes were devoid of cytotoxicity on cultures of human reconstructed epidermis. The antifungal activity of the aldehydes from olive fruit here reported, substantiates the use of olive and olive oil in skin diseases and suggests that these natural compounds could be useful agents in the topical treatment of fungal cutaneous infections.

[Enzyme activities of dermatophytes isolated from different clinical samples by ApiZYM method]

Dermatophytes' enzymes may have a role in chronic superficial infections. In this study it was planned to investigate the possible relationship between the enzymatic activities of the dermatophytes and acute or chronic course of the infections. Dermatophytes were isolated from 58 (72%) out of 81 patients with superficial infections. The infections were divided into two groups as acute (< or = 6 weeks) or chronic (> 6 weeks). Isolated fungi were identified by the classical methods and ApiZYM method. ApiZYM exhibits 19 different enzymatic activities. From 11 acute cases; five Epidermophyton floccosum, three Trichophyton rubrum, two Microsporum canis and one Trichophyton mentagrophytes strains were isolated. Of the 47 chronic cases, 96% was due to T. rubrum and 4% due to T. mentagrophytes. Production of alkaline phosphatase, leucine arylamidase and beta-glucosidase enzymes were detected in all tested strains. There was no difference between the enzymatic activities of acute and chronic cases. Alpha-mannosidase activity was detected in all of the species isolated from acute cases whereas none of the chronic cases were positive (P < 0.001). The results of this study suggest that alpha-mannosidase activity may play a role in both cutaneous inflammatory response caused by dermatophytes and the chronicity of the lesions.

Evaluation of immunogenicity and protective efficacy of a Microsporum canis metalloprotease subunit vaccine in guinea pigs

In order to identify protective immunogens against Microsporum canis infection, a purified recombinant keratinolytic metalloprotease (r-MEP3) was tested as a subunit vaccine in experimentally infected guinea pigs. Both humoral and cellular specific immune responses developing towards r-MEP3 were evaluated, by enzyme-linked immunosorbent assay and by in vitro lymphocyte transformation tests respectively. Vaccination induced a strong antibody response, and a significant but transient lymphoproliferative response against the protein. However, the protocol failed to prevent fungal invasion or development of dermatophytic lesions. These results show that under the present experimental conditions, r-MEP3 specific antibodies are not protective against a challenge exposure. They also suggest that in the same model, the induction of cell-mediated immunity towards r-MEP3 is not sufficient, indicating the need for further research in the field of specific immune mechanisms involved in M. canis dermatophytosis.

Isolation of a promoter region of a secreted metalloprotease gene from Microsporum canis

MEP3 of Microsporum canis encodes a 43.5 kDa extracellular keratinolytic metalloprotease, which is thought to be one of the virulence-related factors in dermatophytosis. In order to analyze the system underlying the regulation of MEP3 gene expression, the 5'-upstream region was isolated by inverse PCR. The nucleotide sequence of a DNA fragment of about 2.1 kb containing the coding region contains putative transcription factor binding sites and transcriptional initiation points. Further analyses of the regulatory sequence may be useful for understanding the molecular basis of the coordinated expression of the various genes involved in dermatophytosis.

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.

Species-identification of dermatophytes Trichophyton, Microsporum and Epidermophyton by PCR and PCR-RFLP targeting of the DNA topoisomerase II genes

BACKGROUND

We have focused on the DNA topoisomerase II genes of pathogenic fungi and have previously applied polymerase chain reaction (PCR)-based identification of several species including the some of the major dermatophyte species.

OBJECTIVE

To identify the dermatophytes (18 species) to a species level by PCR and PCR-restriction fragment length polymorphism (RFLP) techniques, without determining the nucleotide sequence.

METHODS

The genomic DNAs of the dermatophytes (ten species of Trichophyton, seven species of Microsporum, and Epidermaphyton floccosum) were amplified by PCR using a common primer set (dPsD1) for the dermatophytes, followed by nested PCR using other primer sets (dPsD2, PsT and PsME) that contained primers specific for the DNA topoisomerase II genes of the dermatophytes. PCRs using PsT and PsME were used for the species-identification of Trichophyton, Microsporum and E. floccosum. The PCR products generated by dPsD2 were digested with restriction enzymes (Hinc II, Hinf, Afl II and PflM I), and the restriction profiles were analyzed.

RESULTS

Of the eighteen species of dermatophytes, five species (T. rubrum, T. violaceum, M. canis, M. gypseum and E. floccosum) were specifically identified by the PCR using PsT and PsME to the species level, and the remaining species were identified by the unique restriction profiles for each species in the PCR-RFLP analysis, except that the restriction profile of T. mentagrophytes var. interdigitale was identical to that of T. mentagrophytes var. quinckeanum.

CONCLUSION

PCR and PCR-RFLP techniques targeting the DNA topoisomerase II gene are simple and rapid, and quite useful as tools for the identification of dermatophytes to the species level.

Recombinant expression and antigenic properties of a 31.5-kDa keratinolytic subtilisin-like serine protease from Microsporum canis

A secreted 31.5-kDa keratinolytic subtilase (SUB3; AJ431180) is thought to be a Microsporum canis virulence factor and represents a candidate for vaccination trials. In this study, the recombinant keratinase (r-SUB3) was produced by the Pichia pastoris expression system and purified to homogeneity. Recombinant SUB3 displayed identical biochemical properties with the native protease. Experimentally cutaneously infected guinea pigs showed specific lymphoproliferative response towards r-SUB3, while no specific humoral immune response was induced except for one animal. The heterologous expression of SUB3 provides a valuable tool for addressing further investigations on the role of this keratinase in the specific cellular immune response and on its use in vaccination trials in the cat.

Molecular taxonomy of dermatophytes and related fungi by chitin synthase 1 (CHS1) gene sequences

In the present study, the nucleotide sequences of the CHS1 gene from dermatophytes and related fungi in the genera Chrysosporium, Epidermophyton, Microsporum and Trichophyton were investigated using molecular methods. About 440-bp genomic DNA fragments of the CHS1 gene from 21 species were amplified by polymerase chain reaction (PCR) and sequenced. The CHS1 nucleotide sequences of these fungi showed more than 83% similarity. The molecular taxonomy of the CHS1 gene sequences revealed that Microsporum was genetically distinct from Chrysosporium and Trichophyton, as classified by morphological characteristics.

Direct detection of dermatophytes in skin samples based on sequences of the chitin synthase 1 (CHS1) gene

For the direct detection of dermatophytes in skin scrapings and hairs from animals, a primer pair specific to the chitin synthase 1 (CHS1) gene of dermatophytes was constructed. By PCR analysis with the primer pair, dermatophyte DNA could be diagnosed directly and rapidly in clinical skin samples.

Humoral and cellular immune response to aMicrosporumcanisrecombinant keratinolytic metalloprotease (r-MEP3) in experimentally infected guinea pigs

In order to better understand the host-fungus relationship in Microsporum canis dermatophytosis and to identify major fungal antigens, the immune response to a crude exoantigen preparation and to a purified recombinant keratinolytic metalloprotease (r-MEP3) was evaluated in guinea pigs experimentally infected with M. canis. Humoral and cellular immune responses were assessed from day 0 to day 57 post-infection (PI), the former by enzyme-linked immunosorbent assay (ELISA) and the latter via a lymphocyte proliferation assay. Infected guinea pigs developed humoral and cellular responses to both M. canis exoantigen and r-MEP3, while no specific immune response to these antigens was observed in control animals. This is the first report on the development of both humoral and cell-mediated immune responses to a purified keratinase in M. canis dermatophytosis.

Secreted metalloprotease gene family of Microsporum canis

Keratinolytic proteases secreted by dermatophytes are likely to be virulence-related factors. Microsporum canis, the main agent of dermatophytosis in dogs and cats, causes a zoonosis that is frequently reported. Using Aspergillus fumigatus metalloprotease genomic sequence (MEP) as a probe, three genes (MEP1, MEP2, and MEP3) were isolated from an M. canis genomic library. They presented a quite-high percentage of identity with both A. fumigatus MEP and Aspergillus oryzae neutral protease I genes. At the amino acid level, they all contained an HEXXH consensus sequence, confirming that these M. canis genes (MEP genes) encode a zinc-containing metalloprotease gene family. Furthermore, MEP3 was found to be the gene encoding a previously isolated M. canis 43.5-kDa keratinolytic metalloprotease, and was successfully expressed as an active recombinant enzyme in Pichia pastoris. Reverse transcriptase nested PCR performed on total RNA extracted from the hair of M. canis-infected guinea pigs showed that at least MEP2 and MEP3 are produced during the infection process. This is the first report describing the isolation of a gene family encoding potential virulence-related factors in dermatophytes.

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.

Purification of diacylglycerol kinase from Microsporum gypseum and its phosphorylation by the catalytic subunit of protein kinase A

Diacylglycerol (DG) kinase (EC 2.7.1.107) was purified to homogeneity from the soluble extract of Microsporum gypseum, a dermatophyte. Purified enzyme showed a final specific activity of 2172 pmol/min/mg protein and its apparent molecular weight on SDS-PAGE was found to be 93 kDa. The activity of purified enzyme was inhibited in a dose-dependent manner in the presence of DG-kinase inhibitor (D5919, Sigma). DG-kinase activity was found to be stimulated in the presence of phosphatidylcholine, phosphatidylethanolamine, and cardiolipin while the activity was alleviated in the presence of phosphatidic acid and arachidonic acid. Kinase activity was partially inhibited when assayed after prior treatment with alkaline phosphatase. Treatment of DG-kinase with the catalytic subunit of protein kinase A (PKA)-stimulated DG-kinase activity in a dose-dependent manner. Incubation of DG-kinase with the catalytic subunit of PKA led to the phosphorylation of DG-kinase as revealed by autoradiography. The phosphorylated band disappeared completely in the presence of specific PKA inhibitor. Increased activity of DG-kinase on incubation with the catalytic subunit of PKA was possibly due to the phosphorylation of the former by the latter. Whether this in vitro phosphorylation and activation of DG-kinase occurs under physiological conditions remains to be elucidated.

Purification and characterization of a 43.5 kDa keratinolytic metalloprotease from Microsporum canis

A keratinolytic protease secreted by a feline clinical isolate of Microsporum canis cultivated in a broth containing feline keratin as the sole nitrogen source was purified from the culture filtrate by affinity chromatography on bacitracin-agarose and by hydrophobic chromatography on octyl-agarose. The enzyme had an apparent molecular mass of 43.5 kDa and the pI was 7.7. It had a significant activity against keratin azure, elastin-Congo red and denatured type I collagen (azocoll). Using the latter substrate, the optimum pH was around 8 and the apparent optimum temperature around 50 degrees C. The protease was strongly inhibited by 1,10-phenanthroline, phosphoramidon and EDTA. The first 13 N-terminal amino acid sequence showed a 61% homology with that of the extracellular metalloprotease of Aspergillus fumigatus and with the neutral protease I of A. oryzae, confirming that this 43.5 kDa keratinase is a metalloprotease. This keratinolytic metalloprotease could be a virulence-related factor involved in pathophysiological mechanisms of M. canis dermatophytosis.

Characterization of an extracellular keratinase from Microsporum canis

Extracellular keratinase (Ekase) 48-, 34- and 31.5-kDa polypeptides, which were isolated from Microsporum canis and examined by immunoblotting reacted with a monoclonal antibody against Ekase of M. canis. We analyzed the amino acid and determined the first 17 amino acid NH2-terminal sequences of the 48-, 34- and 31.5-kDa polypeptides. These polypeptides had a high aspartic acid, glycine and alanine content, respectively. The first 17 amino acid residues of the 34-kDa polypeptide were homologous to those of thermomycolin. This indicated that the 34-kDa polypeptide of Ekase is homologous to the thermomycolin produced by Malbranchea pulchella. Furthermore, Ekase was very heat-stable in the presence of 50 mM CaCl2 at 55 degrees C, since 50% of the initial activity remained. In contrast, no activity was detected after heating in the absence of CaCl2. These results indicate a close relationship between dermatophytes and M. pulchella.

Chitin synthase 1 (Chs1) gene sequences of Microsporum equinum and Trichophyton equinum

Chitin synthase 1 (Chs1) genes from Microsporum equinum and Trichophyton equinum were compared with those of the other dermatophytes. The Chs1 nucleotide sequences of these dermatophytes from horses showed more than 80% similarity to those of Arthroderma benhamiae, A. fulvum, A. grubyi, A. gypseum, A. incruvatum, A. otae, A. simii, A. vanbreuseghemii, Epidermophyton floccosum, T. mentagrophytes var. interdigitale (T. interdigitale), T. rubrum and T. violaceum. Especially high degree of nucleotide sequence similarity of more than 99% was noted between the Chs1 gene fragments of M. equinum and A. otae, and those of T. equinum, T. interdigitale and A. vanbreuseghemii, respectively. The phylogenetic analysis of their sequences revealed that M. equinum was genetically very close to A. otae and T. equinum to A. vanbreuseghemii. A molecular analysis of Chs1 genes will provide useful information for the genetic relatedness of M. equinum and T. equinum and confirm the value of DNA sequencing in identification of these two dermatophytes.

Keratinolytic activity of five human isolates of the dermatophytes

The keratinolytic activity of five species of the dermatophytes which include Trichophyton rubrum, T. mentagrophytes, T. tonsurans, Microsporum audouinii and M. gypseum isolated from school children were tested using human hair as the substrate. M. gypseum was found to possess the highest keratinolytic activity with a net value of released protein being 78.8 ug/ml after five weeks of incubation. Also the net value of released protein for T. tonsurans, T. rubrum, T. mentagrophytes and M. audouinii were 55.5 ug/ml, 52.5 ug/ml, 43.8 ug/ml and 26.3 ug/\ml respectively. Only T. mentagrophytes and M. gypseum were able to cause structural damage in form of perforations on the hair shaft. Also during the degradation of the hair, the pH of the basal medium for each dermatophyte increased. The increase in pH was highest in the medium with M. gypseum but lowest in that of M. audouinii.

The in vitro and in vivo production of a 31.5-kD keratinolytic subtilase from Microsporum canis and the clinical status in naturally infected cats

BACKGROUND

Microsporum-canis-infected cats, especially the asymptomatic infected ones, are mainly responsible for the zoonotic disease. The important variability of the clinical signs in cats is poorly understood. Recently, a 31.5-kD keratinolytic subtilase was found to be a putative virulence factor.

OBJECTIVE

To investigate the possible relationship between the clinical status of dermatophytic cats and the production of the keratinase.

METHODS

Seven M. canis strains isolated either from clinically affected, asymptomatic infected or mechanical carrier cats were tested for the in vitro production of the enzyme. The immunohistochemical detection of the enzyme was also assessed in skin biopsies of 4 symptomatic and 7 asymptomatic naturally infected cats.

RESULTS

All the strains produced in vitro a 31.5-kD keratinolytic subtilase. The enzyme was present in all but 1 of the infected cats.

CONCLUSION

The production of the keratinase is not a factor directly responsible for the clinical picture seen in M.-canis-infected cats.

Phylogenetic relation of Epidermophyton floccosum to the species of Microsporum and Trichophyton in chitin synthase 1 (CHS1) gene sequences

The Nucleotide sequence of the chitin synthase 1 (CHS1) gene of Epidermophyton floccosum, an anthrophophilic dermatophyte which is the type species of the genus Epidermophyton was analyzed to determine its phylogenetic relation to eight other dermatophyte species belonging to the genera Microsporum and Trichophyton, which were sequenced in our previous studies. A genomic DNA fragment about 620 bp in length of the CHS1 gene was amplified from E. floccosum by polymerase chain reaction (PCR) and was sequenced. The CHS1 nucleotide sequence showed more than 85% similarity with sequences derived from the other dermatophytes. Phylogenetic analyses of the sequences from E. floccosum revealed that the genus Epidermophyton may be genetically distinct from Microsporum and Trichophyton.

Inhibitors of the fungal cell wall. Synthesis of 4-aryl-4-N-arylamine-1-butenes and related compounds with inhibitory activities on beta(1-3) glucan and chitin synthases

As part of our project devoted to the search for antifungal agents, which act via a selective mode of action, we synthesized a series of new 4-aryl- or 4-alkyl-N-arylamine-1-butenes and transformed some of them into 2-substituted 4-methyl-tetrahydroquinolines and quinolines by using a novel three-step synthesis. Results obtained in agar dilution assays have shown that 4-aryl homoallylamines not possessing halogen in their structures, tetrahydroquinolines and quinolines, display a range of antifungal properties in particular against Epidermophyton floccosum and Microsporum canis. Regarding the mode of action, all active compounds showed in vitro inhibitory activities against beta(1-3) glucan-synthase and mainly against chitin-synthase. These enzymes catalyze the synthesis of beta(1-3) glucan and chitin, respectively, major polymers of the fungal cell wall. Since fungal but not mammalian cells are encased in a cell wall, its inhibition may represent a useful mode of action for these antifungal compounds.

Purification and characterization of cAMP dependent protein kinase from Microsporum gypseum

A cyclic AMP dependent protein kinase (PKA), its regulatory (R) and catalytic (C) subunits were purified to homogeneity from soluble extract of Microsporum gypseum. Purified enzyme showed a final specific activity of 277.9 nmol phosphate transferred min(-1) mg protein(-1) with kemptide as substrate. The enzyme preparation showed two bands with molecular masses of 76 kDa and 45 kDa on sodium dodecyl polyacrylamide gel electrophoresis. The 76 kDa subunit was found to be the regulatory (R) subunit of PKA holoenzyme as determined by its immunoreactivity and the isoelectric point of this subunit was 3.98. The 45 kDa subunit was found to be the catalytic (C) subunit by its immunoreactivity and phosphotransferase activity. Gel filtration using Sepharose CL-6B revealed the molecular mass of PKA holoenzyme to be 240 kDa, compatible with its tetrameric structure, consisting of two regulatory subunits (76 kDa) and two catalytic subunits (45 kDa). The specificity of enzyme towards protein acceptors in decreasing order of phosphorylation was found to be kemptide, casein, syntide and histone IIs. Purified enzyme had apparent K(m) values of 71 microM and 25 microM for ATP and kemptide, respectively. Phosphorylation was strongly inhibited by mammalian PKA inhibitor (PKI) but not by inhibitors of other protein kinases. The PKA showed maximum activity at pH 7.0 and enzyme activity was inhibited in the presence of N-ethylmaleimide (NEM) which shows the involvement of sulfhydryl groups for the activity of PKA. PKA phosphorylated a number of endogenous proteins suggesting the multifunctional role of cAMP dependent protein kinase in M. gypseum. Further work is under progress to identify the natural substrates of this enzyme through which it may regulate the enzymes involved in phospholipid metabolism.

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

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.

Histopathological pattern and humoral immune response to a crude exo-antigen and purified keratinase of Microsporum canis in symptomatic and asymptomatic infected cats

In order to understand better the mechanisms involved in the diverse clinical patterns in Microsporum canis-infected cats, the histopathological features were compared in symptomatic and asymptomatic infected cats. Additionally, the IgG immune response to a crude exo-antigen and purified keratinase of M. canis was studied by ELISA in cats of various clinical and mycological status. Acute and subacute perifolliculitis and folliculitis occurred more frequently in symptomatic than asymptomatic cats. The latter usually displayed signs of chronic inflammation and a marked infiltration of superficial dermis by mast cells, which would suggest that these animals present similarities to chronically dermatophytic humans or animals. When using a crude M. canis antigen, all infected cats were shown to have significantly higher levels of specific IgG when compared to culture negative and mechanical carrier-cats. In these non-infected animals, specific IgG was more frequently detected in adults than in young animals. No difference in anti-crude antigen specific IgG was observed between symptomatic and asymptomatic infected cats, indicating that the presence of IgG is probably unrelated to the clinical status of cats. Anti-keratinase specific IgG was only detected in one of the infected cats.

Isozyme variation within and among populations of Microsporum species

Isozyme variation among 54 isolates of Microsporum canis, 18 Microsporum cookei isolates and two Diheterospora isolates were studied using starch gel electrophoresis. Of eight enzymes examined, four were polymorphic (EST, G6P, MDH and PEP), having from two to four electrophoretic forms. Within each species, consistent and reproducible isozyme patterns of the eight enzyme systems were obtained. Phenotypic diversity (H) in M. canis was higher than in M. cookei (H = 0.459 and H = 0.408 respectively), but phenotypic differentiation of M. canis isolates from different geographical regions (Auckland, Wellington and Palmerston North, New Zealand) was low, with a proportion of total diversity (Gst) of 0.151 found among the localities. The results suggest that the isolates of M. canis from different geographical regions are closely related, supporting the theory of a common lineage.

Purification and characterization of a 315 kDa keratinolytic subtilisin-like serine protease from Microsporum canis and evidence of its secretion in naturally infected cats

A keratinolytic protease, secreted as the major component by a feline clinical isolate of Microsporum canis cultivated in a minimal medium containing cat keratin, was purified by affinity chromatography on bacitracin agarose and gel filtration. The apparent molecular mass of the enzyme was 31.5 kDa and the pI was 11.8. The enzyme was not glycosylated and its first 15 N-terminal amino acids showed numerous similarities with other fungal subtilisins. The optimum pH was around 9 while inactivation of the enzyme was reversible at pH 4, but not at pH 11. The enzyme was stable at 37 degrees C with an apparent optimum temperature around 55 degrees C. PMSF, soybean trypsin inhibitor (SBTI) and chymostatin strongly inhibited the proteinase. The highest affinity (Km of 0.37 mM) and physiological efficiency (k(cat)/Km) were obtained for the synthetic substrate N-Suc-Ala-Ala-Pro-Phe-p-nitroanilide. These results indicate that the keratinase belongs to the subtilisin-like serine protease family. Purified rabbit immunoglobulins G prepared against the keratinase and used in an immunohistochemical test allowed the detection of the keratinase produced by the fungus invading hair structures in naturally infected cats. The in vitro keratinolytic activity of the enzyme and its production in vivo suggest that it may contribute to pathogenicity.

Isozyme variation of Microsporum canis and M. cookei from New Zealand

Fifty-four isolates of Microsporum canis (Arthroderma otae) from humans, cats and dogs obtained from Auckland, Palmerston North and Wellington, New Zealand and 18 M. cookei and two Diheterospori spp. from soils were examined for variation using eight isozyme loci. M. canis isolates were from infected and non-infected cases. Isozyme analysis separated the three species which were further subdivided into electrophoretic types (ETs). Clustering analysis using normalized percentage disagreement (PTC) average linkage method revealed two clusters for M. cookei with two subclusters in cluster 2. M. canis had three main divisions (clusters 3, 4 and 5) and Diheterospora formed a separate division. The presence of isolates from different sources in the same clusters and lack of statistical significance as measured by confidence intervals suggests the existence of isolates with common lineage.

[Dermatophytes do not produce sialidase in vitro]

Sialidase (EC 3.2.1.18) is a pathogenicity factor of many microorganisms, and may also play a role in adhesion of dermatophytes to the epithelia of their hosts by the hydrolytical cleavage of terminal, negatively charged sialic acids of glycoconjugates on the cell surfaces, thus allowing fungal lectins to bind to the subterminal sugars. Therefore, 116 strains of seven species of dermatophytes were investigated for sialidase production. Two highly sensitive, quantitative sialidase assays were applied to cell homogenates and culture supernatants from seven different media of the fungi, but were always negative for sialidase activity. However, sialidase activity was always detected in Ophiostoma stenoceras used as a positive control cultivated in parallel; the enzyme was inducible by sialylated mucins. A sialidase-dependent pathomechanism for dermatophytes appears unlikely based on the results presented.

Alteration in protein kinase(s) level affects the phospholipid content in M. gypseum with modulated levels of calcium/cyclic AMP

Protein kinase(s) have been identified for the first time in Microsporum gypseum. It phosphorylated exogenous protein acceptors preferentially histone IIs and casein and are mainly localized in the cytosolic fraction of M. gypseum. Alterations in protein kinase activity was observed in calcium/aminophylline and atropine (cAMP modulators) grown cells which is due to the modulation in the Ca2+/cAMP levels. Alteration in the protein kinase(s) activity finally affected the total phospholipid content in these modulated cells of M. gypseum. These observations suggest a correlation between the activity of protein kinase(s) and phospholipid synthesis in M. gypseum. This protein kinase(s) has a broad substrate specificity and is a seryl-threonyl type protein kinase(s) as it phosphorylates exogenous (histone) and endogenous proteins at serine and threonine residues.

Partial characterization of proteolytic enzymes of Microsporum canis and Microsporum cookei

Characterization by proteinase inhibitors of the enzymes produced by Microsporum spp. revealed that Microsporum canis and Microsporum cookei produce serine proteinase(s), but only M. canis expresses aspartic and cysteine proteinases and probably a metalloproteinase. Both M. canis and M. cookei expressed metalloelastinolytic proteinases. All the proteinase types have been implicated in the pathogenicity of a wide range of microorganisms.

Multiple proteinases from two Microsporum species

Enzyme expression of 67 isolates of two Microsporum species, M. canis and M. cookei, were compared in both shake and stationary cultures using substrate copolymerized SDS-PAGE. Most M. canis isolates expressed more proteolytic bands in shake culture, while M. cookei isolates expressed more in stationary culture. M. canis isolates expressed up to six proteinases of different relative mobilities (122, 64, 62, 45, 31 and 25 kDa). M. cookei expressed up to seven proteinases in stationary culture (67, 66, 64, 62, 45, 42 and 39 kDa). Those of 67 and 66 kDa were not expressed in shake culture. The proteinases expressed by M. cookei were similar to those expressed by M. canis except for 122 and 25 kDa. With the exception of isolates from non-infected cats, 25 kDa was also commonly expressed by isolates from infected hosts in the shake culture treatment. The differences in enzyme expression obtained may reflect differences in the contrasting ecological roles of the two species.

Extracellular enzymatic activity of Microsporum canis isolates

The enzymatic activity of 70 feline and canine Microsporum canis isolates was determined by the Api-Zym test. The liquid phase of cultures, inoculated into Tryptic Soy Broth, was used to examine 19 enzymes. Considerable differences were observed among the extracellular enzymatic patterns. All the isolates produced alkaline phosphatase and beta-glucosidase, while lipase (C14), trypsin, chymotrypsin, beta-glucuronidase, and alpha-fucosidase activity was never revealed. Esterase (C4) activity was present in 57 samples (81%), esterase lipase (C8) in 31 (44%), leucine arylamidase in 35 (50%), valine arylamidase and cystine arylamidase in 7 (10%), acid phosphatase in 64 (91%), naphthol-AS-BI-phosphohydrolase in 60 (86%), alpha-galactosidase in 5 (7%), beta-galactosidase in 6 (8%), alpha-glucosidase in 25 (36%), N-acetyl-beta-glucosaminidase in 41 (58%), and alpha-mannosidase in 51 (73%). The beta-galactosidase activity of M. canis has not been reported previously. Remarkable variations of intensity for each enzymatic activity were also detected. It is believed that these results could provide basic data for further investigations on the pathogenic role of enzymes secreted by M. canis.

[Exoenzymes of dermatophytes isolated from acute and chronic tinea]

The presence of five enzymes (deoxyribonuclease, elastase, lipase, caseinase and hemolysin) in 76 strains of dermatophytes 47 of Trichophyton rubrum, 10 of T. mentagrophytes, five of T. tonsurans, 10 of Microsporum canis and four of Epidermophyton floccosum) isolated from 30 cases of acute dermatophytosis and from 46 chronic ones was determined by a qualitative plate assay; in the same way, the presence of these five enzymes with the acute and chronic dermatophytosis was correlated. It was observed that three of the enzymes were produced by the strains with a meaningful frequency; deoxyribonuclease was produced by 84.2% of the strains; elastase by 82.9%; and lipase by 65.8%. In T. rubrum the DNase was produced in 100% of strains. DNase and elastase were related to fungi which caused acute or chronic dermatophytosis in 93.3/78.2% and 96.6/74% respectively. On the other hand, lipase was present in 76% of strains, the ones that caused the chronic infections.

Polyacrylamide gel electrophoresis patterns of some Microsporum species

The paper reports observations made of various Microsporum species during a PAGE pattern study of the epidemiology of Microsporum canis. It is shown that M. audouinii can readily be distinguished from M. canis but that M. equinum is more difficult to separate. M. rivalierii was distinguishable from M. audouinii, confirming previous reports. M. distortum could not be separated from M. canis by PAGE gels of total protein or by isozyme patterns generated. There are particular problems with studies of that type on dermatophyte protein in that the intrinsic proteases degrade the preparations.

Screening the keratinolytic activity of dermatophytes in vitro

Sixteen strains out of 12 species dermatophytes were examined in respect to their ability of utilizing keratin substrates as the only sources of C and N. The employed keratin substrates included a solubilized preparation of feather keratin (KS) and native keratin, guinea pig hair and chicken feathers. It has been shown that the preparation KS constitutes a convenient model for a preliminary estimation of fungal keratinolytic activity and it can be a source of information about the localization of these enzymes. It has been found that, among the 16 fungal strains, 13 strains synthesize mainly intracellular keratinases while 3 strains of T. verrucosum release enzymes mainly to the medium. Native keratin from hair and feathers was degraded only by some of the examined strains which, under the experimental conditions, developed characteristic spore forms. Keratin of guinea pigs hair was attacked only by the T. mentagrophytes strains, T. verrucosum and K. ajelloi, and only T. gallinae grew on native keratin from chicken feathers.

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.

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

A keratinolytic proteinase (KPase) which is regarded as an important factor in the pathogenesis of dermatophytosis was isolated and purified from Microsporum (M.) canis culture filtrates. Enzyme-linked immunosorbent assay (ELISA) was used to determine the occurrence of circulating antibodies to this enzyme in sera samples from guinea pigs with superficial fungal infections caused by M. canis. Of sera samples from guinea pigs infected with M. canis, 75% were reactive within 10 weeks, however, those ELISA values were relatively low compared with those from guinea pigs immunized with KPase. The presence of circulating antibodies was first detected 2 weeks post inoculation with M. canis, corresponding to the period when the lesions were most severe. The titers of the ELISA antibodies reached a peak at 4 weeks; at that time the lesions had disappeared completely.

Brief communication: extracellular enzymatic activities of dermatophytes

Eighty dermatophyte strains belonging to the genera Trichophyton, Microsporum, Epidermophyton and Chrysosporium were screened for their ability to produce extracellular enzymes using a semiquantitative method. The results obtained vary significantly when the studied genera are observed separately, though the enzyme beta-galactosidase was detected in none of the four studied genera.

Isolation of an extracellular proteinase (keratinase) from Microsporum canis

Proteolytic activity was demonstrated when a strain of Microsporum canis was cultured in broth with human hair, but not in the medium without hair. The extracellular proteinase (keratinase) was isolated and purified by chromatography. Disc electrophoresis showed one protein band of extracellular proteinase, and the antibody against this enzyme gave a single precipitin line in agar diffusion. The IgG fraction completely neutralized the proteinase activity. The proteinase of M. canis may play a role in infection caused by this fungus, by affecting keratinized tissue such as stratum corneum and hair.

The nuclear DNA-dependent ribonucleic acid polymerases of the dermatophytic fungus Microsporum gypseum

The DNA-dependent RNA polymerases of the dermatophytic fungus Microsporum gypseum were partially characterized. Nuclear extracts prepared from vegetative mycelia were fractionated by DEAE-Sephadex chromatography into three enzyme species which resembled in most of their characteristics those of other eukaryotic organisms.