Isolation and characterization of an immunogenic fragment of heat shock protein 60 from Trichophyton mentagrophytes. Isolierung und Charakterisierung eines immunogenen Fragmentes des Hitzeschockproteins 60 von Trichophyton mentagrophytes

The possible role of dermatophyte cysteine dioxygenase in keratin degradation

Cysteine dioxygenase (CDO, EC 1.13.11.20) is a key enzyme involved in the homeostatic regulation of cysteine level and in production of important oxidized metabolites of cysteine such as pyruvate, sulphite, sulphate, hypotaurine, and taurine in all eukaryotic cells. The intracellular CDO concentration is regulated at both transcriptional and posttranslational levels. In several fungi, CDO plays an important role as a virulence factor involved in morphological transition from yeast to mycelial forms. CDO is crucial for oxidation of cysteine to cysteine sulphinic acid and therefore for sulphite production and secretion. Because sulphite cleaves disulphide bridges as a first unavoidable step in keratinolysis, it is hypothesized that in dermatophytes, CDO is a virulence factor crucial for keratin degradation.

Isolation of recombinant cysteine dioxygenase protein from Trichophyton mentagrophytes

Cysteine dioxygenase (CDO, EC 1.13.11.20) catalyses the oxygenation of cysteine to cysteine sulphinic acid leading to the production of sulphite, sulphate and taurine as the final metabolites of cysteine catabolism. Keratinolytic fungi secrete sulphite and sulphate to reduce disulphide bridges in host tissue keratin proteins as the first step of keratinolysis. In the present study, we describe the identification of cDNA, as well as expression and characterisation of recombinant CDO protein from Trichophyton mentagrophytes. The cDNA was amplified using primers designed on the basis of high conservancy CDO regions identified in other fungi. PCR product was cloned and sequenced. Recombinant CDO was expressed in Escherichia coli, and affinity purified and identified by matrix-assisted laser desorption/ionization - time-of-flight mass spectrometry (MALDI-TOF MS). Enzyme activity was assayed by monitoring the production of cysteine sulphinate using mass spectrometry. The Cdo cDNA encodes for a protein consisting of 219 amino acids. Recombinant CDO protein C-terminally fused with a His tag was purified by affinity chromatography. The CDO purified under native condition was proved to be enzymatically active. Protein identity was confirmed by MALDI-TOF MS. Comparison of cDNA sequence with those identified in other fungi revealed significant homology. Identification of T. mentagrophytes CDO provides indispensable tools for future studies of dermatophyte pathogenicity and development of new approaches for prevention and therapy.

Molecular detection and characterisation of fungal heat shock protein 60

Heat shock proteins (Hsp) are highly conserved molecules, which are both constitutively expressed and up-regulated in response to various stress conditions. In particular, fungal Hsp60 can act as immunodominant antigens and facilitate powerful immunological properties. A possible cellular heat shock response was investigated in eight fungi (Aspergillus fumigatus, Aspergillus terreus, Penicillium chrysogenum, Cladosporium cladosporioides, Scedosporium apiospermum, Trichophyton mentagrophytes, Candida albicans and Saccharomyces cerevisiae). Fully automated RNA extraction was followed by quantitative real-time RT-PCR targeting fungus-specific Hsp60 mRNA and sequencing of the amplicon. Levels of temperature-dependent gene expression were evaluated and rates of similarity and identity were compared. While Hsp60 mRNA was constitutively expressed in all the samples tested, a temperature-dependent induction was not shown in C. cladosporioides. In the 80-amino acid fragment from the hypothetical protein, 66% of the amino acids were identical, 20% showed a conserved and 8% a semi-conserved substitution. Our findings should contribute to a better understanding of host-pathogen relationship and suggest that fungal Hsp60 under temperature-related stress conditions might act as an immunogenic trigger in orchestrating fungi-related diseases.

Excretion-secretion products and proteases from live Sporothrix schenckii yeast phase: immunological detection and cleavage of human IgG

Antigenic preparations from Sporothrix schenckii usually involve materials from mixed cultures of yeast and mycelia presenting cross-reactions with other deep mycoses. We have standardized pure yeast phase with high viability of the cells suitable to obtain specific excretion-secretion products without somatic contaminations. These excretion-secretion products were highly immunogenic and did not produce noticeable cross-reactions in either double immunodiffusion or Western blot. The antigenic preparation consists mainly of proteins with molecular weights between 40 and 70 kDa, some of them with proteolytic activity in mild acidic conditions. We also observed cathepsin-like activity at two days of culture and chymotrypsin-like activity at four days of culture consistent with the change in concentration of different secreted proteins. The proteases were able to cleave different subclasses of human IgG suggesting a sequential production of antigens and molecules that could interact and interfere with the immune response of the host.

Quantitative real-time PCR study on persistence of pDNA vaccine pVax-Hsp60 TM814 in beef muscles

Background

Application of plasmid DNA for immunization of food-producing animals established new standards of food safety. The addition of foreign products e.g. pDNA into the food chain should be carefully examined to ensure that neither livestock animals nor consumers develop unpredicted or undesirable side-effects.

Methods

A quantitative real-time PCR (QRTPCR) methodology was developed to study the biodistribution and persistence of plasmid DNA vaccine pDNAX (pVAX-Hsp60 TM814) in mice and beef cattle. The linear quantification range and the sensitivity of the method was found to be 10 – 10⁹ copies per reaction (500 ng/gDNA) and 3 copies per reaction, respectively.

Results

Persistence of pDNAX in mice muscle tissue was restricted to injection site and the amount of pDNAX showed delivery formulation dependent (naked pDNA, electroporation, cationic liposome complexes) and mouse age-dependent clearance form injection site but pDNAX was still detectable even after 365 days. The QRTPCR analysis of various muscle tissue samples of vaccinated beef bulls performed 242–292 days after the last revaccination proved that residual pDNAX was found only in the injection site. The highest plasmid levels (up to 290 copies per reaction) were detected in the pDNAX:CDAN/DOPE group similarly to mice model. No pDNA was detected in the samples from distant muscles and draining lymph nodes.

Conclusion

Quantitative real-time PCR (QRTPCR) assay was developed to assess the residual pDNA vaccine pVAX-Hsp60 TM814 in mice and beef cattle. In beef cattle, ultra low residual level of pDNA vaccine was only found at the injection site. According to rough estimation, consumption of muscles from the injection site represents almost an undetectable intake of pDNA (400 fg/g muscle tissue) for consumers. Residual plasmid in native state will hardly be found at measurable level following further meat processing. This study brings supportive data for animal and food safety and hence for further approval of pDNA vaccine field trials.

Immunoprophylaxis of dermatophytosis in animals

Dermatophytosis is a relatively common disease in many countries occurring endemically both in companion and food animals. Fungi belonging to the genera Trichophyton and Microsporum are most often isolated from clinical cases. Measures to control and prevent dermatophytosis include sanitation, hygienic measures and treatment. In some countries, successful control and eradication have been achieved by mass vaccination of cattle and fur-bearing animals. Vaccines containing live attenuated cells of the fungus stimulate a cell-mediated immune response conferring long-lasting protection against subsequent challenge by the homologous fungus. A delayed type hypersensitivity (DTH) skin test using appropriate dermatophyte antigens is suitable to assess the response. Inactivated dermatophyte vaccines are available for use in cattle, horse, dog, and cat in some countries. However, the scientific literature is scarce making it difficult to conclude on efficacy and appropriate use. Current vaccines are all first generation vaccines. Attempts have been made to prepare subunit vaccines based on new knowledge about virulence factors like the keratinases, so far with limited success. Candidate antigens must be able to stimulate a strong T helper 1 cell response and future research should focus on identification of major T-cell epitopes that specifically elicit a DTH reaction. Dermatophytosis is a zoonotic disease. In Norway and a few other countries, systematic vaccination against cattle ringworm has almost eliminated the disease, and ringworm in man caused by T. verrucosum is almost nonexistent. A similar benefit could be expected if a safe and efficacious vaccine was available for Microsporum canis infection in cats and dogs.

Clinical assessment of postinfection, postcontact and postvaccination immunity manifestation after experimental inoculation of calves with Trichophyton verrucosum culture

Immunity against ringworm has been well examined, but the knowledge of its development after repeated infection is limited. Therefore, the immunity developed after a single or double contact with various doses of Trichophyton verrucosum strain was investigated in calves which had or had not shown any signs of ringworm after contact with dermatophyte. In total six individual experiments were performed on 117 calves. Experimental infection with the virulent T. verrucosum strain was used to investigate the animals' immunity. Calves showing severe trichophytosis after application of high doses of T. verrucosum culture were immune to reinfection by equally high doses of this dermatophyte. A similar protection level was reached after intramuscular revaccination or after recovery from trichophytosis with moderate course induced by two inoculations of low doses. If moderate course of illness had been induced by same single dose, the immunity was lower. Animals displaying no signs of trichophytosis after inoculation with the low doses developed insufficient immunity. There was no immunity against reinfection in animals having previous contact with subinfectious doses through undamaged skin. The results obtained suggest that the level of postinfection immunity depends on the disease extent and the frequency of administration of the infectious agent. The development of postcontact immunity cannot be excluded in calves.

Recombinant protein and DNA vaccines derived from hsp60 Trichophyton mentagrophytes control the clinical course of trichophytosis in bovine species and guinea-pigs

Heat shock proteins (hsp) were identified in many infectious agents as immunodominant antigens with a protective effect. Immunization of laboratory animals by selected representants of hsp60, hsp70 and hsp90 isolated from several pathogens induced protective host immunity and significantly reduced clinical manifestation of infection. The present study involves preparation of a recombinant protein vaccine and a DNA vaccine. Both vaccines were derived from the hsp60 of the dermatophyte, Trichophyton mentagrophytes. Challenge trials with evaluation of the protective effect of vaccination were performed on calves and guinea-pigs. Both vaccination procedures reduced, in statistically significant fashion, the clinical course of skin mycosis in calves experimentally inoculated with the dermatophyte, T. mentagrophytes. In experiments with guinea-pigs, increased protection was only seen with DNA vaccination. After DNA vaccine application, no paravaccination side-effects (granulomas at the injection site, changed total state of the animal) were observed. Only vaccination with the recombinant protein in calf's experiment induced specific serum antibodies. This observation indicates that antibodies are not associated with protection. In summary, DNA vaccine hsp60 is the most promising for prevention of bovine trichophytosis.