R.J. Hay

Purification, N-Terminal Amino Acid Sequence and Partial Characterization of A Cu,Zn Superoxide Dismutase From the Pathogenic Fungus Aspergillusfumiga Tus

A superoxide dismutase (SOD) has been purified to homogeneity from the fungal pathogen Aspergillus fumigatus using a combination of cell homogenization, isoelectric focusing and gel filtration FPLC. The N-terminal amino acid sequence of the purified enzyme demonstrated substantial homology to known Cu,Zn superoxide dismutases for a range of organisms, including Neurospora crassa and Saccharomyces cerevisiae. The enzyme subunit has a pI of 5.9, a relative molecular mass of 19 kDa and a spectral absorbance maximum of 550nm. The non reduced enzyme has a relative molecular mass of 95 kDa. The enzyme remained active after prolonged incubation at 70 degrees C and was pH insensitive in the range 7-11. Potassium cyanide and diethyldithiocarbamate, known Cu,Zn SOD inhibitors, caused inhibition of the purified enzyme at working concentrations of 0.25 mM, whilst sodium azide and o-phenanthroline demonstrated inhibition at higher concentrations (10-30 mM). SOD activity was also detectable in culture filtrate of A. fumigatus. This enzyme may have a potential role as a virulence factor in the avoidance of neutrophil and phagocyte oxidative burst killing mechanisms.

A murine monoclonal antibody exhibiting high species specificity for Histoplasma capsulatum var. capsulatum.

A monoclonal antibody (mAb) exhibiting a high degree of species specificity for the yeast phase of the dimorphic fungus Histoplasma capsulatum was produced by a modification of the standard mAb production protocol. The technique for generating mAbs involved the use of the immunosuppressive drug cyclophosphamide to diminish the response in mice to immunodominant cross-reactive epitopes. This mAb exhibited clear specificity and did not react by ELISA with the closely related genera Blastomyces, Paracoccidioides and Sporothrix. In Western blots it recognized a linear determinant on a 70-75 kDa molecule in H. capsulatum antigen, with an extremely faint reactivity to antigens of identical molecular mass derived from Sporothrix and Paracoccidioides, and no reactivity against Blastomyces antigen.

Combined Use of Paracoccidioides brasiliensis Recombinant 27-Kilodalton and Purified 87-Kilodalton Antigens in an Enzyme-Linked Immunosorbent Assay for Serodiagnosis of Paracoccidioidomycosis

ABSTRACT The diagnosis of paracoccidioidomycosis (PCM) has relied on the identification of the hosts humoral response by using a variety of immunological methods, such as complement fixation and immunodiffusion. Although these approaches are useful, historically their sensitivity and specificity have often been compromised by the use of complex mixtures of undefined antigens. The use of combinations of purified, well-characterized antigens appears preferable and may yield optimum results. Accordingly an indirect enzyme-linked immunosorbent assay (ELISA) using combinations of the previously described 27-kDa recombinant antigen and the 87-kDa heat shock protein were used for diagnosis and follow-up of patients with PCM. A total of 37 patients classified according to their clinical presentations (7 with the acute or subacute form of the disease, 22 with the chronic form of the disease, and 8 with the chronic unifocal form) were studied. Eighteen of these patients were also evaluated at every follow-up appointment. Forty serum samples from patients with other diseases and 50 serum samples from healthy individuals were also studied. Detection of anti-27-kDa and anti-87-kDa antibodies in sera of patients with PCM by ELISA using a combination of the two purified proteins showed a sensitivity of 92% with a specificity of 88% in comparison with normal human sera and 90% in comparison with the heterologous sera. These results demonstrated a significant increase in sensitivity and specificity compared to results when the antigens were used separately. Thus, the use of combinations of well-defined antigens appears to offer clear advantages over the use of single antigens when diagnosing PCM.

Evidence that the M antigen of Histoplasma capsulatum var. capsulatum is a catalase which exhibits cross-reactivity with other dimorphic fungi

A panel of monoclonal antibodies (Mabs) was raised against histoplasmin, the antigen derived from the mycelial phase of Histoplasma capsulatum var. capsulatum which contains the diagnostically useful H and M antigens. A number of Mabs were obtained which recognized a 70-75 kD component of an antigenic preparation of H. capsulatum var. capsulatum by Western blotting. When reacted with histoplasmin by Western blotting the Mabs recognized a similar 70-75 kD band, together with a series of higher molecular mass bands at approximately 130, 190 and 230 kD, a pattern which correlates strongly with both the published relative molecular mass (Mr) of the M antigen and the known subunit structure of the enzyme catalase. These Mabs were also shown to recognize a commercial preparation of Aspergillus niger catalase by ELISA. Other dimorphic fungi were also reactive with these Mabs by Western blotting, indicating the presence of common epitopes on the catalase molecules of these species.

Paracoccidioides brasiliensis 87-kilodalton antigen, a heat shock protein useful in diagnosis: characterization, purification, and detection in biopsy material via immunohistochemistry.

ABSTRACT The 87-kDa antigen derived from the fungal pathogen Paracoccidioides brasiliensis can be detected in the sera of infected patients, and its levels have been shown to correlate well with response to treatment and with clinical cure. Despite its potential importance, the antigen has been poorly characterized. The 87-kDa antigen was purified to homogeneity via preparative gel electrophoresis; N-terminal amino acid sequencing revealed substantial homology with heat shock proteins (hsps) from a variety of organisms. A monoclonal antibody (MAb) raised against a Histoplasma capsulatum 80-kDa hsp showed cross-reactivity to the purified 87-kDa antigen via Western blotting, and the 87-kDa-specific MAb P1B demonstrated that the antigen was expressed at higher levels in yeast than in mycelia by the same technique. Enzyme-linked immunosorbent assay and immunofluorescence reactivity using P1B confirmed increased expression of the 87-kDa antigen during the temperature-induced transformation of mycelia to yeast. Yeast-to-mycelium transformation was accompanied by a fall in expression, although the 87-kDa antigen was clearly constitutively expressed in both phases. Immunochemical staining of tissues from patients with MAb P1B who were infected with P. brasiliensis confirmed in vivo expression of the 87-kDa antigen by yeasts, and identification of this antigen via this method appears to be a useful adjunct to other methods used to diagnose paracoccidioidomycosis.

Post-operative responses of paranasal Aspergillus granuloma to itraconazole

Paranasal Aspergillus granuloma is an invasive infection, seen mainly in tropical countries, involving the paranasal sinuses, orbit and brain. Previously surgical excision has been followed by a high relapse rate, 80% in some series, and mortality. This study involved the use of post-operative therapy with oral itraconazole in doses of 200-300 mg daily. Twenty-two patients were treated for a mean period of 19.7 weeks. Of 19 patients for whom follow-up data were available, 12 (62%) were rated as being in complete remission in a mean period of 17.2 months after the end of therapy. Only one patient developed progressive disease during itraconazole therapy. No serious adverse effect was seen. Use of itraconazole shows promise as a means of preventing relapse after surgery in this progressive infection.

Ultrastructural and immunogenic changes in the formation of mycetoma grains.

The differences in the fine structure and antigenic determinants of mycetoma fungi in the mycelial phase in vitro and in grains in vivo facilitate an interpretation of grain formation. Aggregates of hyphal elements with multiple and thickened walls was a feature of the fungi in vivo. Associated with hyphal wall material, numerous polysaccharide microfibrils were detected in grains of Madurella mycetomatis. These were not seen associated with hyphal elements in vitro and it is suggested that these structures may be concerned with the aggregation of fungal elements in the formation of grains. Antibodies directed against the fungi in vitro were shown, by indirect immunogold labelling, to bind at identical sites in fungal material grown in vitro as in mycetoma grains. However the grain matrix was not labelled, suggesting that part of the structure formed in vivo is composed of modified antigen or is host derived.

Possible mechanisms of immune modulation in chronic dermatophytoses: an in vitro study

Summary It has been suggested that patients with chronic superficial Trichophyton rubrum infection have defective cellular immunity to dermatophyte antigens. This may be due to a selective anergy to dermatophyte antigens or reflect the activity of dermatophyte‐derived lymphocyte inhibitory factors. To explore these possibilities, we assessed lymphocyte transformation to a variety of recall antigens, including a cytoplasmic and exoantigen preparation of Trichophyton rubrum in 15 patients with chronic dermatophyte infection and 15 age‐and sex‐matched positive controls. In a duplicate set of experiments, autologous serum was replaced by heat‐inactivated fetal calf serum. In addition, the direct effect of Trichophyton rubrum extracts on lymphoproliferation was assessed in vitro.

Cutaneous Mycobacterium kansasii infection--treatment with erythromycin.

A 20‐year‐old woman developed cutaneous Mycobacterium kansasii infection following steroid infiltration of two plaques of lichen simplex. The organism was resistant to many standard antituberculous drugs and following sensitivity studies treatment with erythromycin was begun. This has been effective and well tolerated. Treatment of atypical mycobacteria with drugs not traditionally associated with antituberculous activity is being increasingly reported and, so far, resistance has not been a problem. Erythromycin has good tissue penetration with excellent activity against M. kansasii and should be considered in the therapy of similar cases.

Superoxide dismutase of Cryptococcus neoformans: purification and characterization

We have purified to homogeneity a putative superoxide dismutase of 19.5 kDa from the pathogenic yeast Cryptococcus neoformans by homogenization, isoelectric focusing and gel filtration. The N-terminal amino acid sequence of this protein indicates a significant sequence homology with known manganese-containing superoxide dismutases (Mn-SODs) from various organisms. In addition, the presence of superoxide dismutase activity was confirmed using specific substrate gels which detect this enzyme when nitro-tetrazolium blue reduction is prevented by the photochemical source of superoxide, in the presence of riboflavin when exposed to light. Superoxide dismutase activity was also assayed using cytochrome c. The molecular weight of the native enzyme (on non-denaturing gels) is 80 kDa. The optimum pH for the enzyme is 7.5 and its pi = 6.6. The enzyme was inhibited by sodium dodecyl sulphate, sodium azide, o-phenanthroline, and EDTA, in descending order.