Purification, immunochemical and biological characterization of malate dehydrogenase of Schistosoma mansoni

Two-dimensional electrophoresis of Malassezia allergens for atopic dermatitis and isolation of Mal f 4 homologs with mitochondrial malate dehydrogenase

The yeast Malassezia furfur is a natural inhabitant of the human skin microflora that induces an allergic reaction in atopic dermatitis. To identify allergens of M. furfur, we separated a crude preparation of M. furfur antigens as discrete spots by 2-D PAGE and detected IgE-binding proteins using sera of atopic dermatitis patients. We identified the known allergens, Mal f 2 and Mal f 3, and determined N-terminal amino acid sequences of six new IgE-binding proteins including Mal f 4. The cDNA and genomic DNA encoding Mal f 4 were cloned and sequenced. The gene was mitochondrial malate dehydrogenase and encoded Mal f 4 composed of 315 amino acids and a signal sequence of 27 amino acids. We purified Mal f 4, which had a molecular mass of 35 kDa from a membrane fraction of a lysate of cultured cells. Thirty of 36 M. furfur-allergic atopic dermatitis patients (83.3%) had elevated serum levels of IgE to purified Mal f 4, indicating that Mal f 4 is a major allergen. There was a significant correlation of the Phadebas RAST unit values of Mal f 4 and the crude antigen, but not between Mal f 4 and the known allergen Mal f 2.

Specificity of the solid phase alkaline phosphatase immunocapture assay for the diagnosis of human Schistosoma mansoni infection

The species specificity of the solid phase alkaline phosphatase immunocapture assay (APIA) for the immunological detection of human immunoglobulin G antibodies to the alkaline phosphatase of adult Schistosoma mansoni was evaluated. Sera from schistosomiasis patients from South America, West Africa, south-east Asia and uninfected control subjects were compared. Only the sera of patients infected with S. mansoni gave positive results. There was no apparent difference between 2 populations infected with S. mansoni, one from South America and the other from West Africa. The results with sera from various regions of West Africa were also indistinguishable. Although the APIA was not able to discriminate the geographical origin of the S. mansoni-infected subjects, the method appeared to be specific for S. mansoni and suitable for use in the immunodiagnosis of schistosomiasis mansoni, particularly in endemic areas where mixed infections of Schistosoma spp. occur.

Experimental host-induced selection in Schistosoma mansoni strains from Guadeloupe and comparison with natural observations

Allelic frequency variation at the malate dehydrogenase (E.C.1.1.1.37) polymorphic locus (Mdh-1) was analysed during several successive generations in four strains of Schistosoma mansoni from Guadeloupe, maintained experimentally on mice. A rapid evolution of the frequency of the Mdh-1a allele is interpreted as being the result of an interaction between experimental drift and selection induced by the murine laboratory host. These experimental results are compared to the genetic structures observed among the corresponding natural populations of S. mansoni in Guadeloupe (West Indies). They strengthen the hypothesis of a natural host-induced selection by the murine host (Rattus rattus), which, in Guadeloupe, plays the role of host reservoir for this human schistosome.

Immunocapture assay for quantification of human IgA antibodies to parasite antigenic enzymes. Application with the alkaline phosphatase of Schistosoma mansoni

Conditions are described for using solid phase adsorbed jacalins in an immunocapture assay for IgA antibodies to the alkaline phosphatase of Schistosoma mansoni. Microtiter plates were activated with polylysine and jacalins were covalently adsorbed by means of glutaraldehyde. From three different jacalins, the one purified from seeds of Artocarpus tonkinensis showed the lowest non-specific adsorption and was used for further studies. Comparing solutions of bovine serum albumin, ovalbumin and Tween 20, it was shown that the latter was most successful in blocking non-specific adsorption. Low serum dilutions resulted in a less efficient IgA capture by the adsorbed jacalin than higher dilutions. Under optimal working conditions, a high correlation could be shown between the presence of specific anti-alkaline phosphatase antibodies of IgA isotype and IgG isotype.

Antigenicity of adult Schistosoma mansoni alkaline phosphatase

Antibodies to the alkaline phosphatase (AP) of Schistosoma mansoni in infected human and mice sera were evaluated by a direct solid-phase AP immunoadsorption assay (APIA) and by Western blot and immunostaining. APIA consisted of (a) solid-phase capture of immunoglobulins from infected human or mice, (b) immunoadsorption of the enzyme antigen by the antibodies, and (c) detection of the enzymatic activity. By this procedure the appearance of the anti-AP response in mice was detected around 50 days post-infection; this response was not specific for an AP of a given schistosome strain and it was not induced by an autoimmunity phenomenon. Fourteen out of 15 sera from infected people tested by APIA showed a clear antibody response against this enzyme. Immunoblots in non-reducing conditions supported APIA results indicating that the parasite AP was specifically recognized by the antibodies present in infected human and mice sera. These results suggest the possible usefulness of the schistosome AP as a marker for S. mansoni infection.

Immunodiagnosis of Schistosomiasis mansoni with APIA (alkaline phosphatase immunoassay)

The previously shown antigenicity of Schistosoma mansoni (JL venezuelan strain) alkaline phosphatase (Mg2+, pH 9.5) allowed its use in an immunodiagnosis assay, that consisted in the immunoadsorption of the enzymatic activity. Protein-A coated polyvinyl plates were used as solid phase to capture IgG from sera of infected human patients. After buffered saline washings, the plates were incubated with an enzyme-rich fraction (a n-butanol aqueous extract of adult worm obtained from pairs). Immunoadsorbed alkaline phosphatase (AP) was revealed by adding rho-nitrophenyl phosphate. Anti-AP antibodies were detected in 93% of coproparasitologically proven S. mansoni-infected venezuelan patients but not in parasite-free control sera and sera from patients infected with parasitosis other than schistosomiasis. The APIA did not correlate with cure but the anti-AP antibody response was progressively reduced after treatment. The use of an AP substrate amplifying system allowed an improvement of the assay sensitivity without loss of specificity. The data suggest that the APIA could be used as a marker of infection by S. mansoni.

Allelic frequency variations at the MDH-1 locus within Schistosoma mansoni strains from Guadeloupe (French West Indies): ecological interpretation

1. An isoenzymatic study on Schistosoma mansoni from Guadeloupe has been carried out using isoelectric focusing in polyacrylamide gels. 2. Among the seven systems examined (LDH, MDH, G6PD, PGI, PGM, AcP, HK), only MDH showed variation at the MDH-1 locus and mdh-1a allele frequencies were used to characterise eight strains derived either from human or murine hosts, and representative of different transmission sites. 3. In comparison with criteria previously employed to type these strains (ecological context of their transmission sites, cercarial emergence patterns), mdh-1a frequency variations have been correlated to the degree of participation of the murine host reservoir in the parasite transmission dynamics within the different foci of Guadeloupe.

Molecular cloning of Schistosoma mansoni myosin

A cDNA library representative of adult Schistosoma mansoni mRNA populations was screened with serum from infected rats (refractory hosts), positive plaques being rescreened with serum from infected mice and humans. Based on general reactivity, one clone was selected for further study. As judged by immunofluorescence data, size of corresponding mRNA, and nucleotide sequence analysis, the recombinant expresses approximately 625 amino acids of a schistosome muscle myosin rod. Antibodies evoked by the protein do not cross-react with human cardiac or skeletal muscle, are not invariably stimulated in naturally infected human beings, and rise in titer after chemotherapeutic cure, findings which suggest that the antigen is not a causative agent of Katayama fever, and is probably presented by degenerating worms. The schistosome sarcomeric myosin gene, the most primitive examined to date, appears to be unique inasmuch as it may not be a member of a multigene family and encodes a single mRNA transcript; nonetheless, predicted higher order structure of its translation product is consistent with expected function.

Antigenic properties of Schistosoma mansoni aminopeptidases: evolution during the development in mammalian hosts

The involvement in the immunity to schistosomiasis of an aminopeptidase activity of schistosomula, 20-day-old and adult worms of Schistosoma mansoni has been studied. This activity, hydrolysing leucine-p-nitroanilide and alanine-p-nitroanilide at pH 7.4 was immunoprecipitated by various infected rat and human sera. These antigenic enzymes were expressed at day 28 after infection in the rat and seemed to be specific for the Schistosoma species. Several aminopeptidase activities were found after analysis by isoelectric focusing of the adult extract but only the pI 8.3 peak was antigenic. Three antigenic peaks were demonstrated after AcA 34 Ultrogel filtration. The biological relevance of these antigenic enzymes in schistosomiasis is discussed.

Detection of Schistosoma mansoni M antigen in circulating immune-complexes and in kidneys of infected hamsters

Circulating M antigen (CMA) of Schistosoma mansoni was found in the trichloroacetic acid (TCA) soluble fraction of a polyethylene glycol precipitate of serum from infected hamsters. It was also found as a TCA-soluble component in an immunoglobulin-containing fraction eluted from infected hamster kidneys. It was not found in similarly treated control sera nor in the products of acid dissociation of circulating immune complexes (CIC) from infected hamster sera. CMA was not detected in the kidneys of normal hamsters. Precipitating anti-M antigen antibodies were present in one of 10 sera from infected hamsters, but not in the eluates of hamster kidneys. These results indicate that CMA is present in circulating immune complexes in infected hamsters. The presence of CMA in kidneys from the same hamsters suggests a possible role for circulating antigens in immune-complexed form in the aetiology of glomerulonephritis in S. mansoni infection.

Separation and comparative immunoassay (DASS, ELISA) with antigens from adult Schistosoma mansoni

Antigenic fractions were prepared from adult Schistosoma mansoni by homogenization and solubilization in phosphate buffer, and subsequent separation on Ultrogel AcA-44. The fractions were tested for antigenicity in two immunodiagnostic techniques, the defined antigen substrate spheres (DASS) system, and the enzyme-linked immunosorbent assay (ELISA), using serum from schistosomiasis patients. The results obtained in the two tests correspond to each other. Sera from 25 patients with proven schistosomiasis were tested with ELISA, using the antigen fractions. For all sera tested, the titres obtained, were dependent on the antigen fraction used. However, areas of high antigenicity were different for different sera. Antigens with molecular weight lower than 60,000, gave negative results for about 30% of the sera but those with molecular weight higher than 60,000 gave positive results for all sera. For about 60% of the sera, the sensitivity of ELISA increased when antigens of increasing molecular weight were used. Cross reactions with two other helminth infections occurred mainly with high molecular weight antigens.