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A J Simpson

Publications and source records attributed to A J Simpson.

At least 181 records · Page 10Linked to original sources
PubMed1986

IgM antibodies recognizing carbohydrate epitopes shared between schistosomula and miracidia of Schistosoma mansoni that block in vitro killing.

A series of monoclonal antibodies (mAb) was raised in mice against Schistosoma mansoni, which recognized a carbohydrate determinant on a major Mr greater than 200,000 schistosomulum surface antigen. These mAb cross-reacted with the surface of cercariae and miracidia and with schistosomula of S. haematobium and S. bovis. Other mAb were generated that only recognized a Mr 20,000 schistosomulum surface antigen; they did not cross-react with eggs or miracidia and were species specific. The anti-Mr 20,000 mAb of the IgG1 isotype exhibited high levels of complement-dependent cytotoxicity to schistosomula in vitro. IgM mAb that recognized carbohydrate epitopes of the Mr greater than 200,000 surface antigen blocked the lethal activity of the anti-Mr 20,000 mAb. The IgM anti-Mr greater than 200,000 mAb also reduced complement-dependent cytotoxicity of serum from mice vaccinated with irradiated cercariae.

Animals↗
PubMed1986

The presence of antibody in mice chronically infected with Schistosoma mansoni which blocks in vitro killing of schistosomula.

We have previously reported that IgM monoclonal antibodies (mAb) that recognize surface carbohydrate determinants shared between schistosomula, cercariae, and miracidia block antibody/complement dependent killing of schistosomula in vitro. Binding assays that make use of one of the IgM mAb labeled with 125I demonstrated that serum from chronically infected mice (CMS) contained high levels of competing antibody, whereas serum from mice vaccinated with irradiated cercariae (VMS) contained little antibody of this specificity. Absorption of CMS with cercariae that removed antibodies to schistosomulum surface carbohydrate determinants increased its ability to kill schistosomula in vitro; absorption of VMS with cercariae failed to alter the lethal activity of the serum. Furthermore, fractionation of CMS by protein A Sepharose chromatography demonstrated that the IgG fraction had an increased lethal activity compared with unfractionated serum; this result was not seen with VMS. Finally, the IgM fraction of CMS was shown to block in vitro killing of the IgG fractions of both CMS and VMS. These data suggest that the blocking activities observed with the IgM mAb are contained within the serum of chronically infected mice but not in the serum of mice vaccinated with irradiated cercariae.

Animals↗
PubMed1986

A major role for carbohydrate epitopes preferentially recognized by chronically infected mice in the determination of Schistosoma mansoni schistosomulum surface antigenicity.

A radioimmunoassay that makes use of whole schistosomula and 125I-labeled protein A has been used to characterize and to quantify the binding of antisera to the surface of 3 hr mechanically transformed schistosomula of Schistosoma mansoni. This technique facilitates the determination of epitopes on the schistosomula in addition to those detected by surface labeling and immunoprecipitation. By using this technique, it has been demonstrated that there is a much greater binding to the parasite surface of antibodies from chronically infected mice (CMS) than of antibodies from mice infected with highly irradiated cercariae (VMS), and CMS recognizes epitopes that VMS does not. Treatment of the surface of the schistosomula with trifluoromethanesulphonic acid and sodium metaperiodate has suggested that the discrepancy of the binding between the two sera is due to the recognition of a large number of additional epitopes by CMS, which are carbohydrate in nature. Some of the carbohydrate epitopes are expressed on the previously described surface glycoprotein antigens of Mr 200,000, 38,000, and 17,000.

Animals↗
PubMed1986

The recognition of Schistosoma mansoni surface antigens by antibodies from patients infected with S. mansoni and S. haematobium.

Polypeptide surface antigens of Schistosoma mansoni recognized by schistosomiasis patients have been identified and their strain and species specificity investigated. Antibodies from individuals infected with S. mansoni were used in immunoprecipitation assays of 125I-labelled schistosomulum surface antigens. All individuals surveyed from St. Lucia strongly precipitated antigens of approximately Mr 38,000 to 32,000 and 20,000. These antigens were shown by two-dimensional gel electrophoresis to be the same as those recognized by experimentally immunized mice. Although individuals showed a highly heterogeneous response against total polypeptide antigens synthesized in vitro by cell-free translation of adult S. mansoni mRNA, all individuals recognized the same surface antigens. Immunoprecipitation with sera from patients infected with S. mansoni in many different parts of Africa resulted in generally the same antigens being precipitated, although a very high molecular weight antigen(s), not strongly recognized by the St. Lucian sera was also precipitated by most of the African patient sera. One serum from Ghana precipitated the high molecular weight antigen but not the low molecular weight antigens, raising the possibility of the existence of S. mansoni strain(s) exhibiting some diversity in surface antigens. The surface of S. mansoni schistosomula was found to bind strongly antibodies from individuals infected with S. haematobium, demonstrating that most surface antigens are cross-reactive. Immunoprecipitation demonstrated, however, that of the polypeptide surface antigens only the very high molecular weight antigen was recognized by anti-S. haematobium antibodies and that the 38,000 to 32,000 and 20,000 Mr antigens were species-specific. Immunoprecipitation of the polypeptide antigens derived from purified adult surface membranes demonstrated recognition of the same 32,000, 25,000 and 20,000 Mr antigens recognized by chronically infected mice. Again these antigens were found to be species-specific.

Adult↗
PubMed1986

Repetitive DNA as a tool for the identification and comparison of nematode variants: application to Trichinella isolates.

DNA prepared from four isolates of Trichinella was compared by genomic DNA cross-hybridisation, by electrophoresis following restriction endonuclease digestion and by hybridisation studies using a cloned repetitive DNA sequence from T. spiralis. The DNA from T. spiralis, T. nelsoni and T. pseudospiralis isolates was distinct and the interrelationships of these isolates were inferred. In contrast to previous work on T. nativa and T. spiralis, our work suggests that these two isolates are very similar.

Animals↗
PubMed1986

Differentiation of Schistosoma haematobium from related species using cloned ribosomal RNA gene probes.

The ribosomal RNA (rRNA) gene units of Schistosoma mansoni (lateral spined eggs) and six species of schistosomes with terminal spined eggs (S. haematobium, S. curassoni, S. bovis, S. intercalatum, S. margrebowiei and S. mattheei) have been studied. The schistosome rRNA gene unit consists of a regular interspersion of the two genes encoding the large and small rRNA units with two spacers. The large spacer is not transcribed while the small spacer is part of the transcription unit. Variation in the rRNA gene unit of the species studied is demonstrated and takes three forms: First, variation in DNA sequence leads to both reduced homology in the spacer regions between species and loss or gain of restriction sites. Second, variation in the length of the transcribed spacer is demonstrated and DNA insertions of 0.2 kilobases (kb) and 0.1 kb are observed in S. mattheei and S. margrebowiei, respectively. Third, the length of the non-transcribed spacer region varies between species. S. haematobium has a 0.5 kb deletion in this region, while that of S. margrebowiei contains varying numbers of a 0.4 kb DNA insert. These interspecific variations have been shown to be conserved within species. Analysis of the rRNA genes by DNA hybridisation techniques therefore serves as a means of species identification, whereby it is possible to differentiate S. haematobium from other schistosome species with terminal spined eggs. Similarly, S. margrebowiei and S. mattheei may be clearly distinguished, although no major variation has been detected between S. curassoni, S. bovis and S. intercalatum. All these species differ from S. mansoni by the absence of certain restriction sites in the non-transcribed spacer.

Animals↗
PubMed1986

Adult schistosome cDNA libraries as a source of antigens for the study of experimental and human schistosomiasis.

Protective immunity has been demonstrated in experimental schistosomiasis and is also believed to occur in man. It can be mediated by antibodies from infected animals or animals immunized with attenuated organisms. Recombinant Escherichia coli synthesizing antigenic polypeptides from the three principal species of schistosome that infect man, Schistosoma mansoni, S. japonicum and S. haematobium, have been constructed. Libraries of adult worm cDNA were prepared from each species in the expression vector lambda gt 11 and directly screened with antibodies from animals experimentally immunized with S. mansoni and S. japonicum and from humans infected with S. haematobium. The S. mansoni clones have been analysed in greatest detail. At least four different types of clones were identified. All the detected recombinant polypeptide antigens were recognised by antibodies from chronically infected mice and most were also recognised by antibodies from mice immunized with attenuated cercariae and anti-surface membrane antibodies. Clones synthesizing species-specific antigens for both S. mansoni and S. japonicum were identified by simultaneous screening of both libraries. At least three types of S. haematobium clones were identified by screening with human infection serum, most of which were species-specific. All the antigens were in the form of fusion peptides with E. coli beta-galactosidase and their expression was induced by isopropylthiogalactopyranoside. Since known protective monoclonal antibodies recognise highly glycosylated membrane proteins which cannot be identified in the form of nascent polypeptides, the direct identification of polypeptide antigens defined by their reactivity, as reported here, is an essential step in producing reagents by recombinant DNA technology, suitable for vaccination and diagnosis.

Animals↗
PubMed1986

Cloning of a major developmentally regulated gene expressed in mature females of Schistosoma mansoni.

A cDNA library constructed from RNA isolated from adult Schistosoma mansoni has been screened by differential hybridization to identify clones corresponding to genes highly expressed by female worms. Several such cDNAs encoding the same highly abundant mRNA species were identified. Studies with one of these (pSF10) which contained a 500 base pair insert demonstrated that this gene was not expressed in immature females or eggs and encoded a polypeptide of approximately 35 000 daltons. Quantitation of the levels of RNA showed that 10% of the total RNA of female parasites was homologous to pSF10. A single gene corresponding to pSF10 was identified in Southern blotting experiments using adult worm DNA. The cloning of this gene will facilitate study of the molecular and genetic events controlling female schistosome maturation.

Animals↗
PubMed1985

Schistosoma mansoni: antigen preparations which induce antibodies to schistosomula surface antigens.

To determine the easiest method of raising antibodies to antigens exposed on the surface of schistosomula of Schistosoma mansoni, several crude preparations of the parasite were used to immunize mice. Schistosomula released products, whole worm homogenate, and parasite eggs all raised antibodies which bound to the surface of live schistosomula, although the anti-egg antiserum did so less strongly. Anti-schistosomula released products antiserum recognized three schistosomula surface antigens of Mr 15,000, 20,000, and 32,000, anti-whole worm homogenate recognized 20,000, 32,000, and 38,000 Mr surface antigens, and anti-egg recognized a less than 200,000 Mr surface antigen. None of these antigens was recognized when the labeled preparation was immunoprecipitated with its homologous antiserum. When these antisera were used to immunoprecipitate cell free translation products of adult worm RNA, the antischistosomula released products and anti-whole worm homogenate recognized an 11,000 Mr doublet while the anti-egg precipitated 14,000 and 44,000 Mr antigens. Other crude preparations were used to immunize rabbits; Formalin-fixed schistosomula, denuded adult worms, and purified worm tegument all induced antibodies which recognized the 20,000, 32,000, and 38,000 Mr schistosomula surface antigens.

Animals↗
PubMed1985

Schistosoma mansoni: complexity of antigenic and nonantigenic surface polypeptides.

Two-dimensional gel analysis of the surface polypeptides of the schistosomula stage of Schistosoma mansoni resolved a complex pattern of approximately 20 polypeptides. The majority of these were identified as immunogenic since they were immunoprecipitated with antisera from chronically infected mice and from mice vaccinated with irradiated cercariae. However, several major surface polypeptides were not immunoprecipitated by sera from infected or immune mice and were presumed to be nonantigenic.

Animals↗