Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0042961 (volvulus)
 4,305 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two clones, pOA1 and pOA5, have been isolated from a genomic DNA library prepared from pools of Onchocerca armillata adults in the plasmid vector pUC12. In dot-blot hybridisations, these two clones do not cross-hybridise significantly with total genomic DNA from O. volvulus, O. gutturosa, O. ochengi, O. gibsoni, O. lienalis, bovine, human, Culicoides nubeculosus, Simulium species or Brugia pahangi, but do hybridise with as little as 100 pg of DNA from two separate geographic isolates of O. armillata. The sequence of pOA1 and pOA5 has been determined and found to contain a repetitive DNA sequence 147 bp in length. These clones can be used as specific and sensitive DNA probes for the identification of O. armillata capable of identifying a single L3 larva.
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PMID:Cloning and characterization of a species-specific repetitive DNA sequence from Onchocerca armillata. 318 12

Characterization of the immune response to Onchocerca volvulus is important for the diagnosis, control and understanding of the disease it causes. The antibody response to surface, secreted and somatic antigens of the worm has therefore been examined at an individual immunoglobulin (Ig) class level, by using a panel of different human sera. Onchocerca-specific antigens tend to be of low molecular mass and preferentially recognized by IgG4 and IgE. There is considerable cross-reaction between O. volvulus and O. gibsoni, so that the latter may be an alternative source of material for use in diagnosis. A surface-enriched fraction of low molecular mass appears to be a most promising diagnostic tool. Amongst somatic antigens, two were uniquely recognized by IgG3 antibodies in sera from sowda patients, thereby providing a molecular correlate for a recognized pathological condition. Improved diagnosis is needed for detecting infection in both humans and the vector. Our target for detection in humans is a continuously released, nonimmunogenic product, which is ideally stage and parasite specific. The excretions of adult worms do contain components not recognized by antibodies in infected serum, but we cannot rule out that these are of host, rather than parasite origin. Excretions of Litomosoides carinii contain both host and parasite molecules and, in addition, stage-specific and sex-specific components. Unfortunately, however, the rate of production of excretions varies during the life of L. carinii. This finding may be relevant to the detection of Onchocerca excretions if they are produced at a similarly uneven rate. Finally, for detecting infective larvae in the vectors, we are currently screening a genomic library of O. volvulus for an appropriate probe. To date, one DNA sequence has been cloned that shows promising specificity.
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PMID:Onchocerca antigens in protection, diagnosis and pathology. 329 54

A thorough study of parasite antigens is a prerequisite for control programmes based on protection by vaccination, accurate serodiagnosis and perhaps immune modulation to diminish pathological sequelae. Stage specific surface secreted and somatic antigens may be of particular value in proceeding towards these goals. The design of vaccines is most appropriately focused on surface antigens. With respect to pathology, certain antigens must stimulate humoral and, or cellular immune responses which are responsible for the undesirable immunopathologic consequences of the disease. The ultimate objective, therefore, is identification of those particular antigens followed by appropriate down regulation of the immune system in order to delete such potentially harmful immunological reactions. The relevant illustration presented in this context is an interesting correlation between one particular clinical condition of onchocerciasis ("sowda") and the serological response, defined both in terms of the parasite antigen and an immunoglobulin class restricted antibody response. Current parasitological methods of diagnosis consistently underestimate parasite prevalence. Failure to detect low level patent infections incurs the risk of having a reservoir capable of perpetuating infections. There is, then, an urgent requirement for accurate serodiagnosis, to be used in association with, and for the evaluation of, drug treatment and vector elimination in parasite control programmes. Given the high sensitivity of current immunoassay technology, the only bar to establishing the necessary immunological tests is the choice of suitably specific antibody-antigen systems. Once these are identified, a combination of recombinant nucleic acid biochemistry and hybridoma technology should provide the necessary reagents for inexpensive, robust and specific diagnostic tests. In addition, it may not be many years before the ubiquitous RIA and ELISA technology gives way to the newly developing biosensor systems. Finally, given the sensitivity and specificity of today's nucleic acid hybridization techniques, we may soon expect to see specific identification of infective larvae in their vectors of this, a cloned DNA probe specific for Onchocerca volvulus, and with potential for the detection of infective larvae in blackflies is described.
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PMID:Nematode antigens in protection, diagnosis and pathology. 332 66

Blackflies are vectors for Onchocerca volvulus, a filarial parasite that infects tens of millions of people in Africa and Latin America. Different species of the insect vectors, varying greatly in their ability to transmit the infection, may populate overlapping geographical regions and be morphologically similar. A rapid and reliable method for distinguishing among blackfly species is presently not available. We have isolated cloned DNAs coding for repetitive sequences that can distinguish between two species of North American blackflies, Simulium pictipes and Simulium vittatum. These DNAs do not cross hybridize to three African blackfly species. The assay is very sensitive, less than 1/1000th of the amount of DNA in a single fly being sufficient for detection with a radioactive probe. Diagnosis with nonradioactive probes by a procedure that is amenable for use in the field was also demonstrated.
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PMID:Identification of species-specific DNA sequences in North American blackflies. 338 25

A genomic library of a savanna isolate of Onchocerca volvulus was screened to detect recombinant plasmids containing highly repeated DNA sequences of this parasite. Four recombinant plasmids were identified which hybridized specifically to Onchocerca DNA, but not to DNA from humans, black flies, Brugia malayi, B. pahangi, or Wuchereria bancrofti. The recombinant plasmids had a low level of homology to Dirofilaria immitis. All recombinant plasmids contain related DNA sequences based on Southern hybridization analysis. Sequences related to these recombinant plasmids are present in different geographic isolates of O. volvulus and O. ochengi, an animal parasite. Two of the recombinant plasmids contain sequences also found in O. lienalis. One recombinant plasmid, puOvs3, has been characterized in detail, including DNA sequence determination. Radiolabeled puOvs3 is able to detect 100 pg of genomic DNA isolated from O. volvulus worms from both savanna and forest regions. It can differentiate O. volvulus from O. ochengi by Southern blot analysis.
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PMID:Characterization of an Onchocerca-specific DNA clone from Onchocerca volvulus. 366 30

Adaptive resonance theory (ART) describes a class of artificial neural network architectures that act as classification tools which self-organize, work in realtime, and require no retraining to classify novel sequences. We have adapted ART networks to provide support to scientists attempting to categorize tandem repeat DNA fragments from Onchocerca volvulus. In this approach, sequences of DNA fragments are presented to multiple ART-based networks which are linked together into two (or more) tiers; the first provides coarse sequence classification while the subsequent tiers refine the classifications as needed. The overall rating of the resulting classification of fragments is measured using statistical techniques based on those introduced by Zimmerman, et al. (1994) to validate results from traditional phylogenetic analysis. Tests of the Hierarchical ART-based Classification Network, or HABclass network, indicate its value as a fast, easy-to-use classification tool which adapts to new data without retraining on previously classified data.
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PMID:DNA sequence analysis using hierarchical ART-based Classification Networks. 758 98

The manganese-containing superoxide dismutase (MnSOD) is a major component of the cellular defence mechanisms against the toxic effects of the superoxide radical. Within the framework of studies on anti-oxidant enzymes and their protective role in the human parasitic nematode Onchocerca volvulus, sequences encoding the MnSOD were isolated and examined in this study. Degenerate primers were designed based upon conserved regions of MnSOD sequences from other organisms, and were used in PCR on reverse-transcribed O. volvulus total RNA and genomic DNA to identify partial cDNA and genomic DNA fragments encoding the O. volvulus MnSOD (OvMnSOD). The genomic DNA PCR product was used to screen an O. volvulus adult worm lambda unizap II cDNA library and the nucleotide sequence of the longest clone determined. The complete 5'-end of the OvMnSOD cDNA was obtained using the rapid amplification of cDNA ends (RACE) procedure with O. volvulus total RNA and was found to possess a spliced leader sequence at the 5'-terminus. The deduced primary sequence encodes a 25 kDa protein, which has the conserved residues required for enzyme activity and metal binding. The 24 N-terminal amino acids encoded by the OvMnSOD cDNA comprise a putative mitochondrial transit peptide. The OvMnSOD gene was also isolated from an O. volvulus adult worm lambda fix II genomic library, a restriction map was constructed and the nucleotide sequence determined. The OvMnSOD gene was found to possess five exons and four introns with consensus splice-site junctions. Potential regulatory elements were identified in the 5' genomic flanking sequence. Southern-blot analysis with total worm genomic DNA indicates a single-copy gene, with a restriction pattern consistent with that of the isolated gene.
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PMID:Characterization of the manganese superoxide dismutase cDNA and gene from the human parasite Onchocerca volvulus. 777 25

Immunity to Onchocerca volvulus (Ov) infection is suggested by the presence of putatively immune (PI) subjects in a region of Ecuador in which Ov is endemic. PI subjects were identified by traditional diagnostic methods combined with a polymerase chain reaction-based assay for Ov DNA in skin snips. Responses of peripheral blood mononuclear cells (PBMC) from the PI group (n = 16) were compared with those of persons with active infection (microfiladermic [MF] subjects; n = 51). PBMC of PI subjects proliferated significantly more to Ov antigen (OvAg; P < .009) than did PBMC of MF persons but less to streptolysin-O (P < .001). Cytokine analysis of PBMC culture supernatants revealed that PI subjects (n = 11) produced significantly more interferon-gamma to OvAg than did those in the MF group (n = 18; P = .018), less interleukin (IL)-5 to nonparasite antigen (P = .003) and mitogen (P = .012), and less IL-10 spontaneously (P = .016). Thus, immunity to Ov may in part be mediated by an antigen-specific Th1-type response.
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PMID:Immunity to onchocerciasis: putative immune persons produce a Th1-like response to Onchocerca volvulus. 787 12

The development of polymerase chain reaction-based methods using strain- and species-specific DNA probes for Onchocerca volvulus has permitted classification of individual parasites from every stage of the parasite's life cycle. This technology has been applied on a large scale basis by Onchocerciasis Control Program (OCP) in West Africa. The primary objective of the OCP in using the DNA probes was to obtain accurate estimates of the annual transmission potential of the blinding strain of O. volvulus. The DNA probe classification of larvae collected throughout the OCP area demonstrated that larvae of less pathogenic strains of O. volvulus and other filarial parasites carried by Simulium damnosum s.l. have resulted in a significant overestimation of the annual transmission potential for blinding onchocerciasis. This effect is particularly pronounced along the southern border of the OCP, where the blinding and less pathogenic strains of O. volvulus coexist, and in the north of the control area, where animal parasites, particularly O. ochengi, may even predominate. A second objective of the OCP in applying the DNA probe technology was to determine the distribution of blinding and less pathogenic O. volvulus in infected individuals along the southern border of the control area. Results obtained from these studies have generally confirmed the distribution pattern established by previous epidemiologic studies. In addition, DNA probe classifications have demonstrated that in areas where the blinding and less pathogenic strains of O. volvulus coexist, a single individual may simultaneously be infected with both strains of the parasite.
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PMID:DNA probe-based classification of Simulium damnosum s. l.-borne and human-derived filarial parasites in the onchocerciasis control program area. 798 61

Human infections with the tissue nematode Onchocerca volvulus result in a variety of clinical conditions that possibly include protective immunity. In a West African area hyperendemic for human onchocerciasis, 120 residents were classified according to clinical and laboratory findings as presenting with generalized onchocerciasis, localized onchocerciasis, or as being putatively immune. The three groups differed in the distribution of HLA-D variants as determined by DNA typing. The most pronounced differences were found among alleles of the DQ loci. The haplotype DQA1*0501-DQB1*0301 was significantly more frequent among putatively immune individuals than among patients with generalized or localized disease. Conversely, DQA1*0101-DQB1*0501 and, independently, the allele DQB1*0201 were more frequent in generalized disease than in localized disease or putative immunity. In these correlations, the frequencies of allelic variants were in localized disease intermediate to those of the two other groups. The only distinct association found with localized disease was that of the DP allele DPB1*0402. The findings indicate that HLA-D variants influence the course of O. volvulus infection and help to define a state that may reflect protective immunity.
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PMID:HLA-D alleles associated with generalized disease, localized disease, and putative immunity in Onchocerca volvulus infection. 805 11


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