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Query: UMLS:C0042961 (volvulus)
 4,305 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The existence of immunity to Onchocerca volvulus (Ov) infection is suggested by the presence of uninfected persons in hyperendemic areas. A major barrier to the study of immunity has been the correct identification of putatively immune (PI) subjects. To identify a PI group in a hyperendemic area in Ecuador, clinical and epidemiologic information was combined with a polymerase chain reaction (PCR)-based assay identifying Ov DNA in skin snips and a recombinant antigen-based ELISA. Comparison of immune responses revealed that PI subjects had significantly lower levels of Ov-specific IgG, IgG subclasses, and IgE than infected (INF) subjects. Female subjects were significantly more likely to be PI than male subjects, and INF female subjects had significantly lower levels of Ov-specific IgG, IgG1, and IgG3 than INF male subjects. Thus, the use of molecular-based techniques has helped to define more precisely the PI state in onchocerciasis.
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PMID:Immunity to onchocerciasis: identification of a putatively immune population in a hyperendemic area of Ecuador. 793 Jul 13

Definitive diagnosis of Onchocerca volvulus (Ov) infection requires the identification of the parasite in either the skin or subcutaneous nodules. These parasitologic approaches suffer from poor sensitivity. To assess the efficacy and utility of a polymerase chain reaction (PCR)-based diagnosis for Ov infection, skin snips were examined from 94 persons in an Ov-endemic region of Ecuador, and results were compared in a blinded fashion with those of a PCR assay based on the Onchocerca-specific repetitive DNA sequence, O-150. All 60 patients microfilaria-positive on skin snip examination were positive in the PCR-based assay. In addition, 13 of 34 who were microfilaria-negative by skin snips were positive in the PCR assay. This suggests that the PCR-based assay is significantly more sensitive than current methods and overcomes many deficiencies of parasitologic and serologic methodologies in diagnosing active onchocerciasis.
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PMID:Polymerase chain reaction-based diagnosis of Onchocerca volvulus infection: improved detection of patients with onchocerciasis. 815 53

Eukaryotic transcription factors can be identified and classified according to conserved DNA-binding motifs and conserved regulatory domains. The functional and structural analysis, and the conservation of these genes among metazoans emphasizes the importance of these DNA-binding proteins in development and differentiation. In order to identify genes with common DNA-binding motifs in the genome of Onchocerca volvulus we have cloned a zinc finger encoding gene of the structure C2-H2. Using the Caenorhabditis elegans sex determining tra-1 gene as a probe we have identified two tra-1 related genes in the genome of O. volvulus. The zinc finger region of one of these genes (OvZf1) was subcloned and sequenced. The predicted protein has at least eight consecutive zinc fingers and each finger possesses the characteristic paired cysteine- and histidine residues and the proper spacing of the amino acids between the conserved residues.
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PMID:Identification of a zinc finger encoding gene in Onchocerca volvulus. 825 86

The Dv3-14 gene fragment of Dictyocaulus viviparus is 471 bp, of which about 90% is translated. The calculated molecular mass of the translation product is 15.5 kDa. DNA sequence homologies were found with major sperm proteins (MSPs) from Ascaris suum, Caenorhabditis elegans and Onchocerca volvulus. Within a segment of 62 amino acids the predicted amino acid sequence of Dv3-14 shows 84% homology with an A. suum MSP and 84% homology with a C. elegans MSP. Computer analysis of the protein sequence identified three segments of immunodominant antigenic sites as putative candidates for synthetic peptide antigens. Immunoblotting analysis of the translated product showed that it is adult stage specific, water soluble and not membrane bound and can be demonstrated in the supernatant fluids of cultures from adult worms kept in cell culture medium. The results suggest that the protein encoded by Dv3-14 is a MSP of D. viviparus.
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PMID:The diagnostic antigen encoded by gene fragment Dv3-14: a major sperm protein of Dictyocaulus viviparus. 835 87

Strategies for detection and control of onchocerciasis in Africa have included identification of DNA probes and PCR target sequences for sensitive and specific detection of parasites. To evaluate the applicability of published PCR and DNA probe based methods for the study of onchocerciasis in Sudan, we collected adult O. volvulus from geographically distinct regions of Sudan (700 miles apart), Abu Hamed (northern desert) and Raja (southwestern savannah), and we examined the similarities between Sudanese O. volvulus repeats and published versions of the repeat from West African O. volvulus. Amplification of DNA extracted from the Raja O. volvulus strain predictably generated a ladder of products, multiples of the base 150 bp repeat, as has been reported from West Africa. However, amplification of DNA from the Abu Hamed O. volvulus isolate resulted in a series of doublets. The unexpected DNA fragments thus amplified differed in size from the base 150 bp unit by approximately 50 base pairs and was most clearly visualized at 150-200 base pairs. DNA sequence analysis of the amplified repeats in the isolate of O. volvulus from Abu Hamed revealed a variant of the 150 bp tandem repeat which contained an extra 49 bp. The additional 49 bp contained two short repeats of 21 bp and 10 bp, corresponding to bases 99-119 and 128-137 respectively, of the known 150 bp O. volvulus repeat. This work demonstrates a variant of the O. volvulus 150 bp tandem repeat, which easily distinguishes Raja and Abu Hamed isolates of O. volvulus, and which has potential value for differentiating Abu Hamed strains of O. volvulus from other strains in East Africa.
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PMID:Characterization of a variant tandem repeat from Sudanese Onchocerca volvulus. 836 58

Repeated DNA sequences have been instrumental in the development of DNA probes for many different parasites. Isolation of such DNA probes has generally been accomplished by differential screening of genomic libraries with total genomic DNA preparations. In the current work, a rational design strategy is presented for the development of oligonucleotide probes based upon repeated sequence families. A repeated sequence family present in the genome of Onchocerca parasites, designated O-150, has been amplified from various samples of genomic DNA using PCR. DNA sequence analysis of the resulting PCR products demonstrated that the sequences may be arranged into clusters within which the individual sequences are identical or nearly identical. Differences among the cluster consensus sequences have been exploited to explain the specificities of previously isolated O-150 based probes and to develop two new oligonucleotide probes. One of these probes hybridizes specifically to Onchocerca volvulus O-150 PCR products, while the second hybridizes specifically to O-150 PCR products from the closely related bovine parasite O. ochengi. These oligonucleotide probes have been used to characterize Onchocerca infective larvae isolated from wild caught infected flies in West Africa. Because repeated sequence families are a common feature of most genomes, including those of parasites, this method should be applicable to the rational design of oligonucleotide probes for other parasitic infections.
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PMID:Design of Onchocerca DNA probes based upon analysis of a repeated sequence family. 847 50

Filarial parasites release macromolecules into their environment both in vitro and in vivo. These excretory-secretory products (E-S) have been studied with respect to function, vaccination potential, pathogenicity, and ability to serve as antigen targets for diagnostic tests. We have recently described monoclonal antibody OV-1 which binds to an intermediate filament in E-S and circulating antigens of Onchocerca volvulus. OV-1 also binds to cross-reactive antigens of Brugia malayi. Therefore, OV-1 was used to immunoscreen a B. malayi adult worm cDNA library in an attempt to clone a homologue (BMIF). BMIF is a 1664-bp full-length transcript which codes for 505 amino acids. BMIF has 95% sequence homology at the amino-acid level to OV1CF, an O. volvulus intermediate filament that was also selected with OV-1, and 75% homology to Ascaris intermediate filament A. Southern blot analysis suggests that BMIF is confined to a single location in the genomic DNA of B. malayi. Antibodies raised to BMIF identified native antigens in immunoblots of B. malayi adult worms, infective larvae and adult E-S. In addition, the antibody also bound to a 60-kDa antigen in immunoblots of poly(ethylene glycol)-precipitated immune complexes in sera from B. malayi infected patients. Localization studies showed that the antigen encoded by BMIF is present in the hypodermis, developing embryos and muscle of adult B. malayi. These studies show that BMIF is an E-S product of B. malayi adult worms which is detectable in sera from patients with brugian filariasis.
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PMID:Molecular characterization of a Brugia malayi intermediate filament protein which is an excretory-secretory product of adult worms. 857 31

A recently developed polymerase chain reaction (PCR)-based assay is significantly more sensitive than current methods for diagnosing Onchocerca volvulus infection, and it overcomes many difficulties in identifying active onchocerciasis. Since chemotherapy is widely used to treat onchocerciasis, the utility of PCR in assessing responses to treatment and in predicting recrudescence is important. Twenty-eight patients who had skin snips positive for microfilariae (Mf) were studied 120 days after receiving amocarzine, when each was negative for Mf: 16 (57%) were positive for O. volvulus DNA in the PCR-based assay. Of these, 14 (88%) were Mf positive when reassessed parasitologically on day 240, and all were Mf positive on day 365. Equally important was the finding that 12 patients had cleared both Mf and Mf DNA; only 1 was Mf positive at day 240. This suggest that the PCR-based assay provides a sensitive means assessing infection status after macrofilaricidal chemotherapy and is an early predictor of persons likely to have a recurrence of Mf.
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PMID:Polymerase chain reaction-based assessment after macrofilaricidal therapy in Onchocerca volvulus infection. 862 52

An Onchocerca volvulus expression library was differentially screened to identify a molecular marker distinguishing sowda (lichenified onchodermatitis) from other onchocerciasis forms. One clone, PG3, was recognized by pooled sera from patients with sowda, but not by pooled sera from patients with generalized onchocerciasis; it was not recognized by sera from patients with lymphatic filariasis or other helminth infections. The DNA of PG3 hybridized strongly with O. volvulus Eco RI-digested DNA, but not with DNA from Brugia spp., Trichinella spp., and humans. A weak reaction was observed with DNA from O. gibsoni and Acanthocheilonema viteae. The PG3 DNA sequence showed a high homology with both human and nematode collagens. Confirmation of the collagen-like nature of the sowda-specific PG3 product was obtained by amino terminal sequencing of the PG3 expression product, as well as by demonstrating its susceptibility to collagenase digestion. The characteristic recognition of the O. volvulus collagen specified by clone PG3 was confirmed by measuring antibody levels to the expressed product in individual sowda and generalized onchocerciasis sera, respectively. Identification of a nematode collagen antigen mainly recognized in sowda patients raises the possibility that this extreme form of dermatitis might arise through cross-reactivity between anti-O. volvulus collagen antibodies and human collagen. However, a relationship between the PG3 recognition by antibodies and the sowda pathogenesis could not be demonstrated.
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PMID:Identification of Onchocerca volvulus collagen as an antigen mainly recognized by antibodies in chronic hyper-reactive onchodermatitis (sowda). 864 4

A polymerase chain reaction (PCR) of a 150-bp tandem repeat of Onchocerca volvulus (O-150) combined with Southern-blot hybridization to species-specific DNA probes was employed for DNA detection. O-150 was amplified from parasites originating from Uganda, Benin, Cameroon, Liberia, Ghana, Burkina Faso, Mali, and Zaire and was successfully hybridized to digoxigenin-labeled oligonucleotides. To investigate the sensitivity of the PCR, 2 skin biopsies were taken from each of 227 persons from Uganda with proven O. volvulus infections but with low microfilaria (mf) densities due to ivermectin treatment. One biopsy was tested by PCR and the other was digested using collagenase to assess the total number of mf. The PCR revealed 76.2% of the samples to be positive, and the collagenase method showed that 78.9% were positive, indicating similar sensitivity for the two methods. It is probable that for both techniques the biopsy must contain at least one live mf or fragments of a dead mf. In this study, no free or circulating O. volvulus DNA could be detected in skin biopsies by PCR.
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PMID:Sensitivity of a polymerase chain reaction-based assay to detect Onchocerca volvulus DNA in skin biopsies. 873 77


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