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

The immune response after early exposure to or infection with Onchocerca volvulus was investigated in an autochthonous focus caused by the migration of infected persons to a previously unaffected area in Ecuador. Peripheral blood mononuclear cell (PBMC) proliferative and cytokine responses (interferon [IFN]-gamma and interleukin [IL]-5) to filarial antigens were measured in 14 subjects with serologic evidence of exposure and in 7 subjects with evidence of dermal microfilarial DNA and were compared with responses in 43 subjects with chronic O. volvulus infections. PBMC proliferative and cytokine responses (IFN-gamma and IL-5) to parasite antigens were elevated in the early exposure/infection group, compared with those in the chronic infection group. Addition of an IL-10-neutralizing antibody to filaria antigen-stimulated cultures resulted in significantly elevated proliferative responses in the chronic infection group. The findings suggest that early exposure and early parasite patency are associated with a vigorous cellular response, but, as infections become chronic, the cellular response becomes down-regulated, partly through an IL-10-dependent mechanism.
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PMID:Early human infection with Onchocerca volvulus is associated with an enhanced parasite-specific cellular immune response. 1134 16

Prior studies have shown that Onchocerca volvulus DNA can be detected in skin snips and in black flies after polymerase chain reaction (PCR) with primers specific for repeated "O-150" DNA sequences. We have adapted a paper chromatography hybridization assay (PCHA) to detect amplified O-150 DNA and compared this method to two established methods, namely agarose gel electrophoresis (AGE) and hybridization enzyme-linked immunosorbent assay (ELISA). The minimum amounts of purified O-150 DNA detected by PCHA, AGE, and ELISA were 5, 10, and 2 ng, respectively. The three methods had similar estimated sensitivities for detecting O. volvulus DNA amplified from skin snips from African subjects with onchocerciasis (88%, 84%, and 91%, respectively). No false positive results were observed with skin snips from uninfected control subjects. The paper chromatography hybridization assay detects PCR products in 30 minutes without electricity or special equipment. This technology brings DNA detection a step closer to widespread use in field settings.
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PMID:Paper chromatography hybridization: a rapid method for detection of Onchocerca volvulus DNA amplified by PCR. 1135 2

The complete mitochondrial genome sequences were determined for two species of human hookworms, Ancylostoma duodenale (13,721 bp) and Necator americanus (13,604 bp). The circular hookworm genomes are amongst the smallest reported to date for any metazoan organism. Their relatively small size relates mainly to a reduced length in the AT-rich region. Both hookworm genomes encode 12 protein, two ribosomal RNA and 22 transfer RNA genes, but lack the ATP synthetase subunit 8 gene, which is consistent with three other species of Secernentea studied to date. All genes are transcribed in the same direction and have a nucleotide composition high in A and T, but low in G and C. The AT bias had a significant effect on both the codon usage pattern and amino acid composition of proteins. For both hookworm species, genes were arranged in the same order as for Caenorhabditis elegans, except for the presence of a non-coding region between genes nad3 and nad5. In A. duodenale, this non-coding region is predicted to form a stem-and-loop structure which is not present in N. americanus. The mitochondrial genome structure for both hookworms differs from Ascaris suum only in the location of the AT-rich region, whereas there are substantial differences when compared with Onchocerca volvulus, including four gene or gene-block translocations and the positions of some transfer RNA genes and the AT-rich region. Based on genome organisation and amino acid sequence identity, A. duodenale and N. americanus were more closely related to C. elegans than to A. suum or O. volvulus (all secernentean nematodes), consistent with a previous phylogenetic study using ribosomal DNA sequence data. Determination of the complete mitochondrial genome sequences for two human hookworms (the first members of the order Strongylida ever sequenced) provides a foundation for studying the systematics, population genetics and ecology of these and other nematodes of socio-economic importance.
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PMID:The mitochondrial genomes of the human hookworms, Ancylostoma duodenale and Necator americanus (Nematoda: Secernentea). 1181 91

Treatment of onchocerciasis with diethylcarbamazine (DEC) or ivermectin is associated with a posttreatment reaction characterized by fever, tachycardia, hypotension, lymphadenopathy, and pruritus. To investigate the role of the Wolbachia bacterial endosymbiont of Onchocerca volvulus in these reactions, serum samples collected before and after treatment with either anthelmintic were assessed for evidence of Wolbachia DNA. By use of real-time quantitative polymerase chain reaction, Wolbachia DNA was detected in both groups-with significantly higher levels in those who received DEC (P <.0001). In the ivermectin group, there was a significant correlation between levels of bacterial DNA and serum tumor necrosis factor-alpha (P =.013). Peak DNA levels correlated with reaction scores (P =.048). Significant correlations were also seen between Wolbachia DNA and the antibacterial peptides calprotectin (P =.021) and calgranulin B (P <.0001). These findings support a role for Wolbachia products in mediating the inflammatory responses seen following treatment of onchocerciasis and suggest new targets for modulating these reactions.
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PMID:Bacterial endosymbionts of Onchocerca volvulus in the pathogenesis of posttreatment reactions. 1192 Feb 98

The geophysics of the north Yemen, associating a north-south directed mountainous fish bone (rising in more of 2,000 meters), to numerous rivers or "wadis" is convenient to the development of simulium shelters, main vectors for cutaneous filariasis to Onchocerca sp. Following several missions of bio-clinical and epidemiological evaluations in neighbouring villages of wadis, it has been possible to study different clinical aspects: one reminding the classical african onchocerciasis with generalized and diffused dermatitis, and, on an other hand, a hyperreactive dermatitis on one side of the body and associated with a collateral lymphatic ganglion. This disease is well known for local populations as "aswad" meaning "black" or "sowda". Clinically whatever the studied focus, coexists the two types of onchodermatitis (uni or bilateral). Yhe sowda patients are proportionally less numerous than those touched by the generalized type. Frequent eye lesions of the West African onchocerciasis are not found in sowda cases. In classical optical microscopy, microfilaria is morphologically indifferenciable between sowda and onchocerciasis clinical aspects. Skin snips were carried out on patients of both groups. Identification of microfilaria by molecular biology through the study of the DNA genome was done out of 5 skin snips. Microfilaria was kept dry between laminas and the DNA extracted from rehydrated microfilaria. DNA was intensified with specific primers of Onchocerca type (O150PCR). This phase was followed by hybridisation of amplification products by PCR to specific stains: OVS-2 for Onchocerca volvulus species, OCH for Onchocerca ochengi, PFS1 and PSS1-BT respectively for the forest strain and the savannah strain of Onchocerca volvulus as described previously. We can distinguish 2 kinds of answers based on the clinical origin of the snip-tests: the first one concern 3 patients with numerous dermal microfilariae but without any clinical sowda and corresponding to microfilaria O. volvulus type but different from the forest or savannah strains found in sub-Saharan Africa. The second one corresponds to 2 patients with less than 5 microfilaria in their snip-test. They show the typical clinical picture of sowda. They are identified as microfilaria type Onchocerca but they do not belong to species volvulus, or to species ochengi. It seems quite probable that the clinical picture of sowda be the result of developing onchocerciasis of animal origin and not identified as to day. The ivermectin, therapeutic of choice for African onchocerciasis in annual unique cure seems less effective in the coverage of sowda. In that case rehearsal of cures every 3 months would be necessary for mass campaigns to limit the transmission of this filariasis.
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PMID:[Human onchocerciasis and "sowda" in the Republic of Yemen]. 1197 66

We developed a polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA) for the detection of Onchocerca volvulus DNA. To standardize the PCR and to avoid false-negative results, an internal control DNA was co-amplified by the same set of primers. We differentiated the wild-type PCR product of the O-150 DNA sequence from the internal control by specific DNA probes. Detection of biotinylated PCR products by DNA probes was performed by ELISA to quantify the PCR product or by DNA Detection Test Strips as a rapid field technique. The methods were evaluated on skin biopsies from individuals living in an area endemic for O. volvulus in Uganda, but with low microfilaria densities because of ivermectin treatment. Microfilaria density was assessed by a single skin snip and a second skin snip was examined by PCR. Among 69 samples from microfilaria carriers, 47 (68%) were positive by ELISA and 55 (80%) by test strip detection of PCR products. When 39 samples of microfilaria-negative individuals from the same area were tested, 10 (27%) were positive by ELISA and 12 (31%) by test strips. None of the 19 samples obtained from persons living in an area not endemic for O. volvulus but endemic for Mansonella streptocerca was positive in either test. Although the ELISA is theoretically more sensitive than the test strips for the detection of PCR products, examination of field samples revealed that the test strip method had a higher operational sensitivity and was more convenient to perform. Thus, the DNA Detection Test Strips are a rapid and low-tech tool for identification of PCR products in laboratories of countries endemic for onchocerciasis.
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PMID:An internal control for the detection of Onchocerca volvulus DNA by PCR-ELISA and rapid detection of specific PCR products by DNA Detection Test Strips. 1203 Oct 75

T helper cell-recognized epitopes were determined in chitinase of Onchocerca volvulus, a vaccine candidate protein. The proliferation of splenic T cells of mice immunized with recombinant protein was tested with a library of chitinase-peptides of 16 amino acids with termini overlapping by 12 amino acids, and a library of "designer peptides", i.e. sequences identified with three epitope-predicting algorithms. Fourteen epitope-bearing stretches were identified with the peptides of the overlapping library. Testing of the designer peptides partially confirmed these data and revealed additional epitopes. Five clusters of epitopes were identified for the creation of peptide or minigene DNA vaccines with good potency and potential range of MHC allele presentation.
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PMID:Identification of T helper cell-recognized epitopes in the chitinase of the filarial nematode Onchocerca volvulus. 1239 96

BACKGROUND: Many filarial nematodes harbour Wolbachia endobacteria. These endobacteria are transmitted vertically from one generation to the next. In several filarial species that have been studied to date they are obligatory symbionts of their hosts. Elimination of the endobacteria by antibiotics interrupts the embryogenesis and hence the production of microfilariae. The medical implication of this being that the use of doxycycline for the treatment of human onchocerciasis and bancroftian filariasis leads to elimination of the Wolbachia and hence sterilisation of the female worms. Wolbachia play a role in the immunopathology of patients and may contribute to side effects seen after antifilarial chemotherapy. In several studies Wolbachia were not observed in Loa loa. Since these results have been doubted, and because of the medical significance, several independent methods were applied to search for Wolbachia in L. loa. METHODS: Loa loa and Onchocerca volvulus were studied by electron microscopy, histology with silver staining, and immunohistology using antibodies against WSP, Wolbachia aspartate aminotransferase, and heat shock protein 60. The results achieved with L. loa and O. volvulus were compared. Searching for Wolbachia, genes were amplified by PCR coding for the bacterial 16S rDNA, the FTSZ cell division protein, and WSP. RESULTS: No Wolbachia endobacteria were discovered by immunohistology in 13 male and 14 female L. loa worms and in numerous L. loa microfilariae. In contrast, endobacteria were found in large numbers in O. volvulus and 14 other filaria species. No intracellular bacteria were seen in electron micrographs of oocytes and young morulae of L. loa in contrast to O. volvulus. In agreement with these results, Wolbachia DNA was not detected by PCR in three male and six female L. loa worms and in two microfilariae samples of L. loa. CONCLUSIONS: Loa loa do not harbour obligatory symbiotic Wolbachia endobacteria in essential numbers to enable their efficient vertical transmission or to play a role in production of microfilariae. Exclusively, the filariae cause the immunopathology of loiasis is patients and the adverse side effects after antifilarial chemotherapy. Doxycycline cannot be used to cure loiais but it probably does not represent a risk for L. loa patients when administered to patients with co-infections of onchocerciasis.
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PMID:Obligatory symbiotic Wolbachia endobacteria are absent from Loa loa. 1280 20

BACKGROUND: The majority of filarial nematode species are host to Wolbachia bacterial endosymbionts, although a few including Acanthocheilonema viteae, Onchocerca flexuosa and Setaria equina have been shown to be free of infection. Comparisons of species with and without symbionts can provide important information on the role of Wolbachia symbiosis in the biology of the nematode hosts and the contribution of the bacteria to the development of disease. Previous studies by electron microscopy and PCR have failed to detect intracellular bacterial infection in Loa loa. Here we use molecular and immunohistological techniques to confirm this finding. METHODS: We have used a combination of PCR amplification of bacterial genes (16S ribosomal DNA [rDNA], ftsZ and Wolbachia surface protein [WSP]) on samples of L. loa adults, third-stage larvae (L3) and microfilariae (mf) and immunohistology on L. loa adults and mf derived from human volunteers to determine the presence or absence of Wolbachia endosymbionts. Samples used in the PCR analysis included 5 adult female worms, 4 adult male worms, 5 mf samples and 2 samples of L3. The quality and purity of nematode DNA was tested by PCR amplification of nematode 5S rDNA and with diagnostic primers from the target species and used to confirm the absence of contamination from Onchocerca sp., Mansonella perstans, M. streptocerca and Wuchereria bancrofti. Immunohistology was carried out by light and electron microscopy on L. loa adults and mf and sections were probed with rabbit antibodies raised to recombinant Brugia malayi Wolbachia WSP. Samples from nematodes known to be infected with Wolbachia (O. volvulus, O. ochengi, Litomosoides sigmodontis and B. malayi) were used as positive controls and A. viteae as a negative control. RESULTS: Single PCR analysis using primer sets for the bacterial genes 16S rDNA, ftsZ, and WSP were negative for all DNA samples from L. loa. Positive PCR reactions were obtained from DNA samples derived from species known to be infected with Wolbachia, which confirmed the suitability of the primers and PCR conditions. The quality and purity of nematode DNA samples was verified by PCR amplification of 5S rDNA and with nematode diagnostic primers. Additional analysis by 'long PCR' failed to produce any further evidence for Wolbachia symbiosis. Immunohistology of L. loa adults and mf confirmed the results of the PCR with no evidence for Wolbachia symbiosis. CONCLUSION: DNA analysis and immunohistology provided no evidence for Wolbachia symbiosis in L. loa.
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PMID:Evidence against Wolbachia symbiosis in Loa loa. 1281 46

The sugar trehalose is claimed to be important in the physiology of nematodes where it may function in sugar transport, energy storage and protection against environmental stresses. In this study we investigated the role of trehalose metabolism in nematodes, using Caenorhabditis elegans as a model, and also identified complementary DNA clones putatively encoding genes involved in trehalose pathways in filarial nematodes. In C. elegans two putative trehalose-6-phosphate synthase (tps) genes encode the enzymes that catalyse trehalose synthesis and five putative trehalase (tre) genes encode enzymes catalysing hydrolysis of the sugar. We showed by RT-PCR or Northern analysis that each of these genes is expressed as mRNA at all stages of the C. elegans life cycle. Database searches and sequencing of expressed sequence tag clones revealed that at least one tps gene and two tre genes are expressed in the filarial nematode Brugia malayi, while one tps gene and at least one tre gene were identified for Onchocerca volvulus. We used the feeding method of RNA interference in C. elegans to knock down temporarily the expression of each of the tps and tre genes. Semiquantitative RT-PCR analysis confirmed that expression of each gene was silenced by RNA interference. We did not observe an obvious phenotype for any of the genes silenced individually but gas-chromatographic analysis showed >90% decline in trehalose levels when both tps genes were targeted simultaneously. This decline in trehalose content did not affect viability or development of the nematodes.
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PMID:Trehalose metabolism genes in Caenorhabditis elegans and filarial nematodes. 1367 35


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