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PubMed1991

Ivermectin uptake and distribution in the plasma and tissue of Sudanese and Mexican patients infected with Onchocerca volvulus.

Ten Sudanese patients with Onchocerca volvulus infection were treated with a single oral dose of 150 micrograms/kg of ivermectin. Plasma samples were collected before treatment, 0.5, 1, 3, 4, 6, 12 hours and 1, 2, 3, 7, and 30 days. Four patients were selected for nodulectomies and skin biopsies at 6, 18 and 30 hours and 3 days post treatment. Using these samples O. volvulus worm fragments were dissected free of host nodular tissues for ivermectin extraction. Ivermectin was present in the nodular tissue at 6 hr and persisted for 3 days. It was also detected in an individual worm tissue extract at a concentration similar to the nodule, but in subcutaneous fascial tissue higher concentrations were sometimes found. Ivermectin was detected by radioimmunoassay in the plasma of all patients at 1 hr and peak concentrations were reached in an average of 5.6 hr. The drug persisted at detectable levels for 7 days in 70% of the studied patients. Plasma samples were also collected from 16 treated Mexican onchocerciasis patients before ivermectin treatment and 4 hr treatment and from six individuals who served as controls. The Mexican patients had concentrations of ivermectin in their plasma similar to those in the Sudanese patients.

Humans↗

PubMed1998

[Onchocerca volvulus--a rare cause of a mass in children].

The parasite Onchocerca volvulus is well-known in its endemic areas in South and Central America and West Africa. It is transmitted to man by simulium flies and causes systemic infection with skin, lymphatic and ophthalmic manifestations and can cause blindness (river blindness). Treatment with Ivermectin is effective but sometimes there is need for surgical intervention to prevent or treat complications. We describe an 11-year-old girl, a new immigrant from Ethiopia, who had a firm mass in her left thigh, caused by Onchocerca volvulus. It was completely excised. This is a very rare condition in Israel, which must be considered in patients coming from endemic areas.

Animals↗

PubMed1991

Uptake of chloroquine by Onchocerca volvulus in vivo and in vitro.

Patients infected with Onchocerca volvulus in the Cayapa River focus in north-east Ecuador were given 500 mg chloroquine diphosphate (CQ) orally prior to nodulectomy. The concentrations of CQ were determined in parasite fragments and host tissue dissected from the nodules, in skin overlying the nodules, and in plasma at 3, 4, 7, and 24 hours after dosing. Onchocerca volvulus took up CQ rapidly, in some cases accumulating the drug to concentrations of over 600 pmol mg-1 worm tissue by three hours, and maintaining similar concentrations through 24 hours. These amounts were markedly higher than peak concentrations in plasma (3.16 pmol microliters-1) and in host tissues (78 pmol mgm-1) and skin (up to 93 pmol mg-1). In vitro uptake of CQ by females of O. volvulus was greater under alkaline conditions (pH 8.4) than at pH 6.8 and 7.4. Uptake reached equilibrium after one to two hours, with final concentrations being approximately 10 times lower than those reached in vivo. Inhibitory effects of chloroquine and its major metabolite desethylchloroquine on the motility of O. volvulus and other filariae have been observed previously in vitro; whether or not the drug had adverse effects on adult parasites in vivo was not determined in these experiments. However, the results illustrate the accessibility of O. volvulus to blood borne agents in vivo, and the potential importance of pharmacodynamic characteristics in the search for new macrofilaricidal agents.

Animals↗

PubMedDate not supplied

A DNA sequence specific for forest form Onchocerca volvulus.

Onchocerciasis, or river blindness, is caused by infection with Onchocerca volvulus, a filarial parasite which infects about 40 million people in Africa and Latin America. Epidemiological, clinical, entomological and serological studies of African onchocerciasis led to the hypothesis that Onchocerca volvulus exists in different forms in the forest and savannah. It is uncertain if these differences are due to genetic differences within O. volvulus itself, or to epigenetic factors, such as differences in the host populations. To date no basic biochemical differences between the forest and savannah populations of O. volvulus has been found, although isoenzyme studies have shown that differences in allele frequency between forest and savannah populations exist. Here we describe the isolation of a DNA sequence that seems to be specific for the forest form of O. volvulus, the first indication of a basic genetic difference between the savannah and forest forms.

Base Sequence↗

PubMed1994

Molecular cloning of an Onchocerca volvulus extracellular Cu-Zn superoxide dismutase.

Onchocerca volvulus, a human parasitic nematode, is the third leading cause of preventable blindness worldwide. This study describes the molecular cloning of a novel superoxide dismutase (SOD) from the parasite. This putative O. volvulus extracellular SOD (OvEcSOD) is 628 nucleotides (nt) long, including a 22-nt 5' spliced leader (SL1) and a portion encoding an N-terminal hydrophobic 42-amino-acid signal peptide. The remainder of the cDNA shares 71% identity with an O. volvulus cytosolic SOD sequence and is 3 nt longer. All residues involved in metal ion binding, active site formation, folding, and dimer formation in SODs are conserved. Data indicate the OvEcSOD and O. volvulus cytosolic SOD are separate gene products and that the OvEcSOD appears to possess the characteristics of a membrane-bound or secreted enzyme which may be involved in the parasite defense against phagocyte-generated reactive oxygen species.

Amino Acid Sequence↗

PubMed1993

Cryopreservation of infective larvae of Onchocerca volvulus (Filarioidea: Onchocercidae).

Infective larvae (L3) of Onchocerca volvulus were procured in Liberia, West Africa, in the natural black fly vector, Simulium yahense. A cryobiological technique was developed to preserve L3 of O. volvulus that were fully viable after thawing. Larvae were treated before cooling with 4 cryoprotective compounds. Three compounds, dimethyl sulfoxide (DMSO), glycerol, and ethylene glycol, were prepared with distilled water. The fourth compound was DMSO prepared in different concentrations with 0.25 M sucrose. The treatment with DMSO + 0.25 M sucrose cryoprotectant resulted in the highest survival of infective larvae. Five cooling rates between 0.5 C/min and 20.0 C/min were applied. The highest survival of L3 was with the cooling rate of 1.0 C/min. Two-step cooling of L3 was applied. In the first step, L3's were frozen to 5 levels from -10.0 C to -20.0 C, -30.0 C, -40.0 C, -60 C, and -80.0 C, and in the second step, larvae were transferred into liquid nitrogen at -196 C for rapid cooling and storage. The survival was the highest when larvae were cooled to approximately -40 C prior to transfer into liquid nitrogen. Slow, gradual, and rapid thawing procedures were applied. The survival was the highest in rapid warming.

Animals↗

PubMed1990

Use of monoclonal antibodies for the characterization of Onchocerca volvulus antigens.

In order to identify Onchocerca volvulus antigens that could be considered as either diagnostic and/or immunoprophylactic, mouse monoclonal antibodies were produced against O. volvulus soluble antigens. Three were selected on the basis of their staining patterns in an indirect fluorescent antibody assay carried out on cryosections of adult O. volvulus. The first monoclonal antibody (K1-159) recognized a cuticular antigen which appeared in IFA to be restricted to the genus Onchocerca. However, neither Western blotting, nor the immunoprecipitation experiments performed on radiolabelled O. volvulus soluble antigen allowed detection of the corresponding antigen(s). The second monoclonal antibody (K1-126) bound to the muscle cells of adults. A 30,000 Mr antigen was detected by Western blot analysis of adult O. volvulus homogenate. This antigen was also recognised by sera from infected patients and corresponding antigenic determinants were detected in extracts of O. gutturosa, Acanthocheilonema viteae and Ascaris suum, but not in Brugia malayi. The third monoclonal antibody (K1-143) recognized egg shells and the surface of adult worms. The target epitope was not species specific and could be found in O. gutturosa, A. viteae, B. malayi and A. suum. The electrophoretic analysis of I-125 labelled soluble antigens and radiolabelled surface antigens of adult O. volvulus, showed numerous antigens (molecular weights ranging from 30,000 to 120,000 Mr) precipitated by K1-143. In an inhibition radioimmunoassay, K1-143 allowed the detection of corresponding antibodies in 79% of the O. volvulus patient sera tested.

Animals↗

PubMed1999

Induction of specific cell-mediated immunity in mice by oral immunization with Salmonella expressing Onchocerca volvulus glutathione S-transferase.

Cellular and humoral immune responses of mice to Onchocerca volvulus glutathione S-transferase (OvGST) presented via in vivo expression in attenuated Salmonella typhimurium were examined and compared with the same antigen administered by subcutaneous injection with Freund's adjuvant. After infection with recombinant S. typhimurium, maximal numbers of bacteria were recovered from the mesenteric lymph nodes and spleens during the second week postinfection. By weeks 3-4, bacteria were absent from these tissues. Splenocytes from mice infected with S. typhimurium expressing OvGST showed significant and specific proliferative responses to OvGST, whereas the non-recombinant S. typhimurium controls and those which received the antigen by subcutaneous injection with Freund's adjuvant did not. Mice infected with recombinant S. typhimurium had elevated IFN-gamma levels over non-recombinant S. typhimurium and placebo controls. but IL-4 and IL-5 levels were low and did not differ significantly between these groups. Antibody responses to OvGST antigen expressed by a recombinant Salmonella vaccine or delivered in a purified form with Freund's adjuvant were moderate to high. These data suggest that Salmonella can be used as a vaccine delivery vector that induces specific cellular and humoral immune responses to Onchocerca volvulus antigens. This is the first report to describe the successful application of a filarial antigen in a live-vector delivery system as well as the first recombinant based filarial vaccine to elicit a cellular immune response similar to that described for putative immune endemics.

Administration, Oral↗

PubMed1989

Specific detection of human antibodies to Onchocerca volvulus.

Specific diagnosis of antibodies to Onchocerca was achieved through (1) the construction of direct and indirect ELISA systems, and (2) restricting ELISA assays to the IgG4 class. The direct ELISA was based on the isolation of a surface derived, low molecular weight surface antigen preparation containing two main antigens (M. wt. 16.2 and 12.8 kDA) as defined by Western blot analysis. The direct ELISA system detected antibodies in children of six years old, and may therefore be applicable to detecting reinvasion in OCP areas of Onchocerca volvulus control. The indirect ELISA system was a competitive binding ELISA-based assay using a monoclonal antibody recognising two Onchocerca components (M. wts. 15.6 and 25.9) on a Western blot. The direct and indirect ELISA systems were similarly specific and sensitive when evaluated in a preliminary survey. The direct ELISA system yielded a specificity and sensitivity of: 100% and 100% respectively, using Mexican endemic and Mexican intestinal nematode infection sera as positive and negative controls respectively: 91% and 96% respectively, using Venezuelan endemic and Venezuelan Mansonella ozzardi infection sera as positive and negative controls, respectively: 87% and 93% respectively, using African endemic and Papuan (New Guinea) Wuchereria bancrofti infection sera as positive and negative controls respectively: 93% and 93% respectively, using African endemic and Indian W. bancrofti infection sera as positive and negative controls respectively. Similar specificity and sensitivity levels were obtained when the same comparisons were made using the indirect (inhibition) ELISA assay. These values may be contrasted with the currently used PBS extract of O. volvulus which yielded specificities of less than 10% in all the above comparisons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1996

Immunohistological studies on an Onchocerca volvulus ankyrin (EI).

The distribution of an Onchocerca volvulus ankyrin, designated E1, was studied in different O. volvulus stages and other helminths by immunohistochemistry using rabbit antibodies raised against the recombinant E1 protein. In adult O. volvulus the protein designated E1 was localized to the extracellular clefts as well as to the cytoplasm adjacent to the cell membrane in the area of the basal labyrinth in hypodermis, intestine and uterus and to a lesser extent in oviduct and vas deferens. Neuronal cell bodies were also labelled. No labelling of the basal laminae, muscles or epithelia of ovary or testis was observed. Detection of the E1 protein was associated with embryonic development. Germ cells and early morulae showed no reaction; labelling was first seen in late morulae, corresponding to the stage of gastrulation, and increased in the following embryonic stages. In microfilariae the nerve ring and the cephalic space, which represents the anterior nerve-enriched portion of the body, were labelled. In third-stage larvae of O. volvulus labelling was associated with the hypodermis, and in those of Anisakis sp. the cytoplasm adjacent to the membrane of the excretory gland cell and the basal labyrinth of the hypodermis were labelled. Following anthelminthic treatment a disruption of the labelling pattern of the E1 protein was observed in adult O. volvulus with leakage of the protein into neighbouring areas. Damage to the worm was associated with reduction and finally loss of E1 protein labelling. No E1 protein was detected in dead adult worms, embryos or microfilariae. Labelling of the same organs was observed in 8 other Onchocerca species and in several other nematodes, but no reaction was seen in trematodes. The results indicate that the EI protein is associated with neuronal structures of O. volvulus, that its presence is developmentally regulated and that it has cross-reactive homologues in other nematodes. The results suggest that E1 is a functional protein. It may be useful for the assessment of parasite damage and death as well as in the characterization of the filarial nervous system.

Animals↗

PubMed1986

Identification of non-cross-reacting antigens of Onchocerca volvulus with lymphatic filariasis serum pools.

Onchocerca volvulus proteins labelled with 125I were immunoprecipitated with onchocerciasis and lymphatic filariasis human serum pools in order to differentiate between cross-reacting and non-cross-reacting antigens. Analysis of the immunoprecipitates by two-dimensional gel electrophoresis revealed that all high molecular weight (Mr) O. volvulus antigens cross-reacted with the lymphatic filariasis serum pools. We observed, however, that at least 8 O. volvulus antigens were specifically immunoprecipitated only by the onchocerciasis serum pools, with Mr ranging from 20,000 up to 43,000 Daltons. These results suggest that the lower Mr O. volvulus antigens are more species specific than the other antigens. The significance of these findings for the immunodiagnosis of onchocerciasis is discussed.

Adult↗

PubMed1996

Protective immunity induced by vaccination with Onchocerca volvulus tropomyosin in rodents.

A cDNA clone of Onchocerca volvulus, designated MOv14, and encoding 136 amino-acid residues from the C-terminus of O. volvulus tropomyosin, was evaluated as a protective immunogen in two complimentary rodent models of onchocerciasis. Vaccination of BALB/c mice with the recombinant fusion of MOv14 coupled to Maltose-Binding Protein (MBP) induced significant reductions (48-62%) in the recovery of Onchocerca lienalis microfilariae from the skin, compared to control groups immunized with MBP alone. The predominant antibody response generated to MOv14 by vaccination was of IgG1. Following a similar vaccination protocol in Mongolian jirds, two independent experiments demonstrated that 16 weeks after infection with Acanthocheilonema viteae there was a 46% reduction in the recovery of adult worms in vaccinated animals compared to control groups. Antibodies generated by vaccination recognized a product released during culture of A. viteae infective larvae which migrated at a distinct molecular mass from native tropomyosin from somatic tissues.

Animals↗

PubMed1985

Calcification in adult Onchocerca volvulus.

Calcified worm fragments of adult Onchocerca volvulus from patients in West Africa were collected for a chemical analysis. The material contained predominantly calcium carbonate. Some results of investigations on the occurrence of calcified worms in untreated populations are reported on. Relations between the numbers of old parasites and those of calcified worms are discussed. The significance of possible resorption of calcified worm fragments for the interpretation of the effects of drug trials or other control measures are mentioned.

Animals↗

PubMed1984

Identification of an antigen of Onchocerca volvulus of possible diagnostic use.

Adult Onchocerca volvulus worms obtained by enzyme digestion from nodules of infected Mexicans were radio-isotope labelled by the chloramine-T or Bolton-Hunter methods. No antigenic determinants were detected in extracts of worms labelled by the chloramine-T method but 3 antigens were detected in extracts of the Bolton-Hunter labelled worms. Two were present in such small amounts that it was impractical to investigate them further, but a major component of mol. wt 20 kDa was purified by gel filtration and used in a serological survey of inhabitants of villages in Southern Mexico. Using the 20 kDa antigen, which is superficially located on both sexes of O. volvulus, sera from both non-endemic and endemic regions were analysed by radio-immunoprecipitation of this antigen. In Southern Mexico, the average sensitivity of the test was 92%, and the specificity 98%. Whilst the 20 kDa antigen did not detect antibodies in the sera of Trinidadians infected with Wuncheria bancrofti or Mansonella ozzardi, this antigen detected high levels of antibodies in Indians exposed to W. bancrofti.

Animals↗

PubMed1980

Life span and distribution of Onchocerca volvulus microfilariae in mice.

Microfilariae of Onchocerca volvulus obtained from onchocercomas were inoculated subcutaneously into the inguinal region of mice. Microfilariae disseminated rapidly, invading the tail and lungs within 1 hr and the ears within 3 hr postinoculation. During the early period of infection microfilariae appeared in the eyes, ears, viscera, pelt, carcass, and tail; later, the microfilariae tended to accumulate in the tail. Liver microfilariae were recovered up to 12 wk postinoculation. Intraperitoneal inoculation and subcutaneous inoculation into the inguinal region resulted in the concentration of microfilariae in the tail, whereas inoculation into the scalp caused microfilarial accumulation in the ears.

Animals↗

PubMed1994

Phosphoprotein patterns in Onchocerca volvulus developmental stages.

Living females and microfilariae of Onchocerca volvulus incubated in culture medium containing [32P]orthophosphate were observed to phosphorylate their proteins rapidly. Patterns of phosphoproteins in extracts from these labelled parasites were compared after two dimensional electrophoresis and autoradiography. Protein extracts from eggs, microfilariae and adult females of O. volvulus were phosphorylated in the presence of [gamma-32P]ATP, magnesium acetate, and added cyclic AMP-dependent protein kinase or the endogenous protein kinase present in the extracts. Patterns of phosphoproteins were compared after separation by single and two-dimensional gel electrophoresis followed by autoradiography. Common phosphopeptide bands were observed when phosphorylated extracts from adult females, microfilariae and eggs were compared. However, extracts from eggs displayed unique phosphorylated polypeptides of M(r) 30,000 and 34,000 that were absent from the extracts from microfilariae. Furthermore, two phosphorylated polypeptides of M(r) 47,000 and 76,000 were detected in extracts from microfilariae but not from eggs. These results indicate that O. volvulus parasites may phosphorylate different proteins at different stages of their development.

Animals↗

PubMed1988

Seasonality of adult black flies and Onchocerca volvulus transmission in Guatemala.

Transmission of Onchocerca volvulus, principally by Simulium ochraceum, was studied over a 14-month period in the Atitlán region of Guatemala. Semimonthly catches of black flies were made on human volunteers at 4 localities with different prevalences of human onchocerciasis. Host-seeking activity of S. ochraceum reached its greatest magnitude in the early dry season (October-January) but then declined rapidly and was lowest during the late dry season (February-May). The frequency of O. volvulus larvae in parous host-seeking S. ochraceum also varied seasonally, and this variation was most pronounced for third stage larvae. At a hyperendemic locality, the highest frequency of this larval stage occurred during the February-March period (0.0142 in 1979 and 0.0095 in 1980). From June-January, the frequency of third stage larvae in S. ochraceum was less than 0.003. The frequency of early first stage larvae exhibited the least seasonal variation, ranging from 0.0354 in August-September to 0.0628 in April-May. The transmission rate of O. volvulus by S. ochraceum also varied seasonally. At the same hyperendemic locality, infective biting density of S. ochraceum attained its greatest magnitude in February-March. The survival rate of female S. ochraceum from one gonotrophic cycle to the next was estimated from the ratio of flies with early first stage larvae to those with infective stage larvae. These rates varied seasonally and ranged from 0.2132 to 0.3974, with the highest rates occurring in the late dry season.

Animals↗

PubMed1998

T cell responses in coinfection with Onchocerca volvulus and the human immunodeficiency virus type 1.

Onchocerca volvulus and the human immunodeficiency virus (HIV) are two immunocompromising infectious agents of major public health concern in Uganda. To examine the effect of coinfection with O. volvulus and HIV on cellular immune responses, lymphocyte proliferative responses and cytokine production of peripheral blood mononuclear cells (PBMC) from persons infected with O. volvulus with and without HIV type 1 infection were compared. Proliferation of PBMC to PHA and tuberculin (PPD) in coinfection was less (P = 0.08, P < 0.01) than in O. volvulus infection. O. volvulus extract stimulated lymphocyte proliferation in microfilaria-negative and HIV-negative O. volvulus infection while only an inconspicuous response was observed in microfilaria-negative coinfection. After stimulation of PBMC with PPD, the production of interferon-gamma (IFN-gamma), interleukin (IL)-4 and IL-5-demonstrated in O. volvulus infection-were reduced in coinfection with HIV (P < 0.01). While both groups failed to produce IFN-gamma in response to O. volvulus extract, only O. volvulus infected persons generated pronounced IL-5 and low IL-4 levels (0.01 > P = 0.02). The cellular immune responses in coinfection suggested an HIV-related lack of specific reactivity to O. volvulus antigen and impairment of IL-4 and IL-5 production in addition to the lack of IFN-gamma response on antigenic stimulation.

Adult↗