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PubMed1991

Filariasis in Gongola State Nigeria. I: Clinical and parasitological studies in Mutum-Biyu district.

A total of 2552 persons living in 9 villages along the Benue river valley, Mutum-Biyu district of Gongola State, Nigeria were examined between October and December 1989 for filariasis. It is the first time a filariasis survey will be carried out in this State. 276 (10.8%) had Wuchereria bancrofti, 50 (2.0%) had Loa loa, 281 (11.0%) were positive for Mansonella perstans while 12 (0.5%) were positive for Onchocerca volvulus. Villages located near the Benue river had higher prevalence rates than those further away. Dermatitis and hydrocoele were common and clinical manifestations were associated with parasite types. Clinical symptoms without microfilaremia and microfilaremia without clinical symptoms were also observed. The study will fill the gap in our knowledge of filariasis in this part of Nigeria.

Adolescent↗
PubMed1990

IgG4 subclass antibody serology for onchocerciasis.

Antibodies to phosphorylcholine and carbohydrate determinants responsible for much of the cross-reactivity among nematodes are subclass restricted in humans and absent in the IgG4 subclass. Total IgG and IgG4 antibody responses to Onchocerca volvulus were examined by enzyme immunoassay and by immunoblot. Significant background IgG reactivity was detected in both assays in US control sera and sera from patients with intestinal nematode infections, but background reactivity was negligible in the IgG4 assays. IgG4 antibodies were detected by enzyme immunoassay in 17 of 18 Nigerian onchocerciasis serum samples and in 2 of 9 endemic control serum samples. Cross-reactive IgG4 antibodies were present in serum pools from patients infected with other filariae. IgG4 antibodies recognized a restricted subset of O. volvulus antigens in immunoblots relative to IgG. These results confirm the previously reported enhanced specificity of IgG4 antibody assays for filariasis and extend the observation to include onchocerciasis. Whereas IgG4 subclass antibody serology is more specific than measurement of total IgG antibodies for onchocerciasis, cross-reactivity among filariae limits the utility of this approach.

Animals↗
PubMedDate not supplied

Monoclonal antibodies as investigative tools in onchocerciasis.

The development of monoclonal antibodies against parasites can facilitate analysis of host-parasite interactions and can lead to the identification and characterization of antigens that induce protective responses in the immunized host. As diagnostic reagents for human and bovine onchocerciasis, monoclonal antibodies have been used to detect circulating antigens. So far only complex antigens have been used to generate monoclonal antibodies against filarial parasites. The use of such heterogeneous immunogens may result in interference or even in inhibition of the response to the desired parasite antigen(s). Epitopes that are similar or identical to determinants on host molecules or that are components of other infectious agents serve to complicate the generation and selection of monoclonal antibodies against Onchocerca volvulus antigens, and cross-reactivity can be due to monoclonal antibodies reacting with phosphorylcholine, which is present in many preparations of helminth antigens. Because of the host-dependent immunogenicity of filarial agents, reagents should be screened carefully for species specificity by use of a set of different helminth antigens. It is hoped that active collaboration among all investigators engaged in filariasis research will facilitate resolution of such difficulties.

Animals↗
PubMed2005

Antibiotic chemotherapy of onchocerciasis: in a bovine model, killing of adult parasites requires a sustained depletion of endosymbiotic bacteria (Wolbachia species).

Development of a drug lethal to adult Onchocerca volvulus (i.e., macrofilaricide) is a research priority for the control of human onchocerciasis. Using bovine O. ochengi infections, we investigated the effects of oxytetracycline administered in a short intensive regimen (SIR; 10 mg/kg daily for 14 days), compared with a prolonged intermittent regimen (PIR; 20 mg/kg monthly for 6 months) or a combination of both (COM), on the viability of adult worms and their endosymbiotic bacteria (Wolbachia species). The long-term treatments eliminated >80% (COM) or >60% (PIR) of adult female worms (P<.001), and the COM regimen effected a sustained depletion of Wolbachia organisms. Conversely, SIR was not macrofilaricidal and only transiently depleted Wolbachia densities, which repopulated worm tissues by 24 weeks after treatment. These results unequivocally demonstrate the macrofilaricidal potential of tetracyclines against Onchocerca infection and suggest that intermittent, protracted administration will be more effective than continuous shorter term treatment.

Animals↗
PubMed1991

Suppression of human lymphocyte responses to specific and non-specific stimuli in human onchocerciasis.

Characterization of in vitro lymphocyte responsiveness was performed on selected groups of onchocerciasis patients from Sudan and Sierra Leone. These patients manifested a very broad range of clinical signs and showed widely divergent parasite infection intensities. Lymphocyte proliferative responses to soluble Onchocerca volvulus antigen (sAg) were poor in infected persons; mitogen and PPD responses were maintained in the normal range in one group of patients from southwestern Sudan, but were profoundly depressed in a group from N.E. Sudan. Proliferative responses and interferon-gamma (INF-gamma) secretion were very significantly depressed in the presence of live microfilariae of O. volvulus or secretions/excretions (S/E) from microfilariae (mf) or from female, but not male, adult parasites. Lymphocyte responses were maintained near normal when exogenous IL-2 was added to these cultures. The results indicate that O. volvulus infection and its clinical consequences are not consistently associated with systemic deficits in immune responsiveness. However, suppression of lymphocyte reactivity by mf and S/E in vitro suggests that direct parasite intervention in host cell responses could be taking place in vivo, perhaps at the local microenvironment level; mediated by effects on cytokine production.

Animals↗
PubMed2004

Pathogenesis and host responses in human onchocerciasis: impact of Onchocerca filariae and Wolbachia endobacteria.

Onchocerca volvulus is a tissue-invasive parasitic nematode causing skin and eye pathology in human onchocerciasis. The filariae habour abundant intracellular Wolbachia bacteria, now recognised as obligatory symbionts, and therefore emerging as a novel target for chemotherapy. Recent research demonstrates that both the filariae and endobacteria contribute to the pathogenesis of onchocerciasis, and molecules have been identified that promote inflammatory or counter-inflammatory immune mechanisms, divert the host's immune response or procure evasion of the parasite.

Animals↗
PubMed1987

Brugia malayi: recombinant antigens expressed by genomic DNA clones.

A Brugia malayi genomic DNA expression library was screened with rabbit antiserum generated against live infective larvae and 33 clones were identified. Five randomly selected clones were characterized in detail by Western blot, DNA and RNA analyses. The fusion proteins produced by each of these recombinant DNA clones are expressed by different genomic sequences. A profile of antigenic cross-reactivities of all 33 recombinant clones was compiled using a battery of antisera, including sera from humans infected with B. malayi. A high percentage of clones were cross-reactive with antisera against the filarial parasites B. pahangi, Dirofilaria immitis, and Onchocerca volvulus. We have made a preliminary identification of three categories of recombinant clones encoding (1) antigens that were cross-reactive with some or all antisera tested, (2) antigens that were specific to the Brugia genus, and (3) antigens that appeared to be specific to B. malayi. These recombinant antigens are candidates for further studies in filarial immunoprophylaxis and diagnosis.

Animals↗
PubMed1990

Ocular onchocerciasis and intensity of infection in the community. III. West African rainforest foci of the vector Simulium sanctipauli.

The community pattern of ocular onchocerciasis is described for 11 villages from the forest area in Côte d'Ivoire where S. sanctipauli is the princial vector. An analytical method is applied which relates indices of ocular onchocerciasis with the Community Microfilarial Load (CMFL) and compares the results with the ocular onchocerciasis pattern found in the West African savanna. In spite of high transmission levels as estimated by entomological indices, the CMFLs were relatively low which complicated the characterization of the ocular disease pattern. Nevertheless, it could be shown that ocular onchocerciasis is less severe in the Sanctipauli forest than in the savanna, even after correction for differences in CMFL. The prevalence of onchocercal eye lesions and blindness were low and advanced sclerosing keratitis was completely absent. The differences are explained by presuming strain differences of the parasite Onchocerca volvulus. For given CMFLs the mean microfilarial loads in the eye were significantly lower than in the savanna which suggests that the parasite strain in the Sanctipauli forest is less invasive to the eye. Ocular microfilarial loads were too low to determine if the parasite is also less pathogenic to the eye, as has been concluded previously for foci of S. yahense, but this possibility cannot be excluded.

Animals↗
PubMed1987

Humoral immune responses in human onchocerciasis: detection of serum antibodies in early infections.

Sera of children (aged 1-15 years) living in a hyperendemic onchocerciasis area (Mali) were tested for antibodies by an enzyme-linked immunosorbent assay (ELISA) and a radioallergosorbent test (RAST), with an extract of adult Onchocerca volvulus as antigen. Serological results were related to age (equivalent to time of residence in the endemic area) and to parasitological findings (detection of skin microfilariae). This longitudinal study (over three years) allowed us to follow early antibody responses in exposed children with no parasitological or clinical evidence of infection and in children who became microfilaria-positive. Serum antibodies against O. volvulus could be detected one to three years before skin microfilariae. RAST, which detected circulating immunoglobulin E (IgE) antibodies, was more sensitive than ELISA in prepatent infections and gave more positive results for exposed but parasitologically negative individuals than did ELISA. During patent infection, IgE antibody levels tended to decrease in about half those infected, whereas in most children non-IgE antibodies showed no significant changes.

Adolescent↗
PubMed1990

The identification of an Onchocerca-specific recombinant antigen containing a T cell epitope.

Recombinant Onchocerca volvulus Ag have been derived from expression libraries and examined for their ability to stimulate PBMC from patients infected with O. volvulus. Ten clones producing recombinant Ag were selected and plaque purified; lysogens were produced and found to express beta-galactosidase fusion proteins ranging in molecular mass from 115 to 138 kDa. When ammonium sulfate-precipitated lysates of these recombinant phage clones were examined for their ability to stimulate PBMC from a patient with onchocerciasis, all 10 recombinants produced stimulation above that to nonrecombinant phage. When individual fusion proteins, affinity purified on anti-beta-galactosidase linked to agarose, were used to stimulate PBMC from patients with onchocerciasis, only one of the recombinant Ag induced PBMC proliferation (stimulation index greater than 4) above that to Ag from nonrecombinant phage. Characterization of the DNA coding for this Ag showed it to be 1.2 kb in length with a small (90 bp) open reading frame; furthermore, it appears to be Onchocerca specific (on genomic dot blots) and single copy. Using overlapping peptides encompassing the entire open reading frame, one T cell epitope has been localized.

Amino Acid Sequence↗
PubMed1990

A human Ro/SS-A autoantigen is the homologue of calreticulin and is highly homologous with onchocercal RAL-1 antigen and an aplysia "memory molecule".

The Ro/SS-A (Ro) autoantigens consist of at least four immunologically distinct proteins which are recognized by autoantibodies typically found in sera from patients with primary Sjogren's syndrome and in subsets of patients with lupus erythematosus. We recently isolated a 1.9-kb human cDNA clone which encodes one of these Ro autoantigens. Synthetic oligonucleotides corresponding to the human Ro sequence were used to amplify the homologous gene from a murine B cell cDNA library using the polymerase chain reaction. The mouse cDNA-encoded amino acid sequence was found to be 94% homologous to the human Ro sequence and is 100% homologous to murine calreticulin, a high affinity calcium-binding protein which resides in the endoplasmic and sarcoplasmic reticulum. The amino acid sequence of rabbit calreticulin is 92% homologous to both murine calreticulin and human Ro. Onchocerca volvulus and Drosophila melanogaster also have molecules that are highly homologous to human Ro. In addition, human Ro has a molecular mass, isoelectric point, and significant amino acid sequence similar to the Aplysia californica snail neuronal protein 407. These homologies suggest that this Ro protein has a very basic cellular function(s) which may in part involve calcium binding.

Amino Acid Sequence↗
PubMed1990

Humoral autoimmune response against S-antigen and IRBP in ocular onchocerciasis.

Autoimmune mechanisms are thought to play a role in the pathogenesis of the chorioretinal changes in ocular onchocerciasis. In this study, the involvement of autoimmunity against retinal antigens in developing chorioretinitis was investigated. Serum levels of autoantibodies, directed against human S-antigen and interphotoreceptor retinoid-binding protein (IRBP), were determined in patients with onchocerciasis (n = 46) and endemic controls (n = 38) from Sierra Leone with the use of an enzyme immunoassay. In both groups high levels of anti-human S-antigen and IRBP antibodies were detected. No relationship could be demonstrated between the antiretinal antibody level and the occurrence of chorioretinitis in onchocerciasis. The levels of both anti-human S-antigen and IRBP antibodies were significantly higher in patients with onchocerciasis compared with endemic controls (P less than 0.001). Cross-reactivity of antiretinal antibodies with parasitic antigens could not be demonstrated as a possible explanation for the higher levels in patients with onchocerciasis. No correlation was found between the levels of antibodies of different classes against the crude Onchocerca volvulus, the egg antigen, or the microfilariae and the antiretinal antibody levels. Furthermore, in a panel of 13 different monoclonal antibodies directed against O. volvulus, only one showed a slight anti-human IRBP reactivity and none reacted with S-antigen. The immune response against the two retinal antigens investigated was not specific for onchocerciasis because high antibody levels were also found in patients with Bancroftian filariasis from Papua, New Guinea, and Surinam.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

A monoclonal antibody-based immunodiagnostic assay for onchocerciasis.

Five murine monoclonal antibodies raised against Onchocerca volvulus cuticular extracts and termed MOVs (1-4 and 6) were selected based on reactivity with O. volvulus cryosections, and non-reactivity with cryosections of human skin and/or nodular tissue. Two others MOVs 5 and 7 reacted with both. Using the peroxidase-anti- peroxidase (PAP) histochemical method, the target epitopes of MOV 1 were located in the cuticle's basal and cortical layers, those of MOV 2 in the cortical layer; whilst MOV 3-7 stained the basal layer. A sandwich ELISA was then developed. The trapping polyclonal antibody was raised in rabbits utilising the same antigens as for preparation of the MOVs. Once captured on microtiter plates, target antigens were identified by the sequential binding of a MOV, followed by a goat anti-mouse globulin/peroxidase or alkaline phosphatase conjugate that catalysed a colorimetric reaction in the presence of appropriate substrates. In this system, MOV 1 emerged as the most specific and potent reagent capable of recognizing antigens of Onchocerca sp. with a minimal detection limit of 78 ng per test. MOV 1, failed to react with extracts of Loa Loa, Ascaris lumbricoides and Ascaris suum in the test. The developed assay relied on the use of MOV 1, required only 1 ml of urine or 0.05 ml serum. About 97.8% of the 47 urines and 50% of the 20 sera from patients studied gave positive results. Only 1 (3%) of 32 control urines and up to 80% of the 10 control sera studied tested positive, suggesting urine as a better specimen source.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1976

The intervals between the blood-meals of man-biting Simulium damnosum (Diptera: Simuliidae).

Six marking-recapture experiments were carried out with Simulium damnosum in the Cameroon Republic, five in the rain-forest and one in the Sudan-savanna zone. Adult flies were marked by applying a small spot of oil paint to the mesonotum while they were engorging with blood on the legs of volunteers infected with Onchocerca volvulus microfilariae. Catches of wild flies were carried out for 12-13 days after the first day of marking, and all marked flies recaptured were examined. Some of the flies recaptured on days 0, 1 and 2 were nulliparous and had probably been disturbed by the application of the paint before they had completed their blood-meal. The frequency distribution of recaptured marked parous flies returning for their "second" blood-meal rose to a peak early on day 4, but more flies returned earlier,three days after taking a blood-meal, than later on day 5. After day 5, the numbers of recaptured flies were too low to demonstrate any peaks corresponding to "third" and later blood-meals. The longest surviving fly was recaptured 10 days after marking. Twenty-six percent of the flies recaptured on days 3 and 4 contained developing O. volvulus larvae three-five days old, which had presumably been ingested as microfilariae during the blood-meal taken on day 0. Infective larvae first appeared in flies returning late on day 6, and the highest percentage of infective flies occurred on day 7. Infective larvae were found in recaptured flies until day 10, the last day on which marked flies were recovered. Of 929 flies marked on the Sudan-savanna experiment, three (0-32%) flies were recaptured. Two returned on day 4 and one on day 6.

Animals↗
PubMed1987

Polyamine metabolism in filarial worms.

The human and animal filarial parasites Onchocerca volvulus, Dirofilaria immitis, Brugia patei and Litomosoides carinii contained low levels of putrescine but much higher levels of spermidine and spermine as estimated by ion-pair high pressure liquid chromatography; N-acetylated polyamines were present only in minute amounts. Enzyme activities of ornithine decarboxylase (EC 4.1.1.17) and arginine decarboxylase (EC 4.1.1.19), respectively, were not detectable. Experiments carried out with O. volvulus and D. immitis demonstrated the uptake and bioconversion of labeled polyamines. There is evidence for the existence of a complete reverse pathway generating putrescine from spermidine and spermine, respectively, in both worms. N-Acetylating enzyme activities were detected in 100,000 X g preparations of homogenates from D. immitis which were capable to acetylate putrescine, spermidine and spermine. Long term incubation of the worms in the presence of labeled polyamines resulted in the excretion of putrescine and N-acetylputrescine.

Animals↗
PubMed1999

Effects of an Onchocerca-derived cysteine protease inhibitor on microfilariae in their simuliid vector.

A recombinant cysteine protease inhibitor, onchocystatin of the parasitic nematode Onchocerca volvulus, was tested for its role in microfilarial development in the simuliid vector. Onchocystatin was found to be present in female adults and skin microfilariae of the bovine parasite O. ochengi, the closest relative of O. volvulus. In addition the inhibitor could be detected as an excretory-secretory (E-S) product of the microfilariae. Co-injection of onchocystatin and the O. ochengi microfilariae into the surrogate vector Simulium ornatum s.l. significantly enhanced the recovery rates of the parasite within 24 h into the infection (P > 0.001). The findings suggest a possible role of onchocystatin in the evasion by the parasite of the immune response of its vector.

Animals↗
PubMed1983

Sowda--onchocerciasis in north Yemen: a clinicopathologic study of 18 patients.

Sowda is an unusual form of onchocerciasis in Yemenites that differs from African onchocerciasis. Clinical and pathological studies were performed on 18 patients in Yemen Arab Republic (North Yemen). Biopsies of skin and lymph nodes were taken, and then processed at the Armed Forces Institute of Pathology, Washington, D.C. The most striking clinical features were swollen, darkened, pruritic, papular skin changes that were usually limited to one leg, more rarely to one arm, and large soft regional lymph nodes. Dermal changes were deeper and more diffuse than in African onchocerciasis, with many large fibroblasts and plasma cells. Microfilariae of Onchocerca volvulus were much rarer in skin from Yemenites with sowda. When patients were treated with diethylcarbamazine, the dermatitis became suddenly worse as the microfilariae degenerated and provoked acute inflammation. The dermatitis decreased after several days of treatment. Enlarged lymph nodes from sowda have shown follicular hyperplasia, in contrast to follicular atrophy and perivascular fibrosis that are characteristic of lymph nodes from cases of African onchocerciasis. Cell-mediated and humoral immunity may be more active in sowda than in African onchocerciasis.

Adolescent↗
PubMed1979

Electron microscopical studies on onchocerciasis. III. The onchocerca-nodule.

Six onchocerca-nodules from five Liberian patients were examined by electron microscopy. The bulk of cells in the centre of the nodules consists of lymphocytes and macrophages. The lymphocytes can be observed in various stages of differentiation. A major part of the macrophages shows degenerative changes with decrease of lysosomes and increase of fatty vacuoles. Near the worms epithelioid cells and giant cells can be found. Other cells in the nodule include polymorphonuclear neutrophils, eosinophils, plasma cells, and mast cells. Adult Onchocerca volvulus show the basic nematode body plan. The cuticle is subdivided into cortex and two layers with differently arranged fibrillar structures. The characteristics of the hypodermal cells are best seen in the lateral chords, in the interchordal regions the hypodermis is flattened by a muscle layer. The intestine typically contains pigment granules, the cells of the epithelium have folds of their cell membranes forming a basal labyrinth. The uterus consists of two tubes in which the development of the microfilariae from the early embryonic forms to the mature stages is examined.

Adult↗