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PubMed2004

The Secreted Larval Acidic Proteins (SLAPs) of Onchocerca spp. are encoded by orthologues of the alt gene family of Brugia malayi and have host protective potential.

Onchocerca volvulus is a tissue-dwelling, vector-borne nematode parasite of humans and the causative agent of onchocerciasis, or 'River Blindness'. Resistance to infection is associated with immune responses to the infective, third-stage (L3) larvae. The antigens of greatest interest for their vaccine potential are surface and secreted molecules. We have previously identified a family of Secreted Larval Acidic Proteins (SLAPs) from the L3 larvae of O. volvulus by biosynthetic labelling. Here, we provide further characterisation of these molecules following cloning and expression of the corresponding cDNAs. Using protein sequencing, we show that SLAPs are members of the alt gene family, first described in the lymphatic filarial parasite, Brugia malayi. Ov-ALT-1 and Ov-ALT-2 correspond with 20 and 18kDa SLAPs. Both proteins are highly acidic and related by sequence, differing chiefly in an 8-amino acid deletion from Ov-ALT-2. By immunochemistry, we confirm that Ov-ALTs are highly stage-specific, being expressed exclusively in late L2 and L3 larvae during growth in the vector. They are synthesised and stored in the glandular oesophagus. Secretion is triggered by the resumption of development in the definitive host and occurs via the pseudocoelom and cuticle. Serological responses in humans to recombinant Ov-ALT-1 indicate that the level of IgG production may be governed by the force of transmission but does not overtly reflect infection status. Immunisation of mice with recombinant Ov-ALT-1 resulted in a modest level of protection against challenge with O. volvulus L3 larvae (P = 0.036). We conclude that Ov-ALT genes, like those of other filariae, are of interest from the standpoint of parasite transmission and infectivity. They may also offer promise as components of a future sub-unit vaccine should the means to enhance protection be achieved.

Amino Acid Sequence↗

PubMed2005

Relevance of ex vivo blood lymphocyte assay for in vivo lymphocyte function.

Determinations of in vitro proliferative and secretory activities of peripheral blood cells are used widely for research in clinical immunology but, to our knowledge, have not been evaluated as to their power to reflect in vivo activities quantitatively. Here, we addressed this question by quantitatively correlating the in vitro secretion of interleukin (IL)-5 by peripheral blood cells to the in vivo activity of IL-5 as reflected by peripheral-blood eosinophil counts. Studying 458 humans exposed to transmission of the nematode Onchocerca volvulus, IL-5 was measured in the supernatants of 0.02-ml whole-blood cells cultured in the presence of O. volvulus extract or mitogen. O. volvulus-reactive IL-5 secretion was correlated significantly to blood eosinophilia in a quantitative manner explaining 15.1% (95% CI 8.3-19.9%) of the variability of eosinophil counts. Interestingly, correlations were obtained only if parasite counts were included in the calculation using multiple regression analysis. The results show that in vitro assays of minute amounts of blood lymphocytes may quantitatively reflect activities of the entire lymphocyte population in vivo.

Adolescent↗

PubMed1994

[The evaluation of endemic onchocerciasis in the Amou prefecture (Togo)].

We have evaluated the endemicity of the onchocerciasis in two villages of the district of Amou in Togo, Okpahoué et Onglo. We have studied 294 subjects including 136 males and 158 females representing the quarter of the population of the two villages (clinical investigation and exsanguine cutaneous biopsy): 111 persons are parasited by Onchocerca volvulus that means a prevalence rate of 37.7%. We can therefore say that the villages are in a state of "meso-endemicity". We have been able to find nodules by 20 persons among the 111 that give a percentage of 6.8 of the examined persons. Among children of 3 to 9 years old, the prevalence and the average microfilaremia are respectively 8.86 and 3.54%. Among the persons of 50 or older than 50, we found a prevalence rate of 65.95% and an average microfilaremia of 28.37.

Adolescent↗

PubMed2005

Incrimination of Simulium thyolense (Diptera: Simuliidae) as the anthropophilic blackfly in the Thyolo focus of human onchocerciasis in Malawi.

The sibling species of the Simulium damnosum complex that are potential vectors in the foci of human onchocerciasis found in southern Malawi (the southern-most foci in Africa) were identified, using a combination of cytotaxonomic and molecular techniques. Simulium thyolense was found to be the most abundant species within the foci (representing 91% of the larvae collected), whilst S. kilibanum and cytoforms of the 'Ketaketa' subcomplex were the dominant members of the complex found outside of the foci. As all 188 biting female flies collected from the Thyolo, Mwanza and Mulanje foci were identified as S. thyolense, this species is probably the only significant vector of Onchocerca volvulus in the area, and the other Simulium species collected are assumed to be zoophilic. The results confirm the diagnostic value of the size of the amplicon(s) produced in PCR based on the sequences coding for the internal-transcribed-spacer region of the nuclear ribosomal DNA (ITS-1 rDNA), with a characteristic 340bp amplicon for S. thyolense. Chromosomal polymorphisms within S. thyolense indicate some degree of geographical isolation of the 'Thyolo-Mulanje' focus from the Mwanza focus.

Animals↗

PubMed1995

Molecular cloning and characterization of the filarial LIM domain proteins AvL3-1 and OvL3-1.

A full-length cDNA of the filarial nematode Acanthocheilonema viteae was isolated from a cDNA library of female worms, using a partial cDNA of the OvL3-1 gene of Onchocerca volvulus as a probe. The AvL3-1 cDNA contained an open reading frame which encoded for a protein with a theoretical molecular weight of 64 kDa. The deduced protein contained a predicted signal sequence, a short repetitive motive of unknown function, and three LIM domains. The structure of the LIM domains was identical to those of zyxin, a cytoskeleton-associated protein of chicken fibroblasts, suggesting that AvL3-1 has a similar role in filarial nematodes. The sequence information was used to isolate the homologous cDNA of O. volvulus by PCR from a cDNA library of female O. volvulus, which showed an overall identity of 76.9% to AvL3-1 on the protein level. AvL3-1 was expressed in Escherichia coli and the affinity-purified fusion free protein was used to immunized jirds (Meriones unguiculatus). Immunization together with the adjuvant STP or with Freund's adjuvant induced IgG and IgM antibody responses, but no significant protection against a challenge infection with L3 of A. viteae, compared to appropriate control groups.

Amino Acid Sequence↗

PubMed2004

The current status of onchocerciasis in the forest/savanna transition zone of Côte d'Ivoire.

Onchocerca volvulus exists in at least two strains in West Africa, while its black-fly vectors consist of sibling species, dwelling in the savanna and forest/transition zones. In transition and degraded forest zones both parasite strains and different sibling species of the vector can be sympatric. The strain of parasite in infected humans and in vector black-flies was determined in two bioclimes along the Bandama river of Côte d'Ivoire. The upper Bandama is located in the savanna bioclime while the Middle Bandama is located in a degraded forest zone. At both sites, savanna-dwelling sibling species of the Simulium damnosum sensu lato species complex predominated. The severe-strain of O. volvulus was the predominant strain at both sites. However, severe-strain parasites represented a significantly larger proportion of those found in the vector population than in the human population in the degraded forest of the Middle Bandama. These data suggest that in degraded forest areas recently invaded by savanna-dwelling species of S. damnosunz s.l. transmission of the severe-strain of the parasite might be more efficient than transmission of the mild-strain.

Animals↗

PubMed1994

Detrimental effects of onchocerciasis on marriage age and breast-feeding.

This paper examines the extent to which onchocercal skin lesions affect the age at marriage and the duration of lactation among infected women in forest areas of Nigeria. In a retrospective study, 145 multiparous women were asked about their breast-feeding behaviour. Ninety-seven per cent routinely breast-fed after delivery, although the duration of lactation for 75 infected and 70 non-infected women was different. Of the 75 women with Onchocerca volvulus infection, 73% experienced itching during breast-feeding; 26% breast-fed for not more than 3 months compared to 2.1% of non-infected women who breast-fed for the same period (p < 0.005). A multiple regression model showed severity of onchocercal lesions as an independent predictor of shorter duration of lactation for women with O. volvulus infection. Duration of breast-feeding was reduced by more than 9 months for 6 (25%) out of 24 infected women who breast-fed infants before and after the onset of itching from lesions. Also, while the minimum age at marriage was 9 years for non-infected women, it was 17 years for women whose lesions appeared before marriage. This preliminary study suggest that incessant itching and severe onchocerciasis lesions may be important predictors of failure of women to breast-feed for longer periods in rain-forest areas of Nigeria.

Adolescent↗

PubMed1998

[Occurrence of onchocerciasis in subjects coming from non-endemic areas and migrating to a hyperendemic area].

The incidence of Onchocerca volvulus infection was measured from 1992-93 to 1995 in six villages of initially uninfected migrants who settled in 1991 in the Vina Valley (Cameroon), an area of ongoing transmission of onchocerciasis. The mean annual incidence (MAI) exceeded 20% in the three communities located in the first line, and fewer than 15 km from the hyperendemic areas of the Central African Republic. The MAI was lower than 16% in the second line communities. As these populations are particularly at risk of developing ocular complications from onchocerciasis, it is recommended that repeated ivermectin distributions be organized in the migrant villages of the Vina Valley.

Animals↗

PubMed1992

Filarial parasites contain a ras homolog of the TC4/ran/Spil family.

We have isolated and characterized a gene encoding a novel GTP-binding protein of the GTPase superfamily in the filarial parasites Brugia malayi and Onchocerca volvulus. The deduced amino acid sequence of the cloned molecule has approximately 30% overall homology to ras proteins and approximately 90% homology to the 'ras-like' nuclear proteins TC4, ran and Spil. Rabbit antisera to bacterially expressed filarial protein detect a 24-22 kDa doublet in extracts of adult B. malayi and mature microfilariae, which is absent from immature microfilariae. Increased expression of the native parasite protein occurs when worms are cultured in the presence of epidermal growth factor.

Amino Acid Sequence↗

PubMed1999

[Deep onchocerciasis of the left thigh. An unusual case].

INTRODUCTION: Commonly onchocercoma has been presented as superficial and multiple nodules. When it's unique and deeply situated, its clinical diagnosis is difficult. An uncommon form of onchocercoma is reported. CASE REPORT: A 37 years old man presented a big tumor at the inferior third of the left thigh like lipoma or liposarcoma because of microcalcifications. The tumor was removed. It was a cyst containing a liquid like an "mango juice". The histological examination was performed. Degenerated microfilariae of Onchocerca volvulus was found. DISCUSSION: A big and deep onchocerma of the thigh is uncommon and diagnosis before operation is very difficult. Histological examination have eliminate filarial infections like Dracunculus medinensis and have given the right diagnosis. Radiological microcalcifications and absence of microfilariae at the parasilogical and ophthalmological examinations recall an "aged" onchocercoma. For this reason, we didn't realise a chemotherapy. CONCLUSION: This tumor in Sahel areas is very difficult to diagnose before operation. The histological examination is very important in this case. We don't use chemotherapy because this onchocercoma looks old without alive microfilariae.

Adult↗

PubMed1994

DNA sequence analysis using hierarchical ART-based Classification Networks.

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.

Algorithms↗

PubMed1995

Molecular characterization of a parasite antigen in sera from onchocerciasis patients that is immunologically cross-reactive with human keratin.

Onchocerca volvulus is a nematode that causes severe dermatitis and blindness in humans. Prior studies have shown that immune complexes in sera from onchocerciasis patients contain parasite antigens with M(r) of 23,000 and 65,000-70,000. Monoclonal antibody OV-1 binds to these antigens and to corresponding antigens in adult worm extracts and in vitro culture supernatants. OV-1 was used to immunoscreen an O. volvulus adult worm cDNA library. Clone OV1CF contains a 1632-bp open-reading frame that codes for a protein with a predicted M(r) of 63,000. The deduced protein sequence of OV1CF has 78% identity with Ascaris lumbricoides intermediate filament A and 40%-50% identity with several mammalian intermediate filaments. Antibodies raised to OV1CF bind to human keratin, and some sera from onchocerciasis patients contain antibodies to OV1CF and to keratin. Thus, immune complexes from onchocerciasis patients contain a parasite antigen that is immunologically cross-reactive with human intermediate filament proteins.

Adolescent↗

PubMed2003

Trehalose metabolism genes in Caenorhabditis elegans and filarial nematodes.

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.

Amino Acid Sequence↗

PubMed1998

Long-term quantitative ecological assessment of insecticides treatments in four African rivers: a methodological approach.

In West Africa different insecticides had been applied in selected river areas for the reduction of the blackfly populations vectors of Onchocerca volvulus, a parasite causing blindness. To evaluate the possible long term effects of the larvicides on the non target fauna an aquatic monitoring programme has been up from the initial phase of the project. Addressing the attention to the invertebrates data collected in four countries during a maximum period ranging from 1977 to 1996, this paper shows and discusses the data analysis strategy for the measure and interpretation of the biological variation. In particular the application of quantitative ecological analysis methods: Principal Component Analysis, rank abundance models and the community diversity indexes, is critically discussed and comments are given to the ecological interpretation of the results.

Africa↗

PubMedDate not supplied

Infectivity and transmission dynamics of simulium damnosum s. 1 around Owena dam (Ondo State).

A twelve month study on the infectivity and transmission dynamics of simulium damnosum s.1 around Owena dam was conducted as part of a longitudinal study of onchocerciasis in the community living in the vicinity of the dam. A total of 3,133 flies (49.6% nilliparous, 50.4% parous) were caught during the period of study and dissected. The annual biting rate per year was recorded as 33,663 flies while the parous biting rate was recorded as 16,780 for these flies. 0.4% of the flies were infected with Onchocerca volvulus larvae while 0.3% of these had the infective larvae. However 0.3% of the nulliparous flies were found to be infected with mermithid larvae and 0.5% with trematodes. The biting activity of the fly was observed to be bimodal with a small peak in the morning hours (10.00-11.00 hours) and a more pronounced peak in the evening (16.00-17.00 hours). An annual transmission potential of 109 larvae per man per year was recorded with 64% of the infection being recorded during the early dry season when the parous rate was very high. The implications of these findings to the study area are discussed.

Animals↗

PubMed2001

A dominant role for Fc gamma receptors in antibody-dependent corneal inflammation.

Although production of specific Ab is a critical element of host defense, the presence of Ab in tissues leads to formation of immune complexes, which can trigger a type III Arthus reaction. Our studies on a mouse model of river blindness showed that Ab production is essential for recruitment of neutrophils and eosinophils to the cornea and for development of corneal opacification. In the current study, we determined the relative contribution of complement and FcgammaR interactions in triggering immune complex-mediated corneal disease. FcgammaR(-/-) mice, C3(-/-) mice, and immunocompetent control (B6/129Sj) mice were immunized s.c. and injected intrastromally with Onchocerca volvulus Ags. Slit lamp examination showed that control mice, C3(-/-) mice, and control mice injected with cobra venom factor developed pronounced corneal opacification, whereas corneas of FcgammaR(-/-) mice remained completely clear. Furthermore, recruitment of neutrophils and eosinophils to the corneal stroma was significantly impaired in FcgammaR(-/-) mice, but not in C3(-/-) mice or cobra venom factor-treated mice. We therefore conclude that FcgammaR-mediated cell activation, rather than complement activation, is the dominant pathway of immune complex disease in the cornea. These findings demonstrate a novel role for FcgammaR interactions in mediating ocular inflammation.

Animals↗

PubMed1995

Studies on filariasis in Bauchi State, Nigeria. 1. Endemicity of human onchocerciasis in Ningi Local Government Area.

The endemicity of human onchocerciasis was assessed in eight rural, at-risk communities in Ningi Local Government Area, Bauchi State, Nigeria, between July 1990 and March 1991. Of the 1536 subjects skin-snipped, 334 (21.7%) were positive for Onchocerca volvulus microfilariae. Surprisingly, there was a significant inverse relationship between prevalence and mean microfilarial load (r = -0.608; P < 0.05). Males were more likely to be infected than females (P < 0.01) and cattle rearers (71.0% infected), farmers (49.8%) and fishermen (40.0%) had significantly higher prevalences than students/schoolchildren, housewives or traders (P < 0.001). Pruritus and itchy eyes were recorded in all age groups and appeared in much younger subjects than any other manifestations of the infection. Prevalence and onchocercal blindness were linearly related to intensity of infection. The epidemiological significance of these findings, in terms of a future community-wide programme of long-term chemoprophylaxis with Mectizan, is highlighted.

Adolescent↗

PubMed2000

Identification and localization of glutathione S-transferase as a potential target enzyme in Brugia species.

Brugia filarial nematodes are pathogenic lymphatic-dwelling parasites that, like other helminths, may modify the host's defense mechanisms by a major detoxification process involving glutathione-binding proteins such as glutathione S-transferases (GSTs). In the present study, soluble extracts of third-stage larvae, adult male and female worms, microfilariae of either B. pahangi or B. malayi or the adult worm excretory-secretory products of B. malayi were used to determine GST activity. These extracts and affinity-purified fractions of B. pahangi adult worms had a specific enzymatic activity when 1-chloro-2,4-dinitrobenzene was used as a substrate. The observance of this enzyme in all life cycle stages of Brugia spp. demonstrates its ubiquitous nature. Lavage of intraperitoneally infected jirds, but not that of uninfected jirds, also showed increased enzymatic activity, suggesting that GST is secreted in vivo. Soluble proteins of both Brugia spp. were strongly recognized by antibodies in sera from rabbits immunized with affinity-purified native GST of Onchocerca volvulus. Immunohistochemical studies localized these proteins in adult worms, demonstrating cross-reactivity between the GST of these two filarial nematodes. The effect of this enzyme on the motility and viability of adult worms, microfilariae, and larvae was tested in vitro using a battery of known GST inhibitors. Of all those tested, ethacrynic acid, N-ethylmalemide, 4-nitropyridine-oxide, or 1-chloro-2,4-dinitrobenzene at micromolar concentrations reduced the viability and motility of microfilariae, third-stage larvae, and adult worms. These results suggest that Brugia GSTs are major metabolic enzymes and may play an important role in the parasite's survival.

Animals↗