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[
Filaria J,
2003]
BACKGROUND: Ov-CHI-1 is a chitinase specifically expressed in the infective stage larvae of the human filarial parasite Onchocerca volvulus. Evidence has show that it could be a vaccine candidate, however, there is no data available regarding the immunological status of people naturally exposed to infective stage larvae and thus provoked by this antigen. METHOD: We analysed the Ov-CHI-1-specific immune response present in four endemic foci of human onchocerciasis (Ecuador, Nigeria, Togo and Cameroon) by enzyme-linked immunosorbent assays and T-cell proliferation assays. RESULTS: In these foci of infection, antibodies to Ov-CHI-1 were found to be present in only 22% of individuals from Ecuador, but were detected in 42-62% of infected individuals in the three foci from West Africa (Nigeria, Togo and Cameroon). There was found to be no relationship between antibody level and age, gender, or infection intensity as indicated by microfilarial density and numbers of skin nodules. The isotype response to Ov-CHI-1 was dominated by the presence of IgG3, IgG1 was present to a lesser extent. Our results show a positive correlation between N- and C-termini of Ov-CHI-1 in their ability to provoke humoral and cellular immune responses in the human. Peripheral blood mononuclear cell (PBMC) proliferative responses to Ov-CHI-1 when assayed, were found to be significantly higher in the individuals from endemic areas and there was a statistically elevated response to Ov-CHI-1 in the infected individuals when compared to putative immune individuals. CONCLUSION: Ov-CHI-1 is an antigen that we have found strongly induces both humoral and cellular immune responses in humans.
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[
J Biol Chem,
2001]
A recently reported chitinase gene, expressed in the infective, third-stage (L3) larvae of the human filarial parasite Onchocerca volvulus, belongs to the family 18 glycosyl hydrolases and has been designated
Ov-chi-1. The gene product of
Ov-chi-1 is chitinolytic. Allosamidin ablates activity of the native enzyme in a dose-dependent manner but did not significantly inhibit the moulting of L3 larvae. Mono-specific antibodies were used to characterize Ov-CHI-1 as a 60-kDa protein expressed almost exclusively in L3 stages. Immunoelectron microscopy showed that Ov-CHI-1 expression is initiated in late L2 larvae and increases markedly in infective, L3 larvae. It is synthesized exclusively in the glandular esophagus and stored within discrete secretory granules. Secretion occurs through de-granulation during post-infective development, and the primary route of transport appears to be via the pseudo-coelom. An orthologue of
Ov-chi-1 was detected in Caenorhabditis elegans by BLAST analysis. It is constitutively expressed at a low level and is overexpressed in dauer larvae and embryonated eggs. It is chitinolytic. We conclude that Ov-CHI-1 is a highly stage-specific enzyme that may have a role in infectivity of the parasite, aiding escape from the vector or participating in early post-infective migration and/or development. The identification of an orthologue in C. elegans opens the way for further studies into the biological function(s) of this intriguing parasite product.
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[
Genes Dev,
2016]
Nucleotides are required in order to replicate DNA in the developing germline. Here, Chi and colleagues (pp. 307-320) have used Caernohabditis elegans to identify a GLP-1-dependent checkpoint that senses food (bacterially)-supplied nucleotide levels, arresting reproductive development in the absence of sufficient nucleotide supplies.
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[
J Infect Dis,
2017]
We have developed a serologically based immunophenotyping approach to study Onchocerca volvulus (Ov) population diversity. Using genomic sequence data and polymerase chain reaction-based genotyping, we identified nonsynonymous single-nucleotide polymorphisms (SNPs) in the genes of 16 major immunogenic Ov proteins: Ov-CHI-1/Ov-CHI-2, Ov16, Ov-FAR-1, Ov-CPI-1, Ov-B20, Ov-ASP-1, Ov-TMY-1, OvSOD1, OvGST1, Ov-CAL-1, M3/M4, Ov-RAL-1, Ov-RAL-2, Ov-ALT-1, Ov-FBA-1, and Ov-B8. We assessed the immunoreactivity of onchocerciasis patient sera (n = 152) from the Americas, West Africa, Central Africa, and East Africa against peptides derived from 10 of these proteins containing SNPs. Statistically significant variation in immunoreactivity among the regions was seen in SNP-containing peptides derived from 8 of 10 proteins tested: OVOC1192(1-15), OVOC9988(28-42), OVOC9225(320-334), OVOC7453(22-36), OVOC11517(14-28), OVOC3177(283-297), OVOC7911(594-608), and OVOC12628(174-188). Our data show that differences in immunoreactivity to variant antigenic peptides may be used to characterize Ov populations, thereby elucidating features of Ov population biology previously inaccessible because of the limited availability of parasite material.
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[
Mol Biochem Parasitol,
2008]
Chitinase expression in microfilariae of the parasitic nematode Brugia malayi (B. malayi, Bm) is coincidental with the onset of their infectivity to mosquitoes. An antibody raised to Onchocerca volvulus (O. volvulus, Ov) infective-stage larval chitinase (Ov-CHI-1) was specifically reactive against B. malayi microfilarial chitinase and was used to study the localization of chitinase in B. malayi during microfilarial development and transmission to the insect vector. Immuno-electron microscopy (IEM) was used to demonstrate that the chitinase was confined to the inner body of the microfilariae and furthermore that chitinase was only present in sheathed microfilarial species, although the inner body is present in all species. Observation using the IEM implicates two distinct routes of chitinase secretion from the inner body, via either the pharyngeal thread, or during transmission of the microfilariae to the vector, contained in vesicle-like structures. Many morphological studies have described the structure of the inner body, but no function has been assigned to it as of yet. Although it has been commented that the cells surrounding the inner body and pharyngeal thread are those destined to become the intestine and pharynx and that the inner body represents a store of material. Our studies suggest that chitinase is one such product stored in the inner body and that it is secreted during the exsheathment of the microfilaria in the mosquito.
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[
Parasite Immunol,
2018]
In our previous study, a proteome-wide screen was conducted to identify linear epitopes in this parasite's proteome, resulting in the discovery of three immunodominant motifs. Here we investigated whether such antigenic peptides were found in proteins that were already known as vaccine candidates and excretome/secretome proteins for O. volvulus. This approach led to the identification of 71 immunoreactive stretches in 46 proteins. A deep-dive into the immunoreactivity profiles of eight vaccine candidates that were chosen as most promising candidates for further development (Ov-CPI-2,Ov-ALT-1,Ov-RAL-2,Ov-ASP-1,Ov-103,Ov-RBP-1,Ov-CHI-1, andOv-B20), resulted in the identification of a poly-glutamine stretch in Ov-RAL-2 that has properties for use as a serodiagnostic marker for O. volvulus infection. A peptide ELISA was developed, and the performance of this assay was evaluated. Based on this assessment, it was found that this assay has a sensitivity of 75.0% [95% CI: 64.9%-83.5%] and a specificity of 98.5% [95% CI: 94.6%-99.8%]. Furthermore, 8.7% reactivity in Asian parasite-infected individuals (8 out of 92) was observed. Besides this identification of a linear epitope marker, the information on the presence of linear epitopes in vaccine candidate proteins might be useful in the study of vaccines for river blindness. This article is protected by copyright. All rights reserved.
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[
IDrugs,
2010]
CHI''s Seventh Annual Conference on High-Content Analysis (HCA), held in San Francisco, incorporated topics covering new developments in the field of HCA, including hardware and software updates, new biological models for HCA and pathway analysis. This conference report highlights selected presentations on the use of HCA for the characterization of stem cells, cell-colony analysis, the validation of disease models and the identification of antiparasitic compounds.
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[
Mech Dev,
2009]
Proper coordination of oogenesis, ovulation, and fertilization is essential for successful reproduction. In Caenorhabditis elegans, a strong loss-of-function mutation in
dpl-1, which encodes a subunit of the E2F heterodimeric transcription factor EFL-1/DPL-1, causes severe defects during ovulation and fertilization. Here we demonstrate that the somatic gonad structure and sheath cell contraction rate appear normal in
dpl-1 mutants, but that dilation of the spermatheca valve does not occur properly, causing oocytes to become trapped in the proximal gonad arm and enter endomitosis. This ovulation defect can be partially suppressed by increasing the activity of ITR-1, an inositol triphosphate receptor in the spermatheca that promotes dilation in response to IP(3) signaling. Tissue-specific rescue experiments demonstrate that expression of DPL-1 in germ cells but not the spermatheca can restore both ovulation and fertilization in
dpl-1 mutants, indicating that the absence of DPL-1 likely disrupts a pro-ovulation signal originating in the oocyte that in turn stimulates the spermatheca. Moreover, we found that expression of a single EFL-1/DPL-1-responsive gene,
rme-2, in the germ line of
dpl-1 mutants significantly rescues ovulation, but not fertilization. Instead, other EFL-1/DPL-1-responsive genes function to promote successful fertilization. We propose that DPL-1 acts with EFL-1 in developing oocytes to directly regulate a transcriptional program that couples the critical events of ovulation and fertilization.
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[
Nematology,
2000]
A technique is described that refines the standard sugar flotation procedure used to isolate nematodes from their surroundings. By centrifuging nematodes in a number of increasing specific gravity solutions and plotting the fraction floating, the cumulative probability distribution of the population's specific gravity is generated. By assuming normality, the population mean, mu, and standard deviation, sigma, are found by a nonlinear least squares procedure. These density parameters along with their error covariance matrix may be used as a taxonomic physical character. A chi-squared test is derived for comparing populations. Mean and standard deviation pairs (mu, sigma) were found for the specific gravities of the adult stage of the plant parasites Pratylenchus agilis (1.068, 0.017), P. scribneri (1.073, 0.028), P. penetrans (1.058, 0.008) and the bacterial-feeder Caenorhabditis elegans (1.091, 0.016).
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[
International Worm Meeting,
2015]
The conserved eight subunit DREAM (DP, Retinoblastoma [Rb]-like, E2F, and MuvB) complex is a regulator of cell cycle and quiescence genes and plays an important role in development and disease. The C. elegans DREAM members are LIN-35/Rb-like, EFL-1/E2F, DPL-1/DP1, LIN-8, LIN-37, LIN-52, LIN-53, and LIN-54. Recent work has demonstrated that C. elegans direct DREAM targets are de-repressed in the absence of the Rb-like protein LIN-35 and that high gene body levels of the histone variant H2A.Z are linked with target repression1. However, the mechanism that generates gene body H2A.Z enrichment, and the relationship between DREAM and H2A.Z are not currently understood. Furthermore, the functions and regulatory interactions of individual complex members are not clear. For example, LIN-35 has been demonstrated to be a transcriptional repressor by a number of groups, whilst the DP and E2F proteins have previously been reported to act as activators of transcription2. In addition, mutants of individual DREAM complex members do not all have the same phenotype, indicating different functions. Therefore, we are investigating the contribution of DPL-1 (DP) and EFL-1 (E2F) to DREAM target gene repression. We are also carrying out a GFP reporter screen to identify additional components required for DREAM-mediated repression, to elucidate the mechanisms behind DREAM mediated developmental control.1. Latorre, I., Chesney, M.A., Garrigues, J.M., Stempor, P., Appert, A., Francesconi, M., Strome, S., and Ahringer, J. (2015) 'The DREAM complex promotes gene body H2A.Z for target repression', Genes Dev., 29, 495-5002. Chi, W & Reinke, V. (2006) 'Promotion of oogenesis and embryogenesis in the C. elegans gonad by EFL-1/DPL-1 (E2F) does not require LIN-35 (pRB)', Development, 133, 3147-57.