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Onchocerciasis is a skin and eye disease that exerts a heavy socio-economic burden, particularly in sub-Saharan Africa, a region which harbours greater than 96% of either infected or at-risk populations. The elimination plan for the disease is currently challenged by many factors including amongst others; the potential emergence of resistance to the main chemotherapeutic agent, ivermectin (IVM). Novel tools, including preventative and therapeutic vaccines, could provide additional impetus to the disease elimination tool portfolio. Several observations in both humans and animals have provided evidence for the development of both natural and artificial acquired immunity. In this study, immuno-informatics tools were applied to design a filarial-conserved multi-epitope subunit vaccine candidate, (designated Ov-DKR-2) consisting of B-and T-lymphocyte epitopes of eight immunogenic antigens previously assessed in pre-clinical studies. The high-percentage conservation of the selected proteins and epitopes predicted in related nematode parasitic species hints that the generated chimera may be instrumental for cross-protection. Bioinformatics analyses were employed for the prediction, refinement, and validation of the 3D structure of the Ov-DKR-2 chimera. In-silico immune simulation projected significantly high levels of IgG1, T-helper, T-cytotoxic cells, INF-γ, and IL-2 responses. Preliminary immunological analyses revealed that the multi-epitope vaccine candidate reacted with antibodies in sera from both onchocerciasis-infected individuals, endemic normals as well as loiasis-infected persons but not with the control sera from European individuals. These results support the premise for further characterisation of the engineered protein as a vaccine candidate for onchocerciasis., info:eu-repo/semantics/published

Human Onchocerciasis is a neglected tropical disease of debilitating consequences caused by the nodule dwelling nematode Onchocerca volvulus. Excretory Secretory Products (ESPs) help the parasite to establishing infection in an immunocompetent host and thus make O. volvulus ESPs potential sources of diagnostic, therapeutic or immunomodulatory markers. Here, a blend of bioinformatics, biochemical, analytical and immunologic methods were employed to identify one such ESP as a GM2 activator protein orthologue. The cDNA of OvGM2AP was detected in most parasite stages and the protein was detected in ESPs of adult males, adult females and L3 stage. Recombinant OvGM2AP was expressed in Sf21 insect cells and was found to be glycosylated at Asn 173 by mass spectrometry analysis. The recombinant OvGM2AP could significantly differentiate infected from non-infected individuals on total IgG ELISA. No improvement in diagnostic indices was observed when IgG sub-classes were used to detect OvGM2AP by ELISA. A drop in IgG titre was observed to correlate with increased rounds of ivermectin administration. However, as observed from alignment of OvGM2AP sequences with other nematode species, recombinant OvGM2AP was found to cross react with sera from patients with other nematode infections such as Loa loa, Mansonella perstans and Brugia malayi. GM2 degradation to GM3 could not be mediated by OvGM2AP in the presence of human β-hexosaminidase A. However, when examined for competitive inhibition with artificial GM2 substrates such as MUG and MUGs, OvGM2AP was found to competitively inhibit the degradation of MUG by β-hexosaminidase A as opposed to the human GM2AP. Due to the genetic intractability of O. volvulus, Caenorhabditis elegans was used as a model to study the function of OvGM2AP. The C. elegans orthologous gene cpp-1 was found to be expressed predominantly in the hypoderm, with a paralogous form confined to specialized hypodermis such as seam cells. CRISPR-CAS9 mediated knock-out, Doctorat en Sciences, info:eu-repo/semantics/nonPublished

The public health goal of onchocerciasis in Africa has advanced from control to elimination. In this light, accurate diagnosis is necessary to determine treatment endpoints and confirm elimination, as well as to conduct surveillance for the identification of any possible recrudescence of the disease. Currently, the monitoring of onchocerciasis elimination relies on the Ov-16 test. However, this test is unable to discriminate between past and active infections. Furthermore, about 15-25% of infected persons are reported to be negative for the Ov-16 test, giving a misleading sense of security to false-negative individuals who might continue to serve as reservoirs for infections. Therefore, we opted to design and validate a more sensitive and specific chimeric antigen (OvMANE1) for onchocerciasis diagnosis, using previously reported immunodominant peptides of O. volvulus, the parasite responsible for the disease. In silico analysis of OvMANE1 predicted it to be more antigenic than its individual peptides. We observed that OvMANE1 reacts specifically and differentially with sera from O. volvulus infected and non-infected individuals, as well as with sera from communities of different levels of endemicity. Moreover, we found that total IgG, unlike IgG4 subclass, positively responded to OvMANE1, strongly suggesting its complementarity to the Ov-16 diagnostic tool, which detects Ov-16 IgG4 antibodies. Overall, OvMANE1 exhibited the potential to be utilized in the development of specific diagnostic tools-based on both antibody capture and antigen capture reactions-which are indispensable to monitor the progress of onchocerciasis elimination programs., SCOPUS: ar.j, info:eu-repo/semantics/published

info:eu-repo/semantics/published

BACKGROUND: After more than 15 years of community-directed treatment with ivermectin (CDTI) in the Centre 1, Littoral 2 and West CDTI projects in Cameroon, the epidemiological evaluation conducted in 2011 revealed that onchocerciasis endemicity was still high in some communities. To investigate the potential reasons explaining this high endemicity, a cluster coverage survey was conducted in April-May 2015 in three health districts (HD), to assess the implementation of the CDTI, the 2014 therapeutic coverage and the five-year adherence to treatment. A two-stage cluster design was considered during analyses, with data weighted proportionally to age and gender distribution in the population. RESULTS: In the three HDs, 69 community leaders, 762 heads of households, 83 community drug distributors (CDD) and 2942 household members were interviewed. The CDTI organization and the involvement of heads of households were in average weak, with 84.0% (95% CI: 81.2-86.4%) of them who had not participated in activities during the 2014 mass drug administration (MDA). On average, six of ten community leaders declared that the period of treatment was decided by the health personnel while the CDDs selection was made during a community meeting for only 43.4% of them. The 2014 weighted therapeutic coverage was 64.1% (95% CI: 56.8-70.9%), with no significant difference in the three HDs. The survey coverages were lower than the reported coverages with a significant difference varying from 14.1% to 22.0%. Among those aged 10 years and above, 57.8% (95% CI: 50.2-65.1%) declared having taken the treatment each time during the last five MDAs with no significant difference among HDs, while 9.8% (95% CI: 7.5-12.8%) declared that they had never taken the drug. In multivariate analysis, the most important factors associated with the five-year adherence to treatment were high involvement in CDTI and age (40+ years). CONCLUSIONS: Despite more than 15 years of CDTI, there was still weak community pa

Onchocerciasis is a severely debilitating yet neglected tropical disease (NTD) currently affecting approximately 15.5 million people, including 12.2 million people with skin disease and 1.025 million with vision loss. The disease causes social stigma, generates and perpetuates poverty, and leads ultimately to irreversible unilateral or bilateral blindness if untreated. Consequently, onchocerciasis is a major impediment to socioeconomic development in addition to being a major public health concern in some African countries. Many control programs have been launched against the disease with moderate successes achieved in Africa. These limited outcomes are partially due to the unavailability of reliable, non-invasive and easily applicable diagnostic tools for mapping endemic regions, monitoring control program successes, determining treatment endpoints and post-elimination surveillance. The current WHO recommendations for certification of elimination include the use of the Ov16 antibody detection ELISA which is flawed by an intrinsic systematic error as 15-25% of infected populations may not produce antibodies against this antigen due to genetic restrictions. With the recent shift in the global health goal of onchocerciasis from control to elimination, there is a need for the development of novel appropriate tools. These tools include amongst others, drugs, diagnostics, and vaccines. In this work, bioinformatics analyses combined with immunological assays were applied in a bid to develop potential tools for the current elimination programs. With regards to chemotherapy, Ivermectin which has been the sole drug for onchocerciasis treatment for over 30 years kills only the microfilariae (mf) leaving the adult worms intact which continue to produce the mf. Moreover, there is a recent problem of development of parasite resistance to this drug. In addition, moxidectin which was recently approved for treatment is contra-indicated in pregnant women and children under 12 who co, L’onchocercose est une maladie tropicale sévèrement débilitante mais négligée qui touche actuellement environ 15,5 millions de personnes, dont 12,2 millions de souffrant de maladies de la peau et 1,025 millions de souffrant de perte de vision. La maladie provoque une stigmatisation sociale, génère et perpétue la pauvreté et finit par conduire à une cécité unilatérale ou bilatérale irréversible si elle n'est pas traitée. En conséquence, l’onchocercose est un obstacle majeur au développement socioéconomique en plus d’être une préoccupation majeure pour la santé publique. De nombreux programmes de lutte ont été lancés contre la maladie, avec quelques succès en Afrique. Ces résultats sous-optimaux (limités) sont en partie dus à l’absence d’outils fiables, non invasifs et facilement applicables pour la cartographie des régions endémiques, le suivi des succès des programmes de contrôle, la détermination des paramètres de traitement et la surveillance post-élimination. Les recommandations actuelles de l’OMS pour la certification de l’élimination incluent l’utilisation du test ELISA de détection d’anticorps Ov16, entaché d’une erreur systématique intrinsèque puisque 15 à 25% des populations infectées peuvent ne pas produire d’anticorps contre cet antigène en raison de restrictions génétiques. Avec l’évolution récente de l’objectif de santé mondial de l’onchocercose de passé de la lutte à l’élimination, il est donc nécessaire de mettre au point de nouveaux outils appropriés. Ces outils nécessaires incluent, entre autres, des médicaments, des diagnostics et des vaccins. Dans ce travail, des analyses bio-informatiques combinées à des tests immunologiques ont été appliquées dans le but de développer des outils potentiels pour les programmes d'élimination actuels. En ce qui concerne la chimiothérapie, l’ivermectine, qui est le seul médicament utilisé depuis plus de 30 ans pour le traitement de l’onchocercose, ne tue que les microfilaires (mf) laissant intacts les vers adultes qu, Option Biologie moléculaire du Doctorat en Sciences, info:eu-repo/semantics/nonPublished

Onchocerciasis is a severely debilitating yet neglected tropical disease (NTD) that creates social stigma, generates and perpetuates poverty, and leads ultimately in some cases to irreversible unilateral or bilateral blindness if untreated. Consequently, the disease is a major impediment to socioeconomic development. Many control programs have been launched for the disease with moderate successes achieved. This mitigated hit is partially due to the lingering need for reliable, non-invasive and easily applicable tools for mapping endemic regions and post-elimination surveillance. In this work, bioinformatics analyses combined with immunological assays were applied in a bid to develop potential tools for diagnosis and assessing the success of drug treatment programs. We report that (i) the O. volvulus antigen, Ov58GPCR is a G-protein coupled receptor (GPCR) conserved in related nematodes, (ii) synthetic peptides predicted to be in the extracellular domain (ECD) of Ov58GPCR are indeed immunogenic epitopes in actively-infected individuals, (iii) synthetic peptide cocktails discriminate between actively-infected individuals, treated individuals and healthy African controls, (iv) polyclonal antibodies against one of the peptides or against the bacterially-expressed ECD reacted specifically with the native antigen of O. volvulus total and surface extracts, (v) Ov58GPCR is transcribed in both larvae and adult parasite stages, (vi) IgG and IgE responses to the recombinant ECD decline with ivermectin treatment. All these findings suggest that the extracellular domain and synthetic peptides of Ov58GPCR, as well as the specific immune response generated could be harnessed in the context of disease diagnosis and surveillance., SCOPUS: ar.j, info:eu-repo/semantics/published

BACKGROUND: The fight against onchocerciasis in Africa has boomed thanks to the Community Directed Treatment with Ivermectin (CDTI) program. However, in Cameroon, after more than 15 years of mass treatment, onchocerciasis prevalence is still above the non-transmission threshold. This study aimed to explore a possible association between people's beliefs/perceptions of onchocerciasis and of CDTI program, and their adherence to ivermectin in three regions of Cameroon. METHODOLOGY/PRINCIPAL FINDINGS: A cross sectional survey was carried out in three health districts with persistent high onchocerciasis prevalence. Participants were randomly selected in 30 clusters per district. Adherence to ivermectin was comparable between Bafang and Bafia (55.0% and 48.8%, respectively, p>0.05) and lower in Yabassi (40.7%). Among all factors related to program perceptions and disease representations that were studied, perceptions of the program are the ones that were most determinant in adherence to ivermectin. People who had a "not positive" opinion of ivermectin distribution campaigns were less compliant than those who had a positive opinion about the campaigns (40% vs 55% in Bafang, and 48% vs 62% in Bafia, p<0.01), as well as those who had a negative appreciation of community drug distributors' commitment (22% vs 53% in Bafang, 33% vs 59% in Bafia, 27% vs 47% in Yabassi; p<0.01). The most common misconception about onchocerciasis transmission was the lack of hygiene, especially in Bafia and Yabassi. In Bafang, high proportions of people believed that onchocerciasis was due to high consumption of sugar (31% vs less than 5% in Bafia and Yabassi, p<0.001). CONCLUSION/SIGNIFICANCE: There are still frequent misconceptions about onchocerciasis transmission in Cameroon. Perceptions of ivermectin distribution campaigns are more strongly associated to adherence. In addition to education/sensitisation on onchocerciasis during the implementation of the CDTI program, local health authorities

After more than a decade of community-directed treatment with ivermectin (CDTI) in the West Region of Cameroon, epidemiological evaluation conducted in 2011 showed that onchocerciasis endemicity was still high in some communities. The conceptual framework for onchocerciasis elimination recommends in such case, to conduct additional phase 1A surveys at intervals of three to four years. Therefore, to assess the progress made towards the elimination of onchocerciasis in the West CDTI projects, we conducted a cross-sectional survey in May 2015 in 15 unevaluated communities where the highest baseline endemicity level were found in 1996. All volunteers living for at least five years in the community, aged five years or more, underwent clinical and parasitological examinations. Individual adherence to ivermectin treatment was also assessed. Analyses of data were weighted proportionally to age and gender distribution in the population. The mean age was 28.4 ± 22.2 years and there were 55% of women among the 2058 individuals examined. The weighted prevalences were 5.5%, 2.1% and 1.7% for microfilaridermia, nodule and cutaneous signs, respectively. The weighted microfilaridermia prevalences varied from 4.0 in 5-9 years old to 11.6% in 40-49 years old. In the 30 children under 10 years examined in Makouopsap, the weighted prevalences were 49.9% for microfilaridermia and 13.3% for nodule. In surveyed communities, the weighted prevalences varied from 0 to 41.6% for microfilaridermia, with 11 (73.3%) communities having <5%. Except Makouopsap which had 41.6%, all the surveyed communities were below 15% for microfilaridermia prevalence. The community microfilarial load (CMFL) expressed in microfilariae/skin snip (mf/ss), also significantly dropped by 98-100%, from 3.75-33.16 mf/ss in 1996 to 0-0.94 mf/ss in 2015. The weighted therapeutic coverage in 2014 was 69.4% and the 5 years' adherence was only 39.3% among participants. After more than 15 years of CDTI, there is an important p