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Regulatory T cells in human lymphatic filariasis: stronger functional activity in microfilaremics.

ABSTRACT: Infection with filarial parasites is associated with T cell hyporesponsiveness, which is thought to be partly mediated by their ability to induce regulatory T cells (Tregs) during human infections. This study investigates the functional capacity of Tregs from different groups of filarial patients to suppress filaria-specific immune responses during human filariasis. Microfilaremic (MF), chronic pathology (CP) and uninfected endemic normal (EN) individuals were selected in an area endemic for Brugia timori in Flores island, Indonesia. PBMC were isolated, CD4CD25(hi) cells were magnetically depleted and in vitro cytokine production and proliferation in response to B. malayi adult worm antigen (BmA) were determined in total and Treg-depleted PBMC. In MF subjects BmA-specific T and B lymphocyte proliferation as well as IFN-gamma, IL-13 and IL-17 responses were lower compared to EN and CP groups. Depletion of Tregs restored T cell as well as B cell proliferation in MF-positives, while proliferative responses in the other groups were not enhanced. BmA-induced IL-13 production was increased after Treg removal in MF-positives only. Thus, filaria-associated Tregs were demonstrated to be functional in suppressing proliferation and possibly Th2 cytokine responses to BmA. These suppressive effects were only observed in the MF group and not in EN or CP. These findings may be important when considering strategies for filarial treatment and the targeted prevention of filaria-induced lymphedema.

SUBMITTER: Wammes LJ

PROVIDER: S-EPMC3362610 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Regulatory T cells in human lymphatic filariasis: stronger functional activity in microfilaremics.

Wammes Linda J LJ Hamid Firdaus F Wiria Aprilianto E AE Wibowo Heri H Sartono Erliyani E Maizels Rick M RM Smits Hermelijn H HH Supali Taniawati T Yazdanbakhsh Maria M

PLoS neglected tropical diseases 20120529 5

Infection with filarial parasites is associated with T cell hyporesponsiveness, which is thought to be partly mediated by their ability to induce regulatory T cells (Tregs) during human infections. This study investigates the functional capacity of Tregs from different groups of filarial patients to suppress filaria-specific immune responses during human filariasis. Microfilaremic (MF), chronic pathology (CP) and uninfected endemic normal (EN) individuals were selected in an area endemic for Bru ...[more]

PMID: 22666510

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Project description:BackgroundThe prevalence of Wuchereria bancrofti, which causes lymphatic filariasis (LF) in The Gambia was among the highest in Africa in the 1950s. However, surveys conducted in 1975 and 1976 revealed a dramatic decline in LF endemicity in the absence of mass drug administration (MDA). The decline in prevalence was partly attributed to a significant reduction in mosquito density through the widespread use of insecticidal nets. Based on findings elsewhere that vector control alone can interrupt LF, we asked the question in 2013 whether the rapid scale up in the use of insecticidal nets in The Gambia had interrupted LF transmission.Methodology/principal findingWe present here the results of three independently designed filariasis surveys conducted over a period of 17 years (1997-2013), and involving over 6000 subjects in 21 districts across all administrative divisions in The Gambia. An immunochromatographic (ICT) test was used to detect W. bancrofti antigen during all three surveys. In 2001, tests performed on stored samples collected between 1997 and 2000, in three divisions, failed to show positive individuals from two divisions that were previously highly endemic for LF, suggesting a decline towards extinction in some areas. Results of the second survey conducted in 2003 showed that LF was no longer endemic in 16 of 21 districts surveyed. The 2013 survey used a WHO recommended LF transmission verification tool involving 3180 6-7 year-olds attending 60 schools across the country. We demonstrated that transmission of W. bancrofti has been interrupted in all 21 districts.ConclusionsWe conclude that LF transmission may have been interrupted in The Gambia through the extensive use of insecticidal nets for malaria control for decades. The growing evidence for the impact of malaria vector control activities on parasite transmission has been endorsed by WHO through a position statement in 2011 on integrated vector management to control malaria and LF.

Project description:IntroductionLymphatic filariasis (LF), a neglected tropical disease (NTD) preventable through mass drug administration (MDA), is one of six diseases deemed possibly eradicable. Previously we developed one LF elimination scenario, which assumes MDA scale-up to continue in all countries that have previously undertaken MDA. In contrast, our three previously developed eradication scenarios assume all LF endemic countries will undertake MDA at an average (eradication I), fast (eradication II), or instantaneous (eradication III) rate of scale-up. In this analysis we use a micro-costing model to project the financial and economic costs of each of these scenarios in order to provide evidence to decision makers about the investment required to eliminate and eradicate LF.Methodology/key findingsCosting was undertaken from a health system perspective, with all results expressed in 2012 US dollars (USD). A discount rate of 3% was applied to calculate the net present value of future costs. Prospective NTD budgets from LF endemic countries were reviewed to preliminarily determine activities and resources necessary to undertake a program to eliminate LF at a country level. In consultation with LF program experts, activities and resources were further reviewed and a refined list of activities and necessary resources, along with their associated quantities and costs, were determined and grouped into the following activities: advocacy and communication, capacity strengthening, coordination and strengthening partnerships, data management, ongoing surveillance, monitoring and supervision, drug delivery, and administration. The costs of mapping and undertaking transmission assessment surveys and the value of donated drugs and volunteer time were also accounted for. Using previously developed scenarios and deterministic estimates of MDA duration, the financial and economic costs of interrupting LF transmission under varying rates of MDA scale-up were then modelled using a micro-costing approach. The elimination scenario, which includes countries that previously undertook MDA, is estimated to cost 929 million USD (95% Credible Interval: 884m-972m). Proceeding to eradication is anticipated to require a higher financial investment, estimated at 1.24 billion USD (1.17bn-1.30bn) in the eradication III scenario (immediate scale-up), with eradication II (intensified scale-up) projected at 1.27 billion USD (1.21bn-1.33bn), and eradication I (slow scale-up) estimated at 1.29 billion USD (1.23bn-1.34bn). The economic costs of the eradication III scenario are estimated at approximately 7.57 billion USD (7.12bn-7.94bn), while the elimination scenario is projected to have an economic cost of 5.21 billion USD (4.91bn-5.45bn). Countries in the AFRO region will require the greatest investment to reach elimination or eradication, but also stand to gain the most in cost savings. Across all scenarios, capacity strengthening and advocacy and communication represent the greatest financial costs, whereas mapping, post-MDA surveillance, and administration comprise the least.Conclusions/significanceThough challenging to implement, our results indicate that financial and economic savings are greatest under the eradication III scenario. Thus, if eradication for LF is the objective, accelerated scale-up is projected to be the best investment.

Dataset Information

Regulatory T cells in human lymphatic filariasis: stronger functional activity in microfilaremics.

Publications

Regulatory T cells in human lymphatic filariasis: stronger functional activity in microfilaremics.

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