Circulating CD14brightCD16+ 'intermediate' monocytes exhibit enhanced parasite pattern recognition in human helminth infection.

Circulating monocyte sub-sets have recently emerged as mediators of divergent immune functions during infectious disease but their role in helminth infection has not been investigated. In this study we evaluated whether 'classical' (CD14brightCD16-), 'intermediate' (CD14brightCD16+), and 'non-classical' (CD14dimCD16+) monocyte sub-sets from peripheral blood mononuclear cells varied in both abundance and ability to bind antigenic material amongst individuals living in a region of Northern Senegal which is co-endemic for Schistosoma mansoni and S. haematobium. Monocyte recognition of excretory/secretory (E/S) products released by skin-invasive cercariae, or eggs, of S. mansoni was assessed by flow cytometry and compared between S. mansoni mono-infected, S. mansoni and S. haematobium co-infected, and uninfected participants. Each of the three monocyte sub-sets in the different infection groups bound schistosome E/S material. However, 'intermediate' CD14brightCD16+ monocytes had a significantly enhanced ability to bind cercarial and egg E/S. Moreover, this elevation of ligand binding was particularly evident in co-infected participants. This is the first demonstration of modulated parasite pattern recognition in CD14brightCD16+ intermediate monocytes during helminth infection, which may have functional consequences for the ability of infected individuals to respond immunologically to infection

Enhanced Pro-Inflammatory Cytokine Responses following Toll-Like-Receptor Ligation in Schistosoma haematobium-Infected Schoolchildren from Rural Gabon

BACKGROUND: Schistosoma infection is thought to lead to down-regulation of the host's immune response. This has been shown for adaptive immune responses, but the effect on innate immunity, that initiates and shapes the adaptive response, has not been extensively studied. In a first study to characterize these responses, we investigated the effect of Schistosoma haematobium infection on cytokine responses of Gabonese schoolchildren to a number of Toll-like receptor (TLR) ligands. METHODOLOGY: Peripheral blood mononuclear cells (PBMCs) were collected from S. haematobium-infected and uninfected schoolchildren from the rural area of Zile in Gabon. PBMCs were incubated for 24 h and 72 h with various TLR ligands, as well as schistosomal egg antigen (SEA) and adult worm antigen (AWA). Pro-inflammatory TNF-alpha and anti-inflammatory/regulatory IL-10 cytokine concentrations were determined in culture supernatants. PRINCIPAL FINDINGS: Infected children produced higher adaptive IL-10 responses than uninfected children against schistosomal antigens (72 h incubation). On the other hand, infected children had higher TNF-alpha responses than uninfected children and significantly higher TNF-alpha to IL-10 ratios in response to FSL-1 and Pam3, ligands of TLR2/6 and TLR2/1 respectively. A similar trend was observed for the TLR4 ligand LPS while Poly(I:C) (Mda5/TLR3 ligand) did not induce substantial cytokine responses (24 h incubation). CONCLUSIONS: This pilot study shows that Schistosoma-infected children develop a more pro-inflammatory TLR2-mediated response in the face of a more anti-inflammatory adaptive immune response. This suggests that S. haematobium infection does not suppress the host's innate immune system in the context of single TLR ligation

Cytokine Responses to Schistosoma mansoni and Schistosoma haematobium in Relation to Infection in a Co-endemic Focus in Northern Senegal

Background In Africa, many areas are co-endemic for the two major Schistosoma species, S. mansoni and S. haematobium. Epidemiological studies have suggested that host immunological factors may play an important role in co-endemic areas. As yet, little is known about differences in host immune responses and possible immunological interactions between S. mansoni and S. haematobium in humans. The aim of this study was to analyze host cytokine responses to antigens from either species in a population from a co-endemic focus, and relate these to S. mansoni and S. haematobium infection. Methodology Whole blood cytokine responses were investigated in a population in the north of Senegal (n = 200). Blood was stimulated for 72 h with schistosomal egg and adult worm antigens of either Schistosoma species. IL-10, IL-5, IFN-γ, TNF-α, and IL-2 production was determined in culture supernatants. A multivariate (i.e. multi-response) approach was used to allow a joint analysis of all cytokines in relation to Schistosoma infection. Principal Findings Schistosoma haematobium egg and worm antigens induced higher cytokine production, suggesting that S. haematobium may be more immunogenic than S. mansoni. However, both infections were strongly associated with similar, modified Th2 cytokine profiles. Conclusions/Significance This study is the first to compare S. mansoni and S. haematobium cytokine responses in one population residing in a co-endemic area. These findings are in line with previous epidemiological studies that also suggested S. haematobium egg and worm stages to be more immunogenic than those of S. mansoni.status: publishe

Characteristics of the cohort by schistosome infection status.

<p>Characteristics of the cohort by schistosome infection status.</p

SSC^hi monocytes bind cercarial E/S and egg E/S material.

<p><b>A</b>). Representative flow cytometry dot plots showing binding of Alexafluor⁴⁸⁸-conjugated cercarial E/S products (0-3hRP), Alexafluor⁴⁸⁸-conjugated egg E/S products (ESP), Alexafluor⁴⁸⁸-conjugated zymosan-coated bio-particles, and Fluorescein-conjugated D-mannose, to SSC^hi monocytes following incubation for 60 mins. Populations of ligand⁺ cells were identified for each ligand via a ligand⁺ gate set relative to cells incubated without antigen (No ligand control). Plots of ligand binding are representative of data accrued from all study participants. Numerical values are the median for binding of each ligand ± the range. <b>B</b>). Data shows the proportions of SSC^hi cells in the ligand⁺ gate for each participant relative to cells from the same individuals incubated without ligands (horizontal bars indicate the median value; Paired Wilcoxon test, ***p<0.001, ligand⁺<i>versus</i> no ligand control, n = 41).</p

CD14^brightCD16⁺ intermediate monocytes from co-infected individuals bind cercarial E/S ligands more efficiently than those from un-infected individuals.

<p><b>A</b>). The proportions of each monocyte sub-set that bound cercarial E/S compared between participants grouped according to schistosome infection status (un-infected, infected and co-infected). Horizontal bars denote mean proportions of ligand⁺ cells for each group. Post-hoc pairwise comparisons (Fisher's least significant difference tests) are shown where ANOVA was significant, *p<0.05, **p<0.01. <b>B</b>). MFI for each sub-set incubated with cercarial E/S illustrating the relative quantity of ligand binding. Bars denote median MFI for each infection group. Post-hoc pairwise Mann Whitney U comparisons are shown where non-parametric Kruskal Wallis tests were significant, *p<0.05, **p<0.01. Cell proportions in the ligand⁺ gate and MFI for cells incubated without ligand were subtracted from those of cells incubated with fluorescently-labelled cercarial E/S products prior to comparison between infection groups.</p

CD14^brightCD16⁺ intermediate monocytes preferentially bind cercarial and egg E/S but not Zymosan or D-mannose.

<p>Proportions of ligand⁺ SSC^hi PBMC subdivided into monocyte sub-sets according to their expression of CD14 and CD16. Binding of <b>A</b>) Alexafluor⁴⁸⁸-conjugated cercarial E/S products, <b>B</b>) Alexafluor⁴⁸⁸-conjugated egg E/S products, <b>C</b>) Alexafluor⁴⁸⁸-conjugated zymosan-coated bio-particles, and <b>D</b>) Fluorescein-conjugated D-mannose, to different monocyte sub-sets following incubation for 60 mins. Populations of ligand⁺ cells were identified for each ligand relative to cells incubated without antigen (<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002817#pntd-0002817-g002" target="_blank">Fig.2A</a>). Data was accrued from all study participants (n = 41; horizontal bars indicating the median value; Paired Wilcoxon test, ***p<0.001, **p<0.01).</p

Cytokine Responses to <i>Schistosoma mansoni</i> and <i>Schistosoma haematobium</i> in Relation to Infection in a Co-endemic Focus in Northern Senegal

<div><p>Background</p><p>In Africa, many areas are co-endemic for the two major <i>Schistosoma</i> species, <i>S. mansoni</i> and <i>S. haematobium</i>. Epidemiological studies have suggested that host immunological factors may play an important role in co-endemic areas. As yet, little is known about differences in host immune responses and possible immunological interactions between <i>S. mansoni</i> and <i>S. haematobium</i> in humans. The aim of this study was to analyze host cytokine responses to antigens from either species in a population from a co-endemic focus, and relate these to <i>S. mansoni</i> and <i>S. haematobium</i> infection.</p><p>Methodology</p><p>Whole blood cytokine responses were investigated in a population in the north of Senegal (n = 200). Blood was stimulated for 72 h with schistosomal egg and adult worm antigens of either <i>Schistosoma</i> species. IL-10, IL-5, IFN-γ, TNF-α, and IL-2 production was determined in culture supernatants. A multivariate (i.e. multi-response) approach was used to allow a joint analysis of all cytokines in relation to <i>Schistosoma</i> infection.</p><p>Principal Findings</p><p><i>Schistosoma haematobium</i> egg and worm antigens induced higher cytokine production, suggesting that <i>S. haematobium</i> may be more immunogenic than <i>S. mansoni</i>. However, both infections were strongly associated with similar, modified Th2 cytokine profiles.</p><p>Conclusions/Significance</p><p>This study is the first to compare <i>S. mansoni</i> and <i>S. haematobium</i> cytokine responses in one population residing in a co-endemic area. These findings are in line with previous epidemiological studies that also suggested <i>S. haematobium</i> egg and worm stages to be more immunogenic than those of <i>S. mansoni</i>.</p></div

Levels of <i>Schistosoma</i>-induced cytokine responses in 72 h whole blood cultures (n = 200).

<p>Blood samples from one individual were divided into five and stimulated with <i>Schistosoma</i> antigens (SEAm, SEAh, AWAm, or AWAh), and with medium only (negative control; see <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0003080#s2" target="_blank">Materials and Methods</a>).</p>a<p>Crude cytokine levels are reported. IQR: Interquartile range (Tukey's hinges).</p>b<p>Wilcoxon Signed Rank test comparing <i>S. mansoni</i>- and <i>S. haematobium</i>-induced cytokine levels within individuals (either for SEA or AWA).</p>c<p><i>Schistosoma</i> egg antigen.</p>d<p>Adult worm antigen.</p

Characteristics of the 6 datasets used for the gender- and age-adjusted spatial analyses.

<p>^a Total study population in the first columns and numbers of cases in subsequent columns.</p