Community deworming alleviates geohelminth-induced immune hyporesponsiveness

In cross-sectional studies, chronic helminth infections have been associated with immunological hyporesponsiveness that can affect responses to unrelated antigens. To study the immunological effects of deworming, we conducted a cluster-randomized, double-blind, placebo-controlled trial in Indonesia and assigned 954 households to receive albendazole or placebo once every 3 mo for 2 y. Helminth-specific and nonspecific whole-blood cytokine responses were assessed in 1,059 subjects of all ages, whereas phenotyping of regulatory molecules was undertaken in 121 school-aged children. All measurements were performed before and at 9 and 21 mo after initiation of treatment. Anthelmintic treatment resulted in significant increases in proinflammatory cytokine responses to Plasmodium falciparum-infected red blood cells (PfRBCs) and mitogen, with the largest effect on TNF responses to PfRBCs at 9 mo—estimate [95% confidence interval], 0.37 [0.21–0.53], P value over time (Ptime) < 0.0001. Although the frequency of regulatory T cells did not change after treatment, there was a significant decline in the expression of the inhibitory molecule cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) on CD4+ T cells of albendazole-treated individuals, –0.060 [–0.107 to –0.013] and –0.057 [–0.105 to –0.008] at 9 and 21 mo, respectively; Ptime = 0.017. This trial shows the capacity of helminths to up-regulate inhibitory molecules and to suppress proinflammatory immune responses in humans. This could help to explain the inferior immunological responses to vaccines and lower prevalence of inflammatory diseases in low- compared with high-income countries

New insights into the kinetics and variability of egg excretion in controlled human hookworm infections

Four healthy volunteers were infected with 50 Necator americanus infective larvae (L3) in a controlled human hookworm infection trial and followed for 52 weeks. The kinetics of fecal egg counts in volunteers was assessed with Bayesian multilevel analysis, which revealed an increase between weeks 7 and 13, followed by an egg density plateau of about 1000 eggs/g of feces. Variation in egg counts was minimal between same-day measurements but varied considerably between days, particularly during the plateau phase. These analyses pave the way for the controlled human hookworm model to accelerate drug and vaccine efficacy studies

Lower Expression of TLR2 and SOCS-3 Is Associated with Schistosoma haematobium Infection and with Lower Risk for Allergic Reactivity in Children Living in a Rural Area in Ghana

Inflammatory diseases such as atopic disorders are a major health problem in the Western world, but their prevalence is also increasing in developing countries, especially in urban centres. There is increasing evidence that exposure to a rural environment with high burden of compounds derived from parasites and microorganisms is associated with protection from atopic disorders. Since urbanisation is progressing at a rapid pace, particularly in less-developed nations, there is a need to understand the molecular processes that control the progress towards the development of allergic diseases in developing countries. In this study we have examined a population of school children living in a rural area of Ghana, where helminth (worm) infections are prevalent and associated with protection from skin reactivity to house dust mite. Blood samples were collected from these children and analysed for the expression levels of several genes involved in the development of a pro allergic immune system. The results point at a potential molecular link that might explain the negative association between schistosome infections and allergies

The development of TH2 responses from infancy to 4 years of age and atopic sensitization in areas endemic for helminth infections

BACKGROUND: Helminth infections and allergies are associated with TH(2) responses. Whereas the development of TH(2) responses and allergic disorders in pediatric populations has been examined in affluent countries, no or little data exist from low income regions of the world. The aim of this study is to examine factors influencing the development of TH(2) responses of children born in areas endemic for helminth infections and to relate these factors to atopic sensitization at 4 years of age. METHODS: Data were collected from pregnant mothers on helminth infections, education and socioeconomic status (SES). Total IgE, IL-5 in response to mitogen, and helminth antigens were measured in children at 2, 5, 12, 24 and 48 months of age. Skin prick testing (SPT) and allergen-specific IgE were determined at 4 years of age. RESULTS: Strong TH(2) responses were seen at 5 months of age and increased with time. Although maternal filarial infection was associated with helminth-antigen specific TH(2) responses, it was low maternal education or SES but not helminth infection, which was associated with the development of high total IgE and PHA-induced IL-5. At 4 years of age when allergen reactivity was assessed by SPT, the high general TH(2) responses did not translate into higher prevalence of SPT. The risk factor for SPT reactivity was low maternal education which decreased the risk of SPT positivity to allergens (adjusted OR, 0.32; 95% CI, 0.12 – 0.87) independently of maternal filarial infection which tended to reduce the child’s risk for being SPT positive (adjusted OR, 0.35; 95% CI, 0.07 – 1.70). CONCLUSIONS: In areas endemic for helminths, potent TH(2) responses were seen early in life, but did not translate into a higher SPT reactivity to allergens. Therefore, in many parts of the world TH(2) responses in general and IgE in particular cannot be used for diagnosis of allergic diseases

Functional Impairment of Human Myeloid Dendritic Cells during Schistosoma haematobium Infection

Chronic Schistosoma infection is often characterized by a state of T cell hyporesponsiveness of the host. Suppression of dendritic cell (DC) function could be one of the mechanisms underlying this phenomenon, since Schistosoma antigens are potent modulators of dendritic cell function in vitro. Yet, it remains to be established whether DC function is modulated during chronic human Schistosoma infection in vivo. To address this question, the effect of Schistosoma haematobium infection on the function of human blood DC was evaluated. We found that plasmacytoid (pDC) and myeloid DC (mDC) from infected subjects were present at lower frequencies in peripheral blood and that mDC displayed lower expression levels of HLA-DR compared to those from uninfected individuals. Furthermore, mDC from infected subjects, but not pDC, were found to have a reduced capacity to respond to TLR ligands, as determined by MAPK signaling, cytokine production and expression of maturation markers. Moreover, the T cell activating capacity of TLR-matured mDC from infected subjects was lower, likely as a result of reduced HLA-DR expression. Collectively these data show that S. haematobium infection is associated with functional impairment of human DC function in vivo and provide new insights into the underlying mechanisms of T cell hyporesponsiveness during chronic schistosomiasis

CD39 and immune regulation in a chronic helminth infection: The puzzling case of <i>Mansonella ozzardi</i>

<div><p>Background</p><p>Chronic helminth infections typically induce an immunoregulatory environment, with markedly reduced immune responses to both parasite-specific and unrelated bystander antigens. Here we tested whether these changes are also observed in human infections with <i>Mansonella ozzardi</i>, a neglected filarial nematode widely distributed across Latin America.</p><p>Methods</p><p>CD4⁺ T cell populations from microfilaremic (Fil+) and uninfected (Fil-) inhabitants in <i>M</i>. <i>ozzardi</i>-endemic riverine communities in Brazil were characterized by flow cytometry analysis. Plasma concentrations of a wide range of cytokines and chemokines were measured. We examined whether <i>M</i>. <i>ozzardi</i> infection is associated with suppressed <i>in vitro</i> lymphoproliferative and inflammatory cytokine responses upon stimulation with filarial antigen, unrelated antigens or mitogens.</p><p>Principal findings/Conclusions</p><p>Fil+ subjects had lower plasma levels of selected inflammatory cytokines, such as TNF-α, IL-8, and IL-6, than their Fil- counterparts. However, we found no evidence for attenuated T-cell responses to filarial antigens or co-endemic pathogens, such as malaria parasites and <i>Toxoplasma gondii</i>. CD4⁺ T cells expressing CD39, an ectonucleosidase involved in the generation of the anti-inflammatory molecule adenosine, were increased in frequency in Fil+ subjects, compared to uninfected controls. Significantly, such an expansion was directly proportional to microfilarial loads. Surprisingly, CD39 blocking with a neutralizing antibody suppressed antigen-driven lymphoproliferation <i>in vitro</i>, while decreasing inflammatory cytokine responses, in Fil+ and Fil- individuals. These findings suggest that circulating CD4⁺ CD39⁺ T cells comprise subsets with both regulatory and stimulatory roles that contribute to the immune homeostasis in chronic <i>M</i>. <i>ozzardi</i> infection.</p></div

The expansion of CD4⁺CD39⁺ T-cell populations in microfilaremics is directly proportional to their microfilarial load.

<p>The frequencies of CD4⁺CD39⁺ T cells (% of all CD4⁺ T cells that express CD39; upper panel) and CD39⁺ Treg cells (% of all CD4⁺CD25^hiCD127^-FoxP3⁺ T cells that express CD39; lower panel) were plotted against the number of <i>Mansonella ozzardi</i>-specific ITS-2 amplicon copies obtained by quantitative real-time PCR, a proxy of microfilarial load. Data analyzed for 48 subjects using the Spearman rank correlation test.</p

Frequency of CD4⁺ T cells expressing regulation and activation markers in microfilaremic subjects (Fil+) and uninfected controls (Fil-).

<p>Frequency of CD4⁺ T cells expressing regulation and activation markers in microfilaremic subjects (Fil+) and uninfected controls (Fil-).</p

Antigen-driven lymphocyte proliferation is not suppressed in <i>Mansonella ozzardi</i> infection.

<p>PBMC from microfilaremic (Fil+) and uninfected (Fil-) subjects were labeled with CellTrace Violet and incubated with filarial (<i>B</i>. <i>malayi</i> adult worm extract [BmA]) and unrelated antigens (<i>Staphylococcus aureus</i> enterotoxin B [SEB], <i>Toxoplasma gondii</i> taquizoite extract [TgT] and red blood cells infected with <i>Plasmodium vivax</i> schizonts [PvS]), mitogen (phytohemagglutinin [PHA-P]), or medium alone (“unstimulated”). The net % of divided cells (stimulated minus unstimulated) was estimated by flow cytometry and shown in all panels, except for the lower right panel, which shows % of unstimulated divided cells. Data are presented as medians and interquartile ranges for 20 Fil+ and 10 Fil- subjects (TgT, PvS, and PHA-P) or 36 Fil+ subjects and 23 Fil- subjects (BmA, SEB, and medium alone) and were compared using the Mann-Whitney <i>U</i> test. The only significant <i>P</i> value after controlling for a false discovery rate (<i>q</i>) set at 0.10 is shown (number of comparisons <i>m</i> = 6).</p

CD39 blocking alters antigen-driven cytokine production by CD4⁺ T cells.

<p>PBMC from microfilaremic (Fil+) and uninfected (Fil-) subjects were stimulated with <i>Staphylococcus aureus</i> enterotoxin B (SEB) in the presence or absence of anti-CD39 antibody and stained for intracellular cytokines. The % of CD4⁺ T cells producing each cytokine was estimated by flow cytometry. Individual data are presented for 40 Fil+ and 28 Fil- subjects and were compared using the Wilcoxon signed rank test. Significant <i>P</i> values after controlling for a false discovery rate (<i>q</i>) set at 0.10 are underlined (number of comparisons <i>m</i> = 5 for each group, Fil+ and Fil-).</p