Helminth parasites control host-immune responses by secreting immunomodulatory glycoproteins. Clinical trials and mouse model studies have demonstrated the potential of helminth-derived glycoproteins for the treatment of immune-related diseases, like allergies and autoimmune diseases. Studies are however hampered by the limited availability of native parasite-derived proteins. Moreover, recombinant protein production systems have thus far been unable to reconstitute helminth-like glycosylation essential for the functionality of some helminth glycoproteins. Here we exploited the flexibility of the N-glycosylation machinery of plants to reconstruct the helminth glycoproteins omega-1 and kappa-5, two major constituents of immunomodulatory Schistosoma mansoni soluble egg antigens. Fine-tuning transient co-expression of specific glycosyltransferases in Nicotiana benthamiana enabled the synthesis of Lewis X (LeX) and LDN/LDN-F glycan motifs as found on natural omega-1 and kappa-5, respectively. In vitro and in vivo evaluation of the introduction of native LeX motifs on plant-produced omega-1 confirmed that LeX on omega-1 contributes to the glycoprotein’s Th2-inducing properties. These data indicate that mimicking the complex carbohydrate structures of helminths in plants is a promising strategy to allow targeted evaluation of therapeutic glycoproteins for the treatment of inflammatory disorders. In addition, our results offer perspectives for the development of effective anti-helminthic vaccines by reconstructing native parasite glycoprotein antigens.

Infection with the helminth Schistosoma (S.) mansoni drives the development of interleukin (IL)-10-producing regulatory B (Breg) cells in mice and man, which have the capacity to reduce experimental allergic airway inflammation and are thus of high therapeutic interest. However, both the involved antigen and cellular mechanisms that drive Breg cell development remain to be elucidated. Therefore, we investigated whether S. mansoni soluble egg antigens (SEA) directly interact with B cells to enhance their regulatory potential, or act indirectly on B cells via SEA-modulated macrophage subsets. Intraperitoneal injections of S. mansoni eggs or SEA significantly upregulated IL-10 and CD86 expression by marginal zone B cells. Both B cells as well as macrophages of the splenic marginal zone efficiently bound SEA in vivo, but macrophages were dispensable for Breg cell induction as shown by macrophage depletion with clodronate liposomes. SEA was internalized into acidic cell compartments of B cells and induced a 3-fold increase of IL-10, which was dependent on endosomal acidification and was further enhanced by CD40 ligation. IPSE/alpha-1, one of the major antigens in SEA, was also capable of inducing IL-10 in naïve B cells, which was reproduced by tobacco plant-derived recombinant IPSE. Other major schistosomal antigens, omega-1 and kappa-5, had no effect. SEA depleted of IPSE/alpha-1 was still able to induce Breg cells indicating that SEA contains more Breg cell-inducing components. Importantly, SEA- and IPSE-induced Breg cells triggered regulatory T cell development in vitro. SEA and recombinant IPSE/alpha-1 also induced IL-10 production in human CD1d+ B cells. In conclusion, the mechanism of S. mansoni-induced Breg cell development involves a direct targeting of B cells by SEA components such as the secretory glycoprotein IPSE/alpha-1.

Helminth infections have been suggested to impair the development and outcome of Th1 responses to vaccines and intracellular microorganisms. However, there are limited data regarding the ability of intestinal nematodes to modulate Th1 responses at sites distal to the gut. In this study, we have investigated the effect of the intestinal nematode Heligmosomoides polygyrus bakeri on Th1 responses to Mycobacterium bovis bacillus Calmette–Guérin (BCG). We found that H. polygyrus infection localized to the gut can mute BCG-specific CD4+ T cell priming in both the spleen and skin-draining lymph nodes. Furthermore, H. polygyrus infection reduced the magnitude of delayed-type hypersensitivity (DTH) to PPD in the skin. Consequently, H. polygyrus–infected mice challenged with BCG had a higher mycobacterial load in the liver compared with worm-free mice. The excretory–secretory product from H. polygyrus (HES) was found to dampen IFN-γ production by mycobacteria-specific CD4+ T cells. This inhibition was dependent on the TGF-βR signaling activity of HES, suggesting that TGF-β signaling plays a role in the impaired Th1 responses observed coinfection with worms. Similar to results with mycobacteria, H. polygyrus–infected mice displayed an increase in skin parasite load upon secondary infection with Leishmania major as well as a reduction in DTH responses to Leishmania Ag. We show that a nematode confined to the gut can mute T cell responses to mycobacteria and impair control of secondary infections distal to the gut. The ability of intestinal helminths to reduce DTH responses may have clinical implications for the use of skin test–based diagnosis of microbial infections.

SummaryChronic helminth infection with Schistosoma (S.) mansoni protects against allergic airway inflammation (AAI) in mice and is associated with reduced Th2 responses to inhaled allergens in humans, despite the presence of schistosome‐specific Th2 immunity. Schistosome eggs strongly induce type 2 immunity and allow to study the dynamics of Th2 versus regulatory responses in the absence of worms. Treatment with isolated S. mansoni eggs by i.p. injection prior to induction of AAI to ovalbumin (OVA)/alum led to significantly reduced AAI as assessed by less BAL and lung eosinophilia, less cellular influx into lung tissue, less OVA‐specific Th2 cytokines in lungs and lung‐draining mediastinal lymph nodes and less circulating allergen‐specific IgG1 and IgE antibodies. While OVA‐specific Th2 responses were inhibited, treatment induced a strong systemic Th2 response to the eggs. The protective effect of S. mansoni eggs was unaltered in μMT mice lacking mature (B2) B cells and unaffected by Treg cell depletion using anti‐CD25 blocking antibodies during egg treatment and allergic sensitization. Notably, prophylactic egg treatment resulted in a reduced influx of pro‐inflammatory, monocyte‐derived dendritic cells into lung tissue of allergic mice following challenge. Altogether, S. mansoni eggs can protect against the development of AAI, despite strong egg‐specific Th2 responses.

<b><i>Background:</i></b> An inverse relation between <i>Helicobacter pylori</i> infection and asthma has been shown in epidemiological studies. Infection with <i>H. pylori</i>, or application of an extract of it before or after sensitization, inhibits allergic airway disease in mice. <b><i>Objectives:</i></b> The aim of this study was to investigate the effect of an extract of <i>H. pylori</i> on allergic airway disease induced by repeated allergen exposure in mice that were sensitized and challenged prior to extract application. <b><i>Method:</i></b> C57BL/6 mice were intranasally (i.n.) sensitized and challenged with house dust mite (HDM). After a minimum of 4 weeks, mice received the <i>H. pylori</i> extract intraperitoneally and were rechallenged i.n. with HDM. Allergen-specific antibodies were measured by ELISA. Cells present in the bronchoalveolar lavage fluid and dendritic cell (DC) subsets in the lung tissue were analyzed by flow cytometry. Tissue inflammation and goblet cell hyperplasia were assessed by histology. Cells of the mediastinal lymph node (mLN) were isolated and in vitro restimulated with HDM or <i>H. pylori</i> extract. <b><i>Results:</i></b> Treatment with <i>H. pylori</i> extract before rechallenge reduced allergen-specific IgE, the DC numbers in the tissue, and goblet cell hyperplasia. Cells isolated from mLN of mice treated with the extract produced significantly more IL-10 and IL-17 after in vitro restimulation with HDM. mLN cells of <i>H. pylori-</i>treated mice that were re-exposed to the <i>H. pylori</i> extract produced significantly more interferon gamma. <b><i>Conclusions:</i></b> An extract of <i>H. pylori</i> is effective in reducing mucus production and various features of inflammation in HDM rechallenged mice.

The helminth Schistosoma mansoni (S. mansoni) induces a network of regulatory immune cells, including interleukin (IL)‐10‐producing regulatory B cells (Bregs). However, the signals required for the development and activation of Bregs are not well characterized. Recent reports suggest that helminths induce type I interferons (IFN‐I), and that IFN‐I drive the development of Bregs in humans. We therefore assessed the role of IFN‐I in the induction of Bregs by S. mansoni. Mice chronically infected with S. mansoni or i.v. injected with S. mansoni soluble egg antigen (SEA) developed a systemic IFN‐I signature. Recombinant IFN‐α enhanced IL‐10 production by Bregs stimulated with S. mansoni SEA in vitro, while not activating Bregs by itself. IFN‐I signaling also supported ex vivo IL‐10 production by SEA‐primed Bregs but was dispensable for activation of S. mansoni egg‐induced Bregs in vivo. These data indicate that although IFN‐I can serve as a coactivator for Breg IL‐10 production, they are unlikely to participate in the development of Bregs in response to S. mansoni eggs.

Chronic schistosome infections protect against allergic airway inflammation (AAI) via the induction of IL-10-producing splenic regulatory B (Breg) cells. Previous experiments have demonstrated that schistosome-induced pulmonary B cells can also reduce AAI, but act independently of IL-10. We have now further characterized the phenotype and inhibitory activity of these protective pulmonary B cells. We excluded a role for regulatory T (Treg) cell induction as putative AAI-protective mechanisms. Schistosome-induced B cells showed increased CD86 expression and reduced cytokine expression in response to Toll-like receptor (TLR) ligands compared with control B cells. To investigate the consequences for T cell activation we cultured ovalbumin (OVA)-pulsed, schistosome-induced B cells with OVA-specific transgenic T cells and observed less Th2 cytokine expression and T cell proliferation compared with control conditions. This suppressive effect was preserved even under optimal T cell stimulation by anti-CD3/28. Blocking of the inhibitory cytokines IL-10 or TGF-β only marginally restored Th2 cytokine induction. These data suggest that schistosome-induced pulmonary B cells are impaired in their capacity to produce cytokines to TLR ligands and to induce Th2 cytokine responses independent of their antigen-presenting function. These findings underline the presence of distinct B cell subsets with different stimulatory or inhibitory properties even if induced by the same type of helminth.

Allergic airway disease is a major global health burden, and novel treatment options are urgently needed. Numerous epidemiological and experimental studies suggest that certain helminths and bacteria protect against respiratory allergies. These microorganisms are strong regulators of the immune system, and various potential regulatory mechanisms by which they protect against allergic airway inflammation have been proposed. Whereas early studies addressed the beneficial effect of natural infections, the focus now shifts toward identifying the dominant protective molecules and exploring their efficacy in models of allergic airway disease. In this article, we will review the evidence for microbe-mediated protection from allergic airway disease, the potential modes of action involved and discuss advances as well as limitations in the translation of this knowledge into novel treatment strategies against allergic airway disease.