Gabriele Schramm

Omega-1, a glycoprotein secreted by Schistosoma mansoni eggs, drives Th2 responses

Soluble egg antigens of the parasitic helminth Schistosoma mansoni (S. mansoni egg antigen [SEA]) induce strong Th2 responses both in vitro and in vivo. However, the specific molecules that prime the development of Th2 responses have not been identified. We report that omega-1, a glycoprotein which is secreted from S. mansoni eggs and present in SEA, is capable of conditioning human monocyte-derived dendritic cells in vitro to drive T helper 2 (Th2) polarization with similar characteristics as whole SEA. Furthermore, using IL-4 dual reporter mice, we show that both natural and recombinant omega-1 alone are sufficient to generate Th2 responses in vivo, even in the absence of IL-4R signaling. Finally, omega-1–depleted SEA displays an impaired capacity for Th2 priming in vitro, but not in vivo, suggesting the existence of additional factors within SEA that can compensate for the omega-1–mediated effects. Collectively, we identify omega-1, a single component of SEA, as a potent inducer of Th2 responses.

Molecular Characterization of an Interleukin-4-inducing Factor from Schistosoma mansoni Eggs

The eggs of the parasitic trematodeSchistosoma mansoni are powerful inducers of a T helper type 2 (Th2) immune response and immunoglobulin E (IgE) production.S. mansoni egg extract (SmEA) stimulates human basophils to rapidly release large amounts of interleukin (IL)-4, the key promoter of a Th2 response. Here we show purification and sequence of the IL-4-inducing principle of S. mansoni eggs (IPSE). Stimulation studies with human basophils using SmEA fractions and natural and recombinant IPSE as well as neutralization and immunodepletion studies using antibodies to recombinant IPSE demonstrate that IPSE is the bioactive principle in SmEA leading to activation of basophils and to expression of IL-4 and IL-13. Regarding the mechanism of action, blot analysis showed that IPSE is an IgE-binding factor, suggesting that it becomes effective via cross-linking receptor-bound IgE on basophils. Immunohistology revealed that IPSE is enriched in and secreted from the subshell area of the schistosome egg. We conclude from these data that IPSE may be an important parasite-derived component for skewing the immune response toward Th2.

Cutting Edge: IPSE/alpha-1, a Glycoprotein from Schistosoma mansoni Eggs, Induces IgE-Dependent, Antigen-Independent IL-4 Production by Murine Basophils In Vivo

During infection with the helminth parasite Schistosoma mansoni, the deposition of eggs coincides with the onset of IL-4 production and Th2 development. Although IL-4 is known as a potent inducer of Th2 differentiation, the mechanism by which schistosome eggs induce IL-4 production is not clear. In this study, we demonstrate that the S. mansoni egg Ag (SmEA) induces IgE-dependent IL-4 production by basophils derived from Heligmosomoides polygyrus-infected or OVA/alum-immunized mice in the absence of pathogen-specific IgE. The effect is mediated by the secretory glycoprotein IPSE/alpha-1, because IPSE/alpha-1-depleted SmEA no longer induces cytokine production. Conversely, recombinant IPSE/alpha-1 is sufficient to induce IL-4 production. Importantly, the injection of SmEA or recombinant IPSE/alpha-1 into H. polygyrus-infected 4get/KN2 IL-4 reporter mice rapidly induces the dose-dependent IL-4 production by basophils in the liver, a major site of egg deposition. Thus, IPSE/alpha-1 induces basophils to produce IL-4 even in the absence of Ag-specific IgE.

Schistosome-derived omega-1 drives Th2 polarization by suppressing protein synthesis following internalization by the mannose receptor

Schistosome ribonuclease Omega-1 primes DCs to generate Th2 responses by binding and internalization by the mannose receptor and by subsequently impairing protein synthesis.

Dietary lectins can induce in vitro release of IL-4 and IL-13 from human basophils

Dietary lectins, present in beans and other edible plant products, pose a potential threat to consumers due to their capacity to induce histamine release from basophils. In this study, we analyzed the capacity of 16 common, in particular dietary, lectins to induce human basophils to secrete IL‐4 and IL‐13, the key promoters of Th2 responses and IgE synthesis. Several of the lectins, especially concanavalin A, lentil lectin, phytohemagglutinin, Pisum sativum agglutinin and Sambucus nigra agglutinin, triggered basophils to release IL‐4 at concentrations of up to 1 ng / 106 basophils. Lectins with high IL‐4‐inducing capacity also stimulated the release of IL‐13 and histamine. Lectin‐induced IL‐4 and IL‐13 release reached a maximum after 4 – 6 h and more than 18 h, respectively. Affinoblotting revealed that lectins with the capacity to induce mediator release bind to IgE, suggesting IgE binding as initial step of signal generation. In conclusion, several dietary lectins can trigger human basophils to release IL‐4 and IL‐13. Since lectins can enter the circulation after oral uptake, they might play a role in inducing the so‐called early IL‐4 required to switch the immune response towards a Th2 response and type I allergy.

IPSE/alpha-1, a major secretory glycoprotein antigen from schistosome eggs, expresses the Lewis X motif on core-difucosylated N-glycans

Schistosomes are parasitic flatworms that infect millions of people in (sub)tropical areas around the world. Glycoconjugates of schistosomes play a critical role in the interaction of the different developmental stages of the parasite with the host. In particular, glycosylated components of the eggs produced by the adult worm pairs living in the bloodstream are strongly immunogenic. We have investigated the glycosylation of interleukin‐4‐inducing factor from schistosome eggs (IPSE/alpha‐1), a major secretory egg antigen from Schistosoma mansoni that triggers interleukin‐4 production in human basophils, by MS analysis of tryptic glycopeptides. Nanoscale LC‐MS(/MS) and MALDI‐TOF(/TOF)‐MS studies combined with enzymatic degradations showed that monomeric IPSE/alpha‐1 contains two N‐glycosylation sites, which are each occupied for a large proportion with core‐difucosylated diantennary glycans that carry one or more Lewis X motifs. Lewis X has been reported as a major immunogenic glycan element of schistosomes. This is the first report both on the expression of Lewis X on a specific schistosome egg protein and on a protein‐specific glycosylation analysis of schistosome eggs.

Major allergen Phl p Vb in timothy grass is a novel pollen RNase

A cDNA coding for the major group V allergen Phl p Vb was isolated from a timothy grass pollen cDNA library by immunoscreening with a specific monoclonal antibody. It was discovered for the first time that the recombinant Phl p Vb pollen allergen after expression and purification has ribonuclease activity. High homology of Phl p Vb to other group V allergens in grass pollen indicates similar function. By RNase activity gel of natural pollen extract of timothy grass and consecutive Western blot analysis of the excised proteins, the RNase active bands were shown to be group V allergens. Additionally it was demonstrated that an homologous protein to Phl p Vb in the mother plant could be induced by salicylic acid. This indicates that group Vb allergens may be involved in host‐pathogen interactions because in pollen they are quickly exported RNases and in the mother plant they depend on a hormone which is related to expression of plant resistance genes.

Post-translational modifications influence IgE reactivity to the major allergen Phl p 1 of timothy grass pollen.

Grass group I consists of very potent allergenic components which are found in the pollen of all temperate grasses. Several post‐translational modifications are predicted from the cDNA data.

The S. mansoni glycoprotein ω-1 induces Foxp3 expression in NOD mouse CD4+ T cells

Immunization with Schistosoma mansoni soluble antigen preparations protects non‐obese diabetic (NOD) mice against the development of type 1 diabetes. These preparations have long been known to induce Th2 responses in vitro and in vivo. Recently, two separate groups have reported that ω‐1, a well‐characterized glycoprotein in S. mansoni soluble egg antigens (SEA), which with IL‐4 inducing principle of S. mansoni eggs (IPSE/α‐1) is one of the two major glycoproteins secreted by live eggs, is a major SEA component responsible for this effect. We found that ω‐1 induces Foxp3 as well as IL‐4 expression when injected in vivo. We confirmed that ω‐1 conditions DCs to drive Th2 responses and further demonstrated that ω‐1 induces Foxp3+ T cells from NOD mouse naïve T cells. In contrast, IPSE/α‐1 did not drive Foxp3 responses. The in vitro development of Foxp3‐expressing T cells by ω‐1 was TGF‐β‐ and retinoic acid‐dependent. Our work, therefore, identifies ω‐1 as an important factor for the induction of Foxp3+ T cells by SEA in NOD mice.

Structural investigations of the major allergen Phl p I on the complementary DNA and protein level

Until now investigations of group I grass allergens have mainly been performed on ryegrass allergen (Lol p I). We studied this major allergen grass group with timothy grass pollen (Phl p I), a very common and important cause of type I allergy, to determine intraspecific and interspecific variations among different grass species. By immunoscreening a timothy grass pollen complementary DNA library we obtained three full-length clones. They revealed identical nucleotide sequences in the coding regions consisting of 262 amino acids, including a leader sequence of 23 amino acid residues. The comparison of our data with the amino acid sequences deduced from Lol p I and Hol 1 I clones showed sequence identities of greater than 85% and homologies of greater than 90%, indicating a high degree of sequence conservation. Despite the high degree of homology, amino acid differences were in immunodominant positions, which may be responsible for the differing immune response to group I allergens of different grass species.