The Schistosoma mansoni T2 ribonuclease omega-1 modulates inflammasome-dependent IL-1ß secretion in macrophages.

The T2 ribonuclease omega-1 is a powerful Th2-inducing factor secreted by the eggs of the blood fluke Schistosoma mansoni. Omega-1 can modulate pattern recognition receptor-induced inflammatory signatures and alter antigen presentation by dendritic cells. Recent findings have suggested that component(s) contained in or secreted by S. mansoni eggs (soluble egg antigen) can also enhance IL-1ß secretion by dendritic cells stimulated with pattern recognition receptor ligands. Here we show that omega-1 enhances IL-1ß secretion in macrophages stimulated with Toll-like receptor 2 ligand, and propose omega-1 as the factor in soluble egg antigen capable of regulating inflammasome activity. This effect is dependent on the C-type lectin receptor Dectin-1, caspase-8 and the ASC inflammasome adaptor protein, highlighting the ability of omega-1 to regulate multiple pattern recognition receptor signalling pathways. These mechanistic insights into manipulation of host immunity by a parasite product have implications for the design of anti-inflammatory therapeutic drugs.

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-ß- 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.