Schistosomal extracellular vesicle‐enclosed miRNAs modulate host T helper cell differentiation

Abstract

During the chronic stage of Schistosoma infection, the female lays fertile eggs, triggering a strong anti‐parasitic type 2 helper T‐cell (Th2) immune response. It is unclear how this Th2 response gradually declines even though the worms live for years and continue to produce eggs. Here, we show that Schistosoma mansoni downregulates Th2 differentiation in an antigen‐presenting cell‐independent manner, by modulating the Th2‐specific transcriptional program. Adult schistosomes secrete mi RNA ‐harboring extracellular vesicles that are internalized by Th cells in vitro . Schistosomal mi RNA s are found also in T helper cells isolated from Peyer's patches and mesenteric lymph nodes of infected mice. In T helper cells, the schistosomal miR‐10 targets MAP 3K7 and consequently downmodulates NF ‐κ B activity, a critical transcription factor for Th2 differentiation and function. Our results explain, at least partially, how schistosomes tune down the Th2 response, and provide further insight into the reciprocal geographic distribution between high prevalence of parasitic infections and immune disorders such as allergy. Furthermore, this worm‐host crosstalk mechanism can be harnessed to develop diagnostic and therapeutic approaches for human schistosomiasis and Th2‐associated diseases. image During chronic Schistosoma infection a strong anti‐parasitic Th2‐type immune response is triggered. The parasite counteracts this by releasing extracellular vesicles that contain mi RNA s that modulate Th2 differentiation. Schistosomes preferentially interfere with Th2‐specific differentiation pathways. Schistosomal miRNAs secreted via extracellular vesicles taken up by T helper cells block Th2 differentiation. The schistosomal miR‐10 targets MAP3K7 and inhibits NF‐κB activity, essential for Th2 differentiation. Parasite‐driven silencing of the Th2 pathway may explain the chronicity of schistosomal infection.