Parasitic worms release tiny sacs filled with small RNAs that disable immune responses in infected mice.
The membrane-bound sacs, or exosomes, sprout from cells and contain proteins and nucleic acids. Amy Buck at the University of Edinburgh, UK, and her team found that the nematode Heligmosomoides polygyrus, which infects the mouse gut, produces exosomes containing microRNAs (miRNAs) and 'Y RNAs' that can affect gene expression. The exosomes also carried a protein required to process those RNAs.
Mice exposed to exosomes showed a reduced immune response to an allergen compared to unexposed mice. The sacs also lowered expression of some immune-related genes in mouse cells in a lab dish. Moreover, the animals had miRNA from another worm called Litomosoides sigmodontis in their blood, suggesting that miRNA is secreted by other nematodes.
Nature Commun. 5, 5488 (2014)