Sand flyWIKIMEDIA, JAMES GATHANYProtozoan parasites of the Leishmania genus cause leishmaniasis—a spectrum of diseases that can be disfiguring, debilitating or even deadly. Residing in the guts of blood-sucking sand flies, the parasites are transmitted to humans and other mammals when the flies bite. Now, scientists have discovered that, along with the parasites, the flies expel parasite-derived vesicles called exosomes into their mammalian hosts. According to a paper published in Cell Reports today (October 22), these exosomes ramp up inflammation and boost parasite numbers during infection.
“[The work] adds to the collection of vector-associated factors that promote infection following transmission of Leishmania by sand fly bite,” said parasite biologist David Sacks of the National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda, Maryland, who was not involved in the study. “It reinforces the point that sand flies are not just flying syringes, they don’t just deposit parasites and nothing else.”
Indeed, aside from regurgitating parasites into a mammal’s skin when it feeds, a sand fly spews salivary proteins, a parasite-secreted gel, and other factors, all of which influence the development of infection and outcome of disease, explained microbiologist and immunologist Nathan Peters of the University of Calgary who also did not participate in the study.
The release of exosomes—small vesicles ...
