Name of Student:
Ulrike Lambertz
Research Supervisor: Dr. Neil Reiner
Title of Presentation: The role of exosomal RNA in leishmania pathogenesis
Abstract
A major hallmark of infection with leishmania is the persistence of organisms within host
macrophages (MΦs) brought about by manipulation of cellular functions. Evidence has
suggested that impairment of MΦ microbicidal functions is linked to export of leishmaniaderived virulence factors into host cytosol. Consistent with this, our group recently
demonstrated that leishmania secrete known and candidate protein virulence factors as cargo
of exosomes. Importantly, exosomes released from leishmania were taken up by MΦ and had
immuno-modulatory effects on host myeloid cells.
It has also been shown that exosomes released from mammalian cells contain RNA molecules.
Moreover, virus-infected cells were observed to release exosomes containing virally encoded
small regulatory RNAs, which mediated posttranscriptional gene silencing in target cells.
Based on these findings, we hypothesized that leishmania exosomes, in addition to proteins,
may also contain parasite-derived RNA and that these molecules contribute to leishmania
pathogenesis.
Indeed, using radiolabeling, gel electrophoresis as well as Agilent Bioanalyzer analysis, we
have shown that leishmania exosomes do in fact contain RNA. Interestingly, the size range of
exosomal RNA was considerably narrower than that of total leishmania RNA, with the
majority of sequences being shorter than 200 nt. Exosomal RNA was protected from
degradation by exogenous RNases. Furthermore, by Sanger sequencing we identified a
common 12 nt motif in 80% of the RNA sequences found in exosomes. We are currently
characterizing leishmania exosomal RNA by 454 pyrosequencing. Future studies will focus
on investigating the effects of leishmania exosomal RNA on host cells.