Innate immune recognition of an AT-rich stem-loop DNA motif in the Plasmodium falciparum genome

Shrutie Sharma, University of Massachusetts Medical School
Rosane B. DeOliveira, University of Massachusetts Medical School
Parisa Kalantari, University of Massachusetts Medical School
Peggy Parroche, University of Massachusetts Medical School
Nadege Goutagny, University of Massachusetts Medical School
Zhaozhao Jiang, University of Massachusetts Medical School
Jennie Chan, University of Massachusetts Medical School
Daniella C. Bartholomeu, Federal University of Minas Gerais
Fanny N. Lauw, University of Massachusetts Medical School
J. Perry Hall, University of Massachusetts Medical School
Glen N. Barber, University of Miami School of Medicine
Ricardo T. Gazzinelli, University of Massachusetts Medical School
Katherine A. Fitzgerald, University of Massachusetts Medical School
Douglas T. Golenbock, University of Massachusetts Medical School

Abstract

Although Toll-like receptor 9 (TLR9) has been implicated in cytokine and type I interferon (IFN) production during malaria in humans and mice, the high AT content of the Plasmodium falciparum genome prompted us to examine the possibility that malarial DNA triggered TLR9-independent pathways. Over 6000 ATTTTTAC ("AT-rich") motifs are present in the genome of P. falciparum, which we show here potently induce type I IFNs. Parasite DNA, parasitized erythrocytes and oligonucleotides containing the AT-rich motif induce type I IFNs via a pathway that did not involve the previously described sensors TLR9, DAI, RNA polymerase-III or IFI16/p204. Rather, AT-rich DNA sensing involved an unknown receptor that coupled to the STING, TBK1 and IRF3-IRF7 signaling pathway. Mice lacking IRF3, IRF7, the kinase TBK1 or the type I IFN receptor were resistant to otherwise lethal cerebral malaria. Collectively, these observations implicate AT-rich DNA sensing via STING, TBK1 and IRF3-IRF7 in P. falciparum malaria.