The ROP16III-dependent early immune response determines the subacute CNS immune response and type III Toxoplasma gondii survival
Kochanowsky, Joshua A.
Koshy, Anita A.
AffiliationUniv Arizona, UBRP
Univ Arizona, Dept Immunobiol
Univ Arizona, Bio5 Inst
Univ Arizona, Dept Neurol
MetadataShow full item record
PublisherPUBLIC LIBRARY SCIENCE
CitationTuladhar S, Kochanowsky JA, Bhaskara A, Ghotmi Y, Chandrasekaran S, Koshy AA (2019) The ROP16III-dependent early immune response determines the subacute CNS immune response and type III Toxoplasma gondii survival. PLoS Pathog 15(10): e1007856. https://doi.org/10.1371/journal.ppat.1007856
RightsCopyright © 2019 Tuladhar et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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AbstractToxoplasma gondii is an intracellular parasite that persistently infects the CNS and that has genetically distinct strains which provoke different acute immune responses. How differences in the acute immune response affect the CNS immune response is unknown. To address this question, we used two persistent Toxoplasma strains (type II and type III) and examined the CNS immune response at 21 days post infection (dpi). Contrary to acute infection studies, type III-infected mice had higher numbers of total CNS T cells and macrophages/microglia but fewer alternatively activated macrophages (M2s) and regulatory T cells (Tregs) than type II-infected mice. By profiling splenocytes at 5, 10, and 21 dpi, we determined that at 5 dpi type III-infected mice had more M2s while type II-infected mice had more pro-inflammatory macrophages and that these responses flipped over time. To test how these early differences influence the CNS immune response, we engineered the type III strain to lack ROP16 (IIIΔrop16), the polymorphic effector protein that drives the early type III-associated M2 response. IIIΔrop16-infected mice showed a type II-like neuroinflammatory response with fewer infiltrating T cells and macrophages/microglia and more M2s and an unexpectedly low CNS parasite burden. At 5 dpi, IIIΔrop16-infected mice showed a mixed inflammatory response with more pro-inflammatory macrophages, M2s, T effector cells, and Tregs, and decreased rates of infection of peritoneal exudative cells (PECs). These data suggested that type III parasites need the early ROP16-associated M2 response to avoid clearance, possibly by the Immunity-Related GTPases (IRGs), which are IFN-γ- dependent proteins essential for murine defenses against Toxoplasma. To test this possibility, we infected IRG-deficient mice and found that IIIΔrop16 parasites now maintained parental levels of PECs infection. Collectively, these studies suggest that, for the type III strain, rop16III plays a key role in parasite persistence and influences the subacute CNS immune response.
NoteOpen access journal
VersionFinal published version
SponsorsMarch of Dimes [5-FY15-45]; Arizona Biomedical Research Centre [ADHS14-082991]; National Institute of Neurologic Disorders and Stroke - United States Department of Health & Human Services - National Institutes of Health (NIH) - USANIH National Institute of Neurological Disorders & Stroke (NINDS) [NS095994-02S1]; American Heart Association [16PRE30990019]; United States Department of Health & Human Services - National Institutes of Health (NIH) - USA NIH National Institute of Allergy & Infectious Diseases (NIAID) [F31AI147711]; Howard Hughes Medical Institute - Howard Hughes Medical Institute ; BIO5 Institute, University of Arizona; National Cancer Institute (UA Flow Cytometry Shared Resource, UA Cancer Center) [P30CA023074]
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