AI Article Synopsis

  • Viral infections can lead to lower platelet counts, and this study reveals that the encephalomyocarditis virus (EMCV) triggers this drop primarily through platelet Toll-like receptor 7 (TLR7).
  • TLR7 activation causes platelets to form large aggregates with neutrophils, leading to the internalization of platelet fragments by neutrophils without affecting platelet clotting ability.
  • The research indicates that TLR7's role in platelet responses to viral infections can affect overall survival, showing that this interaction between platelets and viruses goes beyond just clotting functions.

Article Abstract

Viral infections have been associated with reduced platelet counts, the biological significance of which has remained elusive. Here, we show that infection with encephalomyocarditis virus (EMCV) rapidly reduces platelet count, and this response is attributed to platelet Toll-like receptor 7 (TLR7). Platelet-TLR7 stimulation mediates formation of large platelet-neutrophil aggregates, both in mouse and human blood. Intriguingly, this process results in internalization of platelet CD41-fragments by neutrophils, as assessed biochemically and visualized by microscopy, with no influence on platelet prothrombotic properties. The mechanism includes TLR7-mediated platelet granule release, translocation of P-selectin to the cell surface, and a consequent increase in platelet-neutrophil adhesion. Viral infection of platelet-depleted mice also led to increased mortality. Transfusion of wild-type, TLR7-expressing platelets into TLR7-deficient mice caused a drop in platelet count and increased survival post EMCV infection. Thus, this study identifies a new link between platelets and their response to single-stranded RNA viruses that involves activation of TLR7. Finally, platelet-TLR7 stimulation is independent of thrombosis and has implications to the host immune response and survival.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4118487PMC
http://dx.doi.org/10.1182/blood-2013-11-536003DOI Listing

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