Graham Beards / Wikimedia Commons
Disease pathogen alters the function of platelets (in purple)Graham Beards / Wikimedia CommonsThe dengue virus, which causes the world’s most prevalent hemorrhagic disease—90 million new infections each year—alters the function of blood platelets, the cells that coagulate blood. This effect, identified by researchers at the Oswaldo Cruz Foundation (Fiocruz) in Rio de Janeiro, occurs in addition to other changes previously attributed to the action of the virus. Scientists have known for some time that the virus causes a significant decrease in blood platelet concentration, thereby raising the risk of hemorrhage. Without a sufficient quantity of these cells—which are actually fragments of bone marrow cells, the body loses the ability to stop blood loss from broken blood vessels. But the manner in which the virus affected platelet activity was unknown. In attempting to find how the virus affects platelets, the group at Fiocruz led by Jonas Perales and Patrícia Bozza decided to compare the protein profile (proteome) of platelets from dengue patients with the profile of platelets from healthy individuals. Of the nearly 3,400 proteins mapped, 252 were differentially expressed (produced in greater or lesser quantity) in the platelets of dengue patients. The proteomic analysis indicated that, following contact with the virus, the platelets became active and began to sequester proteins from the blood, contributing to further platelet activation. They also began to store and release inflammatory molecules into the bloodstream. “These inflammatory cytokines and chemokines appear to work together to aggravate the clinical condition,” says researcher Monique Trugilho, first author of the study (PLOS Pathogens, May 2017). The group also found that contact with the virus induces in the platelets a potential new function that was once considered exclusive to immune cells: the platelets may be able to degrade viral proteins, send the protein fragments to the surface and introduce them into other cells, triggering an immune response. “Additional experiments are needed to confirm whether this occurs, but proteomic analysis indicates that the platelets have the proteins necessary to perform that function,” Trugilho says.
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