Bacteria fighter downs dengue fever

DUKE (US) — Cells that help the body ward off bacteria and pathogens do double duty by also recognizing viruses in time to create an immune response.

“It appears the mast cells are activated and call immune system cells to the skin where they clear infection, which limits the spread of infection in the host,” says Ashley St. John, a research fellow at Duke University.
St. John and colleagues chose to study the dengue virus because mosquitoes inject the virus through the skin, which is rich in mast cells.

The study findings are published online in the journal Proceedings of the National Academy of Sciences.

Mice lacking mast cells had more of the dengue virus in their lymph nodes and increased infection after measured injection with a small dose, compared to mice with normal levels of mast cells. Mast cells produce chemokines, which in turn help to bring some special killer cells into the infected skin to fight and contain the virus.

“It was an important discovery for the field to learn that mast cells could be activated by pathogens like bacteria or parasites,” St. John says. “We were excited to learn that mast cells also respond to and promote the clearance of a viral infection.”

The finding is important because “to date there are no vaccines or effective therapies for dengue fever,” says senior author Soman Abraham, professor of pathology.

Because mast cells are involved in airway reactions, as during an asthma attack, this new finding might also help scientists study viral infection in the lungs, airways, and sinuses. Other mosquito-borne viruses, like West Nile, could also be studied in terms of mast-cell response.

Because mast cells can be deliberately activated and also shut down with small molecules, different approaches can be studied.

“Now that we know mast cells can recognize viruses, we can better understand how that infection process begins,” Abraham says. “Knowing the important role of mast cells in viral infections could help find ways to prevent these infections, perhaps in the form of vaccines.”

The work was supported by start-up funds from Duke-NUS Graduate Medical School, with additional funding by U.S. National Institutes of Health.

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