A study published online on February 1 in the Journal of Experimental Medicine (www.jem.org) shows that antiviral proteins called type I interferons (IFNs) are needed to fend off infection with an exotic mosquito-borne virus called Chikungunya virus. This pathogen, which causes high fevers and severe joint pain, triggered a recent epidemic in Southeast Asia, infecting more than 30% of the population in some areas.

A team led by Marc Lecuit and Matthew Albert at the Pasteur Institute in Paris found that individuals infected with Chikungunya virus had increased levels of type I IFNs in their blood. But the source of the virus-fighting IFN proteins came as a surprise. Viruses related to Chikungunya trigger type I IFN production mostly from immune cells. But during Chikungunya infection, immune cells neither produced nor responded to type I IFNs. Rather non-immune cells called fibroblasts—the main target of virus infection—provided the essential type I IFN.

This unique feature should be taken into consideration in future efforts to develop therapeutic strategies for controlling Chikungunya virus infection.