Why Portland Oregon is a Great Place to Study Dengue, Zika, and Chikungunya

Posted 15 November 2016

Portland Oregon is well known for its beautiful parks and urban hipster culture. But here’s something that has not been featured on an episode of the popular TV show Portlandia: It turns out Portland is also a great place to study exposures to dengue, chikungunya and possibly Zika as well.
No, these diseases are not rampant in the Northwest. But William Messer, MD, PhD, at the Oregon Health and Sciences University (OHSU), has taken advantage of the city’s well-traveled and cosmopolitan population to recruit a large group of research subjects—he has 117 volunteers thus far--for a long-term study of immune reactions to a single exposure to either dengue, chikungunya or Zika viruses.
“Several years ago we started posting flyers in area universities and just recruiting by word of mouth, looking for people who had traveled to or were from countries where these diseases are endemic,” Messer said. “Our volunteers are not currently infected but they were once diagnosed with either dengue, chikungunya or Zika.”
The study is still in its early phase, but blood samples from Messer’s volunteers already are providing interesting insights into all three diseases.
For example, one of the volunteers is an elderly woman who was infected with dengue as a child when her parents were in the Peace Corps 50 years ago. But the family moved back to the United States and never again lived in an area where dengue was endemic. Messer learned from her remote exposure to dengue could confer protective antibodies that persist for decades. A better understanding of dengue immunity in these remotely exposed individuals may provide insights that could aid efforts to develop a dengue vaccine that uses a live, weakened form of the disease to provide long-term protection.
Messer also has confirmed that physicians have a tough time distinguishing dengue infections from chikungunya infections. So far, blood tests have revealed that 10 people who volunteered for the study because they had been once diagnosed with dengue actually had more likely been infected with chikungunya.
Messer recently began recruiting patients who have been infected with Zika. One of the issues he wants to explore is whether, over the long term, antibodies to Zika will continue to be confused with antibodies to dengue. The two diseases both come from the same family of viruses known as flaviruses. And during the Zika outbreak in Latin America, lab tests would sometimes have a hard time distinguishing one from the other.
That’s a problem because physicians want to identify Zika patients who previously were infected with dengue. There is evidence that antibodies to dengue may be capable of either intensifying or, conversely, neutralizing a Zika infection, presenting the puzzling paradox that a previous exposure to dengue could make Zika either milder or more severe.
 “Our preliminary results indicate that after the acute phase of the illness has passed, you can more easily distinguish one from the other and see whether a patient really has been exposed to both,” Messer said. “That’s important because we want to follow patients who have been infected with dengue and Zika to see if they are more likely to suffer long-term complications.”
Messer said he got the idea of recruiting a local population to study tropical diseases from Aravinda de Silva, PhD, his mentor from his days studying at the University of North Carolina, Chapel Hill, who had developed a similar cohort.
“When you are working in an area where there is a significant international community and also a lot of people who travel frequently in the developing world, you can recruit research subjects who have been exposed to a wide variety of tropical diseases,” Messer said.