People with immunity to dengue may have a reduced risk of infection with Zika virus, according to a new study.
In the epicenter of the Zika epidemic in northeast Brazil, 73 percent of people living in an urban slum in Salvador were infected in 2015.
In the study, which appears in the journal Science, researchers examined a cohort of 1,453 individuals participating in a long-term health survey in Pau da Lima, Salvador, Brazil who may have been exposed to Zika during the 2015 outbreak. In the epicenter of the Zika epidemic in northeast Brazil, 73 percent of people living in an urban slum in Salvador were infected in 2015.
Using multiple immune assays, the team characterized this cohort’s immunity to dengue before and after the Zika outbreak and identified Zika infections. To do this, the team developed a novel assay that measured immunoglobulin G3 responses to Zika, a specific antibody that recognizes Zika.
“This study is the first to demonstrate that immunity to dengue can protect against Zika infection in human populations,” says Derek Cummings, a biology professor and a researcher with the University of Florida’s Emerging Pathogens Institute.
“One of the challenges in studying dengue and Zika is distinguishing immunity to one virus from the other. We used multiple methods to disentangle immune responses to each virus,” says Federico Costa, an associate professor at the Federal University of Bahia and an associate adjunct professor at the Yale University School of Public Health.
A majority of individuals in the cohort had been infected with dengue before the Zika outbreak. For those with prior immunity to dengue, each doubling of antibody titers was associated with a 9 percent reduction in risk of Zika infection.
“Even though there was protective immunity in the population, this community was heavily infected,” says coauthor Albert Ko, a professor and chair of epidemiology at Yale School of Public Health. “Dengue immunity reduced individuals’ risk, but still 73 percent of the population was infected by Zika.”
The results provide evidence that acquired immunity to the Zika virus has driven Zika transmission to low levels.
“The Zika pandemic has created overall high rates of immunity to this virus in the Americas, which will be a barrier for outbreaks in coming years,” says Isabel Rodriguez-Barraquer, an assistant professor at University of California, San Francisco and one of the lead authors of the study.
Additional researchers contributing to the work came from the Brazilian Ministry of Health and the University of Pittsburgh.
The US National Institutes of Health; the Yale School of Public Health; and the Brazilian Ministries of Health, Education, Science, and Technology.
Source: University of Florida