Researchers from Princeton University’s Department of Molecular Biology have developed a new method that can precisely track the replication of yellow fever virus in individual host immune cells. The technique, which is described in a paper published March 14 in the journal Nature Communications, could aid the development of new vaccines against a range of viruses, including Dengue and Zika.
Yellow fever virus (YFV) is a member of the flavivirus family that also includes Dengue and Zika virus. The virus, which is thought to infect a variety of cell types in the body, causes up to 200,000 cases of yellow fever every year, despite the widespread use of a highly effective vaccine. The vaccine consists of a live, attenuated form of the virus called YFV-17D, whose RNA genome is more than 99 percent identical to the virulent strain. This one percent difference in the attenuated virus’ genome may subtly alter interactions with the host immune system so that it induces a protective immune response without causing disease.
To explore how viruses interact with their hosts, and how these processes lead to virulence and disease, Alexander Ploss, assistant professor of molecular biology, and colleagues at Princeton University adapted a technique — called RNA Prime flow — that can detect RNA molecules within individual cells. They used the technique to track the presence of replicating viral particles in various immune cells circulating in the blood of infected mice. Mice are usually resistant to YFV, but Ploss and colleagues found that even the attenuated YFV-17D strain was lethal if the transcription factor STAT1, part of the antiviral interferon signaling pathway, was removed from mouse immune cells. The finding suggests that interferon signaling within immune cells protects mice from YFV, and that species-specific differences in this pathway allow the virus to replicate in humans and certain other primates but not mice.