Understanding cross-reactive immunity to Japanese encephalitis virus

Japanese encephalitis (JE) virus is transmitted by mosquitoes and causes brain swelling mostly in children in Asia. It is a member of a family of viruses that includes yellow fever, dengue and Zika. The body responds to viruses by making antibodies. For this family of viruses, antibodies against one virus can cross-react with another virus, because they are all similar. Surprisingly, this cross-reaction can make a second infection worse. This is a particular problem with dengue. However, the cross-reaction can also be helpful. Studying cross-reactions where these viruses naturally occur is difficult, because you cannot tell which virus was first.

This study has a new way of getting round this problem. I will give a live JE vaccine to people in the UK. The body makes antibodies to a live vaccine in the same way it does for a real infection. I will then test the antibodies of the participants who I will split into two groups: people who have never been exposed to these viruses and those who have been vaccinated against yellow fever.

The aim is to identify helpful cross-reactions and minimise the harmful cross-reaction.