Hi everyone, my name is Thomas Langerak and I am one of the Viruskenner Coaches this year. I studied medicine and at the moment I am doing research at the Virology department of Erasmus MC. My research is in part focussing on a mechanism called antibody dependent enhancement. In this blog, I will try to explain you what antibody dependent enhancement is.

As you may know, antibodies are a powerful tool of our immune system to combat pathogens such as viruses and bacteria. It might therefor surprise you that antibodies can sometimes actually harm us and increase the severity of a viral infection via antibody dependent enhancement. Antibody dependent enhancement is mainly known for Dengue virus. This is a virus that is transmitted through mosquitoes and is highly prevalent in tropical regions. There are four types of dengue (dengue 1-4) that only differ a bit from each other. When someone gets infected with dengue virus type 1, the immune system will make antibodies against this virus and clear the virus. These antibodies stay present in the blood for quite a while. If, few months later, this person gets infected again with dengue, for example with dengue type 2, the antibodies against dengue type 1 that are still present in the blood can also bind to dengue type 2. However, since these antibodies are not specific enough, they cannot fully neutralize this dengue type 2 virus and therefor this virus, coated by antibodies, is still infectious. Some immune cells in the human body recognize viruses when they are covered by antibodies and can efficiently clear these virus-antibody complexes by ‘eating’ them. However, whenever such an immune cell eats a virus that is covered by antibodies but is not neutralized by these antibodies, this virus can start replicating itself in these immune cells. The antibodies therefor actually helped the virus in entering cells in which it can replicate, much like a Trojan horse! This is why a severe dengue infection with complications such as spontaneous bleeding, occurs more often during a secondary dengue infection compared to a primary dengue infection.

Luckily this is quite a rare phenomenon that only a few viruses are capable of. Still I think it is a very interesting mechanism that deserve to be studied so that we understand it better.