Researchers at the Howard Hughes Medical Institute have discovered how malaria parasites evade the human immune system on their way to infecting people. Their discovery was published in Nature in late 2005.
Essentially, the parasite has a number of cloaking mechanisms, and keeps most of them in reserve. As it encounters resistance from the human immune system the parasite is capable of tailoring its cloaking to the immune system. The parasite has dozens of genes designed to get past the immune system, and what the researchers found was that as one gene was activated, that also trigger the suppression of the others. In this way, the malaria parasite is able to try one method after another to infect the host, and reduce the risk that the host might quickly develop an immunity against most or all of the parasite’s cloaking methods.
As HHMI researcher Alan Cowman put it in a press release announcing the discovery,
It’s like a leopard being able to change its spots. New forms come up, and the immune system beats them down again. Because of this a lot of people think you need five years of constant exposure to malaria in its different disguises to gain immunity.
Unfortunately too many people, especially children, die long before they can develop immunities to the malaria parasite’s numerous tricks. Even among people who develop immunity, that immunity can be quickly lost if the individual is not consistently exposed to malaria parasites.
This sort of research could one day lead to a treatment for malaria that might, for example, defeat this mechanism and allow for those exposed to malaria to quickly develop immune responses to all of its cloaking mechanisms.
How malaria dupes immune system. BBC, December 29, 2005.
Scientists Lift Malaria’s Cloak of Invisibility. Press Release, Howard Hughes Medical Institute, December 28, 2005.