Malaria
Every year, nearly half a million people die of malaria. The majority of the victims are children under the age of 5 in sub-Saharan Africa. There are medications, but these tend to lose their efficacy because the parasite will become resistant. Genuinely effective vaccines are not yet available.
Every year, nearly half a million people die of the most severe form of malaria, which is particularly prevalent among the poorest people in the world. In addition, there is another form of malaria which tends to be less fatal, but does often cause severe illness. This widespread form of malaria (called vivax-type malaria) annually causes some 14 million people to fall ill.
What the parasites do
Malaria is caused by parasites which are transmitted by mosquitoes. Following a mosquito bite, several hundreds of parasites will travel from the blood to the liver, where they will generally mature and reproduce within two weeks. The liver cell will then burst, causing all these new parasites to bring about the sepsis (blood infection) that makes people ill. If that weren't quite bad enough in itself, it was found thirty years ago that there is a type of malaria some of whose parasites remain ‘dormant’ in the liver. In recent years we have learned more about the biology of this ‘dormant’ parasite.
Complicating factors
In our mission to eradicate malaria (which is an objective shared by researchers and policymakers alike), we will need new and effective medications as well as vaccines. It is quite hard to research antimalarial vaccines and medications, because malaria parasites have a complex life cycle. What makes it so complex is that the parasites do not only develop in the mosquitoes carrying the malaria, but in the human liver, and then in the human blood. In addition, the parasites are highly able to survive in human hosts. Natural human immune systems tend to be incapable of eradicating the parasites. We will have to come up with vaccines that can do a better job of it.
How we conduct our research
Studies examining malaria parasites in rhesus macaques are a good reflection of what happens inside human beings. After all, the malaria parasites hosted by humans and rhesus macaques are closely related. Due to this close kinship, humans can be infected by parasites hosted by monkeys. In addition, monkeys' immune systems and metabolism are a lot like ours, too. Moreover, the unique characteristic of one of the main malaria parasites hosted by humans (the fact that it forms ‘dormant’ parasites in the liver) can be found in certain malaria parasites living in monkeys, as well. This means that monkey models are particularly well suited to pre-clinical trials* examining the safety and efficacy of new medications and vaccines.
In addition to studies involving animal testing, we also focus on methods designed to reduce the number of animals used in experiments, e.g. by establishing culture systems for the various types of parasites.
Our focus areas
A significant part of our research is focused on the creation of new vaccines and medications. In the initial stages, we will mainly use parasites cultivated in test tubes. Using state-of-the-art techniques, we will seek to understand the parasites' weaknesses. We also test the efficacy of new medications against ‘dormant’ liver forms of the parasite in a test tube model we have developed ourselves. Only if an active ingredient proves effective in a test tube will we test its efficacy in a monkey model, using a real malaria infection.
* BPRC has developed a new vaccine against malaria, called AMA1. This vaccine offers protection against the blood forms of the parasite. Thanks to pre-clinical trials in monkey models, we were then able to trial this vaccine in humans. Trials in Paris and Burkina Faso have shown that the vaccine is safe and provokes an immune response. Further trials involving human subjects will have to demonstrate whether this vaccine can help us provide actual protection against malaria.
Why we need monkeys for our studies
To this day, clinical trials cannot be held without prior animal testing. After all, cells in a Petri dish can behave completely differently from cells in a complex immune system. In a small minority of studies, monkeys are the animals most suitable for the study of serious diseases in humans. Pursuant to Dutch law, monkeys can only be used as experimental animals when no alternative method exists.