Dormant malaria parasites become less active as they age

08 Jan 2019 | Back to News, Publications and Annual Reports

The most commonly-occurring strain of malaria, vivax malaria, is difficult to combat because the parasite forms dormant stages known as 'hypnozoites', which embed themselves in the host's liver. They can remain there, unnoticed, for weeks or even years – until suddenly, for unknown reasons, they resume their growth and cause an outbreak of malaria.

So far, no adequate therapy exists to treat this form. Recently, however, we have learned more about the genetic properties of these dormant stages – information that is extremely valuable to pharmaceutical research.

Looking for weaknesses

The dormant parasite is not only a source of disease, but also the first step in spreading vivax malaria. This is because as soon as the hypnozoites resume their growth and trigger a blood-borne infection, it once more becomes possible for mosquitoes to transmit the malaria parasite. In recent years, scientists around the world have been working hard to find new drugs to eliminate these dormant malaria parasites. While the impact on the parasites of many potential medicines can be tested in Petri dishes, the quest for an effective drug is proving to be anything but simple.

By learning more about hypnozoites, we hope to identify weaknesses which we can then target through the development of specific medicines. It is difficult, however, to use the vivax parasite itself in this research, as we have not yet found a way to culture the blood-borne form. We must therefore rely on infected blood from patients. As a result, the few techniques that have been developed for unravelling the mysteries of dormant vivax parasites are still in their infancy.

Older forms are less active

Another malaria parasite that also forms dormant stages is found in primates. Genetically speaking, this parasite is virtually identical to the vivax parasite, which is why it is frequently used in drug research aimed at combating hypnozoites. While in the past, this often meant infecting large numbers of monkeys, today it mostly involves testing in Petri dishes. Visit our 'behind the scene' page to watch a video about this.
BPRC researchers have previously succeeded in using the primate parasite to develop new techniques, which have made it possible to obtain and catalogue isolated hypnozoites. Those hypnozoites were six days old.

Vital information for further research

So far, our researchers have managed to successfully isolate nine-day-old hypnozoites. Together with their partners in Basel, they were then able to study the genetic properties of these older forms. Their findings proved that these older specimens were less active than the six-day-old forms. Still, certain processes did remain active, which is vital information for further research.

This study was published in the online scientific journal eLIFE.