Periodic Reporting for period 1 - PASSAGE (Plasmodium liver stage schizogony: high replication and genetic diversity)
Okres sprawozdawczy: 2023-06-01 do 2025-11-30
Malaria remains one of the world’s deadliest infectious diseases, killing a child every minute. It is caused by Plasmodium parasites, transmitted by infected mosquitoes. After entering the human body, the parasite first travels to the liver. There, a single parasite can multiply into tens of thousands of new forms that go on to infect red blood cells and cause disease. The amount of parasite biomass generated during this liver stage is directly linked to the severity of malaria.
Despite decades of research, we still do not fully understand how Plasmodium achieves such extraordinarily high replication rates inside liver cells, nor what the consequences are for parasite evolution and disease progression. This lack of knowledge hampers the development of new strategies to prevent and treat malaria.
The PASSAGE project aims to fill this gap by:
1. Describing in detail how Plasmodium replicates in the liver.
2. Identifying the parasite’s own molecular “control switches” that regulate this replication.
3. Understanding the causes and consequences of DNA damage that occur during this phase, and how this might generate genetic diversity that helps the parasite adapt and survive.
Ultimately, the project will provide unprecedented insights into a critical phase of malaria infection, potentially revealing novel drug and vaccine targets.
Despite decades of research, we still do not fully understand how Plasmodium achieves such extraordinarily high replication rates inside liver cells, nor what the consequences are for parasite evolution and disease progression. This lack of knowledge hampers the development of new strategies to prevent and treat malaria.
The PASSAGE project aims to fill this gap by:
1. Describing in detail how Plasmodium replicates in the liver.
2. Identifying the parasite’s own molecular “control switches” that regulate this replication.
3. Understanding the causes and consequences of DNA damage that occur during this phase, and how this might generate genetic diversity that helps the parasite adapt and survive.
Ultimately, the project will provide unprecedented insights into a critical phase of malaria infection, potentially revealing novel drug and vaccine targets.
In the first 24 months, we have made several important discoveries:
• Challenging textbook knowledge – We found that Plasmodium does not replicate in the liver solely by a process called schizogony (multiple nuclear divisions followed by cell division). Instead, it starts with an unusual mode of replication known as endopolygeny around 16 hours after infection, then switches to schizogony after 48 hours.
• Link to DNA damage – The final, highly synchronous round of replication is accompanied by extensive DNA damage, marked by a molecular signal known as γ-H2A. This suggests that rapid replication puts the parasite’s genome under stress.
• Key regulators uncovered – We generated conditional knockdown parasite lines for four kinases (Mrk1, Ark1, Ark2, Nek3) believed to regulate cell division. Three of these lines (Mrk1, Ark1, Ark2) progressed to liver stage studies, revealing that these enzymes are essential for proper parasite growth in the liver. Notably, Ark2 is crucial for establishing blood-stage infection.
• New genetic tools – To overcome limitations in the initial knockdown approach during mosquito stages, we began developing a DiCre-based system that allows precise gene control at specific life cycle stages.
• Broader impact – These findings were shared with the scientific community, including at the Keystone Symposia on Malaria in March 2025.
• Challenging textbook knowledge – We found that Plasmodium does not replicate in the liver solely by a process called schizogony (multiple nuclear divisions followed by cell division). Instead, it starts with an unusual mode of replication known as endopolygeny around 16 hours after infection, then switches to schizogony after 48 hours.
• Link to DNA damage – The final, highly synchronous round of replication is accompanied by extensive DNA damage, marked by a molecular signal known as γ-H2A. This suggests that rapid replication puts the parasite’s genome under stress.
• Key regulators uncovered – We generated conditional knockdown parasite lines for four kinases (Mrk1, Ark1, Ark2, Nek3) believed to regulate cell division. Three of these lines (Mrk1, Ark1, Ark2) progressed to liver stage studies, revealing that these enzymes are essential for proper parasite growth in the liver. Notably, Ark2 is crucial for establishing blood-stage infection.
• New genetic tools – To overcome limitations in the initial knockdown approach during mosquito stages, we began developing a DiCre-based system that allows precise gene control at specific life cycle stages.
• Broader impact – These findings were shared with the scientific community, including at the Keystone Symposia on Malaria in March 2025.
PASSAGE is breaking new ground by:
• Revealing a previously unknown replication strategy in Plasmodium liver stages.
• Linking high replication rates to DNA damage and potential genetic diversification before parasites even reach the blood.
• Providing the first functional evidence of key parasite kinases as regulators of liver-stage growth and disease outcome.
These results not only expand fundamental knowledge but also open the door to novel interventions. If we can disrupt these replication processes or the parasite’s ability to manage DNA damage, we may block the infection before symptoms appear.
Future work will complete the mapping of DNA damage “hotspots” in the parasite genome, determine exactly how genetic diversity arises in the liver stage, and explore how this influences malaria severity. Such knowledge could guide the design of next-generation antimalarial drugs and inform vaccine strategies targeting the liver stage, which is a “bottleneck” in the parasite’s life cycle.
• Revealing a previously unknown replication strategy in Plasmodium liver stages.
• Linking high replication rates to DNA damage and potential genetic diversification before parasites even reach the blood.
• Providing the first functional evidence of key parasite kinases as regulators of liver-stage growth and disease outcome.
These results not only expand fundamental knowledge but also open the door to novel interventions. If we can disrupt these replication processes or the parasite’s ability to manage DNA damage, we may block the infection before symptoms appear.
Future work will complete the mapping of DNA damage “hotspots” in the parasite genome, determine exactly how genetic diversity arises in the liver stage, and explore how this influences malaria severity. Such knowledge could guide the design of next-generation antimalarial drugs and inform vaccine strategies targeting the liver stage, which is a “bottleneck” in the parasite’s life cycle.