Toxoplasmosis: novel target to prevent transmission

If pregnant women pass Toxoplasma gondii, it can result in serious health problems for their babies such as blindness or brain damage. Additionally, people infected with HIV are at risk of serious complications owing to the reactivation of dormant parasitic cysts in the brain. The parasite, however, is ubiquitous as it is a common infection of cats. Toxoplasma gondii lives inside one third of us and is often transmitted by pets. However, researchers from University of Glasgow’s Wellcome Centre for Molecular Parasitology in collaboration with the University of Vermont now found out that the parasite strictly depends on a key protein to form a communication network and ultimately continue the infection process. 

When the group headed by Markus Meissner disrupted the protein network, parasites could not properly replicate and became unable to leave host cells – which ultimately halts infection. Normally, during an infection, Toxoplasma replication is synchronised as it is in the malaria parasite, both members of the Apicomplexa, meaning that all parasites in the host cell replicate at the same time. 

Until now, it was unclear how the parasites co-ordinated this tightly regulated process. Now, the researchers discovered that the protein actin helps to form an extensive network that connects individual Toxoplasma parasites.  When they depleted actin in the parasite, the network collapsed – the parasites replicated out of synch and were trapped inside the host cell. This provides an insight into how this potentially dangerous parasitic infection can be disrupted, said Meissner. 

When we first saw the formation of such an extensive network, we didn’t believe our eyes and the first thing we discussed was if this is just an artefact. However, at the end all our control experiments demonstrated that it is very real. The major challenge was to convince some of our colleagues who were also looking into the role of actin in these parasites.

The findings could provide more than protection from Toxoplasma, but also new treatments for other parasite diseases, including malaria. We’ve known for many years that actin was an important protein needed for parasite entry into host cells, said Aoife Heaslip, who co-authored the study. However, our discovery that actin forms communication channels between parasites as they grow inside host cells adds a whole new dimension to our understanding.