Intractable malaria parasites made to thrive in human cell culture

Much of what we know about the species of parasite responsible for the malaria widespread in Africa was learnt from studying the parasite's biology and gene expression in human red blood cells in vitro. Yet the species of parasite that causes most malaria outside of Africa, Plasmodium vivax, and a similar species proving deadly in parts of Asia, Plasmodium knowlesi, do not grow in cultured human red blood cells (RBC), meaning researchers must study the parasites in live primates.

Now a team of researchers led by scientists from the UK's National Institute for Medical Research (NIMR), London, including Arnab Pain of King Abdullah University of Science and Technology (KAUST) in Thuwal, Saudi Arabia, may have made the study of P. vivax and P. knowlesi much easier by developing strains of P. knowlesi that thrive in cultured human RBC¹.

After growing P. knowlesi in a mixture of monkey RBC and human serum, the simian malaria parasites were divided into two separate cell lines, with one cultured in a mixture of monkey and human RBC. Eight months later the simian RBC were removed from the mixed system, allowing the simian parasite to grow exclusively in human RBC. After nearly a year in cell culture, the human RBC-adapted simian parasite retained their ability to invade and grow in simian RBC at rates similar to those in human RBC. In addition, the researchers were able to manipulate the parasite's genes, paving the way for genetic study.

"This study will throw light on how malaria parasite recognises and invades human RBC paving the [way to] design anti-invasion vaccines or chemical compounds that could block this vital process in the malaria parasite's life cycle," says Pain.

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