The cost of drug resistance.

Research over recent years has identified two proteins which, when mutated, can influence the degree of resistance of the malaria parasite to the antimalarial drug chloroquine. One of these proteins, the ‘chloroquine resistance transporter' is discussed below (see "Learning about the malaria parasite's ‘chloroquine resistance transporter' from others in its family"). The other is called ‘P-glycoprotein homologue 1', or Pgh1 for short. How mutations in this protein influence the sensitivity of the parasite to antimalarial drugs is still unclear. But what we have shown in this study is that mutations in Pgh1 that increase the degree of chloroquine resistance, also have the effect of reducing the overall ‘vigour' of the parasite, retarding its growth relative to parasites that retain the ‘normal' form of the protein.

High levels of chloroquine resistance therefore come at a significant cost to the malaria parasite.

Hayward, R., Saliba, K.J. and Kirk, K. (2005) pfmdr1 mutations associated with chloroquine resistance incur a fitness cost in Plasmodium falciparum. Molecular Microbiology, 55, 1285-1295.