Babesia and plasmodia increase host erythrocyte permeability through distinct mechanisms

Human erythrocytes infected with Plasmodium falciparum have markedly increased permeability to diverse solutes, many of which may be mediated by an unusual small conductance ion channel, the plasmodial surface anion channel (PSAC). Because these increases may be essential for parasite survival in the bloodstream, an important question is whether other intraerythrocytic parasites induce similar ion channels. Here, we examined this question using human erythrocytes infected with Babesia divergens, a distantly related apicomplexan parasite that can cause severe disease in immunocompromised humans. Osmotic lysis experiments after enrichment of infected erythrocytes with a new method revealed that these parasites also increase host permeability to various organic solutes. These permeability changes differed significantly from those induced by P. falciparum in transport rates, selectivity profiles and temperature dependence. Cell-attached and whole-cell patch-clamp experiments confirmed and extended these differences because neither PSAC-like channels nor significant increases in whole-cell anion conductance were seen after B. divergens infection. While both babesia and plasmodia increase host erythrocyte permeability to a diverse collection of organic solutes, they utilize fundamentally different mechanisms.