Abstract
Erythrocyte-binding-like (EBL) proteins are known to play an important role in malaria parasite invasion of red blood cells (RBCs); however, any roles of EBL proteins in regulating host immune responses remain unknown. Here, we show that Plasmodium yoelii EBL (PyEBL) can shape disease severity by modulating the surface structure of infected RBCs (iRBCs) and host immune responses. We identified an amino acid substitution (a change of C to Y at position 741 [C741Y]) in the protein trafficking domain of PyEBL between isogenic P. yoelliinigeriensis strain N67 and N67C parasites that produce different disease phenotypes in C57BL/6 mice. Exchanges of the C741Y alleles altered parasite growth and host survival accordingly. The C741Y substitution also changed protein processing and trafficking in merozoites and in the cytoplasm of iRBCs, reduced PyEBL binding to band 3, increased phosphatidylserine (PS) surface exposure, and elevated the osmotic fragility of iRBCs, but it did not affect invasion of RBCs in vitro The modified iRBC surface triggered PS-CD36-mediated phagocytosis of iRBCs, host type I interferon (IFN-I) signaling, and T cell differentiation, leading to improved host survival. This study reveals a previously unknown role of PyEBL in regulating host-pathogen interaction and innate immune responses, which may be explored for developing disease control strategies.IMPORTANCE Malaria is a deadly parasitic disease that continues to afflict hundreds of millions of people every year. Infections with malaria parasites can be asymptomatic, with mild symptoms, or fatal, depending on a delicate balance of host immune responses. Malaria parasites enter host red blood cells (RBCs) through interactions between parasite ligands and host receptors, such as erythrocyte-binding-like (EBL) proteins and host Duffy antigen receptor for chemokines (DARC). Plasmodium yoelii EBL (PyEBL) is known to play a role in parasite invasion of RBCs. Here, we show that PyEBL also affects disease severity through modulation of host immune responses, particularly type I interferon (IFN-I) signaling. This discovery assigns a new function to PyEBL and provides a mechanism for developing disease control strategies.