Transcriptional analysis of hCMEC/D3 cells after PIESP2 stimulation

Cerebral malaria (CM) is the most severe complication caused by Plasmodium falciparum infection and is responsible for the majority of malaria deaths. The pathophysiological changes caused by parasite virulent factors and human immune response to parasites contribute to CM. To date, very few parasite virulent proteins have been found to participate in CM. Identification of new parasite proteins involved in CM may provide new directions for possible intervention. To this end, by using comparative genomics analysis, we identified 430 proteins specific to Plasmodium falciparum. These proteins were divided into 143 independent groups on the basis of their sequence similarity. Several of them have been reported to contributed to CM. Through integrating the information gathered from serological study and gene expression evaluation, we finally identified parasite-infected erythrocyte specific protein 2 (PIESP2) to be a CM related protein. Through further experimental investigation, we found that PIESP2 is an immunogenic protein. Its expression begins at early trophozoite stage and progressively increases with parasite development. Although PIESP2 proteins mainly reside inside infected red blood cells (IRBCs), a few of them are present on IRBC surface at the late trophozoite stage. Moreover, blockage of PIESP2 by antiserum apparently inhibited the adhesion of IRBCs to BMECs. Western blot analysis detected the binding of PIESP2 to BMECs. Transcriptional analysis revealed that PIESP2 binding to BMECs can increase the expression of genes involved in inflammatory response but decrease the expression of genes related to anchoring junction. Therefore, we speculated that PIESP2 contributes to CM by mediating the sequestration of IRBCs to BMECs, inducing inflammation response and impairing the integrity of the blood brain barrier (BBB). Our study was the first time to illustrate the role of PIESP2 in CM.