Expression of the erythrocyte-binding antigen 175 in sporozoites and in liver stages of Plasmodium falciparum

Screening of a Plasmodium falciparum genomic expression library for antigen s expressed at the pre-erythrocytic stages resulted in the isolation of a r ecombinant phage (DG249) whose insert corresponded to regions II and III of a 175-kDa erythrocyte-binding antigen (EBA-175). EBA-175 is a parasite lig and implicated in red blood cell invasion. Reverse-transcriptase polymerase chain reaction, indirect immunofluorescent antibody test, and Western blot analysis confirmed that EBA-175 is expressed not only in blood-stage paras ites but also in infected hepatocytes and on the sporozoite surface. The pr esence of EBA-175 on pre-erythrocytic parasites enhances the vaccine potent ial of this antigen by adding another target to the immune responses elicit ed by immunization.