P. vivax accounts for 19 million infections annually and is the most widely distributed and relapsing human malaria. Its infection is strictly limited to human reticulocytes which are young red blood cells. Infection in the blood-stages leads to the clinical symptoms associated with P. vivax infection. Entry of P. vivax parasites into reticulocytes is dependent on multiple parasite ligand-host receptor interactions. Recent work shows that P. vivax reticulocyte binding protein 2b (PvRBP2b) was identified to bind reticulocyte receptor transferrin receptor 1 (TfR1) to mediate the invasion into human reticulocytes . Anti-PvRBP2b mouse monoclonal antibodies obtained by hybridoma technology inhibit PvRBP2b-TfR1 interaction and block P. vivax invasion. These results prove the critical role PvRBP2b-TfR1 interaction plays in P. vivax invasion and also suggest the potential application of anti-PvRBP2b monoclonal antibodies in parasite invasion research and malaria treatment. In this project, we aim to adapt second-generation monoclonal antibodies using techniques that combine antigen-specific B cell sorting and antibody gene cloning. We enriched B cells from PvRBP2b-immunized mice and sorted PvRBP2b-specific B cells with B cell surface markers and fluorescent PvRBP2b. From a single cell, we synthesized cDNA and amplified antibody genes with nest-PCR. The antibody chains are cloned into expression plasmids for expression in human embryonic cells followed by purification. We will characterize these anti-PvRBP2b monoclonal antibodies on PvRBP2b-TfR1 interaction to better understand how to inhibit P. vivax invasion into reticulocytes.