Poster Presentation First Malaria World Congress 2018

Isolation of naturally acquired human monoclonal antibodies to Plasmodium vivax adhesin PvRBP2b reveals novel inhibitory epitopes (#249)

Li Jin Chan 1 2 , Anugraha Gandhirajan 3 , Lenore Carias 3 , Camila Franca 1 2 , Sebastien Menant 1 , Yi Jun Chen 1 , Calum McConville 1 2 , Christopher King 3 , Wai-Hong Tham 1 2 , Ivo Mueller 1 2
  1. Infection and Immunity, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
  2. Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
  3. Centre for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio, United States

Background and Aims

Plasmodium vivax invades reticulocytes exclusively to cause malaria in humans. The interactions between the parasite adhesin P. vivax reticulocyte binding protein 2b (PvRBP2b) with Transferrin receptor 1 (TfR1) enables host cell recognition, which is critical for successful invasion. We aim to isolate naturally acquired human monoclonal antibodies to PvRBP2b and map the epitopes bound by inhibitory antibodies to facilitate vaccine design.


Single B cells that recognized PvRBP2b were isolated using fluorescence activated cell sorting of peripheral blood mononuclear cells from adult Cambodian individuals. Antibody sequences were cloned and human monoclonal antibodies were expressed and purified by Protein A column affinity chromatography followed with size exclusion chromatography. Inhibition of the PvRBP2b-TfR1 interaction was examined using a flow cytometry-based red blood cell binding assay. Epitopes bound by the human monoclonal antibodies were mapped using a collection of PvRBP2b recombinant fragments. Competition ELISAs were performed using a panel of well characterized inhibitory mouse monoclonal antibodies to determine if the human antibodies have different structural modes of action.


Sequencing of 94 antibody heavy chains from PvRBP2b specific memory B cells from three Cambodian individuals has yielded 36 distinct clonal groups. Currently, we have expressed human monoclonal antibodies from 16 different clonal groups, four of which abolish PvRBP2b binding to reticulocytes and four that moderately inhibit PvRBP2b binding. Seven of these inhibitory human monoclonal antibodies compete with our collection of inhibitory mouse monoclonal antibodies whereas one human monoclonal antibody binds a completely new inhibitory epitope.


Interrogating the human antibody repertoire generated from natural infection of P. vivax has revealed the presence of several inhibitory monoclonal antibodies to PvRBP2b with different structural modes of action. The characterization of inhibitory epitopes will guide the rational design of vaccine antigens.

  1. Gruszczyk J, et al. (2018) Transferrin receptor 1 is a reticulocyte-specific receptor for Plasmodium vivax. Science 359(6371):48-55.
  2. Franz B, May KF, Dranoff G, Wucherpfennig K (2011) Ex vivo characterization and isolation of rare memory B cells with antigen tetramers. Blood 118(2):348-357.