Plasmodium vivax reticulocyte-binding protein (PvRBP) rat antibodies block reticulocyte binding of the native PvRBP parasite proteins. Flow cytometry dot plots depicting the inhibition of binding of native PvRBP2c (A) and PvRBP1a (B) in the presence of the respective anti-rRBP2.2/1.1 total rat immunoglobulin G (IgG; 400 and 800 µg/mL). APC, allophycocyanin; TO, thiazole orange. C, D, Bar charts showing the percentage of reticulocyte-binding inhibition of native PvRBP2c (C) and PvRBP1a (D) by anti-PvRBP IgG compared with preimmune rat IgG. The reticulocyte binding of the native PvRBP2c and PvRBP1a parasite proteins was potently blocked by the rRBP2.2 and rRBP1.1 rat antibodies (total IgG). As controls, reticulocyte binding of native PvRBP2c/PvRBP1a was analyzed in the presence of total rat IgG against the non-binders, rRBP2.3 and rRBP1.5. Anti-rat rRBP2.3/rRBP1.5 IgG failed to block the binding of native PvRBP2c and PvRBP1a proteins. Reticulocytes were enriched by magnetic sorting. *P < .001. Abbreviation: rRBP, recombinant RBP.