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Volume 11 Supplement 1

Challenges in malaria research

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Erythrocyte binding activity of Plasmodium vivax tryptophan rich antigens is inhibited by patients’ antibodies


Plasmodium vivax uses duffy antigen to invade the human erythrocytes but reports of duffy negative infection by P. vivax indicate that this parasite may also be using some other alternative receptors for the invasion [1]. Studies are therefore required to identify these additional parasite molecules which are involved in host-parasite interaction. Plasmodium vivax, contains a family of tryptophan rich antigens containing positionally conserved tryptophan residues. These antigens can induced significant cellular and humoral responses in human individuals [2, 3] and few showed interaction with erythrocytes.

Materials and methods

Recombinant Plasmodium vivax tryptophan-rich antigens were purified by Ni-NTA affinity chromatography. Heparinized blood was collected from healthy lab individuals to obtain human erythrocytes for binding assays, and from the microscopically confirmed P.vivax infected individuals for patients’ sera. Rabbit antibodies against PvTRAgs used here were raised in the lab. Erythrocyte binding assays were performed by cell ELISA and Flow cytometry [2, 4].


PvTRAgs binds to the human erythrocytes in a concentration dependent manner and not to the human lymphocytes. The binding was specific as competition with untagged proteins inhibits the erythrocyte binding to 50% at equimolar concentration. Antibodies raised against rabbits and produced by infected patients inhibit the binding of respective PvTRAg at different dilutions. PvTRAg38 and PvATRAg74 was sensitive to chymotrypsin only and not to the trypsin and neuraminidase while all other PvTRAgs were resistant to all these proteases.


Six out of fifteen PvTRAgs bind specifically to the human erythrocytes and were inhibited by rabbit anti PvTRAgs and also by the antibodies produced during natural course of P. vivax infection. There may be more than one RBC receptor for these six PvTRAgs where only PvTRAg38 and PvATRAg74 are sensitive to chymorypsin while others using those molecules which are other than glycophorin and sialoglycoproteins. Studies are in progress to investigate the respective RBC receptors for these PvTRAgs and their role in erythrocyte invasion process.


  1. Mendes C, Dias F, Figueiredo J, Mora VG, Cano J, de Sousa B, do Rosario VE, Benito A, Berzosa P, Arez AP: Duffy negative antigen is no longer a barrier to Plasmodium vivax - molecular evidences from the African West Coast (Angola and Equatorial Guinea). PLoS Negl Trop Dis. 2011, 5: e1192-10.1371/journal.pntd.0001192.

    Article  PubMed Central  CAS  PubMed  Google Scholar 

  2. Alam MT, Bora H, Singh N, Sharma YD: High immunogenecity and erythrocyte-binding activity in the tryptophan-rich domain (TRD) of the 74-kDa Plasmodium vivax alanine-tryptophan-rich antigen (PvATRAg74). Vaccine. 2008, 26: 3787-3794. 10.1016/j.vaccine.2008.05.059.

    Article  CAS  PubMed  Google Scholar 

  3. Jalah R, Sarin R, Sud N, Alam MT, Parikh N, Das TK, Sharma YD: Identification, expression, localization and serological characterization of a tryptophan-rich antigen from the human malaria parasite Plasmodium vivax. Mol Biochem Parasitol. 2005, 142: 158-169. 10.1016/j.molbiopara.2005.01.020.

    Article  CAS  PubMed  Google Scholar 

  4. Tran TM, Moreno A, Yazdani SS, Chitnis CE, Barnwell JW, Galinski MR: Detection of a Plasmodium vivax erythrocyte binding protein by flow cytometry. Cytometry A. 2005, 63: 59-66.

    Article  PubMed  Google Scholar 

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Department of Biotechnology, Government of India for financial support. Dr. Chetan Chitnis for providing DBP region II (PvRII) and Dr. S. S. Chauhan for his help in critical evaluation of the data.

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Tyagi, R.K., Sharma, Y.D. Erythrocyte binding activity of Plasmodium vivax tryptophan rich antigens is inhibited by patients’ antibodies. Malar J 11 (Suppl 1), P98 (2012).

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