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Infection and Immunity, June 2008, p. 2576-2586, Vol. 76, No. 6
0019-9567/08/$08.00+0     doi:10.1128/IAI.00677-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Expression, Purification, and Characterization of the Immunological Response to a 40-Kilodalton Plasmodium vivax Tryptophan-Rich Antigen{triangledown}

Asim A. Siddiqui,1 Hema Bora,1 Neeru Singh,2 Aditya P. Dash,3 and Yagya D. Sharma1*

Department of Biotechnology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India,1 National Institute of Malaria Research (ICMR), Field Station, Jabalpur (M.P.) 482003, India,2 National Institute of Malaria Research, 22 Shamnath Marg, Delhi 110054, India3

Received 16 May 2007/ Returned for modification 8 September 2007/ Accepted 7 March 2008

We describe here an ~40-kDa Plasmodium vivax tryptophan-rich antigen (PvTRAg40) which contains 321 amino acids and 11.4% tryptophan residues. This protein shows 65% homology (35% identity) with the previously described PvTRAg, besides sharing 23 of 27 positionally conserved tryptophan residues and similar genomic organization. The nucleotide sequence of the entire tryptophan-rich domain of PvTRAg40 was identical among 35 P. vivax clinical isolates. The protein is expressed by ring, trophozoite, and schizont stages of the parasite. The cDNA covering exon 2 of PvTRAg40 was cloned and expressed in the pPROEXHTa vector, and recombinant protein was purified. A high humoral immune response (90.7% seropositivity; n = 43) against this recombinant protein was detected in humans during the course of natural P. vivax infection. Eighty percent of the total of 20 P. vivax-exposed individuals exhibited lymphoproliferative responses against this antigen. The T cells of these individuals produced larger amounts of interleukin-12 (IL-12), IL-4, and IL-10 than gamma interferon and tumor necrosis factor alpha cytokines in response to the recombinant protein. Production of Th2-biased cytokines, conserved T- and B-cell epitopes, and an enhanced humoral immune response indicate that PvTRAg40 could possibly induce antibody-mediated immune protection against infection.

* Corresponding author. Mailing address: Department of Biotechnology, All India Institute of Medical Sciences, New Delhi 110029, India. Phone: 91-11-26588145. Fax: 91-11-26589286. E-mail: ydsharma_aiims{at}yahoo.com

{triangledown} Published ahead of print on 24 March 2008.

Editor: J. F. Urban, Jr.

Infection and Immunity, June 2008, p. 2576-2586, Vol. 76, No. 6
0019-9567/08/$08.00+0     doi:10.1128/IAI.00677-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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