Expression, purification, and characterization of the immunological response to a 40-kilodalton Plasmodium vivax tryptophan-rich antigen.
We describe here an approximately 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.
Siddiqui
Asim A
AA
Department of Biotechnology, All India Institute of Medical Sciences, New Delhi 110029, India.
Bora
Hema
H
Singh
Neeru
N
Dash
Aditya P
AP
Sharma
Yagya D
YD
D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan / Q000096:biosynthesis; D000953:Antigens, Protozoan / Q000737:chemistry* / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D001483:Base Sequence; D016207:Cytokines / Q000096:biosynthesis; D005786:Gene Expression Regulation; D006801:Humans; D007074:Immunoglobulin G / Q000096:biosynthesis; D008213:Lymphocyte Activation; D016780:Malaria, Vivax / Q000276:immunology; D008969:Molecular Sequence Data; D010966:Plasmodium vivax / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D016415:Sequence Alignment; D013601:T-Lymphocytes / Q000276:immunology; D014364:Tryptophan / Q000737:chemistry*
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D016207:Cytokines; D007074:Immunoglobulin G; D014364:Tryptophan