title: Presence of memory T cells and naturally acquired antibodies in Plasmodium vivax malaria-exposed individuals against a group of tryptophan-rich antigens with conserved sequences.
abstract: BACKGROUND
  Tryptophan-rich antigens of malarial parasites have been proposed to be the potential vaccine candidate antigens. Plasmodium vivax contains the largest number of such antigens, which need to be evaluated for their immune responses.
  
  
  METHODS
  Recombinant proteins of 15 P. vivax tryptophan-rich antigens (PvTRAgs) were expressed, purified, and used for the human humoral and cellular immune responses. Genetic polymorphism of these 15 genes was also determined among clinical P. vivax isolates.
  
  
  RESULTS
  The T lymphocytes of P. vivax exposed individuals expressed higher level of CD69 against all 15 PvTRAgs. These antigens also activated the large population of CD4(+) T cells and produced higher level of intracellular IL-2, INF-γ and IL-4. Although there was a mixed Th1 and Th2 response against these antigens, this response was biased toward Th2. The majority of P. vivax patients (75.7%-100%, n = 33) produced IgG antibodies against these antigens. Most of these antigens showed conserved T- and B-cell epitopes in the parasite population.
  
  
  CONCLUSIONS
  These results suggest the presence of memory T cells in humans against these antigens to generate faster and more specific immune responses to minimize the P. vivax infection. Further characterization of these PvTRAgs may lead to the identification of a potential therapeutic target.
authors.affiliation: Department of Biotechnology,  All India Institute of Medical Sciences, Ansari Nagar, New Delhi,  India.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Zeeshan
authors.forename: Hema
authors.initials: H
authors.lastname: Bora
authors.forename: Yagya Dutta
authors.initials: YD
authors.lastname: Sharma
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D000913:Antibodies, Protozoan / Q000096:biosynthesis*; D000953:Antigens, Protozoan / Q000276:immunology*; D001483:Base Sequence; D017124:Conserved Sequence; D006801:Humans; D007111:Immunity, Cellular / Q000276:immunology; D056724:Immunity, Humoral / Q000276:immunology; D007074:Immunoglobulin G / Q000096:biosynthesis; D007194:India / Q000453:epidemiology; D007371:Interferon-gamma / Q000378:metabolism; D007376:Interleukin-2 / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism; D016780:Malaria, Vivax / Q000453:epidemiology / Q000276:immunology*; D008969:Molecular Sequence Data; D010966:Plasmodium vivax / Q000235:genetics / Q000276:immunology*; D011110:Polymorphism, Genetic; D011994:Recombinant Proteins / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013601:T-Lymphocytes / Q000276:immunology; D018417:Th1 Cells / Q000276:immunology; D018418:Th2 Cells / Q000276:immunology; D014364:Tryptophan / Q000276:immunology*
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D007074:Immunoglobulin G; D007376:Interleukin-2; D011994:Recombinant Proteins; D015847:Interleukin-4; D007371:Interferon-gamma; D014364:Tryptophan