title: Analysis of immune responses against T- and B-cell epitopes from Plasmodium falciparum liver-stage antigen 1 in rodent malaria models and malaria-exposed human subjects in India.
abstract: Liver-stage antigen 1 (LSA-1) is a potential vaccine candidate against preerythrocytic stages of malaria. We report here the immunogenicity of linear synthetic constructs delineated as T(H)-cell determinants from the nonrepeat regions of Plasmodium falciparum LSA-1 in murine models and human subjects from areas where malaria is endemic in Rajasthan State, India. Seven peptide constructs (LS1.1 to LS1.7) corresponding to predicted T-cell sites from both the N- and C-terminal regions and peptide LS1R from a repeat region of PfLSA-1 were synthesized to analyze the cellular immune responses. These linear peptides were also tested for humoral responses in order to determine if there were any overlapping B-cell epitopes in the predicted T-cell sites. Most peptides induced cellular responses in peptide-immunized BALB/c and C57BL/6 mice as measured by proliferation and cytokine analysis. Cross-reactive T-cell recognition of P. falciparum-based peptides in Plasmodium berghei-immune animals was evaluated, but only one peptide, LS1.2 (amino acids 1742 to 1760) triggered T-cell proliferation and interleukin-2 and gamma interferon secretion in P. berghei-immune splenocytes of BALB/c and C57BL/6 mice as well as in Thamnomys gazellae (natural host of P. berghei ANKA). In an enzyme-linked immunosorbent assay with the peptides, only one peptide, LS1.1, was recognized by anti-P. berghei liver-stage serum. Three peptides (LS1. 1, LS1.2, and LS1.3) of the eight peptides tested in this study were recognized by a relatively large percentage of P. falciparum-exposed human subjects; the reactivities ranged from approximately 45% for LS1.3 to approximately 60% for LS1.1 and LS1.2. Interestingly, all of the eight putative T-cell determinants were also recognized by the sera collected from malaria patients, although the response was variable in nature. These T(H)- and B-cell epitopes may be of potential value for preerythrocytic antigen-based malaria subunit vaccine formulations.
authors.affiliation: Malaria and Structural Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: S K
authors.initials: SK
authors.lastname: Joshi
authors.forename: A
authors.initials: A
authors.lastname: Bharadwaj
authors.forename: S
authors.initials: S
authors.lastname: Chatterjee
authors.forename: V S
authors.initials: VS
authors.lastname: Chauhan
mesh_terms: D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D000953:Antigens, Protozoan / Q000008:administration & dosage / Q000235:genetics; D001402:B-Lymphocytes / Q000276:immunology*; D002648:Child; D000939:Epitopes / Q000008:administration & dosage / Q000235:genetics; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000096:biosynthesis; D007376:Interleukin-2 / Q000096:biosynthesis; D008099:Liver / Q000469:parasitology; D008213:Lymphocyte Activation; D016778:Malaria, Falciparum / Q000276:immunology* / Q000469:parasitology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000235:genetics / Q000254:growth & development / Q000276:immunology*; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000953:Antigens, Protozoan; D000939:Epitopes; D007376:Interleukin-2; D011994:Recombinant Proteins; C067302:liver stage-specific antigen, Plasmodium; D007371:Interferon-gamma