High immunogenecity and erythrocyte-binding activity in the tryptophan-rich domain (TRD) of the 74-kDa Plasmodium vivax alanine-tryptophan-rich antigen (PvATRAg74).
Plasmodium vivax is the most widespread species of human malaria parasite affecting 70-80 million people worldwide each year. In recent years, some potential vaccine candidate antigens from P. vivax have been identified including tryptophan-rich antigens PvTRAg and PvTARAg55. We report here the identification and partial characterization of a 74 kDa P. vivax alanine-tryptophan-rich antigen (PvATRAg74) which is expressed by all asexual blood stages of the parasite. This protein contains two major domains, i.e. alanine-rich domain (ARD) in N-terminal region and the tryptophan-rich domain (TRD) at C-terminus. PvATRAg74 also contains variable numbers of octa-peptide repeats in the ARD region. The C-terminal PvATRAg74 containing TRD was highly conserved among 32 P. vivax isolates while N-terminal ARD showed genetic polymorphisms. The 36 kDa TRD was expressed in E. coli and named here as His6-TRD. The purified recombinant His6-TRD showed binding with uninfected human erythrocytes. This antigen was also recognized by all 38 P. vivax patients' sera on ELISA thus showing a very high seropositivity rates. In vitro stimulation of lymphocytes with purified His6-TRD indicated that it induced T cell immune response in majority (94%, n=16) of P. vivax exposed individuals. The stimulated T cells produced higher amount of IL-4 and IL-10 than IFN-gamma, TNF-alpha, and IL-12 indicating a Th2 type of response bias. Unlike PvTARAg55, this antigen is more immunogenic in humans and possesses the erythrocyte-binding activity. Immunogenecity of PvATRAg74 is similar to PvTRAg whose erythrocyte-binding activity still remains unknown.
Alam
Mohammad Tauqeer
MT
Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, India.
Bora
Hema
H
Singh
Neeru
N
Sharma
Yagya D
YD
D000328:Adult; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D000953:Antigens, Protozoan / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D049109:Cell Proliferation; D002648:Child; D017124:Conserved Sequence; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D004912:Erythrocytes / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D005260:Female; D015870:Gene Expression; D006801:Humans; D008222:Lymphokines / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010966:Plasmodium vivax / Q000235:genetics / Q000276:immunology*; D011110:Polymorphism, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020449:Repetitive Sequences, Amino Acid; D017422:Sequence Analysis, DNA; D013601:T-Lymphocytes / Q000276:immunology
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D016054:DNA, Protozoan; D008222:Lymphokines