Identification of T cell epitopes within a 23-kD antigen (P24) of Toxoplasma gondii.
Among the potentially vaccinating antigens, the products excreted/secreted by the parasite T. gondii have been demonstrated to be excellent candidates. The molecular cloning of one of these antigens (P24) present in excreted/secreted antigens (ESA) has recently been carried out in our laboratory. The recombinant antigen P24 corresponds to a native molecule of 23 kD. We were interested in determining the main epitopes of the P24 antigen eliciting a T lymphocyte response using synthetic peptides derived from the primary structure of P24. Five peptides: 64-79, 88-109, 170-193, 194-208 and 231-250 were synthesized according to their hydrophobicity, mobility and accessibility profiles. The presence of T lymphocyte epitopes in these peptides has been examined in the rat model. The determination of T cell epitopes was carried out using T lymphocytes from infected rats, and from ESA and P24 expression vaccine virus immunized rats. The results showed that the stimulation of T cells with these peptides varied according to the period after Toxoplasma infection. The main T cell stimulation was obtained with the 88-109, 170-193 and 194-208 peptides. When Fisher rats were immunized with ESA, a most significant stimulation was achieved with the 170-193 and 194-208 peptides. In addition, T lymphocytes primed with P24 expressed vaccine virus immunization were more stimulated with the 88-109 and the 194-208 peptides. This study showed that P24-derived peptide-specific T cells were elicited in the three experimental situations, although no antibody response against the 23-kD native antigen was evidenced in the Fisher rat model. However, the native antigen (presented by irradiated parasites) can induce a proliferative response of the 170-193 peptide-specific T lymphocytes, confirming that this peptide contains an important T cell epitope. The adoptive transfer into athymic rats of T helper cells recovered from 170-193 peptide-immunized Fisher rat conferred a significant protection to infected nude rats despite the fact that no antibody production was observed.
Duquesne
V
V
Centre d'Immunologie et de Biologie Parasitaire, Unité mixte INSERM 167-CNRS 624, Lille, France.
Auriault
C
C
Gras-Masse
H
H
Boutillon
C
C
Darcy
F
F
Cesbron-Delauw
M F
MF
Tartar
A
A
Capron
A
A
D000818:Animals; D000953:Antigens, Protozoan / Q000276:immunology*; D002478:Cells, Cultured; D000939:Epitopes / Q000032:analysis*; D005260:Female; D016219:Immunotherapy, Adoptive; D008213:Lymphocyte Activation; D008297:Male; D010446:Peptide Fragments / Q000276:immunology; D051381:Rats; D011916:Rats, Inbred F344; D013601:T-Lymphocytes / Q000276:immunology*; D014122:Toxoplasma / Q000276:immunology*; D014616:Vaccinia virus / Q000276:immunology
D000953:Antigens, Protozoan; D000939:Epitopes; D010446:Peptide Fragments