Number of cells from Plasmodium falciparum-immune donors that produce gamma interferon in vitro in response to Pf155/RESA, a malaria vaccine candidate antigen.
Secretion of gamma interferon (IFN-gamma) in response to stimulation of Plasmodium falciparum-primed T cells by specific antigens may be a useful indicator of cellular immunity to malaria. An enzyme-linked immunospot (ELISPOT) assay designed to detect IFN-gamma at the single-cell level was used to study IFN-gamma-producing cells from P. falciparum-primed donors from The Gambia after in vitro stimulation with various malarial antigens. IFN-gamma secreted into the culture supernatant was measured by conventional enzyme-linked immunosorbent assay (ELISA). There was a good correlation in individual donors between the level of IFN-gamma secreted into the culture supernatant and the number of IFN-gamma-secreting cells. However, the ELISPOT assay was apparently more sensitive in demonstrating low levels of IFN-gamma production than the ELISA was. Thus after stimulation with crude P. falciparum antigen from infected erythrocytes, 72% of the primed donors responded positively in the ELISPOT assay but only 55% responded positively in the ELISA. When stimulated with synthetic peptides representing immunodominant epitopes of the malarial antigen Pf155/RESA, a vaccine candidate, 31 to 55% responded in the ELISPOT assay and 21 to 36% responded in the ELISA. Unprimed Europeans did not respond positively to these antigens in either of the assays, and background in antigen-free controls was generally low. These results indicate that measurement of IFN-gamma by the ELISPOT assay or ELISA should have wide applications in large-scale epidemiological studies of malaria immunity. In addition, the ELISPOT assay makes it possible to analyze the T cells responding to malarial antigens in terms of both numbers and functional heterogeneity.
Department of Immunology, University of Stockholm, Sweden.
L
L
Kabilan
M
M
Troye-Blomberg
G
G
Andersson
E M
EM
Riley
H P
HP
Ekre
H C
HC
Whittle
P
P
Perlmann
D000328:Adult; D000368:Aged; D000818:Animals; D000954:Antigens, Surface / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D005714:Gambia / Q000453:epidemiology; D006801:Humans; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000096:biosynthesis*; D008288:Malaria / Q000453:epidemiology / Q000276:immunology*; D008875:Middle Aged; D010963:Plasmodium falciparum; D015800:Protozoan Proteins / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology* / Q000469:parasitology; D014612:Vaccines / Q000276:immunology
D000954:Antigens, Surface; D000939:Epitopes; D015800:Protozoan Proteins; D014612:Vaccines; C050256:ring-infected erythrocyte surface antigen (RESA), Plasmodium falciparum; D007371:Interferon-gamma