gammadelta T cells are a component of early immunity against preerythrocytic malaria parasites.
We tested the hypothesis that gammadelta T cells are a component of an early immune response directed against preerythrocytic malaria parasites that are required for the induction of an effector alphabeta T-cell immune response generated by irradiated-sporozoite (irr-spz) immunization. gammadelta T-cell-deficient (TCRdelta(-/-)) mice on a C57BL/6 background were challenged with Plasmodium yoelii (17XNL strain) sporozoites, and then liver parasite burden was measured at 42 h postchallenge. Liver parasite burden was measured by quantification of parasite-specific 18S rRNA in total liver RNA by quantitative-competitive reverse transcription-PCR and by an automated 5' exonuclease PCR. Sporozoite-challenged TCRdelta(-/-) mice showed a significant (P < 0.01) increase in liver parasite burden compared to similarly challenged immunocompetent mice. In support of this result, TCRdelta(-/-) mice were also found to be more susceptible than immunocompetent mice to a sporozoite challenge when blood-stage parasitemia was used as a readout. A greater percentage of TCRdelta(-/-) mice than of immunocompetent mice progressed to a blood-stage infection when challenged with five or fewer sporozoites (odds ratio = 2.35, P = 0.06). TCRdelta(-/-) mice receiving a single irr-spz immunization showed percent inhibition of liver parasites comparable to that of immunized immunocompetent mice following a sporozoite challenge. These data support the hypothesis that gammadelta T cells are a component of early immunity directed against malaria preerythrocytic parasites and suggest that gammadelta T cells are not required for the induction of an effector alphabeta T-cell immune response generated by irr-spz immunization.
McKenna
K C
KC
Department of Microbiology, University of Maryland, Baltimore, Baltimore, Maryland 21201, USA.
Tsuji
M
M
Sarzotti
M
M
Sacci
J B
JB
Witney
A A
AA
Azad
A F
AF
D000818:Animals; D001769:Blood / Q000469:parasitology; D004912:Erythrocytes / Q000469:parasitology; D005260:Female; D008099:Liver / Q000469:parasitology; D008288:Malaria / Q000517:prevention & control; D017780:Malaria Vaccines / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010967:Plasmodium yoelii / Q000276:immunology*; D051381:Rats; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000502:physiology
D017780:Malaria Vaccines