The effect of tuberculin skin test and BCG vaccination on the expansion of PPD-specific IFN-gamma producing cells ex vivo.
Understanding the immunogenicity of BCG in a population where it has failed will facilitate the design of new TB vaccines. We assessed the immunogenicity of M. bovis BCG over 12 months by ELISPOT assay. Forty-one adolescents and young Gambian male adults received a tuberculin skin test (TST) which was followed one week later by BCG vaccination, but the 23 control subjects received neither of these. TST alone significantly induced PPD-specific IFN-gamma producing cells. Twenty-three percent of subjects did not respond to BCG, which was associated with higher pre-existing ex vivo response to PPD. Paradoxically, amongst BCG responders there was a correlation between pre-existing response and subsequent response to BCG. We conclude that BCG is immunogenic, but this effector response is short-lived and can be limited in higher pre-existing anti-mycobacterial immunity, suggesting a possible threshold beyond which BCG immunogenicity is inhibited.
Ota
Martin O C
MO
Bacterial Diseases Programme, Medical Research Council, P.O. Box 273, Banjul, Gambia. mota@mrc.gm
Brookes
Roger H
RH
Hill
Philip C
PC
Owiafe
Patrick K
PK
Ibanga
Hannah B
HB
Donkor
Simon
S
Awine
Timothy
T
McShane
Helen
H
Adegbola
Richard A
RA
D000293:Adolescent; D000328:Adult; D002478:Cells, Cultured; D005714:Gambia; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis*; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008214:Lymphocytes / Q000276:immunology*; D008297:Male; D009163:Mycobacterium bovis / Q000276:immunology*; D014374:Tuberculin Test; D032581:Tuberculosis Vaccines / Q000276:immunology*
D032581:Tuberculosis Vaccines; D007371:Interferon-gamma