title: The effect of tuberculin skin test and BCG vaccination on the expansion of PPD-specific IFN-gamma producing cells ex vivo.
abstract: 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.
authors.affiliation: Bacterial Diseases Programme, Medical Research Council, P.O. Box 273, Banjul, Gambia. mota@mrc.gm
authors.forename: Martin O C
authors.initials: MO
authors.lastname: Ota
authors.forename: Roger H
authors.initials: RH
authors.lastname: Brookes
authors.forename: Philip C
authors.initials: PC
authors.lastname: Hill
authors.forename: Patrick K
authors.initials: PK
authors.lastname: Owiafe
authors.forename: Hannah B
authors.initials: HB
authors.lastname: Ibanga
authors.forename: Simon
authors.initials: S
authors.lastname: Donkor
authors.forename: Timothy
authors.initials: T
authors.lastname: Awine
authors.forename: Helen
authors.initials: H
authors.lastname: McShane
authors.forename: Richard A
authors.initials: RA
authors.lastname: Adegbola
mesh_terms: 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*
chemical_list: D032581:Tuberculosis Vaccines; D007371:Interferon-gamma