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Int J Tuberc Lung Dis. 2001 Jul;5(7):664-72.

Relationship between IFN-gamma and skin test responsiveness to Mycobacterium tuberculosis PPD in healthy, non-BCG-vaccinated young adults in Northern Malawi.

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1
Karonga Prevention Study, Chilumba, Malawi.

Abstract

SETTING:

Rural northern Malawi, where vaccination with BCG Glaxo (1077) provides protection against leprosy but not against pulmonary tuberculosis.

OBJECTIVE:

To evaluate the patterns of responsiveness to purified protein derivative of Mycobacterium tuberculosis (PPD) in terms of delayed type hypersensitivity (DTH) and interferon-gamma (IFN-gamma) production.

DESIGN:

IFN-gamma was measured in 6 day whole blood cultures diluted 1 in 10, stimulated with PPD RT48, and the results compared to the DTH response to PPD RT23. A total of 633 individuals aged 12 to 28 years, without prior BCG vaccination, were recruited.

RESULTS:

Overall, 63% of subjects made a positive IFN-gamma response (defined as >62 pg/ml), and 37% gave a DTH induration of >5 mm. A strong correlation between skin test and IFN-gamma responses was observed, although with interesting exceptions: 13/270 individuals with zero DTH showed IFN-gamma responses >500 pg/ml, and 7/53 individuals with >10 mm induration showed IFN-gamma responses < or = 62 pg/ml. The prevalence of skin test responsiveness increased with age, and was higher among older males than females; age-sex patterns were less clear for IFN-gamma production.

CONCLUSION:

The 6 day IFN-gamma response to PPD correlates well with Mantoux skin test induration. The discordant individuals may represent important subsets in terms of protective immunity and risk of clinical tuberculosis.

PMID:
11467373
[Indexed for MEDLINE]

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