Impact of age and sex on mycobacterial immunity in an area of high tuberculosis incidence
OBJECTIVE: To determine the impact of age and sex on assay positivity and on the extent of reactivity of both TST and T-cell assays in young persons in an area of South Africa with high TB transmission.
RESULTS: Age had a strong impact on assay positivity for all seven immune phenotypes tested (P < 0.0007). Among positive responders, the extent of purified protein derivative (PPD) triggered IFN-γ release (P < 0.003) was sensitive to age. ESAT-6 triggered IFN-γ release (day 7, P = 0.03) and the frequency of PPD-specific IFN-γ+CD4+ (P = 0.03) and IFN-γ+CD8+ cells (P = 0.04) were weakly dependent on age. By contrast, the extent of TST induration was insensitive to age (P > 0.05), and sex had no significant impact on any phenotype measured (P > 0.05). The high proportion of positive responders in the 1–10 year age-group observed with long-term whole blood assays, but not with 3-day assays and TST, suggests that long-term whole blood assays may be confounded by bacille Calmette-Guérin vaccination in this age group.
CONCLUSION: There is a significant impact of age, but not sex, on different assays of immune reactivity in this high TB transmission setting.
Document Type: Regular Paper
Affiliations: 1: McGill Centre for the Study of Host Resistance & Departments of Human Genetics and Medicine, McGill University, Montreal, Canada 2: South African Vaccine Initiative, Institute of Infectious Diseases and Molecular Medicine, Health Sciences Faculty, University of Cape Town, Cape Town, South Africa 3: Department of Infectious Disease Immunology, Statens Serum Institute, Copenhagen, Denmark 4: Paediatric Infectious Diseases Unit, School of Child and Adolescent Health, Red Cross Children's Hospital, University of Cape Town, Cape Town, South Africa 5: Desmond Tutu TB Centre, Department of Paediatrics and Child Health, Faculty of Health Sciences, Stellenbosch University, Tygerberg, South Africa 6: Faculté de Médecine Necker, Université de Paris Descartes, Paris, France
Publication date: 2010-08-01
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