Humoral response to defined epitopes of tubercle bacilli in adult pulmonary and child tuberculosis

Abstract

In order to investigate the humoral response to tuberculosis in different categories of patients, serum antibody levels to six epitopes ofMycobacterium tuberculosis in adult pulmonary and child tuberculosis were determined. Serum antibody titres were determined by competitive inhibition with radio-labelled murine monoclonal antibodies in 67 adults and 85 children with tuberculosis and in 79 age-matched controls. BCG vaccination (n=39) and self-healed tuberculosis (n=11) in adults gave rise to higher antibody titres to TB68, TB23 and TB72 epitopes (all p−4). The diagnostic sensitivity, with a 95 % specificity, was best with the combination of probes TB23, TB68, TB72 for sputum-positive (85 %) and TB78, ML34 (53 %) for sputum-negative patients. Antibody titres in children with tuberculosis were lower than in adult patients; diagnostic sensitivity in histologically or microbiologically proven cases (n=18) was only 44 %, while that in mediastinal lymphadenitis (n=67) was 13.5 %. This study suggests that the magnitude and specificity of the humoral response to tubercle bacilli varies with site and severity of infection; the implications for pathogenesis or protective immunity are discussed.