Effect of Ascaris Lumbricoides specifc IgE on tuberculin skin test responses in children in a high-burden setting: a cross-sectional community-based study

Abstract

M. tuberculosis (M.tb) is associated with enhanced T helper cell type 1 (Th1) immune responses while helminth infection is associated with T helper cell type 2 (Th2) immune responses. The aim of this study was to investigate whether helminth infection could influence the ability to generate an appropriate Th1 immune response that is characterized by a positive tuberculin skin test (TST), in M.tb exposed children. A community-based, cross sectional household contact tracing study was carried out, using matched enrolment of HIV negative children with and without documented household M.tb exposure. The study documented demographics, clinical characteristics, HIV status, M.tb exposure (using a standard contact score) and M.tb infection status (TST greater than or  = 10 mm). Ascaris lumbricoides-specific IgE was used as proxy for Ascaris infection/exposure. Of 271 children (median age 4 years (range: 4 months to 15 years)) enrolled, 65 participants (24%) were serum positive for Ascaris IgE. There were 168 (62%) children with a documented household tuberculosis contact and 107 (40%) were (TST) positive overall. The preliminary findings highlight a high prevalence of both Ascaris exposure/infection and M.tb infection in children in an urban setting. Helminth exposure/infection may reduce the immune response following M.tb exposure when controlling for epidemiological and clinical covariates. These findings might be relevant to the interpretation of immunological tests of M.tb infection in children