IgG antibody response to Mycobacterium tuberculosis curli pili (MTP) in people from different geographical regions in Sub-Saharan Africa

Previously, a slot blot or an indirect enzyme-linked immunosorbent assay (ELISA) using a synthetic or purified MTP antigen, conceptually demonstrated IgG antibody induction in pulmonary TB patients, albeit with small sample sizes and differing sensitivity. Therefore, we evaluated an IgG MTP ELISA in larger populations from The Gambia (n = 549), Uganda (n = 161), and South Africa (n = 193), comprising human immunodeficiency virus (HIV) positive and negative, with microbiologically confirmed active TB. The association between the IgG level and demographic characteristics was determined by multivariate logistic regression. The sensitivity (44.8-61.2 %) and specificity (33.4-78.5 %) varied in the three cohorts. Anti-MTP antibody titres differed between the TB positive and negative groups within the South African and The Gambian cohorts (p < 0.001), but not in Uganda (p = 0.35). Antibodies were detected in HIV positive and negative patients and were reduced at 6-month follow-up after treatment (p > 0.067). The study verified previous findings that anti-MTP antibodies, and therefore MTP antigen, are produced during active TB. However, the accuracy of the MTP-IgG ELISA was low, and is therefore not suitable as a target product profile in the high burden TB areas investigated. Further studies are needed to clarify the variable reactivities in different geographical areas.