Associations of Schistosoma mansoni Infection, Latent Tuberculosis, Host Interferon-γ Concentrations, and Praziquantel Treatment in Tanzanian Adults

Latent tuberculosis infection (LTBI) and Schistosoma mansoni are common in Africa, and helminth-induced immunomodulation may affect LTBI detection. This study aimed to assess whether S. mansoni infection affects LTBI detection by the QuantiFERON-TB Gold Plus (QFT-Plus) assay and alters serum interferon-γ (IFN-γ) concentrations in response to Mycobacterium tuberculosis (Mtb) antigens at baseline and after 1 year, during which participants with S. mansoni infection received praziquantel treatment. At baseline, 65 individuals with schistosome infection had lower average IFN-γ concentrations in TB1-stimulated QFT-Plus supernatants compared with 83 uninfected individuals (10.4 versus 51.9 pg/mL, P = 0.038). Although not statistically significant, QFT-Plus test positivity rate was unexpectedly slightly higher among adults with schistosome infection at baseline (26.2% versus 18.1%, P = 0.24). The incidence over 12 months was higher posttreatment in participants initially infected with S. mansoni compared with those uninfected (13.9% [n = 5/36] versus 4.2% [n = 2/48], P = 0.13). By 12 months, IFN-γ concentrations were comparable between the two groups (53.8 versus 33.5 pg/mL, respectively, P = 0.56). Individuals who cleared S. mansoni infection experienced a nearly 12-fold increase in IFN-γ levels relative to those who remained uninfected, although this difference did not reach statistical significance (P = 0.17). In conclusion, baseline S. mansoni infection was associated with suppressed IFN-γ responses to Mtb antigens, suggesting helminth-induced immune dampening. Praziquantel treatment may partially restore TB-specific immune responses and facilitate LTBI detection. These findings highlight the potential role of S. mansoni as a critical cofactor affecting LTBI diagnosis in schistosomiasis-endemic regions.