Helminth species-specific effects on IFN-gamma producing T cells during active and latent tuberculosis

• BackgroundInterferon-gamma (IFN-gamma) is a key cytokine inducing protective immune responses during tuberculosis (TB) infection. Helminth-induced immune responses may affect IFN-gamma production by T cells, although its connection with disease severity and immune recovery during treatment is unexplored. We investigated the species-specific effect of helminths on the IFN-gamma production by T cells in relation to disease severity during active and latent TB infection (LTBI). MethodsIn this study, 69 active pulmonary TB patients (PTB), 28 with LTBI and 66 healthy controls were included. Active TB was diagnosed using GenXpert MTB/RIF while QuantiFERON test (QFT) was used for the screening of healthy community controls (CCs) and for the diagnosis of LTBI. Helminth infection was identified by routine diagnosis whereas clinical disease severity was evaluated by the TB score. Intracellular IFN-gamma production of T cells in stimulated peripheral blood mononuclear cells (PBMCs) was analyzed by flow cytometry using TB antigens (PPD), the polyclonal T cell activator staphylococcal enterotoxin B (SEB), or medium as unstimulated control. ResultsHelminth infected CCs and LTBI subjects showed a significant reduction of IFN-gamma(+) CD4(+) T cells by PPD-stimulation compared to non-helminth infected control groups. The significant reduction in the frequency of IFN-gamma(+) T cells in both latent and active PTB patients following SEB stimulation was mostly attributed to Schistosoma mansoni infection, whereas Ascaris lumbricoides, Schistosoma mansoni, and hookworm infection contributed equally in CCs. Following anti-helminthic and anti-TB treatment for 2 months, the frequency of IFN-gamma(+) CD4 T cells in helminth coinfected PTB was restored to levels of helminth negative PTB before treatment. Helminth coinfected PTB patients with an intermediate and severe clinical course had reduced capacity for production of IFN-gamma(+) T cells compared to the corresponding non-helminth infected PTB. ConclusionWe found a reduction in IFN-gamma producing T cells by helminth coinfection which was restored following anti-helminthic treatment. This reduction was helminth species-dependent in an exploratory sub-analysis and correlated to increased disease severity. Author summaryProtective immunity against tuberculosis (TB) requires a Th-1 response with cytokines like TNF and IFN-gamma which plays a key role in the recruitment and activation of immune cells. Helminth infection, on the other hand, can lead to induction of regulatory T cells and a Th-2 skewed response decreasing IFN-gamma in T cells. Decreased Th-1 responses could favor reactivation of latent TB infection (LTBI), although the helminth species-specific effect on IFN-gamma(+)CD4(+) T cells and the link to TB disease severity in patients with active pulmonary TB (PTB) have not been fully investigated. Therefore, blood cells (PBMCs) from healthy controls, LTBI individuals, and PTB patients were used to evaluate the impact of different helminths on the frequency of IFN-gamma(+)CD4(+) T cells, in Gondar Ethiopia. Ascaris lumbricoides, Schistosoma mansoni, and hookworm infection in healthy controls contributed equally to decreasing the frequency of IFN-gamma(+)CD4(+) T cells, whereas in both LTBI and PTB patients S. mansoni coinfection had the greatest impact on reducing IFN-gamma producing capacity of T cells. Decreased IFN-gamma producing capacity of T cells was correlated with increased TB disease severity, only in helminth coinfected PTB patients, and anti-helminthic therapy restored the IFN-gamma producing capacity of T cells at the 2 months follow-up.

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MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Immunologi inom det medicinska området (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Immunology in the medical area (hsv//eng)

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