Hepcidin exerts a negative immunological effect in pulmonary tuberculosis without HIV co-infection, prolonging the time to culture-negative

Highlights

• In contrast to HIV-related tuberculosis, evaluations of the influence of hepcidin in non-HIV-related tuberculosis have been limited.
• Non-HIV tuberculosis patients with higher hepcidin levels required a longer time to become culture-negative in this study.
• The effect of hepcidin on time for culture to culture-negative was the most relevant in other clinical factors using multivariate analysis.
• The negative correlation between hepcidin levels and spot numbers in the positive control wells of the T-SPOT.TB assay was identified.
• Hepcidin reduced interferon-gamma production in a dose-dependent manner on in vitro examination with Jurkat cells stimulated with PHA.

Abstract

Objectives

A major regulatory peptide in iron metabolism, hepcidin, has been shown to predict mortality in HIV-infected tuberculosis patients. The aim of this study was to evaluate whether plasma hepcidin levels on admission can be used to predict the treatment outcome of patients with smear-positive pulmonary tuberculosis (PTB) without HIV co-infection.

Methods

In this prospective observational study, a total of 35 PTB patients with Mycobacterium tuberculosis-positive sputum smears were enrolled. The relationship between plasma hepcidin levels on admission and the time period to sputum culture-negative was explored.

Results

Plasma hepcidin levels of PTB patients were significantly higher than those of healthy subjects (p < 0.001). A positive correlation between hepcidin level on admission and the period until culture-negative was also observed (r = 0.46, p = 0.006). Furthermore, the hepcidin level showed a negative correlation with spot numbers in the positive control wells of the T-SPOT.TB assay; thus the effect of the peptide on interferon-gamma production in T cells was explored. Hepcidin reduced interferon-gamma gene transcription and interferon-gamma production in a dose-dependent manner in Jurkat cells stimulated with phytohaemagglutinin, an antigen non-specific stimulation.

Measurement of plasma hepcidin levels

Peripheral blood specimens were collected in vacutainer tubes containing ethylenediaminetetraacetic acid (EDTA)-Na (Terumo, Tokyo, Japan). Whole blood samples were centrifuged for 10 min at 200 g (1500 rpm). Then, supernatant plasma samples were dispensed and preserved at −80 °C until measurement. Measurement of plasma hepcidin levels was conducted using an ELISA kit (Hepcidin 25 Bioactive; DRG Instruments GmbH, Marburg, Germany) according to the manufacturer’s instructions.

Conclusions

These findings indicate that hepcidin alters immunological reactions against M. tuberculosis infection and has an influence on the outcomes of PTB patients without HIV co-infection.