Identification of human T-cell responses to Mycobacterium tuberculosis resuscitation-promoting factors in long-term latently infected individuals - PubMed (original) (raw)

Identification of human T-cell responses to Mycobacterium tuberculosis resuscitation-promoting factors in long-term latently infected individuals

Susanna Commandeur et al. Clin Vaccine Immunol. 2011 Apr.

Abstract

The Mycobacterium bovis BCG vaccine is the only tuberculosis (TB) vaccine available, yet it provides limited protection against pulmonary TB in adults and fails to protect against TB reactivation. We hypothesized that immunity against Mycobacterium tuberculosis "resuscitation-promoting factors" (Rpfs), which are small bacterial proteins that promote proliferation of dormant mycobacteria, may be relevant in the human immune response to M. tuberculosis. In previous unpublished work, we found that Rpfs Rv0867c and Rv2389c induced gamma interferon (IFN-γ) production in the blood of TB patients' healthy household contacts in several different African populations. Here we examine these two dominant Rpf antigens in more detail and define the nature of the responding T-cell subsets. Multiparameter cytokine profiling showed that Rv2389c and, to a lesser extent, Rv0867c were recognized by mycobacterium-responsive healthy Dutch individuals; peptide-scanning revealed several epitopes, including a single immunodominant epitope in Rv2389c. Rv0867c and, to a lesser extent, Rv2389c Rpf-specific T-cell responses were maintained for decades in long-term M. tuberculosis nonprogressors. Prominent Rv0867c-specific double- and single-cytokine-producing CD8(+) T-cell subset responses were found, including a large population of CD8(+) effector memory and effector T-cell subsets. We conclude that M. tuberculosis Rpf antigens are important targets in the human immune response to M. tuberculosis and represent interesting TB vaccine candidate antigens.

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Figures

Fig. 1.

Fig. 1.

Cytokine and chemokine profiling. PBMCs from healthy individuals (HC; n = 10), BCG-vaccinated individuals (BCG; n = 10), TST-positive individuals (TST; n = 10), and TB patients (TB; n = 9) were stimulated with Rv0867c and Rv2389c proteins and PPD for 6 days. Levels of IFN-γ (A), IL-1β (B), IL-6 (C), and TNF-α (D) were measured and corrected for background levels. Horizontal bars represent median cytokine production levels. Antigen stimuli: ○, Rv0867c; •, Rv2389c; and ▾, PPD. *, background not corrected.

Fig. 2.

Fig. 2.

Frequency of antigen-specific polyfunctional T cells in long-term M. tuberculosis nonprogressors. Shown is the frequency of antigen-specific CD4+ and CD8+ T cells in long-term latently infected elderly subjects (n = 12) producing combinations of IFN-γ, TNF-α, and IL-2 after stimulation for 16 h with Rv0867c (A) or Rv2389c (C) protein. Healthy individuals were also analyzed for their polyfunctional responses to Rv0867c (B) and Rv2389c (D). CD4+ T cells are indicated as closed circles and CD8+ T cells as open circles. Horizontal bars represent the median frequency of antigen-specific CD4+ and CD8+ T cells. Slices in the pie chart represent the fraction of single (blue)-, double (green)-, or triple (red)-positive CD4+ and CD8+ T cells for Rv0867c (E). Expression of T-cell memory markers CCR7 and CD45RA was analyzed and is shown for the largest T-cell population identified: Rv0867c-specific IFN-γ and TNF-α double-positive CD8+ T cells (F). Effector memory T cells are CCR7− and CD45RA−, central memory T cells are CCR7+ and CD45RA−, naive T cells are CCR7+ and CD45RA+, and effector T cells are CCR7− and CD45RA+.

Fig. 3.

Fig. 3.

Integrated mean fluorescence intensity (iMFI) of IFN-γ-, TNF-α-, and/or IL-2-producing CD8+ T cells. Shown is a box and whisker plot representing the iMFI values of CD8+ T cells from long-term nonprogressors (n = 8) in response to Rv0867c protein. iMFI is the product value of multiplication of the frequency of CD8+ T cells with the indicated (poly- or mono-) cytokine profiles with the MFI of IFN-γ (A) and TNF-α (B) produced by these T-cell subsets. The horizontal line represents the median, the lower boundary of the box represents the 25th percentile, and the upper boundary represents the 75th percentile. Whiskers extend from the box to the highest and lowest values.

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