Mycobacterial growth inhibition is associated with trained innate immunity
Simone A. Joosten, … , Mihai G. Netea, Tom H.M. Ottenhoff
Simone A. Joosten, … , Mihai G. Netea, Tom H.M. Ottenhoff
Published February 20, 2018
Citation Information: J Clin Invest. 2018;128(5):1837-1851. https://doi.org/10.1172/JCI97508.
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Research Article Immunology Infectious disease

Mycobacterial growth inhibition is associated with trained innate immunity

Abstract

The lack of defined correlates of protection hampers development of vaccines against tuberculosis (TB). In vitro mycobacterial outgrowth assays are thought to better capture the complexity of the human host/Mycobacterium tuberculosis (Mtb) interaction. Here, we used a mycobacterial growth inhibition assay (MGIA) based on peripheral blood mononuclear cells to investigate the capacity to control outgrowth of bacille Calmette-Guérin (BCG). Interestingly, strong control of BCG outgrowth was observed almost exclusively in individuals with recent exposure to Mtb, but not in (long-term) latent TB infection, and only modestly in BCG vaccinees. Mechanistically, control of mycobacterial outgrowth strongly correlated with the presence of a CD14dim monocyte population, but also required the presence of T cells. The nonclassical monocytes produced CXCL10, and CXCR3 receptor blockade inhibited the capacity to control BCG outgrowth. Expression of CXCR3 splice variants was altered in recently Mtb-exposed individuals. Cytokines previously associated with trained immunity were detected in MGIA supernatants, and CXCL9, CXCL10, and CXCL11 represent new markers of trained immunity. These data indicate that CXCR3 ligands are associated with trained immunity and are critical factors in controlling mycobacterial outgrowth. In conclusion, control of mycobacterial outgrowth early after exposure to Mtb is the result of trained immunity mediated by a CXCL10-producing nonclassical CD14dim monocyte subset.

Authors

Simone A. Joosten, Krista E. van Meijgaarden, Sandra M. Arend, Corine Prins, Fredrik Oftung, Gro Ellen Korsvold, Sandra V. Kik, Rob J.W. Arts, Reinout van Crevel, Mihai G. Netea, Tom H.M. Ottenhoff

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Figure 5

CXCR3 is key in determining mycobacterial outgrowth control.

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CXCR3 is key in determining mycobacterial outgrowth control. PBMCs were ...
PBMCs were infected with live BCG and rotated for 4 days, and samples were incubated in MGIT tubes in the BACTEC machine. (A) A CXCR3 receptor antagonist (NBI-74430) was added daily during the MGIA incubation period to inhibit activity of CXCL10; this reverted the capacity to control mycobacterial outgrowth. Data represent 11 donors with MGIA control run in 2 independent experiments; differences were assessed using the Wilcoxon matched-pairs signed-rank test. (B) Similar to A, addition of the CXCR3 receptor antagonist during the MGIA assay. Data represent 27 donors without MGIA control run in 3 independent experiments; differences were assessed using the Wilcoxon matched-pairs signed-rank test. (C) CXCL10 production was measured in supernatants of the MGIA assay at day 4 of coculture in samples with MGIA control or no MGIA control, in the absence or presence of NBI-74430, the CXCR3 antagonist. Data are expressed as median. (D) CXCR3 splice variants were determined by real-time quantitative reverse transcriptase PCR. ΔCt was calculated for both CXCR3A and CXCR3B using the in-well GAPDH control. Subsequently, the ratio of CXCR3A over CXCR3B was calculated and plotted. Data were compared using the Kruskal-Wallis test. Controls, n = 33; BCG, n = 16; exposed, n = 63; LTBI, n = 26; TB, n = 16. (E) The percentage of Tcm cells was plotted for donors with a low frequency of CD14dim monocytes producing CXCL10 (<3%). Good, n = 11; intermediate, n = 20; no, n = 54. (F) The percentage of Tcm cells plotted for donors with a high frequency of CD14dim monocytes producing CXCL10 (>3%). Groups were compared using the Kruskal-Wallis test. Good, n = 22; intermediate, n = 22; no, n = 15. (G) MGIA assay with PBMCs and isolated fractions of monocytes with or without T cells. Cells were separated and combined in various ratios before infection with live BCG and 4-day coculture. Boxes and whiskers indicate donors that lack MGIA control (n = 8); lines indicate 3 individual donors with MGIA control.