Brucella abortus down-regulates MHC class II by the IL-6-dependent inhibition of CIITA through the downmodulation of IFN regulatory factor-1 (IRF-1)

Velasquez LN, Milillo MA, Delpino MV, Trotta A, Fernandez P, Pozner RG, Lang R, Balboa L, Giambartolomei GH, Barrionuevo P (2017)

Publication Type: Journal article

Publication year: 2017

Journal

Journal of Leukocyte Biology Society for Leukocyte Biology

Book Volume: 101

Pages Range: 759-773

Journal Issue: 3

DOI: 10.1189/jlb.4A0416-196R

Abstract

Brucella abortus is an intracellular pathogen capable of surviving inside of macrophages. The success of B. abortus as a chronic pathogen relies on its ability to orchestrate different strategies to evade the adaptive CD4(+) T cell responses that it elicits. Previously, we demonstrated that B. abortus inhibits the IFN-?-induced surface expression of MHC class II (MHC-II) molecules on human monocytes, and this phenomenon correlated with a reduction in antigen presentation. However, the molecular mechanisms, whereby B. abortus is able to down-regulate the expression of MHC-II, remained to be elucidated. In this study, we demonstrated that B. abortus infection inhibits the IFN-?-induced transcription of MHC-II, transactivator (CIITA) and MHC-II genes. Accordingly, we observed that the synthesis of MHC-II proteins was also diminished. B. abortus was not only able to reduce the expression of mature MHC-II, but it also inhibited the expression of invariant chain (Ii)-associated immature MHC-II molecules. Outer membrane protein 19 (Omp19), a prototypical B. abortus lipoprotein, diminished the expression of MHC-II and CIITA transcripts to the same extent as B. abortus infection. IL-6 contributes to these down-regulatory phenomena. In addition, B. abortus and its lipoproteins, through IL-6 secretion, induced the transcription of the negative regulators of IFN-? signaling, suppressor of cytokine signaling (SOCS)-1 and -3, without interfering with STAT1 activation. Yet, B. abortus lipoproteins via IL-6 inhibit the expression of IFN regulatory factor 1 (IRF-1), a critical regulatory transcription factor for CIITA induction. Overall, these results indicate that B. abortus inhibits the expression of MHC-II molecules at very early points in their synthesis and in this way, may prevent recognition by T cells establishing a chronic infection.

Involved external institutions

Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) / National Scientific and Technical Research Council AR Argentina (AR) Academia Nacional de Medicina de Buenos Aires AR Argentina (AR)

How to cite

APA:

Velasquez, L.N., Milillo, M.A., Delpino, M.V., Trotta, A., Fernandez, P., Pozner, R.G.,... Barrionuevo, P. (2017). Brucella abortus down-regulates MHC class II by the IL-6-dependent inhibition of CIITA through the downmodulation of IFN regulatory factor-1 (IRF-1). Journal of Leukocyte Biology, 101(3), 759-773. https://dx.doi.org/10.1189/jlb.4A0416-196R

MLA:

Velasquez, Lis N., et al. "Brucella abortus down-regulates MHC class II by the IL-6-dependent inhibition of CIITA through the downmodulation of IFN regulatory factor-1 (IRF-1)." Journal of Leukocyte Biology 101.3 (2017): 759-773.

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