Endosomal recognition of Lactococcus lactis G121 and its RNA by dendritic cells is key to its allergy-protective effects.

Abstract

BACKGROUND:

Bacterial cowshed isolates are allergy protective in mice; however, the underlying mechanisms are largely unknown. We examined the ability of Lactococcus lactis G121 to prevent allergic inflammatory reactions.

OBJECTIVE:

We sought to identify the ligands and pattern recognition receptors through which L lactis G121 confers allergy protection.

METHODS:

L lactis G121-induced cytokine release and surface expression of costimulatory molecules by untreated or inhibitor-treated (bafilomycin and cytochalasin D) human monocyte-derived dendritic cells (moDCs), bone marrow-derived mouse dendritic cells (BMDCs), and moDC/naive CD4+ T-cell cocultures were analyzed by using ELISA and flow cytometry. The pathology of ovalbumin-induced acute allergic airway inflammation after adoptive transfer of BMDCs was examined by means of microscopy.

RESULTS:

L lactis G121-treated murine BMDCs and human moDCs released TH1-polarizing cytokines and induced TH1 T cells. Inhibiting phagocytosis and endosomal acidification in BMDCs or moDCs impaired the release of TH1-polarizing cytokines, costimulatory molecule expression, and T-cell activation on L lactis G121 challenge. In vivo allergy protection mediated by L lactis G121 was dependent on endosomal acidification in dendritic cells (DCs). Toll-like receptor (Tlr) 13-/- BMDCs showed a weak response to L lactis G121 and were unresponsive to its RNA. The TH1-polarizing activity of L lactis G121-treated human DCs was blocked by TLR8-specific inhibitors, mediated by L lactis G121 RNA, and synergistically enhanced by activation of nucleotide-binding oligomerization domain-containing protein (NOD) 2.

CONCLUSION:

Bacterial RNA is the main driver of L lactis G121-mediated protection against experimentally induced allergy and requires both bacterial uptake by DCs and endosomal acidification. In mice L lactis G121 RNA signals through TLR13; however, the most likely intracellular receptor in human subjects is TLR8.

• Authors: Karina Stein, Stephanie Brand, André Jenckel, Anna Sigmund, Zhijian James Chen, Carsten J Kirschning, Marion Kauth, Holger Heine
• Journal: The Journal of allergy and clinical immunology (J Allergy Clin Immunol) Vol. 139 Issue 2 Pg. 667-678.e5 (02 2017) ISSN: 1097-6825 [Electronic] United States
• PMID: 27544739 (Publication Type: Journal Article)
• Copyright: Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

Chemical References

• Antigens, Bacterial
• Cytokines
• NOD2 protein, human
• Nod2 Signaling Adaptor Protein
• RNA, Bacterial
• TLR8 protein, human
• Tlr13 protein, mouse
• Toll-Like Receptor 8
• Toll-Like Receptors

Topics

• Animals
• Antigens, Bacterial (immunology)
• Cattle
• Cells, Cultured
• Cytokines (metabolism)
• Dendritic Cells (immunology)
• Disease Models, Animal
• Endosomes (metabolism)
• Female
• Humans
• Lactococcus lactis (immunology)
• Lung (immunology)
• Mice
• Mice, Inbred BALB C
• Mice, Inbred C57BL
• Mice, Knockout
• Milk Hypersensitivity (immunology, prevention & control)
• Nod2 Signaling Adaptor Protein (metabolism)
• RNA, Bacterial (immunology)
• Th1 Cells (immunology)
• Toll-Like Receptor 8 (antagonists & inhibitors)
• Toll-Like Receptors (genetics)