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Hydrophobic Mycobacterial Antigens Elicit Polyfunctional T Cells in Mycobacterium bovis Immunized Cattle: Association With Protection Against Challenge?

Authors :
Benedictus L
Steinbach S
Holder T
Bakker D
Vrettou C
Morrison WI
Vordermeier M
Connelley T
Source :
Frontiers in immunology [Front Immunol] 2020 Nov 12; Vol. 11, pp. 588180. Date of Electronic Publication: 2020 Nov 12 (Print Publication: 2020).
Publication Year :
2020

Abstract

Bovine tuberculosis (bTB), caused by Mycobacterium bovis , is a chronic disease of cattle with a detrimental impact on food quality and production. Research on bTB vaccines has predominantly been focused on proteinaceous antigens. However, mycobacteria have a thick and intricate lipid outer layer and lipids as well as lipopeptides are important for immune-evasion and virulence. In humans, lipid extracts of M. tuberculosis have been shown to elicit immune responses effective against M. tuberculosis in vitro . Chloroform-methanol extraction (CME) was applied to M. bovis BCG to obtain a hydrophobic antigen extract (CMEbcg) containing lipids and lipopeptides. CMEbcg stimulated IFN-γ <superscript>+</superscript> IL-2 <superscript>+</superscript> and IL-17A <superscript>+</superscript> IL-22 <superscript>+</superscript> polyfunctional T cells and elicited T cell responses with a Th1 and Th17 cytokine release profile in both M. bovis BCG vaccinated and M. bovis challenged calves. Lipopeptides were shown to be the immunodominant antigens in CMEbcg, stimulating CD4 T cells via MHC class II. CMEbcg expanded T cells killed CMEbcg loaded monocytes and the CMEbcg-specific CD3 T cell proliferative response following M. bovis BCG vaccination was the best predictor for reduced pathology following challenge with M. bovis . Although the high predictive value of CMEbcg-specific immune responses does not confirm a causal relationship with protection against M. bovis challenge, when taking into account the in vitro antimycobacterial phenotype of CMEbcg-specific T cells (e.g. Th1/Th17 cytokine profile), it is indicative that CMEbcg-specific immune responses could play a functional role in immunity against M. bovis . Based on these findings we conclude that lipopeptides of M. bovis are potential novel subunit vaccine candidates and that further studies into the functional characterization of lipopeptide-specific immune responses together with their role in protection against bovine tuberculosis are warranted.<br /> (Copyright © 2020 Benedictus, Steinbach, Holder, Bakker, Vrettou, Morrison, Vordermeier and Connelley.)

Details

Language :
English
ISSN :
1664-3224
Volume :
11
Database :
MEDLINE
Journal :
Frontiers in immunology
Publication Type :
Academic Journal
Accession number :
33281817
Full Text :
https://doi.org/10.3389/fimmu.2020.588180