Increase of cells expressing PD‐1 and PD‐L1 and enhancement of IFN‐γ production via PD‐1/PD‐L1 blockade in bovine mycoplasmosis

Abstract

IntroductionBovine mycoplasma, chiefly Mycoplasma bovis, is a pathogen that causes pneumonia, mastitis, arthritis, and otitis media in cattle. This pathogen exerts immunosuppressive effects, such as the inhibition of interferon production. However, the mechanisms involved in bovine mycoplasmosis have not been fully elucidated. In this study, we investigated the role of the programmed death‐1 (PD‐1)/programmed death‐ligand 1 (PD‐L1) pathway in immunosuppression in bovine mycoplasmosis.MethodsIn the initial experiments, we used enzyme‐linked immunosorbent assay to measure interferon‐γ (IFN‐γ) from peripheral blood mononuclear cells (PBMCs) isolated from cattle with mycoplasmosis.ResultsExpectedly, IFN‐γ production significantly decreased in cattle with mycoplasmosis compared with that in clinically healthy cattle. Concomitantly, flow cytometric analysis revealed that the proportions of PD‐1+CD4+ and PD‐L1+CD14+ cells significantly increased in peripheral blood of the infected cattle. Interestingly, the number of PD‐1+CD4+ and PD‐1+CD8+ T cells were negatively correlated with IFN‐γ production from PBMCs in bovine mycoplasmosis. Additionally, blockade of the PD‐1/PD‐L1 pathway in vitro by anti‐bovine PD‐1‐ and anti‐bovine PD‐L1 antibodies significantly upregulated the production of IFN‐γ from anti‐mycoplasma‐specific cells.ConclusionsThese results suggest that the PD‐1/PD‐L1 pathway could be involved in immune exhaustion of bovine mycoplasma‐specific T cells. In conclusion, our study opens up a new perspective in the therapeutic strategy for bovine mycoplasmosis by targeting the immunoinhibitory receptor pathways.

Upregulation of PD-L1 Expression by Prostaglandin E2 and the Enhancement of IFN-γ by Anti-PD-L1 Antibody Combined With a COX-2 Inhibitor in Mycoplasma bovis Infection

“…Then, we hypothesized that this immune dysfunction via PGE 2 -PD-L1 axis is commonly involved in bovine chronic infections. Therefore, this study focused on M. bovis infection, which is known to show immune dysfunction induced by exhausted T cell during the disease progression (11). In this study, we demonstrated that M. bovis induced PGE 2 production from monocytes in line with the upregulation of PD-L1 expression on monocytes (Figures 1A-F).…”

“…We previously reported that PD-1/PD-L1 blockade by antibovine PD-1/PD-L1 mAbs enhanced the M. bovis-specific IFN-γ response in vitro (11). Recent research showed that the combined blockade of the PD-1/PD-L1 pathway and PGE 2 by anti-PD-L1 mAb and a COX-2 inhibitor enhanced immune responses against several pathogens (18,19,31).…”

“…Our previous study showed that expression of PD-L1 on monocytes was increased in PBMCs of M. bovis-infected cattle (11). To confirm whether M. bovis directly upregulates PD-L1 expression in bovine PBMCs during in vitro infection, PBMCs from uninfected cattle were cultured with or without live M. bovis and PD-L1 expression was analyzed on monocytes by flow cytometry.…”

“…PD-1/PD-L1 could be a potential therapeutic target in patients with chronic infections. We previously demonstrated that the expression of PD-1 on T cells and PD-L1 on monocytes were significantly increased in M. bovis-infected cattle (11). Furthermore, the blockade of PD-1/PD-L1 pathway by antibodies in vitro activated immune responses in M. bovisinfected cattle (11).…”

“…We previously demonstrated that the expression of PD-1 on T cells and PD-L1 on monocytes were significantly increased in M. bovis-infected cattle (11). Furthermore, the blockade of PD-1/PD-L1 pathway by antibodies in vitro activated immune responses in M. bovisinfected cattle (11). Therefore, the T cell exhaustion caused by PD-1/PD-L1 might be involved in the immune dysfunction during bovine mycoplasma.…”