Clinical efficacy of the combined treatment of anti-PD-L1 rat-bovine chimeric antibody with a COX-2 inhibitor in calves infected with Mycoplasma bovis

Mycoplasma bovis (M. bovis) is a highly contagious pathogen and M. bovis-associated diseases, particularly pneumonia, occur predominantly as herd enzootics, causing considerable economic losses because of calf mortality, weight loss in surviving calves. In our previous studies, the programmed death-1(PD-1)/ PD-ligand 1 (PD-L1) pathway and prostaglandin E2 (PGE2) were shown to be involved in the immunosuppression during chronic infectious diseases in cattle. In this study, the efficacy of dual blockade of the PD-1/PD-L1 pathway and PGE2 in M. bovis infection in vivo was investigated using anti-bovine PDL1 rat-bovine chimeric antibody, Boch4G12, and cyclooxygenase 2 (COX-2) inhibitor, meloxicam. The calves treated with Boch4G12 and meloxicam significantly enhanced M. bovis-specific IFN-γ response after the administration. On the other hand, IFN-γ response was not activated in the controls and cattle treated with meloxicam alone throughout the experimental period. Interestingly, bacterial loads in nasal discharge and bronchoalveolar lavage fluid among calves treated with Boch4G12 with or without meloxicam were significantly decreased. These results suggest that the combination of anti-PD-L1 antibody with a COX-2 inhibitor is a candidate for therapeutic applications in calves infected with M. bovis

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

【Introduction】 Bovine 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. 【Methods】 In 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. 【Results】 Expectedly, 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. 【Conclusions】 These 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 E_2 and the Enhancement of IFN-γ by Anti-PD-L1 Antibody Combined With a COX-2 Inhibitor in Mycoplasma bovis Infection

Bovine mycoplasmosis caused by Mycoplasma bovis results in pneumonia and mastitis in cattle. We previously demonstrated that the programmed death_1 (PD_)/PD-ligand _1 (PD-L_1) pathway is involved in immune dysfunction during M. bovis infection and that prostaglandin E_2 (PGE_2) suppressed immune responses and upregulated PD-L_1 expression in Johne\u27s disease, a bacterial infection in cattle. In this study, we investigated the role of PGE_2 in immune dysfunction and the relationship between PGE_2 and the PD-1/PD-L1 pathway in M. bovis infection. In vitro stimulation with M. bovis upregulated the expressions of PGE_2 and PD-L_1 presumably via Toll-like receptor 2 in bovine peripheral blood mononuclear cells (PBMCs). PGE_2 levels of peripheral blood in infected cattle were significantly increased compared with those in uninfected cattle. Remarkably, plasma PGE_2 levels were positively correlated with the proportions of PD-L_1^+ monocytes in M. bovis-infected cattle. Additionally, plasma PGE_2 production in infected cattle was negatively correlated with M. bovis-specific interferon (IFN)-γ production from PBMCs. These results suggest that PGE_2 could be one of the inducers of PD-L1 expression and could be involved in immunosuppression during M. bovis infection. In vitro blockade assays using anti-bovine PD-L_1 antibody and a cyclooxygenase 2 inhibitor significantly upregulated the M. bovis-specific IFN-γ response. Our study findings might contribute to the development of novel therapeutic strategies for bovine mycoplasmosis that target PGE_2 and the PD_/PD-L_1 pathway

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

Bovine mycoplasmosis caused by Mycoplasma bovis results in pneumonia and mastitis in cattle. We previously demonstrated that the programmed death 1 (PD-1)/PD-ligand 1 (PD-L1) pathway is involved in immune dysfunction during M. bovis infection and that prostaglandin E-2 (PGE(2)) suppressed immune responses and upregulated PD-L1 expression in Johne's disease, a bacterial infection in cattle. In this study, we investigated the role of PGE(2) in immune dysfunction and the relationship between PGE(2) and the PD-1/PD-L1 pathway in M. bovis infection. In vitro stimulation with M. bovis upregulated the expressions of PGE(2) and PD-L1 presumably via Toll-like receptor 2 in bovine peripheral blood mononuclear cells (PBMCs). PGE(2) levels of peripheral blood in infected cattle were significantly increased compared with those in uninfected cattle. Remarkably, plasma PGE(2) levels were positively correlated with the proportions of PD-L1(+) monocytes in M. bovis-infected cattle. Additionally, plasma PGE(2) production in infected cattle was negatively correlated with M. bovis-specific interferon (IFN)-gamma production from PBMCs. These results suggest that PGE(2) could be one of the inducers of PD-L1 expression and could be involved in immunosuppression during M. bovis infection. In vitro blockade assays using anti-bovine PD-L1 antibody and a cyclooxygenase 2 inhibitor significantly upregulated the M. bovis-specific IFN-gamma response. Our study findings might contribute to the development of novel therapeutic strategies for bovine mycoplasmosis that target PGE(2) and the PD-1/PD-L1 pathway