Blockade of bovine PD-1 increases T cell function and inhibits bovine leukemia virus expression in B cells in vitro

Ryoyo Ikebuchi,Shiro Murata,Kazumasa Yokoyama,Tomohiro Okagawa,Kazuhiko Ohashi,Satoru Konnai,Yasuhiko Suzuki,Chie Nakajima

doi:10.1186/1297-9716-44-59

Abstract

Programmed death-1 (PD-1) is a known immunoinhibitory receptor that contributes to immune evasion of various tumor cells and pathogens causing chronic infection, such as bovine leukemia virus (BLV) infection. First, in this study, to establish a method for the expression and functional analysis of bovine PD-1, hybridomas producing monoclonal antibodies (mAb) specific for bovine PD-1 were established. Treatment with these anti-PD-1 mAb enhanced interferon-gamma (IFN-γ) production of bovine peripheral blood mononuclear cells (PBMC). Next, to examine whether PD-1 blockade by anti-PD-1 mAb could upregulate the immune reaction during chronic infection, the expression and functional analysis of PD-1 in PBMC isolated from BLV-infected cattle with or without lymphoma were performed using anti-PD-1 mAb. The frequencies of both PD-1+ CD4+ T cells in blood and lymph node and PD-1+ CD8+ T cells in lymph node were higher in BLV-infected cattle with lymphoma than those without lymphoma or control uninfected cattle. PD-1 blockade enhanced IFN-γ production and proliferation and reduced BLV-gp51 expression and B-cell activation in PBMC from BLV-infected cattle in response to BLV-gp51 peptide mixture. These data show that anti-bovine PD-1 mAb could provide a new therapy to control BLV infection via upregulation of immune response.

Highlights

Immunoinhibition is considered one of the reasons responsible for the refractory nature of several types of tumors and chronic infections [1,2]
Four hybridomas (2C12, 2H7, 3G2, and 5D2) were cloned and confirmed as clones producing monoclonal antibodies (mAb) that reacted with Cos-7 expressing Programmed death-1 (PD-1) but not with cells transfected with the control vector (Table 1 and Figure 1a)
Anti-PD-1 mAb react with bovine lymphocytes To confirm that anti-PD-1 mAb can recognize bovine PD-1 naturally expressed on bovine lymphocytes, we examined surface PD-1 expression on CD4+ and CD8+ T cells as well as IgM+ B cells freshly isolated or stimulated by mitogens, such as Pokeweed mitogen (PWM) and phorbol 12-myristate acetate (PMA)/ionomycin in vitro

Summary

Introduction

Immunoinhibition is considered one of the reasons responsible for the refractory nature of several types of tumors and chronic infections [1,2]. The suppression of both CD4+ T cell proliferation and cytotoxic immune response against BLV antigens is correlated to disease progression [3,6]. In various types of chronic infections and tumors, PD-1 and its ligand, PD-ligand-1 (PD-L1) play an important role in inhibiting chronically activated T cells specific for pathogens, resulting in the induction of “exhausted” T cells [5,7,8,9]. Treatment with monoclonal antibodies (mAb) specific for either PD-1 or PD-L1 reactivates exhausted immune responses such as proliferation, cytokine production, and cytotoxic capabilities of exhausted T cells ex vivo [7,10], and in vivo [11,12], and was tested in clinical trials with cancer patients [13,14]

Methods

Results

Conclusion