Enhancing Virus-Specific Immunity In Vivo by Combining Therapeutic Vaccination and PD-L1 Blockade in Chronic Hepadnaviral Infection
Jia Liu,
Ejuan Zhang,
Zhiyong Ma,
Weimin Wu,
Anna Kosinska,
Xiaoyong Zhang,
Inga Möller,
Pia Seiz,
Dieter Glebe,
Baoju Wang,
Dongliang Yang,
Mengji Lu,
Michael Roggendorf mail
Published: January 02, 2014
DOI: 10.1371/journal.ppat.100385
Abstract
Hepatitis B virus (HBV) persistence is facilitated by exhaustion of CD8 T cells that express the inhibitory receptor programmed cell death-1 (PD-1). Improvement of the HBV-specific T cell function has been obtained in vitro by inhibiting the PD-1/PD-ligand 1 (PD-L1) interaction. In this study, we examined whether in vivo blockade of the PD-1 pathway enhances virus-specific T cell immunity and leads to the resolution of chronic hepadnaviral infection in the woodchuck model. The woodchuck PD-1 was first cloned, characterized, and its expression patterns on T cells from woodchucks with acute or chronic woodchuck hepatitis virus (WHV) infection were investigated. Woodchucks chronically infected with WHV received a combination therapy with nucleoside analogue entecavir (ETV), therapeutic DNA vaccination and woodchuck PD-L1 antibody treatment. The gain of T cell function and the suppression of WHV replication by this therapy were evaluated. We could show that PD-1 expression on CD8 T cells was correlated with WHV viral loads during WHV infection. ETV treatment significantly decreased PD-1 expression on CD8 T cells in chronic carriers. In vivo blockade of PD-1/PD-L1 pathway on CD8 T cells, in combination with ETV treatment and DNA vaccination, potently enhanced the function of virus-specific T cells. Moreover, the combination therapy potently suppressed WHV replication, leading to sustained immunological control of viral infection, anti-WHs antibody development and complete viral clearance in some woodchucks. Our results provide a new approach to improve T cell function in chronic hepatitis B infection, which may be used to design new immunotherapeutic strategies in patients.
Introduction
Hepatitis B virus (HBV) infection evolves into a chronic liver disease and leads to severe sequelae in about 5% of infected adults and in a larger proportion of children. It is estimated that approximately 400 million people are chronically infected with HBV worldwide. There are two types of antiviral therapies currently available for chronic HBV: treatment with pegylated interferon alpha (PEG-IFNα) and nucleot(s)ide analogues, such as entecavir (ETV) and tenofovir. However, treatment with PEG-IFNα leads to a sustained antiviral response in only about 30% patients and is associated with side effects. The introduction of PEG-IFNα in combination with nucleoside analogues did not significantly increase the rate of sustained responders [1], [2]. Although treatment with nucleoside analogues improves the clinical condition of chronic HBV patients, it is hampered by emergence of drug resistance mutations, and rebounding viremia after cessation of antiviral therapy [3], [4]. Therefore, alternative strategies to treat chronic HBV infection are urgently needed.
Persistent HBV infection is associated with functional exhaustion of virus-specific CD8 T cells [5]. This defect in virus-specific T cells is one of the primary reasons for the inability of the host to eliminate the persisting pathogen. Therefore, therapeutic vaccination, which aims to enhance the patient's own antiviral cellular immune response, has been considered as an alternative therapy. However, the efficacy of such strategies in patients has so far been disappointing [6], [7], [8]. Recent work suggests that the high viral load at the time of vaccination might explain the inefficient responses to therapeutic vaccination [9], [10]. Thus, it is important to develop a therapeutic vaccine strategy which could effectively boost endogenous T cell responses to control persistent viral infections.
Recent studies in chronic virus infection models indicate that the interaction between the inhibitory receptor programmed death-1 (PD-1) on lymphocytes and its ligands plays a critical role in T-cell exhaustion [11], [12], [13], [14]. In various human chronic infections, including HBV, high PD-1 levels are expressed by virus-specific T cells, and improvement of the T-cell function has been obtained in vitro by inhibition of the PD-1/PD-ligand 1 (PD-L1) interaction [15], [16], [17], [18], [19], [20], [21]. Moreover, in vivo blockade of PD-1/PD-L1 pathway has successfully been applied in mice persistently infected with lymphocytic choriomeningitis virus (LCMV) to restore the antiviral function of exhausted T cells, and hence improved the effect of the therapeutic vaccination [11], [22].
We have previously demonstrated that therapeutic DNA vaccines in combination with an antiviral nucleoside analogue result in a prolonged suppression of WHV replication in chronically WHV infected woodchucks [23]. Recently, we have also demonstrated that in vitro blockade of the woodchuck PD-1/PD-L pathway could restore the T cell functions in chronic WHV infection [24]. In this study, we examined whether in vivo blockade of the PD-1 pathway in combination with antiviral nucleoside analogue treatment and therapeutic vaccination could enhance CD8 T cell immunity and lead to the resolution of chronic WHV infection in the woodchuck model. Persistently WHV-infected woodchucks were first treated with antiviral drug ETV to decrease the viral replication, and then received therapeutic vaccination and PD-L1 antibody treatment. This combinatorial therapeutic vaccination potently enhanced WHV-specific CD8 T cell responses, resulted in absence of WHV DNA in plasma and seroconversion to anti-WHs in two animals. However, residual WHV replication was still detectable in the liver of some animals. 作者: StephenW 时间: 2014-1-4 12:10