A pilot study on interaction between donkey tetherin and EIAV stains with different virulent and replication characteristics

Highlights

• It is the first time to use a lentivirus attenuation system to investigate the interaction between lentiviruse and host innate immune restriction factors.

• Do-Tetherin differently restricted the budding of virulent EIAV strains with different evolution levels.

• Env proteins of the three EIAV strains with different virulent and replication characteristics all can antagonize the restriction of do-Tetherin, but the antagonization effects declined from the virulent strain to the attenuated strains.

Abstract

Tetherin (BST-2) is an important host restriction factor that can inhibit the release of a diverse array of enveloped viruses from infected cells. Conversely, to facilitate their release and spread, many viruses have evolved various strategies to overcome the antiviral effect of tetherin in a species-specific manner. During the development of an attenuated equine infectious anemia virus (EIAV) vaccine in our laboratory, we found that serial passage of a field-isolated virulent EIAV strains in horse and donkey as well as the cultivated donkey cells, produces several typical EIAV strains, including EIAV_DV, EIAV_DLV, and EIAV_FDDV, which exhibit distinct virulence and replication features in vivo and in vitro. However, the role of host restriction factors in EIAV evolution during the serial passage is not well understood. This study aimed to evaluate whether these newly generated strains adapt differently to donkey tetherin (do-tetherin) based on their virulence. We found that do-tetherin exerts an inhibition on the release of the viral particles produced by all three strains, albeit with varying intensity: EIAV_DV < EIAV_DLV < EIAV_FDDV. Additionally, all three EIAV strains could counteract the restriction mediated by do-tetherin via their envelope proteins (Env) with varying strength: EIAV_DV > EIAV_DLV > EIAV_FDDV. These results indicate that donkey tetherin is involved in shaping of EIAV evolution during serial passage.

Introduction

Recent studies have extensively characterized a number of host restriction factors that restrict viruses at different stage during infection [1], [2], [3], [4], [5]. Tetherin was first identified by Neil et al. (2008) [6], who firstly characterized its ability to restrict the release of HIV-1 from the cell surface. Subsequently, more evidence demonstrates that tetherin exerts a broad antiviral effect on various viruses [7], [8], [9]. Indeed, many viruses encode viral proteins to antagonize the restriction mediated by tetherin through different strategies [10], [11], [12], [13], [14], [15].

Equine infectious anemia virus (EIAV) has the simplest genome structure among all lentiviruses [16], which makes it an ideal model system in which to study the role of specific viral genes in lentiviral replication and persistent infection [17]. Our laboratory has previously developed stably attenuated virulent EIAV strains using a specific passage attenuation system [18], [19]. The major strains generated by this process were EIAV_DV, EIAV_DLV, and EIAV_FDDV, each of which exhibit significant differences in virulence and replication both in vivo and in vitro.

Although equine and donkey tetherin were known to inhibit EIAV release from infected cells, it is unclear whether the arms race between tetherin and EIAV influences either the dynamic evolution of these EIAV strains or the attenuation of their virulence during the adaptive evolution process. To address this question, we evaluated the interplay between do-tetherin and these three different EIAV stains (EIAV_DV, EIAV_DLV, and EIAV_FDDV). Interestingly, we found that do-tetherin has a different antiviral effect on virulent vs. attenuated EIAV strains. Additionally, Env proteins of all three EIAV strains could antagonize the inhibition mediated by do-tetherin in different extent. These results advance our understanding on the interplay between host restriction factors and EIAV evolution.