Raabe M L, Issel C J, Montelaro R C
Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15261, USA.
Virology. 1999 Jul 5;259(2):416-27. doi: 10.1006/viro.1999.9772.
We have previously demonstrated a high propensity for enhancement of virus replication and disease resulting from experimental immunization of ponies with a baculovirus recombinant envelope (rgp90) vaccine from equine infectious anemia virus (EIAV). The current studies were undertaken to examine the correlation between the observed in vivo vaccine enhancement and in vitro assays for antibody-dependent enhancement (ADE) of EIAV replication. Toward this goal an optimized EIAV in vitro enhancement assay was developed using primary equine macrophage cells and used to evaluate the enhancement properties of immune serum taken from rgp90 immunized ponies that displayed various levels of vaccine enhancement after experimental challenge with EIAV. For comparison, we analyzed in parallel immune serum samples from a group of ponies immunized with a viral envelope subunit vaccine (LL-gp) that produced sterile protection from EIAV challenge. The results of these assays demonstrated that the rgp90 immune serum had a greater propensity for in vitro enhancement of EIAV replication than serum from the protected LL-gp immunized ponies; in vitro enhancement levels for the rgp90 immune sera averaged about 1.5, with a maximum enhancement value of about 2.0. While distinguishing between immune serum produced by the rgp90 and LL-gp immunizations, the in vitro enhancement assay failed to reliably correlate with the severity of in vivo enhancement observed among the rgp90 vaccine recipients. Vaccinated ponies that experienced moderate to no disease signs displayed levels of in vitro enhancement similar to those of ponies that experienced severe and fatal enhancement of disease after viral challenge. The observed in vitro enhancement was demonstrated to be dependent on serum immunoglobulin, but independent of complement. These studies demonstrate in the EIAV system that in vitro ADE assays appear to be relatively insensitive indicators of the severity of in vivo enhancement and that relatively low levels of in vitro ADE can be associated with severe to fatal enhancement of virus replication and disease in vivo. These observations suggest that relatively low levels of serum ADE observed in other lentivirus systems, including HIV-1, may have more profound effects on in vivo virus replication and disease than previously recognized.
我们之前已经证明，用来自马传染性贫血病毒（EIAV）的杆状病毒重组包膜（rgp90）疫苗对小马进行实验性免疫会导致病毒复制增强和疾病发生的可能性很高。当前的研究旨在检查观察到的体内疫苗增强作用与EIAV复制的抗体依赖性增强（ADE）体外试验之间的相关性。为实现这一目标，使用原代马巨噬细胞开发了一种优化的EIAV体外增强试验，并用于评估从rgp90免疫的小马中采集的免疫血清的增强特性，这些小马在EIAV实验性攻击后表现出不同程度的疫苗增强作用。为作比较，我们平行分析了一组用病毒包膜亚单位疫苗（LL-gp）免疫的小马的免疫血清样本，该疫苗对EIAV攻击产生了无菌保护。这些试验结果表明，rgp90免疫血清比受保护的LL-gp免疫小马的血清在体外增强EIAV复制的可能性更大；rgp90免疫血清的体外增强水平平均约为1.5，最大增强值约为2.0。虽然能够区分rgp90和LL-gp免疫产生的免疫血清，但体外增强试验未能可靠地与rgp90疫苗接种者中观察到的体内增强严重程度相关联。经历中度至无疾病体征的接种小马显示出的体外增强水平与病毒攻击后经历严重和致命疾病增强的小马相似。观察到的体外增强作用被证明依赖于血清免疫球蛋白，但不依赖于补体。这些研究表明，在EIAV系统中，体外ADE试验似乎是体内增强严重程度的相对不敏感指标，并且相对较低水平的体外ADE可能与体内病毒复制和疾病的严重至致命增强有关。这些观察结果表明，在包括HIV-1在内的其他慢病毒系统中观察到的相对较低水平的血清ADE可能对体内病毒复制和疾病产生比以前认识到的更深远的影响。
