Cervantes Diana T, Ball Judith M, Edwards John, Payne Susan
Texas Department of State Health Services, HSR 2/3 1301 S. Bowen Rd., Ste 200, Arlington, TX, 76013, USA.
Texas A&M University, College Station, TX, USA.
Virus Genes. 2016 Feb;52(1):71-80. doi: 10.1007/s11262-015-1280-z. Epub 2016 Jan 6.
Equine infectious anemia virus (EIAV) causes lifelong infections ranging from acutely fatal, to chronic, to asymptomatic. Within infected animals, EIAV is found as a quasispecies. Many experimental studies on EIAV, carried out in the U.S. over the past 70 years, have used either the highly virulent Wyoming (EIAVWYO) field strain or various derivatives of that strain. These infections have provided insights into the variety of genetic changes that accumulate in the env gene and LTR in experimentally infected horses. In the current study, we obtained EIAV sequences from blood samples collected from naturally infected Texas horses between 2000 and 2002. We found surface (SU) and long terminal repeat (LTR) sequences clearly related to EIAVWYO and its cell culture-adapted derivatives. Some blood samples yielded SU or LTR sequences belonging to 2 discrete clusters. In these cases, SU and LTR variation between animals was no greater than sequence variation within animals. In contrast, a portion of integrase (IN) was more homogeneous within animals than between animals. These results suggest that specific selective pressures are applied to SU and LTR sequences, potentially driving generation of two distinct sequence clusters within a horse. We speculate that viruses in one cluster may be more highly expressed and easily transmitted while those in the second cluster support long-term inapparent infection. The presence of homogeneous IN sequences within a horse supports the hypothesis that SU and LTR sequences diverged after the initial infection.
马传染性贫血病毒（EIAV）可引发终生感染，感染程度从急性致命到慢性再到无症状不等。在受感染动物体内，EIAV以准种形式存在。过去70年在美国进行的许多关于EIAV的实验研究，要么使用高毒力的怀俄明州（EIAVWYO）野外毒株，要么使用该毒株的各种衍生物。这些感染为深入了解实验感染马匹中env基因和长末端重复序列（LTR）中积累的各种基因变化提供了线索。在本研究中，我们从2000年至2002年采集的自然感染得克萨斯州马匹的血液样本中获得了EIAV序列。我们发现表面（SU）和长末端重复序列（LTR）与EIAVWYO及其细胞培养适应衍生物明显相关。一些血液样本产生了属于2个离散簇的SU或LTR序列。在这些情况下，动物之间的SU和LTR变异不大于动物体内的序列变异。相比之下，整合酶（IN）的一部分在动物体内比在动物之间更具同质性。这些结果表明，特定的选择压力作用于SU和LTR序列，可能促使在一匹马体内产生两个不同的序列簇。我们推测，一个簇中的病毒可能表达水平更高且易于传播，而第二个簇中的病毒则支持长期隐性感染。一匹马体内存在同质性IN序列支持了SU和LTR序列在初次感染后发生分歧的假设。
