Tönjes Ralf R, Niebert Marcus
Paul-Ehrlich-Institut, D-63225 Langen, Germany.
J Virol. 2003 Nov;77(22):12363-8. doi: 10.1128/jvi.77.22.12363-12368.2003.
Porcine endogenous retroviruses (PERV) are discussed as putative infectious agents in xenotransplantation. PERV classes A, B, and C harbor different envelope proteins. Two different types of long terminal repeat (LTR) structures exist, of which both are present only in PERV-A. One type of LTR contains a distinct repeat structure in U3, while the other is repeatless, conferring a lower level of transcriptional activity. Since the different LTR structures are distributed unequally among the proviruses and, apparently, PERV is the only virus harboring two different LTR structures, we were interested in determining which LTR is the ancestor. Replication-competent viruses can still be found today, suggesting an evolutionary recent origin. Our studies revealed that the age of PERV is at most 7.6 x 10(6) years, whereas the repeatless LTR type evolved approximately 3.4 x 10(6) years ago, being the phylogenetically younger structure. The age determined for PERV correlates with the time of separation between pigs (Suidae, Sus scrofa) and their closest relatives, American-born peccaries (Tayassuidae, Pecari tajacu), 7.4 x 10(6) years ago.
猪内源性逆转录病毒(PERV)被认为是异种移植中潜在的感染因子。PERV的A、B和C类具有不同的包膜蛋白。存在两种不同类型的长末端重复序列(LTR)结构,且这两种结构仅存在于PERV-A中。一种LTR在U3中含有独特的重复结构,而另一种则没有重复序列,转录活性较低。由于不同的LTR结构在原病毒中分布不均,而且显然PERV是唯一具有两种不同LTR结构的病毒,我们有兴趣确定哪种LTR是祖先型。如今仍能发现具有复制能力的病毒,这表明其起源相对较近。我们的研究表明,PERV的存在时间至多为7.6×10⁶年,而无重复序列的LTR类型大约在3.4×10⁶年前进化而来,是系统发育上较年轻的结构。确定的PERV存在时间与猪(猪科,野猪)与其近亲美洲野猪(西猯科,草原西猯)在7.4×10⁶年前的分化时间相关。