Minipigs play an important role in biomedical research and they have also been used as donor animals for preclinical xenotransplantations. Since zoonotic microorganisms including viruses can be transmitted when pig cells, tissues or organs are transplanted, virus safety is an important feature in xenotransplantation. Whereas most porcine viruses can be eliminated from pig herds by different strategies, this is not possible for porcine endogenous retroviruses (PERVs). PERVs are integrated in the genome of pigs and some of them release infectious particles able to infect human cells. Whereas PERV-A and PERV-B are present in all pigs and can infect cells from humans and other species, PERV-C is present in most, but not all pigs and infects only pig cells. Recombinant viruses between PERV-A and PERV-C have been found in some pigs; these recombinants infect human cells and are characterized by high replication rates. PERV-A/C recombinants have been found mainly in minipigs of different origin. The possible reasons of this high prevalence of PERV-A/C in minipigs, including inbreeding and higher numbers and expression of replication-competent PERV-C in these animals, are discussed in this review. Based on these data, it is highly recommended to use only pig donors in clinical xenotransplantation that are negative for PERV-C.

中文翻译：

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小型猪中重组猪内源性逆转录病毒 (PERV-A/Cs) 的高患病率：起源和存在综述

小型猪在生物医学研究中发挥着重要作用，它们也被用作临床前异种移植的供体动物。由于在移植猪细胞、组织或器官时可以传播包括病毒在内的人畜共患病微生物，因此病毒安全性是异种移植的重要特征。虽然可以通过不同的策略从猪群中消除大多数猪病毒，但对于猪内源性逆转录病毒 (PERV) 来说这是不可能的。PERV 整合在猪的基因组中，其中一些释放出能够感染人类细胞的感染性颗粒。虽然 PERV-A 和 PERV-B 存在于所有猪体内，并且可以感染人类和其他物种的细胞，但 PERV-C 存在于大多数猪体内，但并非所有猪体内都存在，并且只感染猪细胞。在一些猪身上发现了 PERV-A 和 PERV-C 之间的重组病毒；这些重组体感染人类细胞并具有高复制率的特点。PERV-A/C 重组体主要存在于不同来源的小型猪中。本综述讨论了小型猪中 PERV-A/C 高流行的可能原因，包括近亲繁殖和更高数量的复制能力 PERV-C 在这些动物中的表达。基于这些数据，强烈建议在临床异种移植中仅使用 PERV-C 阴性的猪供体。