Rare isolation of human-tropic recombinant porcine endogenous retroviruses PERV-A/C from Göttingen minipigs

Abstract

Background Porcine endogenous retroviruses (PERVs) can infect human cells and pose a risk for xenotransplantation when pig cells, tissues or organs are transplanted to human recipients. Xenotransplantation holds great promise to overcome the shortage of human donor organs after solving the problems of rejection, functionality and virus safety. We recently described the transmission of a human-tropic recombinant PERV-A/C, designated PERV-F, from peripheral blood mononuclear cells (PBMCs) of a Göttingen Minipig (GöMP) to human 293 cells (Krüger et al., in Viruses 12(1):38, 2019). The goal of this study was to characterize PERV-F in more detail and to analyze the probability of virus isolation from other animals. Methods The recombination site in the envelope (env) gene, the long terminal repeats (LTR), the proteins and the morphology of the recombinant PERV-F were characterized by polymerase chain reaction (PCR), sequencing, Western blot analysis, immunofluorescence, and transmissible electron microscopy. Mitogen-stimulated PBMCs from 47 additional pigs, including 17 new GöMP, were co-cultured with highly susceptible human 293 T cells, and the PERV-A/C prevalence and PERV transmission was analyzed by PCR. Results PERV-F, isolated from a GöMP, is an infectious human-tropic PERV-A/C virus with a novel type of recombination in the env gene. The length of the LTR of PERV-F increased after passaging on human cells. In a few minipigs, but not in German landrace pigs, PERV-A/C were found. There was no transmission of human-tropic PERV-A/C from additional 47 pigs, including 17 GöMP, to human cells. Conclusion These data show that human-tropic recombinant PERV-A/C proviruses can only be found in a very small number of minipigs, but not in other pigs, and that their isolation as infectious virus able to replicate on human cells is an extremely rare event, even when using highly susceptible 293 cells.

Early testing of porcine organ xenotransplantation products in humans: Microbial safety as illustrated for porcine cytomegalovirus

“…Although PERV‐C infects only pig cells but not human cells, its presence allows recombination between PERV‐C and PERV‐A, resulting in high titer PERV‐A/C recombinants 3 . However, such a recombination is a rare event in vivo 4 . The item of PERV risk was not addressed in the exploratory studies, and will not be discussed in this manuscript.…”

First virological and pathological study of Göttingen Minipigs with Dippity Pig Syndrome (DPS)

“…This is also new since in previous investigations PERV-A/C was never found in GöMPs from the Ellegaard Göttingen Minipigs A/S facility [28]. PERV-A/C was however found in two cases of GöMPs from the facility of the Göttingen University, were the animals were developed in the past [27, 47]. In one case the newly isolated recombinant PERV-A/C was able to infect human cells [27, 47].…”

“…PERV-A/C was however found in two cases of GöMPs from the facility of the Göttingen University, were the animals were developed in the past [27, 47]. In one case the newly isolated recombinant PERV-A/C was able to infect human cells [27, 47]. Whether the recombination and the wide distribution of PERV-A/C in minipig #342036 is associated with the DPS features remains unclear.…”

“…Selection of the porcine viruses to be tested for Sensitive detection methods have been developed for use in the virological screening of genetically modified donor pigs generated for xenotransplantation as well as screening of the corresponding nonhuman primate transplant recipients [46]. These methods were also used to screen for viruses in GöMPs as these may serve as donor animals for islet cell transplantation into human diabetic recipients [23][24][25][26][27][28][29]47]. Other pig breeds such as the Aachen minipigs [48,49], the Mini-LEWE minipigs [32] and Greek pigs with erythema multiforme [16] were analyzed using these methods.…”

“…12/39 animals (30%) were PCMV/PRV-positive in the first facility, none of ten animals in the second facility. PLHV-3 was found in two of 11 animals from the Göttingen University [47] (Table 5).…”