Microbiological screening of wild-type and genetically engineered pigs and transplant recipients in pig to non-human primate xenotransplantation
Xenotransplantation using porcine cells, tissue or organs may be associated with transmission of various pathogens that can induce zoonosis. Highly specific and sensitive methods detecting porcine endogenous retroviruses (PERVs), hepatitis E virus (HEV), porcine cytomegalovirus (PCMV) were developed and used to screen (i) wild-type Göttingen Minipigs, a breed produced under specified pathogen-free (spf) conditions, (ii) wild-type Aachen Minipigs, a newly created pig breed in Germany, and (iii) pigs produced carrying various transgenic modifications to prevent transplant rejection were analysed. Moreover, some animals were tested for the presence of >49 other microorganisms, incl. porcine lymphotropic herpes viruses (PLHV). Human-tropic PERV-A and PERV-B were found in all pigs und PERV-C was detected in all tested Göttingen Minipigs and in more than 90% of the other pigs. Although PERV-C does not infect human cells, it may represent a special risk when it recombines with PERV-A, as high-titre PERV-A/C were able to infect human cells in vitro. The expression level of PERV in all examined animals, as analysed in a mitogen stimulation assay, was found to same low range as previously reported for German landrace pigs. HEV was found in 27% of the Göttingen Minipigs, the prevalence of the herpes viruses was below 10%. Immunological methods based on recombinant viral proteins were developed to screen for antibodies against PERV, HEV, PCMV and PLHV. Antibodies against HEV were found only in few animals, whereby in piglets they were of maternal origin. The presence of HEV in sera of three sows six days after parturition and in their offspring in a well characterised SPF facility suggests vertical transmission of the virus. In contrast to PERVs, which are integrated in the porcine genome, HEV and herpes viruses can be eliminated using Caesarean section and eventually antiviral treatment. Most importantly, when islet cells from non-transgenic and transgenic pigs expressing immunomodulatory molecules were transplanted into marmosets, no transmission of PERV, HEV, PCMV and PLHV was observed, although four out of 14 donor pigs were PCMV positive. No transmission of PERV, HEV, PCMV and PLHV was observed after hearts from triple transgenic pigs were transplanted into baboons. These data indicate that sensitive and reliable methods for the detection of pathogens are available and that screening of putative donor pigs of porcine xenotransplants is critical to ensure microbiological safety in clinical xenotransplantation. Supported by the German Research Foundation (DFG) Transregio Collaborative Research Centre 127.
Morozov, V. / Plotzki, E. / Heinrichs, G. / et al: Microbiological screening of wild-type and genetically engineered pigs and transplant recipients in pig to non-human primate xenotransplantation. 2015.
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