Activation of Cytomegalovirus in Pig-to-Primate Organ Xenotransplantation

Abstract

Xenotransplantation of porcine organs carries the risk of reactivation of latent virus in donor and recipient tissues as well as transmission of viruses between species. We have investigated the activation of baboon cytomegalovirus (BCMV) and porcine CMV (PCMV) in a pig-to-primate model of xenotransplantation. Tissues originating from a series of six swine-to-baboon composite thymokidney xenotransplants were investigated. Four immunosuppressed baboons died (survival range, 7 to 27 days) with the graft in situ. Increases in BCMV DNA copy numbers occurred in three (75%) of these baboons and was thought to be responsible for pneumonitis and the death of one animal. In two baboons, disseminated intravascular coagulation was successfully treated by graftectomy and discontinuation of immunosuppression. PCMV was upregulated in five of six xenografts (83%). PCMV infection was associated with ureteric necrosis in one xenograft. Although significantly increased in native tissues, low levels of BCMV and PCMV were also detected in tissues other than that of the native viral host species. The cross-species presence of CMV did not appear to cause clinical or histological signs of invasive disease. Thus, viral infections with clinical disease were restricted to tissues of the native species of each virus. Intensive immune suppression currently required for xenotransplantation results in a significant risk of reactivation of latent infections by BCMV and PCMV. It is not yet known whether viral DNA detected across species lines represents cellular microchimerism, ongoing viral infection, or uptake of free virus. The observation of graft injury by PCMV demonstrates that CMV will be an important pathogen in immunosuppressed xenograft recipients. Strategies must be developed to exclude CMV from porcine organ donors.

Absence of Replication of Porcine Endogenous Retrovirus and Porcine Lymphotropic Herpesvirus Type 1 with Prolonged Pig Cell Microchimerism after Pig-to-Baboon Xenotransplantation

“…However, concerns persist regarding the potential risk of interspecies transmission of infectious pathogens with xenografts when clinical trials are initiated (13). Porcine cytomegalovirus (PCMV) and porcine lymphotropic herpesvirus (PLHV) are pathogens of swine that undergo accelerated viral replication and cause clinical syndromes in immunosuppressed xenograft recipients (3,11,15,28,29,31). PCMV is associated with consumptive coagulopathy in baboons after porcine xenotransplantation, and PLHV, a gamma herpesvirus, has been associated with a form of posttransplant lymphoma in immunosuppressed swine after allogeneic hematopoietic stem cell or splenic transplantation (4,10,14,17,28,31).…”

“…Porcine cytomegalovirus (PCMV) and porcine lymphotropic herpesvirus (PLHV) are pathogens of swine that undergo accelerated viral replication and cause clinical syndromes in immunosuppressed xenograft recipients (3,11,15,28,29,31). PCMV is associated with consumptive coagulopathy in baboons after porcine xenotransplantation, and PLHV, a gamma herpesvirus, has been associated with a form of posttransplant lymphoma in immunosuppressed swine after allogeneic hematopoietic stem cell or splenic transplantation (4,10,14,17,28,31). Porcine endogenous retroviruses (PERV) are members of a ubiquitous family of proviral elements of swine, which are capable of replicating in human cells, and thus carry the theoretical risk of transmission to humans in the setting of xenotransplantation (12,36).…”

“…The TaqMan PCR assay protocol described previously was used with the following primers and probes: BCMV forward primer 5Ј-GTTTAGGGAACCGC CATTCTG-3Ј and reverse primer 5Ј-GTATCCGCGTTCCAATGCA-3Ј (28). The BCMV probe was FAM-TCCAGCCTCCATAGCCGGGAAGG-TAMRA (28). The PCMV primers were forward primer 5Ј-GTTCTGGGATTCCGAGG TTG-3Ј and reverse primer 5Ј-ACTTCGTCGCAGCTCATCTGA-3Ј (28).…”

“…The PCMV primers were forward primer 5Ј-GTTCTGGGATTCCGAGG TTG-3Ј and reverse primer 5Ј-ACTTCGTCGCAGCTCATCTGA-3Ј (28). The PCMV probe was FAM-CAGGGCGGCGGTCGAGCTC-TAMRA (28).…”

Mouse retrovirus mediates porcine endogenous retrovirus transmission into human cells in long-term human-porcine chimeric mice

“…The dynamic range of the assay is quantitative between 6.6 million and 66 copies per sample. Pig MHC class I gene primers and probe were developed as internal controls for porcine cellular DNA (37,38). Primers and probe were derived from the pig MHC gene and are as follows: MHC sense, 5′-GCCCTGGGCTTCTACCCTAA-3′; MHC antisense, 5′-TCTCAGGGT-GAGTGGCTCCT-3′; probe, 5′-6FAM-CCAGGACCAGAGCCAGGACATG-GAGCTCGT-TAMRA-3'.…”