Degradation Effect of Diepoxide Fixation on Porcine Endogenous Retrovirus DNA in Heart Valves: Molecular Aspects

Screening pigs for xenotransplantation: expression of porcine endogenous retroviruses in transgenic pig skin

Pigs seem to be the answer to worldwide organ donor shortage. Porcine skin may also be applied as a dressing for severe burns. Genetic modifications of donor animals enable reduction of immune response, which prolongs xenograft survival as temporary biological dressing and allows achieving resistance against xenograft rejection. The risk posed by porcine endogenous retroviruses (PERVs) cannot be eliminated by breeding animals under specific-pathogen-free conditions and so all recipients of porcine graft will be exposed to PERVs. Therefore our study has been focused on the assessment of PERV DNA and mRNA level in skin samples of transgenic pigs generated for xenotransplantation. Porcine skin fragments were obtained from 3- to 6-month-old non-transgenic and transgenic Polish Landrace pigs. Transgenic pigs were produced by pronuclear DNA microinjection and were developed to express the human α-galactosidase and the human α-1,2-fucosyltransferase gene. The copy numbers of PERV DNA and RNA were evaluated using real-time Q-PCR and QRT-PCR. Comparative analysis of all PERV subtypes revealed that PERV-A is the main subtype of PERVs in analyzed skin samples. There was no significantly different copy number of PERV-A, PERV-B and PERV-C between non-transgenic pigs, pigs with the human α-galactosidase and pigs expressing the human α-1,2-fucosyltransferase gene, except of PERV-C DNA. It brings the conclusion, that transgenesis process exerts no influence on PERVs transinfection. That is another step forward in the development of pig skin xenografts as burn wounds dressing.

Porcine endogenous retroviruses in xenotransplantation--molecular aspects

In the context of the shortage of organs and other tissues for use in human transplantation, xenotransplantation procedures with material taken from pigs have come under increased consideration. However, there are unclear consequences of the potential transmission of porcine pathogens to humans. Of particular concern are porcine endogenous retroviruses (PERVs). Three subtypes of PERV have been identified, of which PERV-A and PERV-B have the ability to infect human cells in vitro. The PERV-C subtype does not show this ability but recombinant PERV-A/C forms have demonstrated infectivity in human cells. In view of the risk presented by these observations, the International Xenotransplantation Association recently indicated the existence of four strategies to prevent transmission of PERVs. This article focuses on the molecular aspects of PERV infection in xenotransplantation and reviews the techniques available for the detection of PERV DNA, RNA, reverse transcriptase activity and proteins, and anti-PERV antibodies to enable carrying out these recommendations. These methods could be used to evaluate the risk of PERV transmission in human recipients, enhance the effectiveness and reliability of monitoring procedures, and stimulate discussion on the development of improved, more sensitive methods for the detection of PERVs in the future.

Quantitative analysis of porcine endogenous retroviruses in different organs of transgenic pigs generated for xenotransplantation

The pig appears to be the most promising animal donor of organs for use in human recipients. Among several types of pathogens found in pigs, one of the greatest problems is presented by porcine endogenous retroviruses (PERVs). Screening of the source pig herd for PERVs should include analysis of both PERV DNA and RNA. Therefore, the present study focuses on quantitative analysis of PERVs in different organs such as the skin, heart, muscle, and liver and blood of transgenic pigs generated for xenotransplantation. Transgenic pigs were developed to express the human α-galactosidase, the human α-1,2-fucosyltransferase gene, or both genetic modifications of the genome (Lipinski et al., Medycyna Wet 66:316-322, 2010; Lipinski et al., Ann Anim Sci 12:349-356, 2012; Wieczorek et al., Medycyna Wet 67:462-466, 2011). The copy numbers of PERV DNA and RNA were evaluated using real-time Q-PCR and QRT-PCR, respectively. Comparative analysis of all PERV subtypes revealed the following relationships: PERV A > PERV B > PERV C. PERV A and B were found in all samples, whereas PERV C was detected in 47 % of the tested animals. The lowest level of PERV DNA was shown in the muscles for PERV A and B and in blood samples for PERV C. The lowest level of PERV A RNA was found in the skin, whereas those of PERV B and C RNA were found in liver specimens. Quantitative analysis revealed differences in the copy number of PERV subtypes between various organs of transgenic pigs generated for xenotransplantation. Our data support the idea that careful pig selection for organ donation with low PERV copy number may limit the risk of retrovirus transmission to the human recipients.

Preparation of immunogen-reduced and biocompatible extracellular matrices from porcine liver

Decellularized biologic matrices are plausible biomedical materials for the bioengineering in liver transplantation. However, one of the concerns for safe medical application is the lack of objective assessment of the immunogen within the materials and the in vivo immune responses to the matrices. The purpose of this study was the production of immunogen-reduced and biocompatible matrices from porcine liver. In the present study, 0.1% SDS solution was effective for removing DNA fragments and sequences encoding possible immunogenic and viral antigens within the matrices. The PCR analysis showed that galactose-α-1,3 galactose β-1,4-N-acetylglucosamine (1,3 gal), swine leukocyte antigen (SLA), and porcine endogenous retrovirus (PERV) were completely removed in the matrices. Collagen and glycosaminoglycans (GAGs) were preserved over 63%-71%, respectively, compared to those of native liver. The implanted decellularized tissues showed minimal host responses and naturally degraded within 10 weeks. In this study, we produced immunogen-reduced and biocompatible extracellular matrices from porcine liver. Although future investigations would be required to determine the mechanism of the host reaction, this study could provide useful information of porcine liver-derived biologic matrices for liver researches.