Degradation effect of diepoxide fixation on porcine endogenous retrovirus DNA in heart valves: molecular aspects.

PURPOSE: Xenotransplantations of porcine cells, tissues, and organs involve a risk of zoonotic viral infections in recipients, including by porcine endogenous retroviruses (PERVs), which are embedded the genome of all pigs. An appropriate preparation of porcine heart valves for transplantation can prevent retroviral infection. Therefore, the present study focuses on the effect of epoxy compounds and glutaraldehyde on the PERV presence in porcine heart valves prepared for clinical use. METHODS: Porcine aortic heart valves were fixed with ethylene glycol diglycidyl ether (EDGE) at 5 °C and 25 °C as well as with glutaraldehyde (GA) for 4 weeks. Salting out was used to isolate genomic DNA from native as well as EDGE- and GA-fixed fragments of valves every week. Quantification of PERV-A, PERV-B, and PERV-C DNA was performed by real-time quantitative polymerase chain reaction (QPCR). RESULTS: All subtypes of PERVs were detected in native porcine aortic heart valves. The reduction of the PERV-A, PERV-B, and PERV-C DNA copy numbers was observed in the heart valves which were EDGE-fixed at both temperatures, and in GA-fixed ones in the following weeks. After 7 and 14 days of EDGE cross-linking, significant differences between the investigated temperatures were found for the number of PERV-A and PERV-B copies. PERV DNA was completely degraded within the first week of EDGE fixation at 25 °C. CONCLUSIONS: EDGE fixation induces complete PERV genetic material degradation in porcine aortic heart valves. This suggests that epoxy compounds may be alternatively used in the preparation of bioprosthetic heart valves in future.

Frequent detection of viral nucleic acids in heart valve tissue.

Due to a paucity of published data concerning the prevalence of viral nucleic acid in homografts, we analyzed tissue from 30 donor hearts for the presence of viral genome sequences of enteroviruses, adenoviruses, human cytomegalovirus, and influenza virus using different PCR techniques. Viral DNA was amplified in 64 and 52% of the subvalvular myocardial tissue and non-coronary valve samples, respectively. These findings, compared with clinical history and histologic and serologic analysis, demonstrate the importance of viral safety measures in heart valve banking.

Virus safety of a porcine-derived medical device: evaluation of a viral inactivation method.

The goal of this study was to evaluate the efficacy of a virus-inactivating process for use during the preparation of porcine-derived extracellular matrix biomaterials for human clinical implantation. Porcine small intestine, the source material for the tissue-engineered, small intestinal submucosa (SIS) biomaterial, was evaluated. Relevant enveloped, non-enveloped, and model viruses representative of different virus families were included in the investigation: porcine parvovirus (PPV), porcine reovirus, murine leukemia retrovirus (LRV), and porcine pseudorabies (herpes) virus (PRV). Samples of small intestine were deliberately inoculated with approximately 1 x 10(7) plaque-forming units (PFU) of virus which were thereafter exposed to a 0.18% peracetic acid/4.8% aqueous ethanol mixture for time periods ranging from 5 minutes to 2 hours. Enveloped viruses were more easily inactivated than non-enveloped viruses, but material processed for 30 minutes or longer inactivated all of the viruses. D(10) values were calculated and used to extrapolate the extent of inactivation after 2 hours. Viral titers were reduced by more than 14.0 log(10) PPV, 21.0 log(10) reovirus, 40.0 log(10) PRV, and 27.0 log(10) LRV, meeting international standards for viral sterility. These results demonstrate that treatment of porcine small intestine with a peracetic acid/ethanol solution leads to a virus-free, non-crosslinked biomaterial safe for xenotransplantation into humans.

Heart valves from pigs and the porcine endogenous retrovirus: experimental and clinical data to assess the probability of porcine endogenous retrovirus infection in human subjects.

OBJECTIVE: Replacement of heart valves in human subjects has become a routine procedure in cardiac operations. We sought to investigate whether commercially available glutaraldehyde-fixed porcine heart valve prostheses cause porcine endogenous retrovirus infection in human subjects because recent studies revealed that human cells can be infected with porcine endogenous retrovirus. METHODS: Blood samples of 18 patients who underwent aortic or mitral valve replacement with porcine heart valves were collected 6 months to 3 years after operation and tested for porcine endogenous retrovirus by means of polymerase chain reaction and reverse transcriptase-polymerase chain reaction. In addition, we tried to trace porcine endogenous retrovirus in 3 commercially available, glutaraldehyde-fixed, porcine heart valves. RESULTS: Porcine endogenous retrovirus can be easily detected in native porcine heart valves and degrades completely within 1 week of fixation in glutaraldehyde. In all 3 commercially available porcine heart valves, no traces of porcine endogenous retrovirus were found. All blood samples showed negative test results for the porcine endogenous retrovirus genome. CONCLUSION: Our results indicate that glutaraldehyde fixation of porcine heart valves reliably prevents cross-species transmission of porcine endogenous retrovirus.

Xenotransplantation and the potential risk of xenogeneic transmission of porcine viruses.

The clinical success of allotransplantation and the shortage of donor organs have led to a proposal for the use of animal organs as alternative therapeutic materials for humans. In that regard, swine are preferable to non-human primates as a source of donor organs. While applications for clinical trials for xenotransplantation have not yet been received in Canada, several trials have already been authorized in the United States. A major concern, however, is the potential for xenogeneic transmission of viruses from animals to humans via organ, tissue, or cellular transplantation or via ex vivo exposure of humans to porcine biologic materials. Xenotransplantation allows viruses to bypass the normal immunological defense mechanisms of the recipient. Furthermore, the use of immunosuppressive drugs following transplantation may facilitate the xenogeneic transmission of zoonotic agents. Of porcine viruses, swine hepatitis E virus does not cause any clinical symptoms in the natural host but is a likely zoonotic agent that can infect humans and cause hepatitis. Porcine circovirus type 1 is prevalent in swine populations with no known association with clinical disease, while circovirus type 2 causes post-weaning multi-systemic wasting syndrome. Porcine endogenous retrovirus is integrated into the host chromosomes while porcine cytomegalovirus undergoes latent infection. Two additional porcine herpesviruses have recently been identified in swine and have been named porcine lymphotrophic herpesviruses. These herpesviruses can potentially become reactivated in human recipients after xenotransplantation. All in all, there are a number of viruses in swine that are of primary concern to screen and eliminate from xenotransplantation protocols. Epidemiology and the current knowledge on xenogeneic risk of these viruses are discussed.