Porcine Endogenous Retrovirus (PERV) and its Transmission Characteristics: A Study of the New Zealand Designated Pathogen-Free Herd

Abstract

Previously a strategy for monitoring of pigs intended for cell transplantation was developed and successfully applied to several representative herds in New Zealand. A designated pathogen-free (DPF) herd has been chosen as a good candidate for xenotransplantation. This herd has previously tested free of infectious agents relevant to xenotransplantation and we present here an in depth study of porcine endogenous retrovirus (PERV) transmission. A panel of assays that describes the constraints for the transmission of PERV has been suggested. It includes a) infectivity test in coculture of DPF pig primary cells with both human and pig target cell lines; b) RT activity in supernatant of stimulated primary cells from DPF pigs; c) viral load in donor's blood plasma; d) PERV proviral copy number in DPF pig genome; e) PERV class C prevalence in the herd and its recombination potential.

Development of sensitive methods for detection of porcine endogenous retrovirus-C (PERV-C) in the genome of pigs

“…PERV-A/C were until now detected only in miniature pigs and in these animals only in certain organs, e.g., in the spleen, but not in other organs and never in the germ line ( , [Harrison et al, 2004] and [Dieckhoff et al, 2007]). PERV-A/C were also not found in the New Zealand designated pathogen-free herd (Garkavenko et al, 2008). However, there are new reports on PERV-A/C in commercially used pigs with an increased number in clinically affected animals (Pal et al, 2011).…”

Developing Xenostandards for Microbiological Safety: New Zealand Experience

“…To ensure the release of infectious PERV particles (if any), tested cells were mitogenically stimulated prior to co-culture with standard susceptible cell lines 293 (to elucidate xeno-tropic PERV) and St-Iowa (to elucidate eco-tropic PERV). Although mitogenic stimulation enhanced proliferation of all tested cells, no evidence of PERV transmission was detected in the infectivity test with both human and pig target cells using PBMC or islet cells isolated from the New Zealand SPF pigs Garkavenko, Wynyard, Nathu, Simond, et al, 2008). Thus it was concluded that the New Zealand SPF pigs could be classified as non-transmitters for PERV, possessing the "null" transmission phenotype.…”

“…Moreover, endogenous retroviruses behave like normal cellular genes in that they are inherited by the offspring and not acquired by infection. Accordingly PERV cannot be removed by conventional barrier methods instead requiring more elaborate strategies such as the selective breeding of pigs with favourable PERV genetic characteristics Garkavenko, Wynyard, Nathu, Simond, Muzina et al, 2008;Stoye et al, 1998), or the development of vaccines to protect against PERV transmission or the inhibition of PERV expression by RNA interference using PERV-specific short hairpin RNA (shRNA) and retroviral vectors [reviewed in (Denner, 2008)]. Like most retroviruses PERV has an element of unpredictability in regards to its transmission potential.…”

“…During the characterisation of the www.intechopen.com New Zealand SPF herd PERV viral load in donor blood plasma was measured by real-time PCR using a methodology similar to that described by Dieckhoff et al (2009). RT activity that would indicate retroviral activity and therefore the presence of retroviral particles was also measured in the blood of the donors using a C-Type RT kit Garkavenko, Wynyard, Nathu, Simond, et al, 2008). No evidence of PERV expression or RT activity in pig donors' blood plasma or from stimulated PBMC was found.…”

“…As discussed earlier, using the co-culture infectivity test with human HEK293 and swine St Iowa target cell lines, it was established that primary cells (PBMCs) from NZ donor pigs do not release either xeno-or ecotropic infective viruses Garkavenko, Wynyard, Nathu, Simond, et al, 2008). To support the lack of transmission from this herd, animals were tested for and found to lack the genomic presence of high titre recombinant PERV A/C.…”