Porcine endogenous retroviruses (PERVs) represent a risk for xenotransplantation using pig cells or organs since they are integrated in the genome of all pigs and infect human cells
in vitro
. ...Recombinants between PERV-A and PERV-C have been described in pigs
in vivo
and found
de novo
integrated in the genome of somatic cells, but not in the germ line. To study whether PERV-A/C can infect and have a pathogenic effect in normal pigs, German landrace pigs were inoculated with high-titre PERV-A/C. No provirus integration was found in blood cells or in various tissues, and no antibody production was observed, indicating the absence of infection.
Robert Koch-Institut, Nordufer 20, D-13353 Berlin, Germany 1
Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, D-63225 Langen, Germany 2
Author for correspondence: Joachim Denner at Robert ...Koch-Institut. Fax +49 30 4547 2801. e-mail dennerj{at}rki.de
Using transgenic pigs as the source of cells or organs for xenotransplantation is associated with the risk of porcine endogenous retrovirus (PERV) transmission. Multiple proviruses are integrated into the genome of all pigs, and virus particles, some of which are able to infect human cells, are released from normal pig cells. In order to evaluate the potential risk posed by the transmission of PERVs, in vitro infection studies were performed as a basis for small animal as well as non-human primate models. In vitro infectivity was demonstrated for permanent cell lines and primary cells from a wide range of species. Productive infection was shown using reverse transcriptase (RT) assays and RTPCR for mink, feline and human kidney cell lines, primary rhesus peripheral blood mononuclear cells (PBMCs), and baboon spleen cells and PBMCs as well as for different human lymphoid and monocyte cell lines and PBMCs. In an attempt to establish a small animal model, naive guinea pigs, non-immunosuppressed rats, rats immunosuppressed by cyclosporin-A and immunosuppressed rats treated with cobra venom factor were inoculated with PERVs produced from porcine kidney PK-15 cells, infected human 293 kidney cells and mitogen-stimulated porcine PBMCs. Animals were also inoculated with PERV-producing PK-15 and 293 cells. No antibodies against PERV and no provirus integration were observed in any of the treated animals. This suggests that productive infection of these animals did not occur in this experimental setting.
: The objective of this study was to evaluate the feasibility and safety of a hybrid liver support system with extracorporeal plasma separation and bioreactor perfusion in patients with acute liver ...failure (ALF) who had already fulfilled the criteria for high urgency liver transplantation (LTx). Eight patients (one male, seven female) were treated in terms of bridging to transplantation. The mean age was 36.5 yr (range 20 to 58). Etiology of liver failure was drug‐related in two patients, hepatitis B infection in three patients, and unknown for three patients. The bioreactors were charged with primary liver cells from specific pathogen‐free pigs. Cell viability varied between 91 and 98%. Continuous liver support treatment over a period of 8 to 46 h (mean 27.3 h) was safely performed and well‐tolerated by all patients. No complications associated with the therapy were observed during the follow‐up period. Thrombocytopenia was considered to be an effect of the plasma separation. Subsequently, all patients were transplanted successfully and were observed over at least 3 yr with an organ and patient survival rate of 100%. Screening of patient's sera for antibodies specific for porcine endogenous retroviruses (PERVs) showed no reactivity – either prior to application of the system, or after extracorporeal treatment. The results encourage us to continue the development of the technology, and further studies appear to be justified. The bioreactor technology has been integrated into a modular extracorporeal liver support (MELS) system, combining biologic liver support with artificial detoxification technology.
Research-Practice Partnerships (RPPs) in education have been gaining increasing currency and support since well before the advent of COVID-19. This article reflects on what the pandemic experience ...has meant for some RPPs so far, and imagines what other RPPs might look like in the near future. The authors share a collection of fifteen think-pieces written by individuals working in or around, or funding RPPs during the COVID crisis. These contributions include reflections on how the pandemic affected existing RPPs and how teams responded to the disruptions, how the larger context in which RPPs operate matters, as well as how RPPs can help us build a more just and united society. The authors identify lessons to be drawn from across these think-pieces and implications for the field, and close with a call for action about learning scientists’ possibilities for belonging to RPPs. Through a somewhat unconventional form of scholarship, this article intends to spark and enrich conversations about tensions and choices facing RPPs and learning sciences scholarship broadly in the coming years.
Specific, effective and rapid neutralization assays are crucial for the development of an HIV vaccine based on the stimulation of neutralizing antibodies and the development of such an assay for the ...human immunodeficiency virus-2 (HIV-2) is described. Virus neutralization was measured as the reduction of provirus integration using a duplex real-time PCR with high efficiency (99.4%). This PCR uses primers and a probe specific for the proviral LTR. Amplification and quantitative analysis of the cellular GAPDH gene was carried out in parallel to control for toxic or growth-inhibitory components in the sera. The neutralization assay was used to screen sera from 23 HIV-2 infected patients. 21 sera were able to neutralize HIV-2
60415K, 20 sera neutralized HIV-2
7312A and 7 sera cross-neutralized HIV-1 IIIB. In contrast, when 14 of these sera were tested in parallel with a conventional neutralization assay based on a p27Gag capture ELISA, only one was found to neutralize HIV-2
60415K and 11 to neutralize HIV-2
7312A compared with 12 and 13 sera respectively using the PCR-based assay.
The human endogenous retrovirus K family (HERV-K) comprises 30 to 50 closely related proviruses, most of which are defective. In contrast to all other human endogenous retroviruses, some HERV-K ...proviruses have maintained open reading frames for all viral proteins. In addition to the structural proteins Gag and Env and the reverse transcriptase, two regulatory proteins (Rec and Np9) have been described. Malignant melanoma has the highest mortality among skin cancers and is particularly aggressive. To study the expression of HERV-K, a set of seven primers was developed that allows discrimination between full-length and spliced mRNA and mRNA from deleted and undeleted proviruses. Expression of full-length mRNA from deleted and undeleted proviruses was detected in all human cells investigated. Expression of spliced env and rec was detected in a teratocarcinoma cell line, in 45% of the metastatic melanoma biopsies, and in 44% of the melanoma cell lines. In normal neonatal melanocytes, spliced rec was detected but not spliced env. Viral proteins were shown to be expressed in primary melanomas, metastases, and melanoma cell lines by immunohistochemistry, immunofluorescence, and Western blot analyses using specific antisera. For the first time, antibodies against HERV-K were found in melanoma patients. Melanomas are, in addition to teratocarcinomas and human breast cancer, the third tumor type with enhanced expression of HERV-K.
Retroviruses induce in the infected host an immunosuppression the severity of which depends on the viral load. A pronounced immunosuppression is induced by human and simian immunodeficiency viruses ...(HIV and SIV) ultimately leading to AIDS. It is very likely that HIV originated by trans‐species transmission from primates. In contrast, SlVs are not pathogenic for their natural hosts probably as the result of virus‐host coevolution We have shown that a retroviral protein, the transmembrane envelope protein, may play an important role in retrovirus‐induced immunosuppression and that all retroviruses share an evolutionarily highly conserved domain in this protein. We demonstrate that synthetic peptides corresponding to this domain of different retroviruses, including HlV, the baboon endogenous virus (BaEV), and different porcine endogenous retroviruses (PERVs), are immunosuppressive. We provide evidence that BaEV and different PERVs, including those able to grow in human cells, are immunosuppressive for lymphocytes of different species including human. This implies that xenotransplantation may result in a trans‐species transmission of endogenous retroviruses derived from the donor animal. In analogy to HIV and SIV high‐titer virus replication may cause an AlDS‐like disease in the immunosuppressed human transplant recipient. Two additional points have to be considered: First, human anti‐complement proteins produced by transgenic animals will also protect the virus and, second, the virus may be transmitted to other humans and thus increase its pathogenic potential.
Porcine endogenous retroviruses (PERVs) are considered a special risk for xenotransplantation because they are an integral part of the porcine genome and are able to infect cells of numerous species ...including humans in vitro. Among these cells, the mink lung epithelial cell line Mv1Lu could be productively infected with PERV. Provirus integration was detected by PCR, expression of viral proteins was shown by immunostaining and reverse transcriptase was detected in cell supernatants. PERV produced from mink cells could infect both, uninfected mink Mv1Lu cells and uninfected human 293 cells, with considerably higher virus production by human cells. Typical type C retroviruses were observed in PERV-infected mink cells using electron microscopy together with numerous multivesicular body (MVB)-like structures containing small virus-like particles, not present in uninfected mink cells. These MVBs could be stained with PERV-specific serum. In an attempt to establish a small animal model, PERV grown on mink cells was inoculated into adult and newborn American minks. Neither antibody production against PERV nor integration of viral DNA or production of viral proteins in tissues of different organs could be detected 12 weeks post virus inoculation, indicating that PERV infection had not occurred.
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