No transmission of porcine endogenous retrovirus in an acute liver failure model treated by a novel hybrid bioartificial liver containing porcine hepatocytes

BACKGROUND： A novel hybrid bioartificial liver（HBAL） was constructed using an anionic resin adsorption column and a multi-layer flat-plate bioreactor containing porcine hepatocytes co-cultured with bone marrow mesenchymal stem cells（MSCs）. This study aimed to evaluate the microbiological safety of the HBAL by detecting the transmission of porcine endogenous retroviruses（PERVs） into canines with acute liver failure（ALF） undergoing HBAL.METHODS： Eight dogs with ALF received a 6-hour HBAL treatment on the first day after the modeling by D-galactosamine administration. The plasma in the HBAL and the whole blood in the dogs were collected for PERV detection at regular intervals until one year later when the dogs were sacrificed to retrieve the tissues of several organs for immunohistochemistry and Western blotting for the investigation of PERV capsid protein gag p30 in the tissue. Furthermore, HEK293 cells were incubated to determine the in vitro infectivity.RESULTS： PERV RNA and reverse transcriptase activity were observed in the plasma of circuit 3, suggesting that PERV particles released in circuit 3. No positive PERV RNA and reverse transcriptase activity were detected in other plasma. No HEK293 cells were infected by the plasma in vitro. In addition, all PERV-related analyses in peripheral blood mononuclear cells and tissues were negative.CONCLUSION： No transmission of PERVs into ALF canines suggested a reliable microbiological safety of HBAL based on porcine hepatocytes.

Genome-wide identification of endogenous retrovirus elements and their active transcription in mink genome

Mammalian endogenous retroviruses(ERVs)are ancient retroviruses that have been integrated into genomes.ERVs were believed to be inactive until the discovery of ERV transcription in the mouse genome.However,the transcription level and function of ERV elements in mammalian genomes are not well understood.In this study,we performed the first genome‐wide scanning of ERV loci in the American mink(Neogale vison)genome(NeoERV)followed by transcriptomic analysis to detect actively transcribed NeoERV elements.A total of 365,791 NeoERV loci were identified,and161,205(44%)of these loci were found to be actively transcribed based on transcriptomic data from three types of tissues(amygdala,trachea and lung).More than one third of the actively transcribed NeoERV loci were tissue‐specific.Furthermore,some of the active loci were associated with host gene transcription,and the level of NeoERV transcription was positively correlated with that of host genes,specifically when active loci were located in overlapped gene regions.An in‐depth analysis of the envelope protein coding env gene showed that,in general,its transcription level was higher than that of NeoERVs,which is believed to be associated with host immunity.

Human Endogenous Retroviruses as Biomedicine Markers

Human endogenous retroviruses(HERVs)were formed via ancient integration of exogenous retroviruses into the human genome and are considered to be viral“fossils”.The human genome is embedded with a considerable amount of HERVs,witnessing the long-term evolutionary history of the viruses and the host.Most HERVs have lost coding capability during selection but still function in terms of HERV-mediated regulation of host gene expression.In this review,we summarize the roles of HERV activation in response to viral infections and diseases,and emphasize the potential use of HERVs as biomedicine markers in the early diagnosis of diseases such as cancer,which provides a new perspective for the clinical application of HERVs.

Human Endogenous Retrovirus Type W Envelope from Multiple Sclerosis Demyelinating Lesions Shows Unique Solubility and Antigenic Characteristics

In multiple sclerosis(MS),human endogenous retrovirus W family(HERV-W)envelope protein,pHERV-W ENV,limits remyelination and induces microglia-mediated neurodegeneration.To better understand its role,we examined the soluble pHERV-W antigen from MS brain lesions detected by specific antibodies.Physico-chemical and antigenic characteristics confirmed differences between pHERV-W ENV and syncytin-1.pHERV-W ENV monomers and trimers remained associated with membranes,while hexamers self-assembled from monomers into a soluble macrostructure involving sulfatides in MS brain.Extracellular hexamers are stabilized by internal hydrophobic bonds and external hydrophilic moieties.HERV-W studies in MS also suggest that this diffusible antigen may correspond to a previously described highmolecular-weight neurotoxic factor secreted by MS B-cells and thus represents a major agonist in MS pathogenesis.Adapted methods are now needed to identify encoding HERV provirus(es)in affected cells DNA.The properties and origin of MS brain pHERV-W ENV soluble antigen will allow a better understanding of the role of HERVs in MS pathogenesis.The present results anyhow pave the way to an accurate detection of the different forms of pHERV-W ENV antigen with appropriate conditions that remained unseen until now.

Transcriptome Analyses Implicate Endogenous Retroviruses Involved in the Host Antiviral Immune System through the Interferon Pathway

Human endogenous retroviruses(HERVs) are the remains of ancient retroviruses that invaded our ancestors’ germline cell and were integrated into the genome. The expression of HERVs has always been a cause for concern because of its association with various cancers and diseases. However, few previous studies have focused on specific activation of HERVs by viral infections. Our previous study has shown that dengue virus type 2(DENV-2) infection induces the transcription of a large number of abnormal HERVs loci;therefore, the purpose of this study was to explore the relationship between exogenous viral infection and HERV activation further. In this study, we retrieved and reanalyzed published data on 21 transcriptomes of human cells infected with various viruses. We found that infection with different viruses could induce transcriptional activation of HERV loci. Through the comparative analysis of all viral datasets, we identified 43 key HERV loci that were up-regulated by DENV-2, influenza A virus, influenza B virus, Zika virus, measles virus, and West Nile virus infections. Furthermore, the neighboring genes of these HERVs were simultaneously up-regulated, and almost all such neighboring genes were interferon-stimulated genes(ISGs), which are enriched in the host’s antiviral immune response pathways. Our data supported the hypothesis that activation of HERVs, probably via an interferon-mediated mechanism, plays an important role in innate immunity against viral infections.

Ancient origin and complex evolution of porcine endogenous retroviruses

Porcine endogenous retroviruses(PERVs)are proviruses that have medical value in xenotransplantation.However,the evolutionary process leading to the generation of modern PERVs is not well understood.In this study,we in silico mined 14 pig genomes and other available 304 mammalian genomes,which led to the documentation of 185 full-length PERVs or PERV-like sequences.Notably,we found that lesser Egyptian jerboa(Jaculus jaculus),rock hyrax(Procavia capensis)and eight Muridae species all harbored ancestral PERV-like sequences,indicative of ancient cross-species transmission events from none-porcine species to pigs.We also revealed that 11 genomic rearrangement events were mediated via PERVs,during the process of porcine evolution.In conclusion,these new findings help us to understand the complex evolution of the modern PERVs.

Human Endogenous Retroviruses and Hematological Malignant Tumors

Human endogenous retrovirus(HERV)gene sequences are remnants of retroviruses that infected the ancestors of humans millions of years ago and were integrated into human chromosomes,accounting for approximately 8%-9%of the human genome.Most integrated HERVs have lost their coding capacity and remain silent due to frame shifts,mutations,and sequence deletions or insertions over the millions of years,but their expression is highly regulated by epigenetic and host defense mechanisms.However,there are still some HERV genes that have intact open reading frames due to recent integration into the human genome or positive selective pressure.The abnormal activation of HERVs may contribute to diseases or their pathology,such as malignant tumors,autoimmune diseases,and nervous system diseases.The occurrence and development of hematological malignant tumors(HMTs)is a complex process involving interactions of multiple genetic and environmental factors.The abnormal activation of HERVs may contribute to the pathology of HMTs via indirect mechanisms.In this review,we address the discovery of endogenous retroviruses in vertebrates,and the classification and genomic structure of HERVs.Among HERV family members,HERV-K is the latest type of HERV integrated into the human genome and it has the strongest transcriptional activity.We explore the currently known expression of HERV-K proto-oncogenes in HMTs and further address potential research and therapeutic approaches.However,much remains to be learned about not only the impact of HERVs on the occurrence of HMTs,but also the potential value of HERVs as diagnostic and therapeutic targets for HMTs.

Advances on genetic and genomic studies of ALV resistance

Avian leukosis(AL)is a general term for a variety of neoplastic diseases in avian caused by avian leukosis virus(ALV).No vaccine or drug is currently available for the disease.Therefore,the disease can result in severe economic losses in poultry flocks.Increasing the resistance of poultry to ALV may be one effective strategy.In this review,we provide an overview of the roles of genes associated with ALV infection in the poultry genome,including endogenous retroviruses,virus receptors,interferon-stimulated genes,and other immune-related genes.Furthermore,some methods and techniques that can improve ALV resistance in poultry are discussed.The objectives are willing to provide some valuable references for disease resistance breeding in poultry.

The diversity and evolution of retroviruses:Perspectives from viral“fossils”

Retroviruses exclusively infect vertebrates,causing a variety of diseases.The replication of retroviruses requires reverse transcription and integration into host genomes.When infecting germline cells,retroviruses become inherited vertically,forming endogenous retroviruses(ERVs).ERVs document past viral infections,providing molecular fossils for studying the evolutionary history of retroviruses.In this review,we summarize the recent advances in understanding the diversity and evolution of retroviruses from the perspectives of viral fossils,and discuss the effects of ERVs on the evolution of host biology.

Domesticated HERV-W env contributes to the activation of the small conductance Ca^(2+)-activated K^(+)type 2 channels via decreased 5-HT4 receptor in recent-onset schizophrenia

The human endogenous retroviruses type W family envelope(HERV-W env)gene is located on chromosome 7q21-22.Our previous studies show that HERV-W env is elevated in schizophrenia and HERV-W env can increase cal-cium influx.Additionally,the 5-HTergie system and particularly 5-hydroxytryptamine(5-HT)receptors play a prominent role in the pathogenesis and treatment of schizophrenia.5-hydroxytryptamine receptor 4(5-HT4R)agonist can block calcium channels.However,the underlying relationship between HERV-W env and 5-HT4R in the etiology of schizophrenia has not been revealed.Here,we used enzyme-linked immunosorbent assay to detect the concentration of HERV-W env and 5-HT4R in the plasma of patients with schizophrenia and we found that there were decreased levels of 5-HT4R and a negative correlation between 5-HT4R and HERV-W env in schizophrenia.Overexpression of HERV-W env decreased the transcription and protein levels of 5-HT4R but increased small conductance Ca^(2+)-activated K^(+)type 2 channels(SK2)expression levels.Further studies revealed that HERV-w env could interact with 5-HT4R.Additionally,luciferase assay showed that an essential region(-364 to-176 from the transcription start site)in the SK2 promoter was required for HERV-W env-induced SK2 expression.Importantly,5-HT4R participated in the regulation of SK2 expression and promoter activity.Electrophysiological recordings suggested that HERV-Wenv could increase SK2 channel currents and the increase of SK2 currents was inhibited by 5-HT4R.In condusion,HERV-W env could activate SK2 channels via decreased 5-HT4R,which might exhibit a novel mechanism for HERV-Wenv to influence neuronal activity in schizophrenia.