The Impact of Human Mammary Tumor Virus (HMTV) on the Expression of Epidermal Growth Factor Receptor (EGFR) and Death-Domain Associated Protein (DAXX) in Breast Carcinoma Tissues.

The presence and characteristics of HMTV in Iraqi breast cancer women are still unknown. Furthermore, the identification of HMTV in human breast carcinoma tissue of patients differs by country, and the factors that influence it are still unknown. In many epithelial tumor types, the EGFR and its signaling pathways outcomes are necessary for the behavior of cells and regulating their proliferation, and it has been discovered that DAXX has strong carcinogenic characteristics and could be a new treatment target. This case-control retrospective study investigated the presence of HMTV in paraffin-embedded blocks (FFPT) of tumor samples from 60 Iraqi women patients diagnosed with primary breast cancer and 20 cases of benign tumors as a control group. HMTV env sequences were identified by Real-time PCR. EGFR and DAXX expression were immun0-detected by the immuno-histochemistry technique. HMTV sequences were detected in 15 (25%) samples of malignant breast tumors and 8 (40%) samples of benign breast tumors. There was no statistically significant association between the detection of env sequences of HMTV and age, grade, hormone receptors, EGFR, or DAXX expression compared to clinicopathological characteristics. However, statistically, the data showed a highly significant difference in the Expression of EGFR between study groups, age, and histological types (P=0.0001), and a significant negative association was observed between EGFR and both Her2 and TNBC. There was a statistically significant difference between DAXX (+) and DAXX (-) in study groups (P=0.002), and it was significantly associated with age and histological types of breast cancer (P=0.031 and 0.007, respectively). No significant association was found between DAXX and EGFR, grade, Her2. TNBC of breast cancer. The current study found HMTV env sequences in breast tumors of Iraqi women, suggesting that a larger sample size is needed to illustrate the potential causative role of HMTV in the development of human breast malignancy. Moreover, a negative association was found between HMTV and DAXX and EGFR Expression.

Characterizing the Pathogenicity and Immunogenicity of Simian Retrovirus Subtype 8 (SRV-8) Using SRV-8-Infected Cynomolgus Monkeys.

Simian retrovirus subtype 8 (SRV-8) infections have been reported in cynomolgus monkeys (Macaca fascicularis) in China and America, but its pathogenicity and immunogenicity are rarely reported. In this work, the SRV-8-infected monkeys were identified from the monkeys with anemia, weight loss, and diarrhea. To clarify the impact of SRV-8 infection on cynomolgus monkeys, infected monkeys were divided into five groups according to disease progression. Hematoxylin (HE) staining and viral loads analysis showed that SRV-8 mainly persisted in the intestine and spleen, causing tissue damage. Additionally, the dynamic variations of blood routine indexes, innate and adaptive immunity, and the transcriptomic changes in peripheral blood cells were analyzed during SRV-8 infection. Compared to uninfected animals, red blood cells, hemoglobin, and white blood cells were reduced in SRV-8-infected monkeys. The percentage of immune cell populations was changed after SRV-8 infection. Furthermore, the number of hematopoietic stem cells decreased significantly during the early stages of SRV-8 infection, and returned to normal levels after antibody-mediated viral clearance. Finally, global transcriptomic analysis in PBMCs from SRV-8-infected monkeys revealed distinct gene expression profiles across different disease stages. In summary, SRV-8 infection can cause severe pathogenicity and immune disturbance in cynomolgus monkeys, and it might be responsible for fatal virus-associated immunosuppressive syndrome.

The Role of a Betaretrovirus in Human Breast Cancer: Enveloping a Conundrum.

Most of the evidence that a human betaretrovirus (HBRV/HMTV) highly related to mouse mammary tumour virus (MMTV) has an etiological role in breast cancer has been summarized in a recent comprehensive Special Issue of "Viruses" entitled "Human Betaretrovirus (HBRV) and Related Diseases". Shortly after publication of this special issue, a detailed analysis of aligned env sequences was published and concluded that (i) MMTV and HBRV/HMTV cannot be distinguished on the basis of aligned env sequences and (ii) more sequence data covering the full-length env or HBRV/HMTV genomes from multiple isolates is needed. Although productive infection of human cells by MMTV (and presumably HBRV/HMTV) has been shown, it is imperative that the receptor(s) enabling HBRV/HMTV to infect human cells are defined. Moreover, there is currently no compelling data for common integration sites, in contrast to MMTV induced mammary tumorigenesis in mice, suggesting that other mechanisms of tumorigenesis are associated with HBRV/HMTV infection. These issues need to be resolved before a clear link between MMTV/HBRV/HMTV and human breast cancer can be concluded.

Life after Cleavage: The Story of a ß-Retroviral (MMTV) Signal Peptide-From Murine Lymphoma to Human Breast Cancer.

An increasing body of evidence in recent years supports an association of the betaretrovirus mouse mammary tumor virus (MMTV) with human breast cancer. This is an issue that still raises heated controversy. We have come to address this association using the signal peptide p14 of the MMTV envelope precursor protein as a key element of our strategy. In addition to its signal peptide function, p14 has some significant post endoplasmic reticulum (ER)-targeting characteristics: (1) it localizes to nucleoli where it binds key proteins (RPL5 and B23) involved (among other activities) in the regulation of nucleolar stress response, ribosome biogenesis and p53 stabilization; (2) p14 is a nuclear export factor; (3) it is expressed on the cell surface of infected cells, and as such, is amenable to, and successfully used, in preventive vaccination against experimental tumors that harbor MMTV; (4) the growth of such tumors is impaired in vivo using a combination of monoclonal anti-p14 antibodies or adoptive T-cell transfer treatments; (5) p14 is a phospho-protein endogenously phosphorylated by two different serine kinases. The phosphorylation status of the two sites determines whether p14 will function in an oncogenic or tumor-suppressing capacity; (6) transcriptional activation of genes (RPL5, ErbB4) correlates with the oncogenic potential of MMTV; (7) finally, polyclonal anti-p14 antibodies have been applied in immune histochemistry analyses of breast cancer cases using formalin fixed paraffin-embedded sections, supporting the associations of MMTV with the disease. Taken together, the above findings constitute a road map towards the diagnosis and possible prevention and treatment of MMTV-associated breast cancer.

Stealing genes and facing consequences.

The human genome contains a domesticated viral envelope gene with antiviral activity.

Evolution and antiviral activity of a human protein of retroviral origin.

Endogenous retroviruses are abundant components of mammalian genomes descended from ancient germline infections. In several mammals, the envelope proteins encoded by these elements protect against exogenous viruses, but this activity has not been documented with endogenously expressed envelopes in humans. We report that the human genome harbors a large pool of envelope-derived sequences with the potential to restrict retroviral infection. To test this, we characterized an envelope-derived protein, Suppressyn. We found that Suppressyn is expressed in human preimplantation embryos and developing placenta using its ancestral retroviral promoter. Cell culture assays showed that Suppressyn, and its hominoid orthologs, could restrict infection by extant mammalian type D retroviruses. Our data support a generalizable model of retroviral envelope co-option for host immunity and genome defense.

Linking Human Betaretrovirus with Autoimmunity and Liver Disease in Patients with Primary Biliary Cholangitis.

Primary biliary cholangitis (PBC) is an autoimmune liver disease characterized by the production of diagnostic antimitochondrial antibodies (AMA) reactive to the pyruvate dehydrogenase complex. A human betaretrovirus (HBRV) resembling mouse mammary tumor virus has been characterized in patients with PBC. However, linking the viral infection with the disease is not a straight-forward process because PBC is a complex multifactorial disease influenced by genetic, hormonal, autoimmune, environmental, and other factors. Currently, PBC is assumed to have an autoimmune etiology, but the evidence is lacking to support this conjecture. In this review, we describe different approaches connecting HBRV with PBC. Initially, we used co-cultivation of HBRV with biliary epithelial cells to trigger the PBC-specific phenotype with cell surface expression of cryptic mitochondrial autoantigens linked with antimitochondrial antibody expression. Subsequently, we have derived layers of proof to support the role of betaretrovirus infection in mouse models of autoimmune biliary disease with spontaneous AMA production and in patients with PBC. Using Hill's criteria, we provide an overview of how betaretrovirus infection may trigger autoimmunity and propagate biliary disease. Ultimately, the demonstration that disease can be cured with antiviral therapy may sway the argument toward an infectious disease etiology in an analogous fashion that was used to link H. pylori with peptic ulcer disease.

The Viral Origin of Human Breast Cancer: From the Mouse Mammary Tumor Virus (MMTV) to the Human Betaretrovirus (HBRV).

A Human Betaretrovirus (HBRV) has been identified in humans, dating as far back as about 4500 years ago, with a high probability of it being acquired by our species around 10,000 years ago, following a species jump from mice to humans. HBRV is the human homolog of the MMTV (mouse mammary tumor virus), which is the etiological agent of murine mammary tumors. The hypothesis of a HMTV (human mammary tumor virus) was proposed about 50 years ago, and has acquired a solid scientific basis during the last 30 years, with the demonstration of a robust link with breast cancer and with PBC, primary biliary cholangitis. This article summarizes most of what is known about MMTV/HMTV/HBRV since the discovery of MMTV at the beginning of last century, to make evident both the quantity and the quality of the research supporting the existence of HBRV and its pathogenic role. Here, it is sufficient to mention that scientific evidence includes that viral sequences have been identified in breast-cancer samples in a worldwide distribution, that the complete proviral genome has been cloned from breast cancer and patients with PBC, and that saliva contains HBRV, as a possible route of inter-human infection. Controversies that have arisen concerning results obtained from human tissues, many of them outdated by new scientific evidence, are critically discussed and confuted.

Expansion of a retrovirus lineage in the koala genome.

Retroviruses have left their legacy in host genomes over millions of years as endogenous retroviruses (ERVs), and their structure, diversity, and prevalence provide insights into the historical dynamics of retrovirus-host interactions. In bioinformatic analyses of koala (Phascolarctos cinereus) whole-genome sequences, we identify a recently expanded ERV lineage (phaCin-ß) that is related to the New World squirrel monkey retrovirus. This ERV expansion shares many parallels with the ongoing koala retrovirus (KoRV) invasion of the koala genome, including highly similar and mostly intact sequences, and polymorphic ERV loci in the sampled koala population. The recent phaCin-ß ERV colonization of the koala genome appears to predate the current KoRV invasion, but polymorphic ERVs and divergence comparisons between these two lineages predict a currently uncharacterized, possibly still extant, phaCin-ß retrovirus. The genomics approach to ERV-guided discovery of novel retroviruses in host species provides a strong incentive to search for phaCin-ß retroviruses in the Australasian fauna.

Isolation of a Human Betaretrovirus from Patients with Primary Biliary Cholangitis.

A human betaretrovirus (HBRV) has been linked with the autoimmune liver disease, primary biliary cholangitis (PBC), and various cancers, including breast cancer and lymphoma. HBRV is closely related to the mouse mammary tumor virus, and represents the only exogenous betaretrovirus characterized in humans to date. Evidence of infection in patients with PBC has been demonstrated through the identification of proviral integration sites in lymphoid tissue, the major reservoir of infection, as well as biliary epithelium, which is the site of the disease process. Accordingly, we tested the hypothesis that patients with PBC harbor a transmissible betaretrovirus by co-cultivation of PBC patients' lymph node homogenates with the HS578T breast cancer line. Because of the low level of HBRV replication, betaretrovirus producing cells were subcloned to optimize viral isolation and production. Evidence of infection was provided by electron microscopy, RT-PCR, in situ hybridization, cloning of the HBRV proviral genome and demonstration of more than 3400 integration sites. Further evidence of viral transmissibility was demonstrated by infection of biliary epithelial cells. While HBRV did not show a preference for integration proximal to specific genomic features, analyses of common insertion sites revealed evidence of integration proximal to cancer associated genes. These studies demonstrate the isolation of HBRV with features similar to mouse mammary tumor virus and confirm that patients with PBC display evidence of a transmissible viral infection.

Mouse Mammary Tumour Virus (MMTV) in Human Breast Cancer-The Value of Bradford Hill Criteria.

For many decades, the betaretrovirus, mouse mammary tumour virus (MMTV), has been a causal suspect for human breast cancer. In recent years, substantial new evidence has been developed. Based on this evidence, we hypothesise that MMTV has a causal role. We have used an extended version of the classic A. Bradford Hill causal criteria to assess the evidence. 1. Identification of MMTV in human breast cancers: The MMTV 9.9 kb genome in breast cancer cells has been identified. The MMTV genome in human breast cancer is up to 98% identical to MMTV in mice. 2. EPIDEMIOLOGY: The prevalence of MMTV positive human breast cancer is about 35 to 40% of breast cancers in Western countries and 15 to 20% in China and Japan. 3. Strength of the association between MMTV and human breast cancer: Consistency-MMTV env gene sequences are consistently five-fold higher in human breast cancer as compared to benign and normal breast controls. 4. Temporality (timing) of the association: MMTV has been identified in benign and normal breast tissues up to 10 years before the development of MMTV positive breast cancer in the same patient. 5. EXPOSURE: Exposure of humans to MMTV leads to development of MMTV positive human breast cancer. 6. Experimental evidence: MMTVs can infect human breast cells in culture; MMTV proteins are capable of malignantly transforming normal human breast epithelial cells; MMTV is a likely cause of biliary cirrhosis, which suggests a link between MMTV and the disease in humans. 7. Coherence-analogy: The life cycle and biology of MMTV in humans is almost the same as in experimental and feral mice. 8. MMTV Transmission: MMTV has been identified in human sputum and human milk. Cereals contaminated with mouse fecal material may transmit MMTV. These are potential means of transmission. 9. Biological plausibility: Retroviruses are the established cause of human cancers. Human T cell leukaemia virus type I (HTLV-1) causes adult T cell leukaemia, and human immunodeficiency virus infection (HIV) is associated with lymphoma and Kaposi sarcoma. 10. Oncogenic mechanisms: MMTV oncogenesis in humans probably differs from mice and may involve the enzyme APOBEC3B. CONCLUSION: In our view, the evidence is compelling that MMTV has a probable causal role in a subset of approximately 40% of human breast cancers.

Apples to Apples? A Comparison of Real-World Tolerability of Antiretrovirals in Patients with Human Immunodeficiency Virus Infection and Patients with Primary Biliary Cholangitis.

We previously characterized a human betaretrovirus and linked infection with the development of primary biliary cholangitis (PBC). There are in vitro and in vivo data demonstrating that antiretroviral therapy used to treat human immunodeficiency virus (HIV) can be repurposed to treat betaretroviruses. As such, PBC patients have been treated with nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs), alone and in combination with a boosted protease inhibitor or an integrase strand transfer inhibitor in case studies and clinical trials. However, a randomized controlled trial using combination antiretroviral therapy with lopinavir was terminated early because 70% of PBC patients discontinued therapy because of gastrointestinal side effects. In the open-label extension, patients tolerating combination therapy underwent a significant reduction in serum liver parameters, whereas those on NRTIs alone rebounded to baseline. Herein, we compare clinical experience in the experimental use of antiretroviral agents in patients with PBC with the broader experience of using these agents in people living with HIV infection. While the incidence of gastrointestinal side effects in the PBC population appears somewhat increased compared to those with HIV infection, the clinical improvement observed in patients with PBC suggests that further studies using the newer and better tolerated antiretroviral agents are warranted.

Betaretrovirus infections in dromedary camels in Saudi Arabia.

BACKGROUND: Retroviral infections have been reported in many species of animals, especially cattle, sheep and goats. However, there are no available reports about retrovirus infection in dromedary camels. Several dromedary camels showed visible tumor-like lesions on and around the nostrils as well as around the eyes. OBJECTIVES: Following are the objectives: to identify the causative agents of these identified tumours in dromedary camels and to perform molecular characterization of the detected strains of the causative agent. METHODS: We extracted the nucleic acids from some fresh lesions out of these animals, and then amplified some key retrovirus genes. We amplified several regions of the rotavirus genome using the PCR technique. The obtained sequences were assembled and the phylogenetic trees were conducted per each target retrovirus gene. RESULTS: Our results revealed a high degree of identity to some retroviruses of sheep. Phylogenetic analysis based on some retrovirus genes revealed that the causative agents of these lesions are closely related to sheep retroviruses, particularly the Jaagsiekte sheep Retrovirus (JSRV) and the ENTV. CONCLUSIONS: To the best of our knowledge, this is the first report of retrovirus infections in dromedary camels in the Arabian Peninsula. This highlights the possible species jump for the retrovirus from sheep and goats to the dromedary camels, which live in close proximity with these animals in many parts of the world, especially the Arabian Peninsula.

Detection and Characterisation of an Endogenous Betaretrovirus in Australian Wild Deer.

Endogenous retroviruses (ERVs) are the remnants of past retroviral infections that once invaded the host's germline and were vertically transmitted. ERV sequences have been reported in mammals, but their distribution and diversity in cervids are unclear. Using next-generation sequencing, we identified a nearly complete genome of an endogenous betaretrovirus in fallow deer (Dama dama). Further genomic analysis showed that this provirus, tentatively named cervid endogenous betaretrovirus 1 (CERV ß1), has typical betaretroviral genome features (gag-pro-pol-env) and the betaretrovirus-specific dUTPase domain. In addition, CERV ß1 pol sequences were detected by PCR in the six non-native deer species with wild populations in Australia. Phylogenetic analyses demonstrated that CERV ß1 sequences from subfamily Cervinae clustered as sister taxa to ERV-like sequences in species of subfamily Muntiacinae. These findings, therefore, suggest that CERV ß1 endogenisation occurred after the split of these two subfamilies (between 3.3 and 5 million years ago). Our results provide important insights into the evolution of betaretroviruses in cervids.

Domain Organization of Lentiviral and Betaretroviral Surface Envelope Glycoproteins Modeled with AlphaFold.

The surface envelope glycoproteins of nonprimate lentiviruses and betaretroviruses share sequence similarity with the inner proximal domain ß-sandwich of the human immunodeficiency virus type 1 (HIV-1) gp120 glycoprotein that faces the transmembrane glycoprotein as well as patterns of cysteine and glycosylation site distribution that points to a similar two-domain organization in at least some lentiviruses. Here, high-reliability models of the surface glycoproteins obtained with the AlphaFold algorithm are presented for the gp135 glycoprotein of the small ruminant caprine arthritis-encephalitis (CAEV) and visna lentiviruses and the betaretroviruses Jaagsiekte sheep retrovirus (JSRV), mouse mammary tumor virus (MMTV), and consensus human endogenous retrovirus type K (HERV-K). The models confirm and extend the inner domain structural conservation in these viruses and identify two outer domains with a putative receptor binding site in the CAEV and visna virus gp135. The location of that site is consistent with patterns of sequence conservation and glycosylation site distribution in gp135. In contrast, a single domain is modeled for the JSRV, MMTV, and HERV-K betaretrovirus envelope proteins that is highly conserved structurally in the proximal region and structurally diverse in apical regions likely to interact with cell receptors. The models presented here identify sites in small ruminant lentivirus and betaretrovirus envelope glycoproteins likely to be critical for virus entry and virus neutralization by antibodies and will facilitate their functional and structural characterization. IMPORTANCE Structural information on the surface envelope proteins of lentiviruses and related betaretroviruses is critical to understand mechanisms of virus-host interactions. However, experimental determination of these structures has been challenging, and only the structure of the human immunodeficiency virus type 1 gp120 has been determined. The advent of the AlphaFold artificial intelligence method for structure prediction allows high-quality modeling of the structures of small ruminant lentiviral and betaretroviral surface envelope proteins. The models are consistent with much of the previously described experimental data, show regions likely to interact with receptors, and identify domains that may be involved in mechanisms of antibody neutralization resistance in the small ruminant lentiviruses. The models will allow more precise design of mutants to further determine mechanisms of viral entry and immune evasion in this group of viruses and constructs for structural determination of these surface envelope proteins.

A novel Betaretrovirus discovered in cattle with neurological disease and encephalitis.

BACKGROUND: The majority of emerging infectious diseases in humans are of animal origin, and many of them are caused by neuropathogenic viruses. Many cases of neurological disease and encephalitis in livestock remain etiologically unresolved, posing a constant threat to animal and human health. Thus, continuous extension of our knowledge of the repertoire of viruses prone to infect the central nervous system (CNS) is vital for pathogen monitoring and the early detection of emerging viruses. Using high-throughput sequencing (HTS) and bioinformatics, we discovered a new retrovirus, bovine retrovirus CH15 (BoRV CH15), in the CNS of a cow with non-suppurative encephalitis. Phylogenetic analysis revealed the affiliation of BoRV CH15 to the genus Betaretrovirus. RESULTS: BoRV CH15 genomes were identified prospectively and retrospectively by PCR, RT-PCR, and HTS, with targeting of viral RNA and proviral DNA, in six additional diseased cows investigated over a period of > 20 years and of different geographical origins. The virus was not found in brain samples from healthy slaughtered control animals (n = 130). We determined the full-length proviral genomes from six of the seven investigated animals and, using in situ hybridization, identified viral RNA in the cytoplasm of cells morphologically compatible with neurons in diseased brains. CONCLUSIONS: Further screening of brain samples, virus isolation, and infection studies are needed to estimate the significance of these findings and the causative association of BoRV CH15 with neurological disease and encephalitis in cattle. However, with the full-length proviral sequences of BoRV CH15 genomes, we provide the basis for a molecular clone and further in vitro investigation.

Development of a SYBR Green-based real-time quantitative polymerase chain reaction assay to detect enzootic nasal tumor virus in goats.

Enzootic nasal adenocarcinoma is a contagious respiratory disease in goats that is caused by the enzootic nasal tumor virus 2 (ENTV-2). In order to increase the number of available detection methods for ENTV-2, we developed a SYBR Green real-time polymerase chain reaction (SGrPCR) assay that targets the gag gene of ENTV-2. The low limit of detection of the assay was 3.68 × 101 copies/µL, a hundredfold more sensitive than conventional PCR. The melt curve showed a single sharp melt peak at 83°C, which indicated that there was no non-specific amplification or primer dimer formation. The intra-assay and inter-assay coefficients of variation were 1.58% and 1.82%, respectively. There was no cross-reactivity with closely related goat viruses (i.e., orf virus, peste des petits ruminants virus, goatpox virus, foot-and-mouth disease virus) and endogenous retroviruses. In conclusion, the SGrPCR assay is specific for the gag gene of ENTV-2 and provides a rapid and sensitive approach for detecting ENTV-2 in clinical samples.

L'adénocarcinome nasal enzootique est une maladie respiratoire contagieuse chez les chèvres qui est causé par le virus de la tumeur nasale enzootique 2 (ENTV-2). Afin d'augmenter le nombre de méthodes de détection disponibles pour ENTV-2, nous avons développé un test de réaction en chaîne par polymérase en temps réel SYBR Green (SGrPCR) qui cible le gène gag de ENTV-2. La limite basse de détection du test était de 3,68 × 101 copies/µL, cent fois plus sensible que la PCR conventionnelle. La courbe de fusion montrait un seul pic de fusion net à 83 °C, ce qui indiquait qu'il n'y avait pas d'amplification non spécifique ou de formation de dimère d'amorce. Les coefficients de variation intra-essai et inter-essai étaient respectivement de 1,58 % et 1,82 %. Il n'y avait pas de réactivité croisée avec les virus caprins étroitement apparentés (c'est-à-dire le virus orf, le virus de la peste des petits ruminants, le virus de la variole caprine, le virus de la fièvre aphteuse) et les rétrovirus endogènes. En conclusion, le test SGrPCR est spécifique du gène gag de l'ENTV-2 et fournit une approche rapide et sensible pour la détection d'ENTV-2 dans des échantillons cliniques.(Traduit par Docteur Serge Messier).

Virus-derived variation in diverse human genomes.

Acquisition of genetic material from viruses by their hosts can generate inter-host structural genome variation. We developed computational tools enabling us to study virus-derived structural variants (SVs) in population-scale whole genome sequencing (WGS) datasets and applied them to 3,332 humans. Although SVs had already been cataloged in these subjects, we found previously-overlooked virus-derived SVs. We detected non-germline SVs derived from squirrel monkey retrovirus (SMRV), human immunodeficiency virus 1 (HIV-1), and human T lymphotropic virus (HTLV-1); these variants are attributable to infection of the sequenced lymphoblastoid cell lines (LCLs) or their progenitor cells and may impact gene expression results and the biosafety of experiments using these cells. In addition, we detected new heritable SVs derived from human herpesvirus 6 (HHV-6) and human endogenous retrovirus-K (HERV-K). We report the first solo-direct repeat (DR) HHV-6 likely to reflect DR rearrangement of a known full-length endogenous HHV-6. We used linkage disequilibrium between single nucleotide variants (SNVs) and variants in reads that align to HERV-K, which often cannot be mapped uniquely using conventional short-read sequencing analysis methods, to locate previously-unknown polymorphic HERV-K loci. Some of these loci are tightly linked to trait-associated SNVs, some are in complex genome regions inaccessible by prior methods, and some contain novel HERV-K haplotypes likely derived from gene conversion from an unknown source or introgression. These tools and results broaden our perspective on the coevolution between viruses and humans, including ongoing virus-to-human gene transfer contributing to genetic variation between humans.

Effect of Small Polyanions on In Vitro Assembly of Selected Members of Alpha-, Beta- and Gammaretroviruses.

The assembly of a hexameric lattice of retroviral immature particles requires the involvement of cell factors such as proteins and small molecules. A small, negatively charged polyanionic molecule, myo-inositol hexaphosphate (IP6), was identified to stimulate the assembly of immature particles of HIV-1 and other lentiviruses. Interestingly, cryo-electron tomography analysis of the immature particles of two lentiviruses, HIV-1 and equine infectious anemia virus (EIAV), revealed that the IP6 binding site is similar. Based on this amino acid conservation of the IP6 interacting site, it is presumed that the assembly of immature particles of all lentiviruses is stimulated by IP6. Although this specific region for IP6 binding may be unique for lentiviruses, it is plausible that other retroviral species also recruit some small polyanion to facilitate the assembly of their immature particles. To study whether the assembly of retroviruses other than lentiviruses can be stimulated by polyanionic molecules, we measured the effect of various polyanions on the assembly of immature virus-like particles of Rous sarcoma virus (RSV), a member of alpharetroviruses, Mason-Pfizer monkey virus (M-PMV) representative of betaretroviruses, and murine leukemia virus (MLV), a member of gammaretroviruses. RSV, M-PMV and MLV immature virus-like particles were assembled in vitro from truncated Gag molecules and the effect of selected polyanions, myo-inostol hexaphosphate, myo-inositol, glucose-1,6-bisphosphate, myo-inositol hexasulphate, and mellitic acid, on the particles assembly was quantified. Our results suggest that the assembly of immature particles of RSV and MLV was indeed stimulated by the presence of myo-inostol hexaphosphate and myo-inositol, respectively. In contrast, no effect on the assembly of M-PMV as a betaretrovirus member was observed.