{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,30]],"date-time":"2026-10-30T02:13:22Z","timestamp":1793326402349,"version":"4.5.0"},"reference-count":41,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2023,8,3]],"date-time":"2023-08-03T00:00:00Z","timestamp":1691020800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Eurostars-2 programme","award":["113556"],"award-info":[{"award-number":["113556"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Viruses"],"abstract":"<jats:p>Human endogenous retrovirus type W (HERV-W) is expressed in various cancers. We previously developed an adenovirus-vectored cancer vaccine targeting HERV-W by encoding an assembled HERV-W group-specific antigen sequence and the HERV-W envelope sequence Syncytin-1. Syncytin-1 is constitutively fusogenic and forms large multinucleated cell fusions when overexpressed. Consequently, immunising humans with a vaccine encoding Syncytin-1 can lead to the formation of extensive syncytia, which is undesirable and poses a potential safety issue. Here, we show experiments in cell lines that restoring an evolutionary lost cleavage site of the fusion inhibitory R-peptide of Syncytin-1 inhibit cell fusion. Interestingly, this modification of the HERV-W vaccine\u2019s fusogenicity increased the expression of the vaccine antigens in vitro. It also enhanced Syncytin-1-specific antibody responses and CD8+-mediated T-cell responses compared to the wildtype vaccine in vaccinated mice, with a notable enhancement in responses to subdominant T-cell epitopes but equal responses to dominant epitopes and similar rates of survival following a tumour challenge. The impairment of cell\u2013cell fusion and the enhanced immunogenicity profile of this HERV-W vaccine strengthens the prospects of obtaining a meaningful immune response against HERV-W in patients with HERV-W-overexpressing cancers.<\/jats:p>","DOI":"10.3390\/v15081686","type":"journal-article","created":{"date-parts":[[2023,8,3]],"date-time":"2023-08-03T11:08:43Z","timestamp":1691060923000},"page":"1686","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["The Insertion of an Evolutionary Lost Four-Amino-Acid Cytoplasmic Tail Peptide into a Syncytin-1 Vaccine Increases T- and B-Cell Responses in Mice"],"prefix":"10.3390","volume":"15","author":[{"given":"Isabella","family":"Skandorff","sequence":"first","affiliation":[{"name":"Department of Immunology and Microbiology, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark"},{"name":"InProTher, COBIS, Ole Maaloesvej 3, 2200 Copenhagen, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jasmin","family":"Gille","sequence":"additional","affiliation":[{"name":"Institute of Medical Microbiology and Hygiene, Molecular Microbiology, University of Regensburg Germany, 93053 Regensburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5460-7789","authenticated-orcid":false,"given":"Emeline","family":"Ragonnaud","sequence":"additional","affiliation":[{"name":"InProTher, COBIS, Ole Maaloesvej 3, 2200 Copenhagen, Denmark"},{"name":"Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anne-Marie","family":"Andersson","sequence":"additional","affiliation":[{"name":"InProTher, COBIS, Ole Maaloesvej 3, 2200 Copenhagen, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1520-8299","authenticated-orcid":false,"given":"Silke","family":"Schr\u00f6del","sequence":"additional","affiliation":[{"name":"Sirion Biotech GmbH, Am Haag 6, 82166 Graefelfing, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Christian","family":"Thirion","sequence":"additional","affiliation":[{"name":"Sirion Biotech GmbH, Am Haag 6, 82166 Graefelfing, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ralf","family":"Wagner","sequence":"additional","affiliation":[{"name":"Institute of Medical Microbiology and Hygiene, Molecular Microbiology, University of Regensburg Germany, 93053 Regensburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Peter Johannes","family":"Holst","sequence":"additional","affiliation":[{"name":"InProTher, COBIS, Ole Maaloesvej 3, 2200 Copenhagen, Denmark"},{"name":"Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,8,3]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Grandi, N., Cadeddu, M., Blomberg, J., Mayer, J., and Tramontano, E. (2018). HERV-W group evolutionary history in non-human primates: Characterization of ERV-W orthologs in Catarrhini and related ERV groups in Platyrrhini. BMC Evol. Biol., 18.","DOI":"10.1186\/s12862-018-1125-1"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1186\/1742-4690-1-32","article-title":"Identification of endogenous retroviral reading frames in the human genome","volume":"1","author":"Villesen","year":"2004","journal-title":"Retrovirology"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"3321","DOI":"10.1128\/JVI.74.7.3321-3329.2000","article-title":"An Envelope Glycoprotein of the Human Endogenous Retrovirus HERV-W Is Expressed in the Human Placenta and Fuses Cells Expressing the Type D Mammalian Retrovirus Receptor","volume":"74","author":"Blond","year":"2000","journal-title":"J. Virol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"785","DOI":"10.1038\/35001608","article-title":"Syncytin is a captive retroviral envelope protein involved in human placental morphogenesis","volume":"403","author":"Mi","year":"2000","journal-title":"Nature"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"31","DOI":"10.1111\/apm.12474","article-title":"Expression and function of endogenous retroviruses in the placenta","volume":"124","author":"Denner","year":"2016","journal-title":"APMIS"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"3566","DOI":"10.1128\/MCB.23.10.3566-3574.2003","article-title":"Direct Involvement of HERV-W Env Glycoprotein in Human Trophoblast Cell Fusion and Differentiation","volume":"23","author":"Frendo","year":"2003","journal-title":"Mol. Cell. Biol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"184","DOI":"10.1111\/j.1365-2567.2012.03568.x","article-title":"Immune cell activation by trophoblast-derived microvesicles is mediated by syncytin 1","volume":"136","author":"Holder","year":"2012","journal-title":"Immunology"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"933","DOI":"10.1016\/j.placenta.2012.08.004","article-title":"The endogenous retroviral envelope protein syncytin-1 inhibits LPS\/PHA-stimulated cytokine responses in human blood and is sorted into placental exosomes","volume":"33","author":"Tolosa","year":"2012","journal-title":"Placenta"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1011","DOI":"10.1016\/j.yexcr.2005.12.010","article-title":"CpG methylation suppresses transcriptional activity of human syncytin-1 in non-placental tissues","volume":"312","author":"Pajer","year":"2006","journal-title":"Exp. Cell Res."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"195","DOI":"10.1093\/dnares\/dsp011","article-title":"Comparative methylation of ERVWE1\/syncytin-1 and other human endogenous retrovirus LTRs in placenta tissues","volume":"16","author":"Gimenez","year":"2009","journal-title":"DNA Res."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"104","DOI":"10.1007\/s12672-023-00702-6","article-title":"Molecular mechanisms of syncytin-1 in tumors and placental development related diseases","volume":"14","author":"Wang","year":"2023","journal-title":"Discov. Oncol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"462","DOI":"10.3389\/fmicb.2018.00462","article-title":"HERV envelope proteins: Physiological role and pathogenic potential in cancer and autoimmunity","volume":"9","author":"Grandi","year":"2018","journal-title":"Front. Microbiol."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"M\u00fcller, M.D., Holst, P.J., and Nielsen, K.N. (2022). A Systematic Review of Expression and Immunogenicity of Human Endogenous Retroviral Proteins in Cancer and Discussion of Therapeutic Approaches. Int. J. Mol. Sci., 23.","DOI":"10.3390\/ijms23031330"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Grandi, N., and Tramontano, E. (2017). Type W human endogenous retrovirus (HERV-W) integrations and their mobilization by L1 machinery: Contribution to the human transcriptome and impact on the host physiopathology. Viruses, 9.","DOI":"10.3390\/v9070162"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Dittmar, T., Weiler, J., Luo, T., and Hass, R. (2021). Cell-Cell Fusion Mediated by Viruses and HERV-Derived Fusogens in Cancer Initiation and Progression. Cancers, 13.","DOI":"10.3390\/cancers13215363"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Bastida-Ruiz, D., Van Hoesen, K., and Cohen, M. (2016). The dark side of cell fusion. Int. J. Mol. Sci., 17.","DOI":"10.3390\/ijms17050638"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Andersson, A.-M.C., Schwerdtfeger, M., and Holst, P.J. (2018). Virus-Like-Vaccines against HIV. Vaccines, 6.","DOI":"10.3390\/vaccines6010010"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Skandorff, I., Ragonnaud, E., Gille, J., Andersson, A.-M., Schr\u00f6del, S., Duvnjak, L., Turner, L., Thirion, C., Wagner, R., and Holst, P.J. (2023). Human Ad19a\/64 HERV-W Vaccines Uncover Immunosuppression Domain-Dependent T-Cell Response Differences in Inbred Mice. Int. J. Mol. Sci., 24.","DOI":"10.3390\/ijms24129972"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1956","DOI":"10.1095\/biolreprod.104.033340","article-title":"Functional characterization of the placental fusogenic membrane protein syncytin","volume":"71","author":"Chang","year":"2004","journal-title":"Biol. Reprod."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"5585","DOI":"10.1128\/JVI.79.9.5585-5593.2005","article-title":"Synthesis, Assembly, and Processing of the Env ERVWE1\/Syncytin Human Endogenous Retroviral Envelope","volume":"79","author":"Cheynet","year":"2005","journal-title":"J. Virol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1895","DOI":"10.1093\/molbev\/msh206","article-title":"Evidence of selection on the domesticated ERVWE1 env retroviral element involved in placentation","volume":"21","author":"Bonnaud","year":"2004","journal-title":"Mol. Biol. Evol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"731","DOI":"10.1089\/088922200308738","article-title":"Chromosomal Distribution and Coding Capacity of the Human Endogenous Retrovirus HERV-W Family","volume":"16","author":"Bouton","year":"2000","journal-title":"AIDS Res. Hum. Retroviruses"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1006\/viro.1999.9792","article-title":"Molecular Cloning and Characterization of MSRV-Related Sequences Associated with Retrovirus-like Particles","volume":"260","author":"Bedin","year":"1999","journal-title":"Virology"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1007\/978-1-62703-679-5_11","article-title":"Engineering adenovirus genome by Bacterial Artificial Chromosome (BAC) technology","volume":"1089","author":"Ruzsics","year":"2014","journal-title":"Methods Mol. Biol."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Daradoumis, J., Ragonnaud, E., Skandorff, I., Nielsen, K.N., Bermejo, A.V., Andersson, A.-M., Schroedel, S., Thirion, C., Neukirch, L., and Holst, P.J. (2023). An Endogenous Retrovirus Vaccine Encoding an Envelope with a Mutated Immunosuppressive Domain in Combination with Anti-PD1 Treatment Eradicates Established Tumours in Mice. Viruses, 15.","DOI":"10.3390\/v15040926"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"3129","DOI":"10.4049\/jimmunol.1800031","article-title":"GM-CSF Culture Revisited: Preparation of Bulk Populations of Highly Pure Dendritic Cells from Mouse Bone Marrow","volume":"201","author":"Jin","year":"2018","journal-title":"J. Immunol."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"3822","DOI":"10.1128\/JVI.02568-07","article-title":"Single-Dose Protection against Plasmodium berghei by a Simian Adenovirus Vector Using a Human Cytomegalovirus Promoter Containing Intron A","volume":"82","author":"Sridhar","year":"2008","journal-title":"J. Virol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"3339","DOI":"10.4049\/jimmunol.180.5.3339","article-title":"MHC Class II-Associated Invariant Chain Linkage of Antigen Dramatically Improves Cell-Mediated Immunity Induced by Adenovirus Vaccines 1","volume":"180","author":"Holst","year":"2008","journal-title":"J. Immunol."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Holst, P.J., Jensen, B.A.H., Ragonnaud, E., Thomsen, A.R., and Christensen, J.P. (2015). Targeting of non-dominant antigens as a vaccine strategy to broaden T-cell responses during chronic viral infection. PLoS ONE, 10.","DOI":"10.1371\/journal.pone.0117242"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"486","DOI":"10.1093\/nar\/26.2.486","article-title":"Activation of stress-activated MAP protein kinases up-regulates expression of transgenes driven by the cytomegalovirus immediate\/early promoter","volume":"26","author":"Bruening","year":"1998","journal-title":"Nucleic Acids Res."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"6442","DOI":"10.1128\/JVI.76.13.6442-6452.2002","article-title":"The Envelope Glycoprotein of Human Endogenous Retrovirus Type W Uses a Divergent Family of Amino Acid Transporters\/Cell Surface Receptors","volume":"76","author":"Lavillette","year":"2002","journal-title":"J. Virol."},{"key":"ref_32","first-page":"556","article-title":"Human endogenous retroviral syncytin exerts inhibitory effect on invasive phenotype of B16F10 melanoma cells","volume":"25","author":"Mo","year":"2013","journal-title":"Chin. J. Cancer Res."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"2725","DOI":"10.1002\/eji.200939543","article-title":"Vaccination with an adenoviral vector encoding the tumor antigen directly linked to invariant chain induces potent CD4+ T-cell-independent CD8+ T-cell-mediated tumor control","volume":"39","author":"Sorensen","year":"2009","journal-title":"Eur. J. Immunol."},{"key":"ref_34","first-page":"2055217317742425","article-title":"Antibody response against HERV-W env surface peptides differentiates multiple sclerosis and neuromyelitis optica spectrum disorder","volume":"3","author":"Arru","year":"2017","journal-title":"Mult. Scler. J. Exp. Transl. Clin."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"66","DOI":"10.1016\/j.jneuroim.2015.03.003","article-title":"Epitopes of HERV-Wenv induce antigen-specific humoral immunity in multiple sclerosis patients","volume":"280","author":"Mameli","year":"2015","journal-title":"J. Neuroimmunol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"104","DOI":"10.1186\/1742-4690-6-104","article-title":"B cells and monocytes from patients with active multiple sclerosis exhibit increased surface expression of both HERV-H Env and HERV-W Env, accompanied by increased seroreactivity","volume":"6","author":"Brudek","year":"2009","journal-title":"Retrovirology"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"6282","DOI":"10.1038\/s41598-019-42788-5","article-title":"Anti-HERV-W Env antibodies are correlated with seroreactivity against Mycobacterium avium subsp. paratuberculosis in children and youths at T1D risk","volume":"9","author":"Niegowska","year":"2019","journal-title":"Sci. Rep."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"e26889","DOI":"10.4161\/onci.26889","article-title":"Murine leukemia virus envelope gp70 is a shared biomarker for the high-sensitivity quantification of murine tumor burden","volume":"2","author":"Scrimieri","year":"2013","journal-title":"Oncoimmunology"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1458","DOI":"10.18632\/oncotarget.26680","article-title":"Adenovirus based virus-like-vaccines targeting endogenous retroviruses can eliminate growing colorectal cancers in mice","volume":"10","author":"Neukirch","year":"2019","journal-title":"Oncotarget"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"20534","DOI":"10.1073\/pnas.0707873105","article-title":"Placental syncytins: Genetic disjunction between the fusogenic and immunosuppressive activity of retroviral envelope proteins","volume":"104","author":"Mangeney","year":"2007","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_41","unstructured":"Holst, P., Thirion, C., and Neukirch, L. (2019). A Vaccine For Use in The Prophylaxis and\/or Treatment of a Disease. (WO2019043127), U.S. Patent."}],"container-title":["Viruses"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-4915\/15\/8\/1686\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T20:24:51Z","timestamp":1760127891000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-4915\/15\/8\/1686"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,8,3]]},"references-count":41,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2023,8]]}},"alternative-id":["v15081686"],"URL":"https:\/\/doi.org\/10.3390\/v15081686","relation":{},"ISSN":["1999-4915"],"issn-type":[{"value":"1999-4915","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,8,3]]}}}