This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by An, D. S.
Right arrow Articles by Chen, I. S. Y.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by An, D. S.
Right arrow Articles by Chen, I. S. Y.

 Previous Article  |  Next Article 

Journal of Virology, April 2001, p. 3488-3489, Vol. 75, No. 7
0022-538X/01/$04.00+0   DOI: 10.1128/JVI.75.7.3488-3489.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Envelope Gene of the Human Endogenous Retrovirus HERV-W Encodes a Functional Retrovirus Envelope

Dong Sung An, Yi-ming Xie, and Irvin S. Y. Chen*

Department of Microbiology, Immunology, Molecular Genetics, and Medicine, UCLA AIDS Institute, University of California---Los Angeles, Los Angeles, California 90095

Received 27 October 2000/Accepted 12 January 2001


    ABSTRACT
Top
Abstract
Text
References

A member of the human endogenous retrovirus (HERV) family termed HERV-W encodes a highly fusogenic membrane glycoprotein that appears to be expressed specifically in the placenta. It is unclear whether the glycoproteins of the HERVs can serve as functional retrovirus envelope proteins to confer infectivity on retrovirus particles. We found that the HERV-W envelope glycoprotein can form pseudotypes with human immunodeficiency virus type 1 virions and confers tropism for CD4-negative cells. Thus, the HERV-W env gene represents the first HERV env gene demonstrated to encode the functional properties of a retrovirus envelope glycoprotein.


    TEXT
Top
Abstract
Text
References

Human endogenous retroviruses (HERVs) have been estimated to comprise about 0.5 to 1.0% of the human genome (4, 7). All known HERVs are replication incompetent; however, some proviruses have open reading frames capable of encoding functional proteins (7, 11). One member of the newly described HERV family termed HERV-W (2) encodes a highly fusogenic membrane glycoprotein that has been proposed to play a role in normal placental development (2, 8). The HERV-W envelope has been shown to induce syncytium formation in human, simian, and pig cells but not in avian, rodent, or feline cells (2). However, it is unclear whether this glycoprotein can serve as an envelope protein to confer infectivity on retrovirus particles.

We determined whether the HERV-W envelope can confer infectivity on an envelope-defective human immunodeficiency virus type 1 (HIV-1) strain. We used the HIV-1 vector NLEGFPDelta BgIVprX, a derivative of NLthyDelta BgIVprX (9) with a deletion within the HIV env gene and bearing an enhanced green fluorescent protein (EGFP)-encoding reporter gene. This env deletion-containing vector is dependent upon pseudotyping with an envelope for infectivity (data not shown). Virus was recovered by calcium phosphate-mediated cotransfection of 293T cells with a vector expressing the HERV-W envelope (phCMV-ENVpH74) (2). In addition to the entire HERV-W envelope open reading frame, phCMV-ENVpH74 contains 66 bp of the DNA sequence upstream of the HERV-W envelope start codon and 138 bp of the DNA sequence downstream of the HERV-W stop codon derived from the original HERV-W envelope cDNA. Virions were tested for infectivity on human embryonal kidney 293T cells (3) by measuring the EGFP fluorescence of infected cells by flow cytometry. Infection with virions derived by cotransfection of the HERV-W envelope (NLEGFPDelta BgIVprX [HERV-W]) resulted in EGFP expression following infection of 293T cells (Fig. 1). Inclusion of the retrovirus reverse transcriptase inhibitors (RTIs) zidovudine and nevirapine as a control during infection led to loss of EGFP expression. Thus, pseudotyping of HIV-1 virions with the HERV-W envelope results in infectious virus. Consistent with the lack of fusion on mouse cells (2), NLEGFPDelta BglVprX (HERV-W) did not infect mouse B16 cells (data not shown). Similar results were observed when the HERV-W envelope was utilized to pseudotype an extensive-deletion-containing, self-inactivating HIV-1 vector bearing an internal promoter expressing EGFP (SIN18RhMLVE) (5) rescued by complementation with a packaging plasmid to provide virion gag and pol products (data not shown). Compared to vesicular stomatitis virus G envelope pseudotypes, virions with the HERV-W envelope were approximately two- to fivefold lower in titer for comparable p24 Gag antigen levels. Supernatant titers ranged from 5 × 104 to 1 × 105/ml in different experiments. Freezing, thawing, and concentration by ultracentrifugation reduced titers considerably (data not shown). Consistent with previous reports (2), infectious pseudotypes were not observed with a murine leukemia virus (MLV)-based vector (Fig. 1). These results provide the first direct evidence that an HERV envelope glycoprotein can serve as a functional retrovirus envelope.


View larger version (21K):
[in this window]
[in a new window]
  		FIG. 1.   HIV-1 can be pseudotyped with the HERV-W envelope. 293T cells were cotransfected with an HERV-W envelope expression construct and an HIV-1 vector (NLEGFPDelta BgIVprX) or a MLV vector construct (SRalpha EGFP) (1) and packaging plasmid (SVphi-env-MLV) (6). 293T cells (5 × 104) were infected with 1 ml of the supernatant from the cotransfected 293T cells in the presence (+RTI) or absence (-RTI) of zidovudine (5 µM) and nevirapine (5 µM). The concentration of p24 in the HERV-W envelope- and HIV vector-cotransfected supernatant was 1,159 ng/ml. Two days postinfection, cells were analyzed for EGFP expression by flow cytometry. Mock-transfected cells (no infection) were analyzed in parallel. The x axis represents the logarithmic fluorescence intensity of EGFP; the y axis represents the number of events. The percentage of EGFP-positive populations was as indicated in each panel. Ten thousand events were acquired for flow cytometric analysis. The data shown here are representative of three independent experiments.

The HERV-W family of endogenous retroviruses consist of an estimated 30 to 100 provirus copies per haploid human genome (10). The HERV-Ws first entered the genome of primates following the divergence of New World and Old World monkeys (approximately 25 million years ago) (10). Several other HERV families have also been reported (7, 11). In all cases, the endogenous retroviruses are replication defective because of mutations within functional retrovirus genes (7, 11). However, individual open reading frames corresponding to gag, pol, and env have been observed and in some cases have been shown to encode proteins (7, 11). Our results raise the possibility that HERVs could potentially be assembled into infectious virions through transcomplementation with virion proteins encoded by different HERVs. A functional envelope glycoprotein would confer upon the retroviruses the ability to be transmitted vertically and/or horizontally and potentially provide new roles for HERVs in normal physiology and/or pathology.

The pseudotyping of HIV-1 with the HERV-W envelope also raises the possibility that the expression of other HERV envelopes in other tissues of the body may alter the cell tropism of HIV-1. With the complete nucleotide sequence of the human genome near completion, the identification of novel HERVs with the potential to encode functional envelopes will allow testing of the possibility that other envelopes can pseudotype with HIV-1 and potentially contribute to HIV-1 pathogenesis.


    ACKNOWLEDGMENTS

We thank F. Mallet for providing the HERV-W expression vector phCMV-ENVpH74; B. Poon and P. Krogstad for providing reagents and advice; K. Ferbas, V. Gudeman, S. H. Mao, and A. A.-L. Ho for technical support; and L. Duarte and R. Taweesup for manuscript preparation.

This work was supported by NIH grants AI39975-01 and AI36555.


    FOOTNOTES

* Corresponding author. Mailing address: University of California, Los Angeles, Department of Microbiology, Immunology, Molecular Genetics and Medicine, 10833 Le Conte Ave., 11-934 Factor Bldg., Los Angeles, CA 90095. Phone: (310) 825-4793. Fax: (310) 794-7682. E-mail: rtaweesu{at}ucla.edu.


    REFERENCES
Top
Abstract
Text
References

1. An, D. S., R. P. Wersto, B. A. Agricola, M. E. Metzger, S. Lu, R. G. Amado, I. S. Y. Chen, and R. E. Donahue. 2000. Marking and gene expression by a lentivirus vector in transplanted human and nonhuman primate CD34+ cells. J. Virol. 74:1286-1295[Abstract/Free Full Text].
2. Blond, J.-L, D. Lavillette, V. Cheynet, O. Bouton, G. Oriol, S. Chapel-Fernandes, B. Mandrand, F. Mallet, and F.-L. Cosset. 2000. 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. J. Virol. 74:3321-3329[Abstract/Free Full Text].
3. DuBridge, R. B., P. Tang, H. C. Hsia, P. M. Leong, J. H. Miller, and M. P. Calos. 1987. Analysis of mutation in human cells by using an Epstein-Barr virus shuttle system. Mol. Cell. Biol. 7:379-387[Abstract/Free Full Text].
4. Dunham, I., N. Shimizu, B. A. Roe, S. Chissoe, A. R. Hunt, J. E. Collins, R. Bruskiewich, D. M. Beare, M. Clamp, L. J. Smink, R. Ainscough, J. P. Almeida, A. Babbage, C. Bagguley, J. Bailey, K. Barlow, K. N. Bates, O. Beasley, C. P. Bird, S. Blakey, A. M. Bridgeman, D. Buck, J. Burgess, W. D. Burrill, and K. P. O'Brien. 1999. The DNA sequence of human chromosome 22. Nature 402:489-495[CrossRef][Medline].
5. Kung, S. K. R., D. S. An, and I. S. Y. Chen. 2000. A murine leukemia virus (MuLV) long terminal repeat derived from rhesus macaques in the context of a lentivirus vector and MuLV gag sequence results in a high-level gene expression in human T lymphocytes. J. Virol. 74:3668-3681[Abstract/Free Full Text].
6. Landau, N. R., and D. R. Littman. 1992. Packaging system for rapid production of murine leukemia virus vectors with variable tropism. J. Virol. 66:5110-5113[Abstract/Free Full Text].
7. Lower, R., J. Lower, and R. Kurth. 1996. The viruses in all of us: characteristics and biological significance of human endogenous retrovirus sequences. Proc. Natl. Acad. Sci. USA 93:5177-5184[Abstract/Free Full Text].
8. Mi, S., X. Lee, X. Li, G. M. Veldman, H. Finnerty, L. Racie, E. LaVallie, X. Y. Tang, P. Edouard, S. Howes, J. C. J. Keith, and J. M. McCoy. 2000. Syncytin is a captive retroviral envelope protein involved in human placental morphogenesis. Nature 403:785-789[CrossRef][Medline].
9. Poon, B., J. B. M. Jowett, S. A. Stewart, R. W. Armstrong, G. M. Rishton, and I. S. Y. Chen. 1997. Human immunodeficiency virus type 1 vpr gene induces phenotypic effects similar to those of the DNA alkylating agent, nitrogen mustard. J. Virol. 71:3961-3971[Abstract].
10. Voisset, C., A. Blancher, H. Perron, B. Mandrand, F. Mallet, and G. Paranhos-Baccala. 1999. Phylogeny of a novel family of human endogenous retrovirus sequences, HERV-W, in humans and other primates. AIDS Res. Hum. Retroviruses 15:1529-1533[CrossRef][Medline].
11. Wilkinson, D. A., D. L. Mager, and J. C. Leong. 1994. Endogenous human retroviruses, p. 465-535. In J. A. Levy (ed.), The Retroviridae. Plenum Press, New York, N.Y.

Journal of Virology, April 2001, p. 3488-3489, Vol. 75, No. 7
0022-538X/01/$04.00+0   DOI: 10.1128/JVI.75.7.3488-3489.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:

  • Woodward, C. L., Prakobwanakit, S., Mosessian, S., Chow, S. A. (2009). Integrase Interacts with Nucleoporin NUP153 To Mediate the Nuclear Import of Human Immunodeficiency Virus Type 1. J. Virol. 83: 6522-6533 [Abstract] [Full Text]  
  • Antony, J. M., Ellestad, K. K., Hammond, R., Imaizumi, K., Mallet, F., Warren, K. G., Power, C. (2007). The Human Endogenous Retrovirus Envelope Glycoprotein, Syncytin-1, Regulates Neuroinflammation and Its Receptor Expression in Multiple Sclerosis: A Role for Endoplasmic Reticulum Chaperones in Astrocytes. J. Immunol. 179: 1210-1224 [Abstract] [Full Text]  
  • Dewannieux, M., Blaise, S., Heidmann, T. (2005). Identification of a Functional Envelope Protein from the HERV-K Family of Human Endogenous Retroviruses. J. Virol. 79: 15573-15577 [Abstract] [Full Text]  
  • Cheynet, V., Ruggieri, A., Oriol, G., Blond, J.-L., Boson, B., Vachot, L., Verrier, B., Cosset, F.-L., Mallet, F. (2005). Synthesis, Assembly, and Processing of the Env ERVWE1/Syncytin Human Endogenous Retroviral Envelope. J. Virol. 79: 5585-5593 [Abstract] [Full Text]  
  • Potgens, A.J.G., Drewlo, S., Kokozidou, M., Kaufmann, P. (2004). Syncytin: the major regulator of trophoblast fusion? Recent developments and hypotheses on its action. Hum Reprod Update 10: 487-496 [Abstract] [Full Text]  
  • Bannert, N., Kurth, R. (2004). Retroelements and the human genome: New perspectives on an old relation. Proc. Natl. Acad. Sci. USA 101: 14572-14579 [Abstract] [Full Text]  
  • Bonnaud, B., Bouton, O., Oriol, G., Cheynet, V., Duret, L., Mallet, F. (2004). Evidence of Selection on the Domesticated ERVWE1 env Retroviral Element Involved in Placentation. Mol Biol Evol 21: 1895-1901 [Abstract] [Full Text]  
  • Blaise, S., Ruggieri, A., Dewannieux, M., Cosset, F.-L., Heidmann, T. (2004). Identification of an Envelope Protein from the FRD Family of Human Endogenous Retroviruses (HERV-FRD) Conferring Infectivity and Functional Conservation among Simians. J. Virol. 78: 1050-1054 [Abstract] [Full Text]  
  • Blaise, S., de Parseval, N., Benit, L., Heidmann, T. (2003). Genomewide screening for fusogenic human endogenous retrovirus envelopes identifies syncytin 2, a gene conserved on primate evolution. Proc. Natl. Acad. Sci. USA 100: 13013-13018 [Abstract] [Full Text]  
  • Marin, M., Lavillette, D., Kelly, S. M., Kabat, D. (2003). N-Linked Glycosylation and Sequence Changes in a Critical Negative Control Region of the ASCT1 and ASCT2 Neutral Amino Acid Transporters Determine Their Retroviral Receptor Functions. J. Virol. 77: 2936-2945 [Abstract] [Full Text]  
  • Lavillette, D., Marin, M., Ruggieri, A., Mallet, F., Cosset, F.-L., Kabat, D. (2002). The Envelope Glycoprotein of Human Endogenous Retrovirus Type W Uses a Divergent Family of Amino Acid Transporters/Cell Surface Receptors. J. Virol. 76: 6442-6452 [Abstract] [Full Text]  
  • Benit, L., Dessen, P., Heidmann, T. (2001). Identification, Phylogeny, and Evolution of Retroviral Elements Based on Their Envelope Genes. J. Virol. 75: 11709-11719 [Abstract] [Full Text]  
  • Overbaugh, J., Miller, A. D., Eiden, M. V. (2001). Receptors and Entry Cofactors for Retroviruses Include Single and Multiple Transmembrane-Spanning Proteins as well as Newly Described Glycophosphatidylinositol-Anchored and Secreted Proteins. Microbiol. Mol. Biol. Rev. 65: 371-389 [Abstract] [Full Text]  

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by An, D. S.
Right arrow Articles by Chen, I. S. Y.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by An, D. S.
Right arrow Articles by Chen, I. S. Y.

Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»