scholarly journals Mutation of the Putative Immunosuppressive Domain of the Retroviral Envelope Glycoprotein Compromises Infectivity

2017 ◽  
Vol 91 (21) ◽  
Author(s):  
Urszula Eksmond ◽  
Bryony Jenkins ◽  
Julia Merkenschlager ◽  
Walther Mothes ◽  
Jonathan P. Stoye ◽  
...  
Keyword(s):  
Envelope Glycoprotein ◽  
Leukemia Virus ◽  
Human Cells ◽  
Endogenous Retroviruses ◽  
Envelope Glycoproteins ◽  
Immunosuppressive Activity ◽  
Pathogenic Potential ◽  
Cationic Amino Acid ◽  
Conserved Domain ◽  
Key Residues

ABSTRACT The envelope glycoprotein of diverse endogenous and exogenous retroviruses is considered inherently immunosuppressive. Extensive work mapped the immunosuppressive activity to a highly conserved domain, termed the immunosuppressive domain (ISD), in the transmembrane (TM) subunit of the envelope glycoprotein and identified two naturally polymorphic key residues that afford immunosuppressive activity to distinct envelope glycoproteins. Concurrent mutation of these two key residues (E14R and A20F) in the envelope glycoprotein of the Friend murine leukemia virus (F-MLV) ISD has been reported to abolish its immunosuppressive activity, without affecting its fusogenicity, and to weaken the ability of the virus to replicate specifically in immunocompetent hosts. Here, we show that mutation of these key residues did, in fact, result in a substantial loss of F-MLV infectivity, independently of host immunity, challenging whether associations exist between the two. Notably, a loss of infectivity incurred by the F-MLV mutant with the E14R and A20F double ISD mutation was conditional on expression of the ecotropic envelope receptor murine cationic amino acid transporter-1 (mCAT1) in the virus-producing cell. Indeed, the F-MLV mutant retained infectivity when it was produced by human cells, which naturally lack mCAT1 expression, but not by murine cells. Furthermore, mCAT1 overexpression in human cells impaired the infectivity of both the F-MLV double mutant and the wild-type F-MLV strain, suggesting a finely tuned relationship between the levels of mCAT1 in the producer cell and the infectivity of the virions produced. An adverse effect on this relationship, rather than disruption of the putative ISD, is therefore more likely to explain the loss of F-MLV infectivity incurred by mutations in key ISD residues E14 and A20. IMPORTANCE Retroviruses can interact with their hosts in ways that, although not entirely understood, can greatly influence their pathogenic potential. One such example is a putative immunosuppressive activity, which has been mapped to a conserved domain of the retroviral envelope glycoprotein of several exogenous as well as endogenous retroviruses. In this study, mutations naturally found in some envelope glycoproteins lacking immunosuppressive activity were shown to affect retrovirus infectivity only if the host cell that produced the retrovirus also expressed the cellular entry receptor. These findings shed light on a novel role for this conserved domain in providing the necessary stability to the envelope glycoprotein in order to withstand the interaction with the cellular receptor during virus formation. This function of the domain is critical for further elucidation of the mechanism of immunosuppression mediated by the retroviral envelope glycoprotein.

scholarly journals CAT1/SLC7A1 acts as a cellular receptor for bovine leukemia virus infection

2019 ◽  
Author(s):  
Lanlan Bai ◽  
Hirotaka Sato ◽  
Yoshinao Kubo ◽  
Satoshi Wada ◽  
Yoko Aida
Keyword(s):  
Cell Surface ◽  
Envelope Glycoprotein ◽  
Bovine Leukemia Virus ◽  
Virus Entry ◽  
Leukemia Virus ◽  
Cellular Receptor ◽  
Cationic Amino Acid Transporter ◽  
Cell Leukemia ◽  
Cationic Amino Acid ◽  
Human T Cell

AbstractBovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis, the most common neoplastic disease of cattle, which is closely related to human T-cell leukemia viruses. BLV has spread worldwide and causes a serious problem for the cattle industry. The cellular receptor specifically binds with viral envelope glycoprotein (Env) and this attachment mediates cell fusion to lead virus entry. BLV Env reportedly binds to cationic amino acid transporter 1 (CAT1)/SLC7A1, but whether the CAT1/SLC7A1 is an actual receptor for BLV remains unknown. Here, we showed that CAT1 functioned as an infection receptor, interacting with BLV particles. Cells expressing undetectable CAT1 levels were resistant to BLV infection but became highly susceptible upon CAT1 overexpression. CAT1 exhibited specific binding to BLV particles on the cell surface and co-localized with the Env in endomembrane compartments and membrane. Knockdown of CAT1 in permissive cells significantly reduced binding to BLV particles and BLV infection. In addition, bovine serum with neutralizing activity from a BLV-infected cattle inhibited BLV particles. Expression of CAT1 from various species demonstrated no species-specificity for BLV infection, implicating CAT1 as a functional BLV receptor responsible for its broad host range. These findings provide insights for BLV infection and for developing new strategies for treating BLV and preventing its spread.Author SummaryBovine leukemia virus (BLV), which can infect a variety of animal species and induce lymphoma in cattle, is a member of the familyRetroviridae. BLV induces huge economic losses by not only lymphoma but also subclinical forms of the disease. In addition, BLV is frequently used as an animal model of human T-cell leukemia virus (HTLV), as BLV has many similar characteristics to HTLV. Thus, understanding BLV pathogenesis contribute to resolve not only BLV-but also HTLV-induced problems. Retroviral envelope glycoprotein (Env) is specifically recognized by the cellular receptor at cell surface, which induces a conformational changes between viral and cell membrane to entry. Thus, the elucidation of cellular receptor for BLV infection is very important for virus entry. However, the BLV receptor has not been identified yet. In the current study, we found that BLV Env protein binds to cationic amino acid transporter 1 (CAT1)/SLC7A1 at cell surface, artificial expression of CAT1 in CAT1-negative cells confers the cells susceptible to BLV infection, and CAT1-silencing significantly reduces BLV infection, concluding that CAT1 is the BLV receptor. These findings will have far reaching great advantages of insights in the retrovirus study.

scholarly journals Porcine Endogenous Retroviruses Infect Cells Lacking Cognate Receptors by an Alternative Pathway: Implications for Retrovirus Evolution and Xenotransplantation

2004 ◽  
Vol 78 (16) ◽  
pp. 8868-8877 ◽  
Author(s):  
Dimitri Lavillette ◽  
David Kabat
Keyword(s):  
Host Range ◽  
Receptor Binding ◽  
Envelope Glycoprotein ◽  
Alternative Pathway ◽  
Leukemia Virus ◽  
Endogenous Retroviruses ◽  
Wild Type ◽  
Porcine Endogenous Retroviruses ◽  
Gibbon Ape Leukemia Virus ◽  
Porcine Tissues

ABSTRACT A PHQ motif near the amino termini of gammaretroviral envelope glycoprotein surface (SU) subunits is important for infectivity but not for incorporation into virions or binding to cognate receptors. The H residue of this motif is most critical, with all substitutions we tested being inactive. Interestingly, porcine endogenous retroviruses (PERVs) of all three host-range groups, A, B, and C, lack full PHQ motifs, but most members have an H residue at position 10. H10A PERV mutants are noninfectious but were efficiently transactivated by adding to the assays a PHQ-containing SU or receptor-binding subdomain (RBD) derived from a gibbon ape leukemia virus (GALV). A requirement of this transactivation was a functional GALV receptor on the cells. In contrast to this heterologous transactivation, PERV RBDs and SUs were inactive in all tested cells, including porcine ST-IOWA cells. Surprisingly, transactivation by GALV RBD enabled wild-type or H10A mutant PERVs of all three host-range groups to efficiently infect cells from humans and rodents that lack functional PERV receptors and it substantially enhanced infectivities of wild-type PERVs, even for cells with PERV receptors. Thus, PERVs can suboptimally infect cells that contain cognate receptors or they can employ a transactivation pathway to more efficiently infect all cells. This ability to infect cells lacking cognate receptors was previously demonstrated only for nontransmissible variant gammaretroviruses with recombinant and mutant envelope glycoproteins. We conclude that some endogenously inherited mammalian retroviruses also have a receptor-independent means for overcoming host-range and interference barriers, implying a need for caution in xenotransplantation, especially of porcine tissues.

scholarly journals Retrovirus Vectors Bearing Jaagsiekte Sheep Retrovirus Env Transduce Human Cells by Using a New Receptor Localized to Chromosome 3p21.3

2000 ◽  
Vol 74 (10) ◽  
pp. 4698-4704 ◽  
Author(s):  
Sharath K. Rai ◽  
James C. DeMartini ◽  
A. Dusty Miller
Keyword(s):  
Host Range ◽  
Chemokine Receptors ◽  
Lung Tumor ◽  
High Titer ◽  
Leukemia Virus ◽  
Human Infection ◽  
Human Cells ◽  
Careful Examination ◽  
Chromosome 3 ◽  
Jaagsiekte Sheep Retrovirus

ABSTRACT Jaagsiekte sheep retrovirus (JSRV) is a type D retrovirus associated with a contagious lung tumor of sheep, ovine pulmonary carcinoma. Other than sheep, JSRV is known to infect goats, but there is no evidence of human infection. Until now it has not been possible to study the host range for JSRV because of the inability to grow this virus in culture. Here we show that the JSRV envelope protein (Env) can be used to pseudotype Moloney murine leukemia virus (MoMLV)-based retrovirus vectors and that such vectors can transduce human cells in culture. We constructed hybrid retrovirus packaging cells that express the JSRV Env and the MoMLV Gag-Pol proteins and can produce JSRV-pseudotype vectors at titers of up to 106 alkaline phosphatase-positive focus-forming units/ml. Using this high-titer virus, we have studied the host range for JSRV, which includes sheep, human, monkey, bovine, dog, and rabbit cells but not mouse, rat, or hamster cells. Considering the inability of the JSRV-pseudotype vector to transduce hamster cells, we used the hamster cell line-based Stanford G3 panel of whole human genome radiation hybrids to phenotypically map the JSRV receptor (JVR) gene within the p21.3 region of human chromosome 3. JVR is likely a new retrovirus receptor, as none of the previously identified retrovirus receptors localizes to the same position. Several chemokine receptors that have been shown to serve as coreceptors for lentivirus infection are clustered in the same region of chromosome 3; however, careful examination shows that the JSRV receptor does not colocalize with any of these genes.

scholarly journals Absence of Replication-Competent Human-Tropic Porcine Endogenous Retroviruses in the Germ Line DNA of Inbred Miniature Swine

2004 ◽  
Vol 78 (5) ◽  
pp. 2502-2509 ◽  
Author(s):  
Linda Scobie ◽  
Samantha Taylor ◽  
James C. Wood ◽  
Kristen M. Suling ◽  
Gary Quinn ◽  
...  
Keyword(s):  
Genomic Dna ◽  
Germ Line ◽  
Human Cells ◽  
Endogenous Retroviruses ◽  
Open Reading Frames ◽  
Miniature Swine ◽  
Dna Libraries ◽  
Porcine Endogenous Retroviruses ◽  
Perv Transmission

ABSTRACT The potential transmission of porcine endogenous retroviruses (PERVs) has raised concern in the development of porcine xenotransplantation products. Our previous studies have resulted in the identification of animals within a research herd of inbred miniature swine that lack the capacity to transmit PERV to human cells in vitro. In contrast, other animals were capable of PERV transmission. The PERVs that were transmitted to human cells are recombinants between PERV-A and PERV-C in the post-VRA region of the envelope (B. A. Oldmixon, J. C. Wood, T. A. Ericsson, C. A. Wilson, M. E. White-Scharf, G. Andersson, J. L. Greenstein, H. J. Schuurman, and C. Patience, J. Virol. 76:3045-3048, 2002); these viruses we term PERV-A/C. This observation prompted us to determine whether these human-tropic replication-competent (HTRC) PERV-A/C recombinants were present in the genomic DNA of these miniature swine. Genomic DNA libraries were generated from one miniature swine that transmitted HTRC PERV as well as from one miniature swine that did not transmit HTRC PERV. HTRC PERV-A/C proviruses were not identified in the germ line DNAs of these pigs by using genomic mapping. Similarly, although PERV-A loci were identified in both libraries that possessed long env open reading frames, the Env proteins encoded by these loci were nonfunctional according to pseudotype assays. In the absence of a germ line source for HTRC PERV, further studies are warranted to assess the mechanisms by which HTRC PERV can be generated. Once identified, it may prove possible to generate animals with further reduced potential to produce HTRC PERV.

scholarly journals Analysis of the Interaction of Primate Retroviruses with the Human RNA Interference Machinery

2007 ◽  
Vol 81 (22) ◽  
pp. 12218-12226 ◽  
Author(s):  
Jennifer Lin ◽  
Bryan R. Cullen
Keyword(s):  
Rna Interference ◽  
Virus Type ◽  
Leukemia Virus ◽  
Foamy Virus ◽  
Human Cells ◽  
Small Interfering Rnas ◽  
Cell Leukemia Virus Type ◽  
Human T Cell ◽  
Hiv 1

ABSTRACT The question of whether retroviruses, including human immunodeficiency virus type 1 (HIV-1), interact with the cellular RNA interference machinery has been controversial. Here, we present data showing that neither HIV-1 nor human T-cell leukemia virus type 1 (HTLV-1) expresses significant levels of either small interfering RNAs or microRNAs in persistently infected T cells. We also demonstrate that the retroviral nuclear transcription factors HIV-1 Tat and HTLV-1 Tax, as well as the Tas transactivator encoded by primate foamy virus, fail to inhibit RNA interference in human cells. Moreover, the stable expression of physiological levels of HIV-1 Tat did not globally inhibit microRNA production or expression in infected human cells. Together, these data argue that HIV-1 and HTLV-1 neither induce the production of viral small interfering RNAs or microRNAs nor repress the cellular RNA interference machinery in infected cells.

scholarly journals Peptides presenting the binding site of human CD4 for the HIV-1 envelope glycoprotein gp120

2012 ◽  
Vol 8 ◽  
pp. 1858-1866 ◽  
Author(s):  
Julia Meier ◽  
Kristin Kassler ◽  
Heinrich Sticht ◽  
Jutta Eichler
Keyword(s):  
Amino Acids ◽  
Binding Site ◽  
Envelope Glycoprotein ◽  
Conformational Stability ◽  
Cellular Receptor ◽  
Binding Assays ◽  
Glycoprotein Gp120 ◽  
Dynamics Simulations ◽  
Key Residues ◽  
Hiv 1

Based on the structure of the HIV-1 glycoprotein gp120 in complex with its cellular receptor CD4, we have designed and synthesized peptides that mimic the binding site of CD4 for gp120. The ability of these peptides to bind to gp120 can be strongly enhanced by increasing their conformational stability through cyclization, as evidenced by binding assays, as well as through molecular-dynamics simulations of peptide–gp120 complexes. The specificity of the peptide–gp120 interaction was demonstrated by using peptide variants, in which key residues for the interaction with gp120 were replaced by alanine or D-amino acids.

scholarly journals Retroviral Restriction Factors Fv1 and TRIM5α Act Independently and Can Compete for Incoming Virus before Reverse Transcription

2006 ◽  
Vol 80 (5) ◽  
pp. 2100-2105 ◽  
Author(s):  
Luca D. Passerini ◽  
Zuzana Keckesova ◽  
Greg J. Towers
Keyword(s):  
Life Cycle ◽  
Reverse Transcription ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Viral Life Cycle ◽  
Human Cells ◽  
Restriction Factors ◽  
Retroviral Infection ◽  
The Relationship ◽  
Murine Leukemia

ABSTRACT The restriction factors Fv1 and TRIM5α provide dominant blocks to retroviral infection, targeting incoming capsids at a postentry, preintegration step. They both restrict N-tropic murine leukemia virus with similar specificity yet act at different points in the viral life cycle. TRIM5α-restricted virus is usually unable to reverse transcribe, whereas Fv1-restricted virus reverse transcribes normally. Here we investigate the relationship between these two restriction factors by expressing Fv1 alleles in human cells. We demonstrate that Fv1 is able to compete with TRIM5α for virus before reverse transcription. In human cells expressing Fv1b, N-tropic restricted virus becomes less infectious but reverse transcribes more efficiently, indicating competition between the two antiviral molecules and protection of the virus from TRIM5α by Fv1. Our findings suggest that, like TRIM5α, Fv1 interacts with virus before reverse transcription, but the consequences of this interaction are not realized until a later stage of the life cycle. We also demonstrate that Fv1 is functionally independent of TRIM5α when expressed in human cells.

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