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Byun H, Singh GB, Xu WK, Das P, Reyes A, Battenhouse A, Wylie DC, Santiago ML, Lozano MM, Dudley JP. Apobec-mediated retroviral hypermutation in vivo is dependent on mouse strain. PLoS Pathog 2024; 20:e1012505. [PMID: 39208378 DOI: 10.1371/journal.ppat.1012505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 08/14/2024] [Indexed: 09/04/2024] Open
Abstract
Replication of the complex retrovirus mouse mammary tumor virus (MMTV) is antagonized by murine Apobec3 (mA3), a member of the Apobec family of cytidine deaminases. We have shown that MMTV-encoded Rem protein inhibits proviral mutagenesis by the Apobec enzyme, activation-induced cytidine deaminase (AID) during viral replication in BALB/c mice. To further study the role of Rem in vivo, we have infected C57BL/6 (B6) mice with a superantigen-independent lymphomagenic strain of MMTV (TBLV-WT) or a mutant strain that is defective in Rem and its cleavage product Rem-CT (TBLV-SD). Compared to BALB/c, B6 mice were more susceptible to TBLV infection and tumorigenesis. Furthermore, unlike MMTV, TBLV induced T-cell tumors in B6 μMT mice, which lack membrane-bound IgM and conventional B-2 cells. At limiting viral doses, loss of Rem expression in TBLV-SD-infected B6 mice accelerated tumorigenesis compared to TBLV-WT in either wild-type B6 or AID-knockout mice. Unlike BALB/c results, high-throughput sequencing indicated that proviral G-to-A or C-to-T mutations were unchanged regardless of Rem expression in B6 tumors. However, knockout of both AID and mA3 reduced G-to-A mutations. Ex vivo stimulation showed higher levels of mA3 relative to AID in B6 compared to BALB/c splenocytes, and effects of agonists differed in the two strains. RNA-Seq revealed increased transcripts related to growth factor and cytokine signaling in TBLV-SD-induced tumors relative to TBLV-WT-induced tumors, consistent with another Rem function. Thus, Rem-mediated effects on tumorigenesis in B6 mice are independent of Apobec-mediated proviral hypermutation.
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Affiliation(s)
- Hyewon Byun
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America
| | - Gurvani B Singh
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America
| | - Wendy Kaichun Xu
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America
| | - Poulami Das
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America
| | - Alejandro Reyes
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America
| | - Anna Battenhouse
- Center for Biomedical Research Support, The University of Texas at Austin, Austin, Texas, United States of America
| | - Dennis C Wylie
- Center for Biomedical Research Support, The University of Texas at Austin, Austin, Texas, United States of America
| | - Mario L Santiago
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Mary M Lozano
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America
| | - Jaquelin P Dudley
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America
- LaMontagne Center for Infectious Disease, The University of Texas at Austin, Austin, Texas, United States of America
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Byun H, Singh GB, Xu WK, Das P, Reyes A, Battenhouse A, Wylie DC, Lozano MM, Dudley JP. Apobec-Mediated Retroviral Hypermutation In Vivo is Dependent on Mouse Strain. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.02.565355. [PMID: 37961113 PMCID: PMC10635078 DOI: 10.1101/2023.11.02.565355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Replication of the complex retrovirus mouse mammary tumor virus (MMTV) is antagonized by murine Apobec3 (mA3), a member of the Apobec family of cytidine deaminases. We have shown that MMTV-encoded Rem protein inhibits proviral mutagenesis by the Apobec enzyme, activation-induced cytidine deaminase (AID) during viral replication in BALB/c mice. To further study the role of Rem in vivo , we have infected C57BL/6 (B6) mice with a superantigen-independent lymphomagenic strain of MMTV (TBLV-WT) or a mutant strain (TBLV-SD) that is defective in Rem and its cleavage product Rem-CT. Unlike MMTV, TBLV induced T-cell tumors in µMT mice, indicating that mature B cells, which express the highest AID levels, are not required for TBLV replication. Compared to BALB/c, B6 mice were more susceptible to TBLV infection and tumorigenesis. The lack of Rem expression accelerated B6 tumorigenesis at limiting doses compared to TBLV-WT in either wild-type B6 or AID-deficient mice. However, unlike proviruses from BALB/c mice, high-throughput sequencing indicated that proviral G-to-A or C-to-T changes did not significantly differ in the presence and absence of Rem expression. Ex vivo stimulation showed higher levels of mA3 relative to AID in B6 compared to BALB/c splenocytes, but effects of agonists differed in the two strains. RNA-Seq revealed increased transcripts related to growth factor and cytokine signaling in TBLV-SD-induced tumors relative to those from TBLV-WT, consistent with a third Rem function. Thus, Rem-mediated effects on tumorigenesis in B6 mice are independent of Apobec-mediated proviral hypermutation.
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Beilinson HA, Sevilleja A, Spring J, Benavides F, Beilinson V, Neokosmidis N, Golovkina T. A single dominant locus restricts retrovirus replication in YBR/Ei mice. J Virol 2023; 97:e0068523. [PMID: 37578238 PMCID: PMC10506465 DOI: 10.1128/jvi.00685-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 06/28/2023] [Indexed: 08/15/2023] Open
Abstract
Differential responses to viral infections are influenced by the genetic makeup of the host. Studies of resistance to retroviruses in human populations are complicated due to the inability to conduct proof-of-principle studies. Inbred mouse lines, which have a range of susceptible phenotypes to retroviruses, are an ideal tool to identify and characterize mechanisms of resistance and define their genetic underpinnings. YBR/Ei mice become infected with Mouse Mammary Tumor Virus, a mucosally transmitted murine retrovirus, but eliminate the virus from their pedigrees. Virus elimination correlates with a lack of virus-specific neonatal oral tolerance, which is a major mechanism for blocking the anti-virus response in susceptible mice. Virus control is unrelated to virus-neutralizing antibodies, cytotoxic CD8+ T cells, NK cells, and NK T cells, which are the best characterized mechanisms of resistance to retroviruses. We identified a single, dominant locus that controls the resistance mechanism, which we provisionally named attenuation of virus titers (Avt) and mapped to the distal region of chromosome 18. IMPORTANCE Elucidation of the mechanism that mediates resistance to retroviruses is of fundamental importance to human health, as it will ultimately lead to knowledge of the genetic differences among individuals in susceptibility to microbial infections.
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Affiliation(s)
- Helen A. Beilinson
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA
| | - Amanda Sevilleja
- Committee on Immunology, University of Chicago, Chicago, Illinois, USA
| | - Jessica Spring
- Committee on Microbiology, University of Chicago, Chicago, Illinois, USA
| | - Fernando Benavides
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Vera Beilinson
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA
| | | | - Tatyana Golovkina
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA
- Committee on Immunology, University of Chicago, Chicago, Illinois, USA
- Committee on Microbiology, University of Chicago, Chicago, Illinois, USA
- Committee on Genetics, Genomics and System Biology, University of Chicago, Chicago, Illinois, USA
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Unconventional p97/VCP-Mediated Endoplasmic Reticulum-to-Endosome Trafficking of a Retroviral Protein. J Virol 2021; 95:e0053121. [PMID: 33952644 DOI: 10.1128/jvi.00531-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Mouse mammary tumor virus (MMTV) encodes a Rem precursor protein that specifies both regulatory and accessory functions. Rem is cleaved at the endoplasmic reticulum (ER) membrane into a functional N-terminal signal peptide (SP) and the C terminus (Rem-CT). Rem-CT lacks a membrane-spanning domain and a known ER retention signal, and yet it was not detectably secreted into cell supernatants. Inhibition of intracellular trafficking by the drug brefeldin A (BFA), which interferes with the ER-to-Golgi secretory pathway, resulted in dramatically reduced intracellular Rem-CT levels that were not rescued by proteasomal or lysosomal inhibitors. A Rem mutant lacking glycosylation was cleaved into SP and Rem-CT but was insensitive to BFA, suggesting that unglycosylated Rem-CT does not reach this BFA-dependent compartment. Treatment with endoglycosidase H indicated that Rem-CT does not traffic through the Golgi apparatus. Analysis of wild-type Rem-CT and its glycosylation mutant by confocal microscopy revealed that both were primarily localized to the ER lumen. A small fraction of wild-type Rem-CT, but not the unglycosylated mutant, was colocalized with Rab5-positive (Rab5+) early endosomes. The expression of a dominant-negative (DN) form of ADP ribosylation factor 1 (Arf1) (containing a mutation of threonine to asparagine at position 31 [T31N]) mimicked the effects of BFA by reducing Rem-CT levels and increased Rem-CT association with early and late endosomes. Inhibition of the AAA ATPase p97/VCP rescued Rem-CT in the presence of BFA or DN Arf1 and prevented localization to Rab5+ endosomes. Thus, Rem-CT uses an unconventional p97-mediated scheme for trafficking to early endosomes. IMPORTANCE Mouse mammary tumor virus is a complex retrovirus that encodes a regulatory/accessory protein, Rem. Rem is a precursor protein that is processed at the endoplasmic reticulum (ER) membrane by signal peptidase. The N-terminal SP uses the p97/VCP ATPase to elude ER-associated degradation to traffic to the nucleus and serve a human immunodeficiency virus Rev-like function. In contrast, the function of the C-terminal glycosylated cleavage product (Rem-CT) is unknown. Since localization is critical for protein function, we used mutants, inhibitors, and confocal microscopy to localize Rem-CT. Surprisingly, Rem-CT, which lacks a transmembrane domain or an ER retention signal, was detected primarily within the ER and required glycosylation and the p97 ATPase for early endosome trafficking without passage through the Golgi apparatus. Thus, Rem-CT uses a novel intracellular trafficking pathway, potentially impacting host antiviral immunity.
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Singh GB, Byun H, Ali AF, Medina F, Wylie D, Shivram H, Nash AK, Lozano MM, Dudley JP. A Protein Antagonist of Activation-Induced Cytidine Deaminase Encoded by a Complex Mouse Retrovirus. mBio 2019; 10:e01678-19. [PMID: 31409681 PMCID: PMC6692512 DOI: 10.1128/mbio.01678-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 07/08/2019] [Indexed: 01/27/2023] Open
Abstract
Complex human-pathogenic retroviruses cause high morbidity and mortality worldwide, but resist antiviral drugs and vaccine development due to evasion of the immune response. A complex retrovirus, mouse mammary tumor virus (MMTV), requires replication in B and T lymphocytes for mammary gland transmission and is antagonized by the innate immune restriction factor murine Apobec3 (mA3). To determine whether the regulatory/accessory protein Rem affects innate responses to MMTV, a splice-donor mutant (MMTV-SD) lacking Rem expression was injected into BALB/c mice. Mammary tumors induced by MMTV-SD had a lower proviral load, lower incidence, and longer latency than mammary tumors induced by wild-type MMTV (MMTV-WT). MMTV-SD proviruses had many G-to-A mutations on the proviral plus strand, but also C-to-T transitions within WRC motifs. Similarly, a lymphomagenic MMTV variant lacking Rem expression showed decreased proviral loads and increased WRC motif mutations relative to those in wild-type-virus-induced tumors, consistent with activation-induced cytidine deaminase (AID) mutagenesis in lymphoid cells. These mutations are typical of the Apobec family member AID, a B-cell-specific mutagenic protein involved in antibody variable region hypermutation. In contrast, mutations in WRC motifs and proviral loads were similar in MMTV-WT and MMTV-SD proviruses from tumors in AID-insufficient mice. AID was not packaged in MMTV virions. Rem coexpression in transfection experiments led to AID proteasomal degradation. Our data suggest that rem specifies a human-pathogenic immunodeficiency virus type 1 (HIV-1) Vif-like protein that inhibits AID and antagonizes innate immunity during MMTV replication in lymphocytes.IMPORTANCE Complex retroviruses, such as human-pathogenic immunodeficiency virus type 1 (HIV-1), cause many human deaths. These retroviruses produce lifelong infections through viral proteins that interfere with host immunity. The complex retrovirus mouse mammary tumor virus (MMTV) allows for studies of host-pathogen interactions not possible in humans. A mutation preventing expression of the MMTV Rem protein in two different MMTV strains decreased proviral loads in tumors and increased viral genome mutations typical of an evolutionarily ancient enzyme, AID. Although the presence of AID generally improves antibody-based immunity, it may contribute to human cancer progression. We observed that coexpression of MMTV Rem and AID led to AID destruction. Our results suggest that Rem is the first known protein inhibitor of AID and that further experiments could lead to new disease treatments.
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Affiliation(s)
- Gurvani B Singh
- Dept. of Molecular Biosciences, LaMontagne Center for Infectious Disease, and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, USA
| | - Hyewon Byun
- Dept. of Molecular Biosciences, LaMontagne Center for Infectious Disease, and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, USA
| | - Almas F Ali
- Dept. of Molecular Biosciences, LaMontagne Center for Infectious Disease, and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, USA
| | - Frank Medina
- Dept. of Molecular Biosciences, LaMontagne Center for Infectious Disease, and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, USA
| | - Dennis Wylie
- Computational Biology and Bioinformatics and Center for Biomedical Research Support, The University of Texas at Austin, Austin, Texas, USA
| | - Haridha Shivram
- Dept. of Molecular Biosciences, LaMontagne Center for Infectious Disease, and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, USA
| | - Andrea K Nash
- Dept. of Molecular Biosciences, LaMontagne Center for Infectious Disease, and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, USA
| | - Mary M Lozano
- Dept. of Molecular Biosciences, LaMontagne Center for Infectious Disease, and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, USA
| | - Jaquelin P Dudley
- Dept. of Molecular Biosciences, LaMontagne Center for Infectious Disease, and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, USA
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Kane M, Case LK, Wang C, Yurkovetskiy L, Dikiy S, Golovkina TV. Innate immune sensing of retroviral infection via Toll-like receptor 7 occurs upon viral entry. Immunity 2011; 35:135-45. [PMID: 21723157 PMCID: PMC3519935 DOI: 10.1016/j.immuni.2011.05.011] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 03/02/2011] [Accepted: 03/30/2011] [Indexed: 12/21/2022]
Abstract
Innate immune sensors are required for induction of pathogen-specific immune responses. Retroviruses are notorious for their ability to evade immune defenses and establish long-term persistence in susceptible hosts. However, some infected animals are able to develop efficient virus-specific immune responses, and thus can be employed for identification of critical innate virus-sensing mechanisms. With mice from two inbred strains that control retroviruses via adaptive immune mechanisms, we found that of all steps in viral replication, the ability to enter the host cell was sufficient to induce antivirus humoral immune responses. Virus sensing occurred in endosomes via a MyD88-Toll-like receptor 7-dependent mechanism and stimulated virus-neutralizing immunity independently of type I interferons. Thus, efficient adaptive immunity to retroviruses is induced in vivo by innate sensing of the early stages of retroviral infection.
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Affiliation(s)
- Melissa Kane
- Department of Microbiology, University of Chicago, 920 E. 58 Street, Chicago, IL 60637, USA
| | - Laure K. Case
- Department of Microbiology, University of Chicago, 920 E. 58 Street, Chicago, IL 60637, USA
| | - Christine Wang
- Department of Microbiology, University of Chicago, 920 E. 58 Street, Chicago, IL 60637, USA
| | - Leonid Yurkovetskiy
- Department of Microbiology, University of Chicago, 920 E. 58 Street, Chicago, IL 60637, USA
| | - Stanislav Dikiy
- Department of Microbiology, University of Chicago, 920 E. 58 Street, Chicago, IL 60637, USA
| | - Tatyana V. Golovkina
- Department of Microbiology, University of Chicago, 920 E. 58 Street, Chicago, IL 60637, USA
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Animal models of breast cancer for the study of pathogenesis and therapeutic insights. Clin Transl Oncol 2010; 11:721-7. [PMID: 19917535 DOI: 10.1007/s12094-009-0434-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Activation of oncogenes and inactivation of tumour suppressor genes are common events during breast cancer initiation and progression and often determine treatment responsiveness. Indeed, these events need to be recreated in in vitro systems and in mouse cancer models in order to unravel the molecular mechanisms involved in breast cancer initiation and metastasis and assess their possible impact on responses to anticancer drugs. Optical-based imaging models are used to investigate and to follow important tumour progression processes. Moreover, the development of novel anticancer strategies requires more sensitive and less invasive methods to detect and monitor in vivo drug responses in breast cancer models. This review highlights some of the current strategies for modelling breast cancer in vitro and in the mouse, in order to answer biological or translational questions about human breast malignancies.
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Mertz JA, Lozano MM, Dudley JP. Rev and Rex proteins of human complex retroviruses function with the MMTV Rem-responsive element. Retrovirology 2009; 6:10. [PMID: 19192308 PMCID: PMC2661877 DOI: 10.1186/1742-4690-6-10] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Accepted: 02/03/2009] [Indexed: 11/11/2022] Open
Abstract
Background Mouse mammary tumor virus (MMTV) encodes the Rem protein, an HIV Rev-like protein that enhances nuclear export of unspliced viral RNA in rodent cells. We have shown that Rem is expressed from a doubly spliced RNA, typical of complex retroviruses. Several recent reports indicate that MMTV can infect human cells, suggesting that MMTV might interact with human retroviruses, such as human immunodeficiency virus (HIV), human T-cell leukemia virus (HTLV), and human endogenous retrovirus type K (HERV-K). In this report, we test whether the export/regulatory proteins of human complex retroviruses will increase expression from vectors containing the Rem-responsive element (RmRE). Results MMTV Rem, HIV Rev, and HTLV Rex proteins, but not HERV-K Rec, enhanced expression from an MMTV-based reporter plasmid in human T cells, and this activity was dependent on the RmRE. No RmRE-dependent reporter gene expression was detectable using Rev, Rex, or Rec in HC11 mouse mammary cells. Cell fractionation and RNA quantitation experiments suggested that the regulatory proteins did not affect RNA stability or nuclear export in the MMTV reporter system. Rem had no demonstrable activity on export elements from HIV, HTLV, or HERV-K. Similar to the Rem-specific activity in rodent cells, the RmRE-dependent functions of Rem, Rev, or Rex in human cells were inhibited by a dominant-negative truncated nucleoporin that acts in the Crm1 pathway of RNA and protein export. Conclusion These data argue that many retroviral regulatory proteins recognize similar complex RNA structures, which may depend on the presence of cell-type specific proteins. Retroviral protein activity on the RmRE appears to affect a post-export function of the reporter RNA. Our results provide additional evidence that MMTV is a complex retrovirus with the potential for viral interactions in human cells.
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Affiliation(s)
- Jennifer A Mertz
- Section of Molecular Genetics and Microbiology and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, USA.
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Courreges MC, Burzyn D, Nepomnaschy I, Piazzon I, Ross SR. Critical role of dendritic cells in mouse mammary tumor virus in vivo infection. J Virol 2007; 81:3769-77. [PMID: 17267484 PMCID: PMC1866091 DOI: 10.1128/jvi.02728-06] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Mouse mammary tumor virus (MMTV) is a milk-transmitted betaretrovirus that causes mammary tumors in mice. Although mammary epithelial cells are the ultimate targets of MMTV, the virus utilizes components of the host immune system to establish infection. Previous studies indicated that dendritic cells play a role in MMTV infection. Here we show that dendritic cells are the first cells to be infected by MMTV in vivo and that they are capable of producing infectious virus that can be transmitted to other cell types. Moreover, upon contact with the virus, dendritic cells became more mature and migrated in response to the chemokine macrophage inflammatory protein 3beta. Finally, we demonstrate that targeted ablation of dendritic cells in vivo dramatically attenuated MMTV infection. These data indicate that MMTV infection of dendritic cells is critical to initial propagation of the virus in vivo.
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Affiliation(s)
- Maria Cecilia Courreges
- Department of Microbiology and Abramson Family Cancer Center, University of Pennsylvania, 313 BRBII/III, 421 Curie Blvd., Philadelphia, PA 19104-6142, USA
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Okeoma CM, Lovsin N, Peterlin BM, Ross SR. APOBEC3 inhibits mouse mammary tumour virus replication in vivo. Nature 2007; 445:927-30. [PMID: 17259974 DOI: 10.1038/nature05540] [Citation(s) in RCA: 156] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Accepted: 12/19/2006] [Indexed: 11/09/2022]
Abstract
Genomes of all mammals encode apobec3 genes, which are thought to have a function in intrinsic cellular immunity to several viruses including human immunodeficiency virus type 1 (HIV-1). APOBEC3 (A3) proteins are packaged into virions and inhibit retroviral replication in newly infected cells, at least in part by deaminating cytidines on the negative strand DNA intermediates. However, the role of A3 in innate resistance to mouse retroviruses is not understood. Here we show that A3 functions during retroviral infection in vivo and provides partial protection to mice against infection with mouse mammary tumour virus (MMTV). Both mouse A3 and human A3G proteins interacted with the MMTV nucleocapsid in an RNA-dependent fashion and were packaged into virions. In addition, mouse A3-containing and human A3G-containing virions showed a marked decrease in titre. Last, A3(-/-) mice were more susceptible to MMTV infection, because virus spread was more rapid and extensive than in their wild-type littermates.
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Affiliation(s)
- Chioma M Okeoma
- Department of Microbiology and Abramson Family Cancer Center, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6142, USA
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Szabo S, Haislip AM, Traina-Dorge V, Costin JM, Crawford BE, Wilson RB, Garry RF. Human, rhesus macaque, and feline sequences highly similar to mouse mammary tumor virus sequences. Microsc Res Tech 2005; 68:209-21. [PMID: 16276510 DOI: 10.1002/jemt.20233] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Sequences highly similar (>95%) to the mouse mammary tumor virus (MMTV) env gene have been amplified from human DNA samples, including DNA samples from patients with breast cancer (BC) and persons who did not have BC. The sequences from human DNA were distinct from the MMTV sequences used as controls in these PCR reactions, indicating that these results are not simply due to contamination. In addition to both, mouse and human-related sequences were also amplified from some monkey and cat genomic DNA samples. These products were shown to be distinct from, but highly related to, the MMTV env gene, whereas, testing of other sources (lambda phage, snake, cockroach, sea urchin, chicken, or dog) demonstrated no specific amplification. A sequence 90% similar to the MMTV group antigen gene (gag) was amplified from cat DNA. These results indicate that DNA from vertebrate species other than rodents, including some but not all humans, monkeys, and cats, can contain sequences closely related to MMTV.
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Affiliation(s)
- Sara Szabo
- Department of Pathology, Children's Hospital, New Orleans, Louisiana 70118, USA.
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Christensen T. Association of human endogenous retroviruses with multiple sclerosis and possible interactions with herpes viruses. Rev Med Virol 2005; 15:179-211. [PMID: 15782388 DOI: 10.1002/rmv.465] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The hypothesis that human endogenous retroviruses (HERVs) play a role in autoimmune diseases is subject to increasing attention. HERVs represent both putative susceptibility genes and putative pathogenic viruses in the immune-mediated neurological disease multiple sclerosis (MS). Gammaretroviral HERV sequences are found in reverse transcriptase-positive virions produced by cultured mononuclear cells from MS patients, and they have been isolated from MS samples of plasma, serum and CSF, and characterised to some extent at the nucleotide, protein/enzyme, virion and immunogenic level. Two types of sequences, HERV-H and HERV-W, have been reported. No known HERV-H or HERV-W copy contains complete ORFs in all prerequisite genes, although several copies have coding potential, and several such sequences are specifically activated in MS, apparently resulting in the production of complete, competent virions. Increased antibody reactivity to specific Gammaretroviral HERV epitopes is found in MS serum and CSF, and cell-mediated immune responses have also been reported. Further, HERV-encoded proteins can have neuropathogenic effects. The activating factor(s) in the process resulting in protein or virion production may be members of the Herpesviridae. Several herpes viruses, such as HSV-1, VZV, EBV and HHV-6, have been associated with MS pathogenesis, and retroviruses and herpes viruses have complex interactions. The current understanding of HERVs, and specifically the investigations of HERV activation and expression in MS are the major subjects of this review, which also proposes to synergise the herpes and HERV findings, and presents several possible pathogenic mechanisms for HERVs in MS.
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Affiliation(s)
- Tove Christensen
- Institute of Medical Microbiology and Immunology, Bartholin Building, University of Aarhus, DK-8000 Aarhus C, Denmark.
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Szabo S, Haislip AM, Garry RF. Of mice, cats, and men: Is human breast cancer a Zoonosis? Microsc Res Tech 2005; 68:197-208. [PMID: 16276516 DOI: 10.1002/jemt.20232] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Mouse mammary tumor virus (MMTV), a member of the betaretroviridae, is the most common cause of breast cancer (BC) in mice. MMTV is transmitted in mice both in the germline as endogenous proviruses and exogenously as infectious virions. Here, we review a variety of evidence accumulated for six decades that has suggested that a human homologue of MMTV may exist. The findings include recent studies from several independent laboratories that have detected sequences very closely related to MMTV in DNA isolated from human BC tumors. Other laboratories, however, have failed to detect the MMTV-related sequences in human DNA samples, and conclusive evidence for a human mammary tumor virus has been elusive. We also reviewed additional studies, suggesting that betaretroviruses are present in a much wider range of species than previously known, including rodents, felines, and primates. The observation that a subset of cats may be infected with a close homologue of MMTV may be of epidemiological significance for human BC. Cats may become infected by MMTV from mice, and in turn may transmit the virus to humans, possibly after selection for variants with an expanded host range.
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Affiliation(s)
- Sara Szabo
- Department of Pathology, Children's Hospital, New Orleans, Louisiana 70118, USA.
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Selmi C, Ross SR, Ansari AA, Invernizzi P, Podda M, Coppel RL, Gershwin ME. Lack of immunological or molecular evidence for a role of mouse mammary tumor retrovirus in primary biliary cirrhosis. Gastroenterology 2004; 127:493-501. [PMID: 15300582 DOI: 10.1053/j.gastro.2004.05.033] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
BACKGROUND & AIMS Recent observations, including a pilot clinical trial, have suggested that a human mouse mammary tumor virus (MMTV) causes primary biliary cirrhosis (PBC). We attempted to confirm such data. METHODS We obtained sera from 101 patients (53 with PBC and 48 controls), fixed liver sections from 10 patients (8 PBC and 2 controls), fresh liver specimens (6 PBC and 6 controls), and fresh peripheral blood lymphocytes (PBLs) (10 PBC and 10 controls). We studied sera for reactivities against 3 different strains of MMTV virions, MMTV(C3H), MMTV(FM), and MMTV(LA), including goat polyclonal antibodies against MMTV virions, gp52, and p27 as positive controls. We stained liver specimens using polyclonal antibodies against MMTV and gp52 and further examined tissue samples and PBLs for specific MMTV genome sequences. RESULTS By Western blot analysis, no detectable reactivity in any of the PBC sera against any of the 3 MMTV strains or MMTV gp52 or p27 was observed. However, viral proteins were recognized by our control positive polyclonal antibodies. We note that 13%-60% of PBC sera presented low reactivity against 2 proteins of approximately 57 and 74 kilodaltons. Such reactivity is related to the trace amounts of mitochondrial antigens in the virus preparations derived from murine mammary tumor tissue. No detectable immunohistochemical or molecular evidence for MMTV was found in the liver specimens or PBLs. CONCLUSIONS We were unable to recapitulate the data on this specific retroviral etiology of PBC and suggest that such data could be the result of contamination.
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Affiliation(s)
- Carlo Selmi
- Division of Rheumatology, Allergy, and Clinical Immunology, University of California at Davis, 95616, USA
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15
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Jude BA, Pobezinskaya Y, Bishop J, Parke S, Medzhitov RM, Chervonsky AV, Golovkina TV. Subversion of the innate immune system by a retrovirus. Nat Immunol 2003; 4:573-8. [PMID: 12730691 DOI: 10.1038/ni926] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2003] [Accepted: 03/12/2003] [Indexed: 01/25/2023]
Abstract
Retroviruses evolve rapidly to avoid the immune response of the infected host. We show here that the wild-type mouse mammary tumor virus MMTV(C3H) persisted indefinitely in C3H/HeN mice. However, it was rapidly lost in mice of the closely related C3H/HeJ strain and was replaced by a virus recombinant with an endogenous Mtv provirus. Maintenance of the wild-type virus was dependent on Toll-like receptor-4 (TLR4) signaling, which triggered production of the immunosuppressive cytokine interleukin-10. In the presence of mutant TLR4 in C3H/HeJ mice, wild-type virus was eliminated by the cytotoxic immune response, promoting selection of the immune escape recombinant MMTV variants. Thus, subversion of the innate immune system is yet another survival strategy used by retroviruses.
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Affiliation(s)
- Brooke A Jude
- The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609, USA
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16
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Christensen T, Pedersen L, Sørensen PD, Møller-Larsen A. A transmissible human endogenous retrovirus. AIDS Res Hum Retroviruses 2002; 18:861-6. [PMID: 12201909 DOI: 10.1089/08892220260190344] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The transmissibility of the human endogenous retrovirus HERV-H/RGH-2 was investigated by marker rescue: intraspecies transmission of HERV-H/RGH-2 retrovirus particles was attempted by cocultivation of virion-producing, long-term cell cultures spontaneously formed from peripheral blood mononuclear cells from several multiple sclerosis patient cultures with a retroviral vector construct-harboring cell line. Transmissibility was assessed by assays for productive infection (reverse transcriptase activity), and assays for rescue of the retroviral vector construct in indicator cells. Our studies show that the human endogenous retrovirus HERV-H/RGH-2 is transmissible, albeit at a very low level. The human endogenous retrovirus HERV-H/RGH-2 is associated with multiple sclerosis (MS). Previously, we demonstrated sequence variants of the human endogenous retrovirus HERV-H family in virion form, by applying RT-PCR to virion RNA from the supernatants of long-term MS cell cultures, and to the particulate fraction of a series of MS patient plasma samples.
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Affiliation(s)
- Tove Christensen
- Department of Medical Microbiology and Immunology, University of Aarhus, DK-8000 Aarhus C, Denmark.
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17
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Abstract
We usually think of superantigens (SAg) as dangerous toxins that may cause toxic shock syndrome and death. Now, based on two papers in this issue of Immunity, it seems that we all have SAg genes within us, lying dormant and waiting to be activated under special circumstances.
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Affiliation(s)
- D N Posnett
- Department of Medicine, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA.
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18
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Mustafa F, Lozano M, Dudley JP. C3H mouse mammary tumor virus superantigen function requires a splice donor site in the envelope gene. J Virol 2000; 74:9431-40. [PMID: 11000212 PMCID: PMC112372 DOI: 10.1128/jvi.74.20.9431-9440.2000] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Mouse mammary tumor virus (MMTV) encodes a superantigen (Sag) that is required for efficient milk-borne transmission of virus from mothers to offspring. The mRNA used for Sag expression is controversial, and at least four different promoters (two in the long terminal repeat and two in the envelope gene) for sag mRNA have been reported. To determine which RNA is responsible for Sag function during milk-borne MMTV transmission, we mutated a splice donor site unique to a spliced sag RNA from the 5' envelope promoter. The splice donor mutation in an infectious provirus was transfected into XC cells and injected into BALB/c mice. Mice injected with wild-type provirus showed Sag activity by the deletion of Sag-specific T cells and induction of mammary tumors in 100% of injected animals. However, mice injected with the splice donor mutant gave sporadic and delayed T-cell deletion and a low percentage of mammary tumors with a long latency, suggesting that the resulting tumors were due to the generation of recombinants with endogenous MMTVs. Third-litter offspring of mice injected with wild-type provirus showed Sag-specific T-cell deletion and developed mammary tumors with kinetics similar to those for mice infected by nursing on MMTV-infected mothers, whereas the third-litter offspring of the splice donor mutant-injected mice did not. One of the fifth-litter progeny of splice donor mutant-injected mice showed C3H Sag activity and had recombinants that repaired the splice donor mutation, thus confirming the necessity for the splice donor site for Sag function. These experiments are the first to show that the spliced sag mRNA from the 5' envelope promoter is required for efficient milk-borne transmission of C3H MMTV.
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Affiliation(s)
- F Mustafa
- Section of Molecular Genetics and Microbiology and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78705, USA
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19
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Abstract
It is clear that there is genetic variation among different individuals in their susceptibility to infection by viruses and other pathogens. Identification of the genes involved in conferring resistance or susceptibility to viral infection will allow us to understand both mechanisms of infection and pathogenesis and to develop reagents for treating or preventing them. Because of the large number of genetically well-characterized inbred mouse strains and the ability to generate targeted germ line mutations, this species is particularly well-suited for such analysis. This review focuses on how the use of genetics to study the retrovirus mouse mammary tumor virus allowed the dissection of both the viral infection pathway and the response of the host to this infection.
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Affiliation(s)
- S R Ross
- Department of Microbiology, University of Pennsylvania, 421 Curie Blvd., Philadelphia, PA 19104-6142, USA
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20
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Dzuris JL, Zhu W, Kapkov D, Golovkina TV, Ross SR. Expression of mouse mammary tumor virus envelope protein does not prevent superinfection in vivo or in vitro. Virology 1999; 263:418-26. [PMID: 10544114 DOI: 10.1006/viro.1999.9967] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Inbred mice expressing endogenous mouse mammary tumor virus envelope proteins can be infected with exogenous virus, and the mammary tumors that develop in these mice usually have many proviruses integrated in their genomes, indicating that this virus is not subject to receptor interference. We show here that transgenic mice expressing an exogenous mouse mammary tumor virus (C3H) envelope protein can still be infected with this virus. Moreover, cultured mammary gland cells expressing the mouse mammary tumor virus (C3H) envelope protein can be superinfected with pseudotyped viruses bearing that same protein. Thus cellular expression of the mouse mammary tumor virus envelope protein does not block superinfection in vivo or in vitro.
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MESH Headings
- Animals
- Blotting, Western
- Cell Line
- DNA, Viral/analysis
- DNA, Viral/genetics
- Female
- Mammary Glands, Animal/cytology
- Mammary Glands, Animal/metabolism
- Mammary Glands, Animal/pathology
- Mammary Neoplasms, Experimental/metabolism
- Mammary Neoplasms, Experimental/virology
- Mammary Tumor Virus, Mouse/genetics
- Mammary Tumor Virus, Mouse/metabolism
- Mice
- Mice, Inbred C3H
- Mice, Transgenic
- Proviruses/genetics
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Retroviridae Infections/metabolism
- Retroviridae Infections/virology
- Superinfection/metabolism
- Superinfection/virology
- Transfection
- Transgenes/genetics
- Transgenes/physiology
- Tumor Virus Infections/metabolism
- Tumor Virus Infections/virology
- Viral Envelope Proteins/genetics
- Viral Envelope Proteins/metabolism
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Affiliation(s)
- J L Dzuris
- Department of Microbiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6148, USA
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21
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Abstract
Superantigens (SAGs) are a class of immunostimulatory and disease-causing proteins of bacterial or viral origin with the ability to activate large fractions (5-20%) of the T cell population. Activation requires simultaneous interaction of the SAG with the V beta domain of the T cell receptor (TCR) and with major histocompatibility complex (MHC) class II molecules on the surface of an antigen-presenting cell. Recent advances in knowledge of the three-dimensional structure of bacterial SAGs, and of their complexes with MHC class II molecules and the TCR beta chain, provide a framework for understanding the molecular basis of T cell activation by these potent mitogens. These structures along with those of TCR-peptide/MHC complexes reveal how SAGs circumvent the normal mechanism for T cell activation by peptide/MHC and how they stimulate T cells expressing TCR beta chains from a number of different families, resulting in polyclonal T cell activation. The crystal structures also provide insights into the basis for the specificity of different SAGs for particular TCR beta chains, and for the observed influence of the TCR alpha chain on SAG reactivity. These studies open the way to the design of SAG variants with altered binding properties for TCR and MHC for use as tools in dissecting structure-activity relationships in this system.
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MESH Headings
- Amino Acid Sequence
- Animals
- Autoimmune Diseases/immunology
- Foodborne Diseases/immunology
- Histocompatibility Antigens Class II/chemistry
- Histocompatibility Antigens Class II/metabolism
- Humans
- Immunotherapy
- Kinetics
- Lymphocyte Activation/physiology
- Macromolecular Substances
- Models, Molecular
- Molecular Sequence Data
- Protein Conformation
- Receptors, Antigen, T-Cell, alpha-beta/chemistry
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/metabolism
- Shock, Septic/immunology
- Superantigens/administration & dosage
- Superantigens/chemistry
- Superantigens/metabolism
- T-Lymphocytes/immunology
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Affiliation(s)
- H Li
- Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, Rockville 20850, USA
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22
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Acha-Orbea H, Finke D, Attinger A, Schmid S, Wehrli N, Vacheron S, Xenarios I, Scarpellino L, Toellner KM, MacLennan IC, Luther SA. Interplays between mouse mammary tumor virus and the cellular and humoral immune response. Immunol Rev 1999; 168:287-303. [PMID: 10399081 DOI: 10.1111/j.1600-065x.1999.tb01299.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Mouse mammary tumor virus has developed strategies to exploit the immune response. It requires vigorous immune stimulation to achieve efficient infection. The infected antigen-presenting cells present a viral superantigen on the cell surface which stimulates strong CD4-mediated T-cell help but CD8 T-cell responses are undetectable. Despite the high frequency of superantigen-reactive T cells, the superantigen-induced immune response is comparable to classical antigen responses in terms of T-cell priming, T-cell-B-cell collaboration as well as follicular and extra-follicular B-cell differentiation. Induction of systemic anergy is observed, similar to classical antigen responses where antigen is administered systemically but does not influence the role of the superantigen-reactive T cells in the maintenance of the chronic germinal center reaction. So far we have been unable to detect a cytotoxic T-cell response to mouse mammary tumor virus peptide antigens or to the superantigen. This might yet represent another step in the viral infection strategy.
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Affiliation(s)
- H Acha-Orbea
- Ludwing Institute of Cancer Research, Lausanne Branch, University of Lausanne, Epalinges, Switzerland.
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23
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Golovkina TV, Dudley JP, Ross SR. B and T Cells Are Required for Mouse Mammary Tumor Virus Spread Within the Mammary Gland. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.161.5.2375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
Mouse mammary tumor virus (MMTV) is an infectious retrovirus transmitted through milk from mother to newborns. MMTV encodes a superantigen (SAg) whose activity is indispensable for the virus life cycle, since a genetically engineered virus with a mutation in the sag gene neither amplified in cells of the immune system of suckling pups nor infected their mammary glands. When wild-type MMTV was injected directly into the mammary glands of uninfected pubescent mice, their lymphoid as well as mammary gland cells became virus infected. To test whether this infection of lymphoid cells was dependent on SAg activity and required for virus spread within the mammary gland, we performed mammary gland injections of wild-type MMTV(C3H) into two strains of transgenic mice that lacked SAg-cognate, Vβ14+ T cells. Neither the MTV-ORF or LEL strains showed infection of their mammary glands. Moreover, no MMTV infection of their peripheral lymphocytes was detected. Similar experiments with mice lacking B cells (μ-chain knockouts) showed no detectable virus spread in the mammary glands or lymphoid tissues. These data suggest that SAg activity and MMTV-infected lymphocytes are required, not only for initial steps of viral infection, but also for virus spread within the mammary gland. Virus spread at late times in infection determines whether MMTV induces mammary tumors.
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Affiliation(s)
- Tatyana V. Golovkina
- *Department of Microbiology/Cancer Center, University of Pennsylvania School of Medicine, Philadelphia, PA 19104; and
| | | | - Susan R. Ross
- *Department of Microbiology/Cancer Center, University of Pennsylvania School of Medicine, Philadelphia, PA 19104; and
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24
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Wrona TJ, Lozano M, Binhazim AA, Dudley JP. Mutational and functional analysis of the C-terminal region of the C3H mouse mammary tumor virus superantigen. J Virol 1998; 72:4746-55. [PMID: 9573239 PMCID: PMC110007 DOI: 10.1128/jvi.72.6.4746-4755.1998] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The mouse mammary tumor virus (MMTV) encodes within the U3 region of the long terminal repeat (LTR) a protein known as the superantigen (Sag). Sag is needed for the efficient transmission of milk-borne virus from the gut to target tissue in the mammary gland. MMTV-infected B cells in the gut express Sag as a type II transmembrane protein that is recognized by the variable region of particular beta chains (Vbeta) of the T-cell receptor (TCR) on the surface of T cells. Recognition of Sag by particular TCRs results in T-cell stimulation, release of cytokines, and amplification of MMTV infection in lymphoid cells that are needed for infection of adolescent mammary tissue. Because the C-terminal 30 to 40 amino acids of Sag are variable and correlate with recognition of particular TCR Vbeta chains, we prepared a series of C-terminal Sag mutations that were introduced into a cloned infectious MMTV provirus. Virus-producing XC rat cells were used for injection of susceptible BALB/c mice, and these mice were monitored for functional Sag activity by the deletion of C3H MMTV Sag-reactive (CD4+ Vbeta14+) T cells. Injected mice also were analyzed for mutant infection and tumor formation in mammary glands as well as milk-borne transmission of MMTV to offspring. Most mutations abrogated Sag function, although one mutation (HPA242) that changed the negative charge of the extreme C terminus to a positive charge created a weaker Sag that slowed the kinetics of Sag-mediated T-cell deletion. Despite the lack of Sag activity, many of the sag mutant viruses were capable of sporadic infections of the mammary glands of injected mice but not of offspring mice, indicating that functional Sag increases the probability of milk-borne MMTV infection. Furthermore, although most viruses encoding nonfunctional Sags were unable to cause mammary tumors, tumors were induced by such viruses carrying mutations in a negative regulatory element that overlaps the sag gene within the LTR, suggesting that loss of Sag function may be compensated, at least partially, by loss of transcriptional suppression in certain tissues. Together these results confirm the importance of Sag for efficient milk-borne transmission and indicate that the entire C-terminal region is needed for complete Sag function.
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MESH Headings
- Amino Acid Sequence
- Animals
- DNA Mutational Analysis
- DNA, Viral/genetics
- Female
- Genes, Viral
- Mammary Tumor Virus, Mouse/genetics
- Mammary Tumor Virus, Mouse/immunology
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C3H
- Molecular Sequence Data
- Mutation
- Rats
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/immunology
- Retroviridae Infections/immunology
- Retroviridae Infections/virology
- Sequence Alignment
- Superantigens/genetics
- Superantigens/immunology
- Tumor Virus Infections/immunology
- Tumor Virus Infections/virology
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Affiliation(s)
- T J Wrona
- Department of Microbiology and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
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25
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Abstract
Mouse mammary tumor virus (MMTV) infected both B and T tissue culture cells and primary B and T cells in vivo after milk-borne transmission of the virus. The infected tissue culture cells processed viral proteins, and both these and primary B and T cells shed virus when cultured in vitro. Moreover, the infected B and T tissue culture cells transmitted virus to uninfected mammary gland cells in vitro. The level of infection of these different cell types in vivo was dependent on the strain of mouse, with C3H/HeN mice showing greater B-cell infection and BALB/c mice greater T-cell infection after nursing on MMTV-infected C3H/HeN mothers. Although their B cells were less infected, BALB/c mice developed tumors more rapidly than C3H/HeN mice. These results indicate that both infected T and B cells are potential carriers of MMTV in vivo.
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Affiliation(s)
- J L Dzuris
- Department of Microbiology/Cancer Center, University of Pennsylvania School of Medicine, Philadelphia 19103-6142, USA
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26
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Golovkina TV, Piazzon I, Nepomnaschy I, Buggiano V, de Olano Vela M, Ross SR. Generation of a tumorigenic milk-borne mouse mammary tumor virus by recombination between endogenous and exogenous viruses. J Virol 1997; 71:3895-903. [PMID: 9094666 PMCID: PMC191541 DOI: 10.1128/jvi.71.5.3895-3903.1997] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Two novel exogenous mouse mammary tumor viruses (MMTV), BALB2 and BALB14, that encode superantigens (Sags) with Vbeta2+ and Vbeta14+ specificities, respectively, were found in the BALB/cT mouse strain. BALB/cT females were crossed with AKR/J males to generate F1 females. Foster nursing of BALB/cT mice on (BALB/cT x AKR/J)F1 mothers resulted in the generation of a new mouse strain, BALB/cLA, that had acquired a new exogenous MMTV (hereafter called LA) with a Vbeta6+/Vbeta8.1+-T-cell-specific Sag. Sequence analysis of the long terminal repeats of the BALB2, BALB14, and LA viruses indicated that LA virus resulted from recombination between BALB14 and the endogenous Mtv-7 provirus. Mtv-7 is expressed only in lymphoid tissues but not the mammary glands of Mtv-7-containing mouse strains such as AKR. In contrast, LA virus was highly expressed in the mammary gland, although it had the sag-specific region from Mtv-7. The LA virus, as well as different recombinant viruses expressed in the mammary glands of (BALB/cT x AKR/J)F1 mice, acquired a specific DNA sequence from BALB14 virus that is required for the mammary-gland-specific expression of MMTV. Since the Sag encoded by LA virus strongly stimulated cognate T cells in vivo, selection for recombinant virus with the Mtv-7 sag most likely occurred because the increased T-cell proliferation resulted in greater lymphoid and mammary gland cell infection. As a result of the higher virus titer, 80% of BALB/cLA females developed mammary gland tumors, although the incidence was only 40% in BALB/cT mice.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Female
- Male
- Mammary Neoplasms, Experimental/etiology
- Mammary Tumor Virus, Mouse/genetics
- Mice
- Mice, Inbred AKR
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Milk/virology
- Molecular Sequence Data
- Receptors, Antigen, T-Cell, alpha-beta/analysis
- Recombination, Genetic
- Repetitive Sequences, Nucleic Acid
- Superantigens/chemistry
- Superantigens/genetics
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Affiliation(s)
- T V Golovkina
- Department of Microbiology/Cancer Center, University of Pennsylvania, Philadelphia 19104-6142, USA
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27
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Delcourt M, Thibodeau J, Denis F, Sekaly RP. Paracrine transfer of mouse mammary tumor virus superantigen. J Exp Med 1997; 185:471-80. [PMID: 9053447 PMCID: PMC2196028 DOI: 10.1084/jem.185.3.471] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Transfer of vSAG7, the endogenous superantigen encoded in the Mtv7 locus, from MHC class II to MHC class II+ cells has been suggested to occur both in vivo and in vitro. This transfer usually leads to the activation and deletion of T cells expressing responsive V beta s. However, there is no direct molecular evidence for such a transfer. We have developed an in vitro system which confirms this property of vSAGs. vSAG7 was transfected into a class II murine fibroblastic line. Coculture of these cells with class II+ cells and murine T cell hybridomas expressing the specific V beta s led to high levels of IL-2 production which was specifically inhibited by vSAG7- and MHC class II-specific mAbs. Moreover, injection of vSAG7+ class II+ cells in mice led to expansion of V beta 6+ CD4+ cells. We show that this transfer activity is paracrine but does not require cell-to-cell contact. Indeed, vSAG7 was transferred across semi-permeable membranes. Transfer can occur both from class II+ and class II+ cells, indicating that MHC class II does not sequester vSAG7. Finally, competition experiments using bacterial toxins with well defined binding sites showed that the transferred vSAG7 fragment binds to the alpha 1 domain of HLA-DR.
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Affiliation(s)
- M Delcourt
- Laboratoire d'Immunologie Institut de Recherches Cliniques de Montréal, Canada
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28
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Affiliation(s)
- L P Villarreal
- Center for Viral Vector Design, Department of Molecular Biology and Biochemistry, University of California, Irvine 92697, USA.
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29
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Mouse Mammary Tumor Virus: Immunological Interplays between Virus and Host **This article was accepted for publication on 1 October 1996. Adv Immunol 1997. [DOI: 10.1016/s0065-2776(08)60743-9] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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30
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Abstract
Superantigens of mouse mammary tumor virus induce a strong cognate interaction between T cells and B cells. In addition to amplifying the virus-infected B-cell pool, this superantigen-driven interaction leads to the differentiation of virus-specific B cells into plasma cells. Successful interaction between T cells and B cells is required for completion of the viral life cycle.
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Affiliation(s)
- S A Luther
- Ludwig Institute of Cancer Research, Lausanne Branch, University of Lausanne, Chemin des Boveresses 155, CH-1066 Epalinges, Switzerland.
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31
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Wrona T, Dudley JP. Major histocompatibility complex class II I-E-independent transmission of C3H mouse mammary tumor virus. J Virol 1996; 70:1246-9. [PMID: 8551589 PMCID: PMC189937 DOI: 10.1128/jvi.70.2.1246-1249.1996] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
C57BL/6 mice are resistant to C3H mouse mammary tumor virus (MMTV)-induced mammary tumorigenesis and lack major histocompatibility complex class II I-E molecules that are essential for presentation of C3H superantigen to T cells. T cells are needed for transmission of milk-borne MMTV from the gut to the mammary gland. In this report, we show that infectious C3H MMTV is produced by C57BL/6 mice that nurse on C3H mothers but that virus production in the mammary gland is delayed compared with that in I-E+ mouse strains.
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Affiliation(s)
- T Wrona
- Department of Microbiology, University of Texas at Austin 78712, USA
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