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Sajiki Y, Konnai S, Okagawa T, Nishimori A, Maekawa N, Goto S, Watari K, Minato E, Kobayashi A, Kohara J, Yamada S, Kaneko MK, Kato Y, Takahashi H, Terasaki N, Takeda A, Yamamoto K, Toda M, Suzuki Y, Murata S, Ohashi K. Prostaglandin E 2-Induced Immune Exhaustion and Enhancement of Antiviral Effects by Anti-PD-L1 Antibody Combined with COX-2 Inhibitor in Bovine Leukemia Virus Infection. THE JOURNAL OF IMMUNOLOGY 2019; 203:1313-1324. [PMID: 31366713 DOI: 10.4049/jimmunol.1900342] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 06/28/2019] [Indexed: 01/09/2023]
Abstract
Bovine leukemia virus (BLV) infection is a chronic viral infection of cattle and endemic in many countries, including Japan. Our previous study demonstrated that PGE2, a product of cyclooxygenase (COX) 2, suppresses Th1 responses in cattle and contributes to the progression of Johne disease, a chronic bacterial infection in cattle. However, little information is available on the association of PGE2 with chronic viral infection. Thus, we analyzed the changes in plasma PGE2 concentration during BLV infection and its effects on proviral load, viral gene transcription, Th1 responses, and disease progression. Both COX2 expression by PBMCs and plasma PGE2 concentration were higher in the infected cattle compared with uninfected cattle, and plasma PGE2 concentration was positively correlated with the proviral load. BLV Ag exposure also directly enhanced PGE2 production by PBMCs. Transcription of BLV genes was activated via PGE2 receptors EP2 and EP4, further suggesting that PGE2 contributes to disease progression. In contrast, inhibition of PGE2 production using a COX-2 inhibitor activated BLV-specific Th1 responses in vitro, as evidenced by enhanced T cell proliferation and Th1 cytokine production, and reduced BLV proviral load in vivo. Combined treatment with the COX-2 inhibitor meloxicam and anti-programmed death-ligand 1 Ab significantly reduced the BLV proviral load, suggesting a potential as a novel control method against BLV infection. Further studies using a larger number of animals are required to support the efficacy of this treatment for clinical application.
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Affiliation(s)
- Yamato Sajiki
- Department of Disease Control, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
| | - Satoru Konnai
- Department of Disease Control, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan; .,Department of Advanced Pharmaceutics, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
| | - Tomohiro Okagawa
- Department of Advanced Pharmaceutics, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
| | - Asami Nishimori
- Department of Disease Control, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
| | - Naoya Maekawa
- Department of Advanced Pharmaceutics, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
| | - Shinya Goto
- Department of Disease Control, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
| | - Kei Watari
- Department of Disease Control, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
| | - Erina Minato
- Department of Veterinary Clinical Medicine, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
| | - Atsushi Kobayashi
- Department of Veterinary Clinical Medicine, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
| | - Junko Kohara
- Animal Research Center, Agriculture Research Department, Hokkaido Research Organization, Shintoku 081-0038, Japan
| | - Shinji Yamada
- Department of Antibody Drug Development, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan
| | - Mika K Kaneko
- Department of Antibody Drug Development, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan
| | - Yukinari Kato
- Department of Antibody Drug Development, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan
| | - Hirofumi Takahashi
- Shibecha Branch, Kushiro Central Office, Hokkaido Higashi Agricultural Mutual Aid Association, Shibecha 088-2311, Japan
| | - Nobuhiro Terasaki
- Shibecha Branch, Kushiro Central Office, Hokkaido Higashi Agricultural Mutual Aid Association, Shibecha 088-2311, Japan
| | - Akira Takeda
- Shibecha Branch, Kushiro Central Office, Hokkaido Higashi Agricultural Mutual Aid Association, Shibecha 088-2311, Japan
| | - Keiichi Yamamoto
- Department of Advanced Pharmaceutics, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.,Research and Development Center, Fuso Pharmaceutical Industries, Ltd., Osaka 536-8523, Japan
| | - Mikihiro Toda
- Department of Advanced Pharmaceutics, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.,New Business and International Business Development, Fuso Pharmaceutical Industries, Ltd., Osaka 536-8523, Japan
| | - Yasuhiko Suzuki
- Department of Advanced Pharmaceutics, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.,Division of Bioresources, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0019, Japan; and.,Global Station for Zoonosis Control, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo 001-0019, Japan
| | - Shiro Murata
- Department of Disease Control, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.,Department of Advanced Pharmaceutics, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
| | - Kazuhiko Ohashi
- Department of Disease Control, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.,Department of Advanced Pharmaceutics, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
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2
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Development of a luminescence syncytium induction assay (LuSIA) for easily detecting and quantitatively measuring bovine leukemia virus infection. Arch Virol 2018; 163:1519-1530. [PMID: 29455325 DOI: 10.1007/s00705-018-3744-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 01/02/2018] [Indexed: 01/11/2023]
Abstract
Bovine leukemia virus (BLV) causes enzootic bovine leukosis and is closely related to the human T cell leukemia virus. Since BLV infection mostly occurs via cell-to-cell transmission, BLV infectivity is generally measured by culturing BLV-infected cells with reporter cells that form syncytia upon BLV infection. However, this method is time-consuming and requires skill. To visualize the infectivity of BLV, we developed a new assay called the luminescence syncytium induction assay (LuSIA) that is based on a new reporter cell line designated CC81-BLU3G. CC81-BLU3G is stably transfected with pBLU3-EGFP, which contains the BLV long terminal repeat U3 region linked to the enhanced-green fluorescence protein (EGFP) gene. CC81-BLU3G expresses the EGFP in response to BLV Tax expression specifically, and forms fluorescing syncytia when transfected with an infectious BLV plasmid or when cultured with BLV-infected cells. Compared to the conventional assay, LuSIA was more specific and detected cattle samples with low proviral loads. The fluorescing syncytia was easily detected by eye and automated scanning and LuSIA counts correlated strongly with the proviral load of infected cattle (R2 = 0.8942).
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3
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Yuan Y, Kitamura-Muramatsu Y, Saito S, Ishizaki H, Nakano M, Haga S, Matoba K, Ohno A, Murakami H, Takeshima SN, Aida Y. Detection of the BLV provirus from nasal secretion and saliva samples using BLV-CoCoMo-qPCR-2: Comparison with blood samples from the same cattle. Virus Res 2015; 210:248-54. [PMID: 26298004 DOI: 10.1016/j.virusres.2015.08.013] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 08/12/2015] [Accepted: 08/12/2015] [Indexed: 10/23/2022]
Abstract
Bovine leukemia virus (BLV) induces enzootic bovine leukosis, which is the most common neoplastic disease in cattle. Sero-epidemiological studies show that BLV infection occurs worldwide. Direct contact between infected and uninfected cattle is thought to be one of the risk factors for BLV transmission. Contact transmission occurs via a mixture of natural sources, blood, and exudates. To confirm that BLV provirus is detectable in these samples, matched blood, nasal secretion, and saliva samples were collected from 50 cattle, and genomic DNA was extracted. BLV-CoCoMo-qPCR-2, an assay developed for the highly sensitive detection of BLV, was then used to measure the proviral load in blood (n=50), nasal secretions (n=48), and saliva (n=47) samples. The results showed that 35 blood samples, 14 nasal secretion samples, and 6 saliva samples were positive for the BLV provirus. Matched blood samples from cattle that were positive for the BLV provirus (either in nasal secretion or saliva samples) were also positive in their blood. The proviral load in the positive blood samples was >14,000 (copies/1×10(5) cells). Thus, even though the proviral load in the nasal secretion and saliva samples was much lower (<380 copies/1×10(5) cells) than that in the peripheral blood, prolonged direct contact between infected and healthy cattle may be considered as a risk factor for BLV transmission.
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Affiliation(s)
- Yuan Yuan
- RIKEN GENESIS CO., LTD., RIKEN Yokohama Institute, East Research Building 3F, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Yuri Kitamura-Muramatsu
- RIKEN GENESIS CO., LTD., RIKEN Yokohama Institute, East Research Building 3F, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Susumu Saito
- RIKEN GENESIS CO., LTD., RIKEN Yokohama Institute, East Research Building 3F, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
| | - Hiroshi Ishizaki
- NARO Institute of Livestock and Grassland Science, 768 Senbonmatsu, Nasushiobara, Tochigi 329-2793, Japan
| | - Miwa Nakano
- NARO Institute of Livestock and Grassland Science, 768 Senbonmatsu, Nasushiobara, Tochigi 329-2793, Japan
| | - Satoshi Haga
- NARO Institute of Livestock and Grassland Science, 768 Senbonmatsu, Nasushiobara, Tochigi 329-2793, Japan
| | - Kazuhiro Matoba
- NARO Institute of Livestock and Grassland Science, 768 Senbonmatsu, Nasushiobara, Tochigi 329-2793, Japan
| | - Ayumu Ohno
- Viral Infectious Diseases Unit, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Hironobu Murakami
- School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5201, Japan
| | | | - Yoko Aida
- Viral Infectious Diseases Unit, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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Ikebuchi R, Konnai S, Okagawa T, Nishimori A, Nakahara A, Murata S, Ohashi K. Differences in cellular function and viral protein expression between IgMhigh and IgMlow B-cells in bovine leukemia virus-infected cattle. J Gen Virol 2014; 95:1832-1842. [PMID: 24814926 DOI: 10.1099/vir.0.065011-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Bovine leukemia virus (BLV) induces abnormal B-cell proliferation and B-cell lymphoma in cattle, where the BLV provirus is integrated into the host genome. BLV-infected B-cells rarely express viral proteins in vivo, but short-term cultivation augments BLV expression in some, but not all, BLV-infected B-cells. This observation suggests that two subsets, i.e. BLV-silencing cells and BLV-expressing cells, are present among BLV-infected B-cells, although the mechanisms of viral expression have not been determined. In this study, we examined B-cell markers and viral antigen expression in B-cells from BLV-infected cattle to identify markers that may discriminate BLV-expressing cells from BLV-silencing cells. The proportions of IgM(high) B-cells were increased in blood lymphocytes from BLV-infected cattle. IgM(high) B-cells mainly expressed BLV antigens, whereas IgM(low) B-cells did not, although the provirus load was equivalent in both subsets. Several parameters were investigated in these two subsets to characterize their cellular behaviour. Real-time PCR and microarray analyses detected higher expression levels of some proto-oncogenes (e.g. Maf, Jun and Fos) in IgM(low) B-cells than those in IgM(high) B-cells. Moreover, lymphoma cells obtained from the lymph nodes of 14 BLV-infected cattle contained IgM(low) or IgM(-) B-cells but no IgM(high) B-cells. To our knowledge, this is the first study to demonstrate that IgM(high) B-cells mainly comprise BLV-expressing cells, whereas IgM(low) B-cells comprise a high proportion of BLV-silencing B-cells in BLV-infected cattle.
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Affiliation(s)
- Ryoyo Ikebuchi
- Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Satoru Konnai
- Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Tomohiro Okagawa
- Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Asami Nishimori
- Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Ayako Nakahara
- Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Shiro Murata
- Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Kazuhiko Ohashi
- Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
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5
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Aida Y, Murakami H, Takahashi M, Takeshima SN. Mechanisms of pathogenesis induced by bovine leukemia virus as a model for human T-cell leukemia virus. Front Microbiol 2013; 4:328. [PMID: 24265629 PMCID: PMC3820957 DOI: 10.3389/fmicb.2013.00328] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 10/17/2013] [Indexed: 11/27/2022] Open
Abstract
Bovine leukemia virus (BLV) and human T-cell leukemia virus type 1 (HTLV-1) make up a unique retrovirus family. Both viruses induce chronic lymphoproliferative diseases with BLV affecting the B-cell lineage and HTLV-1 affecting the T-cell lineage. The pathologies of BLV- and HTLV-induced infections are notably similar, with an absence of chronic viraemia and a long latency period. These viruses encode at least two regulatory proteins, namely, Tax and Rex, in the pX region located between the env gene and the 3′ long terminal repeat. The Tax protein is a key contributor to the oncogenic potential of the virus, and is also the key protein involved in viral replication. However, BLV infection is not sufficient for leukemogenesis, and additional events such as gene mutations must take place. In this review, we first summarize the similarities between the two viruses in terms of genomic organization, virology, and pathology. We then describe the current knowledge of the BLV model, which may also be relevant for the understanding of leukemogenesis caused by HTLV-1. In addition, we address our improved understanding of Tax functions through the newly identified BLV Tax mutants, which have a substitution between amino acids 240 and 265.
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Affiliation(s)
- Yoko Aida
- Viral Infectious Diseases Unit, RIKEN Wako, Saitama, Japan
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6
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Gillet N, Florins A, Boxus M, Burteau C, Nigro A, Vandermeers F, Balon H, Bouzar AB, Defoiche J, Burny A, Reichert M, Kettmann R, Willems L. Mechanisms of leukemogenesis induced by bovine leukemia virus: prospects for novel anti-retroviral therapies in human. Retrovirology 2007; 4:18. [PMID: 17362524 PMCID: PMC1839114 DOI: 10.1186/1742-4690-4-18] [Citation(s) in RCA: 242] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Accepted: 03/16/2007] [Indexed: 12/15/2022] Open
Abstract
In 1871, the observation of yellowish nodules in the enlarged spleen of a cow was considered to be the first reported case of bovine leukemia. The etiological agent of this lymphoproliferative disease, bovine leukemia virus (BLV), belongs to the deltaretrovirus genus which also includes the related human T-lymphotropic virus type 1 (HTLV-1). This review summarizes current knowledge of this viral system, which is important as a model for leukemogenesis. Recently, the BLV model has also cast light onto novel prospects for therapies of HTLV induced diseases, for which no satisfactory treatment exists so far.
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Affiliation(s)
- Nicolas Gillet
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Arnaud Florins
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Mathieu Boxus
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Catherine Burteau
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Annamaria Nigro
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Fabian Vandermeers
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Hervé Balon
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Amel-Baya Bouzar
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Julien Defoiche
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Arsène Burny
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | | | - Richard Kettmann
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Luc Willems
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
- Luc Willems, National fund for Scientific Research, Molecular and Cellular Biology laboratory, 13 avenue Maréchal Juin, 5030 Gembloux, Belgium
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Fulton BE, Portella M, Radke K. Dissemination of bovine leukemia virus-infected cells from a newly infected sheep lymph node. J Virol 2006; 80:7873-84. [PMID: 16873244 PMCID: PMC1563808 DOI: 10.1128/jvi.00529-06] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To investigate the early establishment of bovine leukemia virus (BLV) infection, we injected BLV-infected or mock-infected allogeneic cells into the shoulder of sheep in which an efferent lymphatic duct of the draining prescapular lymph node had been cannulated. Rare mononuclear cells acting as centers of BLV infection in culture were present within 4 to 6 days in efferent lymph and within 6 to 10 days in blood. Soon after BLV injection, immunoglobulin M+ (IgM+) and CD8+ cells increased in efferent lymph and oscillated reciprocally in frequency. CD8+ blasts increased on days 4 to 6, when infectious centers increased 100-fold in lymph. On days 6 and 7, both lymph and blood were enriched with CD8+ cells that were labeled late on day 5 with an intravenous pulse of 5-bromo-2'-deoxyuridine (BrdU). Lymph, but not blood, was enriched with BrdU+ B cells on day 7. Capsid-specific antibodies became detectable in efferent lymph on days 6 to 8 and surface glycoprotein-specific antibodies on day 9, preceding their detection in serum by 9 to 14 days. Systemic dissemination of BLV-infected cells was thus accompanied by an increase in proliferating CD8+ cells and the onset of BLV-specific antibodies in lymph. Infectious centers reached maximum frequencies of 0.2% in lymph by days 11 to 13, and then their frequencies increased by 5- to 40-fold in blood cells, suggesting that many infected blood cells do not recirculate back into lymph. Beginning on days 10 to 13, a subpopulation of B cells having high levels of surface IgM increased sharply in peripheral blood. Such cells were not present in lymph. After a day 16 pulse of BrdU, recently proliferated cells that stained intensely for surface IgM appeared in blood within 15 h. Predominantly B lymphocytes contained the viral capsid protein when lymph and blood cells were cultured briefly to allow BLV expression. However, both early in lymph and later in blood, BrdU+ B cells greatly exceeded productively infected cells, indicating that new BLV infections stimulate proliferation of two different populations of B cells.
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Affiliation(s)
- B E Fulton
- Department of Animal Science, University of California, One Shields Ave., Davis, CA 95616-8521, USA
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Tajima S, Takahashi M, Takeshima SN, Konnai S, Yin SA, Watarai S, Tanaka Y, Onuma M, Okada K, Aida Y. A mutant form of the tax protein of bovine leukemia virus (BLV), with enhanced transactivation activity, increases expression and propagation of BLV in vitro but not in vivo. J Virol 2003; 77:1894-903. [PMID: 12525624 PMCID: PMC140974 DOI: 10.1128/jvi.77.3.1894-1903.2003] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In a previous study, we identified an interesting mutant form of the Tax protein of bovine leukemia virus (BLV), designated D247G. This mutant protein strongly transactivated the long terminal repeat of BLV and was also able to transactivate the cellular proto-oncogene c-fos. This finding suggested that BLV that encode the mutant protein might propagate and induce lymphoma more efficiently than wild-type BLV. To characterize the effects of the strong transactivation activity of the mutant Tax protein, we constructed an infectious molecular clone of BLV that encoded D247G and examined the replication and propagation of the virus in vitro and in vivo. Cultured cells were transfected with the wild-type and mutant BLV, and then levels of viral proteins and particles and the propagation of viruses were compared. As expected, in vitro, mutant BLV produced more viral proteins and particles and was transmitted very effectively. We injected the wild-type and mutant BLV into sheep, which are easily infected with BLV, and monitored the proportion of BLV-positive cells in the blood and the expression of BLV RNA for 28 weeks. By contrast to the results of our analyses in vitro, we found no significant difference in the viral load or the expression of viral RNA between sheep inoculated with wild-type or mutant BLV. Our observations indicate that the mutant D247G Tax protein does not enhance the expansion of BLV and that there might be a dominant mechanism for regulation of the expression of BLV in vivo.
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Affiliation(s)
- Shigeru Tajima
- Retrovirus Research Unit, RIKEN, Wako, Saitama 351-0198, Japan
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9
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Johnston ER, Albritton LM, Radke K. Envelope proteins containing single amino acid substitutions support a structural model of the receptor-binding domain of bovine leukemia virus surface protein. J Virol 2002; 76:10861-72. [PMID: 12368329 PMCID: PMC136609 DOI: 10.1128/jvi.76.21.10861-10872.2002] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Functional domains of the strikingly conserved envelope (Env) glycoproteins of bovine leukemia virus (BLV) and its close relative, human T-cell leukemia virus type 1 (HTLV-1), are still being defined. We have used BLV Env protein variants to gain insights into the structure and function of this important determinant of viral infectivity. Each of 23 different single amino acid variants found in cDNA clones of env transcripts present after short-term culture of peripheral blood mononuclear cells from BLV-infected sheep was expressed in COS-1 cells and tested for the ability to mediate cell fusion and to be cleaved to surface (SU) and transmembrane (TM) protein subunits. Of 11 Env variants that failed to induce syncytia or did so poorly, 7 contained changes in amino acids identical or chemically conserved in the HTLV-1 Env protein. These seven included the four variants that showed aberrant proteolytic cleavage and poor cell surface expression, underscoring their importance for Env structure. Ten of 12 variants that retained wild-type syncytium-inducing ability clustered in the N-terminal half of BLV SU, which forms the putative receptor-binding domain (RBD). Several variants in the RBD showed evidence of subtle misfolding, as judged by reduced binding to monoclonal antibodies recognizing conformational epitopes F, G, and H formed by the N terminus of SU. We modeled the BLV RBD by aligning putative structural elements with known elements of the ecotropic Friend murine leukemia virus RBD monomer. All the variant RBD residues but one are exposed on the surface of this BLV model. These variants as well as function-altering, antibody-reactive residues defined by other investigators group on one face of the molecular model. They are strikingly absent from the opposite face, implying that it is likely to face inward in Env complexes. This surface might interact with the C-terminal domain of SU or with an adjacent monomer in the Env oligomer. This location suggests an orientation for the monomer of ecotropic Friend murine leukemia virus RBD.
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Affiliation(s)
- Elizabeth R Johnston
- Department of Animal Science and Graduate Group in Biochemistry and Molecular Biology, University of California, Davis, California 95616, USA
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10
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Johnston ER, Radke K. The SU and TM envelope protein subunits of bovine leukemia virus are linked by disulfide bonds, both in cells and in virions. J Virol 2000; 74:2930-5. [PMID: 10684314 PMCID: PMC111788 DOI: 10.1128/jvi.74.6.2930-2935.2000] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
After the polyprotein precursor of retroviral envelope proteins is proteolytically cleaved, the surface (SU) and transmembrane (TM) subunits remain associated with each other by noncovalent interactions or by disulfide bonds. Disulfide linkages confer a relatively stable association between the SU and TM envelope protein subunits of Rous sarcoma virus and murine leukemia virus. In contrast, the noncovalent association between SU and TM of human immunodeficiency virus leads to significant shedding of SU from the surface of infected cells. The SU and TM proteins of bovine leukemia virus (BLV) initially were reported to be disulfide linked but later were concluded not to be, since TM is often lost during purification of SU protein. Here, we show that SU and TM of BLV do, indeed, associate through disulfide bonds, whether the envelope proteins are overexpressed in transfected cells, are produced in virus-infected cells, or are present in newly produced virions.
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Affiliation(s)
- E R Johnston
- Department of Animal Science and Graduate Group in Biochemistry and Molecular Biology, University of California, Davis, California 95616-8521, USA
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11
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Chevallier N, Berthelemy M, Le Rhun D, Lainé V, Levy D, Schwartz-Cornil I. Bovine leukemia virus-induced lymphocytosis and increased cell survival mainly involve the CD11b+ B-lymphocyte subset in sheep. J Virol 1998; 72:4413-20. [PMID: 9557733 PMCID: PMC109673 DOI: 10.1128/jvi.72.5.4413-4420.1998] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In this study, we show that bovine leukemia virus (BLV)-induced persistent lymphocytosis (PL) results from the in vivo expansion of the CD11b+ B-lymphocyte population. This subset shares phenotypic characteristics with murine and human B-1 cells. BLV interactions with the sheep B-1-like subset were explored. We found that B-1- and B-2-like cells are initially infected to similar extents. However, in long-term-infected sheep, the viral load is higher in B-1-like cells and only B-1- and not B-2-like cells show increased ex vivo survival compared to that in uninfected sheep. Ex vivo viral expression was found in both B-1- and B-2-like cells, indicating that both cell types support viral replication. Finally, cycloheximide and a protein kinase C inhibitor (H7) that blocks the ex vivo activation of viral expression did not affect the increased survival in B-1-like cells, suggesting that resistance to apoptosis is acquired in vivo. Collectively, these results indicate a peculiar susceptibility of sheep B-1-like cells to BLV transforming effects and further support the involvement of increased survival in BLV pathogenesis.
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Affiliation(s)
- N Chevallier
- URA INRA-DGER d'Immunopathologie Cellulaire et Moléculaire, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
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