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Hirons A, Khoury G, Purcell DFJ. Human T-cell lymphotropic virus type-1: a lifelong persistent infection, yet never truly silent. THE LANCET. INFECTIOUS DISEASES 2020; 21:e2-e10. [PMID: 32986997 DOI: 10.1016/s1473-3099(20)30328-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Revised: 04/06/2020] [Accepted: 04/16/2020] [Indexed: 12/12/2022]
Abstract
Human T-cell lymphotropic virus type-1 (HTLV-1) has a large global burden and in some key communities, such as Indigenous Australians living in remote areas, greater than 45% of people are infected. Despite HTLV-1 causing serious malignancy and myelopathic paraparesis, and a significant association with a range of inflammatory comorbidities and secondary infections that shorten lifespan, few biomedical interventions are available. HTLV-1 starkly contrasts with other blood-borne sexually transmitted viral infections, such as, HIV, hepatitis B virus, and hepatitis C virus, with no antiviral treatments that reduce virus-infected cells, no rapid diagnostics or biomarker assays suitable for use in remote settings, and no effective vaccine. We review how the replication strategies and molecular properties of HTLV-1 establish a long-term stealthy viral pathogenesis through a fine-tuned balance of persistence, immune cell dysfunction, and proliferation of proviral infected cells that collectively present robust barriers to treatment and prevention. An understanding of the nature of the HTLV-1 provirus and opposing actions of viral-coded negative-sense HBZ and positive-sense regulatory proteins Tax, p12 and its cleaved product p8, and p30, is needed to improve the biomedical tools for preventing transmission and improving the long-term health of people with this lifelong infection.
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Affiliation(s)
- Ashley Hirons
- The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia
| | - Georges Khoury
- The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia
| | - Damian F J Purcell
- The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia.
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2
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Bangham CRM, Miura M, Kulkarni A, Matsuoka M. Regulation of Latency in the Human T Cell Leukemia Virus, HTLV-1. Annu Rev Virol 2019; 6:365-385. [PMID: 31283437 DOI: 10.1146/annurev-virology-092818-015501] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The human T cell leukemia virus persists in vivo in 103 to 106 clones of T lymphocytes that appear to survive for the lifetime of the host. The plus strand of the provirus is typically transcriptionally silent in freshly isolated lymphocytes, but the strong, persistently activated cytotoxic T lymphocyte (CTL) response to the viral antigens indicates that the virus is not constantly latent in vivo. There is now evidence that the plus strand is transcribed in intense intermittent bursts that are triggered by cellular stress, modulated by hypoxia and glycolysis, and inhibited by polycomb repressive complex 1 (PRC1). The minus-strand gene hbz is transcribed at a lower, more constant level but is silent in a proportion of infected cells at a given time. Viral genes in the sense and antisense strands of the provirus play different respective roles in latency and de novo infection: Expression of the plus-strand gene tax is essential for de novo infection, whereas hbz appears to facilitate survival of the infected T cell clone in vivo.
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Affiliation(s)
- Charles R M Bangham
- Division of Infectious Diseases, Department of Medicine, Imperial College London, London W2 1PG, United Kingdom;
| | - Michi Miura
- Division of Infectious Diseases, Department of Medicine, Imperial College London, London W2 1PG, United Kingdom;
| | - Anurag Kulkarni
- Division of Infectious Diseases, Department of Medicine, Imperial College London, London W2 1PG, United Kingdom;
| | - Masao Matsuoka
- Laboratory of Virus Control, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto 606-8507, Japan.,Department of Hematology, Rheumatology and Infectious Diseases, Kumamoto University School of Medicine, Kumamoto 860-8556, Japan;
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3
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Palker TJ. Human T-cell Lymphotropic Viruses: Review and Prospects for Antiviral Therapy. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/095632029200300301] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The human T-cell lymphotropic viruses types I and II (HTLV-I, II) pose challenges to researchers and clinicians who seek to unveil mechanisms of viral transformation and pathogenesis. HTLV-I infection in humans is associated with a wide array of primary and secondary diseases ranging from mild immunosuppression to adult T-cell leukaemia/lymphoma and HTLV-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a neurological degenerative syndrome. As retroviruses, HTLV-I and II share similar replicative cycles with human immunodeficiency virus (HIV), the causative agent of acquired immunodeficiency syndrome. However, in contrast to HIV-I which destroys CD4+ T cells, HTLV-I and II can preferentially transform a CD4+ T-cell subset to an unrestricted growth state. HTLV-I and II, along with simian T-lymphotropic virus (STLV) and bovine leukaemia virus (BLV), form a phylogenetic group which is distinct from ungulate, non-human primate and human lentiviruses such as visna, simian immunodeficiency virus (SIV), and human immunodeficiency viruses types 1 and 2. The proviral genome of HTLV-I is flanked at the 5′ and 3′ ends by long terminal repeats (LTR) and is further subdivided into structural gag and env genes, a pro gene encoding an aspartyl protease, a pol gene which encodes reverse transcriptase and endonuclease, and the regulatory gene elements tax and rex. Regions within the LTR contain recognition sites for cellular proteins and the tax gene product that collectively promote viral expression. Tax-mediated activation of cellular genes involved in growth and differentiation is suspected to play a dominant role in the leukaemogenic process associated with HTLV-I infection. Differential rex-regulated splicing of viral message gives rise to transcripts encoding the polyprotein precursor gag-pro-pol (unspliced), envelope (single spliced), or tax/rex (doubly spliced). The 100nm HTLV virion contains an electron-dense core surrounding a divalent-single stranded DNA genome. This core is in turn enclosed by concentric shells of matrix protein and an outer lipid bilayer, the latter acquired as the virus buds from the surface of the infected cell. Envelope glycoproteins associated with the outside of this lipid bilayer can interact with viral receptors on cells and mediate virus entry. Antiviral strategies have been directed at inhibiting viral entry into cells (sulphated and non-sulphated polysaccharides, vaccines), blocking of viral replication (AZT, suramin), intracellular immunization (transdominant repression of rex), and elimination of virus infected cells (IL-2 receptor-directed toxins). Serological screening of the blood supply and curtailing breast feeding of children by HTLV-I + mothers have likely had a major impact in preventing HTLV-I infection.
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Affiliation(s)
- T. J. Palker
- Duke University Medical Center, P.O. Box 3307, Durham, NC, 27710, USA
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4
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HTLV-1 clonality in adult T-cell leukaemia and non-malignant HTLV-1 infection. Semin Cancer Biol 2013; 26:89-98. [PMID: 24316494 PMCID: PMC4062949 DOI: 10.1016/j.semcancer.2013.11.003] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2013] [Accepted: 11/28/2013] [Indexed: 11/21/2022]
Abstract
Human T lymphotropic virus type 1 (HTLV-1) causes a range of chronic inflammatory diseases and an aggressive malignancy of T lymphocytes known as adult T-cell leukaemia/lymphoma (ATLL). A cardinal feature of HTLV-1 infection is the presence of expanded clones of HTLV-1-infected T cells, which may persist for decades. A high viral burden (proviral load) is associated with both the inflammatory and malignant diseases caused by HTLV-1, and it has been believed that the oligoclonal expansion of infected cells predisposes to these diseases. However, it is not understood what regulates the clonality of HTLV-1 in vivo, that is, the number and abundance of HTLV-1-infected T cell clones. We review recent advances in the understanding of HTLV-1 infection and disease that have come from high-throughput quantification and analysis of HTLV-1 clonality in natural infection.
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Interaction between the HTLV-1 envelope and cellular proteins: impact on virus infection and restriction. Future Med Chem 2011; 2:1651-68. [PMID: 21428837 DOI: 10.4155/fmc.10.255] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The first human retrovirus, human T-lymphotropic virus 1 (HTLV-1), was discovered 30 years ago. Despite intensive study, the cell surface molecules involved in virus entry have only been identified over the past few years. Three molecules form the receptor complex for HTLV-1: glucose transporter 1, neuropilin 1 and heparan sulfate proteoglycans. Another molecule on the surface of dendritic cells, DC-SIGN, may play a role in dendritic cell-mediated infection of cells. In addition to the cell surface molecules used for entry, the HTLV-1 envelope interacts with cellular proteins, enabling the virus to traffic by exploiting cellular delivery pathways. To facilitate both these steps, HTLV-1 encodes motifs that mimic cellular binding partners for the trafficking system and ligands for the receptors. Here we review the interactions between the HTLV-1 envelope and cellular proteins.
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Strong induction of 4-1BB, a growth and survival promoting costimulatory receptor, in HTLV-1-infected cultured and patients' T cells by the viral Tax oncoprotein. Blood 2008; 111:4741-51. [PMID: 18276843 DOI: 10.1182/blood-2007-10-115220] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1), the cause of adult T-cell leukemia, stimulates the growth of infected T cells in cultures and in nonleukemic patients. In the latter, HTLV-1 is found in long-term persisting T-cell clones. The persistence of normal T cells is controlled by the growth-stimulating and antiapoptotic functions of costimulatory receptors, while the growth-stimulating HTLV-1 functions are mediated by the viral oncoprotein Tax. Here we analyzed the impact of Tax on costimulatory receptors in T cells with repressible Tax and found that among these receptors 4-1BB (TNFRSF9/CD137/ILA) was induced most strongly. Up-regulated 4-1BB expression was a consistent feature of all HTLV-1-infected cell lines, whether patient-derived or in vitro transformed. Tax was sufficient to induce the expression of the endogenous 4-1BB gene in uninfected T cells, and it strongly activated (45-fold) the 4-1BB promoter via a single NF-kappaB site. The ligand of 4-1BB was also found on transformed T-cell lines, opening up the possibility of autostimulation. Moreover, 4-1BB expression in patients' lymphocytes ex vivo correlated with Tax expression, strongly suggesting Tax-mediated 4-1BB activation in vivo. Thus, 4-1BB up-regulation by Tax could contribute to growth, survival, and clonal expansion of the infected cells during persistence and disease.
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7
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Asquith B, Bangham CRM. How does HTLV-I persist despite a strong cell-mediated immune response? Trends Immunol 2007; 29:4-11. [PMID: 18042431 DOI: 10.1016/j.it.2007.09.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Revised: 08/23/2007] [Accepted: 09/05/2007] [Indexed: 11/18/2022]
Abstract
Human T-lymphotropic virus type 1 (HTLV-1) is a pathogenic retrovirus that infects human CD4(+) T lymphocytes. Despite its presence in T cells, HTLV-1 causes little overt immunosuppression. This host-virus relationship has therefore been exploited as an excellent model system for studying the dynamic interaction between a persistent retrovirus and the normal human immune system. We use a combination of mathematical and experimental techniques to identify key factors on both sides of the in vivo host-virus interaction that significantly determine HTLV-I proviral load and disease risk. We develop a model to describe how these factors interact to enable viral persistence.
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Affiliation(s)
- Becca Asquith
- Department of Immunology, Wright-Fleming Institute, Imperial College London, London, W2 1PG, UK.
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8
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Asquith B, Zhang Y, Mosley AJ, de Lara CM, Wallace DL, Worth A, Kaftantzi L, Meekings K, Griffin GE, Tanaka Y, Tough DF, Beverley PC, Taylor GP, Macallan DC, Bangham CRM. In vivo T lymphocyte dynamics in humans and the impact of human T-lymphotropic virus 1 infection. Proc Natl Acad Sci U S A 2007; 104:8035-40. [PMID: 17483473 PMCID: PMC1861853 DOI: 10.1073/pnas.0608832104] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Human T-lymphotropic virus type 1 (HTLV-1) is a persistent CD4+ T-lymphotropic retrovirus. Most HTLV-1-infected individuals remain asymptomatic, but a proportion develop adult T cell leukemia or inflammatory disease. It is not fully understood how HTLV-1 persists despite a strong immune response or what determines the risk of HTLV-1-associated diseases. Until recently, it has been difficult to quantify lymphocyte kinetics in humans in vivo. Here, we used deuterated glucose labeling to quantify in vivo lymphocyte dynamics in HTLV-1-infected individuals. We then used these results to address four questions. (i) What is the impact of HTLV-1 infection on lymphocyte dynamics? (ii) How does HTLV-1 persist? (iii) What is the extent of HTLV-1 expression in vivo? (iv) What features of lymphocyte kinetics are associated with HTLV-1-associated myelopathy/tropical spastic paraparesis? We found that CD4+CD45RO+ and CD8+CD45RO+ T lymphocyte proliferation was elevated in HTLV-1-infected subjects compared with controls, with an extra 10(12) lymphocytes produced per year in an HTLV-1-infected subject. The in vivo proliferation rate of CD4+CD45RO+ cells also correlated with ex vivo viral expression. Finally, the inflammatory disease HTLV-1-associated myelopathy/tropical spastic paraparesis was associated with significantly increased CD4+CD45RO+ cell proliferation. We suggest that there is persistent viral gene expression in vivo, which is necessary for the maintenance of the proviral load and determines HTLV-1-associated myelopathy/tropical spastic paraparesis risk.
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Affiliation(s)
- Becca Asquith
- *Department of Immunology, Imperial College, London W2 1PG, United Kingdom
- To whom correspondence may be addressed. E-mail: or
| | - Yan Zhang
- Centre for Infection, Division of Cellular and Molecular Medicine, St. George's, University of London, Cranmer Terrace, London SW17 0RE, United Kingdom
| | - Angelina J. Mosley
- *Department of Immunology, Imperial College, London W2 1PG, United Kingdom
| | - Catherine M. de Lara
- Edward Jenner Institute for Vaccine Research, Compton, Newbury, Berkshire RG20 7NN, United Kingdom
| | - Diana L. Wallace
- Edward Jenner Institute for Vaccine Research, Compton, Newbury, Berkshire RG20 7NN, United Kingdom
| | - Andrew Worth
- Edward Jenner Institute for Vaccine Research, Compton, Newbury, Berkshire RG20 7NN, United Kingdom
| | - Lambrini Kaftantzi
- *Department of Immunology, Imperial College, London W2 1PG, United Kingdom
| | - Kiran Meekings
- *Department of Immunology, Imperial College, London W2 1PG, United Kingdom
| | - George E. Griffin
- Centre for Infection, Division of Cellular and Molecular Medicine, St. George's, University of London, Cranmer Terrace, London SW17 0RE, United Kingdom
| | - Yuetsu Tanaka
- Department of Immunology, Graduate School and Faculty of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan; and
| | - David F. Tough
- Edward Jenner Institute for Vaccine Research, Compton, Newbury, Berkshire RG20 7NN, United Kingdom
| | - Peter C. Beverley
- Edward Jenner Institute for Vaccine Research, Compton, Newbury, Berkshire RG20 7NN, United Kingdom
| | - Graham P. Taylor
- Department of Genito-Urinary Medicine, Imperial College London, London W2 1PG, United Kingdom
| | - Derek C. Macallan
- Centre for Infection, Division of Cellular and Molecular Medicine, St. George's, University of London, Cranmer Terrace, London SW17 0RE, United Kingdom
| | - Charles R. M. Bangham
- *Department of Immunology, Imperial College, London W2 1PG, United Kingdom
- To whom correspondence may be addressed. E-mail: or
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9
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Abstract
Despite significant advances in our understanding of the immune response to persistent viruses like human T-cell lymphotropic virus type I (HTLV-I), many important questions remain unanswered. Mathematical modelling enables us to interpret and synthesise diverse experimental data in new ways and thus can contribute to our understanding. Here, we review recent advances in mathematical modelling of HTLV-I infection and illustrate how mathematics has enabled us to identify factors that determine an individual's viral burden and risk of developing HTLV-I-associated diseases.
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Affiliation(s)
- Becca Asquith
- Department of Immunology, Imperial College London, London, UK.
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10
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Asquith B, Mosley AJ, Heaps A, Tanaka Y, Taylor GP, McLean AR, Bangham CRM. Quantification of the virus-host interaction in human T lymphotropic virus I infection. Retrovirology 2005; 2:75. [PMID: 16336683 PMCID: PMC1327681 DOI: 10.1186/1742-4690-2-75] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2005] [Accepted: 12/09/2005] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND HTLV-I causes the disabling inflammatory disease HAM/TSP: there is no vaccine, no satisfactory treatment and no means of assessing the risk of disease or prognosis in infected people. Like many immunopathological diseases with a viral etiology the outcome of infection is thought to depend on the virus-host immunology interaction. However the dynamic virus-host interaction is complex and current models of HAM/TSP pathogenesis are conflicting. The CD8+ cell response is thought to be a determinant of both HTLV-I proviral load and disease status but its effects can obscure other factors. RESULTS We show here that in the absence of CD8+ cells, CD4+ lymphocytes from HAM/TSP patients expressed HTLV-I protein significantly more readily than lymphocytes from asymptomatic carriers of similar proviral load (P = 0.017). A high rate of viral protein expression was significantly associated with a large increase in the prevalence of HAM/TSP (P = 0.031, 89% of cases correctly classified). Additionally, a high rate of Tax expression and a low CD8+ cell efficiency were independently significantly associated with a high proviral load (P = 0.005, P = 0.003 respectively). CONCLUSION These results disentangle the complex relationship between immune surveillance, proviral load, inflammatory disease and viral protein expression and indicate that increased protein expression may play an important role in HAM/TSP pathogenesis. This has important implications for therapy since it suggests that interventions should aim to reduce Tax expression rather than proviral load per se.
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Affiliation(s)
- Becca Asquith
- Department of Immunology, Imperial College, London W2 1PG, UK
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK
| | | | - Adrian Heaps
- Department of Immunology, Imperial College, London W2 1PG, UK
| | - Yuetsu Tanaka
- Department of Immunology, Graduate School and Faculty of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan
| | - Graham P Taylor
- Department of Genito-Urinary Medicine and Communicable Diseases, Imperial College, London W2 1PG, UK
| | - Angela R McLean
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK
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11
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Abstract
All retroviruses possess a highly error-prone reverse transcriptase, but the extent of the consequent sequence diversity and the rate of evolution differ greatly among retroviruses. Because of the high mutability of retroviruses, it is not the generation of new viral variants that limits the extent of diversity and the rate of evolution of retroviruses, but rather the selection forces that act on these variants. Here, we suggest that two selection forces--the immune response and the limited availability of appropriate target cells during transmission and persistence--are chiefly responsible for the observed sequence diversity in untreated retroviral infections. We illustrate these aspects of positive selection by reference to specific lentiviruses [human and simian immunodeficiency viruses (HIV and SIV)] and oncoviruses [feline leukemia virus (FeLV) and human T cell leukemia virus (HTLV)] that differ in their extent of variation and in disease outcomes.
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Affiliation(s)
- J Overbaugh
- Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
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12
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Asquith B, Bangham CR. The role of cytotoxic T lymphocytes in human T-cell lymphotropic virus type 1 infection. J Theor Biol 2000; 207:65-79. [PMID: 11027480 DOI: 10.1006/jtbi.2000.2156] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The vast majority of individuals infected with human T-cell lymphotropic virus type 1 have a strong and persistently activated cytotoxic T lymphocyte response to the virus. Experimental work investigating the effects of human T-cell lymphotropic virus-specific cytotoxic T lymphocytes is conflicting. One significant body of work suggests that specific cytotoxic T lymphocytes are protective and help to reduce the risk of disease. However, another body of work implies that specific cytotoxic T lymphocytes play an important role in the development of disease. Here we use a theoretical model to explore the role of cytotoxic T lymphocytes in persistent infection. A way of reconciling the apparently contradictory data is proposed and experimentally testable predictions are made.
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Affiliation(s)
- B Asquith
- Department of Immunology, Imperial College School of Medicine, St Mary's, Norfolk Place, London, W2 1PG, U.K
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13
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Abstract
A strong cytotoxic T lymphocyte response to HTLV-I protects against the associated inflammatory disease of the central nervous system, HAM/TSP (HTLV-I-associated myelopathy/tropical spastic paraparesis), by reducing the proviral load of HTLV-I; however, when the proviral load exceeds a threshold level, HTLV-I-specific cytotoxic T lymphocytes could contribute to inflammation.
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Affiliation(s)
- C R Bangham
- Department of Immunology, Imperial College School of Medicine, London, W2 1PG, UK.
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14
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Bangham CR, Hall SE, Jeffery KJ, Vine AM, Witkover A, Nowak MA, Wodarz D, Usuku K, Osame M. Genetic control and dynamics of the cellular immune response to the human T-cell leukaemia virus, HTLV-I. Philos Trans R Soc Lond B Biol Sci 1999; 354:691-700. [PMID: 10365395 PMCID: PMC1692558 DOI: 10.1098/rstb.1999.0422] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
About 1% of people infected with the human T-cell leukaemia virus, type 1 (HTLV-I) develop a disabling chronic inflammatory disease of the central nervous system known as HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Patients with HAM/TSP have a vigorous immune response to HTLV-I, and it has been widely suggested that this immune response, particularly the HTLV-I-specific cytotoxic T-lymphocyte (CTL) response, causes the tissue damage that is seen in HAM/TSP. In this paper we summarize recent evidence that a strong CTL response to HTLV-I does in fact protect against HAM/TSP by reducing the proviral load of HTLV-I. We conclude that HTLV-I is persistently replicating at a high level, despite the relative constancy of its genome sequence. These results imply that antiretroviral drugs could reduce the risk of HAM/TSP by reducing the viral load, and that an effective anti-HTLV-I vaccine should elicit a strong CTL response to the virus. The dynamic nature of the infection also has implications for the epidemiology and the evolution of HTLV-I.
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Affiliation(s)
- C R Bangham
- Department of Immunology, Imperial College School of Medicine, London, UK.
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15
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Suzuki Y, Gojobori T. The origin and evolution of human T-cell lymphotropic virus types I and II. Virus Genes 1998; 16:69-84. [PMID: 9562892 DOI: 10.1023/a:1007953826869] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Studies on human T-cell lymphotropic virus types I (HTLV-I) and II (HTLV-II) are briefly reviewed from the viewpoint of molecular evolution, with special reference to the evolutionary rate and evolutionary relationships among these viruses. In particular, it appears that, in contrast to the low level of variability of HTLV-I among different isolates, individual isolates form quasispecies structures. Elucidating the mechanisms connecting these two phenomena will be one of the future problems in the study of the molecular evolution of HTLV-I and HTLV-II.
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Affiliation(s)
- Y Suzuki
- Center for Information Biology, National Institute of Genetics, Mishima, Japan
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16
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Fechner H, Blankenstein P, Looman AC, Elwert J, Geue L, Albrecht C, Kurg A, Beier D, Marquardt O, Ebner D. Provirus variants of the bovine leukemia virus and their relation to the serological status of naturally infected cattle. Virology 1997; 237:261-9. [PMID: 9356338 DOI: 10.1006/viro.1997.8784] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Infection of cattle with the bovine leukemia virus (BLV) results in a strong permanent antibody response to the BLV antigens some weeks after infection. However, cattle may carry provirus and not have detectable antibody titers. To prove the occurrence of different BLV provirus variants in German cattle and to study the influence of special BLV variants on the immunoreaction, a 444-bp fragment of the env gene of 35 naturally BLV infected animals was analyzed. Seven different groups of BLV provirus variants were found on the basis of restriction fragment length polymorphism. Three BLV provirus variant groups and five additionally sequenced BLV isolates showed a high similarity to BLV provirus isolates from other geographical areas. The variation in nucleotide sequence of the five BLV isolates compared with nine previously sequenced BLV isolates ranged up to 5. 3%. While BLV provirus variant groups A, C, D, E, F, and G were clearly related to agar-gel immunodiffusion test (AGID)- and enzyme-linked immunosorbent assay (ELISA)-positive animals, BLV provirus variant group B was solely found in permanent AGID- and ELISA-negative or in transient ELISA-positive animals. Altogether, these results indicate that special BLV provirus variants may be responsible for atypical forms of BLV infection in cattle.
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Affiliation(s)
- H Fechner
- Faculty of Veterinary Medicine, Free University of Berlin, Luisenstrasse 56, Berlin D-10117, Germany
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17
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Niewiesk S, Bangham CR. Evolution in a chronic RNA virus infection: selection on HTLV-I tax protein differs between healthy carriers and patients with tropical spastic paraparesis. J Mol Evol 1996; 42:452-8. [PMID: 8642614 DOI: 10.1007/bf02498639] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
HTLV-I causes T-cell leukemia and tropical spastic paraparesis (TSP) in a minority of infected people, whereas the majority remain healthy. The virus differs little in sequence between isolates but has been shown to have a quasispecies structure. Using the Nei and Gojobori algorithm, we have shown that the proportion of nonsynonymous to synonymous changes in HTLV-I proviral tax gene sequences from healthy seropositive subjects (Dn/Ds = 0.9 to 1.3) is significantly higher than those from TSP patients (Dn/Ds = 0.3 to 0.6). Here we show that the distinction between healthy seropositives and TSP patients can only be seen with proviral tax sequences, but not with cDNA, the amino-terminal or carboxy-terminal half of tax, or the rex gene. The Dn/Ds ratio of proviral tax sequences was used to analyze two TSP patients with atypical features and to investigate the influence of cytotoxic T cells (CTL) on the viral quasispecies.
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Affiliation(s)
- S Niewiesk
- Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford, United Kingdom
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18
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Gojobori T, Yamaguchi Y, Ikeo K, Mizokami M. Evolution of pathogenic viruses with special reference to the rates of synonymous and nonsynonymous substitutions. IDENGAKU ZASSHI 1994; 69:481-8. [PMID: 7999369 DOI: 10.1266/jjg.69.481] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
For pathogenic viruses such as human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), human influenza A virus, and human T-cell leukemia virus type I (HTLV-I), the evolutionary features were briefly reviewed with special reference to the rates of synonymous and nonsynonymous substitutions. In particular, these rates were discussed in connection with the neutral theory of molecular evolution. It was common to all the five pathogenic viruses that the rate of synonymous substitution was higher than that of nonsynonymous substitution particularly when the entire gene regions were compared between different isolates. This suggests that the viral proteins are quite conservative to functional and structural changes even though most of these viral genomes are evolving at a speed extraordinarily higher than their host genomes. Thus, this feature is consistent with the neutral theory. However, it is also pointed out that positive selection may be operating on some specific sites such as antigenic sites in order for the pathogenic viruses to escape from the host immune system.
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Affiliation(s)
- T Gojobori
- National Institute of Genetics, Mishima, Japan
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19
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Niewiesk S, Daenke S, Parker CE, Taylor G, Weber J, Nightingale S, Bangham CR. The transactivator gene of human T-cell leukemia virus type I is more variable within and between healthy carriers than patients with tropical spastic paraparesis. J Virol 1994; 68:6778-81. [PMID: 8084014 PMCID: PMC237103 DOI: 10.1128/jvi.68.10.6778-6781.1994] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Human T-cell leukemia virus type I (HTLV-1) causes T-cell leukemia and tropical spastic paraparesis (TSP) in a minority of infected people, whereas the majority remain healthy. No association between a particular HTLV-I sequence and disease manifestation has been found in previous studies. We studied here the sequence variability of the gene for the HTLV-I Tax protein, which is the dominant target antigen of the very strong cytotoxic T-lymphocyte response to the virus. In HTLV-I infection, the intraisolate nucleotide variability is much greater than the variability between isolates. The predicted protein sequence of Tax was significantly more variable in the healthy seropositive individuals' provirus than in those of the patients with TSP. Thus, tax sequence heterogeneity, rather than the presence of particular sequences, distinguishes healthy HTLV-I-seropositive individuals from patients with TSP.
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Affiliation(s)
- S Niewiesk
- Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford, United Kingdom
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20
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Bronson EC, Anderson JN. Nucleotide composition as a driving force in the evolution of retroviruses. J Mol Evol 1994; 38:506-32. [PMID: 8028030 DOI: 10.1007/bf00178851] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
All complete retrovirus sequences in the GenEMBL database were examined with the goal of assessing possible relationships between the nucleotide composition of retroviral genomes, the amino acid composition of retroviral proteins, and evolutionary strategies used by retroviruses. The results demonstrated that the genome of each viral lineage has a characteristic base composition and that the variations between groups are related to retroviral phylogeny. By analogy to microbial species, we suggest that the variations arise from group-specific patterns of directional mutations where the bias can be exerted on any of the four nucleotides. It is most likely that the mutational patterns are introduced during reverse transcription, and a direct participation of reverse transcriptase in the process is suspected. A straightforward strategy was used to analyze the compositional relationship between nucleotides and encoded amino acids. The procedure entailed calculations of amino acid frequencies from nucleotide content and the comparison of the calculated values to the observed amino acid frequencies in retroviruses. The results revealed an excellent correspondence between variation in genomic base composition and variation in amino acid composition of proteins with the compositional differences extending into all major coding regions of the viruses. Because of the magnitude and dispersion of these effects, and because of the nonconservative nature of many of the substitutions between groups with different genomic biases, we suggest that the variations in protein composition driven by biased nucleotide frequencies are an important factor in shaping the characteristic phenotypes of the different viral lineages. A clue to the nature of the evolutionary forces that are responsible for the generation of nucleotide biases was provided by the observation that viruses with radically different base frequencies most often inhabit the same cell type. This observation, along with analysis of amino acid and nucleotide replacement patterns between and within reverse transcriptase sequences from the various groups, permitted us to advance a model for the evolution of retroviruses. According to the model, speciation could initiate when daughter virions from a single progenitor vary in the direction of their mutational bias. These variations would exert a pleiotropic effect on the frequencies of nucleotides in all viral genes and consequently on the frequencies of amino acids in the encoded proteins. The variants with the most extreme compositional differences would have a selective advantage because their different precursor requirements would enable them to occupy different ecological niches within a single cell.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- E C Bronson
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907
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21
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Chen YM, Jang YJ, Kanki PJ, Yu QC, Wang JJ, Montali RJ, Samuel KP, Papas TS. Isolation and characterization of simian T-cell leukemia virus type II from New World monkeys. J Virol 1994; 68:1149-57. [PMID: 7507178 PMCID: PMC236553 DOI: 10.1128/jvi.68.2.1149-1157.1994] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Since the description of human T-cell leukemia virus type I (HTLV-I) and its simian counterpart, simian T-cell leukemia virus type I (STLV-I), the possible existence of other related simian retroviruses has been raised. Here, we report a new retrovirus, STLV-II, which we have identified in spider monkeys (Ateles fusciceps), a New World primate species. Initially, a recombinant HTLV-II envelope protein (RP-IIB) was used to identify anti-STLV-II antibodies in New World monkeys by Western blot (immunoblot) assays. Subsequently, the virus was characterized by Southern blot hybridization, which showed that STLV-II and HTLV-II have a high degree of nucleotide sequence homology but have different restriction enzyme patterns. Nucleotide sequence analysis of the pX-II region of STLV-II provirus revealed 3% variation with the corresponding region of HTLV-II. Electron micrographic studies revealed HTLV-like, type C retrovirus particles outside the cell membranes of STLV-II-infected cells. This study describes the first link between HTLV-II and a simian reservoir in the New World. Further molecular studies of STLV-II infection in different species of New World monkeys, especially from the wild, may provide valuable information about the origin and intragroup relationships of South American monkeys. Spider monkeys infected with STLV-II may serve as an important animal model for HTLV-II infection in humans.
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Affiliation(s)
- Y M Chen
- Institute of Biomedical Sciences, Academia Sinica, Nan-Kang, Taipei, Taiwan, Republic of China
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22
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Miura T, Fukunaga T, Igarashi T, Yamashita M, Ido E, Funahashi S, Ishida T, Washio K, Ueda S, Hashimoto K. Phylogenetic subtypes of human T-lymphotropic virus type I and their relations to the anthropological background. Proc Natl Acad Sci U S A 1994; 91:1124-7. [PMID: 8302841 PMCID: PMC521466 DOI: 10.1073/pnas.91.3.1124] [Citation(s) in RCA: 124] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Isolates of human T-lymphotropic virus type I (HTLV-I) were phylogenetically analyzed from native inhabitants in India and South America (Colombia and Chile) and from Ainu (regarded as pure Japanese descendants from the preagricultural "Jomon" period). Their genomes were partially sequenced together with isolates from Gabon in central Africa and from Ghana in West Africa. The phylogenetic tree was constructed from the sequence data obtained and those of previously reported HTLV-I isolates and simian T-lymphotropic virus type I (STLV-I) isolates. The heterogeneity of HTLV-I was recently recognized, and one major type, generally called the "cosmopolitan" type, contained Japanese, Caribbean, and West African isolates. The phylogenetic tree constructed in the present study has shown that this cosmopolitan type can be further grouped into three lineages (subtypes A, B, and C). Subtype A consists of some Caribbean, two South American, and some Japanese isolates, including that from the Ainu, in addition to an Indian isolate, and subtype B consists of other Japanese isolates in addition to another Indian isolate, suggesting that there might be at least two ancestral lineages of the Japanese HTLV-I. Subtype A implies a close connection of the Caribbean and South American natives with the Japanese and thereby a possible migration of the lineage to the American continent via Beringia in the Paleolithic era. Subtype C consists of the West African and other Caribbean isolates, indicating that not all but part of the Caribbean strains directly originated from West Africa probably during the period of slave trade. The tree also has shown that the HTLV-I isolate from Gabon in central Africa forms a cluster with STLV-I from a chimpanzee, suggesting a possible interspecies transmission between man and the chimpanzee in the past. No specific clustering was observed in the tree in relation to manifestations of the disease such as adult T-cell leukemia and HTLV-I-related neurological disorders. Thus, the topology of the phylogenetic tree reflects the movement of people carrying the virus in the past.
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Affiliation(s)
- T Miura
- Institute for Virus Research, Kyoto University, Japan
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23
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Mansky LM, Temin HM. Lower mutation rate of bovine leukemia virus relative to that of spleen necrosis virus. J Virol 1994; 68:494-9. [PMID: 8254760 PMCID: PMC236310 DOI: 10.1128/jvi.68.1.494-499.1994] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Genetic variation of the more complex retroviruses in the human T-cell leukemia virus/bovine leukemia virus (HTLV/BLV) group is less than in some other retroviral genera. To test whether reverse transcription of HTLV/BLV group members is less error prone than that of members of other groups, we developed an assay for detecting forward mutations in BLV, similar to that developed for the simpler spleen necrosis virus (SNV). We used this system to study the rates and types of mutations that occur during a single replication cycle. We found that BLV reverse transcription is approximately two and one-half times less error prone than SNV reverse transcription (4.8 x 10(-6) versus 1.2 x 10(-5) mutation per bp per cycle, respectively). The relative numbers of all types of observed mutations (that is, base pair substitutions, frameshifts, deletions, and deletions with insertions) were similar for BLV and SNV.
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Affiliation(s)
- L M Mansky
- McArdle Laboratory for Cancer Research, University of Wisconsin, Madison 53706
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24
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Yanagihara R. Geographic-specific genotypes or topotypes of human T-cell lymphotropic virus type I as markers for early and recent migrations of human populations. Adv Virus Res 1994; 43:147-86. [PMID: 8191953 DOI: 10.1016/s0065-3527(08)60048-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- R Yanagihara
- Laboratory of Central Nervous System Studies, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
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25
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GOJOBORI T, YAMAGUCHI Y, IKEO K, MIZOKAMI M. Evolution of pathogenic viruses with special reference to the rates of synonymous and nonsynonymous substitutions. Genes Genet Syst 1994. [DOI: 10.1266/ggs.69.481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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26
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Bastian I, Gardner J, Webb D, Gardner I. Isolation of a human T-lymphotropic virus type I strain from Australian aboriginals. J Virol 1993; 67:843-51. [PMID: 8093491 PMCID: PMC237438 DOI: 10.1128/jvi.67.2.843-851.1993] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
A human T-lymphotropic virus type I (HTLV-I) strain was isolated in a CD4+ T-lymphocyte culture established from a healthy seropositive Australian Aboriginal. This isolate, identified as HTLV-IMSHR-1, was detected by immunofluorescence with monoclonal antibodies, by the presence of gag-encoded protein p24 in the culture supernatant, and by cocultivation leading to infection and transformation of lymphocytes from an HTLV-I-negative donor. By using the polymerase chain reaction technique, the env gene and segments of the pol and pX regions of the proviral genome of HTLV-I(MSHR-1) were amplified and sequenced. Comparison with the envelope sequences of prototype strains revealed up to 7% divergence at the nucleotide level and 3.1 to 4.3% divergence in the predicted amino acid sequence. Phylogenetic analysis showed that the Australian and Melanesian isolates are related. Differential reactivity with monoclonal antibodies suggests that gag protein p19 of HTLV-I(MSHR-1) is also divergent. The potential for antigenic divergence between the prototype HTLV-I isolates and the Austro-Melanesian variants requires further investigation, because it would have implications for serodiagnosis and vaccine development.
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Affiliation(s)
- I Bastian
- Menzies School of Health Research, Casuarina, Darwin, Northern Territory, Australia
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27
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Palker TJ, Riggs ER, Spragion DE, Muir AJ, Scearce RM, Randall RR, McAdams MW, McKnight A, Clapham PR, Weiss RA. Mapping of homologous, amino-terminal neutralizing regions of human T-cell lymphotropic virus type I and II gp46 envelope glycoproteins. J Virol 1992; 66:5879-89. [PMID: 1326649 PMCID: PMC241464 DOI: 10.1128/jvi.66.10.5879-5889.1992] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Twelve synthetic peptides containing hydrophilic amino acid sequences of human T-cell lymphotropic virus type I (HTLV-I) envelope glycoprotein were coupled to tetanus toxoid and used to raise epitope-specific antisera in goats and rabbits. Low neutralizing antibody titers (1:10 to 1:20) raised in rabbits to peptides SP-2 (envelope amino acids [aa] 86 to 107), SP-3 (aa 176 to 189), and SP-4A (aa 190 to 209) as well as to combined peptide SP-3/4A (aa 176 to 209) were detected in the vesicular stomatitis virus-HTLV-I pseudotype assay. Higher-titered neutralizing antibody responses to HTLV-I (1:10 to 1:640) were detected with pseudotype and syncytium inhibition assays in four goats immunized with a combined inoculum containing peptides SP-2, SP-3, and SP-4A linked to tetanus toxoid. These neutralizing anti-HTLV-I antibodies were type specific in that they did not inhibit HTLV-II syncytium formation. Neutralizing antibodies in sera from three goats could be absorbed with peptide SP-2 (aa 86 to 107) as well as truncated peptides containing envelope aa 90 to 98, but not with equimolar amounts of peptides lacking envelope aa 90 to 98. To map critical amino acids that contributed to HTLV-I neutralization within aa 88 to 98, peptides in which each amino acid was sequentially replaced by alanine were synthesized. The resulting 11 synthetic peptides with single alanine substitutions were then used to absorb three neutralizing goat antipeptide antisera. Both asparagines at positions 93 and 95 were required for adsorption of neutralizing anti-HTLV-I antibodies from all three sera. Peptide DP-90, containing the homologous region of HTLV-II envelope glycoprotein (aa 82 to 97), elicited antipeptide neutralizing antibodies to HTLV-II in goats that were type specific. In further adsorption experiments, it was determined that amino acid differences between homologous HTLV-I and HTLV-II envelope sequences at HTLV-I aa 95 (N to Q) and 97 (G to L) determined the type specificity of these neutralizing sites. Thus, the amino-terminal regions of HTLV-I and -II gp46 contain homologous, linear, neutralizing determinants that are type specific.
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Affiliation(s)
- T J Palker
- Department of Medicine, Duke University Medical Center, Durham, North Carolina
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28
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Saksena NK, Sherman MP, Yanagihara R, Dube DK, Poiesz BJ. LTR sequence and phylogenetic analyses of a newly discovered variant of HTLV-I isolated from the Hagahai of Papua New Guinea. Virology 1992; 189:1-9. [PMID: 1604804 DOI: 10.1016/0042-6822(92)90675-f] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A 631-bp region of the long terminal repeat (LTR) of a variant of human T-cell lymphoma/leukemia virus type I (HTLV-I), isolated from a healthy member of a remote, recently contacted group (Hagahai) in Papua New Guinea, was sequenced and compared to LTR sequences of other members of the primate T-cell lymphoma virus group (PTLV), including HTLV-I, simian T-cell lymphoma virus (STLV-I) and HTLV-II. Sequence analysis of the LTR of this New Guinean isolate, designated as HTLV-I(PNG-1), indicated a sequence divergence of 8.4% to 10.4% from prototype Japanese HTLV-I(ATK) and other HTLV-I and STLV-I isolates and 48.6% diversity from HTLV-II. Few mutations were found in the core elements of the transcriptional enhancer regions, the TATA box promoter, and the polyadenylation signal and site. Further, the observed changes did not significantly alter the inferred stability of the Rex response element, a stem loop structure critical for polyadenylation and Rex protein binding. Dendograms based on LTR sequences indicated that the strain of virus that evolved into HTLV-I(PNG-1) diverged from the other PTLV in the distant past, just after the progenitors of STLV-I from Asia, but before the ancestors of STLV-I from Africa. By contrast, other HTLV-I isolates were found to represent strains of virus that have diverged more recently and clustered primarily according to their geographical origin. These data confirm that HTLV-I(PNG-1) is a new and distinct variant of the PTLV group. Also, our analyses suggest that both HTLV-I and STLV-I may have originated in the Indo-Malay region and eventually spread to Africa and then to the New World and Japan with horizontal transmission between man and nonhuman primates possibly occurring over thousands of years.
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Affiliation(s)
- N K Saksena
- Department of Medicine, State University of New York, Syracuse 13210
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29
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Sherman MP, Saksena NK, Dube DK, Yanagihara R, Poiesz BJ. Evolutionary insights on the origin of human T-cell lymphoma/leukemia virus type I (HTLV-I) derived from sequence analysis of a new HTLV-I variant from Papua New Guinea. J Virol 1992; 66:2556-63. [PMID: 1548780 PMCID: PMC289058 DOI: 10.1128/jvi.66.4.2556-2563.1992] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Recent studies have established the presence of human T-cell lymphoma/leukemia virus type I (HTLV-I) in Melanesia. An HTLV-I strain, PNG-1, has now been isolated from a healthy member of the Hagahai, a remote, recently contacted group in Papua New Guinea. To further characterize PNG-1, we employed polymerase chain reaction amplification with subsequent cloning and sequencing of amplified products. Sequence analyses of amplified regions of pol, env, and pX genes of this variant indicate marked heterogeneity (approximately 7%) from prototype HTLV-I. Based on available sequence data, PNG-1 is distinct from all other known HTLV-I strains and diverges from the common ancestor of HTLV-I prior to prototype isolates. The data also suggest, therefore, that HTLV-I originated in the Indo-Malay region rather than Africa.
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Affiliation(s)
- M P Sherman
- Department of Medicine, State University of New York Health Science Center at Syracuse, Syracuse 13210
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30
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Abstract
The human T-lymphotropic retroviruses HTLV-I and HIV-1/-2 share a complementary patchwork homology in which the RRE regions of HIV-1 and -2 cover 78.1% of a 169 nucleotide (nt) region (PX1,2) positioned precisely between open reading frames PX I and PX II of ATLV (HTLV-I). The sequence character of the PX1,2 region is shown to be influenced by a primordial expansion, CTC2T, originating several hundred nucleotides upstream. A second primordial expansion, AGCU(U/C), is identified and shown to represent 52.1% of the HIV-1 RRE region. It is argued that prior to the present AIDS pandemic the efficiency of the rev receptor was enhanced by an ancestral recombination event.
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31
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Abstract
RNA virus mutation frequencies generally approach maximum tolerable levels, and create complex indeterminate quasispecies populations in infected hosts. This usually favors extreme rates of evolution, although periods of relative stasis or equilibrium, punctuated by rapid change may also occur (as for other life forms). Because complex quasispecies populations of RNA viruses arise probabilistically and differentially in every host, their compositions and exact roles in disease pathogenesis are indeterminate and their directions of evolution, and the nature and timing of "new" virus outbreaks are unpredictable.
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Affiliation(s)
- J J Holland
- Department of Biology, University of California, San Diego, La Jolla 92093-0116
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32
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Gessian A, Yanagihara R, Franchini G, Garruto RM, Jenkins CL, Ajdukiewicz AB, Gallo RC, Gajdusek DC. Highly divergent molecular variants of human T-lymphotropic virus type I from isolated populations in Papua New Guinea and the Solomon Islands. Proc Natl Acad Sci U S A 1991; 88:7694-8. [PMID: 1881912 PMCID: PMC52368 DOI: 10.1073/pnas.88.17.7694] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
To determine the molecular genetic relationship between Melanesian strains of human T-lymphotropic virus type I (HTLV-I) and cosmopolitan prototype HTLV-I, we amplified by PCR, then cloned, and sequenced a 522-base-pair region of the HTLV-I env gene in DNA extracted from uncultured (fresh) and cultured peripheral blood mononuclear cells obtained from six seropositive Melanesian Papua New Guineans and Solomon Islanders, including a Solomon Islander with HTLV-I myeloneuropathy. Unlike isolates of HTLV-I from Japan, the West Indies, the Americas, and Africa, which share greater than or equal to 97% sequence homology, the Melanesian strains of HTLV-I were only 91.8%-92.5% identical with a prototype Japanese HTLV-IATK-1. The nucleotide sequence of proviral DNA from the Solomon Islander with HTLV-I myeloneuropathy also diverged markedly from that of HTLV-I isolated from Japanese patients with HTLV-I-associated myelopathy and from Jamaican patients with tropical spastic paraparesis, suggesting that these variant viruses are capable of causing disease. The HTLV-I variants from Papua New Guineans, in turn, differed by nearly 4% from the Melanesian variants from Solomon Islanders, indicating the existence of another HTLV-I quasi-species. By contrast, HTLV-I strains from two residents of Bellona Island, a Polynesian Outlier within the Solomon Islands, were closely related to cosmopolitan prototype HTLV-I (greater than or equal to 97% sequence identity), suggesting recent introduction, possibly during this century. These findings are consistent with a proto-Melanesian HTLV-I strain of archaic presence, which evolved independently of contemporary cosmopolitan strains, and pose new questions about the origin and global dissemination of HTLV-I.
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Affiliation(s)
- A Gessian
- Laboratory of Tumor Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
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33
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Fukami-Kobayashi K, Tateno Y. Robustness of maximum likelihood tree estimation against different patterns of base substitutions. J Mol Evol 1991; 32:79-91. [PMID: 1849180 DOI: 10.1007/bf02099932] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In the maximum likelihood (ML) method for estimating a molecular phylogenetic tree, the pattern of nucleotide substitutions for computing likelihood values is assumed to be simpler than that of the actual evolutionary process, simply because the process, considered to be quite devious, is unknown. The problem, however, is that there has been no guarantee to endorse the simplification. To study this problem, we first evaluated the robustness of the ML method in the estimation of molecular trees against different nucleotide substitution patterns, including Jukes and Cantor's, the simplest ever proposed. Namely, we conducted computer simulations in which we could set up various evolutionary models of a hypothetical gene, and define a true tree to which an estimated tree by the ML method was to be compared. The results show that topology estimation by the ML method is considerably robust against different ratios of transitions to transversions and different GC contents, but branch length estimation is not so. The ML tree estimation based on Jukes and Cantor's model is also revealed to be resistant to GC content, but rather sensitive to the ratio of transitions to transversions. We then applied the ML method with different substitution patterns to nucleotide sequence data on tax gene from T-cell leukemia viruses whose evolutionary process must have been more complicated than that of the hypothetical gene. The results are in accordance with those from the simulation study, showing that Jukes and Cantor's model is as useful as a more complicated one for making inferences about molecular phylogeny of the viruses.
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