HTLV2
A Microbial Biorealm page on the genus HTLV2
Classification
Viruses; Retro-transcribing viruses; Retroviridae; Orthoretrovirinae; Deltaretrovirus; Primate T-lymphotrophic virus 2 (1).
Description and significance
Describe the disease caused by this organism if it is a pathogen, or the natural macroscopic "field guide" appearance and habitat of your organism if it is not. What is or has been the impact your organism on human history or our environment?. How does it do this? How have we harnessed this power, or tried to prevent it? In other words, how do you know it if you see it, and how does its presence influence humans in the present, and historically?
Genome structure
HTLV-2’s genome is completely sequenced. It has a linear chromosome of single stranded RNA with seven genes, which include HTLV2gp1-6 and HTLV2gs1. It consists of 8,952 nucleotides and has a GC content of 53%. It shows approximately 60% homology to the human T-cell leukemia virus type I. This homology makes it an important research model of deltaretroviruses. Its genomic structure is as follows: LTR-gag-protease-pol-env-X-LTR. The protease gene encodes a protease that can cleave the precursor Gag protein encoded by gag. The pol gene encodes for 982 amino acids. The env gene encodes for 486 amino acids. The X region of the gene is likely responsible for the replication of the virus. The high ratio of synonomous to nonsynomous changes to HTLV-2s genome from HTLV-1’s genome suggests that ability of this virus to produce certain amino acids was not significantly changed.
include Lairmore reference in this section
Cell structure, metabolism & life cycle
Provide a physical and biochemical description of the organism. What kind of organism is it, what does it look like, how is it built, what are its metabolic properties, how can it be identified, what is it's life cycle, &c. In other words, describe the organism from its perspective.
Ecology (including pathogenesis)
HTLV-2 was first discovered in 1982 in a patient with hairy-cell leukemia, a rare type of leukemia that most often affects men but can affect women. Subsequent studies were unable to demonstrate that HTLV-2 was the cause of the leukemia, but it has been implicated in certain neurological disorders and increased bacterial infections in the bloodstreams of AIDS patients. In a recent study examining the incidence of AIDS patients co-infected with HTLV-2, patients infected with both viruses were more likely to develop peripheral neuropathy than those only infected with one of the viruses. While other studies have demonstrated similar increased risk of certain neurological disorders with HTLV-2 infection, these studies are confounded with the presence of other viruses. (The rate of co-infection also suggests that the weakened immune response of AIDS patients is allows the HTLV-2 virus to infect the individual, as it rarely presents itself in patients by itself.) These suggested neurological disorders caused by HTLV-2 include HAM/TSP, multiple system atrophy (MSA), and ataxia. HAM/TSP most often results in muscle stiffness and weakness and increased frequency of urination. The symptoms of MSA are very similar to Parkinson's disease. Ataxia refers to a loss of muscle coordination. As a retrovirus, HTLV-2 bind to specific receptors on the host cell and replicate by releasing reverse transcriptase to create DNA from its single stranded RNA genome. HTLV-2 alters gene expression that increases the production of lymphocytes and ultimately changes the structure of its most prominent target, the CD8+ lymphocyte. It is not understand how the virus is able to change the structure of the cell. The HTLV-2 virus has multiple modes of transmission, related to its ability to stay attached to its host cell even after replication. Some studies state that is it not passed in utero while others suggest that it does, but it is clear that it can pass from mother to child through breast milk. Up to 25% of children with mothers who have the disease and breastfeed will contract the virus. It is sexually transmitted and is more easily transmitted from a male to a female than a female to a male. It is also commonly transmitted through needle sharing; this is the prominent mode of transmission in North America, Europe, South America, and Asia. It is endemic to certain Amerindian tribes, such as the Guahibo Indians of Venezuela. It is also endemic to the Bakola pygmy tribe of Africa, as compared to local African tribes. The endemism if the virus is likely due to its vertical transmission through breast feeding. Because the overall incidence of HTLV-2 infection is so rare, and because it affects very specific subsets of the world population, the pathogenesis of HTLV-2 is unclear. Recent research has demonstrated that the protein Tax stimulates two interleukins (IL-14 and IL-2), which increases T-cell growth and may be responsible for the change in cell structure. This causes leukogenesis, which may explain why the HTLV-2 virus was first discovered in a leukemia patient though the virus could not be isolated from any other patients with the same type of leukemia. The tax protein differs among different subtypes (a, b, c) of the virus, but it is not known if this is related to pathogenesis. It is probable that the pathogenesis of HTLV-2 is similar to that of HTLV-1, in which the increase in T-cell proliferation leads to T-cell killing by the body's immune system which releases damaging cytokines and lymphokines. This response is typical of an auto-immune disease.
References: Kalyanaraman, V.S., Sarngadharan, M.G., Robert-Guroff, Marjorie, Miyoshi, Isao, Blayney, Douglas, Golde, David, Gallo, Robert C. “A New Subtype of Human-T-Cell Leukemia Virus (HTLV-II) Associated with a T-Cell Variant of Hairy Cell Leukemia. Science. 1982. Volume 218 (4572): 571-573. Leon-Ponte, Matilde, Noya, Oscar, Bianco, Nicolas, De Perz, Gloria Echeverria. "Highly endemic Human T-Lymphotrophic Virus Type II (HTLV-II) Infection in a Venezuelan Guahibo Amerindian Group" J. Acquir Immune Defic Syndr. 1996. Volume 13(3):281-286. http://journals.lww.com/jaids/Fulltext/1996/11010/Highly_Endemic_Human_T_Lymphotropic_Virus_Type_II.11.aspx
Boxus M, Twizere JC, Legros S, Dewulf JF, Kettmann R, Willems L. "The HTLV-1 Tax interactome." Retrovirology. Volume 5(76).
Dooneief G, Marlink R, Bell K, et al. "Neurologic consequences of HTLV-II infection in injection-drug users." Neurology.1996. Volume 46(6):1556-1560.
Araujo, A. Hall, William W. "Human T-Lymphotrophic Virus Type II and Neurological Disease." 2004. Annals of Neurology.Volume 56(1). http://onlinelibrary.wiley.com/doi/10.1002/ana.20126/pdf
Lairmore, Michael D., Montgomery, Andy. "Isolation and Confirmation of Human T-Cell Leukemia Virus Type 2 from Peripheral Blood Mononuclear Cells." Methods Mol Biol. 2005. Volume 304:113-123. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3060566/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3060566/pdf/nihms183536.pdf
Szczypinska, E.M. "Human T-Cell Lymphotrophic Viruses." Medscape Reference. 2009. http://emedicine.medscape.com/article/219285-overview#a0104
Zehender, G., Colastante C, Santambrogio S, De Maddalena C, Massetto B, Cavilli B, Jacchetti G, Fasan M, Adorni F, Osio M, Moroni M, Galli M. "Increased risk of developing peripheral neuropathy in patients co-infected with HIV-1 and HTLV-2." 2002. J Acquir Immune Defic Syndr. Volume 31(4): 440-447.
http://www.ncbi.nlm.nih.gov/pubmed?term=Increased%20Risk%20of%20Developing%20Peripheral%20Neuropathy%20in%20Patients%20Coinfected%20With%20HIV-1%20and%20HTLV-2.%5BArticle%5D
Mauclere P, Afonso PV, Meertens L, Plancoulaine S, Calattini S, Froment A, Van Beveren M, de The G, Quintana-Murci L, Mahieux R, Gessain A. “HTLV-2B strains, similar to those found in several Amerindian tribes, are endemic in African Bakola Pygmies. Journal of Infectious Diseases. 2011. Volume 203(9):1316-1323. http://www.ncbi.nlm.nih.gov.lucy2.skidmore.edu:2048/pubmed/21459818 • HTLV-II endemic to only certain populations ex. African bagola pygmies
Pathology and Pathogenesis of Human Viral Diseasehttp://books.google.com/books?id=uy8pUQmu5FwC&pg=PA249&lpg=PA249&dq=HTLV-2+pathology&source=bl&ots=z7FOL63QYW&sig=_U_38_uzubh_sWo4fSS0BchWWPE&hl=en&ei=AXyvTr-sFobw0gGG9Mm5AQ&sa=X&oi=book_result&ct=result&resnum=1&ved=0CB8Q6AEwAA#v=onepage&q=HTLV-2%20pathology&f=false
Interesting feature
Describe in detail one particularly interesting aspect of your organism or it's affect on humans or the environment.
References
1. NCBI Taxonomy Browser. Human T-lymphotrophic virus 2. http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=11909&lvl=3&lin=f&keep=1&srchmode=1&unlock
2. Leon-Ponte, Matilde, Noya, Oscar, Bianco, Nicolas, De Perz, Gloria Echeverria. "Highly endemic Human T-Lymphotrophic Virus Type II (HTLV-II) Infection in a Venezuelan Guahibo Amerindian Group" J. Acquir Immune Defic Syndr. 1996. Volume 13(3):281-286.
3. Boxus M, Twizere JC, Legros S, Dewulf JF, Kettmann R, Willems L. "The HTLV-1 Tax interactome." Retrovirology. Volume 5(76). Dooneief G, Marlink R, Bell K, et al. "Neurologic consequences of HTLV-II infection in injection-drug users." Neurology.1996. Volume 46(6):1556-1560.
4. Araujo, A. Hall, William W. "Human T-Lymphotrophic Virus Type II and Neurological Disease." 2004. Annals of Neurology.Volume 56(1). http://onlinelibrary.wiley.com/doi/10.1002/ana.20126/pdf
5. Lairmore, Michael D., Montgomery, Andy. "Isolation and Confirmation of Human T-Cell Leukemia Virus Type 2 from Peripheral Blood Mononuclear Cells." Methods Mol Biol. 2005. Volume 304:113-123.
6. Szczypinska, E.M. "Human T-Cell Lymphotrophic Viruses." Medscape Reference. 2009. http://emedicine.medscape.com/article/219285-overview#a0104
7. Zehender, G., Colastante C, Santambrogio S, De Maddalena C, Massetto B, Cavilli B, Jacchetti G, Fasan M, Adorni F, Osio M, Moroni M, Galli M. "Increased risk of developing peripheral neuropathy in patients co-infected with HIV-1 and HTLV-2." 2002. J Acquir Immune Defic Syndr. Volume 31(4): 440-447.
8. Mauclere P, Afonso PV, Meertens L, Plancoulaine S, Calattini S, Froment A, Van Beveren M, de The G, Quintana-Murci L, Mahieux R, Gessain A. “HTLV-2B strains, similar to those found in several Amerindian tribes, are endemic in African Bakola Pygmies. Journal of Infectious Diseases. 2011. Volume 203(9):1316-1323.
