View source for Biology:Human T-lymphotropic virus 2

{{Short description|Species of virus}}
{{Virusbox
| parent = Deltaretrovirus
| species = Primate T-lymphotropic virus 2
}}

A [[Biology:Virus|virus]] closely related to HTLV-I, '''human T-lymphotropic virus 2''' ('''HTLV-II''') shares approximately 70% genomic [[Biology:Homology modeling|homology]] (structural similarity) with [[Biology:Human T-lymphotropic virus 1|HTLV-I.]] It was discovered by Robert Gallo and colleagues.<ref name="Geskin 423–431">{{cite journal|last1=Geskin|first1=Larisa J.|last2=Pomerantz|first2=Rebecca G.|last3=Mirvish|first3=Ezra D.|date=2011-02-01|title=Infectious agents in cutaneous T-cell lymphoma|url=https://www.jaad.org/article/S0190-9622(09)02307-X/abstract|journal=Journal of the American Academy of Dermatology|language=en|volume=64|issue=2|pages=423–431|doi=10.1016/j.jaad.2009.11.692|pmid=20692726|pmc=3954537|issn=0190-9622}}</ref><ref>{{cite web|url=http://www.timelinesdb.com/listevents.php?subjid=378&title=AIDS|title=Robert gallo discovers htlv2 and 1|access-date= 23 February 2019}}</ref>

HTLV-2 is prevalent among the indigenous populations in [[Earth:Africa|Africa]] and the Indian-American tribes in Central and South America as well as among drug users in [[Earth:Europe|Europe]] and [[Earth:North America|North America]]<ref name="Ciminale 398">{{cite journal|last1=Ciminale|first1=Vincenzo|last2=Rende|first2=Francesca|last3=Bertazzoni|first3=Umberto|last4=Romanelli|first4=Maria G.|date=2014-07-29|title=HTLV-1 and HTLV-2: highly similar viruses with distinct oncogenic properties|journal=Frontiers in Microbiology|volume=5|pages=398|doi=10.3389/fmicb.2014.00398|issn=1664-302X|pmc=4114287|pmid=25120538|doi-access=free}}</ref> It can be passed down from [[Medicine:Vertically transmitted infection|mother to child]] through breastmilk and genetically as well from either parent.

HTLV-II entry in target cells is mediated by the [[Biology:Glucose transporter|glucose transporter]] [[Biology:GLUT1|GLUT1]].<ref name=Manel>{{cite journal |vauthors=Manel N, Kim FJ, Kinet S, Taylor N, Sitbon M, Battini JL |title=The ubiquitous glucose transporter GLUT-1 is a receptor for HTLV |journal=Cell |volume=115 |issue=4 |pages=449–59 |date=November 2003 |pmid=14622599 |doi= 10.1016/S0092-8674(03)00881-X|doi-access=free }}</ref>[[File:HTLV Phylogeny.jpg|thumb|A phylogeny of the subtypes of HTLV and their relationships between endogenous and exogenous retroviruses in the human genome. HERV = human endogenous retrovirus, SFV = simian foamy virus]]

== Virology ==
[[Biology:Human T-lymphotropic virus 1|HTLV-1]] and HTLV-2 share broad similarities in their overall genetic organization and expression pattern, but they differ substantially in their [[Biology:Pathogen|pathogen]]ic properties.<ref name="Ciminale 398"/>  The virus utilizes the [[Biology:GLUT1|GLUT-1]] and [[Biology:Neuropilin 1|NRP1]] cellular receptors for their entry, although [[Biology:Human T-lymphotropic virus 1|HTLV-1]], but not HTLV-2, is dependent on heparan sulfate proteoglycans. Cell-to-cell transmission is essential for virus [[Biology:Viral replication|replication]] and occurs through the formation of a [[Biology:Viral synapse|virological synapse]].<ref name="Ciminale 398"/> The family of Human T-lymphotropic virus (Figure 2) can be further categorized into four sub types. The figure also divides the retroviruses into exogenous and endogenous. [[Biology:Retrovirus|Retrovirus]]es can exist as two different forms: endogenous which consist of normal genetic components and exogenous which are horizontally transferred genetic components that are usually infectious agents that cause disease i.e. [[Biology:HIV|HIV]]. In (Figure 3) open reading frames (ORF) are shown which can if translated can predict which genes will be present and this can help to better understand human [[Biology:Retrovirus|retrovirus]]es. Of the four subtypes, HTLV-2 may be linked to [[Medicine:Cutaneous T cell lymphoma|Cutaneous T-cell lymphoma]] (CTCL).<ref name="jaad.org">{{cite web|url=https://www.jaad.org/action/captchaChallenge?redirectUri=%2Farticle%2FS0190-9622%2809%2902307-X%2Ffulltext|title=Journal of the American Academy of Dermatology|website=www.jaad.org|access-date=2019-02-22}}</ref> In one study involving cultured lymphocytes from patients with [[Medicine:Mycosis fungoides|mycosis fungoides]] (Figure 1), [[Biology:Polymerase chain reaction|PCR]] amplification showed gene sequences of HTLV-II. This finding may suggest a possible correlation with HTLV-2 and CTCL. Further research and studies must be conducted to show a positive relationship.<ref name="Geskin 423–431"/>

== Transmission ==
[[Medicine:Vertically transmitted infection|Perinatal transmission]] and breastfeeding and through [[Medicine:Blood-borne disease|blood transfusion]], sexual contact, and use of intravenous drugs.<ref name="Ciminale 398"/>

=== Epidemiology ===
[[Biology:Human T-lymphotropic virus 1|HTLV-1]] and HTLV-2 are both involved in actively spreading [[Medicine:Epidemic|epidemic]]s, affecting 15-20 million people worldwide. <sup>[4]</sup> In the {{wipe|United States}}, the overall prevalence is 22 per 100,000 population, with HTLV-2 more common than [[Biology:Human T-lymphotropic virus 1|HTLV-1]]. Data collection performed from 2000 to 2009 among US [[Medicine:Blood donation|blood donors]] has shown a general decline since the 1990s.<ref name="emedicine.medscape.com">{{cite web|title=Human T-Cell Lymphotropic Viruses (HTLV)|url=https://emedicine.medscape.com/article/219285-overview|website=Medscape|access-date=22 February 2019}}</ref>

== Symptoms ==
Human T- leukemia, type 2 (HTLV-2) generally causes no signs or [[Medicine:Symptom|symptom]]s. Although HTLV-2 has not been definitively linked with any specific [[Disease|health problems]], scientists suspect that some affected people may later develop [[Medicine:Neurological disorder|neurological problems]] such as:<ref>{{cite web|url=https://rarediseases.org/rare-diseases/htlv-type-i-and-type-ii/|title=HTLV Type I and Type II|website=NORD (National Organization for Rare Disorders)|language=en-US|access-date=2019-02-22}}</ref><ref name="emedicine.medscape.com"/>
* Sensory neuropathies (conditions that affect the [[Biology:Nerve|nerve]]s that provide feeling)
* [[Medicine:Gait abnormality|Gait abnormalities]]
* [[Biology:Urinary bladder|Bladder]] dysfunction
* Mild [[Medicine:Cognitive impairment|cognitive impairment]]
* [[Engineering:Motor control|Motor abnormalities]] (loss of or limited muscle control or movement, or limited mobility)
* [[Medicine:Erectile dysfunction|Erectile dysfunction]]
* [[Medicine:Mycosis fungoides|Mycosis fungoides]]

[[File:Neck of a woman suffering from mycosis fungoides of the skin Wellcome L0061976.jpg|alt=|thumb|Figure 1. ''Mycosis fungoides'', a skin disease showing nodules and plaques composed of lymphocytes spread across the skin, has been associated with HTLV-II infection<ref name="jaad.org"/>]]
Although evidence is limited, there may also be a link between HTLV-2 and chronic lung infections (i.e. [[Medicine:Pneumonia|pneumonia]] and [[Medicine:Bronchitis|bronchitis]]), [[Medicine:Asthma|asthma]] and [[Medicine:Dermatitis|dermatitis]].<ref name="NIH">{{cite web|url=https://rarediseases.info.nih.gov/diseases/9783/human-t-cell-leukemia-virus-type-2|title=Human T-cell leukemia virus type 2|publisher=US Department of Health and Human Services {{!}} Genetic and Rare Diseases Information Center (GARD) – an NCATS Program|access-date=2019-02-22}} {{PD-notice}}</ref>

===Clinical significance===
HTLV-II has not been clearly linked to any disease, but has been associated with several cases of myelopathy/tropical spastic paraparesis (HAM/TSP)- like [[Medicine:Neurological disorder|neurological disease]] and may cause [[Medicine:Respiratory disease|chronic lung problems.]]{{citation needed|date=November 2022}}

An impact on [[Biology:Platelet|platelet count]] has been observed.<ref name="pmid18755983">{{cite journal  |vauthors=Bartman MT, Kaidarova Z, Hirschkorn D, etal |title=Long-term increases in lymphocytes and platelets in human T-lymphotropic virus type II infection |journal=Blood |volume=112 |issue=10 |pages=3995–4002 |date=November 2008 |pmid=18755983 |pmc=2581993 |doi=10.1182/blood-2008-05-155960 }}</ref>

In the 1980s, HTLV-2 was identified in a patient with an unidentified T cell lymphoproliferative disease that was described as having characteristics similar to the B cell disorder, hairy cell leukemia.<ref name="pmid6981847">{{cite journal |vauthors=Kalyanaraman VS, Sarngadharan MG, Robert-Guroff M, Miyoshi I, Golde D, Gallo RC |title=A new subtype of human T-cell leukemia virus (HTLV-II) associated with a T-cell variant of hairy cell leukemia |journal=Science |volume=218 |issue=4572 |pages=571–3 |date=November 1982 |pmid=6981847 |doi= 10.1126/science.6981847|bibcode=1982Sci...218..571K }}</ref>  HTLV-2 was identified in a second patient with a T cell lymphoproliferative disease; this patient later developed hairy cell leukemia, but HTLV-2 was not found in the hairy cell clones.<ref name="pmid2827811">{{cite journal |vauthors=Rosenblatt JD, Giorgi JV, Golde DW, etal |title=Integrated human T-cell leukemia virus II genome in CD8 + T cells from a patient with "atypical" hairy cell leukemia: evidence for distinct T and B cell lymphoproliferative disorders |journal=Blood |volume=71 |issue=2 |pages=363–9 |date=February 1988 |pmid=2827811 |doi=10.1182/blood.V71.2.363.363 |url=https://ashpublications.org/blood/article/71/2/363/165559/Integrated-human-T-cell-leukemia-virus-II-genome |doi-access=free |access-date=10 July 2020 }}</ref>  The cause of hairy cell leukemia is not known, but it is no longer believed to be related to [[Medicine:Viral disease|viral infections]].{{citation needed|date=November 2022}}

== Treatment ==
There are few [[Chemistry:Therapy|treatments]]<ref>{{cite journal|last1=Gotuzzo|first1=Eduardo|last2=Vanham|first2=Guido|last3=Vandamme|first3=Anne-Mieke|last4=Dooren|first4=Sonia Van|last5=González|first5=Elsa|last6=Verdonck|first6=Kristien|date=2007-04-01|title=Human T-lymphotropic virus 1: recent knowledge about an ancient infection|url=https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(07)70081-6/abstract|journal=The Lancet Infectious Diseases|language=en|volume=7|issue=4|pages=266–281|doi=10.1016/S1473-3099(07)70081-6|issn=1473-3099|pmid=17376384}}</ref> including [[Medicine:Chemotherapy|chemotherapy]] and antiretrovirals that can slow the [[Biology:Viral load|viral load]] but no cure or definitive treatment exists for HTLV-2.<ref name="NIH"/>

=== Diagnosis ===
Human T- leukemia, type 2 (HTLV-2) is usually diagnosed based on blood tests that detect to the virus. However, HTLV-2 is often never suspected or [[Medicine:Diagnosis|diagnosed]] since most people [[Medicine:Asymptomatic|never develop any signs or symptoms of the infection]]. [[Medicine:Diagnosis|Diagnosis]] may occur during  for [[Medicine:Blood donation|blood donation]], testing performed due to an [[Medicine:Infection|infection]], or a [[Medicine:Complete blood count|work-up]] for an HTLV-2-associated medical problems.<ref name="NIH"/>

=== Prevention ===
Due to there being no [[Medicine:Cure|cure]] for HTLV II the [[Medicine:Preventive healthcare|prevention]] is focused on early detection and preventing the spread of HTLV-2 to others.  blood donors, promoting safe sex and discouraging needle sharing can decrease the number of new infections. [[Medicine:Vertically transmitted infection|Mother-to-child transmission]] can be reduced by screening [[Medicine:Pregnancy|pregnant]] women so infected mothers can avoid [[Social:Breastfeeding|breastfeeding]].<ref name="NIH"/>

=== Prognosis ===
The long-term [[Medicine:Prognosis|outlook]] for most people infected with HTLV-2 is good. Infection with HTLV-2 is [[Medicine:Chronic condition|lifelong]], but 95% of affected people have [[Medicine:Asymptomatic|no signs or symptoms of the condition]]. Although, HTLV-2-related health problems tend to be significantly milder than those associated with [[Biology:Human T-lymphotropic virus 1|HTLV1]].<ref name="NIH"/>

==References==
{{Reflist}}

==External links==
* {{cite web |title=''Human T-lymphotropic virus 2'' |work=NCBI Taxonomy Browser |url=https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=11909 |id=11909}}
* [http://htlv.net International Retrovirology Association]
* {{MeshName|Human+T-lymphotropic+virus+2}}

{{Retroviruses}}
{{Zoonotic viral diseases}}
{{Taxonbar|from=Q2720986}}

{{DEFAULTSORT:Human T-Lymphotropic Virus 2}}
[[Category:Deltaretroviruses]]

{{Sourceattribution|Human T-lymphotropic virus 2}}