Human T-lymphotropic virus

From Infogalactic: the planetary knowledge core
(Redirected from HTLV)
Jump to: navigation, search
Human T-lymphotropic virus
Virus classification
Group:
Group VI (ssRNA-RT)
Family:
Retroviridae
Subfamily:
Orthoretrovirinae
Genus:
Deltaretrovirus
Species:
Simian T-lymphotropic virus
Serotypes

Human T-lymphotropic virus

Lua error in Module:Taxonbar/candidate at line 22: attempt to index field 'wikibase' (a nil value).

The human T-lymphotropic virus or human T-cell lymphotropic virus (HTLV) family of viruses are a group of human retroviruses that are known to cause a type of cancer called adult T-cell leukemia/lymphoma and a demyelinating disease called HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP). The HTLVs belong to a larger group of primate T-lymphotropic viruses (PTLVs). Members of this family that infect humans are called HTLVs, and the ones that infect Old World monkeys are called Simian T-lymphotropic viruses (STLVs). To date, four types of HTLVs (human T-lymphotropic virus 1 [HTLV-I], human T-lymphotropic virus 2 [HTLV-II], HTLV-III, and HTLV-IV) and four types of STLVs (STLV-I, STLV-II, STLV-III, and STLV-V) have been identified. HTLV types HTLV-1 and HTLV-2 viruses are the first retroviruses which were discovered. Both belong to the oncovirus subfamily of retroviruses and can transform human lymphocytes so that they are self-sustaining in vitro.[1] The HTLVs are believed to originate from intraspecies transmission of STLVs. The original name for HIV, the virus that causes AIDS, was HTLV-III. The HTLV-1 genome is diploid, composed of two copies of a single-stranded RNA virus whose genome is copied into a double-stranded DNA form that integrates into the host cell genome, at which point the virus is referred to as a provirus. A closely related virus is bovine leukemia virus BLV.

HTLV-I

<templatestyles src="Module:Hatnote/styles.css"></templatestyles>

Main article: Human T-lymphotropic virus 1

HTLV-I is an abbreviation for human T-cell lymphotropic virus type 1, also called human T-cell leukemia type 1, a virus that has been seriously implicated in several kinds of diseases, including HTLV-I-associated myelopathy, and as a virus cancer link for leukemia (see adult T-cell leukemia/lymphoma).HTLV-1 has six reported subtypes (subtypes A to F). The great majority of infections are caused by the cosmopolitan subtype A.[2] HTLV was discovered by Luc Antoine Montagnier (born 18 August 1932) a French virologist along with Françoise Barré-Sinoussi and Harald zur Hausen. Robert Gallo and colleagues were also involved in 1980.[3] Between 1 in 20 and 1 in 25 infected persons are thought to develop cancer as a result of the virus.[citation needed].[4] HTLV-1 infection is thought to spread only through dividing cells since, reverse transcriptase generates proviral DNA from genomic viral RNA, and the provirus is integrated into the host genome by viral integrase after transmission. Therefore, the quantification of provirus reflects the number of HTLV-1-infected cells. So, an increase in numbers of HTLV-1-infected cells using cell division, by actions of accessory viral genes, especially tax, may provide an enhancement of infectivity tax expression induces proliferation, inhibits the apoptosis of HTLV-1-infected cells and, conversely, evokes the host immune response, including cytotoxic T cells, to kill virus-infected cells.[5]

HTLV-II

<templatestyles src="Module:Hatnote/styles.css"></templatestyles>

Main article: Human T-lymphotropic virus 2

A virus closely related to HTLV-I, also discovered by Robert Gallo and colleagues,[6] HTLV-II shares approximately 70% genomic homology (structural similarity) with HTLV-I.

HTLV-III is currently the name used to describe another virus related to HTLV-I and HTLV-II.[citation needed] "HTLV-IV" has been used to describe recently characterized viruses.[7][8][9]

These viruses were discovered in 2005 in rural Cameroon, and were, it is presumed, transmitted from monkeys to hunters of monkeys through bites and scratches.

  • HTLV-III is similar to STLV-III (Simian T-lymphotropic virus 3).[10] Multiple strains have been identified.[11] It expresses gag, pol, and env, among other proteins.[12]
  • HTLV-IV does not resemble any known virus.

It is not yet known how much further transmission has occurred among humans, or whether the viruses can cause disease.

The use of these names can cause some confusion, because the name HTLV-III was one of the names for HIV in early AIDS literature, but has since fallen out of use.[13] The name HTLV-IV has also been used to describe HIV-2.[14] A large Canadian study documented this confusion among healthcare workers, where >90% of HTLV tests ordered by physicians were actually intended to be HIV tests.[15]

Transmission

HTLV-I and HTLV-II can be transmitted sexually,[16][17] by blood to blood contact (e.g. by blood transfusion or sharing needles when using drugs)[18][19] and via breast feeding.[20]

Research

While there is no present licensed vaccine, there are many factors which make a vaccine against HTLV-1 feasible. The virus displays relatively low antibody production variability, natural immunity does occur in humans, and experimental vaccination using envelope antigens has been shown to be successful in animal models. Four HTLVs are well established. HTLV-1 and HTLV-2 are both involved in actively spreading epidemics, affecting 15-20 million people worldwide. HTLV-1 is the more clinically significant of the two, as it has been proven to be the etiologic agent of multiple disorders. At least 500,000 of the individuals infected with HTLV-1 eventually develop an often rapidly fatal leukemia, while others will develop a debilitative myelopathy, and yet others will experience uveitis, infectious dermatitis, or another inflammatory disorder. HTLV-2 is associated with milder neurologic disorders and chronic pulmonary infections. The novel HTLV-3 and HTLV-4 have been isolated only in a few cases; no specific illnesses have yet been associated with these viruses. Plasmid DNA vaccines elicit potent and protective immune responses in numerous small-animal models of infectious diseases. However, their immunogenicity in primates appears less potent. In the United States, HTLV-I/II seroprevalence rates among volunteer blood donors average 0.016 percent. Approximately half of HTLV-I/II-seropositive blood donors nationwide are infected with HTLV-I. HTLV-I infected donors most often report a history of birth in HTLV-I endemic countries or sexual contact with persons from the Caribbean or Japan. In the past two decades a large initiative has been put forth to understand the biological and pathogenic properties of the human T-cell lymphotropic virus type 1 (HTLV-1); this has ultimately led to the development of various experimental vaccination and therapeutic strategies to combat HTLV-1 infection. These strategies include the development of envelope glycoprotein derived B-cell epitopes for the induction of neutralizing antibodies, as well as a strategy to generate a multivalent cytotoxic T-lymphocyte (CTL) response against the HTLV-1 Tax antigen. A vaccine candidate that can elicit or boost anti-gp46 neutralizing antibody response may have a potential for prevention and therapy against HTLV-1 infection.[21] Potential treatments include prosultiamine, a vitamin B-1 derivative, which has been shown to reduce viral load and symptoms;[22] azacytidine, an anti-metabolite, which has been credited with the cure of a patient in Greece;[23] tenofovir disoproxil (TDF), a reverse-transcriptase inhibitor used for HIV; cepharanthine, an alkaloid from stephania cepharantha hayata;[24] and phosphonated carbocyclic 2'-oxa-3'aza nucleosides (PCOANs).[25] A newer formulation of TDF, called tenofovir alafenamide (TAF), also has promise as a treatment with less toxicity.

References

  1. ↑ [1]
  2. ↑ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2901658/
  3. ↑ Detection and isolation of type C retrovirus particles from fresh and cultured lymphocytes of a patient with cutaneous T-cell lymphoma. Poiesz BJ, Ruscetti FW, Gazdar AF, Bunn PA, Minna JD, Gallo RC. Proc Natl Acad Sci U S A. 1980 Dec; 77(12):7415–9
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Taylor, G. P., and M. Matsuoka. 2005. Natural history of adult T-cell leukemia/lymphoma and approaches to therapy, Oncogene 24:6047-6057[PubMed]
  6. ↑ Kalyanaraman, V.S., Sarngadharan, M.G., Robert Guroff, M., Miyoshi, I., Blayney, D., Golde, D., and Gallo, R.C.: A new subtype of human T cell leukemia virus (HTLV II) associated with a T cell variant of hairy cell leukemia. Science 218: 571–573, 1982.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Human T-Lymphotropic Virus Type III at the US National Library of Medicine Medical Subject Headings (MeSH)
  13. ↑ Human T Lymphotropic Virus Type IV at the US National Library of Medicine Medical Subject Headings (MeSH)
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ http://www.htlv1.eu/htlv_one.html#how
  18. ↑ http://www.htlv1.eu/htlv_two.html#how
  19. ↑ Coovadia HM et al. Mother-to-child transmission of HIV-1 infection during exclusive breastfeeding in the first 6 months of life :An intervention cohort study" Lancet 2007, 369(9567) 1107-1116.
  20. ↑ Neutralizing antibodies against human T cell leukemia virus type-I (HTLV-1) eradicate HTLV-1 in combination with autologous peripheral blood mononuclear cells via antibody-dependent cellular cytotoxicity while preventing new infection
  21. ↑ Nervous System Disease: A New Outlet for an Old Drug?
  22. ↑ Antiretroviral activity of 5-azacytidine during treatment of a HTLV-1 positive myelodysplastic syndrome with autoimmune manifestations
  23. ↑ Synergistic inhibition of HTLV-1-infected cell proliferation by combination of cepharanthine and a tetramethylnaphthalene derivative
  24. ↑ Lua error in package.lua at line 80: module 'strict' not found.

External links

Retrieved from "https://infogalactic.com/w/index.php?title=Human_T-lymphotropic_virus&oldid=722304515"