Human T-lymphotropic virus 2

A virus closely related to HTLV-I, human T-lymphotropic virus 2 (HTLV-II) shares approximately 70% genomic homology (structural similarity) with HTLV-I.

It is found predominantly in Native Americans,^[1] and South American Indian groups. And also in Asian countries. More common in Japan and Korea.^{[citation needed]} It can be passed down from mother to child through breastmilk and genetically as well from either parent.

HTLV-II entry in target cells is mediated by the glucose transporter GLUT1.^[2]

Virology

HTLV-1 and HTLV-2 share broad similarities in their overall genetic organization and expression pattern, but they differ substantially in their pathogenic properties.^[3] The viruse utilizes the GLUT-1 and NRP1 cellular receptors for their entry, although HTLV-1, but not HTLV-2, is dependent on heparan sulfate proteoglycans. Cell-to-cell transmission is essential for virus replication and occurs through the formation of a virological synapse^[4]

Transmission

Perinatal transmission and breastfeeding and through blood transfusion, sexual contact, and use of intravenous drugs.^[5]

Symptoms

Human T- leukemia , type 2 (HTLV-2) generally causes no signs or symptoms. Although HTLV-2 has not been definitively linked with any specific health problems, scientists suspect that some affected people may later develop neurological problems such as:^[6][7]

• Sensory neuropathies (conditions that affect the nerves that provide feeling)
• Gait abnormalities
• Bladder dysfunction
• Mild cognitive impairment
• Motor abnormalities (loss of or limited muscle control or movement, or limited mobility)

• Erectile dysfunction

Although evidence is limited, there may also be a link between HTLV-2 and chronic lung infections (i.e. pneumonia and bronchitis), asthma and dermatitis.^[8]

Epidemology

HTLV-1 and HTLV-2 are both involved in actively spreading epidemics, affecting 15-20 million people worldwide. ^[4] In the United States, the overall prevalence is 22 per 100,000 population, with HTLV-2 more common than HTLV-1. Data collection performed from 2000-2009 among US blood donors has shown a general decline since the 1990s.^[9]

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 neurological disease and may cause chronic lung problems.

An impact on platelet count has been observed.^[10]

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.^[11] 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.^[12] The cause of hairy cell leukemia is not known, but it is no longer believed to be related to viral infections.

References

External links

• "Human T-lymphotropic virus 2". NCBI Taxonomy Browser. 11909.
• International Retrovirology Association
• Human+T-lymphotropic+virus+2 at the U.S. National Library of Medicine Medical Subject Headings (MeSH)

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