Human T-lymphotropic virus 2
A virus closely related to HTLV-I, human T-lymphotropic virus 2 shares approximately 70% genomic homology with HTLV-I. It was discovered by Robert Gallo and colleagues.
HTLV-2 is prevalent in Africa and among Indigenous peoples in Central and South America, as well as among drug users in Europe and North America. It can be passed down from mother to child through breast milk, and through blood transfusions, sexual contact, and use of intravenous drug usage.
HTLV-II entry in target cells is mediated by the glucose transporter GLUT1.
Virology
and HTLV-2 share broad similarities in their overall genetic organization and expression pattern, but they differ substantially in their pathogenic properties. The virus 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 the virus replication and occurs through the formation of a virological synapse. The family of Human T-lymphotropic virus can be further categorized into four subtypes. The figure also divides the retroviruses into exogenous and endogenous. Retroviruses can exist in two different forms: endogenous which consists of normal genetic components and exogenous which are horizontally transferred genetic components that are usually infectious agents that cause disease i.e. HIV. In open reading frames are shown which can if translated predict which genes will be present and this can help to better understand human retroviruses. Of the four subtypes, HTLV-2 may be linked to Cutaneous T-cell lymphoma. In one study involving cultured lymphocytes from patients with mycosis fungoides, 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.Transmission
and breastfeeding and through blood transfusion, sexual contact, and use of intravenous drug usage.Epidemiology
and HTLV-2 are both involved in actively spreading epidemics, affecting 15-20 million people worldwide. 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 to 2009 among US blood donors has shown a general decline since the 1990s.Clinical significance
Infection with HTLV-2 generally causes no signs or symptoms and the virus has not been definitively linked with any specific health problems, but has been associated with several cases of myelopathy/tropical spastic paraparesis -like neurological disease. It is suspected that some affected people may later develop neurological problems such as:- Sensory neuropathies
- Gait abnormalities
- Bladder dysfunction
- Mild cognitive impairment
- Motor abnormalities
- Erectile dysfunction
- Mycosis fungoides
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. 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.