Human T-lymphotropic virus 2

Virology

HTLV-1 and HTLV-2 share broad similarities in genetic organization and expression, but differ in pathogenic properties. The virus uses GLUT-1 and NRP1 cellular receptors for entry, though HTLV-2 does not depend on heparan sulfate proteoglycans as HTLV-1 does.

Cell-to-cell transmission occurs through a virological synapse. The human T-lymphotropic virus family includes four subtypes. HTLV-2 may be linked to cutaneous T-cell lymphoma (CTCL); in one study, cultured lymphocytes from patients with mycosis fungoides showed HTLV-II gene sequences by PCR amplification, suggesting a possible correlation that requires further research.

Clinical significance

Infection with HTLV-2 generally causes no signs or symptoms and has not been definitively linked to specific health problems, though it has been associated with several cases of myelopathy/tropical spastic paraparesis (HAM/TSP)-like neurological disease. Suspected neurological issues include sensory neuropathies, gait abnormalities, bladder dysfunction, mild cognitive impairment, motor abnormalities, and erectile dysfunction.

Mycosis fungoides has also been associated. Limited evidence suggests links to chronic lung infections, asthma, dermatitis, and an impact on platelet count. In the 1980s, HTLV-2 was identified in a patient with a T cell lymphoproliferative disease resembling hairy cell leukemia.

Treatment

No cure or definitive treatment exists for HTLV-2, though chemotherapy and antiretrovirals can slow viral load. Diagnosis usually occurs through blood tests, but the infection is often unsuspected because most people remain asymptomatic; detection may happen during blood donation, testing for other infections, or work-up for associated problems. Prevention focuses on early detection and reducing spread: screening blood donors, promoting safe sex, discouraging needle sharing, and screening pregnant women so infected mothers can avoid breastfeeding. The long-term outlook is good; infection is lifelong, but 95% of affected people have no signs or symptoms, and HTLV-2-related problems tend to be milder than those from HTLV-1.

Did You Know?

• HTLV-2 is more common than HTLV-1 in the United States.
• Data from US blood donors collected from 2000 to 2009 showed a general decline in prevalence since the 1990s.
• Transmission occurs perinatally, through breastfeeding, blood transfusion, sexual contact, and intravenous drug use.