- Last Update On : 2013-01-20
HTLV 1 is a retrovirus that has been associated with adult T cell leukemia/lymphoma (ATLL) and tropical spastic paraperesis (TSP). HTLV 1 infection is endemic in some Asian and African countries as well as in Central America. In the U.S., the virus is found primarily in people of African-American background. Approximately 10 to 20 million people are infected worldwide. HTLV 1 can be transmitted by blood and breast-feeding.
ATLL occurs in 2 to 5% of infected individuals, mainly those individuals infected at birth. The estimated average time between HTLV 1 infection and malignancy is 20 to 30 years. ATLL is a rapidly aggressive disease with a mean survival of 6 months that presents with symptoms of hypercalcemia, skin infiltration, hepatosplenomegaly, and lytic bone lesions. Leukemic cells have characteristic flower-like lobulated nuclei.
TSP occurs with about the same frequency as ATLL. It is a slow progressive incapacitating myelopathy characterized by spasticity and weakness of lower limbs, paraplegia, sphincter disturbances, and various degrees of sensory loss.
This virus can be transmitted by blood transfusions and blood donors are routinely screened for HTLV 1 antibody. Approximately 30% of the recipients, who received HTLV 1 positive units prior to the introduction of testing, have seroconverted. Very few (1%) of these patients have progressed to leukemia or paresis, due to the long latency period.
Another related virus, HTLV-2 was originally isolated from two patients with hairy cell leukemia. This virus may also cause neurologic disease similar to TSP. It is transmitted by blood and sexual intercourse. Most males in the U.S. with HTLV-2 infection have a history of drug abuse, while most infected females have a history of sexual contact with known IV drug users.
Specimens are initially tested for viral antibody with an enzyme immunoassay (EIA). Because the viruses are closely related, current HTLV-1 EIAs detect the majority of HTLV 2 infections. Positive EIA samples are further tested by an HTLV-1 Western blot. HTLV confirmatory criteria require the presence of antibody to p24 and gp46 or gp61 for classification as HTLV positive. Samples that are positive can be tested with HTLV peptide assays to distinguish between HTLV 1 and 2.
Results are reported as positive or negative. The reference value is negative.
Specimen requirement is one SST tube of blood.