Human T-cell leukemia virus (HTLV)

Two types of human T-cell Leukemia Virus (HTLV) are known. They are also known as human T-cell lymphotrophic viruses . HTLV-1 often is carried by a person with no overt symptoms being apparent. However, HTLV-I is capable of causing a number of maladies. These include abnormalities of the T cells and B cells , a chronic infection of the myelin covering of nerves that causes a degeneration of the nervous system, sores on the skin, and an inflammation of the inside of the eye. HTLV-II infection usually does not produce any symptoms. However, in some people a cancer of the blood known as hairy cell leukemia can develop.

At one time there was a third HTLV virus. However, what once called HTLV-III is now referred to as the Human Immunodeficiency Virus (HIV ). HIV is generally accepted to be the causative agent of acquired immunodeficiency syndrome.

HTLV is a type of virus called a retrovirus. These viruses are unique in that they possess an enzyme that enables them to manufacture deoxyribonucleic acid from their constituent ribonucleic acid .

HTLV-I is most commonly associated with a disease called adult T-cell leukemia, which is a rapidly spreading cancerous growth that affects the T cells of the immune system . Indeed, the virus was first isolated in 1980 from a patient with T-cell lymphoma. Once the symptoms of the disease appear, deterioration of the individual occurs quickly. However, the symptoms may not appear for decades after the virus has infected someone. The reason for this extended period of latency is not known. HTLV-I has also been isolated from people who have maladies that include arthritis, Kaposi's sarcoma, and non-Hodgkin's lymphoma. Whether the virus is a contributor to such maladies, or is coincidentally expressed, is not yet clear.

The HTLV-I form of the virus is found all over the world. However, it is more prevalent in some countries, such as Japan, than in other countries, such as the United States.

HTLV-II was isolated in 1982 from a patient with hairy cell leukemia. Even so, the virus still has not been definitively established as the cause of that malady. However, the frequent isolation of HTLV-II from patients with this form of leukemia, as well as other types of leukemia's and lymphomas, lends credence to the theory that the virus is vital for the development of the malignancies.

HTLV-II is found in many intravenous drug users. Transmission of the virus from person to person via the contaminated blood in the needles used for drug injection has been documented. HTLV-II can also be spread by exchange of other body fluids, such as occurs in sexual contact.

In spite of the above conditions associated with HTLVII, the majority of those infected with the virus do not display any symptoms.

The virus can be passed from person to person by the transfer of contaminated blood or via the intimate association of sexual contact. Also, the virus is capable of being passed from mother to infant via breast milk. Blood donor programs in many countries now rigorously test for the presence of HTLV in donated blood and plasma.

HTLV infections are incurable. However, the progressive physical deterioration associated with the infections can be lessened somewhat if the infections are diagnosed early. Screening for the virus relies on the detection of antibodies. Typically, antigen-antibody agglutination tests or the enzyme-linked immunosorbent assay (ELISA ) is used. Confirmation of infections is provided by demonstrating the presence of viral protein in electrophoretic gels following the application of an antibody (the technique is dubbed the Western Blot).

See also AIDS; Immunodeficiency