Human T-Cell Lymphotropic Virus (HTLV I/II)
Human T-Cell Lymphotropic Virus
Sample
- The serum of the patient is needed.
- A random sample may be used.
Purpose of the test (Indication)
- This is used to diagnose a certain type of leukemia (T-cell leukemia).
- To diagnose demyelinating neurological disease.
Definition of Human T-Cell Lymphotropic Virus (HTLV)
- HTLV-I
- This virus is closely related to retroviruses and is mostly like HIV-I.
- Its transmission is also like HIV-I.
- HTLV-I lymphotropic, the retrovirus is the causative agent of cutaneous T-cell lymphoma in adults and nervous system degenerative disorder called tropical spastic paraparesis.
- HTLV-II
- It is not conclusively associated with specific diseases.
Pathophysiology of Human T-Cell Lymphotropic Virus (HTLV)
- These are oncogenic RNA retroviruses :
- HTLV-I is associated with T-cell leukemia/ lymphoma.
- It is endemic in certain parts of the Japan and Caribbean basin.
- There are large lymphocytes, multilobulated nuclei like monocytes.
- It is rarely associated with neurologic conditions like tropical spastic paraparesis.
- HTLV-II is associated with:
- There are no clearcut associations but seen in a few following condtions.
- Demyelinating neurological disorder (tropical spastic paraparesis).
- Hairy cell leukemia.
- HTLV-I is associated with T-cell leukemia/ lymphoma.
- This is human retrovirus belongs to the Retroviridae family in the genus Deltaretrovirus.
- Retroviruses are RNA viruses with the presence of reverse transpeptidase enzyme which converts RNA virus to DNA virus which incorporates into the genome of the host and mostly affects T-lymphocytes.
HTLV-I and difference from the HIV-I:
- HTLV-I does not cause depletion of the T-helper cells (CD4+ cells).
- It is generally not associated with immunosuppression.
- It does not cause AID syndrome.
- The presence of the antibodies does not indicate HIV-I infection or risk of AIDS.
- This is endemic in southern Japan, a Caribbean island, South America, and areas of Africa.
Distribution of the HTLV-I/II
- HTLV-I is found predominantly in:
- Southern Japan.
- Some of the Caribbean islands.
- Parts of Central and South America.
- Sub-Saharan Africa.
- >10% of the people in the endemic area are seropositive. This virus is found in 50% of the relatives of virus-positive leukemic patients.
Mode of spread. This is like HIV:
- Body fluids contaminations.
- Intravenous drug use.
- HTLV-I is seen in I/V drug users in the USA (20% to 25%).
- HTLV-I has also been seen in prostitutes (7%).
- Sexual transmission.
- Breastfeeding. There is a risk of 20% spread to infants depending upon the duration of breastfeeding.
- In the USA HTLV-I has been found in:
- Patient with ATL (adult T- cell leukemia).
- Intravenous drug users.
- Donated blood products.
- There are 40% to 60% chances of seroconversion in the contaminated blood.
- While more risk to the immunocompromised patient.
- Even in healthy persons.
- In the case of transplantation of the liver, kidneys, and lungs.
HTLV-I role for T-L leukemia/lymphoma:
- HTLV-I genome structure consists of gag, pol, env, and long terminal repeat (LTR), like other retroviruses.
- There is another region labeled as the tax (TAX) gene.
- This tax gene can cause viral replication and also acts of LTR.
- There is a transcription of the viral mRNA.
- tax protein also activates several host genes in the lymphocytes.
- There is activation and the proliferation of the T-lymphocytes (CD4+).
- THis HTLV-I virus causes the expansion and the nonmalignant proliferation of the T-L (CD4+).
- There increased risk for mutation and gene instability.
- Ultimately there is the emergence of the monoclonal T-L emergence and leads to T-L leukemia/lymphoma.
Normal
- Antibodies are negative.
Lab Diagnosis of Human T-Cell Lymphotropic Virus:
- Serologic tests show HTLV-I antibodies by ELIZA.
- HTLV-I antibodies are seen in:
- Adult T-cell leukemia/lymphoma.
- Degenerative neurological diseases are called Tropical spastic paraparesis in Caribean islands.
- It is seen in 5% of the general population and 15% of the older people.
- HTLV-I myelopathy is seen in Japan.
- <15% of the general population of Japan and <30% of the older people.
- It is seen is prostitutes in the USA
- These are seen in I/V drug abusers.
- It is seen in multiple blood transfusions.
- Rarely seen in homosexuals males.
- These antibodies are not seen in hemophiliacs.
- It is seen in 0.025% of random blood donors.
- These tests also detect HTLV-II.
- Western blot test is done to confirm the serologic tests.
- The nucleic acid probe with PCR enhancement is the most sensitive test to differentiate HTLV-I and HTLV-II.
Positive HTLV antibodies are seen in:
- Acute HTLV infection.
- HTLV-I
- Adult T-cell leukemia.
- Tropical spastic paraparesis.
- Hairy cell leukemia.