HTLV (Human T-lymphotropic virus)
Date: 2 سال قبل
author: AmirAbad
HTLV (Human T-lymphotropic virus)
The human T-lymphotropic
virus or human T-cell leukemia-lymphoma virus (HTLV) family of viruses are a
group of human retroviruses that are known to cause a type of cancer called
adult T-cell leukemia/lymphoma and a demyelinating disease called HTLV-1
associated myelopathy/tropical spastic paraparesis (HAM/TSP). The HTLV genome
is diploid, composed of two copies of a single-stranded RNA virus whose genome
is copied into a double-stranded DNA form that integrates into the host cell
genome, at which point the virus is referred to as a provirus.
How is HTLV infection transmitted?
HTLV infection can be
transmitted via 3 main routes:
· Via
unprotected sexual contact.
·
Via contaminated
blood transfusions or blood products1, sharing contaminated needles and other
injection equipment, self-flagellation, or receiving an organ or tissue
transplant from an infected donor.
·
HTLV virus can be
passed from an infected mother to her baby mainly via breast feeding
(predominantly with prolonged breast feeding beyond 6 months of age) and less
commonly during the pregnancy (intra-uterine transmission).
What diseases does HTLV
cause?
In the majority of infected
individuals there is an asymptomatic carrier state (silent but ongoing
infection), with only a small proportion (about 5 to 9%) developing disease
associated with HTLV-1 during their lifetime.
HTLV-1 infection gives rise
to two main disease entities:
·
Adult T-cell
leukaemia/lymphoma (ATLL) which is a form of blood cancer
·
HTLV-associated
myelopathy (HAM)
ATLL occurs in
approximately 5% and HAM in approximately 3% of carriers.
In a smaller number of
patients, other inflammatory conditions such as uveitis (inflammation of the
eye), arthritis (inflammation of joints), myositis (inflammation of muscles),
alveolitis (inflammation of lungs) and dermatitis (inflammation of skin) can be
seen.
The HTLV-2 disease spectrum
is less clear, but lung conditions, myelopathy (inflammation of the spinal
cord) and dermatitis, have been reported.
Sometimes, as HTLV causes
mild immunosuppression, patients may develop diseases caused by other infectious
agents that are able to thrive in a host with a suppressed immune system (e.g.
parasitic infections such as Strongyloides stercoralis).
What tests are performed?
- Serology:
Once individuals are infected with HTLV, their immune system starts
producing antibodies that are specifically directed against the virus. By
detection of these antibodies using laboratory tests, whether or not a
person is infected with this virus can be determined. Using the
development of antibodies to detect infection is called serology.
- Molecular:
Sometimes a test to detect the genetic material of the virus is used. This
can be useful in situations such as having indeterminate serology
(inconclusive antibody) test results or when antibodies to both HTLV-1 and
HTLV-2 are detected. The measurement of HTLV-1 viral load in patients
found to be infected is also useful to determine risk of disease and
sometimes to aid with the diagnosis and treatment of an HTLV-1-associated
disease. Detection and quantification of HTLV-genetic material is called
molecular diagnostics.
Prevention and treatment
There is currently no
vaccine for HTLV-1, although development of a vaccine is considered feasible.
However, animal models may not be suitable to study vaccine effects in HTLV-1.
No candidate HTLV-1 vaccine has proceeded to a clinical trial with an efficacy
endpoint so far.
No treatment is currently
recommended for people with asymptomatic HTLV-1 infection. Treatment should
instead focus on the symptoms of associated diseases, namely ATL and HAM/TSP,
and screening for comorbidities and coinfection.
Write Comment
Comments