Learn all about HTLV (Human T Lymphotropic Virus). Human T-cell Lymphotropic virus (HTLV) was the first human retrovirus discovered. HTLV belongs to the Retroviridae family in the genus Deltaretrovirus. Retroviruses are RNA viruses that use an enzyme called reverse transcriptase to produce DNA from RNA. The DNA is subsequently incorporated into the host’s genome. HTLV predominantly affects T lymphocytes.
Human T-cell lymphotropic virus type 1 (HTLV-1) is endemic in many parts of the world and is primarily transmitted through sexual intercourse or from mother to child. Sexual transmission occurs more efficiently from men to women than women to men and might be enhanced by sexually transmitted diseases that cause ulcers and result in mucosal ruptures, such as syphilis, herpes simplex type 2 (HSV-2), and chancroid.
Human T-cell leukemia virus type 1 (HTLV-1), the first human retrovirus to be discovered, is present in diverse regions of the world, where its infection is usually neglected in health care settings and by public health authorities. Since it is usually asymptomatic in the beginning of the infection and disease typically manifests later in life, silent transmission occurs, which is associated with sexual relations, breastfeeding, and blood transfusions.
Treatment of opportunistic infections varies depending on the type of disease and ranges from careful observation to aggressive chemotherapy and antiretroviral agents. Adult T cell lymphoma is a common complication of HTLV infection and requires aggressive chemotherapy, typically R-CHOP.
Other treatments for ATL in HTLV infected patients include interferon alpha, zidovudine with interferon alpha and CHOP with arsenic trioxide. Therapies studied include corticosteroids, plasmapheresis, cyclophosphamide, and interferon, which may produce a temporary symptomatic improvement in myelopathy symptoms.
HTLV (Human T-Lymphotropic Virus)
HTLV stands for Human T cell Lymphotropic Virus. HTLV belongs to the Retroviridae family in the genus Deltaretrovirus. Retroviruses are RNA viruses that use an enzyme called reverse transcriptase to produce DNA from RNA. It is a retrovirus that infects a type of white blood cell called a T-cell or T-lymphocyte. The great majority of people infected with HTLV-1 do not develop any related disease. A small minority of individuals, about 1 in 20 of these infected, will develop disease due to HTLV-1, but this usually occurs after several decades of infection.
Human T-cell Leukemia/Lymphoma Virus Types
Infection with human T cell leukemia/lymphoma virus type I (HTLV-I) has been etiologically associated with two diseases: adult T cell leukemia and HTLV-I-associated myelopathy/tropical spastic paraparesis. Increasing evidence suggests that HTLV-I infection may be associated with immunosuppression and, as a consequence, affect the risk and expression of several other infectious diseases, of which the best studied are strongyloidiasis, tuberculosis, and leprosy. HTLV-II is prevalent among injection drug users in the United States and in Europe, and >80% of HTLV infections in drug users in the United States are due to HTLV-II.
HTLV-II also appears to be endemic in Native American populations, including the Guaymi Indians in Panama and Native Americans in Florida and New Mexico. HTLV-II-infected blood donors most often report either a history of injection drug use or a history of sexual contact with an injection drug user. A smaller percentage of infected individuals report a history of blood transfusion. HTLV-II is transmitted similarly to HTLV-I, but much less is known about the specific modes and efficiency of transmission of HTLV-II.
The virus can be transmitted by transfusion of cellular blood products (whole blood, red blood cells, and platelets). Neither HTLV-3 nor HTLV-4 has been associated with specific diseases thus far, and further research is ongoing. Given the ongoing discovery of subtypes and strains, it is not surprising that 28% of certain populations in central Africa have been reported to have indeterminate HTLV serology results.
How HTLV-1 Infection Causes Cancer?
The new DNA genes can then become part of the chromosomes of the human cell infected by the virus. This can change how the cell grows and divides, which can sometimes lead to cancer. HTLV-1 is something like HIV, which is another human retrovirus. But HTLV-1 cannot cause AIDS.
HTLV-1 Virus Infections Symptoms
HAM/TSP usually has an insidious onset and chronic evolution. Initial symptoms are subtle and include gait problems, unexplained falls, low back pain, constipation, urinary urgency/incontinence and numbness or pain in the lower limbs. Over the years, progressive leg weakness ensues followed by the exacerbation of the urinary and sensory symptoms. The prognosis of the neurological disability is variable. Approximately 2-5% of people with HTLV-1 will develop ATL, a cancer of the T-cells (a type of white blood cell). The signs and symptoms of this condition and the disease progression vary from person to person. Affected people may have the following features:
- Lymphadenopathy (swollen lymph nodes)
- Nausea and vomiting
- Skin and bone abnormalities
- Enlarged liver and/or spleen
- Frequent infections
Roughly .25-2% of people with HTLV-1 will develop HAM/TSP, a chronic, progressive disease of the nervous system. Signs and symptoms of this condition vary but may include
- Progressive weakness
- Stiff muscles
- Muscle spasms
- Weak’ bladder
HTLV-1 Infection Treatment
HTLV-1 infection treatment includes;
- Immunosuppressive Therapy
- There are many forms of these steroids, prednisolone, prednisone and methylprednisolone. They have never been formally tested in patients with HAM/TSP but some observational information on its use is available.
- Steroid sparing drugs
- Ciclosporin: A, methotrexate and azathioprine are often used in autoimmune diseases and some doctors prescribe them for HAM/TSP patients. They do not reduce the HTLV-1 proviral load. They might prevent the progression of HAM/TSP. But there is no data available on large groups of patients to be sure.
- Anti-viral therapy
- Interferon alpha (IFN- α)
- Anti-retroviral therapy
- Zidovudine and lamivudine have been tested against placebo in the UK in 2004. These two drugs did not reduce the HTLV-1 proviral load and did not improve mobility. Raltegravir has also been tested, but did not reduce the HTLV-1 proviral load and did not improve mobility.
Sodium-valproate has been shown to initially increase and then reduce HTLV-1 proviral load in patients with HAM/TSP.