HTLV-1 is a microorganism that belongs to the retrovirus family, same as HIV. Although the virus is not common in our latitude, millions of people in endemic regions of the world, such as Japan, are infected with it. The HTLV-1 virus is dangerous because it causes adult T-cell leukemia and may be asymptomatic for up to 40 years.
Contents:
- HTLV-1 infection - history of virus discovery
- HTLV-1 infection - frequency of occurrence
- HTLV-1 infection - routes of infection
- HTLV-1 infection - consequences of infection
- HTLV-1 infection - screening for blood donors
- HTLV-1 infection - diagnosis
- HTLV-1 infection - prevention and treatment
Human T-cell leukemia / lymphoma virus or human T- lymphotropic virus) is a virus that belongs to the retrovirus family.
The HTLV-1 virus is a unique virus because it uses RNA as the carrier of genetic information (most organisms on Earth use DNA).
The virus, after infection of the cell, mainly T CD4 + lymphocytes, activates its own reverse transcriptase enzyme and transcribes its RNA into DNA. Thanks to the process of reverse transcription, the HTLV-1 virus can integrate into the human genome and remain in the cell in a latent (latent) form. A virus can have a latency period of up to 30-40 years.
HTLV-1 virus occurs in 6 subtypes (subtypes A to F), which differ in their genotype. However, studies have shown that the subtypes have no influence on the pathogenic potential of the virus. The most common infections are the cosmopolitan A subtype.
HTLV-1 infection - history of virus discovery
HTLV-1 was the first human retrovirus discovered, and its discovery completely changed the perception of this family of viruses as retroviruses were thought to only infect animals. This also had subsequent ramifications for the discovery of HIV, which is closely related to HTLV-1.
The HTLV-1 virus has been independently discovered on two different continents. In 1980 in the United States and in 1982 in Japan. Shortly after the discovery and description of the HTLV-1 virus was discovereda similar virus that shared 70% of its genome and was named HTLV-2.
Then, in 2005, two other HTLV-1 related microbes - HTLV-3 and HTLV-4 - were described in Central Africa.
HTLV-1 infection - frequency of occurrence
It is estimated that around 20 million people worldwide are infected with HTLV-1. HTLV-1 is endemic in regions including Japan, the Caribbean, South America (Brazil, Colombia, Chile, and Peru), West and Central Africa, Romania, parts of the Middle East (especially Iran), and central Australia.
Japan is the most important area for HTLV-1 infections. HTLV-1 infections in Poland are extremely rare. Moreover, there is no significant influx of people from endemic regions with virus infections.
HTLV-1 infection - routes of infection
The way in which the HTLV-1 virus infects cells in the human body is extremely interesting. After integration with the human genome, the HTLV-1 virus exists in the form of a provirus and can spread from cell to cell through the so-called viral synapse.
Therefore, the virus is virtually undetectable in the blood, although it is present in genital secretions. It is important to note that infection with HTLV-1 requires direct contact between the infected cell for infection to occur, as only then can a viral synapse form.
The most important routes of HTLV-1 infection are:
- breastfeeding the baby by the mother (probability of transmission is 20%)
- in labor (less than 5% of cases)
- sexual contact (more likely in people who do not use condoms, have multiple sexual partners, have genital ulcers)
- use of non-sterilized syringes
- blood transfusion (probability of transmission is 20-60%)
HTLV-1 infection - consequences of infection
HTLV-1 virus causes:
- Adult T-cell lymphoma / leukemia (ATL), which develops after 30-50 years of latency and is endemic in southwestern Japan, Korea, New Guinea, Central Africa and South America
- HTLV-1-associated myelopathy and spastic paraparesis, which develop after 20-40 years of latency
- bronchitis, bronchiectasis and bronchiectasis which are mainly caused by subtype C in the Melanesian island region
- infectious dermatitis
- inflammatory diseases like Sjögren's syndrome, vasculitis andmuscle
- immunodeficiencies causing opportunistic infections
- depression and chronic fatigue syndrome
It is now believed that HTLV-1 is possibly one of the most oncogenic agents known to mankind, making it so dangerous that around 90% of infected people remain asymptomatic carriers for many years.
The TAX protein, encoded by the viral genome, is mainly responsible for neoplastic transformation. It induces excessive division and at the same time inhibits the programmed death (apoptosis) of HTLV-1 infected cells.
HTLV-1 infection - screening for blood donors
The most risky route of HTLV-1 infection is transfusion of infected blood. Shortly after the discovery of HTLV-1, that is, since 1986, screening tests for the presence of the virus in the blood of donors began in many countries.
In 1993, screening of blood donors for the virus was already performed in all developed countries and in many developing countries where HTLV-1 is endemic.
Unfortunately, such research has not yet been implemented all over the world (e.g. in Poland).
In addition, only a few countries, such as the UK and France, screen for the presence of HTLV-1 in organ donors.
In Poland, tests on blood donors are not performed routinely, as there is no data indicating a significant incidence of HTLV-1 infections.
Pursuant to Directive 2006/17 / EC and 2012/39 / EU, laboratory tests for HTLV-1 are performed on donors of tissues / cells living in high-incidence areas, from such areas, or whose sexual partners or parents come from from such areas.
Positive laboratory tests for HTLV-1 exclude tissue and cell donation.
HTLV-1 infection - diagnosis
Screening for HTLV-1 virus is typically performed using highly sensitive immunoassays such as enzyme immunoassays (EIAs) or agglutination tests.
Positive or equivocal results are then confirmed by highly specific methods such as Western blot (WB), immunofluorescence tests (IFA) or radioimmunoprecipitation tests (RIPA).
Molecular tests to detect viral genetic material (proviral DNA) such as Polymerase Chain Reaction (PCR) are used to resolve equivocal results in the confirmation test.
The PCR test can also be used as a standalone confirmation test. In addition, molecular methods can be used foridentifying the HTLV-1 virus subtype.
HTLV-1 infection - prevention and treatment
Currently, there is no vaccine against HTLV-1, so the best method of preventing HTLV-1 infection is to avoid contact with secretions containing the virus. Educational programs in groups of people exposed to contact with the virus also play an important role in prevention.
In addition, despite nearly 40 years of research into the biology of HTLV-1, effective treatment strategies have still not been developed.
Adult T-cell lymphoma / leukemia is very resistant to conventional chemotherapy and radiation therapy used to treat other blood cancers.
Similarly, treatment of HTLV-1-associated myelopathy and spastic paraparesis with agents such as steroids and antiviral drugs is of little benefit.
Good to know … HTLV-1 and HIV viruses, apart from being very closely related to each other, also share common routes of transmission, as they infect the same cells (CD4 + T lymphocytes). It is estimated that up to 10% of people with HIV can be co-infected with HTLV-1.
About the author
Karolina Karabin, MD, PhD, molecular biologist, laboratory diagnostician, Cambridge Diagnostics Polska A biologist by profession, specializing in microbiology, and a laboratory diagnostician with over 10 years of experience in laboratory work. A graduate of the College of Molecular Medicine and a member of the Polish Society of Human Genetics. Head of research grants at the Laboratory of Molecular Diagnostics at the Department of Hematology, Oncology and Internal Diseases of the Medical University of Warsaw. She defended the title of doctor of medical sciences in the field of medical biology at the 1st Faculty of Medicine of the Medical University of Warsaw. Author of many scientific and popular science works in the field of laboratory diagnostics, molecular biology and nutrition. On a daily basis, as a specialist in the field of laboratory diagnostics, he runs the content department at Cambridge Diagnostics Polska and cooperates with a team of nutritionists at the CD Dietary Clinic. He shares his practical knowledge on diagnostics and diet therapy of diseases with specialists at conferences, training sessions, and in magazines and websites. She is particularly interested in the influence of modern lifestyle on molecular processes in the body.
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