Virus T: Mechanisms of Transmission, Symptoms, Diagnosis, Treatment, Prediction and Prevention

It is mainly transmitted from mother to child through breastfeeding or through blood transfusion.

The human T-cell lymphotropic virus type 1 or T virus was first discovered as a human retrovirus that causes the malignant hematologic T-cell neoplasm, called leukemia or T-cell lymphoma in adults.

The virus is transmitted through contact with body fluids containing cells infected with the human T-cell lymphotropic virus type 1.

Strategies for the prevention of adult T cell leukemia should be divided into two steps.

The first step is the prevention of the transmission of the human lymphotropic virus of type 1 T cells.

This has been established in some endemic areas of the T Virus by screening the T Virus among blood donors and abstaining from breastfeeding in pregnant women who are carriers of human T-cell type 1 lymphotropic virus.

The second step is the prevention of the development of T-cell leukemia in adults among carriers of the human T-cell type 1 lymphotropic virus.

This has not been established at all. Approximately 90% of T virus carriers remain as healthy as uninfected individuals throughout their lifetime and the risk factors for developing T cell leukemia in adults have not yet been defined.

In addition, preventive intervention, such as vaccination, can cause other unfavorable immunological consequences, which is why well-considered strategies should be further developed.

Transmission mechanisms

It has been shown that the route of infection is related to the development of diseases associated with the human lymphotropic virus of type 1 T cells.

T cell leukemia in adults has been associated mainly with breastfeeding and T-associated myelopathy and tropical spastic paraparesis that has been associated with blood transfusion.

Three main routes of viral transmission have been established:

  • Transmission from mother to child, mainly through breastfeeding.
  • Sexual transmission, predominantly male to female.
  • Cellular blood components.

The efficacy of the mother-to-child transmission route is estimated at around 20%.

Mother-to-child transmission during pregnancy or the peripartum period has been reported to be less than 5%.

Virus T can infect a wide variety of human cell types in vitro.

It has been proposed that Virus T particles first come into contact with heparan sulfate proteoglycan, then neuropilin-1 recruits the Virus T complex and heparan sulfate proteoglycan to present them to the glucose transporter 1.

The glucose transporter complex 1, heparan sulfate proteoglycan and neuropilin-1, makes the viral envelope competent for membrane fusion and entry into the cell.

Virus-free T virus virions are poorly infectious in vitro for most cell types, including their major target cells, CD4 T cells.

The main transmission pattern of Virus T is cell-to-cell contact, however, only myeloid and plasmacytoid dendritic cells can be infected with the virus.

This route may be important in the context of mother-to-child transmission through breastfeeding.

Dendritic cells can play an important role during the initial acquisition of the infection, the transmission of milk virus to the mucosa.

Three main mechanisms of cell-to-cell transmission of T virus have been proposed: Infected lymphocytes polarized their microtubules and viral components upon contact with other T cells, forming the so-called virological synapses.

The infected cells transiently produce and store viral particles in extracellular adhesive structures rich in extracellular matrix components, including collagen and agrin, and cellular linker proteins, which resemble bacterial biofilms.

Extracellular viral assemblies attach rapidly to other cells at cell contact, allowing virus spread and infection of target cells

Prevention of Virus T transmission

The prognosis for adult T cell leukemia is one of the worst among the hematological malignancies with the best available therapy, and no preventive vaccine against the T virus is yet available.

Therefore, preventing the transmission of the virus is the most realistic way to prevent the progression of the disease.

Prevention of vertical transmission

The prevention of mother-to-child transmission has the most significant impact on the appearance of T virus infection and associated diseases.

Avoiding breastfeeding is essential since it is the main form of vertical transmission of this virus.

Prenatal detection for the T virus should be used in endemic areas, combined with the relevant advice from carrier mothers regarding the transmission of the virus through breastfeeding.

Even with exclusive bottle-feeding, 2.5% of babies born to carrier mothers were infected with the virus, although intrauterine transmission of T-Virus is rare, transplacental transmission during delivery is more likely as in the case of other viruses.

Prevention of horizontal transmission

Virus T can also be transmitted through contact with body fluids, such as whole blood or whole blood products.

The development of T cell leukemia in adults, related to transfusion is exceptional.

Therefore, the purpose of prevention of horizontal transmission is mainly to reduce the population of carriers of the virus.

Transfusion and sexual transmission

The screening program to prevent the transmission of transfusion-related virus T has been developed since 1986 and many countries in endemic areas began to employ the systematic screening of all blood donors.

The screening of candidates for blood donors has proven to be an effective strategy to prevent the transmission of the virus.

For the non-endemic areas of the reports, they showed that the risk of infection by Virus T could be improved in some populations of selected donors, especially in immigrants from endemic areas, recommending the use of policies for the selective recruitment of donors.

For developing countries, the high cost of imported detection test kit is not insignificant, therefore, it is necessary to develop more profitable strategies for the analysis of blood donors.

In most African countries, transfusion still represents a risk of transmission of Virus T.

Most of the sexual transmission of the virus is from men to women.

Recommendations should be emphasized to prevent sexually transmitted infections, including the use of condoms and to avoid multiple and unknown sexual partners.

However, access to correct information about the infection and proper counseling is very important since candidates for blood donors and sexually active people are usually asymptomatic and of reproductive age.

symptom

T-cell leukemia in adults, myelopathy associated with the T-virus and tropical spastic paraparesis, are diseases associated with the human lymphotropic virus of T-cell type 1.

Signs and symptoms of leukemia or T-cell lymphocytic lymphoma in adults may include:

  • Fever.
  • Night sweats.
  • Fatigue.
  • Increased number and abnormal immature lymphocytes.
  • Enlarged lymph nodes

Symptoms of T-virus-associated myelopathy and tropical spastic paraparesis may include:

  • Weakness in the lower extremities.
  • Muscle spasms and contractions.
  • Back pain.
  • Muscular stiffness.
  • Urinary, intestinal and sexual dysfunction.

Diagnosis

Human lymphotropic T virus infection is associated with certain rare diseases of T lymphocytes (T cells), a type of white blood cell that is an important part of the body’s immune system.

There is evidence to detect an infection by the virus in order to help identify the virus as the underlying cause of certain diseases.

When the virus enters the body it preferentially infects T-cell lymphocytes. The body’s immune system responds by producing antibodies that target the virus.

Most people who are infected do not develop active disease, but a few will develop a condition related to a T cell disorder.

HTLV tests can be used in different ways:

  • In people with risk factors for infection with the human T-cell lymphotropic virus type 1 (such as living in parts of the world where the infection is most common, having a sexual partner who comes from one of these areas, having multiple sexual partners, be a Native American Indian, or have a history of blood transfusions.
  • To diagnose the cause of a T cell-related disorder if a person has symptoms consistent with myelopathy associated with the human T-cell lymphotropic virus type 1 tropical spastic paraparesis, especially if the person has risk factors associated with this condition.
  • To determine the source of infection of an affected individual; Because the human T-cell lymphotropic virus type 1 can be passed from the mother to the baby during pregnancy, the mother of an affected child can be tested to determine if it is the probable source of the child’s infection.
  • Typically, an enzyme immunoassay test method is used to detect antibodies to the human T-cell lymphotropic virus type 1 in the blood initially. If the initial test is positive, a second method, such as the electrotransfer test, is ordered to confirm the finding.
  • In cases where HTLV-I and HTLV-II can not be distinguished, molecular tests (polymerase chain reaction method) that detect the genetic material of the virus can be performed.

The human T-cell lymphotropic virus type 1 tests are usually performed step by step and usually include an initial test followed by confirmatory tests, depending on the results.

If the initial test of the human T-cell lymphotropic virus type 1 is negative, then it is unlikely that the individual has an infection and the person’s symptoms are probably due to another cause. In general, no further tests are necessary.

If the patient has HTLV-I or HTLV-II antibodies in the initial and confirmatory tests, then it is likely that the person has an infection with type 1 human T-cell lymphotropic virus.

If you also have symptoms related to an associated condition, then it is likely that this infection is the underlying cause.

A patient with positive initial and confirmatory results but no symptoms, such as someone who has been evaluated because she is the mother of an affected child or the sexual partner of an affected person, or someone whose blood donation was positive and confirmatory tests are also positive, You probably have the infection.

However, in the vast majority of cases, the person will never develop a disease.

These people can transmit the infection to other people and should take the necessary precautions.

Those who have a positive initial test of human T-cell lymphotropic virus type 1 and a negative confirmatory test probably have a false-positive infection and not a type 1 human T-cell lymphotropic virus.

Those with an indeterminate confirmation test result should be reanalyzed in several weeks to determine if they have developed antibodies.

If the confirmatory test is negative or still undetermined, then it is unlikely that the person has the infection.

A positive molecular test of human type T lymphotropic virus type 1 indicates that the person analyzed has the infection.

If the molecular result is negative, then the person is less likely to become infected, but it can not be ruled out since the amount of virus in the blood may have been too low to detect at the time of testing.

The human T-cell lymphotropic virus type 1 becomes inactive (latent) in the body after an infection, but they are never completely eradicated.

For this reason, a person who tested positive will not be able to donate blood.

Treatment

The current treatment options are:

  • Conventional chemotherapy.
  • Allogeneic transplant of hematopoietic stem cells.
  • Interferon-α and zidovudine.
  • Vaccine.

Forecast

The prognosis is still poor with chemotherapy or transplantation of allogeneic hematopoietic stem cells.

Until now, prevention is based entirely on the prevention of vertical transmission of Virus T by refraining from breastfeeding the mother carrying the virus.

The prenatal detection of Virus T should be implemented in the endemic area with careful advice.

In addition, the screening of candidates for blood donors has proven to be effective in preventing transmission.

Recommendations to prevent sexual transmission, including the use of condoms and the adoption of safe sexual behavior, should be emphasized.

The need to develop an effective and safe vaccine should be emphasized.