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Mononucleosis

Mononucleosis


It is a common viral infection that affects humans relatively early, during the first decade of life. It is more easily transmitted in situations of overcrowding and poor adherence to hygiene conditions. Even in developed societies, at least 50% of the population becomes HIV positive before puberty.



Where is it due to?


It is caused by the Epstein-Barr virus (EBV) or human herpesvirus 4, which belongs to the Gamaherpesvirinae subfamily of the Herpesviridae family. EBV has the morphology of herpesviruses, with 162 capsomeres, an icosahedral arrangement, surrounded by a lipid envelope, and carrying a 172-kbp DNA double helix in a circular or straight arrangement, depending on the stage of infection.


Mechanism of virus infection


EBV initially infects B lymphocytes through a receptor, the complement receptor CD21. It has the ability to transform precursor and mature B lymphocytes into lymphoblastoid cell lines. B lymphocytes are places where the virus "hides", but epithelial cells, which do not express the receptor, are where it reproduces. Monocytes can also be infected by the virus and the infection can affect the virus-host interaction. B lymphocytes can express the viral nuclear antigens, EBNA 1, EBNA 2, EBNA 3(EBNA 3a), EBNA 4(EBNA 3b), EBNA 5 (LP) and EBNA 6(EBNA 3c), and membrane proteins of virus (LMP 1, 2A and B). In addition, latently infected B lymphocytes contain large amounts of virus-encoded pieces of RNA, known as EBER's (EBER 1, EBER 2).


How is it transmitted?


The transmission of the virus takes place with saliva and rarely with the sexual route. Familial transmission is very common. Therefore, the virus is often isolated from the oropharyngeal secretions of HIV-positive individuals, as well as those with infectious mononucleosis (LM). This is also the reason why LM was called the "kissing disease".

What does it cause?


In its usual uncomplicated course, the disease causes infectious mononucleosis, which includes fever, malaise, pharyngotonsillitis, periorbital edema, hepatosplenomegaly, lymphocytosis with atypical lymphocytes, and elevated liver enzymes. Complications of the disease occur less often, are divided into three categories and can be:

  • Benign – haematological, neurological, visceral, skin/epithelial other

  • Malignant and precancerous – lymphomas (Burkitt, Hodgkin, non Hodgkin) lymphoproliferative diseases, possible relationship with stomach and breast cancer

  • Genetics – X-linked lymphoproliferative syndrome






Diagnostic methods


To diagnose the presence of the EBV virus can be used:

Direct methods, such as:

  • the use of an electron microscope,

  • the detection of virus antigens (EBNA 1, EBNA 2, LMP 1),

  • molecular techniques (PCR, in situ hybridization for EBER 1 and EBER 2).

Prevention - treatment


There is no approved vaccination program to prevent infection with the virus. However, two vaccine attempts have been made, one using glycoprotein 340 (gp340) to produce virus-neutralizing antibodies and the other using peptide vaccines, based on major histocompatibility complex class I gene epitopes.

Standard treatment includes symptomatic treatment, such as antipyretic drugs, rest, hydration, and periodic medical and laboratory monitoring. For treatment, nucleoside analogues such as acyclovir, ganciclovir and flamciclovir, as well as the pyrophosphate analogue foscarnet inhibit the multiplication of the virus. Despite inhibition of virus multiplication with these drugs, symptoms persist, possibly due to immune stimulation.

In special cases and to treat the complications of the disease, cortisone, γ-interferon, cyclosporine, methotrexate etoposide, etc. are applied on a case-by-case basis.




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