Viral entry and pathway selection
The pathogen is the Epstein-Barr virus (strains 1A or 2B). The virion adsorbs onto the surface of target cells by binding to the CD21 receptor. The membrane glycoprotein gp350/220 plays a key role in this process, while proteins gp85, gp25, and gp42/38 ensure the fusion of the viral envelope with the cell membrane.
Further pathogenesis strictly depends on the type of infected cell:
- In epithelial cells (oropharyngeal mucosa, salivary gland ducts), viral replication ends in cytolysis—cell destruction. New virions enter the saliva en masse, where they can be detected for 12 to 18 months after infection.
- In B-lymphocytes, replication proceeds without cytolysis. The virus blocks cellular apoptosis, leading to the phenomenon of immortalization. The B-cell transforms into a lymphoblastoid cell and acquires the capacity for unlimited division (each division is accompanied by the transmission of the virus to daughter cells).
Role of antigens in pathogenesis
Control over the target cell is exerted through the sequential synthesis of viral antigens and proteins:
- Nuclear antigens (EBNA). The EBNA1 protein maintains viral DNA in the nucleus as an episome (a resting circular structure). EBNA2 and EBNA3 stimulate cell growth and the production of latent proteins.
- Latent membrane proteins (LMP). LMP1 acts as an oncogene, while LMP2 blocks viral activation during the latency phase, maintaining chronic infection.
The immune system reacts to antigens in a strict sequence. First, antibodies to the capsid antigen (VCA) appear in the blood, followed by antibodies to the early (EA) and membrane (MA) antigens, and last to the nuclear (EBNA) antigen.
Mechanisms of profound immunosuppression
Epstein-Barr virus actively suppresses host defenses by triggering a cascade of immunological disorders:
- T-helper blindness. Viral proteins (e.g., gp42/38) directly bind to MHC-II molecules on macrophages and B-lymphocytes, shielding them. This blocks antigen-presenting function and disrupts cellular cooperation.
- Action of viral cytokines. EBV synthesizes a protein analogous to interleukin-10. It suppresses the production of $\gamma$-interferon and IL-12, paralyzing the function of macrophages, natural killers, and cytotoxic lymphocytes.
- Depletion of the humoral arm. Viral superantigens cause chaotic (polyclonal) activation of B-lymphocytes. Cells synthesize nonspecific antibodies and then massively undergo apoptosis. This impairs the formation of immunological memory.
- Mutational escape. Direct and inverted nucleotide repeats in the EBV genome easily shift positions during replication, allowing the virus to temporarily evade antibody attacks.
Clinical and morphological consequences
Pathogenetic processes are directly reflected in the clinical picture of mononucleosis. Proliferation and hyperplasia of lymphoid tissue lead to generalized lymphadenopathy, hepatosplenomegaly, and tonsillopharyngitis.
The hemogram shows leukocytosis accompanied by the appearance of atypical mononuclear cells—large cells with broad basophilic cytoplasm. Polyclonal activation of B-lymphocytes leads to the synthesis of heterophile antibodies, which are used in diagnostics (heteroagglutination reactions). As a result, the virus persists in the body for life, creating risks for future immuno- and oncopathology.
Briefly: answers to topical questions
Specifically, which classes of immunoglobulins (IgM, IgG) to the capsid antigen (VCA) are used to diagnose the acute phase, and how long do they circulate?
To diagnose the acute phase of Epstein-Barr virus infection, IgM antibodies to the viral capsid antigen (anti-VCA IgM) are used. As the clinical picture unfolds, the level of IgG antibodies to the capsid antigen (anti-VCA IgG) increases, which subsequently serve as markers of a past infection. The serological profile during the height of the disease includes the detection of anti-VCA IgM in the absence of antibodies to the nuclear antigen. The exact duration of VCA immunoglobulin circulation is not specified in the provided materials.
Which specific oncological diseases are associated with lifelong persistence of the Epstein-Barr virus?
The following processes are linked in the sources to the lifelong persistence of Epstein-Barr virus and its role in oncopathology:
- Lymphoproliferative diseases: X-linked lymphoproliferative syndrome, B-lymphoproliferative disorders including post-transplant and HIV lymphomas, multiple polyclonal lymphomas, Burkitt lymphoma, Hodgkin's disease, T-cell lymphoma.
- Epithelial tumors and lesions: hairy leukoplakia of the tongue, leukoplakia of the tongue and oral mucosa, nasopharyngeal carcinoma, gastric carcinoma, stomach and intestinal cancer.
- Tumors with a possible, unexcluded EBV involvement: leiomyosarcoma, hepatocellular carcinoma, thymoma.
To remember the order in which antibodies appear in EBV infection, use the mnemonic "TIME" (in Russian «ВРЕМЯ»): First Capsid (VCA), Early (EA), and Membrane (MA), and Nuclear (EBNA) at the very end.
Class and exam questions
Why is the virus shed in saliva for so long during mononucleosis?
In the epithelial cells of the oropharynx and the excretory ducts of the salivary glands, EBV replication is accompanied by cell destruction (lysis). New virions continuously enter the saliva, where they can be detected for up to 12–18 months.
What is B-lymphocyte immortalization?
This is the phenomenon of "cellular immortality." Epstein-Barr virus blocks the natural process of B-cell apoptosis, forcing it to divide continuously and transmit viral DNA to all daughter cells.
In what form does the virus persist in the body during chronic infection?
In the latency phase, the viral DNA is stored inside the nucleus of the infected B-lymphocyte as an episome—an extrachromosomal resting closed circular structure.
What else to study on this topic
- Criteria for assessing severity and clinical periods of IM
- Differential diagnosis of mononucleosis-like syndrome
- Decoding the hemogram: morphology of atypical mononuclear cells
- Specific EBV markers in ELISA and PCR
- Indications for glucocorticoids and antiviral therapy
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