Epstein–Barr virus
المؤلف:
Baijayantimala Mishra
المصدر:
Textbook of Medical Virology
الجزء والصفحة:
2nd Edition , p47-48
2025-07-24
287
The morphology of EBV is grossly similar to other members of Herpesviridae family. EBV is a double-stranded DNA virus. The nucleic acid is surrounded by icosahedral capsid containing 162 capsomers, which again is surrounded by lipid envelop. The diameter of the mature viral particle is 150–200 nm. Viral envelop is acquired from the infected host cell membrane and like other members of the herpes group of viruses, envelop is thought to be acquired from trans-Golgi network. Envelop contains numerous peplomers.
The genome of EBV contains a linear DNA molecule of 184 kbp lengths. The EBV DNA contains several internal repeats interspersed with unique sequences, flanked by terminal repeat sequences. Two strains of EBV exist: 1 and 2 also called A and B. They differ in the domain of viral genome that code for Epstein Barr virus nuclear antigen (EBNA) 2, 3A, B and C and also Epstein-Barr virus encoded small RNA (EBER). Type 1 is more common in Western countries, whereas type 2 is less common in Western countries but more common in African countries. Type 1 is more efficient in transformation of B lymphocyte in vitro as compared to type 2. However, there is no specific disease association with any particular type. Within types, individual isolates differ in the number of tandem repeats in their internal repeats. This heterogeneity can be used to identify the individual isolates, which can be helpful in analysis of epidemiological studies to monitor transmission of the virus.
Near 100 genes are expressed by EBV during viral replication. Of these, ten are associated with latency. EBV nuclear antigen-1 (EBNA-1) binds to the viral DNA and helps the binding of viral DNA to the host cell chromosome in a form of episome. EBNA-2 causes up-regulation of latent membrane protein 1 and 2 (LMP1, LMP2) and also cellular proteins which are responsible for B cell growth and transformation. LMP1 is the major oncoprotein. This activates the transcription factor nuclear factor kB (NF-kB), activation of c-jun, cytokine production and B cell proliferation.
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