Epstein Barr Virus: Properties of the Virus

Epstein–Barr Virus

Epstein–Barr virus (EBV) or human herpesvirus 4 (HSV-4) is the causative agent of infectious mononucleosis. Epstein–Barr virus is also the first virus known to be associated with human malignancies, such as Burkitt’s lymphoma, other B-cell lym-phoma, and nasopharyngeal carcinoma. It also causes other lymphoproliferative disorders in immunodeficient individuals. Epstein–Barr virus is a gamma herpesvirus belonging to subfamily Gammaherpesvirinae. It shows very limited host specificity.

Properties of the Virus

◗ Morphology

Epstein–Barr virus shows following features:

·          It is an enveloped DNA virus. It consists of a genome, a capsid, and an envelope.

·        The genome consists of a 172 kbp, linear dsDNA. It is surrounded by an icosahedral capsid composed of capso-meres. Both the capsid and the genome, which form the nucleocapsid, are enclosed by an envelope containing gly-coproteins. The envelope is derived from the outer nuclear membrane of host cell and contains many proteins, which are expressed for different types of infections.

·          The viral capsid antigen (VCA) is the most important anti-gen present in the capsule and is of diagnostic importance. Neutralizing antibodies are produced against the viral membrane antigen. The early antigens (EAs), Epstein–Barr nuclear antigen (EBNA), lymphocyte-determined membrane antigen, and viral membrane antigens are other antigens of diagnostic importance.

The EBV enters B lymphocytes at the site of receptor for the C3 component of the complement. The virus replicates in cyto-plasm of the infected epithelial cells and the replicative cycle is similar to that of HSV.

◗ Antigenic and genomic properties

Based on differences in the latency nuclear antigen genes, EBV consists of two types EBV-1 and EBV-2, also known as type a and type b strains, respectively. Both the types cause the same degree of clinical illness. They are prevalent throughout the world and can simultaneously infect the same person.

◗ Other properties

Epstein–Barr viruses are sensitive to the action of ether and bile salts. They are relatively fragile and do not survive for a longer period outside the human body fluids.

Virus Isolation and Animal Susceptibility

The virus can grow in human embryonic lung fibroblast cul-ture. The CPE produced by the virus is focal and is associated with refractile ballooning of the cells. The CPE unlike other viruses takes two or more weeks to develop.