Lymphocryptovirus

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Mononucleosis viral cell under microscope. Image credit:https://userfiles.steadyhealth.com/images/ic/how-do-you-get-mononucleosis.jpg.

Classification

Virus; Peploviricota; Herviviricetes; Herpesvirales; Orthoherpesviridae

Species

NCBI: [1]

Lymphocryptovirus

Description and Significance

Lymphocryptovirus is a virus that can affect primates and has an icosahedral capsid. This virus is also commonly known as Epstein-Barr virus. This virus can have long term effects on humans and can cause many other health problems in the future if infected by. There is no cure for this virus, but research has found that in later stages it is linked to cancer found in the lymphatic system. It is mostly spread through oral saliva or an infected object.

Genome Structure

This genome is linear, double-stranded DNA and approximately 170 kilobases in size. The genome is contained into a single chromosome which encodes over 80 genes. The genome sequence contains terminal repeats that facilitate circularization during latency, allowing it to persist as an episome within the host cell nucleus.

Cell Structure, Metabolism and Life Cycle

Similar to other members of the Gammaherpesvirinae subfamily, Lymphocryptovirus particles are enveloped and ~120-200 nm in diameter. The virus has an icosahedral capsid, tegument layer, and a glycoprotein embedded lipid envelop for host cell entry. (Johanson et all., 2004 ; Epstein et al., 1964) The double-stranded DNA is packaged with the capsid.

Lymphocryptovirus is metabolically dependent on its host, hijacking cellular pathways to replicate. The virus t enhances glycolysis and glutaminolysis during infection to support its replication.

The life cycle of Lymphocryptovirus alternates between lytic and latent phases. In lytic replication, the virus produces progeny in epithelial cells. In latent phases, it persist as a circular episome with minimum gene expression to avoid immune detection (Thorley-Lawson & Gross, 2004). Host specificity is mediated by interaction between viral glycoproteins and receptors like CD21 (Finegeroth et al., 1984).

Ecology and Pathogenesis

The Lymphocryptovirus is found in both Old World and New World primates. This includes humans being a host. The Epstein-Barr virus is a type of Lymphocryptovirus that causes mononucleosis in humans. They can be mutualistic to their host, giving a benefit to both the host and it. In this mutualistic relationship, the Lymphocryptovirus can immortalize host cells to express viral genes. This encourages diversity and evolution within the host cells. This virus has a biochemical significance in acting as an ecologic and biological marker for abnormal activity. If the virus is in high levels in the environment, this can indicate pollutants, unusual bacterial activity, or the need for ecosystem modifications.

The Lymphocryptovirus causes infection in the B lymphocytes, allowing it to be dormant and reactivate in certain conditions, which can lead to increased levels of cell proliferation. This can eventually lead to lymphoma as the cells overgrow and group together into a tumor. It is most common to infect those already immunocompromised systems as the B lymphocytes are weaker this way, allowing for an easier attack.

This virus has many virulence factors which include latency, lymphotropism, proliferation, shedding, reactivation, oncogenic factors diseases, and immune suppression. With latency, the disease can sit dormant in cells and persist within the host for the entirety of the host's life span. It is lymphotropic, meaning it has the ability to infect lymphocytes, such as B lymphocytes. The oncogenic factors include the ability to become proto-oncogenes, which will eventually develop into cancer. In patients, symptoms of the virus include sore throat, fatigue, fever, swollen lymph nodes, rashes, and enlarges spleen and liver.

References

Ensser A. (2008).“Simian Gammaherpesviruses”. Encyclopedia of Virology. Volume 3. p.585-594.

Epstein, M. A., Achong, B. G., & Barr, Y. M. (1964). Virus particles in cultured lymphoblasts from Burkitt’s lymphoma. Lancet, 1(7335), 702–703.

Fingeroth, J. D., et al. (1984). Epstein-Barr virus receptor of human B lymphocytes is the C3d receptor CR2. Proceedings of the National Academy of Sciences, 81(14), 4510–4514.

Henson B, Perkins E, Cothran J, Desai P. (2009).Self-Assembly of Epstein-Barr Virus Capsids. Journal of Virology. 83(8):3877–3890

Johannsen, E., et al. (2004). Proteins of purified Epstein-Barr virus. Proceedings of the National Academy of Sciences, 101(46), 16286–16291.

Thorley-Lawson, D. A., & Gross, A. (2004). Persistence of the Epstein-Barr virus and the origins of associated lymphomas. New England Journal of Medicine, 350(13), 1328–1337.

Author

Page authored by Finley Walker, Molly Cooper, Brooklyn Justice, & Kandace Stephenson, students of Prof. Bradley Tolar at UNC Wilmington.