Varicella-zoster Virus (VZV) |
Life Cycle of The varicella-zoster virus
How does vzv reproduce in the cell? The varicella-zoster virus has a reproductive cycle that last about 18 hours. Within that time, VZV used the host cell's enzymes to transcribe its DNA. Both the virus's DNA and the parts needed to assemble the virus's capsid are produced in the nucleus. Herpesviridae, such as VZV, also produce many of their own enzymes involved in metabolism, including those for protein processing. When VZV is not latent, it is perpetually in the lytic cycle, or in other words, the host cells are always destroyed after viral infection and production.
initial infection The varicella-zoster virus is transmitted through the virions on the infected person's skin. These virions are then inhaled by another person and enter his or her respiratory tract via the mucous membrane. VZV then moves from cell to cell without its envelope until it finds and attacks T-cells in the blood. Using these T-cells, the virus is able to migrate to the skin, where it recreates its envelope because the epidermis "lacks the endosomal pathway that removes glycoproteins from the envelope" (3). The now enveloped virus accumulates in the skin, causing the fluid-filled blisters of chicken pox. The viral particles on the skin from these blisters can then infect a new host, repeating the process.
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Latency From the skin cells, the enveloped virion travels to the sensory nerve cells because a gycoprotein called mannose 6-phosphate located in the viral envelope has a corresponding receptors in nerve cells. The virus then proceeds to the sensory ganglia, a collection of cells on the body of neurons. Though there is no immediate affect, VZV can remain latent in the ganglia. During the varicella-zoster virus's latency, there is a "stable maintenance of the viral genome in the nucleus with limited expression of a small subset of viral genes” (2). The latent VZV can then activate, mostly in the elderly and people with weakened immune systems, causing shingles.
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Sources:
- Tortora, Gerard J., Berdell R. Funke, and Christine L. Case. Microbiology. 9th ed. San Francisco: Pearson, 2007. Print
- Roizman, Bernard, and Nina Thayer, eds. "Herpesvirus Properties." Herpesvirus Family: Herpesviridae. Los Alamos National Laboratory, n.d. Web. 8 Apr. 2015. <http://stdgen.northwestern.edu/stdgen/bacteria/hhv2/herpes.html>.
- Dougherty, Matthew. "From Chickenpox to Shingles." In Vivo. Columbia Health Sciences, n.d. Web. 8 Apr. 2015. <http://www.cumc.columbia.edu/publications/in-vivo/Vol1_no7_apr15_02/varicella.html>.
- "Sensory Ganglion." Encyclopedia Brittanica. N.p.: n.p., n.d. Encyclopedia Britannica. Web. 8 Apr. 2015. <http://www.britannica.com/EBchecked/topic/534817/sensory-ganglion>.
heading photo: http://2.bp.blogspot.com/-9pJN62Zrk3Q/Tv50HT3LNrI/AAAAAAAAAZ0/Dm_aW24poOY/s1600/EnvelopedVirus_L.jpg
figure on latency: http://shinglesaware.co.uk/hcp/assets/images/what_is_shingles.shingles_viral_reactivation.image1.jpg
figure on latency: http://shinglesaware.co.uk/hcp/assets/images/what_is_shingles.shingles_viral_reactivation.image1.jpg