Paramyxovirus

By Maura Allen and Lisa Walker

An Introduction to Paramyxovirus

Paramyxovirus is a family of viruses that is most commonly associated with measles, mumps, and rubella, also known as German measles. The virus also causes RSV, which can lead to more serious respiratory conditions like pneumonia if it infects infants or the elderly, newcastle disease, parainfluenza, the sendai virus, and the hendra virus.

A History of Paramyxovirus

Little was known about the paramyxovirus until recently, except in the context of measles and mumps. Mumps was first identified by the ancient Greeks, and measles is thought to have evolved from a similar animal virus in the Babylonian era. Other forms of paramyxovirus exist, including various forms of the virus that attack different animals like iguanas and an avian form exists that attacks birds. The avian form is called Newcastle disease, and a form of it causes Canine Distemper in dogs.

Structure of the Virus

The genetic material (single stranded RNA) of the virus, RdRp, a protein that it uses to reproduce, and additional proteins that the virus needs are contained in a nucleocapsid, which is the membrane around a virus that is made with nucleic acids. There are some functional proteins that help the virus attach to, and infect a host cell that are located on the surface of the nucleocapsid and look like spikes on its surface.

Infecting the Host Cell

Paramyxovirus has various attachment proteins all over the capsid that stick out as spikes. Theses spikes bind to the sialic acid that is present on the surface of most animal tissue cells and especially on blood cells. These proteins also facilitate the virus’s entrance into the cell.

The labels refer to proteins of the virus. HN is the attachment protein for this virus.

Nucleic Acid in the Virus

The paramyxovirus contains negative-sense, single stranded RNA. All viruses that contain negative sense, single stranded RNA replicate the same way. Negative-sense refers to the fact that this RNA cannot directly direct the formation of any proteins. For this to happen, it must be converted into positive sense RNA, which is then used in the same way as mRNA inside the host cell. More information on the replication of the virus will be covered later.

Replication of the Genome

Replication of the paramyxovirus genome, which consists of 6-10 genes, takes place in the cytoplasm of the host cell. The RNA of the virus is translated into positive sense RNA through use of the enzyme RdRp, which is short for RNA-dependent-RNA-polymerase. The positive sense RNA can then act as mRNA which is read by the host cell, and the host cell’s mechanisms build the necessary proteins, as well as gets copied into more negative sense RNA to use in the daughter virus.

Replication of the Virus

Once the RNA has been replicated it is easy to make a new virus. The positive sense RNA created by the virus is then interpreted by the host cell the same way mRNA would be. Because of this, the host cell then begins making the proteins that the virus needs. Because the nucleic acid and the proteins of the virus have been replicated, the virus can now be constructed. The new virons are released from the cell through the lytic cycle: the cell explodes to release them.

Mumps

Mumps is one of the many diseased caused by a virus in the paramyxovirus family. It is characterized by the swelling of the salivary glands. There is no cure for mumps. Symptoms are treated, but otherwise most commonly, people just wait for it to go away. There are rarely complications. Mumps has become less common since the MMR vaccine became more widespread. (MMR stands for Measles, Mumps and Rubella, which are the most common diseases caused by the paramyxovirus.)

Measles

Measles is a highly contagious disease caused by the paramyxovirus. 90% of the people exposed to the virus contract the disease. The symptoms are a fever, cough, runny nose, rash, and red eyes. Again, there is no specific treatment for the disease, but it has become much less common with the increased used of the MMR vaccine.

Rubella

Rubella, or the German measles is the third most common disease caused by paramyxovirus. It is also called the 3-day measles because the symptoms only last around 3 days in children, although they can last longer in adults and teens. The symptoms are a swelling of the lymph nodes in the back of the neck and a mild fever. The most obvious symptom is a rash that travels from the face down across the rest of the body, a rash similar to the measles rash, which is why it is commonly associated with measles. The symptoms quickly dissipate, and there is no actual treatment for the disease. The symptoms can be treated, and the disease is only dangerous when pregnant women contract it, because they can pass it to the fetus who can get congenital rubella which can cause severe developmental complications. The MMR vaccine, however has drastically reduced the cases of Rubella.

Bibliography

Content: http://web.uct.ac.za/depts/mmi/stannard/paramyx.html http://en.wikipedia.org/wiki/Paramyxovirus#Physical_structure http://kidshealth.org/parent/infections/skin/german_measles.html http://www.microbiologybytes.com/virology/

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Images:o http://faculty.ksu.edu.sa/70714/Pictures%20Library/Viruses%20Pi

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o http://www.foxnews.com/images/392744/0_61_320_measles.jpg o http://www.idph.state.il.us/images/mumps.jpg o http://upload.wikimedia.org/wikipedia/commons/0/03/Rubella.jpg o http://www.wendyleesshihtzu.com/images/Paramyxovirus_Distem

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o http://www.mcb.uct.ac.za/tutorial/v.html