Ebola Virus Life Cycle: Definition & Stages

Instructor: Adrianne Baron

Adrianne has a master's degree in cancer biology and has taught high school and college biology.

The Ebola virus has caused many casualties in recent years. This lesson looks at the life cycle of the Ebola virus as well as possible therapeutic targets that could prevent the disease.

Ebola Virus

Do you remember the year 2014? You probably had goals and plans set for that year. Things were going very well the first couple of months, and then in March, you started hearing about a very deadly outbreak of Ebola. Ebola is a hemorrhagic fever disease caused by the Ebola virus. The Ebola virus is a piece of single stranded RNA, polymerase, and proteins encapsulated in a viral envelope.

Stained micrograph of the Ebola virus
Stained micrograph of the Ebola virus

Like most viruses, the Ebola virus needs a host in order to multiply. That's where people come in. However, we aren't the only options for a host; the virus can also use rodents, bats, and other mammals. The virus' journey doesn't end after it find its host, however; several things occur afterwards. Let's look at what the virus goes through during its life cycle.

Life Cycle

The life cycle of the Ebola virus begins with the extracellular virion, or enveloped virus outside of a cell or host. Once it finds a host, the virus has to make its way inside. This usually occurs through the mucosal membranes such as the nose, mouth, or open wounds. The virion attaches to a receptor on the surface of a cell. The cells that are used the most are dendritic, endothelial, and other immune cells. Once the virion is attached, the membrane of the cell will engulf the virion and give it entry into the cell.

The second step in the life cycle is recruitment of two host proteins, Cathepsin B and L, to process the glycoprotein. The virus needs glycoprotein in order to be released from the vesicle that transported it into the cell. It causes the membranes of the vesicle and the virus to fuse together. Once this fusion occurs, ribonucleocapsids are released from the vesicle.

Next, the negative single-stranded RNA of the Ebola virus is transcribed into strands of viral mRNA, which are pieces of RNA that contain the directions for producing more viral RNA and its associated proteins. After the viral mRNA is finished being transcribed, it moves through the cytoplasm to the nucleus of the cell. The viral mRNAs are not alone, however. They are accompanied by VP 30, a viral protein necessary for replication of RNA, polymerase, and nucleocapsids.

Now, the polymerase, along with the replication mechanisms of the host cell, begin replication of the virus. The products of this replication are multiple strands of negative single-stranded RNA. The newly replicated strands of viral RNA get encapsulated by the nucleocapsids in the nucleus. During this point in the cycle, the nucleus releases the encapsulated virus.

During the last step of the cycle, the newly produced encapsulated virus is transported to the membrane of the cell. The nucleocapsid surrounding the virus interacts with the budding mechanism of the cell. This interaction allows the encapsulated virus to be released by budding off from the cell membrane. At this point, it now becomes a new extracellular virion and the cycle starts over.

Therapeutic Targets

The life cycle of the Ebola virus is rather interesting, but there are parts of the process that researchers do not understood very well. This is the main obstacle when trying to figure out ways to stop the viral cycle. However, there are a few possibilities that are beginning to show some promise. The best way to stop a viral cycle is to target its specific parts.

The first thing that the Ebola virus requires is the ability to attach to the cell membrane in order to gain entry into the cell. To prevent this, an antibody could be produced that binds to the receptor on the cell membrane surface. If the antibodies are there, then the receptors are already attached to something, so the virus is unable to attach itself. It may also be possible to create a molecule that will bind to the glycoprotein of the virus, which would make it unable to gain entry.

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