What are three major ways in which a virus enters a host cell to deliver its genome?

Questions

1. Examine the diagram (Figure 4, next page) showing the life cycle of the Ebola virus. a. Label the fi ve major steps used by Ebola virus to infect cells. In what specifi c ways are these similar or

diff erent from those you labeled in the general virus life cycle?

i. __________________________

ii. __________________________

iii. __________________________

iv. __________________________

v. __________________________

Key similarities and diff erences:

b. Label the key viral and cellular factors in the indicated areas of the diagram. Describe each of their roles.

2. Formulate a hypothesis as to what would happen to viral replication and budding from the cell if the ribosomes did not make VP40.

3. What is one structural component of the Ebola virus to target for a vaccine that prevents infections like Terry’s? Explain your answer. Keep in mind the Ebola virus structures and that vaccines are developed to prevent viral infections (for example, the fl u vaccine contains a weakened form of the infl uenza virus that does not cause disease).

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Part V – Treatment Terry’s doctor knew quick action was necessary to help her survive the Ebola infection. Th e doctor had four options to treat Terry’s condition: a vaccine, a standard antiviral medication, an immunotherapy-based method of treatment, and serum from an Ebola patient who had fully recovered.

Th e fi rst option, a vaccine in clinical trials, could potentially provide protection against a viral infection when used prior to contracting the disease. Vaccines typically introduce the body to an antigen, consisting of the dead virus, or parts of a virus, such as a specifi c glycoprotein from the viral protein coat/envelope. Th ese non-self antigens are considered foreign to the body and invoke an immune response where antibodies are made against the viral protein in the vaccine. Once antibodies are made and circulated throughout the body, they can attach to the viral antigens and the immune system destroys the antigen. Th is immune response takes time.

When considering the second option, Terry’s doctor thought about antiviral therapies for other viruses, like the fl u. She knew that with infl uenza infection, the antiviral medicine Tamifl u™ was only eff ective if administered within the fi rst 48 hrs of infection. Unfortunately, Terry was in late stages of the disease, and there were no such approved Ebola- specifi c antiviral medicines currently available for use.

Th e third option was immunotherapy with the investigational treatment ZMapp.™ ZMapp is a treatment method that uses three unique antibodies against Ebola GP made in tobacco plants. While there had not been any large-scale human trials at the time of Terry’s infection, when these antibodies were injected into Ebola-infected mice and rhesus macaque primates, the animals showed increased survival. As such, ZMapp was thought to be a potentially eff ective antiviral/immunotherapy-based treatment for Ebola infections in humans, and in a few cases was used to treat human Ebola patients during the 2014 outbreak. Although the mechanism of action for ZMapp had not been elucidated yet, researchers believed that since the antibodies in ZMapp bound to the glycoprotein (antigen) on the Ebola virus, it prevented viral attachment to the cells and thus did not allow entry or viral replication.

A fi nal option would be to give Terry serum from a patient who had recovered from an Ebola infection of the same strain. Th is serum would be rich with Ebola-specifi c antibodies to enhance Terry’s immune response. However, this method of treatment required identifying an Ebola virus survivor who had blood type compatibility with Terry and who was willing and able to donate serum in a timely fashion.

Question

1. Synthesize the information provided above. Come up with an argument as to the best treatment plan for Terry.

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Case copyright held by the National Center for Case Study Teaching in Science, University at Buff alo, State University of New York. Originally published February 9, 2016. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work. Licensed image in title block ©Ezume Images | Fotolia, id#93050805.

Part VI – Recovery Terry’s symptoms cleared and she was virus free. Th e battle was now over and Terry’s cells won. One would never know whether it was the treatment, Terry’s own immune system, or a combination of the two that won the war against Ebola. In the end, Terry survived the potentially-deadly infection and was able to return home without any long-term eff ects, other than a newfound understanding and appreciation of how viruses, like Ebola, replicate and cause disease.

Victory at all costs, victory in spite of all terror, victory however long and hard the road may be;

for without victory, there is no survival.

—Winston Churchill—