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SEU’s capsid symmetry is ___.

Explain how a mutation could decrease the virulence of the virus.  Recall this mutation is in the glycoprotein that mediates membrane fusion.  Answer this question by addressing the prompts A-D below. Which of the viruses is the least virulent?   Provide evidence from the end-point dilution assay to support your answer. (one sentence max) Which step(s) of the infection cycle is affected by this protein. (one sentence max) What is the role of this protein in membrane fusion (you must thoroughly describe the process of membrane fusion and the role of the glycoprotein in the process). (5 sentences max) How would this specific mutation negatively affect membrane fusion. (3 sentences max)

SEU is a(n) [12] virus.

In order for SEU to successfully infect a cell it must enter the cell via [17a], triggered by the attachment of [17b] to the host’s [17c] proteins.

If you wanted to use Koch’s postulates to identify Potato virus as the pathogen responsible for an outbreak on South African farms, which of the following is unnecessary?

Use this prompt to answer questions 10-11. To better understand the importance of MRV’s glycoprotein in the virulence of the virus, researchers have produced mutant viruses with amino acid changes in glycoprotein and tested the virulence of the virus using the end-point dilution assay.   The wildtype virus (WT) has no mutations, C virions have mutations in the cytoplasmic tail, E virions have mutations in the ectodomain and F virions have mutations in the fusion peptide.  The results from the end-point dilution assay for each virus is shown below.

From your experiments (results copied again below) you note the limited tissue tropism of SEU.  Based on this information and your knowledge of the viral infection cycle, explain why the SEU is able to infect some cell lines, but not others.  To completely answer the question you must address the prompts below.  Please label your answers A. through E. List the steps of the infection cycle. (five words max) Identify which step(s) of the infection cycle determines host cell susceptibility.  Explain your answer. (2 sentences max) Identify which step(s) of the infection cycle determines host cell permissiveness.  Explain your answer. (2 sentences max) Determine if each cell line (mouth, tongue and heart) is susceptible and/or permissive and explain your reasoning for each.

The virus’ envelope is composed of… (choose all that apply)

Use this prompt to answer questions 7-11. Visna-maedi virus (VMV) is a retrovirus that causes encephalitis and chronic pnuemonitis in sheep.  VMV has a long incubation time, meaning that infected sheep may not show symptoms until years after infection, giving the virus time to spread through the flock before it is noticed.  Symptoms include relentless loss of weight, breathing issues, coughing and arthritis.  Infections in the brain can lead to paralysis and death.   VMV is part of the genus Lentivirus.  This genus consists of enveloped positive single stranded RNA viruses that can embed their genome into the host’s chromosomes.  This virus enters through membrane fusion at the host’s cell membrane.

What adverse effect is unique to propranolol compared to other beta blockers?