There is to be NO COLLABORATION for this test and students are expected to submit their own work with no help from others. Any work found to have been copied or plagiarised from other sources will result in a mark of zero.
PLEASE NOTE: The points value given to each question should determine the length of your answer.
e.g. A question worth 1 mark should not be a paragraph long, and require just a sentence or two. Conversely, a question worth 5 marks will require more than one sentence.
ANSWER ALL QUESTIONS ON THIS DOCUMENT.
SECTION A (15 marks total)
Question 1:
A live attenuated vaccine generally elicits a stronger and longer lasting immune response than a subunit vaccine. Briefly discuss why this is the case. (5 marks)
How would you improve the immunogenicity of a subunit vaccine? (3 marks)
Question 2:
Explain the difference between a single cycle and replication defective virus in terms of their form of attenuation as well as their presentation to the host immune system as a vaccine.
(5 marks
Question 3:
What is herd immunity and why is it important?. (2 marks)
SECTION B (30 marks total)
Question 4:
You will need to read the article cited below to answer the questions in this section:
An Optimized Synthetic DNA Vaccine Encoding the Toxin A and Toxin B Receptor Binding Domains of Clostridium difficile Induces Protective Antibody responses In Vivo (2014)
Scott M. Baliban et al. Infect. Immun. 82(10):4080.
The following questions relate to the figure below (Figure 1, Panel A).
Figure 1, Panel A
- TcdA RBD and TcdB RBD are the gene constructs used in the DNA vaccine vectors. What do each of these antigens represent, and give reasons as to why they were used. (4 marks)
- What is CMV and why is it important in terms of the DNA vaccine construct? (2 marks)
- What is hlgE, and what is its purpose in the vaccine construct? Why is it important?
(3 mark
- What does the NQ in the Tcd A/B RBD-NQ refer to? Why was it done? (2 marks)
Question 5:
The following questions relate to the figure below (Figure 4)
Scott M. Baliban et al. Infect. Immun. 82(10):4080
Figure 4
Survival of immunized mice challenged with TcdA and TcdB. (A) An immunization and challenge schedule for mice is shown. C57BL/6 mice (n _10/group) were immunized as described in the text and rested for 8 weeks before being challenged intraperitoneally with a lethal dose of C. difficile toxin. (B and C) Animals immunized with pARBD-NQ (B) or pBRBD-NQ (C) were challenged with 300 ng of TcdA or 150 ng of both TcdA and TcdB, respectively. i.p., intraperitoneal; ctrl, control. *, P _ 0.05; ***, P _ 0.001.
(a) Why were mice rested for 8 weeks after immunisation before being challenged? (1 mark)
(b) Why was a lethal dose of C. difficile toxin and not the actual C. difficile strain used in this challenge experiment? What are they trying to show? (3 marks)
(c) Why is there a difference in survival between Panel B and Panel C? (it is not sufficient to say pARBD-NQ was used for one and pRBD-NQ was used for the other)
What is used as the control (3 marks)
Question 6:
The following question [parts (a) and (b)] relates to the figure below (Figure 2, Panel B).
Scott M. Baliban et al. Infect. Immun. 82(10):4080
Figure 2: (Panel B) After the third immunization, total serum anti-RBD IgG responses were measured by ELISA.
(a) Explain why there is a difference in antibody response when 10µg or 25µg of plasmid pARBD-NQ (upper graph) is used, but no difference is seen when 10µg or 25µg of plasmid pBRBD-NQ (lower graph) is used? (3 marks)
(b) Using the data from the above graphs, can you say anything about the protective function of the antibodies? Why or why not? (2 marks)
Question 7:
The following question [parts (a) and (b)] relates to the figure below (Figure 7, Panels B and E).
Scott M. Baliban et al. Infect. Immun. 82(10):4080
- What is the difference in the challenge model used here and that used in Figure 4? Why is it important to use different challenge models? (3 marks)
- Why is there a difference in the survival rate between panels B and E? What does this show and is it important? (4 marks)
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