Biology: The Unity and Diversity of Life (MindTap Course List)
14th Edition
ISBN: 9781305073951
Author: Cecie Starr, Ralph Taggart, Christine Evers, Lisa Starr
Publisher: Cengage Learning
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Chapter 20, Problem 1DAA
Adapting to Host Defenses Surface proteins called HLAs allow white blood cells to detect HIV particles and fight an infection. In a recent study, scientists tested whether HIV is adapting to this host defense. They did so by looking at the frequency of a specific mutation (1135X) in HIV. This “escape mutation” helps the virus avoid detection by a version of the HLA protein (HLA-B*51) that is common in some regions of the world, but not in others. FIGURE 20.19 shows the percentage of HIV-positive people who had HIV with the 1135X mutation. Data were collected at medical centers from several parts of the world.
FIGURE 20.19 Regional variation in the frequency of the 1135X escape mutation among HIV-positive people. For each region, pink bars represent the percentage of people whose blood cells have HLA-B*51. and thus cannot detect 1135X mutants. Blue bars represent the percentage of people with other versions of the HLA protein. These people have blood cells that can detect and fight HIV even if it has the 1135X mutation.
1. What percentage of people with H LA-B*51 in Vancouver had HIV with the escape mutation for this protein?
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Several vaccines against viral infections are made by isolating purified surface proteins of the viral particle, mixing them with an adjuvant to stimulate an innate immune response, and injecting the mixture into people. Two examples of this are the vaccine against Hepatitis B virus, and the vaccine against Human Papilloma Virus (the ‘cervical cancer’ vaccine). One interesting property of vaccines of this type (known as ‘subunit vaccines’) is that there is a requirement for a CD4 T cell response to the vaccine antigen in order to generate antibodies to the innocuous protein in the vaccine. In the case of the Hepatitis B vaccine, the viral protein included in the vaccine is the Hepatitis B surface antigen (HepB-SAg), a protein that is approximately 200 amino acids in length. The graph in Figure Q4.27 shows the data from immunizing individuals with this vaccine, and monitoring their production of protective antibody responses to the viral protein.
a) What results would be predicted if…
Let’s say there are two closely related viruses, let’s call them Guernsey virus and Micro virus. These two viruses only infect epithelial cells. Their surface antigens are sufficiently similar that there are a number of shared epitopes between the two viruses. Choose one of the following:
A) If you get infected and successfully recover from one virus, it’s quite possible that you’ll have neutralizing antibodies against the other.
B) If you get infected and successfully recover from one virus, you’ll still be susceptible to the other one because the antigens aren’t exactly the same.
C) If you get infected and successfully recover from one virus, it’s likely that getting infected with the other virus will be worse because of the common phenomena of antibody-dependent enhancement.
D) Not enough information has been given.
Which of the following is false when considering the CCR5Δ32 mutation?
a) The mutation prevents the entry of HIV-1 into a T cell.
b) The deletion that produced CCR5Δ32 caused a frameshift which extends the length of the protein product.
c) CCR5Δ32 prevents infection by HIV-1 in homozygotes but only delays the onset of HIV symptoms in heterozygotes.
d) The protein product produced by CCR5Δ32 is altered in such a manner that it cannot embed in the cell membrane.
Chapter 20 Solutions
Biology: The Unity and Diversity of Life (MindTap Course List)
Ch. 20 - Prob. 1SQCh. 20 - Prob. 2SQCh. 20 - Prob. 3SQCh. 20 - Prob. 4SQCh. 20 - __________ do not reproduce sexually. a....Ch. 20 - Prob. 6SQCh. 20 - Adapting to Host Defenses Surface proteins called...Ch. 20 - Prob. 2DAACh. 20 - Prob. 3DAACh. 20 - Adapting to Host Defenses Surface proteins called...
Ch. 20 - Prob. 7SQCh. 20 - Bacteria that serve as decomposers are ___ . a....Ch. 20 - Prob. 9SQCh. 20 - Formation of a(n) ___ allows some soil bacteria to...Ch. 20 - Prob. 11SQCh. 20 - Prob. 12SQCh. 20 - Which of these diseases is caused by bacteria? a....Ch. 20 - Prob. 14SQCh. 20 - Prob. 15SQCh. 20 - If a cut or scrape becomes infected,...Ch. 20 - The adenoviruses that cause colds do not have a...Ch. 20 - Prob. 3CTCh. 20 - Prob. 4CT
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