Antibodies to Trypanosoma Glycoprotein Variants Over Time
Sleeping sickness is caused by the unicellutar Trypanosoma parasite. The surface of this parasite is covered by glycoproteins that are encoded by a gene with more than 1,000 duplications in the trypanosome genome. Each of the gene copies is slightly different and has different molecular structures. The data below show the number of parasites over time (A) and the relative amount of antibodies specific to two trypanosome glycoproteins (B) over 24 days of a human infection, and the index varies from no antibodies (0) to many antibodies (1)
Part A: Data from a Study of Parasite Levels
Day
4
6
8
10
12
14
16
18
20
22
24
Number of Parasites (in millions) per mL of Blood
0.3
0.2
0.2
0.7
0.2
0.1
1.2
0.9
1.2
0.6
0.1
Part B: Data from a Study of Antibody Levels
Day
4
Antibody Specific to Glycoprotein Variant A
0
6
0
8
0.2
10
0.5
12
1
14
1
16
1
18
1
20
1
22
1
Antibody Specific to Glycoprotein Variant B
0
0
0
0
0
0.1
0.3
0.9
1
1
24
1
1
Use the passage to answer the question.
Based on the data provided in part A of the passage, there are parasite load decreases followed by increases. Justify
how trypanosome biology and features of the immune system could interact to result in this varying parasite load.
As one glycoprotein variant becomes recognized and attacked by the adaptive immune system, another glycoprotein that is not yet recognized is able to persist.
The longer the glycoprotein variants persist in the body, they attack and impair the immune system over time.
As both glycoprotein variants become recognized by the innate immune system, the parasite load levels fall until the Immune system can no longer detect the parasite, which allows the trypanosome to thrive.
As antibody leveis increase, the parasites with the associated glycoprotein variant are able to evade detection by the adaptive immune system.
(1 point)