An immunoassay was developed to rapidly diagnose patients infected with an emerging virus. However, the researchers discovered that some individuals were producing false negatives when tested, despite being infected with the virus. What might explain this?
A. Rapid evolution of the viral antigen
B. Changes in the length of the viral DNA
C. Number of genome copies carried in each virion
D. Changes in the antibody produced by the virus
Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
Gather Content
· What do you already know about immunoassays?
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
A. Rapid evolution of the viral antigen
Clarify Question
· What is the key concept addressed by the question?
o This question addresses immunoassays.
· What type of thinking is required?
o This question is asking you to analyze the information given, using logic, to dissect the problem and determine the answer.
Gather Content
· What do you already know about immunoassays?
o Immunoassays can rapidly diagnose viral infections. They are tests that allow the detection of a molecule through the use of an antibody.
o Biotechnology companies can make antibodies against a range of viruses and bacteria. These antibodies can be used in immunoassays to detect whether there is virus in a sample collected from a patient. An antibody against a specific virus can be coated into a plastic well on a microtiter plate. When an unknown sample is added to the well, if the virus is present, it will be bound by the antibody. Bound virus can be detected using a second antibody against the virus that has been linked to a fluorescent molecule, or an enzyme that produces a colored product from a suitable substrate. The amount of fluorescence or colored product made by the enzyme, is proportional to the amount of virus present.
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
o The antibody is part of the test; the antigen is made by the virus.
o The best explanation for failure of the immunoassay is that the detected antigen has changed, so it is no longer recognizable by the antibody in the test.
o The antibodies in an immunoassay can recognize the proteins on the outside of a virus coat, but they cannot recognize features of the viral DNA itself.
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
o The question required you to analyze the information given, using logic, to dissect the problem and determine the answer.
o Did you recognize that immunoassays rely upon the ability of the antibody to recognize a certain viral antigen protein?
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