TUTORIAL 5
Multiple Choices
For each of the questions below select the one best answer.
1.
Western assays used to test serum samples for the presence of antibodies to infectious agents, such as HIV, are particularly useful as diagnostic assays because
A.
they are more sensitive than ELISA.
B.
antibodies specific for multiple antigenic epitopes can be detected.
C.
they allow multiple samples to be tested simultaneously.
D.
they are less expensive and take less time to perform as compared with ELISA.
2.
An ELISA designed to test for the presence of serum antibody for a new strain of pathogenic bacteria is under development. Initially, a monoclonal antibody specific for a single epitope of the organism was used both to sensitize the wells of the ELISA plate and as the enzyme-labeled detecting antibody in a conventional sandwich ELISA. The
ELISA failed to detect the antigen despite the use of a wide range of antibody concentrations. What is the most probable cause of this problem?
A.
The antibody has a low affinity for the antigen.
B.
The monoclonal antibody used to sensitize the wells is blocking access of the epitope, thus when the same antibody is enzyme-labeled, it cannot bind to the antigen.
C.
The enzyme-labeled antibody used should have been a different isotype than the sensitizing antibody.
D.
The monoclonal antibody used is probably unstable.
3.
The indirect Coombs' test (anti-immunoglobulin test) typically uses:
A.
Patient's red cells to determine whether they will bind IgG
B.
Patient's serum to determine whether it forms a precipitate with donor plasma
C.
Patient's serum to determine whether it contains antibodies that bind to a variety of reagent red cells
D.
Patient's serum to determine whether it contains antibodies that bind to the patient's red cells
4.
The usual sequence of events in the development of an effective immune response to a viral infection is
A.
Antibody synthesis, interferon secretion, NK cell ADCC, cellular immune response.
B.
NK cell ADCC, interferon secretion, antibody synthesis, cellular immune response
C.
Interferon secretion, cellular immune response, antibody synthesis, NK cell ADCC.
D.
Cellular immune response, interferon secretion, antibody synthesis, NK cell ADCC.
5.
Antigenic variation is a mechanism of immune evasion that results in
A.
interference with attachment to host receptors.
B.
induction of immune suppression.
C.
alterations in important surface antigens.
D.
destruction of antigens by proteolytic enzymes

6.
The best way to provide immunologic protection against tetanus neonatorum (of the newborn) is to
A.
inject the infant with human tetanus antitoxin.
B.
inject the newborn with tetanus toxoid.
C.
inject the mother with toxoid within 72 hours of the birth of her child.
D.
immunize the mother with tetanus toxoid before or early in pregnancy.
7.
Active, durable immunization against poliomyelitis can be accomplished by oral administration of attenuated vaccine (Sabin) or by parenteral injection of inactivated
(Salk) vaccine. These vaccines are equally effective in preventing disease because
A.
both induce adequate IgA at the intestinal mucosa, the site of entry of the virus.
B.
antibody in the serum protects against the viremia (virus in the blood) that leads to disease.
C.
both vaccines induce formation of interferon.
D.
both vaccines establish a mild infection that can lead to formation of antibody.
8.
The administration of vaccines is not without hazard. Of the following, which is least likely to affect adversely an immunocompromised host?
A.
Measles vaccine
B.
Hepatitis B vaccine
C.
Bacille Calmette-Guerin
D.
Sabin poliomyelitis vaccine

Structure Questions
1.
You are a medical doctor looking after 4 patients who are suspected to have been infected by H1N1 inf1uenza virus at different points of time. The report card below shows the test results for virus and antibody in the patients' blood samples:
Patients
Peter
Nancy
Andrew
H1N1 virus
Present
Absent
Present
Anti-H1N1 IgM
High
None
None
Anti-H1N1 IgG
Low
None
None
Jane Absent Low a) Who is/are having an active infection? Explain your answer.
High b) Among the 4 patients here, who is most likely to be the first patient infected by the virus? Give reasons for your answer. c) Andrew shows serious symptoms of H1N1 infection but has not yet developed antibodies. Conventional drug treatments do not improve Andrew's condition and you decide to treat him with passive immunization using either Peter's or Jane's serum. Whose serum is preferred and why?
2.
A chemist managed to isolate a novel protein (HepKP) from the capsid of Hepatitis A virus. This is an 8kd protein. He wanted to test if this protein has the potential to be developed into a subunit vaccine in future. He started by injecting the mouse with this protein and test for antibody production. This is the protocol:

Dissolve HepKP in saline at 35~g/ml
 Inject 100μl of of HepKP solution intramuscularly into the mouse

Inject the first booster one week later

Apply 2 more booster shots one week apart

Bleed the mouse on week 5 to check for anti-HepKP production
The chemist was disappointed by the immunization result and he approaches you for advice. What suggestions would you give him to enhance the production of anti-HepKP antibody from mouse?