In a Clinical Trial of a New Antiviral Vaccine Composed

question 13

Multiple Choice

In a clinical trial of a new antiviral vaccine composed of a recombinant viral peptide and adjuvant, 4% of the healthy recipients did not show evidence of response to the immunization. Further investigation revealed that all the nonresponders expressed the same, single allelic variant of HLA-DR but all the responders were heterozygous for HLA-DR alleles. Which of the following is the most likely explanation for this finding?

• A)Response to the vaccine requires T cell recognition of complexes of the viral peptide with HLA-DR, but the peptide cannot bind to the allelic variant of HLA-DR found in the nonresponders.
• B)The nonresponders could not express class II MHC proteins.
• C)The viral peptide is not an immunodominant epitope.
• D)The nonresponders underwent determinant selection of another viral epitope.
• E)Because of technical errors, the nonresponders had not received adequate doses of the vaccine.

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