Question 178

Question:

After infection with measles virus, a 6-year-old boy produces antibodies to all eight viral proteins. The next year he is again exposed to measles virus. Antibodies to which of the following viral proteins are most likely to be protective?

Correct Answer: A.  Hemagglutinin

Measles is an enveloped, single-stranded, negative sense RNA virus with a helical nucleocapsid. The hemagglutinin (HA) (choice A) viral protein is an envelope protein that binds sialic acid on cells allowing the virus to be endocytosed. Antibodies targeting viral envelope proteins have the best chance of binding their targets and providing the best immunity.
Matrix (choice B), nonstructural (choice C), nucleocapsid (choice D), and polymerase (choice E) proteins are shielded from their respective antibodies by the viral envelope and continue to be hidden once the virus is endocytosed into the host cell. Antibodies to the aforementioned proteins will not provide as much immunity from disease as antibodies to envelope proteins.