True statement about Influenza-A is:
|A||It has a double stranded segmented RNA|
|B||Pandemics are caused by antigenic drift|
|C||Ribonucleoprotein antigen is nonspecific|
|D||Hemaglutinin and Neuraminidase antigens are strain specific|
a. Influenza viruses belong to orthomyxoviruses. These viruses have segmented single stranded RNA.
b. Influenza viruses are divided into three types A, B and C based on the internal or ribonucleoprotein antigen. Pandemics are caused by Influenza A virus.
c. This occurs because of sudden antigenic change due to antigenic shift which occur due to genetic reassortment.
d. Hemagglutinin and neuraminidase are surface, strain specific antigens, which are used for sub typing of Influenza A virus.
Extra Edge: Original antigenic Sin:
a. This term refers to the observation that when a person is exposed to a virus that cross react with another virus to which that individual was previously exposed, more antibody may be produce against the original virus than against the current one.
b. This was observed in people with antibodies to the A1 type of influenzae virus, who, when exposed to the A2 type, produce large amounts of antibody to A1 but very little antibody to the A2 virus. It is also the underline cause of severe hemorrhagic dengue fever.
c. This phenomenon has two practical implication.
d. Attempts to vaccinate people against the different influenza virus strains may be less effective than expected.
e. Epidemiologic studies based on measurement of antibody titers may yield misleading result.