Question

Australian antigen for hepatitis b is?

• A. Hb S ag
• B. Hb E ag
• C. Hb D ag
• D. HbV Dna

Answer 1

The Correct Option is A

Step 1: Recall the naming history. In 1965 Blumberg detected a novel serum protein in an Australian aboriginal patient; this discovery later earned a Nobel Prize and the protein kept the nickname $Australia\ antigen$.
Step 2: Subsequent work tied that protein to the outer envelope of the hepatitis B virion, i.e. its surface coat, abbreviated HBsAg.
Step 3: Among the choices, only HBsAg represents the viral envelope protein, so it equals the Australia antigen.
Step 4: Eliminate the rest - HBeAg reflects active replication, HBcAg sits inside the nucleocapsid and is not free in plasma, and HBV DNA is quantified by PCR for viral load. None carries the Australia label.
\[\boxed{\text{HBsAg}}\]