This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
All of the following rabies vaccines are commercially available except - 
Select and explain. 
A. Killed sheep brain vaccine, B. Human diploid cell vaccine, C. Vero continous cell vaccine, D. Recombinant glycoprotein
D: Recombinant glycoprotein
Answer: D: Recombinant glycoprotein 
Explanation: Subunit vaccine -The glycoprotein subunit in the virus surface which is the protective antigen, has been cloned and recombinant vaccines produced. They are still in the experimental stage. REF:ANANTHANARAYAN AND PANIKER'S TEXTBOOK OF MICROBIOLOGY 9TH EDITION PAGE NO:536