What is a potential problem with the use of diphtheria toxin as an immunotoxin? Can the use of anthrax toxin overcome this problem? Do vaccines necessarily work better if they target virulence factors...

What is a potential problem with the use of diphtheria toxin as an immunotoxin? Can the use of anthrax toxin overcome this problem?

Do vaccines necessarily work better if they target virulence factors than if they target molecules not involved in virulence? Explain why or why not.