Lecture 19 Viral Vaccines

For the final

Variolation

Small dose of a virulent virus

Why could smallpox be eradicated?

No animal reservoirs

The vaccine was effective

Lifelong immunity (not antigenic shift or drift)

Inactivated viruses

Cannot infect but expose person to viral antigens

Live attenuated virus vaccines

Infect but don’t cause disease

Subviral/Subunit vaccines

Contain only a subset of viral proteins

Nucleic acid vaccine

DNA or mRNA that produces viral antigens after injection

Recombined virus vaccine

Harmless recombined viruses that produce antigen from virulent virus

Advantages of live attenuated viral vaccines

• Natural infection route w/ better immune responses

• Effective in small amounts

• Long/lifetime immunity

• Don’t need adjuvants

Disadvantages of life attenuated viral vaccines

• Reversed to virulence (Polio)

• Can form recombinants

• Vaccine itself may cause outbreaks in immunocompromised individuals

• Doesn’t always “take;” can be interfered with

• Expensive & unstable

T/F: Inactivated viral vaccines trigger both T and B cell mediated immune responses

False

Do inactivated viral vaccines trigger both T and B cell mediated immune responses?

No, they only trigger B cell mediated responses

Is it appropriate to inoculate immunocompromised individuals with live attenuated virus vaccine?

No. They can cause diseases in these individuals

mRNA vaccines

Vaccine that teaches cells to make a protein to trigger an immune response

Advantages of mRNA vaccines

• High potency

• Can rapidly develop

• Potentially cheaper to manufacture

• Safe administration

• No risk of integration (unlike DNA)

Why isn’t there an available HIV/AIDS vaccine yet?

1) It kills key immune cells (CD4)

2) Can remain latent w/o producing viral proteins

3) High mutation rate

4) Has various evasion strategies

Herd immunity

Risk of disease dramatically lowered when notable percent of population are vaccinated

Interrupts transmission of disease

Advantages of inactivated virus vaccines

• Polyvalent: multiple strains/viruses in one vaccine

• Stable

• Safe for immunocompromised

• No natural spread

Disadvantages of virus vaccines

• Requires complete inactivation

• Need adjuvants

• Need larger doses

• Shorter period of immunity

• Incomplete cellular response