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Plate 34

Antiviral Vaccines & Drugs

Vaccines

• A vaccine stimulates the body to make proteins that destroy specific foreign organisms.

Vaccine History

• 1700s, Edward Jenner, an English scientist, noticed that milkmaids did not get smallpox

• Milkmaids commonly became infected with cowpox, which is similar to smallpox, but much more mild

• 1796, Jenner took pus from a milkmaid’s hand, injected it into a young boy, then inoculated the boy with smallpox – the boy never contracted smallpox

Antigens

• Antigen – a substance that causes the production of antibodies in the immune system

• Derived from the term antibody generator• Typically made of proteins or polysaccharides

Antibody

• Antibody – an immune system protein found in the blood that identifies and neutralizes antigens

• Antibodies have binding sites that recognize specific antigens

• Vaccines stimulate antibodies without harmful effects

Vaccine Production• Vaccines are produced by

cultivating living viruses in a tissue culture

• After a significant quantity of viruses have replicated, a physical or chemical agent is used to inactivates the virus

• Inactivated viruses still stimulate antibody production in the host, but don’t cause the disease

Warm-Up

How do vaccines work?

Attenuation• Attenuation – the process of

using a “live” pathogen to create immunity

• Attenuated viruses pass through a foreign host (ex: an egg) first, and specific viruses are selected for the vaccine

• A mutated virus may survive well in the new host, but is now harmless in the original host

Benefits of Attenuated Vaccines

• Since the virus is still alive, it will continue to replicate, but slowly – thus, boosters aren’t required as frequently

• Activates entire immune system

• Inexpensive

Drawbacks of Attenuated Vaccines

• Small chance that the virus may become virulent again

• May cause disease in people with weakened immune systems

• Can be difficult to transport – need to keep viruses “alive”

Vaccine Injections & Boosters

DNA Review

• A nucleotide is formed from a nucleoside (nitrogenous base + sugar) and a phosphate group

• During viral replication, nucleotides are linked by polymerase enzymes

Acyclovir

• A drug that is classified as a “chain terminator” and acts as a “false nucleotide”

• During viral replication, the acyclovir is attached to the nucleotide in front of it, but lacks an attachment point for the next nucleotide

Acyclovir• Brand name: Zovirax• Used to treat people with

chickenpox, shingles, and genital herpes

• Doesn’t cure people with these diseases, but stops the spreading of the virus in your body