D7 - Antivirals

• Differences between bacteria and viruses• How does antiviral drugs work?• The AIDS problem

D.7.1

• How do viruses differ from bacteria?

List the differences you know of between bacteria and viruses.

Bacteria Viruses

List the differences you know of between bacteria and viruses.

Bacteria• Microscopic• Has single, circular strand of

DNA—is able to manufacture RNA from the DNA.

• Cell wall• Can reproduce on its own.

Viruses• Submicroscopic• Has either a section of DNA or

RNA surrounded by a coat of packed protein units called capsomeres.

• No cell wall• Can’t reproduce without a

living host. Takes over cell’s machinery to produce more viruses.

D.7.2

• Describe the different ways in which antiviral drugs work

Describe the different ways in which antiviral drugs work.

Well known viral infections• Common cold• Influenza (Including H1N1)• HIV/AIDS• Chicken Pox• Herpes/wartsWhat is the body’s natural defense to viral

infections?

The body’s natural defense to viral infections

• Fever• Coughing• Sneezing• Runny nose• Diarrhea• Vomiting

Different ways in which antiviral drugs work

• Viruses multiply very quickly, so antiviral drugs will often have little effect by the time symptoms appear.

• Goal of antiviral drugs is to stop virus replication• DNA/RNA modification• Stop viruses to leave infected cells

Acyclovir and ganciclovir• Acyclovir is used as a cream or orally to fight herpes

viruses. Gancyclovir is used for genital herpes or when viruses has become resistant to acyclovir

• Shortens the time of the outbreak, but does not prevent recurrences

• It stops replication of viral DNA, and prevents virus from multiplying

Acyclovir

Gancyclovir

Amantadine and rimantidine

• Prevent new viruses from leaving the cell• Used to treat influenza. It inhibits the active

site of neuraminidase, an enzyme which helps the virus to stick to the cell wall

Amantadine Rimantidine

D.7.3

• Discuss the difficulties associated with solving the AIDS problem

HIV (Human Immunodeficiency Virus) • A retrovirus (contains RNA)• Is acquired by sharing bodily fluids with someone whos is

infected with HIV• Can lead to AIDS (Acquired Immune Deficiency Syndrome).• Attacks white blood cells called T helper cells (T4-cells)• T helper cells activate the immune system- the body is

rendered unable to fight infections• When invading a cell it starts making DNA from it’s RNA with

an enzyme called reverse transcriptase

• HIV

HIV, cont.• One of the problems with antiviral drugs for HIV is

the virus is constantly mutating• A drug called AZT (zidovudine) has been used to

inhibit the reverse transcriptase, and this does not affect normal cells

• AZT has been effective in prolonging the period until AIDS develops• AIDS medicins consist of a coctail of antivirals

Structurally similar?

AZT (zidovudine) Acyclovir

Solving the AIDS problem…

• What can we do today?

Solving the AIDS problem…

• Develop new antivirals• Develop vaccins• Prevent people from getting HIV, e.g. by using

condoms