Acyclovir is an antiviral drug used to treat herpes infections. Outline two ways in which antiviral drugs work.

Discuss two difficulties associated with the development of drugs for the effective treatment of AIDS.

alter cell’s genetic material;

(changes cell membrane so that it) inhibits virus entry/binding to cell;

prevents virus from leaving cell (after reproduction);

becomes part of DNA of virus / alters virus / blocks enzyme (polymerase) which builds DNA;

prevents virus from using cell to multiply/reproduce/replicate;

Do not accept “blocks enzyme activity within host cell / OWTTE”.

HIV mutates (rapidly) / OWTTE;

Do not accept “AIDS mutates” without mention of the virus.

HIV destroys (T-)helper cells/white blood cells/lymphocytes / HIV attacks immune system;

Penalize the use of “AIDS” for “HIV” once only.

Do not accept general answers based on “cost of drugs” or “cost of development”.

More than half of the candidates showed a good understanding of how antiviral drugs work.

Most candidates talked about the rapid mutation of viruses, however, only a few talked about viruses destroying T-helper cells as a difficulty associated with the development of drugs for the treatment of AIDS. A number of candidates discussed the high cost of such drugs that was irrelevant to the question. Some candidates confused AIDS with HIV.