AIDS: Science at a Crossroads

6. DRUG TREATMENTS: WHAT'S IN THE CUPBOARD?
There is no cure for AIDS, but a number of treatments have been developed to help deal with the
various opportunistic infections which people with HIV and AIDS may contract, and to try and delay
the onset of AIDS.
Orthodox therapies
The existing treatments for HIV infection and the symptoms of AIDS have benefited patients in the
rich world but have scarcely touched the developing countries. Mainly because of good treatments for
opportunistic infections such as cytomegalovirus or Pneumocystis carinii, people in the North can now
expect to live for about two years after AIDS has been diagnosed - twice as long as in the early 1980s.
In the South, the available data suggest the survival is much shorter. Doctors in the South are frustrated
by the lack of basic antibiotics and antifungals they need to treat these opportunistic infections. But
with total annual health budgets per capita of as little as US$ 13.5 on average in sub-Saharan Africa,
even these cheap drugs are out of reach. The antiviral drugs that attack HIV itself, such as zidovudine
(AZT) are out of the question: one day's supply for someone with AIDS costs about US$ 15.
So far, approaches to the direct treatment of HIV have focused on either attacking the virus, by
designing antiviral drugs or boosting the immune system against it. In addition, there is a wide range
of drugs to treat opportunistic infections such as tuberculosis.
The earliest type of antivirals are known as nucleoside analogues: they include zidovudine (AZT), ddl,
ddC, 3TC, stavudine and FLT. All these drugs work in the same way: they mimic the protein building
blocks (nucleosides) in a cell and stop the virus from assembling its genetic material. When HIV
replicates, it has to turn its genetic material from RNA into DNA, which it does with the help of its
enzyme reverse transcriptase. The enzyme builds up the chain of building blocks in DNA by
assembling nucleosides from the cell. The "false" nucleosides generated by the drug join into the chain
and stop further real nucleosides from being added, like a broken bead in a necklace.
Trials of AZT show that it can benefit people with AIDS for a limited period by slowing down the
process of disease. However, its benefits are short-lived: people who start taking it when they havye HIV
infection but no symptoms will tend to develop AIDS as soon as they would have done if they had not
taken the drug. Unfortunately, the drug can also have significant side effects including anaemia and
muscle wasting. Nevertheless, a study from the US National Institute of Allergy and Infectious Diseases
showed in early 1994 that the drug could cut by two-thirds the number of infections passed from mothers
to their unborn children. Encouraging though this is, most pregnant women with HIV in the world have
no hope of obtaining AZT And the long-term effects of the drug, if any, on a foetus are unknown.
Other antivirals include protease inhbitors, which work by inhibiting protease, an essential viral
enzyme enabling HIV to reassemble new copies of itself, by chopping up large proteins into smaller
ones. Saquinavir, one of several protease inhibitors on trial, has produced some encouraging results on
its own and in combination wihth other antivirals (10).
The main problem with antivirals of all types is that HIV rapidly develops resistance to them.
Researchers hope that combinations of different antivirals will help to lengthen healthy life and reduce
the opportunities for drug-resistant strains to emerge. However, there are few data as yet to either
support or destroy their hopes.
Rather than attack the virus directly, some treatments are designed to reinforce defences against it by
boosting the immune system. They include so-called therapeutic vaccines, in which an already infected
person receives an injection of genetically engineered envelope protein. The aim of a therapeutic
vaccine is to trigger a new immune response in the infected person, in the hope that it might strengthen

the natural immune response against the virus. Despite bullish early claims, the effects of these
therapeutic vaccines is unclear.

13 - Panos Briefing: AIDS: SCIENCE AT A CROSSROADS