AIDS TREATMENT UPDATE, Issue 42, June 1996
Edward King

The longest study of a protease inhibitor to date has found that for people who had previously taken AZT, those treated with the combination of ddC plus saquinavir were significantly less likely to die or develop an AIDS-defining illness than those treated with either drug alone during 18 months follow-up.

The study enrolled people with CD4 counts between 50 and 350. Participants had taken AZT for an average of 16 months before joining the trial and switching to the trial drugs. There was no difference between saquinavir and ddC when taken alone, either in terms of disease progression or survival. The result provides more evidence that combinations are better than monotherapy.

This is only the second completed study which has assessed the clinical benefits of protease inhibitors. Earlier this year, in a much shorter study in people with more advanced disease, adding ritonavir to any existing anti-HIV therapy was also shown to delay disease progression and prolong life.

Saquinavir is currently available in the UK through an open label safety study for people who are failing to do well on currently approved drugs. In practice, this open label study does allow doctors to add saquinavir to any combination of drugs for people with CD4 counts below 350.

* Immune activation

American researchers have confirmed existing theories by showing that HIV replication is boosted when the immune system is activated.

The researchers gave the tetanus booster immunisation to 13 symptom-free HIV-positive people to stimulate their immune system. Blood samples were taken for tests on the day of the injection and 3, 7, 14, 21, 28 and 42 days later.

When the immune system is activated, HIV-infected immune cells are also stimulated to produce new HIV particles. The researchers found that all the HIV-positive people experienced two-fold to 36-fold increases in viral load following the injections. HIV levels peaked after 13 days, and had returned to their starting baseline value after six weeks.

Two people also had HIV levels in their lymph nodes measured; in both cases viral load rose after the injection.

Apart from immunisations, factors that activate the immune system include infections, both HIV-related (opportunistic infections) and non-HIV-related (such as sexually transmitted diseases). The study thus lends weight to the belief that HIV-positive partners may be well-advised to practise safer sex despite both already having HIV.

HIV-positive people who are at risk from infections (such as hepatitis B among gay men and drug users, or tropical diseases when travelling) are generally advised to have standard immunisations, although certain vaccines that contain live micro-organisms should be avoided (see AIDS Treatment Update issues 19 and 38). The benefit of being protected against infections is likely to outweigh any risk from short-term increases in HIV viral load.

* Improved survival

A review of HIV-positive gay men enrolled in the US Multicenter AIDS Cohort Study has concluded that survival rates have improved significantly in the period from 1989-1993 compared with 1985-1988. The increases are attributed to anti-HIV drugs and preventive therapies against opportunistic infections.

For each of the two time periods, the researchers divided participants into three groups on the basis of their CD4 count, and examined how many men survived for at least 2.5 years. The results, summarised in the table below, showed that among people with CD4 counts below 350 there was a significant improvement in survival in the more recent period, when better treatments were available.

Although the results of such retrospective studies should always be interpreted with caution, the researchers argue that in fact the figures are likely to underestimate the beneficial effects of treatments on survival, since not everyone in the latter time period took the medications that were available.

Proportion surviving at least 2.5 years CD4 count range 1985-1988 1989-1993

0-100 22% 54% 101-200 53% 71% 201-350 83% 91%

* Briefly...

This month we received a lengthy response to the article in issue 40 that dissected 'AIDS dissident' claims that HIV does not exist. However, the article's authors - the Australian team who have previously claimed that HIV tests routinely give false results - abruptly withdrew the paper and insisted that we did not publish it.

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