PEOPLE ELIGIBLE FOR THE SWISS STUDY:

Infection with HIV CD4 counts of at least 200 cells per cubic millimeter for at least 12 weeks CD4 counts of at least 14% of total lymphocytes for at least 12 weeks

OPPORTUNISTIC INFECTIONS THAT OFTEN OCCUR WITH HIV AND AIDS:

Pneumocystis carinii pneumonia Mycobacterium avium complex Toxoplasmosis Cryptococcosis Histoplasmosis Coccidioidomycosis Cytomegalovirus

PNEUMOCYSTIS CARINII PNEUMONIA BEFORE HAART:

Affected 60-80% of adult HIV patients 70% of these suffered second episode of PCP within 12 months

April 28, 1999
Web posted at: 5:12 p.m. EDT (2112 GMT)

In this story: Opportunistic infections and PCP Benefits of discontinuing preventative therapy Study of Swiss HIV patients Another study confirms the observations Still questions about secondary prophylaxis RELATED SITES

By Hacsi Horvath

(WebMD) -- Two studies, conducted independently of each other, indicate that it may be possible for many HIV-infected patients to discontinue lifelong preventative therapy against a dangerous respiratory infection.

One study appears in the April 29 issue of The New England Journal of Medicine. The other appeared in The Lancet's April 17 edition.

Opportunistic infections are a leading cause of death among people with HIV and AIDS. These infections take advantage of a patient's deficient immune system to further weaken and even kill the person. Pneumocystis carinii pneumonia (PCP) is a particularly deadly one. Before medications were developed that could prevent it, PCP was the most common infectious cause of death for people with AIDS.

A key indicator of a functioning immune system is the presence of high levels of CD4-positive lymphocytes in the bloodstream. Doctors have typically prescribed an anti-PCP medication called trimethoprim/sulfamethoxazole (Septra or Bactrim), or other drugs, for HIV patients whose CD4 levels fall below 200 cells per cubic millimeter. PCP and other opportunistic infections often occur in those patients whose CD4 levels fall below this threshold. The preventative regimen has been assumed to be a lifelong course of therapy.

The advent in 1996 of highly active antiretroviral therapy (HAART), with its capacity to restore the immune system and to reduce HIV levels in the blood, has led researchers to question the need for these lifelong prophylactic (preventative) measures. Although the anti-PCP therapy is inexpensive and simple (21 cents, and one tablet per day), many people are allergic to these medications. There is a psychological benefit in simplifying the regimen of medications and affirming the immune system's improvement. There is also less risk that antibiotic-resistant strains of bacteria will develop through misuse or unnecessary use of the medication.

In the New England Journal article, researchers associated with the Swiss HIV Cohort Study found that of 262 patients who discontinued prophylactic antibiotic therapy against PCP, none had come down with the disease after more than a year, though two died from other causes. Nor were there any cases of toxoplasmosis, another common infection affecting people with HIV, and also preventable with trimethoprim/sulfamethoxazole. These patients all had received HAART, which had resulted in higher CD4 counts.

A second study, published in The Lancet, seems to confirm the observations of the Swiss study. While the Swiss study was prospective, meaning that the participants were chosen on the basis of certain criteria, and directed to discontinue preventative therapy against PCP, researchers with the EuroSIDA Study Group worked retrospectively, analyzing the outcomes of 378 people undergoing HAART who had already stopped taking the antibiotic medication. As was the case with the Swiss study, none of the EuroSIDA group developed PCP or toxoplasmosis.

Both studies concluded that lifelong primary preventative therapy against PCP may no longer be necessary. It's not clear, however, whether secondary prophylaxis against re-infection may be discontinued, in the case of patients who have already survived one episode of PCP, though 59 members (16 percent) of the EuroSIDA study fell into this category.

These studies show that the lymphocytes of the restored immune system may be effective in preventing PCP and possibly other opportunistic infections. It is still unknown whether the new antiretroviral therapies will be sufficient of themselves to make secondary PCP prophylaxis unnecessary, but further studies should make this clear.