AIDS may affect course of syphilis.

AIDS may affect course of syphilis

The incidence of syphilis and itsassociated mortality have declined dramatically since the discovery of penicillin. But the syphilis-causing spirochete, Treponema pallidum, is far from extinct; last year nearly 28,000 new cases of syphilis were reported in the United States, according to the Centers for Disease Control in Atlanta. And while most of these cases were apparently cured with single huge doses of penicillin, there is a growing debate about the ability of these shots to kill spirochetes that may be lurking undetected in the central nervous system. Indeed, there have been several reports in recent years of failed treatments for neurosyphilis--an advanced form of the disease in which the invading organisms infect the cerebrospinal fluid.

Now there is evidence that a patient'sown immune system is more important in fighting syphilis than was previously believed, and that the standard 2.4 million units of intramuscular penicillin may in fact be insufficient to halt the progress of the disease in some patients with weakened immune systems. The new findings, reported in the June 18 NEW ENGLAND JOURNAL OF MEDICINE, are particularly relevant to patients with AIDS.

Donna Felsenstein and her colleaguesat Massachusetts General Hospital in Boston looked at four recent cases of neurosyphilis in men with antibodies to HIV--the AIDS-causing human immunodeficiency virus. Two of the men developed the advanced form of syphilis despite having been treated with standard doses of penicillin. In the other two, syphilis was not discovered until it had reached the neurosyphilitic stage; the researchers subsequently determined that the disease had progressed to that stage much more rapidly than usual. In one case, within four months of his first exposure to syphilis, an AIDS-exposed man developed a form of neurosyphilis that normally takes five to 12 years to develop.

The precise mechanism by whichAIDS may accelerate the course of syphilis remains unclear, but AIDS is known to impair the body's two major defenses against treponemal infection-- spirochete-eating macrophages and antibody-producing B cells. In addition, the authors hypothesize, HIV-induced inflammation of the meninges surrounding the spine may facilitate treponemal penetration into the central nervous system, while antibiotics tend to remain in the blood. They suggest that for HIV-positive patients--and possibly for others--larger doses of penicillin, given over longer periods of time, may be necessary to get therapeutic levels of the antibiotic into the cerebrospinal fluid. Meanwhile, the debate goes on about the need for such augmented therapy in otherwise healthy patients, or in patients with non-AIDs immunodeficiencies caused by certain drugs or by chemotherapy.