Important note: Information in this article was accurate in 1997. The state of the art may have changed since the publication date.
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The San Francisco Examiner - Thursday, Jan. 23, 1997
Lisa M. Krieger, Examiner Medical Writer
The experiment, outlined by Dr. David Ho of the Aaron Diamond Research Center in New York at the opening of the Fourth Annual Conference on Retroviruses and Opportunistic Infections, will define whether HIV disease is a lifelong condition - or can be defeated.
For 18 months Ho has been treating 20 patients with a potent new combination of anti-viral drugs. Based on his mathematical analysis of the patients' responses, Ho predicts that 2 to 2-1/4 years of treatment are needed to destroy HIV - if it can be eradicated.
This concrete estimate would have been unthinkable before this year. It shows how far medical science has progressed in treating a disease that has eluded a cure since its discovery in 1981. Although not everyone responds to treatment, the experiment suggests that control of the epidemic, which has killed more than 340,000 people in the United States, may be within reach.
Until recently, treatment produced only a slight delay in the relentless progression from HIV infection to AIDS. But scientists discovered that combining several anti-viral treatments could stop the advance and dramatically suppress the virus in the bodies of many patients.
"The antiviral effect we have seen was not predicted by anybody," said Ho, who was named Time magazine's "Man of the Year" for his research. "But we have a long way to go."
HIV has not yet been eliminated in any patient, Ho stressed. But if a cure can be achieved, he said, the best approach would be to hit the virus hard and quickly - as with treatments for tuberculosis or acute leukemia.
If eradication proves impossible, he predicted, HIV will be managed with long-term maintenance medication, much as hypertension or diabetes is treated.
Ho has not asked patients in his study to quit treatment. So far, the virus in their blood has been suppressed for only 18 months. Ho plans 2 to 2-1/4 years of total treatment, plus clearance of virus from tissue, before undertaking his experiment.
Some San Francisco doctors who have asked patients under their care to discontinue anti-viral therapy after 1-1/4 years say they observed a rebound of infection.
In a related development, Ho reported the virus could be driven to undetectable levels in semen. This raises the possibility that transmission of HIV someday could be blocked.
However, he urged that safe sex practices continue.
"Undetectable does not mean absent ..." he said. "We need to study the impact (of treatment) on transmission."
Tests of immune systems in treated patients support Ho's conviction that the virus can be shut off.
The body responds in two major ways against HIV infection - with immune-system cells called antibodies, which attack the virus, and cells called cytotoxic lymphocytes, which attack infected immune cells.
After 18 months of treatment, these warriors against infection had virtually disappeared from Ho's patients.
"This suggests that the body isn't seeing a lot of HIV," he said.
His analysis of the patients found that 99 percent of the virus was suppressed to undetectable levels within several weeks of treatment with triple-drug therapy. Virus that is free-floating or within immune system cells seems to be promptly eliminated, Ho said.
But the remaining 1 percent - "the embers" of virus, Ho calls them - are a far bigger challenge. This virus, trapped within cells called macrophages, take up to 2.3 years to burn out, and could re-ignite the infection if treatment is stopped too soon.
So treatment must persist long enough to extinguish every particle of virus. This is accomplished via two routes: shutting off new viral replication and letting infected immune cells die.
Even as he delivered his predictions, Ho warned against excessive optimism. He said the virus might hide in undiscovered, well-protected places. There is the more remote possibility that fragments of the virus' DNA could recombine and generate new virus.
"We should avoid unwanted "triumphantism,"" he said. "But undue pessimism is equally unhealthy. It is not white, not black. We must paint it in the proper shade of gray."
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