Researchers at the University of California-Los Angeles say they have documented for the first time a case in which an infant infected with the AIDS virus at birth cleared the virus from his body by his first birthday.
The child is now a healthy 5 1/2 -year-old kindergarten pupil who is developing normally and shows no evidence of ever having been infected by HIV.
The report, published today in the New England Journal of Medicine, confirms what researchers had suspected was possible but had never been proved -- that the human immune rTC system can fend off the AIDS virus. By studying the phenomenon, they hope to gain insight for developing an AIDS vaccine.
"This tells us something very important," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, "that there are situations where you can get infected and clear the virus. There must be some mechanism available in the body capable of doing that. If we look carefully enough, we may be able to [find it]."
Several similar cases have been reported in the medical literature, but all have been dismissed as the result of laboratory errors.
Dr. Yvonne J. Bryson and her UCLA colleagues report that they have used sophisticated molecular biology techniques to show without a doubt that the child was infected and that the virus has since disappeared from his body.
The discovery is important, Dr. Bryson said, because "if it happens once, particularly in an infant, it may happen more often."
The results, she said, may explain why 70 percent of infants born to HIV-positive mothers do not themselves develop the disease. It also may shed new light on the mechanisms by which some spouses of HIV-positive individuals and some groups of African prostitutes are able to avoid infection.
But Dr. Bryson cautioned mothers of HIV-positive infants not to build up their hopes solely on her report.
"I don't want this to be misconstrued by mothers," she said. "This is a relatively rare thing."
Dr. Bryson said the team has tentatively identified a second child, a girl, that they believe has recovered from an HIV infection, and they are now doing extensive molecular testing to confirm the possibility. But, she noted, these are only two cases out of more than 170 mother/infant pairs that they have examined in a continuing study of babies born to HIV-infected mothers. The researchers are keeping the identities of the two children confidential.
Dr. Neal Halsey, director of the disease-control division at the Johns Hopkins School of Medicine in Baltimore, said that clearing a virus from the human body is quite common, but not for HIV.
"There are other viral infections, such as measles or mumps, that occur and are cleared from the body. But we didn't think it was possible with HIV," he said.
In an accompanying editorial in the journal, Drs. Kenneth McIntosh and Sandra K. Burchett of Children's Hospital in Boston noted that several similar reports had been published, but that those researchers could not confirm that the children had been infected in the first place. That lack of documentation left open the possibility that the initial positive HIV test could have resulted from contamination of the infant's blood sample in the laboratory or an inadvertent mixing of specimens.
"I was skeptical myself," Dr. Bryson said.
The child was born at the Los Angeles Medical Center. His mother was HIV-positive. He tested positive for HIV 19 days after birth, and again 51 days after birth. But after one year, the boy tested negative.
To show that research errors did not occur, Dr. Bryson and her colleagues, including Dr. Irvin S. Y. Chen, director of the UCLA AIDS Institute, ruled out lab contamination by showing that the genetic composition of the virus isolated from the infant's specimens was virtually identical to that of the virus isolated from his mother.
They also did DNA fingerprinting of the blood cells from which the virus was isolated and showed that those fingerprints were identical to fingerprints from a new sample of the child's blood, thereby eliminating the possibility of mixed-up samples.
"In light of the new case," Drs. McIntosh and Burchett wrote, "it seems that perhaps they [the previous cases] were not errors, or at least not all of them."
The result was "amazing," Dr. Bryson said, because the immune system of infants is generally considered much weaker than that of an adult, and infants are usually more susceptible to infections than adults.
It is possible, Dr. Bryson noted, that the immune system of the child studied has some unique characteristic that allowed it to overcome the virus. The team now is studying him to look for evidence that this might have occurred. It also is possible, she said, that the virus itself was defective and simply could not continue replicating in the child.
But more likely, Dr. Fauci said, is the possibility that antibodies from the mother partially suppressed the infection, allowing the infant's own immune system to complete the job of clearing it.