UCLA researchers 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, who received no treatment, is now 5 years old, healthy 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 suspected was possible but had never proved--that the human immune 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 previously reported, 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 disappeared from his body.
Bryson cautioned mothers of HIV-positive infants not to build up their hopes solely on the basis of her report. "I don't want this to be misconstrued by mothers," she said. "This is a relatively rare thing."
But the discovery is important, Bryson said, because, "if it happens once, particularly in an infant, it may happen more often."
The results, she said, may explain why 70% of infants born to HIV-positive mothers do not develop the disease. It may also 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.
She said, however, that the vast majority of infants who are born infected remain infected. "Every mother or HIV-positive person should not go running to their doctor thinking that perhaps their infection is gone."
Bryson also said that the team has tentatively identified a second child, a girl, that they believe has recovered from an HIV infection, and they are doing the extensive molecular testing necessary to confirm this possibility. But, she noted, these are only two cases out of more than 170 mother-infant pairs that they have examined in an ongoing study of babies born to HIV-infected mothers. The researchers are keeping the identity of the two children confidential.
In an accompanying editorial in the same issue of the journal, Drs. Kenneth McIntosh and Sandra K. Burchett of Childrens Hospital in Boston noted that several similar reports had previously been published, but said 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," Bryson said.
To show that such errors did not occur, 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," 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," 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, Bryson said, that the immune system of the child studied has some unique characteristic that allowed it to overcome the virus, and the team is studying him carefully to look for evidence that this occurred. It is also possible, she said, that the virus was defective and could not continue replicating in the child.
But more likely, Fauci said, is the possibility that antibodies from the mother partially suppressed the infection, allowing the infant's immune system to complete the job of clearing it.
Support for this possibility comes from previous studies in which HIV-positive mothers aborted their fetuses. Examinations of the fetuses showed that a higher percentage were infected by HIV than are infected at birth. Those results suggest that many infants, perhaps even most, are able to clear the infection before or shortly after birth, before any signs of infection could be detected.
In the past year, physicians have begun routinely prescribing the anti-HIV drug AZT to HIV-positive women who are pregnant. Studies show that the drug reduces transmission of the virus to the infants by two-thirds.