The heartening news that a second American baby has possibly been cured of the virus that causes AIDS is drawing attention to the work of a team of Canadian researchers who may have found as many as five similar cases in this country.
The investigators have received nearly $2-million in funding to delve into whether treating HIV-infected newborns with an aggressive trio of drugs immediately after birth can knock out the virus, as apparently happened in a now-famous case in Mississippi.
However, the Canadian scientists, like all pediatric HIV-AIDS researchers looking into this question, face an ethical quandary: They cannot say for sure that the potential cure is successful unless they take HIV-positive children off the anti-retroviral medications that keep the virus at bay.
"It is possible that the only way we will know is to stop the medicine and that is not a simple decision," said Ari Bitnun, a physician in the department of infectious diseases at the Hospital for Sick Children in Toronto and a member of the research team. "If they aren't cured and you stop their medicine, the viral load will go up and you can start the medicines again, but there may be some downsides to that."
This dilemma helps explain why the Mississippi baby's apparent recovery from HIV infection was discovered by fluke.
The stunning story, revealed at the Conference on Retroviruses and Opportunistic Infections in Atlanta last March, involved a mother-to-be who was unaware she was HIV-positive and therefore did not take drugs to prevent transmission of the virus to her infant.
Doctors started the baby on high doses of three drugs – AZT, 3CT and nevirapine – about 30 hours after being born, a protocol more aggressive than the standard treatment given to prevent mother-to-child transmission in these cases.
The child was given anti-retroviral medication until the age of 18 months, when the mother stopped coming to medical appointments and halted the medication. Five months later, doctors were shocked to discover the child was virus-free, despite the break in treatment.
When the Canadian researchers heard about the Mississippi case, a light bulb went on, Dr. Bitnun said.
At least two other Canadian hospitals, the Children's Hospital of Eastern Ontario in Ottawa and Sainte-Justine Hospital in Montreal, had been administering the same combination of antiretroviral medications at higher doses to HIV-infected babies very soon after birth for years.
Doctors at all three hospitals combed through their records and found five children who had undergone the early treatment and whose viral loads were suppressed to the point they could not be detected in blood tests, information the scientists used to apply for a grant last summer.
The team is running ultra-sensitive tests on the children, who now range in ages from three to the early school years, in a bid to determine if any traces of the virus are dormant and hidden in their bodies.
"The one big difference is that our children remain on treatment, whereas that [Mississippi] child was taken by mistake off treatment," Dr. Bitnun said.
The team is planning to present its initial findings at the Canadian Association for HIV Research conference in St. John's in May.
They are also embarking on a cross-country study, enrolling as many HIV-infected children as possible to compare those treated immediately after birth with those diagnosed and treated later.
A second American baby, whose case was described this week at the Conference on Retroviruses and Opportunistic Infections in Boston, is a nine-month-old who is apparently virus-free, but remains on medication.
If researchers are touting that child's case as evidence of a possible cure, the cases in this country could fit the bill too, although the Canadian researchers caution it is too early to say.
"The word 'cure' is premature," said Fatima Kakkar, a physician in the division of infectious diseases at Sainte-Justine Hospital in Montreal and another member of the research group. "But by studying these kids, I think we're going to find out a lot of really useful information as to how, with some people in some situations, we can lead to really good viral control that maybe one day won't need medication."