Thursday, March 7, 2013

HIV "cure" might fill a gap

It's strange when the discovery of a "cure" points to another, some say even greater, achievement. For instance, the news this week was that researchers used aggressive drug treatment to "cure" a Mississippi baby born with the AIDS virus. We had a quick talk about the story with Michael Saag, M.D. co-director of the UAB Center for AIDS Research.

The baby's mother, living in a poor, rural community, had been infected and passed the virus to her fetus, but had received no prenatal care before she went into labor. So the baby was born before anyone knew it was infected. As in many stories of discovery, what happened next included some accidents.

The hospital was out of the usual treatment, so the baby was referred to doctors that decided to use a high-dose, three-drug combination for older children instead of the usual low-dose treatment recommended for babies. They also administered the drugs quickly after birth.

After 18 months on the treatment, the baby and its family dropped out of the system, and the child went on an unplanned "treatment holiday." When the family reappeared, doctors realized that the child had been off the medications for a year but had no signs of infection.

As amazing as this case is, what jumps out at me is its rarity. In nearly all cases, HIV-infected mothers in the United States are tested and treated months before giving birth; nearly all of their babies are born with undetectable viral levels (functionally cured). In that light, this week's cure, should it be confirmed, would apply to the very few HIV positive babies in the U.S. that are not treated before birth. Somewhat lost in the excitement over a cure for the few exceptions is the massive achievement by the U.S. system of virtually eliminating mother-to-child HIV transmission.

"This case goes to show that once drugs are invented, as complex as that is, the field then faces the even more daunting task off getting them to everyone who needs them, and using them in the best way for each group of patients," said Saag. "That said, the new technique may fill a vital gap if it reduces viral load to almost zero in babies born to mothers that have slipped through HIV surveillance systems."

This week's discovery could have the most meaning outside of the United States, said Saag. The poorest African countries, for instance, have high infection rates, and only about 60 percent of pregnant women get treatment that can keep them from passing the virus to their babies.

Moving forward, Saag said, it is important for the field to understand why the baby was cured. Early on in exposure to the HIV, the infection either takes or it does not. If it takes, the virus goes into a latent state where it hides and quietly multiplies indefinitely, weakening the immune system while it grows strong. Once a pool of latent virus is present, it is harder to kill enough virus with antiviral drugs to get a cure. In the Mississippi case, Saag said it looks like strong, quick treatment after the initial infection may have prevented the establishment of a latent pool of infected cells.

As explained in this article in USA Today, it will take some time before the global impact of this week's cure is understood. In the best case scenario, babies not treated during pregnancy may receive more aggressive treatment at birth to spare them the burden of taking so many medications for a lifetime.

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