Antibodies May Be Useful In Fighting HIV
NEW YORK, Jan 31 (Reuters Health) -- HIV-targeting antibodies may protect against the sexual transmission of the AIDS virus as well as prevent transmission of the virus from mother to infant, results of two new studies in monkeys suggest.
Antibodies are immune system proteins that target foreign invaders. Although many vaccines, such as the polio vaccine, are protective because they stimulate antibodies, some experts believed that antibodies alone were not enough to combat HIV.
However, in one study, a combination of three antibodies was given to pregnant monkeys and found to protect the monkeys against an HIV-like virus after they gave birth.
The antibody combination was also given to their offspring and protected them from the HIV-like virus when given orally. Newborn monkeys not treated with antibodies became infected with the virus, known as SHIV, which is used in AIDS research involving monkeys.
The finding suggests that these antibodies could protect infants from exposure to HIV during childbirth or through breast milk, conclude Dr. Ruth Ruprecht, of the Dana-Farber Cancer Institute in Boston, Massachusetts, and colleagues.
"If this approach works as successfully in humans, and if the antibodies can be produced inexpensively, it may offer a practical way of preventing mother-to-infant transmission of the AIDS virus even in the developing world," said Ruprecht in a statement issued by Dana-Farber.
In a second study, Dr. John Mascola with the Walter Reed Army Institute of Research in Rockville, Maryland, and colleagues show that antibodies that target three specific sites on the AIDS virus helped protect macaque monkeys against vaginal exposure to SHIV.
"This study demonstrates that antibodies can affect transmission and subsequent disease course after vaginal SHIV-challenge," Mascola and colleagues conclude.
Both reports are published in the February issue of the journal Nature Medicine.
The two studies indicate that antibodies may be more important than previously thought when it comes to transmission of HIV across mucous membranes, according to an editorial by Dr. Marjorie Robert-Guroff, of the National Cancer Institute in Bethesda, Maryland.
Stimulating the production of potent HIV-fighting antibodies "should remain an important component of broadly protective vaccines," she writes. And the findings suggest that injecting antibodies -- a process known as passive immunization -- may prevent transmission of HIV from mother to infant.
However, it is still not clear if the antibodies would protect humans from HIV, a much more dangerous virus than SHIV, Robert-Guroff notes. And the researchers did not conclusively demonstrate that the monkeys were indeed SHIV-free. The animals may have had undetectable levels of the virus in their blood, according to the editorial