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It is estimated that around 40% of mother-to-child transmission of HIV occurs through breast milk. But why do some babies contract HIV from their mothers while others don't?
There is a protein (called SLPI) in saliva which has antiviral, antibacterial and anti-inflammatory properties. This protein can combat HIV. A new study found that babies who have higher levels of SLPI in saliva are half as likely as other babies to be infected by HIV. The hope is that it may be possible to administer drugs that mimic the action of SLPI in order to lower a baby's risk of acquiring its mother's HIV infection.
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Barbara K. Hecht, Ph.D.
Frederick Hecht, M.D.
Medical Editors, MedicineNet.com
Substance in saliva protects babies from mom's HIV
Last Updated: 2002-10-29 11:51:31 -0400
By Alison McCook
NEW YORK (Reuters Health) - Babies with relatively high levels of a particular compound in their saliva appear to be less likely than others to acquire HIV from their infected mothers at one month of age, according to new study findings.
Dr. Carey Farquhar of the University of Washington in Seattle and colleagues found that babies with higher levels of a substance called secretory leukocyte protease inhibitor (SLPI) at one month of age were half as likely as those with lower levels of SLPI to have acquired HIV from their mothers.
Farquhar told Reuters Health that it may eventually be possible to administer drugs that mimic the action of SLPI to help prevent babies from acquiring their mothers' HIV infection.
"SLPI is a protein that could be developed into a drug," Farquhar noted.
HIV-1 is a major type of the virus that can cause AIDS. It is more readily transmitted through sex, infected blood and from mother to child, and may progress to AIDS more quickly than another common type, HIV-2.
Previous research has shown that SLPI in saliva has antiviral, antibacterial and anti-inflammatory properties. In fact, one study suggested that this healing compound may be one reason why dogs and other animals lick their wounds.
Researchers have also shown that SLPI, along with other compounds in saliva, can combat HIV-1, but only SLPI has demonstrated itself capable of going head to head with the virus when tested in the lab at concentrations normally found in saliva.
In the current study, reported in the October 15th issue of the Journal of Infectious Diseases, the investigators tested 602 samples of saliva from 188 infants born to mothers who were infected with HIV-1. The saliva was collected from the infants at birth and when they were 1, 3 and 6 months old.
Although Farquhar and colleagues did not discover an overall link between the risk of mother-to-child infections, they noted that babies with higher levels of SLPI at the age of 1 month were half as likely as other babies to have picked up HIV-1 from their mother's breast milk.
Most often, the concentration of SLPI in infants' saliva dropped from birth to 6 months, the report indicates.
Although HIV does not often infect people after an oral exposure--which researchers have suggested may also be due to SLPI--around 40% of all cases of mother-to-child transmission occur through breast milk, Farquhar told Reuters Health in an interview.
Breast milk contains HIV, the author noted. During delivery, a baby also becomes orally exposed to the mother's blood and genital secretions in the birth canal, while in the womb the baby drinks amniotic fluid, which also contains HIV, Farquhar noted.
The researcher added that it may not be useful to test babies' SLPI levels at birth to determine their susceptibility to infection. "We found that month 1 SLPI levels were associated with breast milk transmission and in countries where HIV-infected women breast-feed their babies, it would probably be better to test maternal HIV viral load to determine how much virus the mother has in her body," Farquhar said.
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