A study by researchers at the Berkeley and Davis campuses of the University of California has found that flash-heating breast milk infected with HIV successfully inactivates the free-floating virus.
The researchers hope that this technique - heating a glass jar of expressed breast milk in a pan of water over a flame or single burner - will provide hope that mothers with HIV in developing nations will soon be able to more safely feed their babies as it can be easily applied in the homes of mothers in resource-poor communities.
"HIV can be transmitted to the baby via breastfeeding. But for infants in developing countries where infant mortality is already so high from diarrhea and other illnesses, they can't afford to lose the antibodies, other anti-infective agents and the optimal nutrition found in breast milk. This study shows that an easy-to-implement heating method can kill the HIV in breast milk," said Kiersten Israel-Ballard, a doctoral candidate at UC Berkeley's School of Public Health and lead author of the study.
Studies by researchers led by Kiersten Israel-Ballard have shown that flash-heating breast milk can kill bacteria while retaining most of the milk's nutritional and antimicrobial properties, as well as a majority of its important antibodies.
Researchers undertook the study after HIV-positive women in Zimbabwe asked how they could make their milk safe for their babies. While the World Health Organization (WHO) recommends heat treating HIV-infected breast milk, there has been little research into a simple method that a mother in a developing country could use.
Studies by this research team have shown that flash-heating breast milk can kill bacteria while retaining most of the milk's nutritional and antimicrobial properties, as well as a majority of its important antibodies.
"We wanted to be sure that there was scientific evidence that flash-heated milk was truly free of HIV, nutritious and immunologically beneficial. This study was done in response to the concerns of the mothers in Zimbabwe, and in addition provides evidence that field studies are warranted," said Barbara Abrams, UC Berkeley professor of epidemiology and maternal and child health, and senior author on the study.
Banks that collect, store and dispense human milk already pasteurize milk, but the method they commonly use requires thermometers and timers that may be hard to obtain in resource-poor communities.
Flash-heating is a type of pasteurization that brings the milk to a higher temperature for a shorter period of time, a method known to better protect the anti-infective and nutritional properties of breast milk than the one typically used in human milk banks.
Moreover, the low-tech materials used for this study are readily available in local communities in the developing world, and the heating method can be easily incorporated into a mother's normal daily routine.
Studies indicate that when babies are breastfed exclusively, there is a 3 to 4 percent risk of HIV transmission. However, when babies are given formula or other foods in addition to breast milk, there is a significant three- to four-fold increase in the risk of HIV transmission, possibly because allergens and contaminants in solid foods and formula can compromise the epithelial lining of a baby's digestive tract, making it easier for viruses to pass through.
For this reason, WHO guidelines have recommended that after six months of exclusively breastfeeding, HIV-positive mothers wean their babies as soon as other foods are available. Even then, while weaning may decrease the risk of HIV transmission, studies have shown that it increases the risk of malnutrition, diarrhea and other diseases that can lead to infant mortality.
As part of the research, 98 samples of breast milk were collected from 84 HIV-positive women in Durban, South Africa. Of these, only 30 had detectable levels of HIV before heating. Not all breast milk from HIV-positive mothers contains HIV naturally. Milk had been hand expressed into clean, locally purchased glass food jars provided by the researchers.
For each sample of HIV-infected milk, researchers set aside 50 milliliters in the original collection jars and used the remainder as unheated controls. The uncovered jars were placed in a 1-quart pan filled with 450 milliliters of water. The water and milk were heated together over a single-burner butane stove. Once the water reached a rolling boil, the breast milk was immediately removed and allowed to cool.
The researchers checked the temperature of the milk at 15-second intervals and determined that the flash-heated milk reached a peak temperature of 163 degrees Fahrenheit (72.9 degrees Celsius), and typically stayed hotter than 132 degrees Fahrenheit (56 degrees Celsius) for more than six minutes.
Viral analysis of the flash-heated and unheated breast milk found that cell-free HIV had been inactivated in all of the heated samples.
The researchers note that they used a reverse transcriptase (RT) assay to test for an enzyme produced by viable HIV since traditional tests for HIV do not distinguish between dead and live viruses. The RT test, however, cannot detect HIV within cells, but preliminary data suggest that flash-heat inactivates cell-associated HIV as well.
"We hope this technique will not only provide HIV-free breast milk that is safe to consume, but that the milk also retains the antibodies and nutrition that will help keep their infants healthy," said Israel-Ballard.
The findings will appear in the July 1 print issue of the Journal of Acquired Immune Deficiency Syndromes.