Malaria Antigen Shed in Breast Milk of Mothers in Region With Endemic Malaria

By Will Boggs MD

January 08, 2020

NEW YORK (Reuters Health) - Malaria antigen is shed in the breast milk of mothers with asymptomatic malaria who live in northeastern Uganda, where malaria is endemic, researchers report.

"For the very first time, we show that 15% of mothers harbor proteins from malaria parasite in breast milk," Dr. Valerie Verhasselt of The University of Western Australia School of Molecular Sciences, in Perth, told Reuters Health by email. "We propose these proteins, in the presence of breast milk factors that are adapted to the infant, may activate the immune system of the child and render the child protected from malaria infection. This would be a way to naturally vaccinate the infant."

Children under age 5 account for two-thirds of all malaria deaths in Africa. Previous studies have yielded conflicting evidence on malaria prevention by breastfeeding.

Dr. Verhasselt and colleagues investigated whether two malaria antigens - Plasmodium falciparum histidine-rich protein 2 (pHRP-2) and lactate dehydrogenase (pLDH) - are detectable in the breast milk in their study of 123 lactating mothers who visited the malaria clinic in northeastern Uganda during the low malaria-transmission season and 201 lactating mothers who visited during the high malaria-transmission season.

None of the mothers had clinical malaria, but 11.4% and 36.8%, respectively, harbored asymptomatic malaria during the low- and high-transmission seasons.

Among the 88 breast milk samples from mothers with asymptomatic malaria, seven (7.9%) had detectable pHRP-2 and 10 (11.3%) had detectable pLDH.

Overall, 14 samples (15.9%) were positive for at least one of these antigens, and three (3.4%) were positive for both, the researchers report in JAMA Pediatrics.

In contrast, none of the 44 milk samples from mothers without malaria showed detectable pHRP-2 or pLDH antigens.

Preliminary data suggested that the percentage of breast milk samples positive for pHRP-2 and the concentration of pHRP-2 in breast milk correlated with the density of P. falciparum parasites in the mothers' blood.

"Now that we have demonstrated that proteins from malaria parasite can be found in maternal milk, we need to conduct a study which follows the children and assesses whether the ones that are exposed to malaria protein through breast milk are more resistant to malaria than the ones that are unexposed," Dr. Verhasselt said. "We also need to find out what controls the transfer of malaria protein into breast milk."

"We could then propose to vaccinate lactating mothers to increase levels of malaria antigen in breast milk and thereby ensure immune activation and long-term protection of their child," she said.

The study had no commercial funding, and the researchers report no conflicts of interest.

SOURCE: JAMA Pediatrics, online January 6, 2020.