It has been reported that breast-feeding is responsible for approximately 40% of the HIV transmissions from HIV-positive mothers to children. Human breast milk, however, is known to contain numerous biologically active components which protect breast-fed infants against bacteria, viruses, and toxins. The purpose of this study was to purify and characterize breast milk
mucin and to determine its anti-HIV-1 activity in an HIV inhibition assay.
Sepharose CL-4B column chromatography and
caesium chloride isopycnic density gradient purification were used to isolate and purify the
mucin. Following Western blotting and
amino acid analysis, an HIV-1 inhibition assay was carried out to determine the anti-HIV-1 activity of crude breast milk and purified milk
mucin (MUC1) by incubating them with HIV-1 prior to
infection of the human T lymphoblastoid cell line (CEM SS cells). SDS-PAGE analysis of the
mucin, together with its
amino acid composition and Western blotting, suggested that this purified
mucin from human breast milk was MUC1. The HIV inhibition assay revealed that while the purified milk
mucin (MUC1) inhibited the HIV-1 activity by approximately 97%, there was no inhibition of the HIV-1 activity by crude breast milk. Although the reason for this is not clear, it is likely that because the MUC1 in crude milk is enclosed by fat globules, there may not be any physical contact between the
mucin and the virus in the crude breast milk. Thus, there is a need to free the
mucin from the fat globules for it to be effective against the virus.