AN IMPACT OF LACTOFERRIN, SERUM ALBUMIN AND SECRETORY IMMUNOGLOBULIN A IN ACTIMICROBIAL ACTIVITY OF BREAST MILK WHEY

The contribution of the antimicrobial activity of sIgA, lactoferrin, a-lactalbumin, serum albumin, and lysozyme to the total antimicrobial activity of whey was evaluated. 66 breast milk samples from healthy women aged from 23 to 45 years collected at different periods of lactation were studied. It was found that along with proceeding the lactation period, not only the total antimicrobial activity (r = -0.944) decreased, but also the activity of the low molecular weight fraction containing the sum of antimicrobial peptides (r = -0.950). The median lactoferrin level varied from 3.46 mg/ml in colostrum down to 0.94 mg/ml one year after the onset of lactation that correlated with whey activity (r = 0.616). The concentration of sIgA was peaked in the whey of colostrum (5.01 mg/ml) and significantly reduced in mature milk, remaining approximately at the same level in subsequent periods of lactation (1.0 mg/ml). Serum albumin concentration significantly decreased while proceeding through lactation period (from 5.52 to 4.68 mg/ml) and correlated with whey activity (r = 0.589). Evaluating effects of the purified a-lactalbumin on C. albicans cells within the range of 5-20 mg/ml by spectrophotometry and microscopy showed the absence of fungicidal activity. At the same time, purified lactoferrin, IgA, lysozyme, and serum albumin demonstrated a direct fungicidal effect. The activity of the IgA preparation at a concentration relevant to the sIgA content in the whey of the first day colostrum was 50.0%, and in the whey after 12 months - 31.0%; lactoferrin - 26.7% and 3.4%; serum albumin - 15.0% and 17.7%; lysozyme - 0.1% and 1.8%. Thus, the sum of the activities of these polypeptides at concentrations typical for the first-day colostrum was 91.7%, which is comparable to the total activity of this whey - 82.4%. The sum of the activities of these polypeptides, typical for 12 months of lactation, was 53.9%, and the total whey activity relevant to this period was 64.5%. Therefore, IgA and lactoferrin contribute the most significant antimicrobial activity in the whey of colostrum, whereas after 12 month-breastfeeding IgA and serum albumin become most significant.