Catharina Svanborg

Molecular characterization of alpha-lactalbumin folding variants that induce apoptosis in tumor cells

This study characterized a protein complex in human milk that induces apoptosis in tumor cells but spares healthy cells. The active fraction was purified from casein by anion exchange chromatography. Unlike other casein components the active fraction was retained by the ion exchanger and eluted after a high salt gradient. The active fraction showed N-terminal amino acid sequence identity with human milk α-lactalbumin and mass spectrometry ruled out post-translational modifications. Size exclusion chromatography resolved monomers and oligomers of α-lactalbumin that were characterized using UV absorbance, fluorescence, and circular dichroism spectroscopy. The high molecular weight oligomers were kinetically stable against dissociation into monomers and were found to have an essentially retained secondary structure but a less well organized tertiary structure. Comparison with native monomeric and molten globule α-lactalbumin showed that the active fraction contains oligomers of α-lactalbumin that have undergone a conformational switch toward a molten globule-like state. Oligomerization appears to conserve α-lactalbumin in a state with molten globule-like properties at physiological conditions. The results suggest differences in biological properties between folding variants of α-lactalbumin.

Antibodies to pneumococcal polysaccharides in human milk: lack of relationship to colonization and acute otitis media

BACKGROUNDnThis study analyzed antibodies to pneumococcal polysaccharides in human milk and their effect on nasopharyngeal colonization and acute otitis media in breast-fed infants.nnnMETHODSnA total of 503 milk samples were collected from 310 mothers. Nasopharyngeal cultures were obtained from their children at 2, 6 and 10 months postpartum, and the capsular groups/types of the Streptococcus pneumoniae isolates were determined.nnnRESULTSnTypes 6A, 6B, 19A, 19F and 23F accounted for 54% of the pneumococcal isolates, but type 3 isolates were uncommon. Milk samples were analyzed for antibody activity to the common capsular polysaccharide types 6A, 19F and 23F; to the type 3 polysaccharide; to C-polysaccharide; and to phosphorylcholine (PC), a major component of the pneumococcal cell wall polysaccharide (CWPS). Anti-capsular antibody activity was low or absent in > 90% of the milk samples. In contrast anti-PC antibody activity was detected in 88% and anti-CWPS in 84% of the samples. The frequency of acute otitis media did not vary with the milk anti-capsular, anti-PC or anti-CWPS antibody activity.nnnCONCLUSIONSnThere was no reduction in nasopharyngeal carriage of S. pneumoniae among children fed milk with anti-capsular or anti-PC antibody activity, but carriage was increased in those children who received milk with anti-CWPS antibody activity. A protective role of antipolysaccharide or anti-CWPS antibodies in milk was not detected under the study conditions.