Colostral proteins from cows immunised with Streptococcus mutans/S-sobrinus support the phagocytosis and killing of mutans streptococci by human leucocytes

Passive immunisation, based on bovine colostral preparations, is an area of active research. Specific bovine antibodies inhibit the virulence factors of target pathogens but the interactions between whey preparations and huma n immune defence cells are not well known. Bovine colostrum inhibits the ph agocytic activity of bovine leucocytes and this may reflect the biological activity of immunoglobulins in it. Therefore, this study aimed to examine t he effects of bovine whey protein preparations from the colostrum of Strept ococcus mutans/S. sobrinus-immunised and sham-immunised cows on binding, in gestion and killing of these bacteria by human leucocytes. Binding and inge stion of FITC-labelled bacteria were estimated by flow cytometry and leukoc yte activation was measured as chemiluminescence. Killing rate was estimate d by plate counting and by measuring bioluminescence from S. mutans- contai ning the insect luciferase gene. Colostral whey protein preparation from hy perimmunised cows activated human leucocytes by opsonising specific bacteri a. Neutrophils, eosinophils and monocytes weakly phagocytosed non-opsonised bacteria and bacteria opsonised with control product. On the contrary, bin ding and ingestion were efficient in the presence of the preparation from i mmunised cows, Thus, these results show that bovine colostral whey proteins are able to support the activation of human phagocytes against pathogenic microbes and that this property is related to specific antibodies in whey p reparations, These whey proteins may also be clinically useful, especially in preventing the colonisation of newly erupted teeth by mutans streptococc i.