Immunomodulatory properties of bovine whey proteins and whey protein concentrates : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nutritional Science and Immunology at Massey University, Palmerston North, New Zealand
In recent years, partly due to advances in protein separation technology, many studies have focused on the immunomodulatory activity of bovine milk and colostral protein components. Individual milk proteins have been purified for the purpose of studying their physical properties and physiological functions. Today there is substantial evidence to indicate that the major components of bovine milk, such as whey protein and several highly purified whey protein isolates, can regulate immune function in heterologous species. Intense research has focused on identifying biologically active components within bovine milk whey, as well as characterising the mode by which mammalian immune function is modulated by these components. However, information regarding the effect of bovine whey proteins on immune responses to orally and parentally-administered antigens is currently conflicting and far from exhaustive. Consequently, this thesis sought not only to investigate the immunomodulatory ability of previously untested bovine whey products on general immunoresponses but also to investigate the ability of bovine whey proteins to modulate murine immune responses to vaccines currently in routine medical use. Initially, individual whey proteins (α-lactalbumin, β-lactoglobulin and lactoferrin) were screened for their in vitro effects on lymphoid cell function and phagocytic function. These in vitro studies found that the individual whey protein components had a positive immunomodulatory effect, providing evidence that these components have the potential to enhance immune function, and investigation into their immunomodulatory capabilities in an in vivo murine model was consequently undertaken. The results of the in vivo studies demonstrated that the dietary whey protein isolates and whey protein concentrate tested in this study could not only enhance two important indices of ex vivo lymphoid and non-lymphoid cell function (lymphocyte proliferation and phagocytic function) but could enhance mucosal and systemic antibody responses to orally and systemically administered human vaccines. The demonstrated benefits to the immune system of dietary whey proteins in the murine model could result in the production of immune-boosting, nutritionally and physiologically advantageous food supplements suitable for human consumption. Of particular relevancy to modern human health is the use of whey proteins as dietary adjuvants or immunopotentiators to increase immune responses to commonly administered vaccines.