Effects of Casein Phosphopeptide-Selenium Complex on the Immune Functions in Beagle Dogs

Simple Summary Although the functions of casein phosphopeptide (CPP) and selenium (Se) as immunomodulators have been demonstrated, research on the regulation of pets' immunity in the form of an organic combination of these two substances have yet to be reported, particularly in dogs. The purpose of this research was to look into the effects of the casein phosphopeptide-selenium complex (CPP-Se) on dog immunity. Our findings show that feeding a snack supplemented with CPP-Se for 30 days can increase the number of blood lymphocytes and improve the expression of cytokine-related genes in peripheral blood lymphocytes (PBL). In addition, serum levels of cytokine-related proteins and immunoglobulins were increased. Furthermore, cell proliferation and expression of cytokine-related mRNAs were also increased when PBL was exposed to CPP-Se in vitro. Collectively, feeding CPP-Se strengthens various immune indicators in dogs, thereby enhancing immunity. This research provides theoretical support for the development of related functional foods and formulations to improve the immunity and health of dogs and other pets in the future. The health of pets is becoming a growing concern for the pet industry and its owners. Immunity is one of the foundational supports for health, thus developing a functional bioactive substance that can boost pets' immunity is essential. Many studies have shown that casein phosphopeptide (CPP) and selenium (Se) can individually regulate immunity in many species, but there has been no reported research on the immunomodulatory function of casein phosphopeptide-selenium complex (CPP-Se). The objective of this study was to investigate the function of CPP-Se on immunomodulation in dogs. Twenty Beagle dogs were equally divided into two groups and fed either a control snack or a test snack supplemented with 0.03% CPP-Se for 30 days. Anticoagulated blood, serum and peripheral blood lymphocytes (PBL) were collected from dogs at 0 d, 10 d, 20 d and 30 d to detect the change in the number of immune cells and the expression of cytokine-related mRNAs and proteins. PBL isolated from blood were exposed to CPP-Se in vitro to measure the proliferative responses and cytokine-related mRNAs expression. During the time the test snack was fed, the number of lymphocytes increased significantly, whereas neutrophils and monocytes remained unaltered. The expression of interleukin-4 (IL-4), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), CD4 molecule (CD4) and CD8 alpha molecule (CD8 alpha) was up-regulated, while interleukin-1 beta (IL-1 beta) was down-regulated, and interleukin-10 (IL-10) declined initially and subsequently increased. ELISA detection revealed a significant increment in serum IL-4, IL-6, Immunoglobulin M (IgM) and IFN-gamma, except for IgG. Furthermore, CPP-Se treatment increased the proliferation and the expression of cytokine-related mRNAs in PBL cultured in vitro. This is the first study to demonstrate that CPP-Se can improve immunity in the dog.