Dietary human milk oligosaccharides but not prebiotic oligosaccharides increase circulating natural killer cell and mesenteric lymph node memory T cell populations in noninfected and rotavirus-infected neonatal piglets

Background: Human milk oligosaccharides (HMOs) have antimicrobial and immunomodulatory actions. It has previously been reported that these oligosaccharides contribute to the reduced duration of rotavirus-induced diarrhea in pigs. Objective:Wemeasured the effects of HMOsand prebiotic oligosaccharides on immune cell populations from noninfected and rotavirus-infected pigs. We hypothesized that dietary HMOs would modulate systemic and gastrointestinal immunity. Methods: Colostrum-deprived newborn pigs were fed formula, formula with 4 g HMOs/L (2'-fucosyllactose, lacto-Nneotetraose, 6'-sialyllactose, 3'-sialyllactose, and free sialic acid), or formula with 3.6 g short-chain galactooligosaccharides/L and 0.4 g long-chain fructooligosaccharides/L. On day 10, half of the pigswere infectedwith the porcine rotavirus strain OSU. Peripheral blood mononuclear cell (PBMC), mesenteric lymph node (MLN), and ileal Peyer's patch immune cell populations were assessedwith the use of flowcytometry 5 d postinfection. Interferon-γ (IFN-γ)-producing cellswere assessedwith the use of Enzyme-Linked ImmunoSpot assay. Results: Infection changed immune cell populations with more systemic natural killer (NK) cells, memory effector T cells, and major histocompatibility complex II⁺ cells in infected than noninfected pigs (P < 0.06). Regardless of infection status, HMO-fed pigs had nearly twice as many PBMC NK cells, 36% more MLN effector memory T cells, and 5 times more PBMC basophils than formula-fed pigs (P < 0.04). These populations were intermediate in pigs fed prebiotics. PBMCs from HMO-fed noninfected pigs had twice as many IFN-γ-producing cells as did those from formula-fed noninfected pigs (P = 0.017). The PBMCs and MLNs of formula-fed noninfected pigs had 3 times more plasmacytoid dendritic cells (pDCs) than those of HMO-fed noninfected and formula-fed infected pigs (P < 0.04). In the MLNs, the formula-fed noninfected pigs had more macrophages, pDCs, and mature DCs (P < 0.04) but fewer immature DCs than HMO-fed noninfected pigs (P = 0.022). Conclusions: Dietary HMOs were more effective than prebiotics in altering systemic and gastrointestinal immune cells in pigs. These altered immune cell populations may mediate the effects of dietary HMOs on rotavirus infection susceptibility.