Evaluation of the Use of Prenatal Immune Stimulation on the Ability to Alter Postnatal Immune Function in Weaned Pigs

Abstract One of the most lacking areas where improvements can be made in swine production is in the area of swine health. This study was designed to determine whether exposure to low dose endotoxin (lipopolysaccharide; LPS) during gestation can enhance immunity to a subsequent LPS challenge in piglets after weaning. Pregnant Camborough sows (parity: 2.6 ± 1.4) were assigned to prenatal immune stimulation (LPS; n = 7; administered 2.5 µg/kg BW LPS i.m. at d 78 ± 1.8 of gestation) or saline treatment groups (CON; n = 7). From the 2 prenatal treatment groups, barrows (n = 17 LPS, 17 CON) were identified at weaning (21 ± 1.3 d of age) to subsequently receive a post-weaning LPS challenge. On d -7, barrows were transported to the USDA-ARS Livestock Issues Research Unit in Lubbock, TX where they were housed in individual pens in an environmentally controlled building with ad libitum access to water and a starter ration. On d -1, pigs were fitted with indwelling jugular catheters and subcutaneous temperature loggers. On d 0, pigs were challenged i.v. with LPS (10 µg/kg BW) and blood samples were collected at -2, 0, 1, 2, 4, 6, 8, 12, and 24 h relative to LPS challenge. Data were analyzed using PROC MIXED in SAS, specific for repeated measures. There was a treatment × time interaction for subcutaneous temperature (P < 0.01), where temperature increased more quickly at 1 and 2 h post-challenge in LPS compared with CON pigs. There was a tendency (P = 0.08) for less change in white blood cells, relative to baseline values, in LPS compared with CON pigs. There was a treatment × time interaction (P = 0.01) for lymphocyte concentrations where concentrations were reduced in LPS compared with CON pigs at 8 h post-challenge. There was also a treatment × time interaction (P = 0.01) for the change in eosinophil concentrations, where there was less change in eosinophil concentrations from 1 to 12h in LPS compared with CON pigs. There was a tendency (P = 0.08) for a treatment × time interaction for serum interleukin-6 (IL-6), where concentrations were reduced in LPS compared with CON pigs at 2h (P = 0.01) and tended to be reduced at 1 and 4h post-challenge (P ≤ 0.11). There was a tendency (P = 0.06) for a treatment × time interaction for IL-8, where concentrations were reduced in LPS compared with CON pigs at 1 and 4h (P ≤ 0.01) and tended to be reduced at 2h post-challenge (P = 0.06). Granulocyte macrophage colony stimulating factor and tumor necrosis factor-α tended (P ≤ 0.08) to be reduced in LPS compared with CON pigs. These data suggest that exposure to endotoxin in utero can influence the postnatal innate immune response to endotoxin. Thus, it is possible to influence the innate immune response of pigs in utero, which may serve as a method to positively influence postnatal immune responsiveness.