title: Mannan oligosaccharide increases serum concentrations of antibodies and inflammatory mediators in weanling pigs experimentally infected with porcine reproductive and respiratory syndrome virus.
abstract: Mannan-containing products are capable of modulating immune responses in animals. However, different products may have diverse immunomodulation. The experiment was conducted to examine effects of mannan oligosaccharide (Actigen; ACT) on growth performance and serum concentrations of antibodies and inflammatory mediators in weanling pigs (Sus scrofa) experimentally infected with porcine reproductive and respiratory syndrome virus (PRRSV). A total of 32 PRRSV-negative pigs (3 wk old) were randomly assigned from within blocks to 1 of 4 treatments in a 2 by 2 factorial arrangement [2 types of diet: control (0%) and ACT addition (0.04%); and with and without PRRSV] in a randomized complete block design. Pigs were blocked by initial BW within sex. Ancestry was equalized across treatments. Pigs (8/treatment) were kept individually in each pen. After 2 wk of an 8-wk period of feeding the treatments, pigs received an intranasal inoculation of PRRSV or sham medium at 5 wk of age. Infection by PRRSV decreased ADG, ADFI, and G:F throughout the experiment (P < 0.01). Actigen did not affect ADG (P = 0.450), but decreased (P = 0.047) ADFI from 28 to 42 days postinoculation (DPI). During that time, ACT improved G:F in infected pigs but not in sham controls (interaction, P = 0.009). Dietary ACT did not affect viremia in infected pigs (P > 0.05), but increased PRRSV-specific antibody titer at 35 DPI (P = 0.042). Infection with PRRSV induced the febrile responses of pigs from 3 to 10 DPI (P < 0.001) with return to normal at 14 DPI. During the experimental period, the rectal temperature of pigs was found slightly elevated by ACT (P = 0.045). Infected pigs had greater serum concentrations of IL-1β, tumor necrosis factor (TNF)-α, IL-12, interferon (IFN)-γ, IL-10, and haptoglobin (Hp) than sham controls (P < 0.001). These results indicate that PRRSV stimulated secretion of cytokines involved in innate, T-helper 1, and T-regulatory immune responses. Actigen tended to decrease the serum TNF-α concentration regardless of PRRSV (P = 0.058). The ACT × PRRSV interaction was significant for IL-1β (P = 0.016), IL-12 (P = 0.026), and Hp (P = 0.047), suggesting that infected pigs fed ACT had greater serum concentrations of these mediators than those fed the control. The increases in IL-1β and IL-12 may favorably promote innate and T-cell immune functions in infected pigs fed ACT. Feeding ACT may be useful as ACT is related to increased PRRSV antibody titers and G:F in infected pigs at certain times during infection.
authors.affiliation: Department of Animal Sciences, University of Illinois, Urbana, IL 61801, USA.
authors.forename: T M
authors.initials: TM
authors.lastname: Che
authors.forename: M
authors.initials: M
authors.lastname: Song
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.forename: R W
authors.initials: RW
authors.lastname: Johnson
authors.forename: K W
authors.initials: KW
authors.lastname: Kelley
authors.forename: W G
authors.initials: WG
authors.lastname: Van Alstine
authors.forename: K A
authors.initials: KA
authors.lastname: Dawson
authors.forename: J E
authors.initials: JE
authors.lastname: Pettigrew
mesh_terms: D000209:Acute-Phase Proteins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D007249:Inflammation / Q000378:metabolism*; D008297:Male; D008351:Mannans / Q000627:therapeutic use*; D019318:Porcine Reproductive and Respiratory Syndrome / Q000097:blood / Q000188:drug therapy*; D019316:Porcine respiratory and reproductive syndrome virus / Q000502:physiology*; D013552:Swine; D013997:Time Factors; D014766:Viremia
chemical_list: D000209:Acute-Phase Proteins; D000914:Antibodies, Viral; D016207:Cytokines; D008351:Mannans