Probiotic Lactococcus lactis (LL) is immunomodulatory and may prevent
allergy by biasing from type-2 to a type-1 immune response. We hypothesized that newborn pigs pre-treated orally with LL are protected against
allergy to
ovomucoid (Ovm). Pigs were assigned to two treatment groups. Piglets were pretreated orally on days of age 1-7, 10, 12, 14, 21, 28 and 35 with LL (
n=30) or medium (control, n=32) and sensitized to Ovm by
intraperitoneal injection together with
cholera toxin on days 14, 21 and 35. Pigs were orally challenged with egg white (day 46) and assigned scores for allergic signs. Outcomes were measured as direct skin tests, serum antibody to Ovm [
IgG (H+L);
IgE;
IgG(1) and
IgG(2)] and
cytokine production by
mitogen-stimulated blood mononuclear cells (BMC). Clinical signs and skin test positivity were less frequent in the LL group (p ≤ 0.0001). Serum antibody associated with
IgG (H and L),
IgE,
IgG(1) or
IgG(2) was significantly increased on day 46 (post-sensitization) compared to day 14 (pre-sensitization) (p ≤ 0.0001). The LL-treated pigs had more
IgE and IgG(2)-related antibody activity and lower
IgG(1)/
IgG(2) and
IgE/
IgG(2) ratios indicating a type-1 bias in immune response (p ≤ 0.05). Concentration of type-2
cytokines interleukin IL-4 and
IL-10 were significantly lower in supernatants of stimulated BMC of LL-treated pigs (p ≤ 0.0001).
Interferon-γ, TGF-β and
IL-13 were not detected in control or treated animals. Thus, oral treatment of neonatal pigs with LL significantly reduced subsequent frequency of
allergy to Ovm associated with reduced type-2 immune response correlates hence supporting the "hygiene hypothesis" and potential use of LL as a neonatal immunoregulator.