Tryptophan Supplements Promote Pregnancy Success in Mice Challenged with Pseudorabies Virus (PRV) by Regulating the Expression of Systemic Cytokines, Immunoglobulins, PRV-Specific Protein Profiles, and Toll-Like Receptors

Tryptophan (Trp) plays an important role in regulating the maternal immune response, a key determinant of the success or failure of pregnancy, but whether Trp supplements can prevent a pseudorabies virus (PRV)-induced failure of pregnancy remains unknown. This study examined the effect of three dietary Trp levels (0.25%, 0.35%, and 0.5%) on the immunity and reproduction of PRV-challenged pregnant mice. PRV challenge resulted in decreased live embryo numbers, live litter sizes, and serum progesterone and interleukin (IL)-10 concentrations, but increased the levels of serum immunoglobulins (Igs) (PRV-specific antibody [IgG, IgA, and IgM]) and IL-1 beta. Live embryo numbers, live litter sizes, serum progesterone concentration, and IgG and PRV-specific antibody levels on day 9 of pregnancy were all increased dose-dependently by Trp inclusion in the diet of PRV-challenged mice. Increased Trp levels in PRV-challenged mice promoted the up-regulation of uterine and embryonic indoleamine 2,3-dioxygenase expression, but attenuated the up-regulation of uterine and embryonic Toll-like receptor (TLR) 3 and TLR9 expression and increased serum interferon-gamma concentration. Collectively, Trp supplements might improve reproductive performance of PRV-challenged pregnant mice by down-regulating TLR expression and pro-inflammatory cytokine synthesis, by up-regulating PRV-specific antibody and immunoglobulin synthesis, and by elevating the concentrations of anti-inflammatory cytokines and progesterone.