Intraperitoneal injection of β-glucan during the suckling period improved the intestinal health of newly weaned rabbits by enhancing immune responses

Abstract

The newly weaned rabbits are susceptible to unpredictable pathogens, which often lead to diarrhea. Recent studies have confirmed that innate immunity can also be trained. An essential feature of trained immunity is a faster and stronger immune response to both homologous and heterologous reinfections. Therefore, the present study investigated the effect of intraperitoneal injection of β-glucan during the suckling period on protecting weaned rabbits from diarrhea and its mechanism. Sixty-four suckling rabbits were randomly divided into two groups based on litter and weight: the control group (C) and the trained group (T). At 6 and 4 days before weaning, rabbits in the two groups were intraperitoneally injected with physiological saline solution (PSS) and β-glucan dissolved in PSS, respectively, and 10 in each group were randomly selected two weeks after weaning for sampling. Results showed that the diarrhea rate and the crypt depth of the ileum in the trained group were decreased (P < 0.05 or P < 0.01). Compared with the control group, rabbits receiving β-glucan during suckling exhibited an increase in the gene expression of tumor necrosis factor-alpha (TNF-α) and interleukin-10 (IL-10) (P < 0.01) and a decrease in that of interleukin-6 (IL-6) (P < 0.05). Pre-stimulation with β-glucan also increased the concentration of serum immunoglobin A (IgA) and immunoglobin G (IgG) (P < 0.05) and that of ileal secretory immunoglobulin (sIgA) and lysozyme (LYZ) (P < 0.05) after weaning. In addition, the trained rabbits showed lower serum malondialdehyde (MDA) and hydroxyl radical levels (P < 0.001). Notably, the microbial communities of ileum mucus in the trained group showed more homogeneity and aggregation. Our results confirmed that pre-stimulation with β-glucan before weaning improved intestinal health by enhancing the immunity ability of both innate and adaptive immune in the newly weaned rabbits, providing an experimental and theoretical basis for the use of β-glucan-induced trained immunity in preventing intestinal infection after weaning in rabbits.