Abstract Weaning in conventional pig production is a stressful event that involves abrupt dietary and environmental changes, and the post-weaning period is associated with increased incidence of disease and antibiotic use. As a result, there is a growing demand for non-antibiotic practices to enhance health during this phase of production. Current production systems wean piglets at a relatively young age, and it is unclear if age at weaning impacts shifts in intestinal immune populations, particularly intraepithelial T lymphocyte (T-IEL) populations, or bacterial communities in a comparable timeframe and magnitude. T-IELs reside in the intestinal epithelium and play a role in intestinal integrity and defense. While later weaning may be an approach to minimize the negative impacts of weaning, the impact of age at weaning on T-IEL abundances and function is not clearly understood. Our results indicate pigs weaned at 18–21 days of age (standard weaned, SW), which is consistent with production practices in the United States, had delayed shifts in T-IEL populations when compared to pigs weaned at 25–28 days of age (late weaned, LW), which is consistent with practices in the European Union. Specifically, the abundance of induced T-IELs (CD8ab+ ab T cells) in the jejunum increased between 0 and 3 days post weaning (dpw) for the LW group and stabilized, but shifts were delayed until between 3dpw and 7dpw in the SW group. Concomitant decreases in the abundance of natural T-IEL (gd T cells) were detected. The structure of jejunal mucosal bacterial communities were comparable between SW and LW pigs at 0dpw, but the SW group had more pronounced shifts from 3dpw to 7dpw and 7dpw to 14dpw compared to minimal shift in LW group from 7dpw to 14dpw. Body weight between groups was comparable when adjusted for age. Overall, the bacterial communities of the jejunal mucosa were more stable after weaning in LW than SW pigs, and jejunal T-IEL abundances stabilized more rapidly in the LW group. As T-IELs play a key role in intestinal homeostasis and barrier integrity, the early differences in population abundance may be indicative of functional differences as well.

Diarrhoea and preweaning mortality in piglets are crucial factors impacting the economic sustainability of the swine industry. Pathogenic infections are among the main causes of diarrhea and mortality. Group 3 innate lymphoid cells (ILC3s) are crucial for safeguarding against pathogenic infections. However, knowledge regarding the development and function of ILC3s in suckling piglets is currently limited. Our findings demonstrate that the development of ILC3s in suckling piglets gradually progresses from day 1 to day 21, with a notable increase observed on day 28. Additionally, the development of NKp46+ILC3s and the production of interleukin (IL)-17A by ILC3s displayed consistent patterns with the changes observed in ILC3s. Notably, interferon (IFN)-γ levels significantly increased on day 14. Moreover, the production of IFN-γ by NKp46+ILC3s was greater than that by NKp46-ILC3s. Importantly, when piglets were subjected to a 4-h challenge with enterotoxigenic Escherichia coli, both the percentages of ILC3s significantly increased, accompanied by increased IL-22 production, highlighting their importance in maintaining intestinal health. The outcomes of this study provide valuable insights for future related research.
© 2024. The Author(s).

Genetic modification of genes such as recombination activating gene 2 (RAG2) or interleukin-2 receptor-γ (IL2RG) results in pigs exhibiting severe combined immunodeficiency (SCID). Pigs presenting a SCID phenotype are important animal models that can be used to establish xenografts and to study immune system development and various immune-related pathologies. However, due to their immunocompromised nature, SCID pigs have shortened lifespans and are notoriously difficult to maintain. The failure-to-thrive phenotype makes the establishment of a breeding population of RAG2/IL2RG double-knockout pigs virtually impossible. Here, to overcome this limitation, we investigated whether reconstituting the immune system of SCID piglets with a fetal bone allograft would extend their lifespan. Following intramuscular transplantation, allografts gave rise to lymphocytes expressing T cell (CD3, CD4 and CD8), B cell (CD79α) and natural killer cell (CD335) lineage markers, which were detected in circulation as well in the spleen, liver, bone marrow and thymic tissues. The presence of lymphocytes indicates broad engraftment of donor cells in the recipient SCID pigs. Unlike unreconstituted SCID pigs, the engrafted animals thrived and reached puberty under standard housing conditions. This study demonstrates a novel method to extend the survival of SCID pigs, which may improve the availability and use of SCID pigs as a biomedical animal model.
© 2024. The Author(s).

Appropriate iron supplementation is essential for neonatal growth and development. However, there are few reports on the effects of iron overload on neonatal growth and immune homeostasis. Thus, the aim of this study was to investigate the effects of iron nutrition on neonatal growth and intestinal immunity by administering different levels of iron to neonatal pigs.
We found that iron deficiency and iron overload resulted in slow growth in neonatal pigs. Iron deficiency and iron overload led to down-regulation of jejunum intestinal barrier and antioxidant marker genes, and promoted CD8+ T cell differentiation in jejunum and mesenteric lymph nodes (MLN) of pigs, disrupting intestinal health. Moreover, iron levels altered serum iron and tissue iron status leading to disturbances in redox state, affecting host innate and adaptive immunity.
These findings emphasized the effect of iron nutrition on host health and elucidated the importance of iron in regulating redox state and immunity development. This study provided valuable insights into the regulation of redox state and immune function by iron metabolism in early life, thus contributing to the development of targeted interventions and nutritional strategies to optimize iron nutrition in neonates.
© 2024. The Author(s).

The gut microbiota is a critical factor in the regulation of host health, but the relationship between the differential resistance of hosts to pathogens and the interaction of gut microbes is not yet clear. Herein, we investigated the potential correlation between the gut microbiota of piglets and their disease resistance using single-cell transcriptomics, 16S amplicon sequencing, metagenomics, and untargeted metabolomics.
Porcine epidemic diarrhea virus (PEDV) infection leads to significant changes in the gut microbiota of piglets. Notably, Landrace pigs lose their resistance quickly after being infected with PEDV, but transplanting the fecal microbiota of Min pigs to Landrace pigs alleviated the infection status. Macrogenomic and animal protection models identified Lactobacillus reuteri and Lactobacillus amylovorus in the gut microbiota as playing an anti-infective role. Moreover, metabolomic screening of the secondary bile acids' deoxycholic acid (DCA) and lithocholic acid (LCA) correlated significantly with Lactobacillus reuteri and Lactobacillus amylovorus, but only LCA exerted a protective function in the animal model. In addition, LCA supplementation altered the distribution of intestinal T-cell populations and resulted in significantly enriched CD8+ CTLs, and in vivo and in vitro experiments showed that LCA increased SLA-I expression in porcine intestinal epithelial cells via FXR receptors, thereby recruiting CD8+ CTLs to exert antiviral effects.
Overall, our findings indicate that the diversity of gut microbiota influences the development of the disease, and manipulating Lactobacillus reuteri and Lactobacillus amylovorus, as well as LCA, represents a promising strategy to improve PEDV infection in piglets. Video Abstract.
© 2024. The Author(s).