Alterations in Intestinal Innate Mucosal Immunity of Weaned Pigs During Porcine Epidemic Diarrhea Virus Infection

Abstract

In the small intestine, localized innate mucosal immunity is critical for intestinal homeostasis. Porcine epidemic diarrhea virus (PEDV) infection induces villus injury and impairs digestive function. Moreover, the infection might comprise localized innate mucosal immunity. This study investigated specific enterocyte subtypes and innate immune components of weaned pigs during PEDV infection. Four-week-old pigs were orally inoculated with PEDV IN19338 strain (n = 40) or sham-inoculated (n = 24). At day post inoculation (DPI) 2, 4, and 6, lysozyme expression in Paneth cells, cellular density of villous and Peyer’s patch microfold (M) cells, and the expression of polymeric immunoglobulin receptor (pIgR) were assessed in the jejunum and ileum by immunohistochemistry, and interleukin (IL)-1β and tumor necrosis factor (TNF)-α were measured in the jejunum by ELISA. PEDV infection led to a decrease in the ratios of villus height to crypt depth (VH–CD) in jejunum at DPI 2, 4, and 6 and in ileum at DPI 4. The number of villous M cells was reduced in jejunum at DPI 4 and 6 and in ileum at DPI 6, while the number of Peyer’s patch M cells in ileum increased at DPI 2 and then decreased at DPI 6. PEDV-infected pigs also had reduced lysozyme expression in ileal Paneth cells at DPI 2 and increased ileal pIgR expression at DPI 4. There were no significant changes in IL-1β and TNF-α expression in PEDV-infected pigs compared to controls. In conclusion, PEDV infection affected innate mucosal immunity of weaned pigs through alterations in Paneth cells, villous and Peyer’s patch M cells, and pIgR expression.

Epithelial-mesenchymal transition of absorptive enterocytes and depletion of Peyer's patch M cells after PEDV infection

“…Interestingly, these post-infection alterations in villus tips were observed in jejunum but not in the ileum. Based on our previous study ( Chen et al, 2020 ), PEDV infection resulted in decreased VH:CD ratios in jejunum on DPI 2, 4, and 6 and in ileum on DPI 4 only, and the results indicate that jejunum had more severe villus injury than ileum. Moreover, in the present study, a positive correlation was observed between the E-cadherin expression and VH:CD ratio.…”

“…Fixed tissue procedures are described below. The clinical disease incidence, fecal virus shedding data, jejunum and ileum VH:CD ratios, and PEDV antigen detection by immunohistochemistry (IHC) at DPI 2, 4, 6 and 10 have been reported in a previous paper ( Chen et al, 2020 ). Pigs at DPI 10 were selected in the present study to assess intestinal restitution at the end of the study duration.…”

“…The following primary antibodies were used for evaluating small intestinal restitution: monoclonal mouse anti-E-cadherin (Thermo Fisher Scientific, Carlsbad, CA, USA); monoclonal mouse anti-vimentin (Dako, Glostrup, Denmark); polyclonal rabbit anti-Snail (Biorbyt, San Francisco, CA, USA); polyclonal rabbit anti-ZO-1/TJP1 (Thermo Fisher Scientific, Carlsbad, CA, USA); monoclonal mouse anti-actin (Thermo Fisher Scientific, CA, USA); monoclonal mouse anti-human Ki-67 (Dako, Carpinteria, CA, USA); and monoclonal mouse anti-cytokeratin peptide 18 (Sigma-Aldrich, St. Louis, MO, USA). Specificity of these antibodies for swine tissue has been validated ( Chen et al, 2020 ; Jung et al, 2015a ; Ladel et al, 2019 ; Vermeulen et al, 2018 ; Palmieri et al, 2011 ).…”

“…The virus replicates in absorptive epithelial cells of the small intestine and induces apoptosis and necrosis, epithelial cell sloughing, and retraction of villus stromal cores which leads to a decreased villus height to crypt depth ratio (VH:CD) ( Debouck et al, 1981 ; Kim and Lee, 2014 ). Moreover, PEDV infection reduces a number of enterocyte subtypes related to innate immunity, including goblet cells, villus microfold (M) cells, and Peyer's patch M cells ( Jung and Saif, 2017 ; Chen et al, 2020 ). Such localized damage could result in disturbed intestinal homeostasis, including disruption of the microbiota ( Liu et al, 2015 ; Koh et al, 2015 ).…”

Deletion in the S1 Region of Porcine Epidemic Diarrhea Virus Reduces the Virulence and Influences the Virus-Neutralizing Activity of the Antibody Induced

“…The clinical signs in PED virus (PEDV)-infected pigs are age-dependent, wherein younger pigs have higher morbidity and mortality [1]. In weaned pigs, PEDV affects their innate immunity through a decrease in Peyer's patch M cells and lysozyme expression in Paneth cells [2].…”