Effects of Intranasal Pseudorabies Virus AH02LA Infection on Microbial Community and Immune Status in the Ileum and Colon of Piglets

Abstract

Pseudorabies virus (PRV) variants broke out in china since 2011, causing high fever, respiratory distress, systemic neurological symptoms, and diarrhea in piglets. This study investigated the effect of intranasal PRV variant (AH02LA) infection on ileal and colonic bacterial communities and immune status in piglets. Ten piglets (free of PRV) were assigned to PRV variant and control groups (uninfected). At day 5 after inoculation, all piglets were euthanized. No PRV was detected in the ileal and colonic mucosa. In the PRV group, we observed up-regulation of specific cytokines gene expression, down-regulation of intestinal barrier-related gene expression, and reduction of secretory immunoglobulin A (sIgA) concentration in the ileum and colon. PRV infection increased the diversity of ileal bacterial community composition. PRV infection reduced the abundance of some beneficial bacteria (Lactobacillus species in the ileum and colon; butyrate-producing bacteria species in the colon) and increased the abundance of potentially pathogenic Fusobacterium nucleatum in the ileum and Sphingomonas paucimobilis in the colon. Moreover, PRV infection decreased concentrations of the beneficial lactate in the ileum and butyrate in the colon. However, this study does not allow to evaluate whether the observed changes are directly due to the PRV infection or rather to indirect effects (fever, clinical signs and changes in diet), and will be our next research content. In summary, our findings provide evidence that intranasal PRV infection directly or indirectly brings gut health risks and implications, although no PRV was detected in the ileum and colon.

Keywords: immune status; intranasal PRV AH02LA infection; microbial community; microbial metabolites; piglets.

Figure 1

Effects of intranasal pseudorabies virus (PRV) AH02LA strain on the mRNA expression of genes related to cytokines and barrier function in the ileal and colonic mucosa of piglets at day 5 post intranasal infection. The values are expressed as the means ± SEM (n = 5). Asterisks indicate statistically significant difference from control. * p < 0.05, ** p < 0.01. The β-actin mRNA level was used to normalize the relative amount of each studied mRNA, and the2^−ΔΔCt method was used to analyze the data. IL, interleukin; IFN-γ, interferon-γ; TNF-α, tumor necrosis factor-α; ZO-1, zonula occludens-1.

Figure 2

Effects of intranasal pseudorabies virus (PRV) AH02LA strain on the concentration of secretory immunoglobulin A (sIgA) in the ileal and colonic digesta of piglets at day 5 post intranasal infection. The values are expressed as the means ± SEM (n = 5). Asterisks indicate statistically significant difference from control. ** p < 0.01.

Figure 3

Diversity of ileal and colonic bacterial community in piglets of control and AH02LA groups. The values are expressed as the means ± SEM (n = 5). Asterisks indicate statistically significant difference from control: * p < 0.05.

Figure 4

Principal coordinate analysis (PCoA) of ileal and colonic bacterial communities in piglets of control and AH02LA groups by Bray–Curtis similarity metric. PC, principal coordinate.

Figure 5

Ileal and colonic bacterial composition profiles at the phylum in piglets of control and AH02LA groups.

Figure 6

Significantly changed genera in the ileal and colonic digesta in piglets of control and AH02LA groups. Values are means ± SEMs (n = 5). Asterisks indicate statistically significant difference from control (Mann–Whitney U test and a false discovery rate). * p < 0.05, ** p < 0.01.

Figure 7

Significantly changed bacteria operational taxonomic units (OTUs) in the ileal and colonic digesta of piglets in control and AH02LA groups. Values are means ± SEMs (n = 5). Asterisks indicated statistically significant difference from control (Mann–Whitney U test and a false discovery rate). * p < 0.05, ** p < 0.01. n.d., no sequence detected.

Figure 8

Effects of intranasal pseudorabies virus (PRV) AH02LA strain on the concentrations of lactate (A) and SCFA (B) in the ileal and colonic digesta of piglets at day 5 post intranasal infection. The values are expressed as the means ± SEM (n = 5). Asterisks indicate statistically significant difference from control. * p < 0.05, ** p < 0.01. SCFA, short-chain fatty acid.

Figure 9

Correlation analysis between bacteria with immune markers or bacterial fermentation products in the ileum and the colon. The red represents a significant positive correlation, and the blue represents a significant negative correlation. * p < 0.05. IL, interleukin; IFN-γ, interferon-γ; TNF-α, tumor necrosis factor-α; ZO-1, zonula occludens-1; sIgA, secretory immunoglobulin A.