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

Bacillus licheniformis-based intensive fermentation of Tibetan tea improved its bioactive compounds and reinforced the intestinal barrier in mice

Tibetan tea changes during microorganism fermentation. Research on microorganisms in Tibetan tea has focused on their identification, while studies on the influence of specific microorganisms on the components and health functions of Tibetan tea are lacking. Bacillus licheniformis was inoculated into Tibetan tea for intensive fermentation, and the components of B. licheniformis-fermented tea (BLT) were detected by liquid chromatography with tandem mass spectrometry (UHPLC-TOF-MS), and then the effects of BLT on intestinal probiotic functions were investigated by experiments on mice. The results revealed the metabolites of BLT include polyphenols, alkaloids, terpenoids, amino acids, and lipids. Intensified fermentation also improved the antioxidant capacity in vivo and the protective effect on the intestinal barrier of Tibetan tea. In addition, the enhanced fermentation of Tibetan tea exerted intestinal probiotic effects by modulating the relative abundance of short-chain fatty acid-producing bacteria in the intestinal flora. Therefore, intensive fermentation with B. licheniformis can improve the health benefits of Tibetan tea.

The immunity protection of intestine induced by pseudorabies virus del gI/gE/TK in piglets

Compared to the classical strain of Pseudorabies virus (PRV), the PRV variant exhibits stronger transmissibility and pathogenicity, causing immense disasters for the global pig industry. Based on this variant, our laboratory has preliminarily constructed a modified pseudorabies virus with deletions in the gE/gI/TK genes. In this study, the protective efficacy of PRV XJ del gI/gE/TK against piglet intestinal damage was evaluated. The results demonstrated that piglets immunized with PRV XJ del gI/gE/TK exhibited alleviated intestinal damage caused by the PRV XJ variant strain. This included reduced viral load, suppressed inflammation, and maintenance of intestinal structure and function. Additionally, PRV XJ del gI/gE/TK also strongly activated the innate immune response in the intestines, increasing the expression of antiviral factor mRNA and the secretion of SIgA to counteract the attack of the PRV XJ variant strain. Our study indicates that PRV XJ del gI/gE/TK can inhibit intestinal damage caused by PRV XJ variant strain and activate the innate immune response in the intestines.

Construction of pseudorabies virus variant attenuated vaccine: codon deoptimization of US3 and UL56 genes based on PRV gE/TK deletion strain

Since 2011, pseudorabies based on the pseudorabies virus (PRV) variant has emerged as a serious health issue in pig farms in China. The PRV gE/TK or gE/gI/TK deletion strains protect against emerging PRV variants. However, these variants may cause lethal infections in newborn piglets without PRV antibodies. Previous studies have shown that codon deoptimization of a virulence gene causes virus attenuation. Accordingly, we deoptimized US3-S (US3 gene encoding a short isoform that represents approximately 95% of the total US3 transcription) and UL56 genes (first 10 or all codons) of PRV gE/TK deletion strain (PRVΔTK&gE-AH02) to generate six recombinant PRVs through bacterial artificial chromosome technology. In swine testicular cells, recombinant PRVs with all codon deoptimization of US3-S or UL56 genes were grown to lower titers than the parental virus. Notably, US3-S or UL56 with all codon deoptimization reduced mRNA and protein expressions. Subsequently, the safety and immunogenicity of recombinant PRVs with codon deoptimization of US3-S or UL56 are evaluated as vaccine candidates in mice and piglets. The mice inoculated with recombinant PRVs with codon deoptimization of US3-S or UL56 showed exceptional survival ability without severe clinical signs. All codons deoptimized (US3-S and UL56) significantly decreased virus load and attenuated pathological changes in the brains of the mice. Moreover, the protection efficiency offered by recombinant PRVs with codon deoptimization of US3-S or UL56 showed similar effects to PRVΔTK&gE-AH02. Remarkably, the 1-day-old PRV antibody-negative piglets inoculated with PRVΔTK&gE-US3-ST-CD (a recombinant PRV with all codon deoptimization of US3-S) presented no abnormal clinical symptoms, including fever. The piglets inoculated with PRVΔTK&gE-US3-ST-CD showed a high serum neutralization index against the PRV variant. In conclusion, these results suggest using codon deoptimization to generate innovative live attenuated PRV vaccine candidates.

Duck plague virus infection alter the microbiota composition and intestinal functional activity in Muscovy ducks

Intestinal damage from the duck plague virus (DPV) infection affects intestinal inflammation factors expression and barrier dysfunction. Here we report findings from the pathogenicity of the intestinal tract, intestinal morphological, intestinal permeability, inflammatory cytokines, and tight junction gene expression in 72 two-wk-old Muscovy ducks exposed to DPV. The characterization of intestinal metabolites and their classification were examined using 16-sequencing technology. The primary outcomes of the study evaluated the correlation between intestinal microbiota characteristics and the degree of infected tissue. The secondary outcomes were to determine whether the biosignatures that defined the microbiota were positively or negatively correlated with viral infection. The tissue was infected accompanied a mild damage of liver and spleen, and severe intestinal bleeding. Two inoculation routes were constructed with susceptible animals to assess the pathogenicity of the DPV in order to enrich the status of infection in Muscovy ducks. High levels of virus titer from Muscovy ducks were found being in the intestine. The expression of INF-α and IL-β with viral infection increased at 4, and 6 dpi, respectively, after detecting of the inflammatory factor and barrier function genes. At 4 and 6 dpi, barrier function gene of ZO-1 and Occludin reduced. The severity of viral infection was significantly correlated with the characteristics of the intestinal microbiota. Ducks infected with the DPV had an increase in the phylum Firmicutes, a decrease in the phylum Actinobacteriota, and differential enrichment with the genus Bacteroides, Tyzzerella, Enterococcus, and Escherchia-Shigella, while the genus Rothia, Streptococcus, and Ralstonia were differentially enriched in the control group. The findings from the current study demonstrated that DPV infection leads to an imbalance of the intestinal microbiota and disruption of the microbial homeostasis in the intestinal tissue in ducks, which might be one of the mechanisms whereby DPV infection might be established in Muscovy ducks. Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase activity monitoring also showed that viral infection reduced these activities. These findings imply that changes in intestinal microbiota, intestinal barrier gene expression, and inflammatory factor are related to viral infection. When taken as a whole, this work provides fresh perspectives on the characteristics of intestinal microbiota and the infection damage caused by the DPV.

Pseudorabies virus-induced expression and antiviral activity of type I or type III interferon depend on the type of infected epithelial cell

Type I and III Interferons (IFNs) are the initial antiviral cytokines produced in response to virus infection. These IFNs in turn bind to their respective receptors, trigger JAK-STAT signaling and induce the expression of IFN-stimulated genes (ISGs) to engage antiviral functions. Unlike the receptor for type I IFNs, which is broadly expressed, the expression of the type III IFN receptor is mainly confined to epithelial cells that line mucosal surfaces. Accumulating evidence has shown that type III IFNs may play a unique role in protecting mucosal surfaces against viral challenges. The porcine alphaherpesvirus pseudorabies virus (PRV) causes huge economic losses to the pig industry worldwide. PRV first replicates in the respiratory tract, followed by spread via neurons and via lymph and blood vessels to the central nervous system and internal organs, e.g. the kidney, lungs and intestinal tract. In this study, we investigate whether PRV triggers the expression of type I and III IFNs and whether these IFNs exert antiviral activity against PRV in different porcine epithelial cells: porcine kidney epithelial cells (PK-15), primary respiratory epithelial cells (PoREC) and intestinal porcine epithelial cells (IPEC-J2). We show that PRV triggers a multiplicity of infection-dependent type I IFN response and a prominent III IFN response in PK-15 cells, a multiplicity of infection-dependent expression of both types of IFN in IPEC-J2 cells and virtually no expression of either IFN in PoREC. Pretreatment of the different cell types with equal amounts of porcine IFN-λ3 (type III IFN) or porcine IFN-α (type I IFN) showed that IFN-α, but not IFN-λ3, suppressed PRV replication and spread in PK-15 cells, whereas the opposite was observed in IPEC-J2 cells and both types of IFN showed anti-PRV activity in PoREC cells, although the antiviral activity of IFN-α was more potent than that of IFN-λ3 in the latter cell type. In conclusion, the current data show that PRV-induced type I and III IFN responses and their antiviral activity depend to a large extent on the epithelial cell type used, and for the first time show that type III IFN displays antiviral activity against PRV in epithelial cells from the respiratory and particularly the intestinal tract.

Bacterial and Viral Co-Infection in the Intestine: Competition Scenario and Their Effect on Host Immunity

Bacteria and viruses are both important pathogens causing intestinal infections, and studies on their pathogenic mechanisms tend to focus on one pathogen alone. However, bacterial and viral co-infections occur frequently in clinical settings, and infection by one pathogen can affect the severity of infection by another pathogen, either directly or indirectly. The presence of synergistic or antagonistic effects of two pathogens in co-infection can affect disease progression to varying degrees. The triad of bacterial–viral–gut interactions involves multiple aspects of inflammatory and immune signaling, neuroimmunity, nutritional immunity, and the gut microbiome. In this review, we discussed the different scenarios triggered by different orders of bacterial and viral infections in the gut and summarized the possible mechanisms of synergy or antagonism involved in their co-infection. We also explored the regulatory mechanisms of bacterial–viral co-infection at the host intestinal immune interface from multiple perspectives.

The antiviral activity of kaempferol against pseudorabies virus in mice

Background

Pseudorabies virus (PRV), a member of the Alphaherpesviruses, is one of the most important pathogens that harm the global pig industry. Accumulated evidence indicated that PRV could infect humans under certain circumstances, inducing severe clinical symptoms such as acute human encephalitis. Currently, there are no antiviral drugs to treat PRV infections, and vaccines available only for swine could not provide full protection. Thus, new control measures are urgently needed.

Results

In the present study, kaempferol exhibited anti-PRV activity in mice through improving survival rate by 22.22 %, which was higher than acyclovir (Positive control) with the survival rate of 16.67 % at 6 days post infection (dpi); meanwhile, the survival rate was 0 % at 6 dpi in the infected-untreated group. Kaempferol could inhibit the virus replication in the brain, lung, kidney, heart and spleen, especially the viral gene copies were reduced by over 700-fold in the brain, which was further confirmed by immunohistochemical examination. The pathogenic changes induced by PRV infection in these organs were also alleviated. The transcription of the only immediate-early gene IE180 in the brain was significantly inhibited by kaempferol, leading to the decreased transcriptional levels of the early genes (EPO and TK). The expression of latency-associated transcript (LAT) was also inhibited in the brain, which suggested that kaempferol could inhibit PRV latency. Kaempferol-treatment could induce higher levels of IL-1β, IL-4, IL-6, TNF-α and IFN-γ in the serum at 3 dpi which were then declined to normal levels at 5 dpi.

Conclusions

These results suggested that kaempferol was expected to be a new alternative control measure for PRV infection.

Identification of four insertion sites for foreign genes in a pseudorabies virus vector

Background

Pseudorabies virus (PRV) is a preferred vector for recombinant vaccine construction. Previously, we generated a TK&gE-deleted PRV (PRV^{ΔTK&gE−AH02}) based on a virulent PRV AH02LA strain. It was shown to be safe for 1-day-old piglets with maternal PRV antibodies and 4 ~ 5 week-old PRV antibody negative piglets and provide rapid and 100 % protection in weaned pigs against lethal challenge with the PRV variant strain. It suggests that PRV^TK&gE−AH02 may be a promising live vaccine vector for construction of recombinant vaccine in pigs. However, insertion site, as a main factor, may affect foreign gene expression.

Results

In this study, we constructed four recombinant PRV-S bacterial artificial chromosomes (BACs) carrying the same spike (S) expression cassette of a variant porcine epidemic diarrhea virus strain in different noncoding regions (UL11-10, UL35-36, UL46-27 or US2-1) from AH02LA BAC with TK, gE and gI deletion. The successful expression of S gene (UL11-10, UL35-36 and UL46-27) in recombinant viruses was confirmed by virus rescue, PCR, real-time PCR and indirect immunofluorescence. We observed higher S gene mRNA expression level in swine testicular cells infected with PRV-S(UL11-10)ΔTK/gE and PRV-S(UL35-36)ΔTK/gE compared to that of PRV-S(UL46-27)ΔTK/gE at 6 h post infection (P < 0.05). Moreover, at 12 h post infection, cells infected with PRV-S(UL11-10)ΔTK/gE exhibited higher S gene mRNA expression than those infected with PRV-S(UL35-36)ΔTK/gE (P = 0.097) and PRV-S(UL46-27)ΔTK/gE (P < 0.05). Recovered vectored mutant PRV-S (UL11-10, UL35-36 and UL46-27) exhibited similar growth kinetics to the parental virus (PRV^{ΔTK&gE−AH02}).

Conclusions

This study focuses on identification of suitable sites for insertion of foreign genes in PRV genome, which laids a foundation for future development of recombinant PRV vaccines.

The pig as a medical model for acquired respiratory diseases and dysfunctions: An immunological perspective

By definition no model is perfect, and this also holds for biology and health sciences. In medicine, murine models are, and will be indispensable for long, thanks to their reasonable cost and huge choice of transgenic strains and molecular tools. On the other side, non-human primates remain the best animal models although their use is limited because of financial and obvious ethical reasons. In the field of respiratory diseases, specific clinical models such as sheep and cotton rat for bronchiolitis, or ferret and Syrian hamster for influenza and Covid-19, have been successfully developed, however, in these species, the toolbox for biological analysis remains scarce. In this view the porcine medical model is appearing as the third, intermediate, choice, between murine and primate. Herein we would like to present the pros and cons of pig as a model for acquired respiratory conditions, through an immunological point of view. Indeed, important progresses have been made in pig immunology during the last decade that allowed the precise description of immune molecules and cell phenotypes and functions. These progresses might allow the use of pig as clinical model of human respiratory diseases but also as a species of interest to perform basic research explorations.

Bacillus amyloliquefaciens TL Downregulates the Ileal Expression of Genes Involved in Immune Responses in Broiler Chickens to Improve Growth Performance

Bacillus amyloliquefaciens TL promotes broiler chicken performance by improving nutrient absorption and utilization and reducing intestinal inflammation. In this study, RNA-sequencing (RNA-seq)-based transcriptomes of ileal tissues collected from probiotic-fed and control broiler chickens were analyzed to elucidate the effects of the probiotic B. amyloliquefaciens TL, as a feed additive, on the gut immune function. In total, 475 genes were significantly differentially expressed between the ileum of probiotic-fed and control birds. The expression of genes encoding pyruvate kinase, prothymosin-α, and heat stress proteins was high in the ileum of probiotic-fed birds (FPKM > 500), but not in the control group. The gene ontology functional enrichment and pathway enrichment analyses revealed that the uniquely expressed genes in the control group were mostly involved in immune responses, whereas those in the probiotic group were involved in fibroblast growth factor receptor signaling pathways and positive regulation of cell proliferation. Bacillus amyloliquefaciens TL downregulated the expression of certain proinflammatory factors and affected the cytokine–cytokine receptor interaction pathway. Furthermore, B. amyloliquefaciens TL in broiler diets altered the expression of genes involved in immune functions in the ileum. Thus, it might contribute to improved broiler growth by regulating the immune system and reducing intestinal damage in broilers.

Intestinal Viral Loads and Inactivation Kinetics of Livestock Viruses Relevant for Natural Casing Production: a Systematic Review and Meta-Analysis

Animal intestines are the source of edible sausage casings, which are traded worldwide and may come from areas where notifiable infectious animal diseases are prevalent. To estimate the risks of virus contamination, knowledge about the quantity of virus and decimal reduction values of the standard preservation method by salting is of great importance. A literature search, based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, was performed in search engine CAB Abstracts to determine the viral load of 14 relevant animal viruses in natural casings or intestines. Only a very limited number of scientific publications per virus were found and viral loads in the intestines varied from high for ASFV (five publications), BVDV (3), CSFV (6), PPRV (3), RPV (2) and TGEV (3) to moderate for PEDV (2) and SVDV (3), low for HEV (2) and FMDV (5), very low for VESV (1) and negative for PrV (2) and VSV (1). PRRSV was found in intestines, however, viral titers were not published. Three viruses (BVDV, CSFV and PPRV) with high viral loads were selected to search for their inactivation kinetics. For casings, no inactivation data were found, however, thermal inactivation data of these viruses were available, but differed in quantity, quality and matrices. In conclusion, important data gaps still exist when it comes to the quantitative inactivation of viruses in sausage casings or livestock intestines.

Protein Level and Infantile Diarrhea in a Postweaning Piglet Model

Infantile diarrhea is a serious public health problem around worldwide and results in millions of deaths each year. The levels and sources of dietary protein are potential sources of diarrhea, but the relationship between the pathogenesis causes of infantile diarrhea and protein intake remains poorly understood. Many studies have indicated that the key to understanding the relationship between the protein in the diet and the postweaning diarrhea of piglets is to explore the influences of protein sources and levels on the mammalian digestion system. The current study was designed to control diarrhea control by choosing different protein levels in the diet and aimed at providing efficient regulatory measures for infantile diarrhea by controlling the protein levels in diets using a postweaning piglets model. To avoid influences from other protein sources, casein was used as the only protein source in this study. Fourteen piglets (7.98 ± 0.14 kg, weaned at 28 d) were randomly allotted to two dietary treatments: a control group (Cont, containing 17% casein) and a high protein group (HP, containing 30% casein). The experiment lasted for two weeks and all animals were free to eat and drink water ad libitum. The diarrhea score (1 = normal; 3 = watery diarrhea) and growth performance were recorded daily. The results showed that the piglets in HP group had persistent diarrhea during the whole study, while no diarrhea was noticed in the control groups. Also, the feed intake and body weights were reduced in the HP groups compared with the other group (P < 0.05). The diarrhea-related mRNA abundances were analyzed by real-time PCR; the results showed that HP treatment markedly decreased the expression of aquaporin (AQP, P < 0.05) and the tight junction protein (P<0.05), but increased inflammatory cytokines (P < 0.01) than those in control group. In addition, the Adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway (P < 0.01) was inhibited in the HP group. Intestinal microbiota was tested by 16S sequencing, and we found that the HP group had a low diversity compared the other group. In conclusion, despite being highly digestible, a high casein diet induced postweaning diarrhea and reduced the growth performance of the postweaning piglets. Meanwhile, AQP, tight junction protein, and intestinal immune were compromised. Thus, the mechanism of how a highly digestible protein diet induces diarrhea might be associated with the AMPK signaling pathway and intestinal microbiome.

Dynamic distribution of gut microbiota in meat rabbits at different growth stages and relationship with average daily gain (ADG)

Background

The mammalian intestinal tract harbors diverse and dynamic microbial communities that play pivotal roles in host health, metabolism, immunity, and development. Average daily gain (ADG) is an important growth trait in meat rabbit industry. The effects of gut microbiota on ADG in meat rabbits are still unknown.

Results

In this study, we investigated the dynamic distribution of gut microbiota in commercial Ira rabbits from weaning to finishing and uncover the relationship between the microbiota and average daily gain (ADG) via 16S rRNA gene sequencing. The results indicated that the richness and diversity of gut microbiota significantly increased with age. Gut microbial structure was less variable among finishing rabbits than among weaning rabbits. The relative abundances of the dominant phyla Firmicutes, Bacteroidetes, Verrucomicrobia and Cyanobacteria, and the 15 predominant genera significantly varied with age. Metagenomic prediction analysis showed that both KOs and KEGG pathways related to the metabolism of monosaccharides and vitamins were enriched in the weaning rabbits, while those related to the metabolism of amino acids and polysaccharides were more abundant in the finishing rabbits. We identified 34 OTUs, 125 KOs, and 25 KEGG pathways that were significantly associated with ADG. OTUs annotation suggested that butyrate producing bacteria belong to the family Ruminococcaceae and Bacteroidales_S24-7_group were positively associated with ADG. Conversely, Eubacterium_coprostanoligenes_group, Christensenellaceae_R-7_group, and opportunistic pathogens were negatively associated with ADG. Both KOs and KEGG pathways correlated with the metabolism of vitamins, basic amino acids, and short chain fatty acids (SCFAs) showed positive correlations with ADG, while those correlated with aromatic amino acids metabolism and immune response exhibited negative correlations with ADG. In addition, our results suggested that 10.42% of the variation in weaning weight could be explained by the gut microbiome.

Conclusions

Our findings give a glimpse into the dynamic shifts in gut microbiota of meat rabbits and provide a theoretical basis for gut microbiota modulation to improve ADG in the meat rabbit industry.