The search for the gene mutations underlying enterotoxigenic Escherichia coli F4ab/ac susceptibility in pigs: a review

A multi-AS-PCR-coupled CRISPR/Cas12a assay for the detection of ten single-base mutations

Single-nucleotide polymorphism (SNP) detection is critical for diagnosing diseases, and the development of rapid and accurate diagnostic tools is essential for treatment and prevention. Allele-specific polymerase chain reaction (AS-PCR) is widely used for detecting SNPs with multiplexing capabilities, while CRISPR-based technologies provide high sensitivity and specificity in targeting mutation sites through specific guide RNAs (gRNAs). In this study, we have integrated the high sensitivity and specificity of CRISPR technology with the multiplexing capabilities of AS-PCR, achieving the simultaneous detection of ten single-base mutations. As for Multi-AS-PCR, our research identified that competitive inhibition of primers targeting the same loci, coupled with divergent amplification efficiencies of these primers, could result in diminished amplification efficiency. Consequently, we adjusted and optimized primer combinations and ratios to enhance the amplification efficacy of Multi-AS-PCR. Finally, we successfully developed a novel nested Multi-AS-PCR-Cas12a method for multiplex SNPs detection. To evaluate the clinical utility of this method in a real-world setting, we applied it to diagnose rifampicin-resistant tuberculosis (TB). The limit of detection (LoD) for the nested Multi-AS-PCR-Cas12a was 102 aM, achieving sensitivity, specificity, positive predictive value, and negative predictive value of 100 %, 93.33 %, 90.00 %, and 100 %, respectively, compared to sequencing. In summary, by employing an innovative design that incorporates a universal reverse primer alongside ten distinct forward allele-specific primers, the nested Multi-AS-PCR-Cas12a technique facilitates the parallel detection of ten rpoB gene SNPs. This method also holds broad potential for the detection of drug-resistant gene mutations in infectious diseases and tumors, as well as for the screening of specific genetic disorders.

A Novel Multiepitope Fusion Antigen as a Vaccine Candidate for the Prevention of Enterotoxigenic E. coli-Induced Calf Diarrhea

Calf diarrhea caused by enterotoxigenic E. coli (ETEC) poses an enormous economic challenge in the cattle industry. Fimbriae and enterotoxin are crucial virulence factors and vaccine targets of ETEC. Since these proteins have complicated components with large molecular masses, the development of vaccines by directly expressing these potential targets is cumbersome Therefore, this study aimed to develop a multiepitope fusion antigen designated as MEFA by integrating major epitopes of FanC and Fim41a subunits and a toxoid epitope of STa into the F17G framework. The 3D modeling predicted that the MEFA protein displayed the epitopes from these four antigens on its surface, demonstrating the desired structural characteristics. Then, the MEFA protein was subsequently expressed and purified for mouse immunization. Following that, our homemade ELISA showed that the mouse antiserum had a consistent increase in polyclonal antibody levels with the highest titer of 1:217 to MEFA. Furthermore, the western blot assay demonstrated that this anti-MEFA serum could react with all four antigens. Further, this antiserum exhibited inhibition on ETEC adhesion to HCT-8 cells with inhibitory rates of 92.8%, 84.3%, and 87.9% against F17+, F5+, and F41+ ETEC strains, respectively. Additionally, the stimulatory effect of STa toxin on HCT-8 cells was decreased by approximately 75.3% by anti-MEFA serum. This study demonstrates that the MEFA protein would be an antigen candidate for novel subunit vaccines for preventing ETEC-induced diarrhea in cattle.

Survey on resistance occurrence for F4+ and F18+ enterotoxigenic Escherichia coli (ETEC) among pigs reared in Central Italy regions

Porcine Post Weaning Diarrhoea (PWD) is one of the most important swine disease worldwide, caused by Enterotoxigenic Escherichia coli (ETEC) strains able to provoke management, welfare and sanitary issues. ETEC is determined by proteinaceous surface appendages. Numerous studies conducted by now in pigs have demonstrated, at the enterocytes level, that, the genes mucin 4 (MUC4) and fucosyltransferase (FUT1), coding for ETEC F4 and F18 receptors respectively, can be carriers of single nucleotide polymorphisms (SNPs) associated with natural resistance/susceptibility to PWD. The latter aspect was investigated in this study, evaluating the SNPs of the MUC4 and FUT1 genes in slaughtered pigs reared for the most in Central Italy. Genomic DNA was extracted from 362 swine diaphragmatic samples and then was subjected to the detection of known polymorphisms on MUC4 and FUT1candidate target genes by PCR-RFLP. Some of the identified SNPs were confirmed by sequencing analysis. Animals carrying the SNPs associated with resistance were 11% and 86% for the FUT1 and MUC4 genes respectively. Therefore, it can be assumed that the investigated animals may be an important resource and reservoir of favorable genetic traits for the breeding of pigs resistant to enterotoxigenic E.coli F4 variant.

Effect of dietary tall oil fatty acids and hydrolysed yeast in SNP2-positive and SNP2-negative piglets challenged with F4 enterotoxigenic Escherichia coli

Reduction of post-weaning diarrhoea caused by ETEC is a principal objective in pig farming in terms of welfare benefits. This study determined the effects of genetic susceptibility and dietary strategies targeting inflammation and fimbriae adherence on F4-ETEC shedding and diarrhoea in weaned piglets in an experimental challenge model. A DNA marker test targeting single nucleotide polymorphism 2 (SNP2) identified piglets as heterozygous (SNP2+, susceptible) or homozygous (SNP2-, resistant) to developing F4ac-ETEC diarrhoea. A total of 50 piglets, 25 SNP2+ and 25 SNP2-, were weaned at 30 days of age and equally distributed to different treatments (n = 10): Positive control (PC): piglets fed with a negative control diet and provided with colistin via drinking water; Negative control (NC): piglets fed with a negative control diet; Tall oil fatty acids (TOFA): piglets fed with a negative control diet + 1.0 g TOFA/kg feed; Yeast hydrolysate (YH): piglets fed with a negative control diet + 1.5 g YH/kg feed derived from Saccharomyces cerevisiae; and Combination (COM): piglets fed with a negative control diet + 1.0 g TOFA and 1.5 g YH/kg feed. On day 10 post-weaning, all piglets were infected with F4-ETEC by oral administration. Piglets fed with PC, TOFA, YH or COM had a lower faecal shedding of F4-ETEC than NC piglets (P < 0.001), which was also shorter in duration for PC and TOFA piglets than for NC piglets (P < 0.001). Piglets in PC, TOFA, YH and COM had a shorter diarrhoea duration versus NC when classified as SNP2+ (P = 0.02). Furthermore, PC, TOFA and YH piglets grew more than NC and COM piglets in the initial post-inoculation period (P < 0.001). In addition, the level of faecal F4-ETEC shedding and the percentage of pigs that developed F4-ETEC diarrhoea (72 vs. 32%, P < 0.01) following infection were higher, and the duration of F4-ETEC diarrhoea longer (2.6 vs. 0.6 days, P < 0.001), in SNP2+ piglets than in SNP2- piglets, and led to reduced growth performance (P = 0.03). In conclusion, piglets fed with TOFA, YH or their combination, irrespective of their SNP2 status, are more resilient to F4-ETEC infection. Moreover, SNP2+ piglets show a higher level of F4-ETEC shedding and diarrhoea prevalence than SNP2- piglets, confirming an association between SNP2 and F4ac-ETEC susceptibility.

Identification of breed-specific genomic variants in Colombian Creole pig breeds by whole-genome sequencing

Dissecting genetic variation of local breeds is important for the success of conservation. In this research, we investigated the genomic variation of Colombian Creole (CR) pigs, with a focus on the breed-specific variants in the exonic region of 34 genes with reported effects on adaptive and economic traits. Seven individuals of each of the three CR breeds (CM, Casco de Mula; SP, San Pedreño; and ZU, Zungo) were whole-genome sequenced along with 7 Iberian (IB) pigs and 7 pigs of each of the four most used cosmopolitan (CP) breeds (Duroc, Landrace × Large White, and Pietrain). Molecular variability in CR (6,451,218 variants; from 3,919,242, in SP, to 4,648,069, in CM) was comparable to that in CP, but higher than in IB. For the investigated genes, SP pigs displayed less exonic variants (178) than ZU (254), CM (263), IB (200), and the individual CP genetic types (201 to 335). Sequence variation in these genes confirmed the resemblance of CR to IB and indicates that CR pigs, particularly ZU and CM, are not exempt from selective introgression of other breeds. A total of 50 exonic variants were identified as being potentially specific to CR, including a high-impact deletion in the intron between exons 15 and 16 of the leptin receptor gene, which was only found in CM and ZU. The identification of breed-specific variants in genes related to adaptive and economical traits can bolster the understanding of the role of gene-environment interactions on local adaptation and points the way for effective breeding and conservation of CR pigs.

A new human challenge model for testing heat-stable toxin-based vaccine candidates for enterotoxigenic Escherichia coli diarrhea - dose optimization, clinical outcomes, and CD4+ T cell responses

Enterotoxigenic Escherichia coli (ETEC) are a common cause of diarrheal illness in young children and travelers. There is yet no licensed broadly protective vaccine against ETEC. One promising vaccine development strategy is to target strains expressing the heat-stable toxin (ST), particularly the human ST (STh), since infections with these strains are among the leading causes of diarrhea in children in low-and-middle income countries. A human challenge model based on an STh-only ETEC strain will be useful to evaluate the protective efficacy of new ST-based vaccine candidates. To develop this model, we experimentally infected 21 healthy adult volunteers with the epidemiologically relevant STh-only ETEC strain TW10722, identified a suitable dose, assessed safety, and characterized clinical outcomes and immune responses caused by the infection. Doses of 1×10¹⁰ colony-forming units (CFU) of TW10722 gave a suitable attack risk of 67% for moderate or severe diarrhea and an overall diarrhea attack risk of 78%. Non-diarrheal symptoms were mostly mild or moderate, and there were no serious adverse events. During the first month after ingesting the challenge strain, we measured significant increases in both activated CD4+ T cells and levels of serum IgG and IgA antibodies targeting coli surface antigen 5 (CS5) and 6 (CS6), as well as the E. coli mucinase YghJ. The CS5-specific CD4+ T cell and antibody responses were still significantly elevated one year after experimental infection. In conclusion, we have developed a safe STh-only ETEC-based human challenge model which can be efficiently used in Phase 2B trials to evaluate the protective efficacy of new ST-based vaccine candidates.

Enterotoxigenic Escherichia coli (ETEC) is a common cause of diarrheal illness in young children living in low- and middle-income countries and in travelers to these countries. Several ETEC vaccine candidates are currently being developed, but so far, no broadly protective vaccines have been licensed. Since most moderate and severe ETEC diarrheal episodes are caused by strains that express the heat-stable enterotoxin (ST), ST represents a promising vaccine target. Here we present a human challenge model that can be used to estimate the protective efficacy of ST-based vaccine candidates in clinical vaccine trials. The model is based on the epidemiologically relevant ST-only ETEC strain TW10722, which we show is safe to ingest by volunteers and readily induce diarrhea.

Effect of mucin 4 allele on susceptibility to experimental infection with enterotoxigenic F4 Escherichia coli in pigs fed experimental diets

Background

This study investigated the validity of the DNA-marker based test to determine susceptibility to ETEC-F4 diarrhoea by comparing the results of two DNA sequencing techniques in weaner pigs following experimental infection with F4 enterotoxigenic Escherichia coli (ETEC-F4). The effects of diet and genetic susceptibility were assessed by measuring the incidence of piglet post-weaning diarrhoea (PWD), faecal E. coli shedding and the diarrhoea index.

Results

A DNA marker-based test targeting the mucin 4 gene (MUC4) that encodes F4 fimbria receptor identified pigs as either fully susceptible (SS), partially or mildly susceptible (SR), and resistant (RR) to developing ETEC-F4 diarrhoea. To further analyse this, DNA sequencing was undertaken, and a significantly higher proportion of C nucleotides was observed for RR and SR at the XbaI cleavage site genotypes when compared to SS. However, no significant difference was found between SR and RR genotypes. Therefore, results obtained from Sanger sequencing retrospectively allocated pigs into a resistant genotype (MUC4–), in the case of a C nucleotide, and a susceptible genotype (MUC4+), in the case of a G nucleotide, at the single nucleotide polymorphism site. A total of 72 weaner pigs (age ~ 21 days), weighing 6.1 ± 1.2 kg (mean ± SEM), were fed 3 different diets: (i) positive control (PC) group supplemented with 3 g/kg zinc oxide (ZnO), (ii) negative control (NC) group (no ZnO or HAMSA), and (iii) a diet containing a 50 g/kg high-amylose maize starch product (HAMSA) esterified with acetate. At days five and six after weaning, all pigs were orally infected with ETEC (serotype O149:F4; toxins LT1, ST1, ST2 and EAST). The percentage of pigs that developed diarrhoea following infection was higher (P = 0.05) in MUC4+ pigs compared to MUC4– pigs (50% vs. 26.8%, respectively). Furthermore, pigs fed ZnO had less ETEC-F4 diarrhoea (P = 0.009) than pigs fed other diets, however faecal shedding of ETEC was similar (P > 0.05) between diets.

Conclusion

These results confirm that MUC4+ pigs have a higher prevalence of ETEC-F4 diarrhoea following exposure, and that pigs fed ZnO, irrespective of MUC4 status, have reduced ETEC-F4 diarrhoea. Additionally, sequencing or quantifying the single nucleotide polymorphism distribution at the XbaI cleavage site may be more reliable in identifying genotypic susceptibility when compared to traditional methods.

Resistance to ETEC F4/F18-mediated piglet diarrhoea: opening the gene black box

Diarrhoea, a significant problem in pig rearing industry affecting pre- and post-weaning piglets is caused by enterotoxigenic Escherichia coli (ETEC). The ETEC are classified as per the fimbriae types which are responsible for bacterial attachment with enterocytes and release of toxins causing diarrhoea. However, genetic difference exists for susceptibility to ETEC infection in piglets. The different phenotypes found in pigs determine their (pigs') susceptibility or resistance towards fimbrial subtypes/variants (F4ab, F4ac, F4ad and F18). Specific receptors are present on intestinal epithelium for attachment of these fimbriae, which do not express to same level in all animals. This differential expression is genetically determined and thus their genetic causes (may be putative candidate gene or mutations) render some animals resistant or susceptible to one or more fimbrial subtypes. Genetic linkage studies have revealed the mapping location of the receptor loci for the two most frequent variants F4ab and F4ac to SSC13q41 (i.e. q arm of 13th chromosome of Sus scrofa). Some SNPs have been identified in mucin gene family, transferring receptor gene, fucosyltransferase 1 gene and swine leucocyte antigen locus that are proposed to be linked mutations for resistance/susceptibility towards ETEC diarrhoea. However, owing to the variety of fimbrial types and subtypes, it would be difficult to identify a single causative mutation and the candidate loci may involve more number of genes/regions. In this review, we focus on the genetic mutations in genes involved in imparting resistance/susceptibility to F4 or F18 ETEC diarrhoea and possibilities to use them as marker for selection against susceptible animals.

Piglet gut microbial shifts early in life: causes and effects

The gut microbiome has long been known to play fundamentally important roles in the animal health and the well-being of its host. As such, the establishment and maintenance of a beneficial gut microbiota early in life is crucial in pigs, since early gut colonizers are pivotal in the establishment of permanent microbial community structures affecting the health and growth performance of pigs later in life. Emphasizing this importance of early gut colonizers, it is critical to understand the factors impacting the establishment of the piglet gut microbiome at weaning. Factors include, among others, diet, in-feed antibiotics, probiotics and prebiotic administration. The impact of these factors on establishment of the gut microbiome of piglets at weaning includes effects on piglet gut microbial diversity, structure, and succession. In this review, we thoroughly reviewed the most recent findings on the piglet gut microbiome shifts as influenced by weaning, and how these microbiome changes brought about by various factors that have been shown to affect the development of microbiota in piglets. This review will provide a general overview of recent studies that can help to facilitate the design of new strategies to modulate the gut microbiome in order to enhance gastrointestinal health, growth performance and well-being of piglets.

Diversity across major and candidate genes in European local pig breeds

The aim of this work was to analyse the distribution of causal and candidate mutations associated to relevant productive traits in twenty local European pig breeds. Also, the potential of the SNP panel employed for elucidating the genetic structure and relationships among breeds was evaluated. Most relevant genes and mutations associated with pig morphological, productive, meat quality, reproductive and disease resistance traits were prioritized and analyzed in a maximum of 47 blood samples from each of the breeds (Alentejana, Apulo-Calabrese, Basque, Bísara, Majorcan Black, Black Slavonian (Crna slavonska), Casertana, Cinta Senese, Gascon, Iberian, Krškopolje (Krškopoljski), Lithuanian indigenous wattle, Lithuanian White Old Type, Mora Romagnola, Moravka, Nero Siciliano, Sarda, Schwäbisch-Hällisches Schwein (Swabian Hall pig), Swallow-Bellied Mangalitsa and Turopolje). We successfully analyzed allelic variation in 39 polymorphisms, located in 33 candidate genes. Results provide relevant information regarding genetic diversity and segregation of SNPs associated to production and quality traits. Coat color and morphological trait-genes that show low level of segregation, and fixed SNPs may be useful for traceability. On the other hand, we detected SNPs which may be useful for association studies as well as breeding programs. For instance, we observed predominance of alleles that might be unfavorable for disease resistance and boar taint in most breeds and segregation of many alleles involved in meat quality, fatness and growth traits. Overall, these findings provide a detailed catalogue of segregating candidate SNPs in 20 European local pig breeds that may be useful for traceability purposes, for association studies and for breeding schemes. Population genetic analyses based on these candidate genes are able to uncover some clues regarding the hidden genetic substructure of these populations, as the extreme genetic closeness between Iberian and Alentejana breeds and an uneven admixture of the breeds studied. The results are in agreement with available knowledge regarding breed history and management, although largest panels of neutral markers should be employed to get a deeper understanding of the population's structure and relationships.

Differential expression of intestinal ion transporters and water channel aquaporins in young piglets challenged with enterotoxigenic Escherichia coli K88

The study was to determine whether the expression of genes involved in intestinal water and ion transport would be affected by enterotoxigenic (ETEC) K88 both in vitro and in vivo. First, 36 male piglets (4 d old) were randomly allotted to either the control or the ETEC K88 group. Each group had 6 replicates with 3 piglets per replicate. All piglets were fed with the same diets for 17 d. On d 15, piglets in the ETEC K88 group were challenged with ETEC K88 (serotype O149:K91:K88ac) at 1 × 10 cfu per pig, whereas those in the control group received the same volume of sterile PBS. After being challenged with ETEC K88 for 72 h (d 18), 1 piglet from each replicate was selected for slaughter to collect samples from the jejunum, ileum, and colon. The mRNA expression and protein abundance of cystic fibrosis transmembrane conductance regulator (CFTR) in the ileum and colon were increased compared with that in the control group ( < 0.05). Furthermore, the mRNA expression of () in the ileum and colon was increased by ETEC K88 challenge ( < 0.05), whereas in the jejunum, both its mRNA and protein expression were increased by ETEC K88 treatment ( < 0.05). Additionally, an established porcine intestinal epithelial cell line (IPEC-J2) was used to investigate the effect and possible mechanism of ETEC K88 on expression of water channel aquaporins (AQP) and ion transporters. Cells (1.17 × 10 per well) were grown in 6-well plates and treated with ETEC K88 at a multiplicity of infection of 50:1 for 3 h. The mRNA expression of , , and () in IPEC-J2 cells was reduced after ETEC K88 treatment ( < 0.05). Further analyses using western blotting also demonstrated that ETEC K88 decreased the protein expression of AQP3, AQP9, and AQP11 in IPEC-J2 cells ( < 0.05). Moreover, the phosphorylation levels of protein kinase A (PKA) and cyclic adenosine monophosphate (cAMP)-response element binding protein (CREB) were decreased by ETEC K88 challenge ( < 0.05). The results indicate that ETEC K88 challenge induced differential expression of intestinal ion transporters and AQP in young piglets, probably by regulation of the cAMP-PKA signaling pathway. This study might provide new insights about the importance of fluid homeostasis in control of ETEC-induced diarrhea in young piglets.

Genetic Susceptibility to Postdiarrheal Hemolytic-Uremic Syndrome After Shiga Toxin-Producing Escherichia coli Infection: A Centers for Disease Control and Prevention FoodNet Study

Background

Postdiarrheal hemolytic-uremic syndrome (D+HUS) following Shiga toxin-producing Escherichia coli (STEC) infection is a serious condition lacking specific treatment. Host immune dysregulation and genetic susceptibility to complement hyperactivation are implicated in non-STEC-related HUS. However, genetic susceptibility to D+HUS remains largely uncharacterized.

Methods

Patients with culture-confirmed STEC diarrhea, identified through the Centers for Disease Control and Prevention FoodNet surveillance system (2007-2012), were serotyped and classified by laboratory and/or clinical criteria as having suspected, probable, or confirmed D+HUS or as controls and underwent genotyping at 200 loci linked to nondiarrheal HUS or similar pathologies. Genetic associations with D+HUS were explored by multivariable regression, with adjustment for known risk factors.

Results

Of 641 enrollees with STEC O157:H7, 80 had suspected D+HUS (41 with probable and 32 with confirmed D+HUS). Twelve genes related to cytokine signaling, complement pathways, platelet function, pathogen recognition, iron transport, and endothelial function were associated with D+HUS in multivariable-adjusted analyses (P ≤ .05). Of 12 significant single-nucleotide polymorphisms (SNPs), 5 were associated with all levels of D+HUS (intergenic SNP rs10874639, TFRC rs3804141, EDN1 rs5370, GP1BA rs121908064, and B2M rs16966334), and 7 SNPs (6 non-complement related) were associated with confirmed D+HUS (all P < .05).

Conclusions

Polymorphisms in many non-complement-related genes may contribute to D+HUS susceptibility. These results require replication, but they suggest novel therapeutic targets in patients with D+HUS.

Post weaning diarrhea in pigs: risk factors and non-colistin-based control strategies

Post-weaning diarrhea (PWD) is one of the most serious threats for the swine industry worldwide. It is commonly associated with the proliferation of enterotoxigenic Escherichia coli in the pig intestine. Colistin, a cationic antibiotic, is widely used in swine for the oral treatment of intestinal infections caused by E. coli, and particularly of PWD. However, despite the effectiveness of this antibiotic in the treatment of PWD, several studies have reported high rates of colistin resistant E. coli in swine. Furthermore, this antibiotic is considered of very high importance in humans, being used for the treatment of infections due to multidrug-resistant (MDR) Gram-negative bacteria (GNB). Moreover, the recent discovery of the mcr-1 gene encoding for colistin resistance in Enterobacteriaceae on a conjugative stable plasmid has raised great concern about the possible loss of colistin effectiveness for the treatment of MDR-GNB in humans. Consequently, it has been proposed that the use of colistin in animal production should be considered as a last resort treatment only. Thus, to overcome the economic losses, which would result from the restriction of use of colistin, especially for prophylactic purposes in PWD control, we believe that an understanding of the factors contributing to the development of this disease and the putting in place of practical alternative strategies for the control of PWD in swine is crucial. Such alternatives should improve animal gut health and reduce economic losses in pigs without promoting bacterial resistance. The present review begins with an overview of risk factors of PWD and an update of colistin use in PWD control worldwide in terms of quantities and microbiological outcomes. Subsequently, alternative strategies to the use of colistin for the control of this disease are described and discussed. Finally, a practical approach for the control of PWD in its various phases is proposed.

The Importance of Endophenotypes to Evaluate the Relationship between Genotype and External Phenotype

With the exception of a few Mendelian traits, almost all phenotypes (traits) in livestock science are quantitative or complex traits regulated by the expression of many genes. For most of the complex traits, differential expression of genes, rather than genomic variation in the gene coding sequences, is associated with the genotype of a trait. The expression profiles of the animal's transcriptome, proteome and metabolome represent endophenotypes that influence/regulate the externally-observed phenotype. These expression profiles are generated by interactions between the animal's genome and its environment that range from the cellular, up to the husbandry environment. Thus, understanding complex traits requires knowledge about not only genomic variation, but also environmental effects that affect genome expression. Gene products act together in physiological pathways and interaction networks (of pathways). Due to the lack of annotation of the functional genome and ontologies of genes, our knowledge about the various biological systems that contribute to the development of external phenotypes is sparse. Furthermore, interaction with the animals' microbiome, especially in the gut, greatly influences the external phenotype. We conclude that a detailed understanding of complex traits requires not only understanding of variation in the genome, but also its expression at all functional levels.

Oral Administration of a Select Mixture of Bacillus Probiotics Affects the Gut Microbiota and Goblet Cell Function following Escherichia coli Challenge in Newly Weaned Pigs of Genotype MUC4 That Are Supposed To Be Enterotoxigenic E. coli F4ab/ac Receptor Negative

Structural disruption of the gut microbiota and impaired goblet cell function are collateral etiologic factors in enteric diseases. Low, moderate, or high doses of a Bacillus licheniformis-B. subtilis mixture (BLS mix) were orally administered to piglets of genotype MUC4 that are supposed to be F4-expressing enterotoxigenic Escherichia coli strain (F4⁺ ETEC) F4ab/ac receptor negative (i.e., MUC4-resistant piglets) for 1 week before F4⁺ ETEC challenge. The luminal contents were collected from the mucosa of the colon on day 8 after F4⁺ ETEC challenge. The BLS mix attenuated E. coli-induced expansion of Bacteroides uniformis, Eubacterium eligens, Acetanaerobacterium, and Sporobacter populations. Clostridium and Turicibacter populations increased following F4⁺ ETEC challenge in pigs pretreated with low-dose BLS mix. Lactobacillus gasseri and Lactobacillus salivarius populations increased after administration of BLS mix during E. coli infection. The beneficial effects of BLS mix were due in part to the expansion of certain Clostridium, Lactobacillus, and Turicibacter populations, with a corresponding increase in the number of goblet cells in the ileum via upregulated Atoh1 expression, in turn increasing MUC2 production and thus preserving the mucus barrier and enhancing host defenses against enteropathogenic bacteria. However, excessive BLS mix consumption may increase the risk for enteritis, partly through disruption of colonic microbial ecology, characterized by expansion of Proteobacteria and impaired goblet cell function in the ileum. Our findings suggest that oral administration of BLS mix reprograms the gut microbiota and enhances goblet cell function to ameliorate enteritis.

IMPORTANCE

The present study is important for improving our understanding of the protective role of probiotics against Escherichia coli infection in piglets. Structural disruption of the gut microbiota and impaired goblet cell function are collateral etiologic factors in enteric diseases. In this study, low, moderate, or high doses of a Bacillus licheniformis-B. subtilis mixture (BLS mix) were orally administered to MUC4-resistant piglets for 1 week before the F4-expressing ETEC strain (F4⁺ ETEC) challenge. Our findings suggest that oral administration of BLS mix reprograms the gut microbiota and enhances goblet cell function to ameliorate enteritis.

New perspectives to the enterotoxigenic E. coli F4 porcine infection model: Susceptibility genotypes in relation to performance, diarrhoea and bacterial shedding

Enterotoxigenic E. coli (ETEC), causing post-weaning diarrhoea, is a major problem in weaned piglets. Individual animal responses to ETEC infection show high variability in animal experiments. Two studies were designed to optimize the ETEC F4ac infection model in piglets by combining the genotype susceptibility with performance, diarrhoea incidence and bacterial shedding. The studies were performed with respectively 120 and 80 male piglets that were tested for susceptibility or resistance towards ETEC O149:F4ac by a DNA marker based test. Three different genotypes were observed; resistant (RR), susceptible heterozygote (RS) and susceptible homozygote (SS). Piglets, were orally infected with an inoculum suspension (containing 1.5E8 CFU/ml ETEC F4ac) at day 0, 1 and 2 of the study. Performance, diarrhoea incidence and bacterial shedding were followed for 21days. In the first week after challenge a difference in average daily gain was observed between resistant and susceptible piglets in both studies. For the complete study period no significant differences were observed. Diarrhoea incidence was significantly higher in susceptible pigs compared to the resistant pigs in the first week after challenge. Bacterial shedding was much higher in the susceptible pigs and ETEC excretion lasted longer. ETEC was hardly detected in the faecal material of the resistant pigs. In conclusion, susceptible pigs showed higher diarrhoea incidence and higher numbers of faecal ETEC shedding in the first week after challenge compared to resistant pigs. The DNA marker based test can be used to select pigs that are susceptible for ETEC for inclusion in ETEC infection model, resulting in less animals needed to perform infection studies.

Efficient SNP Discovery by Combining Microarray and Lab-on-a-Chip Data for Animal Breeding and Selection

The genetic markers associated with economic traits have been widely explored for animal breeding. Among these markers, single-nucleotide polymorphism (SNPs) are gradually becoming a prevalent and effective evaluation tool. Since SNPs only focus on the genetic sequences of interest, it thereby reduces the evaluation time and cost. Compared to traditional approaches, SNP genotyping techniques incorporate informative genetic background, improve the breeding prediction accuracy and acquiesce breeding quality on the farm. This article therefore reviews the typical procedures of animal breeding using SNPs and the current status of related techniques. The associated SNP information and genotyping techniques, including microarray and Lab-on-a-Chip based platforms, along with their potential are highlighted. Examples in pig and poultry with different SNP loci linked to high economic trait values are given. The recommendations for utilizing SNP genotyping in nimal breeding are summarized.

Oral administration of a select mixture of Bacillus probiotics generates Tr1 cells in weaned F4ab/acR- pigs challenged with an F4+ ETEC/VTEC/EPEC strain

Although breeding of F4 receptor − negative (F4R⁻) pigs may prevent post-weaning diarrhea, the underlying immunity is poorly understood. Here, various doses of a Bacillus licheniformis and Bacillus subtilis mixture (BLS-mix) were orally administered to F4ab/acR⁻ pigs for 1 week before F4 (K88) − positive ETEC/VTEC/EPEC challenge. Administration of BLS-mix increased the percentage of Foxp3⁻IL-10⁺ T cells but not of Foxp3⁺IL-10⁺ regulatory T (Treg) cells among peripheral blood CD4⁺ T cells. A low dose of BLS-mix feeding resulted in increased the expression of IL-6, TNF-α, IL-10, and the transcription factors Foxp3 and T-bet mRNAs in the jejunum. Administration of either a low or high dose BLS-mix also led to an increase in the percentage of CD4⁺Foxp3⁺ Treg cells among intraepithelial lymphocytes and CD4⁺IL-10⁺ T cells in the small intestinal Peyer’s patches and the lamina propria of F4ab/acR⁻ pigs following F4⁺ ETEC/VTEC/EPEC challenge. The increased number of IL-10–producing CD4⁺ T cells was attributed to an increase in the proportion of Foxp3⁻IL-10⁺ Treg cells rather than Foxp3⁺IL-10⁺ Treg cells. Our data indicate that oral administration of BLS-mix to newly weaned F4ab/acR⁻ pigs ameliorates enteritis in an F4⁺ ETEC/VTEC/EPEC model; however, induction of IL-10–producing Foxp3⁻ Treg cells by BLS-mix administration cannot account for the protection of newly weaned F4ab/acR⁻ pigs from F4⁺ ETEC/VTEC/EPEC infection, and that excessive generation of CD4⁺IL-10⁺ T cells following consumption of BLS-mix during episodes of intestinal inflammation that is caused by enteric pathogens might prohibit clearance of the pathogen. Select probiotic mixtures may allow for tailoring strategies to prevent infectious diseases.

Receptor for the F4 fimbriae of enterotoxigenic Escherichia coli (ETEC)

Infection with F4(+) enterotoxigenic Escherichia coli (ETEC) responsible for diarrhea in neonatal and post-weaned piglets leads to great economic losses in the swine industry. These pathogenic bacteria express either of three fimbrial variants F4ab, F4ac, and F4ad, which have long been known for their importance in host infection and initiating protective immune responses. The initial step in infection for the bacterium is to adhere to host enterocytes through fimbriae-mediated recognition of receptors on the host cell surface. A number of receptors for ETEC F4 have now been described and characterized, but their functions are still poorly understood. The current review summarizes the latest research addressing the characteristics of F4 fimbriae receptors and the interactions of F4 fimbriae and their receptors on host cells. These include observations that as follows: (1) FaeG mediates the binding activities of F4 and is an essential component of the F4 fimbriae, (2) the F4 fimbrial receptor gene is located in a region of chromosome 13, (3) the biochemical properties of F4 fimbrial receptors that form the binding site of the bacterium are now recognized, and (4) specific receptors confer susceptibility/resistance to ETEC F4 infection in pigs. Characterizing the host-pathogen interaction will be crucial to understand the pathogenicity of the bacteria, provide insights into receptor activation of the innate immune system, and develop therapeutic strategies to prevent this illness.

Variation in 12 porcine genes involved in the carbohydrate moiety assembly of glycosphingolipids does not account for differential binding of F4 Escherichia coli and their fimbriae

Background

Glycosphingolipids (GSLs) are important membrane components composed of a carbohydrate structure attached to a hydrophobic ceramide. They can serve as specific membrane receptors for microbes and microbial products, such as F4 Escherichia coli (F4 ETEC) and isolated F4 fimbriae. The aim of this study was to investigate the hypothesis that variation in genes involved in the assembly of the F4 binding carbohydrate moiety of GSLs (i.e. ARSA, B4GALT6, GAL3ST1, GALC, GBA, GLA, GLB1, GLB1L, NEU1, NEU2, UGCG, UGT8) could account for differential binding of F4 ETEC and their fimbriae.

Results

RT-PCR could not reveal any differential expression of the 12 genes in the jejunum of F4 receptor-positive (F4R⁺) and F4 receptor-negative (F4R^-) pigs. Sequencing the complete open reading frame of the 11 expressed genes (NEU2 was not expressed) identified 72 mutations. Although some of them might have a structural effect, none of them could be associated with a F4R phenotype.

Conclusion

We conclude that no regulatory or structural variation in any of the investigated genes is responsible for the genetic susceptibility of pigs towards F4 ETEC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-014-0103-x) contains supplementary material, which is available to authorized users.

Refined candidate region for F4ab/ac enterotoxigenic Escherichia coli susceptibility situated proximal to MUC13 in pigs

F4 enterotoxigenic Escherichia coli (F4 ETEC) are an important cause of diarrhea in neonatal and newly-weaned pigs. Based on the predicted differential O-glycosylation patterns of the 2 MUC13 variants (MUC13A and MUC13B) in F4ac ETEC susceptible and F4ac ETEC resistant pigs, the MUC13 gene was recently proposed as the causal gene for F4ac ETEC susceptibility. Because the absence of MUC13 on Western blot from brush border membrane vesicles of F4ab/acR⁺ pigs and the absence of F4ac attachment to immunoprecipitated MUC13 could not support this hypothesis, a new GWAS study was performed using 52 non-adhesive and 68 strong adhesive pigs for F4ab/ac ETEC originating from 5 Belgian farms. A refined candidate region (chr13: 144,810,100–144,993,222) for F4ab/ac ETEC susceptibility was identified with MUC13 adjacent to the distal part of the region. This candidate region lacks annotated genes and contains a sequence gap based on the sequence of the porcine GenomeBuild 10.2. We hypothesize that a porcine orphan gene or trans-acting element present in the identified candidate region has an effect on the glycosylation of F4 binding proteins and therefore determines the F4ab/ac ETEC susceptibility in pigs.

Diversity of interferon inducible Mx gene in horses and association of variations with susceptibility vis-à-vis resistance against equine influenza infection

Equine influenza (EI) is primarily an infection of the upper respiratory tract and is one of the major infectious respiratory diseases of economic importance in equines. Re-emergence of the disease, species jumping by H3N8 virus in canines and possible threat of human pandemic due to the unpredictable nature of the virus have necessitated research on devising strategies for preventing the disease. The myxovirus resistance protein (Mx) has been reported to confer resistance to Orthomyxo virus infection by modifying cellular functions needed along the viral replication pathway. Polymorphisms and differential antiviral activities of Mx gene have been reported in pigs and chicken. Here we report the diversity of Mx gene, its expression in response to stimulation with interferon (IFN) α/β and their association with EI resistance and susceptibility in Marwari horses. Blood samples were collected from horses declared positive for equine influenza and in contact animals with a history of no clinical signs. Mx gene was amplified by reverse transcription from total RNA isolated from peripheral blood mononuclear cells (PBMCs) stimulated with IFN α/β using gene specific primers. The amplified gene products from representative samples were cloned and sequenced. Nucleotide sequences and deduced amino acid sequences were analyzed. Out of a total 24 amino acids substitutions sorting intolerant from tolerant (SIFT) analysis predicted 13 substitutions with functional consequences. Five substitutions (V67A, W123L, E346Y, N347Y, S689N) were observed only in resistant animals. Evolutionary distances based on nucleotide sequences with in equines ranged between 0.3-2.0% and 20-24% with other species. On phylogenetic analysis all equine sequences clustered together while other species formed separate clades.

Inheritance of porcine receptors for enterotoxigenic Escherichia coli with fimbriae F4ad and their relation to other F4 receptors

Enteric Escherichia coli infections are a highly relevant cause of disease and death in young pigs. Breeding genetically resistant pigs is an economical and sustainable method of prevention. Resistant pigs are protected against colonization of the intestine through the absence of receptors for the bacterial fimbriae, which mediate adhesion to the intestinal surface. The present work aimed at elucidation of the mode of inheritance of the F4ad receptor which according to former investigations appeared quite confusing. Intestines of 489 pigs of an experimental herd were examined by a microscopic adhesion test modified in such a manner that four small intestinal sites instead of one were tested for adhesion of the fimbrial variant F4ad. Segregation analysis revealed that the mixed inheritance model explained our data best. The heritability of the F4ad phenotype was estimated to be 0.7±0.1. There are no relations to the strong receptors for variants F4ab and F4ac. Targeted matings allowed the discrimination between two F4ad receptors, that is, a fully adhesive receptor (F4adRFA) expressed on all enterocytes and at all small intestinal sites, and a partially adhesive receptor (F4adRPA) variably expressed at different sites and often leading to partial bacterial adhesion. In pigs with both F4ad receptors, the F4adRPA receptor is masked by the F4adRFA. The hypothesis that F4adRFA must be encoded by at least two complementary or epistatic dominant genes is supported by the Hardy-Weinberg equilibrium statistics. The F4adRPA receptor is inherited as a monogenetic dominant trait. A comparable partially adhesive receptor for variant F4ab (F4abRPA) was also observed but the limited data did not allow a prediction of the mode of inheritance. Pigs were therefore classified into one of eight receptor phenotypes: A1 (F4abRFA/F4acR+/F4adRFA); A2 (F4abRFA/F4acR+/F4adRPA); B (F4abRFA/F4acR+/F4adR-); C1 (F4abRPA/F4acR-/F4adRFA); C2 (F4abRPA/F4acR-/F4adRPA); D1 (F4abR-/F4acR-/F4adRFA); D2 (F4abR-/F4acR-/F4adRPA); E (F4abR-/F4acR-/F4adR-).

F4-related mutation and expression analysis of the aminopeptidase N gene in pigs

Intestinal infections with F4 enterotoxigenic Escherichia coli (ETEC) are worldwide an important cause of diarrhea in neonatal and recently weaned pigs. Adherence of F4 ETEC to the small intestine by binding to specific receptors is mediated by F4 fimbriae. Porcine aminopeptidase N (ANPEP) was recently identified as a new F4 receptor. In this study, 7 coding mutations and 1 mutation in the 3′ untranslated region (3' UTR)were identified in ANPEP by reverse transcriptase (RT–) PCR and sequencing using 3 F4 receptor-positive (F4R+) and 2 F4 receptor-negative (F4R–) pigs, which were F4 phenotyped based on the MUC4 TaqMan, oral immunization, and the in vitro villous adhesion assay. Three potential differential mutations (g.2615C > T, g.8214A > G, and g.16875C > G) identified by comparative analysis between the 3 F4R+ and 2 F4R– pigs were genotyped in 41 additional F4 phenotyped pigs. However, none of these 3 mutations could be associated with F4 ETEC susceptibility. In addition, the RT-PCR experiments did not reveal any differential expression or alternative splicing in the small intestine of F4R+ and F4R– pigs. In conclusion, we hypothesize that the difference in F4 binding to ANPEP is due to modifications in its carbohydrate moieties.