Trypanosoma equiperdum in the horse – a neglected threat?

Dourine is a contagious disease caused by Trypanosoma equiperdum that is transmitted directly from animal to animal during coitus. Dourine is known as an important disease in many countries, and it threatens equidae worldwide. It is reported to be widespread in South America, Eastern Europe, Russia, Mongolia, Namibia and Ethiopia. The disease can be carried to various parts of the world through the transportation of infected animals and semen. Since knowledge of the prepatent infectiousness of a recently infected animal is lacking, introduction of the disease is in principle an ever-present threat. Definitive diagnosis depends on the identification of the parasite by means of direct microscopy. This is rarely possible in practice and therefore, diagnosis in the field is based on the observation of typical clinical signs, together with serological tests. This paper is an endeavour to review briefly and compile information on the appearance and importance of Dourine in terms of its epidemiological and clinical features, as well as on its diagnosis, treatment and prognosis.

Effect of β-hydroxybutyric acid, parity, and body condition score on phenotype and proliferative capacity of colostral mononuclear leukocytes of high-yielding dairy cows

In neonatal calves, the ingestion of colostrum is imperative for preventing infectious diseases. Investigations into the transfer of passive immunity of cattle have primarily focused on the importance of colostral immunoglobulins, with a recent increase in focus on understanding the role of colostral leukocytes. The main objective of the present study was to measure the influence of parity, body condition score, serum nonesterified fatty acids, and serum β-hydroxybutyrate concentrations of periparturient cows on phenotype and mitogen- and antigen-induced proliferative capacity of bovine colostral leukocytes. Holstein-Friesian cows (n=141) were intramuscularly vaccinated at 60 and 30 d before the expected parturition date with a tetanus toxoid vaccine. Of these 141 animals, 28 primiparous and 72 multiparous cows were sampled immediately after parturition. Colostrum mononuclear cell populations were identified by flow cytometry using bovine cluster of differentiation markers, and the proliferative capacity of these cells was determined using a (3)H-thymidine proliferation assay. Under-conditioned cows had a significantly higher percentage of colostral macrophages than normal-conditioned animals, whereas over-conditioned cows had significantly more colostral B-lymphocytes. Serum β-hydroxybutyrate was significantly associated with higher numbers of colostral T-lymphocytes and macrophages. Heifers had significantly higher mitogen- and antigen-induced proliferation of their colostral leukocytes than third parity or older cows. In conclusion, body condition score, parity, and serum β-hydroxybutyrate concentration of periparturient high-yielding dairy cows were shown to influence the number of colostral macrophages or the mitogen- and antigen-induced proliferation of colostral leukocytes, possibly influencing the cellular immunity of the newborn calf.

Analysis of the mucosal immune responses induced by single and trickle infections with the bovine abomasal nematode Ostertagia ostertagi

The purpose of this study was to provide more information on the kinetics of the immunological changes occurring in the abomasal mucosa after single and trickle infections with the bovine parasite Ostertagia ostertagi. The time course analysis of gene expression revealed that the major changes coincided with the emergence of adult worms from the gastric glands. These changes consisted of a simultaneous upregulation of Th1- and Th2-type cytokines. In addition, a single O. ostertagi infection elicited an upregulation of the epithelial-derived cytokine IL33, while TSLP expression levels were not impacted. Apart from the massive increase in inflammatory cytokines IL6, IL17 and IL21, O. ostertagi infection also elicited an upregulation of the immunosuppressors TGFB, IL10 and ARG1, as well as NK and γδ-T cell markers. Furthermore, the cytotoxic factors granulysin, perforin and granzyme B were upregulated following an O. ostertagi infection. Analysis of cytokine transcript levels in animals receiving trickle infections for 60 days showed a similar trend as observed following a single infection except for IL33, IL6, GATA-3, TBX21 and NCR1, which were no longer upregulated after trickle infections. Finally, the long trickle infections were associated with mucosal eosinophilia and mastocytosis.

Evaluation of an IgE ELISA with Culicoides spp. extracts and recombinant salivary antigens for diagnosis of insect bite hypersensitivity in Warmblood horses

Insect bite hypersensitivity (IBH) in horses represents an immunoglobulin E (IgE)-mediated hypersensitivity to salivary antigens from biting midges (Culicoides spp.). The aim of this study was to evaluate and compare the performances of IgE ELISAs using recombinant Culicoides spp. Obsoletus group salivary gland antigens or crude whole body extracts ('ObsWBE'), C. nubeculosus recombinant proteins (Culn1, 3, 4, 5, 7, 8 and 10) and Obsoletus group recombinant proteins (Culo1 and 2). IgE levels were measured in plasma of 343 Warmblood horses classified as IBH-affected (n=167) and IBH-unaffected (n=176) according to the owners' descriptions. IBH-affected horses were subdivided based on the severity of their clinical signs at sampling and whether or not their IBH history was considered to be classical. The accuracies of the tests increased when clinical signs at sampling were more pronounced or when the IBH history could be considered as classical. A combination of IgE levels against the three best performing Culicoides spp. recombinant proteins (Culn4, Culo1 and Culo2) and ObsWBE resulted in the best performing test. When IBH-affected horses showing a classical history of the disease and severe clinical signs were compared with IBH-unaffected horses, the Youden's index at the optimal cut-off for the three tests in combination was 0.67. This optimal cut-off had a sensitivity of 70%, a specificity of 97% and a total accuracy of 92%. The performance of the IgE ELISA was affected by the severity of IBH clinical signs at sampling and was improved when IgE levels against several recombinant proteins were combined.

Effect of a disinfection strategy on the methicillin-resistant Staphylococcus aureus CC398 prevalence of sows, their piglets and the barn environment

AIMS

To assess, in a cleaned and disinfected barn environment, the efficacy of an animal disinfection strategy to reduce the livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) prevalence in sows, their offspring and the barn environment.

METHODS AND RESULTS

On each farm, six sow rounds were sampled; sows were divided into either a test or control group. Per round, 20 sows and 40 of their piglets were sampled at different time points together with the barn environment. The disinfection strategy of the test groups consisted of washing the sows with a shampoo followed by disinfection of the skin with a solution containing chlorhexidine digluconate and isopropanol. On the first day of disinfection and 6 days after stopping the disinfection, a significant decrease (P < 0·01) of on average 68 and 66% in sow MRSA prevalence was observed on both farms, whereas no decrease was seen in the control groups. Just before weaning, 21-28 days after the end of the disinfection strategy, the difference in MRSA prevalence between both groups was reduced to 4% and no longer significant (P = 0·20). The MRSA prevalence of the piglets in the test groups was significantly lower (26%; P < 0·01) 6 days after the end of disinfection. Just before weaning, this difference was reduced to 5% but still significant (P < 0·01). In the swine nursery unit, no significant difference (P = 0·99) was seen between both groups. Based on semi-quantitative counts, a relationship (r(2)  > 0·6; P < 0·01) was seen between MRSA contamination in the barn environment and the MRSA prevalence in pigs.

CONCLUSION

Results show that the tested disinfection strategy reduces temporarily the sow and piglet MRSA status, but does not result in a final reduction in MRSA at weaning or in the nursery unit.

SIGNIFICANCE AND IMPACT OF THE STUDY

First report on the efficacy of an animal disinfection strategy to reduce LA-MRSA prevalence in sows, their offspring and the barn environment.

Evaluation of different chromogenic media for the detection of methicillin-resistant Staphylococcus aureus CC398 in broilers

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) has emerged in a wide variety of animal species, including poultry. The objective of this study was to evaluate three different chromogenic media for MRSA clonal complex (CC) 398 detection in broilers. On three Belgian poultry farms, 50 broiler chickens were sampled per farm from both nose shell and cloaca. All swab specimens were enriched and inoculated the following day on three chromogenic media: chromID MRSA (bioMérieux), Brilliance MRSA 2 Agar (Oxoid) and MRSASelect (Bio-Rad). ChromID had the highest isolation rates, yet, Brilliance MRSA 2 Agar demonstrated the highest relative sensitivity, while MRSASelect and Brilliance MRSA 2 Agar showed the highest relative specificity. A subset of MRSA isolates was confirmed to be CC398 by the polymerase chain reaction (PCR) targeting sau1-hsdS1. In conclusion, Brilliance MRSA 2 Agar outperformed MRSASelect and chromID MRSA for the detection of MRSA in broilers.

Targeting aminopeptidase N, a newly identified receptor for F4ac fimbriae, enhances the intestinal mucosal immune response

Enterotoxigenic Escherichia coli (ETEC) are a major cause of diarrhea in human and animal. In piglets, ETEC having F4 fimbriae (F4(+) ETEC) induce severe diarrhea, dependent on the presence of receptors for F4 (F4R). In this study, porcine aminopeptidase N (pAPN) was identified as an F4R by comparative proteomic analysis of brush border proteins of F4R(+) and F4R(-) pigs and by adherence/internalization experiments on pAPN-transfected cells. Binding of F4 fimbriae to pAPN depended on sialic acid containing carbohydrate moieties, and resulted in clathrin-mediated endocytosis of the fimbriae. Endocytosis via pAPN was not restricted to F4 fimbriae, but was also observed for anti-pAPN antibodies. Both F4 fimbriae- and pAPN-specific antibodies were taken up in vivo by porcine enterocytes and induced subsequently a rapid immunoglobulin A and G response. In conclusion, we identified pAPN as an endocytotic receptor for F4 fimbriae and highlight the opportunity to target vaccine antigens to this epithelial receptor.

The effect of enterotoxigenic Escherichia coli F4ab,ac on early-weaned piglets: a gene expression study

Diarrhoea in neonatal and early-weaned piglets due to enterotoxigenic Escherichia coli-F4 (ETEC-F4) is an important problem in the pig farming industry. There is substantial evidence for a genetic basis for susceptibility to ETEC-F4 since not all pigs suffer from diarrhoea after an ETEC-F4 infection. A region on SSC13 has been found to be in close linkage to the susceptibility of piglets for ETEC-F4ab,ac. Potential candidate genes on SSC13 have been examined and although some polymorphisms were found to be in linkage disequilibrium with the phenotype, the causative mutation has not yet been found. In this study we are looking at the expression of porcine genes in relation to ETEC-F4ab,ac. With the aid of the Affymetrix GeneChip Porcine Genome Array we were able to find differentially expressed genes between ETEC-F4ab,ac receptor positive (Fab,acR(+)) piglets without diarrhoea and F4ab,acR(+) piglets with diarrhoea or F4ab,acR(-) animals. Since the susceptibility to ETEC-F4ab,ac was described as a Mendelian trait, it is not so surprisingly that only two differentially expressed genes, transferrin receptor (TFRC) and trefoil factor 1 (TFF1), came out of the analysis. Although both genes could pass for functional candidate genes only TFRC also mapped to the region on SSC13 associated with susceptibility for ETEC-F4, which makes TFRC a positional functional candidate gene. Validation by qRT-PCR confirmed the differential expression of TFRC and TFF1. In piglets without diarrhoea, the expression of both genes was higher in F4ab,acR(+) than in F4ab,acR(-) piglets. Similarly, TFRC and TFF1 expression in F4ab,acR(+) piglets without diarrhoea was also higher than in F4ab,acR(+) piglets with diarrhoea. Consequently, although both genes might not play a role as receptor for F4 fimbriae, they could be of great importance during an ETEC-F4 outbreak. An upregulation of TFRC can be a consequence of the piglets ability to raise an effective immune response. An elevation of TFF1, a protein involved in mucin formation, may also affect the piglet's capability to cope with ETEC bacteria, rather than being a receptor for its fimbriae.

Evaluation of salt concentrations, chromogenic media and anatomical sampling sites for detection of methicillin-resistant Staphylococcus aureus in pigs

The performance of chromogenic media for the detection of methicillin-resistant Staphylococcus aureus (MRSA) in humans, has been evaluated in numerous studies. However, few comparative studies have been performed for the detection of MRSA in pigs. In this study two different salt concentrations (2.5% or 7.5% NaCl) were evaluated in the enrichment nutrient broth and three selective chromogenic media (chromID MRSA, BrillianceMRSA and MRSASelect) for their ability to detect MRSA in swabs from 29 pigs obtained from three different anatomical sampling sites (anterior nares, skin behind both ears and perineum). ChromID MRSA showed the highest relative sensitivity and specificity after enrichment in 7.5% NaCl, followed by MRSASelect and BrilianceMRSA. For all chromogenic media more MRSA-positive results were obtained for specimens collected from skin behind the ears than for specimens taken from both nares and perineum. The results with regard to the anatomical sampling sites were confirmed in a larger study on three different pig farms involving 60 pigs per farm. Skin behind the ears was the anatomical site with the highest relative sensitivity (91.4%) for MRSA detection compared to perineum and anterior nares, with a relative sensitivity of 76.5% and 75.3%, respectively. An increased relative sensitivity could be achieved when combining two anatomical sites. Sampling of anterior nares and skin behind the ears appeared to be the most sensitive combination with a relative sensitivity of 98.2%. These results show that sampling of only the anterior nares underestimates the real pig MRSA prevalence.

Screening of poultry-pig farms for methicillin-resistant Staphylococcus aureus: sampling methodology and within herd prevalence in broiler flocks and pigs

Many reports described the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in different livestock animals from one-species farms. However, in no published reports the prevalence on mixed poultry-pig farms was mentioned, nor the possible relation in MRSA colonization between those two species on one farm, and the possible role of the farmer in the dissemination of MRSA between those two species. Furthermore, no data is available on the optimal sampling site to detect MRSA in broilers. Therefore this study aimed to determine the most suitable sample location in broiler chickens for MRSA and the within flock prevalence of MRSA in various broiler flocks and compared this with the MRSA prevalence in pigs, the colonization of the farmer and the contamination in the barn environment in three mixed poultry-pig farms. MRSA was most frequently isolated from the cloaca and nose shell and to a lesser extent from the skin beneath the wing and the pharynx. The relative sensitivity of the different anatomical sites was, 44.4% for the cloaca, 33.3% for the nose shell, 16.7% for the skin beneath the wing and 5.6% for the pharynx. Based upon these relative sensitivities combining cloaca and nose shell would increase the chance of MRSA detection. A rather low within flock prevalence of MRSA varying between 0% and 28% was detected in broilers, whereas in pigs on the same farms the within herd prevalence varied between 82% and 92%. No MRSA contamination in the direct barn environment of the broilers was found, this in contrast to the environment of the pigs, indicating a relationship between MRSA prevalence and contamination in the environment. Two farmers were continuously colonized, while the third one was only once. In conclusion, a major difference was seen in MRSA occurrence between broilers and pigs from the same farm. This may suggest that broilers are naturally less susceptible to MRSA ST398 colonization than pigs. Conversely, short production time in broilers, vacancy of the barn environment during one week and the higher frequency of disinfection might also explain the lower prevalence in broilers. The farmer may play an important role in the dissemination of MRSA from pigs to poultry, especially in mixed farms where pigs are highly colonized and may act as a reservoir for MRSA ST398 carriage in humans.

Reduction of Escherichia coli O157:H7 excretion in sheep by oral lactoferrin administration

Ruminants are an important reservoir of Escherichia coli O157:H7, therefore reducing E. coli O157:H7 excretion by these animals could play a key role in reducing human infections. The present study investigates the potential of bovine lactoferrin, a natural antimicrobial-immunomodulatory protein of milk, to prevent colonization and excretion of E. coli O157:H7 in sheep. The effect of two different doses of lactoferrin (1.5 g or 0.15 g per 12h) was evaluated on colonization of sheep intestine and faecal excretion of the NCTC12900 strain. Hereto, lactoferrin was orally administered to sheep during 30 consecutive days and sheep were experimentally infected with E. coli O157:H7 on the second day of the lactoferrin administration. Interestingly, both lactoferrin dosages significantly reduced the number of E. coli O157:H7 in faeces as well as the duration of faecal excretion. The high dose group showed a significantly higher antibody response against EspA and EspB, two structural proteins of the bacterial type III secretion system (TTSS), than the colonization control group. The results suggest that oral lactoferrin administration could be used to prevent persistent colonization of sheep with E. coli O157:H7.

Efficacy of Cymelarsan and Diminasan against Trypanosoma equiperdum infections in mice and horses

Trypanocidal sensitivity studies were conducted to assess the efficacy of Diminazene diaceturate (Diminasan) and Bis (aminoethylthio) 4-melaminophenylarsine dihydrochloride (Cymelarsan) against Trypanosoma equiperdum (isolated from two mares with chronic cases of dourine) 713/943 and 834/940 Dodola strains in experimentally infected mice and horses. Diminasan at doses from 3.5 mg/kg to 28 mg/kg and Cymelarsan at doses of 0.25 mg/kg and 0.5 mg/kg body weight failed to cure any of the mice, indicating a clear dose dependent relationship in the mean time of relapse observed in mice. Indeed, mice treated with lower doses relapsed after a shorter time than mice treated with higher doses. However, mice treated with Cymelarsan at doses of 1.0 mg/kg and 2.0 mg/kg body weight were cured and no parasitemia was observed for 60 days. The efficacy of Cymelarsan was also tested in horses. Two groups of horses containing two animals each were infected with T. equiperdum 834/940 Dodola strain and treated with Cymelarsan at a dose rate of 0.25 mg/kg and 0.5 mg/kg, respectively. Cymelarsan at 0.25 mg/kg and 0.5 mg/kg body weight cleared parasitemia within 24 h post treatment and none of the animals were found to show relapse throughout the 320 days of observation. The sensitivity of the particular trypanosome strain to Cymelarsan was also supported by the relative improvement in the mean PCV levels of horses following treatment. A statistically significant difference (p<0.01) in the mean PCV levels of horses treated with Cymelarsan was observed between day 20 at peak parasitemia and days 40 as well as 60 of observation. The mean PCV levels of horses in the control group progressively decreased within the first 60 days of post infection. Two of the horses in the control group developed chronic form of dourine manifested by genital as well as nervous signs with progressive loss of body condition within 320 days post infection. The efficacy of Cymelarsan against the chronic form of dourine was confirmed after treatment of one of the control horses with Cymelarsan at a dose rate of 0.25 mg/kg body weight at day 282 post infection. It was noted that the treated horse improved overall body condition and clinical signs such as incoordination of hind legs, weakness and ventral oedema disappeared within 10 days of treatment. Thus, Cymelarsan was found to be quite effective in curing horses in acute as well as chronic form of dourine. The results obtained from the present study will be important for designing effective control measures against dourine.

Demonstration of differences in virulence between two Theileria parva isolates

In areas with a low incidence of infection due to unimodal presence of ticks, Theileria parva has been observed to induce a disease with relatively low pathology. This is followed by a carrier state, rather than death and therefore provides a better chance of transmission of the parasite back to the tick vector since in unimodal conditions, the different tick stages occur at different times. One isolate from such an area in Zambia, T. parva Chitongo, was compared for virulence with T. parva Muguga, isolated from an area exhibiting a continuous presence of all vector stages in East Africa. To reduce any variation due to infection dose, an in vitro standardized dose was used to initiate infection of groups of three local zebu cattle with each isolate. Parameters of virulence measured were prepatent period, fever, survival (based on ECF index), parasitosis, piroplasm parasitaemia and hematological parameters. Our results suggest that T. parva Chitongo developed a slightly later onset (1-2 days) and lower levels of parasitosis in the lymph node, causing less and later mortality. Comparison of the in vitro rate of transformation confirmed that the time needed to transform an infected lymphocyte took 4 days longer for T. parva Chitongo than T. parva Muguga. Elucidating the mechanism responsible for the lower virulence of T. parva Chitongo could be useful for designing an attenuated vaccine.

The age-dependent expression of the F18+ E. coli receptor on porcine gut epithelial cells is positively correlated with the presence of histo-blood group antigens

F18(+)Escherichia coli have the ability to colonize the gut and cause oedema disease or post-weaning diarrhoea by adhering to specific F18 receptors (F18R) on the porcine epithelium. Although it is well established that a DNA polymorphism on base pair 307 of the FUT1 gene, encoding an alpha(1,2)fucosyltransferase, accounts for the F18R phenotype, the F18R nature is not elucidated yet. The aim of the present study was to investigate the correlation between the presence of H-2 histo-blood group antigens (HBGAs) or its derivative A-2 HBGAs on the porcine gut epithelium and F18(+)E. coli adherence. A significant positive correlation was found between expression of both the H-2 (r=0.586, P<0.01) and A-2 (r=0.775, P<0.01) HBGAs and F18(+)E. coli adherence after examination of 74 pigs aged from 0 to 23 weeks. The majority of the genetically resistant pigs (FUT1M307(A/A)) showed no HBGA expression (91.7%) and no F18(+)E. coli adherence (83.3%). In addition, it was found that F18R expression levels rise with increasing age during the first 3 weeks after birth and that F18R expression is maintained in older pigs (3-23 weeks old). Taken together, these data suggest that, apart from H-2 HBGAs, A-2 HBGAs might be involved in F18(+)E. coli adherence.

Perinatal priming of calves born to Schistosoma mattheei-infected dams

The objective of this study was to elucidate whether calves born to infected dams had been primed against Schistosoma mattheei antigens. Infection-confirmed, pregnant cows were randomly selected for monitoring their offspring. Pre-colostral serum was collected from the neonates for the detection of specific antibodies at birth, as they indicate a transplacental transfer of schistosome-specific antibodies and antigen. At the age of approximately 2 months, peripheral blood mononuclear cells (PBMC) of calves were analysed for specific memory by antigen-specific stimulation in vitro. Twenty-six of the 30 calves demonstrated S. mattheei-specific proliferation. All 12 seropositive-born, as well as 14 of the 18 seronegative-born (before colostrum uptake) calves displayed mattheei-specific proliferation. The results indicate that the calves were primed against S. mattheei and might explain why seropositive-born calves from infected dams are better protected against S. mattheei, and query the impermeability of the damaged ruminant placenta with consequences for antigen transfer.

Screening of pigs resistant to F4 enterotoxigenic Escherichia coli (ETEC) infection

The present study analysed quantitatively the mucin 4 polymorphism for determining the F4ac/ab receptor status of a total of 63 pigs by comparing it with the in vitro villous adhesion assay. The probability of a susceptible genotype for the mucin 4 increases significantly with increasing F4ab or F4ac ETEC adhesion per 250 microm villi (P=0.029 for F4ab, P=0.030 for F4ac), with the odds ratio for each unit increase of F4ab or F4ac equal to, respectively, 1.036 (95% CI [1.004-1.069]) and 1.018 (95% CI [1.002-1.034]). In the phenotypic in vitro villous adhesion test, a cut-off value of 5 bacteria was chosen as a criteria for the distinction between an F4R positive and F4R negative pig. The sensitivity and specificity for the in vitro villous adhesion test, with the genotyping test for mucin 4 as golden standard, is 100% and 24%, respectively, for F4ab as well as F4ac. Absence of adhesion of F4ac and F4ab ETEC to the villous brush borders was not associated with genotypic resistance suggesting that there is at least one other receptor for F4ab/ac Escherichia coli. As a consequence, not only mucin 4 gene polymorphism but also expression of these other receptor(s) has to be included in a screening assay for F4ac/ab receptor negative pigs.

Comparison of immune responses in parenteral FaeG DNA primed pigs boosted orally with F4 protein or reimmunized with the DNA vaccine

We previously showed that an intradermal (i.d.) FaeG DNA prime (2x)-oral F4 protein boost immunization induces a systemic response and weakly primes a mucosal IgG response in pigs, especially when plasmid vectors encoding the A and B subunit of the E. coli thermo-labile enterotoxin (LT) are added to the DNA vaccine. In the present study, we evaluated whether addition of 1alpha,25-dihydroxyvitamin D(3) (vitD(3)) to the DNA vaccine could further enhance this mucosal priming and/or modulate the antibody response towards IgA. To further clarify priming of systemic and mucosal responses by the i.d. DNA vaccination, we firstly compared the localization of the F4-specific antibody response in pigs that were orally boosted with F4 to that in pigs that received a third i.d. DNA immunization and secondly evaluated cytokine mRNA expression profiles after i.d. DNA vaccination. The i.d. DNA prime (2x)-oral F4 boost immunization as well as the 3 i.d. DNA vaccinations induced mainly a systemic response, with a higher response observed following the heterologous protocol. Co-administration of vitD(3), and especially of the LT vectors, enhanced this response. Furthermore, only the heterologous immunization resulted in a weak mucosal priming, which appeared to require the presence of the LT vectors or vitD(3) as adjuvants. In addition, the LT vectors strongly enhanced the FaeG-specific lymphocyte proliferation and this was accompanied by the absence of a clear IL-10 response. However, despite two DNA immunizations in the presence of these adjuvants and an oral F4 boost, we failed to demonstrate the secretory IgA response needed to be protective against enterotoxigenic E. coli.

Optimized FaeG expression and a thermolabile enterotoxin DNA adjuvant enhance priming of an intestinal immune response by an FaeG DNA vaccine in pigs

One of the problems hindering the development of DNA vaccines is the relatively low immunogenicity often seen in humans and large animals compared to that in mice. In the present study, we tried to enhance the immunogenicity of a pcDNA1/faeG19 DNA vaccine in pigs by optimizing the FaeG expression plasmid and by coadministration of the plasmid vectors encoding the A and B subunits of the Escherichia coli thermolabile enterotoxin (LT). The insertion of a Kozak sequence and optimization of vector (cellular localization and expression) and both vector and codon usage were all shown to enhance in vitro FaeG expression compared to that of pcDNA1/faeG19. Subsequently, pcDNA1/faeG19 and the vector-optimized and the vector-codon-optimized construct were tested for their immunogenicity in pigs. In line with the in vitro results, antibody responses were better induced with increasing expression. The LT vectors additionally enhanced the antibody response, although not significantly, and were necessary to induce an F4-specific cellular response. These vectors were also added because LT has been described to direct the systemic response towards a mucosal immunoglobulin A (IgA) response in mice. Here, however, the intradermal FaeG DNA prime-oral F4 boost immunization resulted in a mainly systemic IgG response, with only a marginal but significant reduction in F4+ E. coli fecal excretion when the piglets were primed with pWRGFaeGopt and pWRGFaeGopt with the LT vectors.

In VivoActivation of Chicken Macrophages by Infectious Bursal Disease Virus

Infectious bursal disease virus (IBDV) infects and replicates in the dividing B lymphocytes of chickens. In the present study, the in vivo effect of IBDV infection on chicken macrophage populations and macrophage activation were examined. Specific-pathogen-free chickens were exposed to virulent IBDV and splenic macrophages were recovered during the acute phase of the disease. At 3 and 5 days post-infection (dpi), spleens of virus-exposed chickens had fewer macrophages than those of virus-free controls (p < 0.05). Confocal microscopic examination revealed cells that were positive for both KUL01 (macrophage surface marker) and R63 (IBDVVP2), indicating presence of the virus in macrophages. MQ-NCSU cells, an avian macrophage cell line, were susceptible to replication of IBDV. In addition, splenic macrophages were activated and had temporarily increased levels of mRNA transcripts of pro-inflammatory mediators, including IL-1beta, IL-6, IL-18, and iNOS. The robust expression of proinflammatory cytokine transcripts, along with a decrease in macrophage numbers, suggest that IBDV activates and may lead to a reduction of resident macrophages in vivo.

The jejunal Peyer's patches are the major inductive sites of the F4-specific immune response following intestinal immunisation of pigs with F4 (K88) fimbriae

A recently developed oral immunisation model in pigs in which F4 (K88) fimbriae of enterotoxigenic Escherichia coli are administered to induce a protective intestinal immunity, was used to determine the optimal inductive sites of the F4-specific intestinal immune response. Hereto, pigs were immunised with F4 orally, in the lumen of the mid-jejunum, ileum or mid-colon. Throughout the small intestine, the highest number of ASC was found following jejunal immunisation, followed by ileal, oral and colonic immunisation. To determine the signifance of Peyer's patches in the induced immune response, F4 was injected into the jejunal Peyer's patches (JPP), lamina propria (LP) and ileal Peyer's patches (IPP). Immunisation in the JPP induced the highest number ASC in the small intestine, whereas immunisation in the LP and IPP resulted in lower intestinal antibody responses. In conclusion, we have shown that the JPP are the major inductive sites of the F4-specific intestinal antibody response. This knowledge could be important when using the pig as an animal model for vaccination studies.

Cytokine responses in immunized and non-immunized calves after Ostertagia ostertagi infection

The objective of this study was to evaluate abomasal cytokine responses in helminth-naive calves and calves vaccinated with protective antigen fractions from Ostertagia ostertagi after an experimental challenge infection with infective third stage (L3) larvae. Abomasal lymph nodes and/or abomasal mucosa were collected and messenger RNA for the Th1 cytokines (IFN-gamma, IL-2, IL-12 p40 subunit), the Th2 cytokines (IL-4, IL-5, IL-6, IL-10, IL-13, IL-15) and the Th3/Tr cytokine TGF-beta was quantified by real-time RT-PCR. Vaccination had no effect on cytokine profiles in either the abomasal lymph nodes or the abomasal mucosa. However, following infection all calves showed a significant decrease in the Th1 cytokines, IFN-gamma and IL-12 p40, and a significant increase in the Th2 cytokines, IL-4, IL-5, IL-10 and IL-13 in the lymph nodes, compared to non-infected calves. No correlation between the Th2 response and protection induced by vaccination could be demonstrated. In contrast, a Th2 pattern was not observed in the mucosa of the infected calves, which exhibited an increase in IFN-gamma as well as in the Th2 cytokines IL-4, IL-5 and IL-10 mRNA. No significant association was observed in the abomasal mucosa between any examined cytokine mRNA level and immune effector responses such as parasite-specific antibodies or the number of mucosal mast cells or eosinophils.

F4 (K88) fimbrial adhesin FaeG expressed in alfalfa reduces F4+ enterotoxigenic Escherichia coli excretion in weaned piglets

Transgenic plants are attractive bioreactors to large-scale production of recombinant proteins because of their relatively low cost. This study reports for the first time the use of transgenic plants to reduce enterotoxigenic Escherichia coli (ETEC) excretion in its natural host species. The DNA sequence encoding the major subunit and adhesin FaeG of F4+ ETEC was transformed into edible alfalfa plants. Targeting of FaeG production to chloroplasts led to FaeG levels of up to 1% of the total soluble protein fraction of the transgenic alfalfa. Recombinant plant-produced FaeG (pFaeG) remained stable for 2 years when the plant material was dried and stored at room temperature. Intragastric immunization of piglets with pFaeG induced a weak F4-specific humoral response. Co-administration of pFaeG and the mucosal adjuvant cholera toxin (CT) enhanced the immune response against FaeG, reflected a better induction of an F4-specific immune response. In addition, the intragastric co-administration of CT with pFaeG significantly reduced F4+ E. coli excretion following F4+ ETEC challenge as compared with pigs that had received nontransgenic plant material. In conclusion, transgenic plants producing the FaeG subunit protein could be used for production and delivery of oral vaccines against F4+ ETEC infections.

Pathogenic interactions between Chlamydophila psittaci and avian pneumovirus infections in turkeys

Both Chlamydophila psittaci and avian pneumovirus (APV) are highly prevalent in Belgian turkeys and might contribute to the respiratory disease complex observed in turkeys. Initial outbreaks of chlamydiosis occur mostly at the age of 4-8 weeks, often accompanied by an APV infection in APV non-vaccinated farms. Regardless APV vaccination, breakthroughs of APV infection from 8 weeks on do occur, a period when also a second C. psittaci infection appears. Therefore, this study examined the pathogenicity of an APV superinfection in C. psittaci predisposed turkeys. Turkeys were infected with C. psittaci, APV or with C. psittaci followed by APV. Simulating the impact of an APV infection during the acute phase or latent phase of a C. psittaci infection, turkeys have been infected with APV at 1 and 5 weeks post C. psittaci infection, respectively. APV infection during the acute phase of a C. psittaci infection aggravates the severity of clinical signs, macroscopic lesions, pharyngeal APV excretion and histological tracheae lesions. In contrast, no clear interaction could be established after APV infection in latently C. psittaci infected specific pathogen-free (SPF) turkeys. This study clearly demonstrates the exacerbating role of APV during acute C. psittaci infection, which can play an important role in the respiratory disease complex of turkeys.

Comparison of serological tests for equine trypanosomosis in naturally infected horses from Kazakhstan

In this study, we compared the complement fixation test (CFT), the horse complement fixation test (HCFT) and a card agglutination test for trypanosomosis (CATT/T. evansi) for the diagnosis of equine trypanosomosis in the Republic of Kazakhstan. Cohen's kappa test was used to evaluate the concordance between the three tests. Kappa scores for CFT versus HCFT and CATT are both 0.6165 (95% Confidence Interval CI 0.414--0.819) indicating a "substantial" agreement between CFT and HCFT or CATT, respectively. Kappa for HCFT versus CATT is 0.395 (CI 0.142--0.648) indicating a "fair" agreement between the two tests. In the absence of a golden standard, seroprevalence and sensitivity and specificity of the three tests were estimated using maximum likelihood estimation. CFT has a sensitivity of 57.2% (CI 31.5--79.5%) and a specificity of 95.8% (CI 89.2--98.5%), HCFT has a sensitivity of 80.6% (CI 44.1--95.6%) and a specificity of 99.5% (CI 90.7--100%), CATT has a sensitivity of 80.2% (CI 44.5--95.2%) and a specificity of 98.5% (CI 79.5--99.9%). The seroprevalence of equine trypanosomosis in Kazakhstan was estimated at 16.4% (CI 9.4--27.0%). The data suggest that for epidemiological studies and the control of equine trypanosomosis serological tests prove useful since they have a high specificity and a satisfactory sensitivity. Field applicable tests, such as CATT/T. evansi may be used to replace laboratory-based tests, such as CFT and HCFT.

Key role of Chlamydophila psittaci on Belgian turkey farms in association with other respiratory pathogens

Two hundred turkey sera from eight Belgian and two French farms were tested for the presence of antibodies against avian pneumovirus (APV), Ornithobacterium rhinotracheale (ORT), Mycoplasma gallisepticum, Mycoplasma meleagridis and Chlamydophila psittaci. At slaughter, C. psittaci, APV and ORT antibodies were detected in 94, 34 and 6.5% of the turkeys, respectively. No antibodies against M. gallisepticum or M. meleagridis were present. Additionally, turkeys on three Belgian farms were examined from production onset until slaughter using both serology and antigen or gene detection. All farms experienced two C. psittaci infection waves, at 3-6 and 8-12 weeks of age. Each first infection wave was closely followed by an ORT infection starting at the age of 6-8 weeks, which was still detectable when the second C. psittaci infection waves started. Animals on farm A were not vaccinated against APV leading to an APV subtype B outbreak accompanying the first C. psittaci infection wave. Despite subtype A APV vaccination on farms B and C, the second C. psittaci infection waves were accompanied (farm B) or followed (farm C) by a subtype B APV infection. On all farms respiratory signs always appeared together with a proven C. psittaci, APV and/or ORT infection. This study suggests an association between C. psittaci, APV and ORT, and indicates the multi-factorial aetiology of respiratory infections in commercial turkeys. All three pathogens should be considered when developing prevention strategies for respiratory disease.

Protection of turkeys against Chlamydophila psittaci challenge by DNA and rMOMP vaccination and evaluation of the immunomodulating effect of 1α,25-dihydroxyvitamin D3

Plasmid DNA expressing the major outer membrane protein (MOMP) of an avian Chlamydophila psittaci serovar D strain and recombinant MOMP (rMOMP) with or without the immunomodulating adjuvant 1 alpha,25-dihydroxyvitamin D(3) have been tested for their ability to elicit an immune response and induce protection in turkeys against challenge with the same serovar. Three vaccination strategies were compared: priming and boosting with either pcDNA1::MOMP or rMOMP and priming with pcDNA1::MOMP followed by rMOMP boosting. Turkeys primed with pcDNA1::MOMP showed significant protection against Cp. psittaci challenge, turkeys primed with rMOMP did not. The steroid hormone 1 alpha,25-dihydroxyvitamin D(3) augmented serum and mucosal antibody titres. However, higher antibody titres were not related to better protection and even had a negative effect on especially bacterial excretion.

Development of an enteric-coated pellet formulation of F4 fimbriae for oral vaccination of suckling piglets against enterotoxigenic Escherichia coli infections

A multi-particulate formulation of F4 fimbriae was developed for oral vaccination of suckling piglets against enterotoxigenic Escherichia coli infections. A feasibility test showed that incorporation of F4 fimbriae in a disintegrating pellet formulation consisting of 87.5% Pharmatose 200 M, 2.5% Avicel CL 611 and 10% Explotab by extrusion/spheronisation and subsequent fluid bed drying resulted in the maintenance of 69+/-12% of the biological activity. But subsequent coating resulted in pellets with poor enteric properties, although good in vivo immunising results were obtained after administration to piglets. From the economical point of view, a pellet formulation was optimised to decrease vaccine dose and dosing frequency. After disintegration testing, pellets consisting of lactose (alpha-lactose monohydrate 90 mesh/beta-lactose 75/25 (w/w)) and microcrystalline cellulose in a ratio of 80/20 (w/w) showed a sponge-like structure from which F4 fimbriae could be released. Coating of these pellets resulted in good enteric properties. To improve disintegrating properties of the pellets, the lactose concentration was increased or sodium carboxymethyl starch was added. But this resulted in poor enteric properties after coating. Dissolution test showed that F4 fimbriae were released from the optimised enteric-coated pellets but interaction between F4 fimbriae and the coating polymer was seen. This incompatibility leads to unpredictable in vitro quantification of F4 biological activity.

Porcine-specific CpG-oligodeoxynucleotide activates B-cells and increases the expression of MHC-II molecules on lymphocytes

Two CpG-oligodeoxynucleotide motifs, a mouse-specific one (CpG(mouse)) 5'-GCTAGACGTTAGCGT-3' and a porcine-specific one (CpG(pig)), 5'-TGCATCGATGCAG-3' were synthesized by two different companies and tested in vitro for their capacity to stimulate porcine peripheral blood monomorphonuclear cells (PBMC). The porcine-specific motif, consisting of a nuclease-resistant phosphorothioate guanosines at the 5' and at the 3'-end (CpG(pig)-S), enhanced significantly the proliferation of porcine PBMC in comparison with CpG(mouse). The latter motif did not induce any proliferation. Methylation of CpG(pig) diminished the proliferation. Four days of culture with CpG(pig)-S increased the percentage of B-cells as well as B-cell blasting. Moreover, CpG(pig)-S also enhanced the expression of class II MHC in most cultures while there were no changes in percentage of macrophages or in the degree of expression of the macrophage marker (monoclonal 74-22-15). In conclusion, in this study, it was confirmed that 5'-ggTGCATCGATGCAGggggg-3' is a swine-specific CpG-ODN, that activates porcine B-cells and deserves further evaluation in vivo as a potential immunostimulating adjuvant.

Immunocompetence of fattening pigs fed organic versus conventional diets in organic versus conventional housing

The effect of organic or conventional feeding on the immune response of pigs was determined using organic or conventional housing in a pig fattening unit. The experimental design involved four pens of four animals per housing and diet combination (organic housing and organic nutrition; organic housing and conventional nutrition; conventional housing and organic nutrition and conventional housing and conventional nutrition). The IgM, IgA and IgG responses against intramuscularly injected bovine thyroglobulin were determined as indicators of the antigen-specific immune responsiveness. Some general health and welfare related parameters were evaluated by measuring haptoglobin concentrations at selected times; blood lactate concentration was measured at slaughter. Conventional housing led to a higher IgG response three weeks after the first immunisation. Organic housing led to lower haptoglobin and lactate concentrations at slaughter, indicating a higher stress resistance in these pigs. No major differences between the two feeding types were found. We conclude that the immune responses following either a conventional or an organic diet are comparable, whereas organic housing can increase stress resistance at slaughter compared to conventional housing.

Fimbriae of enterotoxigenic Escherichia coli function as a mucosal carrier for a coupled heterologous antigen

Receptor-mediated uptake of orally administered antigen can lead to an antigen-specific immune response, whereas oral administration of most other non-replicating soluble antigens results in the induction of oral tolerance. In the present study, it is shown that fimbriae purified from an F4(K88)(+) enterotoxigenic Escherichia coli strain can function as a mucosal carrier molecule for the model antigen human serum albumin (HSA). Glutaraldehyde-coupled F4/HSA conjugates were able to bind F4 receptor positive (F4R(+)) enterocytes, but not to F4R(-) enterocytes. Moreover, oral immunization of F4R(+) pigs with F4/HSA conjugates induced a HSA-specific immune response, whereas oral immunization with HSA/HSA conjugates did not. This mucosal carrier function of F4 fimbriae was improved following oral co-administration of the F4/HSA conjugates with the mucosal adjuvant cholera toxin (CT) to F4R(+) pigs, since both humoral and cellular HSA-specific responses were significantly increased. In comparison with F4R(+) pigs, the HSA-specific response was reduced following oral F4/HSA+CT immunization of F4R(-) pigs. This indicates that F4 fimbriae as mucosal carrier and CT as adjuvant synergistically improve the induction of a HSA-specific immune response following oral immunization of pigs. These results could open new perspectives in the development of vaccines against enteropathogens.

Placental transfer of immunoglobulins in cattle infected with Schistosoma mattheei

Although the epitheliochorial placenta of ruminants does not allow passage of immunoglobulins from dam to foetus specific antibodies have been detected at birth in calves born to Schistosoma mattheei-infected cows. The present study determined the prevalence of calves born with specific antibodies for S. mattheei and the origin of these antibodies. For the determination of the prevalence, 100 calves born to infected mothers in an endemic area (Zambia) were examined, 24 were seropositive. To study the origin of these antibodies placentomes of 40 naturally S. mattheei-infected cows were examined for the presence of schistosome eggs and lesions which could explain foetal priming and/or leakage of maternal antibodies and/or antigen into the foetus. Tissue damage and schistosome eggs were observed on the maternal as well as the foetal side of the placentomes. In order to determine the specific nature of the antibody response, antibody profiles against soluble adult worm antigen preparation (SWAP) of S. mattheei were compared by Western blot between dams and their newborn calves (n = 8). The specific recognition profiles were identical for the seropositive calves and their dams on SWAP mattheei. Identical recognition profiles between dams and calves were also observed when sera were analysed on Escherichia coli, a pathogen of which the foetus should be free, and would indicate passive antibody transfer from the dam. In conclusion, the present study shows that S. mattheei could induce placentome lesions and that eggs can cross the placenta. Consequently, foeti can come into contact with S. mattheei antigens in utero, and might also contain maternal antibodies from leakage through placentome lesions. As such, the infection status of the mother could have far reaching effects on the immunological status of her offspring and modify their reaction upon infection.

Immunostimulatory capacity of DNA vaccine vectors in porcine PBMC: a specific role for CpG-motifs?

With the development of DNA vaccines in pigs, the possibility was investigated that the nature and the amount of certain CpG-motifs present on plasmid DNA might have an effect on their immunostimulatory capacity. A panel of three CpG-oligodeoxynucleotides (ODN) and three eukaryotic expression vectors currently used in experimental DNA vaccines in pigs (pcDNA1, pcDNA3.1 and pCI) were screened for their immunostimulatory activity on porcine PBMC by evaluating in vitro the lymphocyte proliferative responses and cytokine profiles (IL-1alpha, IL-2, IL-4, IL-6, IL-10, IFN-gamma, TGF-beta, TNF-alpha). The vectors were chosen so that they differed in number and nature of certain CpG-motifs present on their backbone. CpG-ODN A (5'ATCGAT3') and to a lesser extend CpG-ODN C (5'AACGTT3') significantly enhanced the proliferation of porcine PBMC in contrast to CpG-ODN B (5'GACGTT3') where no effect was observed. Furthermore, CpG-ODN A significantly induced IL-6 and TNF-alpha together with elevated levels of IFN-gamma and IL-2 mRNA expression even though considerable heterogeneity was observed in the response of individual pigs. Comparison of the three vectors showed significantly increased proliferative responses for both pcDNA3.1 and pCI combined with a significant increase in IL-6 mRNA levels for pCI. For pcDNA1, proliferation was absent together with significantly decreased levels of IL-6 and IFN-gamma. CpG-ODN and plasmids both suppressed the TGF-beta and IL-1alpha mRNA expression. Taken together, these data confirm the identity of an optimal immunostimulating CpG-motif in pigs (5'-ggTGCATCGATGCAG-3') and demonstrates that the choice of the vector or the insertion of immunostimulatory motifs can be important in the future design of DNA vaccines in pigs, although further research is necessary to explore the possible link between certain CpG-motifs and the immunogenicity of DNA vaccines.

Immunocompetence in organically fed finishing pigs: effect of corn cob mix

Two consecutive experiments were performed to evaluate the effects on the immune response of corn cob mix (CCM) in an organic pig diet. The immunoglobulin (Ig) M, IgA and IgG responses against an intramuscularly injected model antigen, bovine thyroglobulin, were used as indicator. The experiments were performed in an organic barn with nine pens of four crossbred pigs (two barrows and two sows) from 45 kg to slaughter. In the first experiment, the organic concentrate was mixed with organic CCM-silage to obtain three concentrate: CCM ratios of 100:0, 80:20 and 60:40 (w:w). In the second experiment, three concentrates were produced to obtain diets with equal nutrient levels on a dry matter basis after 0%, 20% and 40% CCM inclusion. Higher inclusion rates of CCM in the ration were accompanied by lower thyroglobulin-specific IgG responses. These effects could not be attributed to one specific component of the CCM, such as fatty acid composition, although there was a degree of correlation with lower vitamin A concentrations. Mycotoxin concentrations were absent or minimal. The study indicated that dietary ingredient composition may affect immunocompetence.

Cholera toxin improves the F4(K88)-specific immune response following oral immunization of pigs with recombinant FaeG

Oral immunization of both humans and animals with non-replicating soluble antigens often results in the induction of oral tolerance. However, receptor-dependent uptake of orally administered soluble antigens can lead to the induction of an antigen-specific immune response. Indeed, oral immunization of pigs with recombinant FaeG (rFaeG), the adhesin of the F4(K88) fimbriae of enterotoxigenic Escherichia coli (ETEC), induces an F4-specific humoral and cellular immune response. This response is accompanied with a reduction in the excretion of F4(+)E. coli following challenge. To improve the immune response against F4, rFaeG was orally co-administered with the mucosal adjuvant cholera toxin (CT). Oral immunization of pigs with rFaeG and CT significantly improved the induction of an F4-specific humoral and cellular immune response and also significantly reduced the faecal F4(+)E. coli excretion following F4(+) ETEC challenge as compared to rFaeG-immunized pigs. Therefore, the present study demonstrates that CT can act in pigs as a mucosal adjuvant for antigens that bind to the intestinal epithelium by a CT-receptor-independent mechanism.

Oral immunization of piglets with recombinant F4 fimbrial adhesin FaeG monomers induces a mucosal and systemic F4-specific immune response

The importance of adhesins in the pathogenicity of several bacteria resulted in studies on their usefulness in vaccines. In this study, the gene of the F4(K88)-fimbrial adhesin FaeG of the pathogenic enterotoxigenic Escherichia coli (ETEC) strain GIS26 was cloned in the pET30Ek-LIC vector and expressed with an N-terminal His- and S-tag in the cytoplasm of BL21(DE3). Recombinant FaeG (rFaeG) subunits were isolated from insoluble cytoplasmic aggregates and refolded into a native-like F4 receptor (F4R)-binding conformation. Indeed, the presence of conformational epitopes was shown by ELISA and the ability to bind the F4R was observed by inhibiting the adhesion of F4+ ETEC to F4R+ villi with increasing concentrations of native-like refolded rFaeG subunits. The rFaeG subunits appear as monomers, whereas the purified F4 fimbriae are multimers. Oral immunization of newly weaned piglets with native-like rFaeG induced a mucosal and systemic F4-specific immune response, significantly reducing F4+ E. coli excretion from 2 till 5 days following challenge infection. However, improvement of stability and immunogenicity of rFaeG is necessary since a higher F4-specific response was obtained following immunization with purified F4 fimbriae. Furthermore, the N-terminal fusion of a His- and S-tag was not detrimental for binding the F4R, supporting the use of FaeG as mucosal carrier. In conclusion, oral immunization with a recombinant fimbrial adhesin subunit of Escherichia coli induces a mucosal and systemic fimbriae-specific immune response.

F4 fimbriae expressed by porcine enterotoxigenic Escherichia coli, an example of an eccentric fimbrial system?

An overwhelming number of infectious diseases in both humans and animals are initiated by bacterial adhesion to carbohydrate structures on a mucosal surface. Most bacterial pathogens mediate this adhesion by fimbriae or pili which contain an adhesive lectin subunit. The importance of fimbriae as virulence factors led to research elucidating the regulation of fimbrial expression and their molecular assembly process. This review provides an overview of the current knowledge of induction, expression and assembly of F4 (K88) fimbriae and discusses its unique as well as its identical characteristics compared to other intensively studied fimbriae or pili expressed by Escherichia coli.

Binding of a monoclonal antibody positively correlates with bioactivity of the F4 fimbrial adhesin FaeG associated with post-weaning diarrhoea in piglets

Piglets are susceptible to F4 (K88)+ enterotoxigenic Escherichia coli (ETEC)-induced neonatal and post-weaning diarrhoea. The F4 fimbriae are composed of some minor subunits and the major subunit FaeG that also constitutes the adhesin. Parenteral vaccination of sows with an F4-containing vaccine protects the suckling piglets against neonatal F4+ ETEC-induced diarrhoea, but no commercial (mucosal) vaccine exists against F4+ ETEC-induced weaning diarrhoea. To develop a vaccine, a bioactive F4-receptor (F4R) binding FaeG molecule is required that binds to the F4R following oral immunization and induces a FaeG-specific immune response. The present study reports the altered binding of the FaeG-specific monoclonal antibody IMM01 with bioactive versus non-bioactive F4 fimbrial adhesin FaeG. The correlation of altered IMM01 binding with altered FaeG bioactivity permits the use of an IMM01-based ELISA as a fast, specific and sensitive in vitro selection for potent F4 or (recombinant) FaeG antigen formulations, useful in an F4+ ETEC vaccine.

Gastrointestinal transit time of nondisintegrating radio-opaque pellets in suckling and recently weaned piglets

The objective was to determine the gastrointestinal (GI) transit times of pellets in piglets at different time points around weaning, as transit times are essential criteria to develop oral drug delivery systems. Nondisintegrating radio-opaque pellets were given orally in order to define the transit times by radiography. The radiographs were analysed with a software programme to calculate the number of pellets present in the different parts of the GI tract. In suckling piglets, the gastric emptying was faster (75% in 1.5 to 3.5 h), and the colonic accumulation (to 73%) was greater than in weaned piglets (3 days, 2 and 3 weeks postweaning, 65% gastric emptying in 18 h, 75% in 17 h, and 75% in 7 h, respectively; maximal colonic accumulations of 48%). Immediately after weaning, the transit was markedly prolonged but shortened with increased postweaning time (3 days, 2 and 3 weeks postweaning, 85% excretion in 175.5, 77, and 50.5 h, respectively). Three weeks postweaning, the transit was no longer affected by weaning as transit times were similar to values reported in growing and adult pigs, and retention appeared to be restricted to the stomach and the colon. These data are of crucial importance in the design of enteric-coated formulations for oral administration of vaccines and therapeutics to young piglets and for human research using the pig model.

Conserved regions in the sequence of the F4 (K88) fimbrial adhesin FaeG suggest a donor strand mechanism in F4 assembly

Oral immunization of newly weaned piglets with recombinant F4 (K88) fimbrial adhesin FaeG induces a F4-specific immune response, significantly reducing F4+ Escherichia coli excretion following challenge. In order to use FaeG subunits in an oral vaccine against F4+ enterotoxigenic E. coli, it is necessary to determine the conservation of the adhesin subunit. Hereto, the faeG sequence was determined of 21 F4ac+ E. coli field isolates from piglets with diarrhoea and subsequently compared with these of the reference strain GIS26 and previously reported FaeG sequences from F4ab, F4ac and F4ad antigenic variant strains. The FaeG amino acid sequence was 96-100% homologous within each F4 serotype, but only 92 and 88% when the F4ab and F4ad antigenic variants were compared with the F4ac antigenic variant. Furthermore, the conserved regions of the adhesin suggest a donor strand mechanism in F4 fimbriae assembly as reported for type 1 and P pili. In conclusion, the results of the reported experiments support the usefulness FaeG in an oral subunit vaccine against F4+ E. coli infections or as a mucosal carrier since the adhesin is conserved among F4+ E. coli field isolates.

Inhibition of adhesion of F18+ Escherichia coli to piglet intestinal villous enterocytes by monoclonal antibody against blood group H-2 antigen

Enterotoxigenic and verotoxigenic F18+ Escherichia coli colonising the pig small intestine, adhere to receptors on intestinal villous enterocytes by F18 fimbriae. The aim of the present study was to define the F18R nature. The knowledge on the nature of this receptor could be important for the development of receptor-based treatments against F18+ E. coli-induced disease. The adhesion of F18+ E. coli to pig intestinal villous enterocytes was analysed in an in vitro assay. The adhesion of F18+ E. coli but not of F4ac+ E. coli was strongly inhibited by monoclonal antibodies (mAb) with blood group H-2 specificity. Conversely, blood group H-1 specific mAb could not inhibit the adhesion of F18+ E. coli nor F4ac+ E. coli. Moreover, the blood group H-2 trisaccharide strongly inhibited the adhesion of F18+ E. coli, but only partially the adhesion of F4ac+ E. coli. These data demonstrate that the F18 receptor contains the blood group antigen H-2 (alpha-fuc-(1-2)-beta-Gal-(1-4)-GlcNAc) as major carbohydrate.