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Human rotavirus (HRV) and human norovirus (HuNoV) are the most common causative agents of acute gastroenteritis- (AGE) related morbidity and mortality around the world. Gnotobiotic (Gn) pigs are the ideal large-animal model that allows for accurate, and precise, preclinical evaluation of vaccine efficacy. Similarities in gastrointestinal anatomy, physiology, and immune system allows for direct translation of results from Gn pigs to humans. Commercially available HRV vaccines perform significantly poorer in low- and middle- income countries as compared with developed countries. Non-replicating rotavirus vaccines (NRRVs) have been proposed as a viable solution to the problems facing currently available live-, attenuated oral vaccines and evaluation of a NRRV was the first research project in this dissertation. Three doses of a novel parenterally administered nanoparticle-based RV vaccine, P24-VP8*, adjuvanted with Al(OH)3 adjuvant, was able to prime VP8*-specific mucosal and systemic T cell responses (IFN-γ producing CD4+ and CD8+ T cells), and to induce strong systemic B cell responses (IgA, IgG and serum neutralizing antibodies). A significant reduction in the mean diarrhea duration, fecal virus shedding titers, and significantly lower fecal cumulative consistency scores was observed among vaccinated pigs demonstrating the efficacy of the vaccine against RV infection and diarrhea. Next, we determined the median infectious dose (ID50) and median diarrhea dose (DD50) of the GII.4/2003 Cin-1 variant of HuNoV in Gn pigs to better standardize the pig model for HuNoV vaccine evaluation. Gn pigs were inoculated with 7 different doses of Cin-1 at 33-34 days of age. Pigs were monitored daily from post-inoculation day (PID) 1 to 7, for fecal virus shedding and fecal consistency to evaluate the virus infectiousness and associated diarrhea. The Log10 ID50 and DD50 were determined based on various mathematical models to be between 3.11 to 3.76, and 3.37 to 4.87 RNA copies, respectively. The Beta-Poisson was identified to be the best-fitting statistical model for estimating both the ID50 and DD50 of Cin-1. Determining the ID50 of the challenge virus strain is crucial for identifying the true infectiousness of HuNoVs and for accurate evaluation of protective efficacies in pre-clinical studies of therapeutics, vaccines and other prophylactics using this reliable animal model. The lack of an easily reproducible cell culture model for HuNoV has significantly delayed the development of effective vaccines. There is still no HuNoV vaccine available. Currently, the vaccine development efforts are mostly based on genetically engineered virus-like particles (VLPs) comprised of the major HuNoV capsid protein VP1. We tested the immunogenicity of a novel tetravalent VLP vaccine containing 4 major HuNoV genotypes (GI.1, GII.3, GII.4 and GII.17) using Gn pigs and evaluated its protective efficacy when challenged with GII.4 Cin-1 HuNoV. Three doses of the VLP vaccine with Al(OH)3 adjuvant administered to Gn pigs intramuscularly (IM), induced high levels of VLP-specific serum IgA and IgG antibody and hemagglutination inhibition antibody responses in the vaccinated pigs. VLP-specific IFN-γ producing CD4+ and CD8+ T cells were also elevated among vaccinated pigs at post-challenge day (PCD) 7 in the spleen and blood, but not in the ileum. However, the vaccinated pigs were not protected from infection and diarrhea when challenged with any one of the three different doses (2 x 105, 8 x 104, and 2 x 104 genome RNA copies) of Cin-1 HuNoV. These results indicated that the IM tetravalent VLP vaccine was highly immunogenic, but the presence of high levels of immune effectors induced by the vaccine were not sufficient for protecting the Gn pigs from Cin-1 challenge. Amino acid (aa) sequence analysis showed that the GII.4 Sydney 2012 strain which was included in the VLP vaccine, had 23 aa substitutions in the major receptor binding domain (P2) compared to the Cin-1, a GII.4 Farmington Hills 2002 strain. Our findings, for the first time, provided in vivo experimental evidence for the total lack of cross-genogroup, cross-genotype and cross-variant protection among HuNoV. This finding has importance implications for HuNoV vaccine development. HuNoV vaccines have to include multiple variants and have to be routinely updated in order to ensure sustained protection among the population. Together these three studies in this dissertation demonstrate the versatility of Gn pigs as a reliable large animal model for studying the pathogenesis and immunity of enteric viruses and the evaluation of immunogenicity and protective efficacy of novel enteric viral vaccines. / Doctor of Philosophy / People of all age groups are susceptible to acute gastroenteritis (AGE), a condition characterized by sudden onset of diarrhea, nausea and abdominal cramps. The two most important viral pathogens responsible for causing AGE are rotavirus (RV) and norovirus (NoV). Gnotobiotic (Gn) pigs have been valuable in helping us understand the mechanism of infection, pathogenesis, immunity and have played a key role in the expediting development of novel vaccines and therapeutics against both of these viruses. Live oral RV vaccines are available but they are not very effective in low income countries where the vaccines are needed the most. Next generation parenteral vaccines are proposed to improve the RV vaccine efficacy. Our first study showed that a nanoparticle-based intramuscular (IM) RV vaccine effectively reduced the duration and severity of human RV infection and diarrhea in Gn pigs. Secondly, we examined in detail the infectivity of HuNoV and identified accurately using different mathematical models on how much virus would be required to infect and cause diarrhea in naïve Gn pigs. This knowledge would greatly help in the accurate assessment of the efficacy of NoV vaccines. Third, we evaluated the immunogenicity and protective efficacy of a tetravalent IM NoV vaccine in Gn pigs. Although the vaccine was highly immunogenic, it did not confer any protection against infection and diarrhea upon challenge with the NoV at different doses. NoVs are so diverse that one year we might be infected with one strain and a few years later, we might be infected again with another strain, even though they belong to the same genotype, and experience the same symptoms. This is because, changes brought about due to mutation in the virus capsid protein allow the viruses to hide from neutralizing antibodies induced by previous infection or vaccination as we have revealed in this study. NoV diversity and lack of cross protection need to be taken into consideration during vaccine development. This thesis shows how Gn pigs can be used to study these components in order to further maximize our ability to understand and combat enteric viral diseases.

The soldier's diet in the Civil War has been known as poor, and a number of illnesses and disorders have been associated with it. However, a nutritional analysis placed within the context of mid-nineteenth century American nutrition has been lacking. Such an approach makes clear the connection between illness and diet during the war for the average soldier and defines the importance of nutrition's role in the war. It also provides a bridge from the American diet to the soldier diet, outlining correlations between the two and examining the influence of physicians, chemists, and health reformers on the Civil War diet. / Master of Arts

The effect of orally administered duodenal contents on preventing diarrhea in neonatal calves challenged with enteropathogenic E. coli was studied in a 3 x 2 factorial experiment with five replications. Newborn calves received either 0 or 200 ml of intestinal fluid inoculum, obtained from older milk-fed calves, 2 h after entering the isolation facility. Colostrum was consumed following inoculum administration. The uninoculated calves received colostrum 2 h after entering the isolation facility. In compliance with the 3 x 2 factorial arrangement, two-thirds of the calves received an E. coli challenge 12 or 24 h after colostrum feeding. The remaining calves were unchallenged. Raw milk was fed at the rate of 10 percent of body weight per day. All experimental calves were observed daily for physical condition, percent dry matter of feces, urine output, rectal temperature, and dietary intake. Body weight and packed cell volume (PCV) were determined every third day. Gamma globulin per 100 ml serum was determined at 24 h of age. The inoculum was assayed microbiologically for total anaerobes, anaerobic lactobacilli, total aerobes, coliforms, and aerobic lactobacilli. Twelve calves were slaughtered at seven days of age to determine microbiological populations of the duodenal tissue and digesta. During the first six days of life calves receiving the inoculum exhibited a lower incidence of diarrhea, greater daily urine output, lower PCV, and superior average daily gain as compared to the uninoculated calves. The incidence of diarrhea and its accompanying symptoms were most severe in uninoculated calves challenged at 12 h. Rectal temperature was not affected by treatment. The differences in response to the challenge between inoculated and uninoculated calves for the complete experimental period were similar, but not as great as during the first six days of life. Serum gamma globulin at 24 h of age was abnormally low in inoculated calves. Uninoculated calves possessed normal levels of serum gamma globulin. Bacterial populations of duodenal tissue and fluid of seven day old calves were not influenced by treatment. / M.S.

Porcine epidemic diarrhea Virus (PEDV) is a virus effecting swine. It is the cause of disease that manifests with symptoms ranging from depression, to severe dehydration and death. Young piglets are particularly susceptible to the virus, which can reach mortality rates of 100%. Presence of the virus on a swine farm can therefore cause severe economic losses. Treatments currently exist for PEDV, but are mostly generated from the virus itself. There has recently been renewed interest in a vaccine that is made from a different source, which might help eliminate some of the side effects of those that currently exist on the market. This project outlines three experiments performed in animals. During the first experiment, a structural protein from the Hepatitis B virus was genetically altered to include important structural portions of PEDV. This new protein is generated in E. coli and purified. After purification, the protein assembles into a virus-like particle (VLP). VLPs are structural proteins of existing viruses that are expressed and assembled to mimic the virus. By doing so, the immune system recognizes the protein as a potential threat, and launches a response in the form of antibodies. Manipulations of the VLPs as describe herein allow the new vaccine to generate antibodies toward other diseases such as PEDV. Although all five of the vaccines used in the first experiment were able to generate appropriate antibodies, only two of them were effective at preventing PEDV from entering susceptible cells (virus neutralization). A second experiment, with three newly designed vaccines was therefore performed. This experiment, like the first, was successful in producing antibodies to several of the included PEDV protein sections, but none were able to neutralize the virus. These results led to a third experiment, during which further design improvements were made to the basic vaccine structure in an attempt to increase the neutralization capabilities of the vaccines. The results from the third experiment indicated that several changes to the vaccine increased the immune response to the structural portions of PEDV, providing a better overall vaccine candidate. This also led to the conclusion that one specific sequence from PEDV has a better ability to neutralize the virus than the other sections. / PHD / Porcine epidemic diarrhea Virus (PEDV) is a virus effecting swine. It is the cause of disease that manifests with symptoms ranging from depression, to severe dehydration and death. Young piglets are particularly susceptible to the virus, which can reach mortality rates of 100%. Presence of the virus on a swine farm can therefore cause severe economic losses. Treatments currently exist for PEDV, but are mostly generated from the virus itself. There has recently been renewed interest in a vaccine that is made from a different source, which might help eliminate some of the side effects of those that currently exist on the market. This project outlines three experiments performed in animals. During the first experiment, a structural protein from the Hepatitis B virus was genetically altered to include important structural portions of PEDV. This new protein is generated in E. coli and purified. After purification, the protein assembles into a virus-like particle (VLP). VLPs are structural proteins of existing viruses that are expressed and assembled to mimic the virus. By doing so, the immune system recognizes the protein as a potential threat, and launches a response in the form of antibodies. Manipulations of the VLPs as describe herein allow the new vaccine to generate antibodies toward other diseases such as PEDV. Although all five of the vaccines used in the first experiment were able to generate appropriate antibodies, only two of them were effective at preventing PEDV from entering susceptible cells (virus neutralization). A second experiment, with three newly designed vaccines was therefore performed. This experiment, like the first, was successful in producing antibodies to several of the included PEDV protein sections, but none were able to neutralize the virus. These results led to a third experiment, during which further design improvements were made to the basic vaccine structure in an attempt to increase the neutralization capabilities of the vaccines. The results from the third experiment indicated that several changes to the vaccine increased the immune response to the structural portions of PEDV, providing a better overall vaccine candidate. This also led to the conclusion that one specific sequence from PEDV has a better ability to neutralize the virus than the other sections.

Human noroviruses (HuNoVs) are the leading cause of viral epidemic acute gastroenteritis and responsible for the deaths of over 200,000 children each year worldwide. HuNoV research has been hampered by the long absence of a readily reproducible cell culture system and a suitable small animal model, while gnotobiotic (Gn) pigs have been a unique animal model for understanding HuNoV pathogenesis and immunity, as well as evaluating vaccine and therapeutics. Recent reports of HuNoVs infection and replication in B cells supplemented with commensal bacteria Enterobacter cloacae and in Blab/c mice deficient in RAG/IL2RG have gained extensive attention, and my studies utilized the well-established Gn pig model to investigate the effects of these two interventions on HuNoV infection. Surprisingly, the colonization of E. cloacae inhibited HuNoV infectivity in Gn pigs, evidenced by the significantly reduced HuNoV shedding in feces and HuNoV titers in intestinal tissues and blood compared to control pigs. Moreover, HuNoV infection of enterocytes but not B cells was observed with or without E. cloacae colonization, indicating B cells were not a target cell type for HuNoV in Gn pigs. On the other hand, using RAG2/IL2RG deficient pigs generated by CRISPR/Cas9 system, with confirmed severe combined immunodeficiency, I evaluated the effects of host immune responses on HuNoV infection. Compared to wild-type Gn pigs, longer HuNoV shedding was observed in RAG2/IL2RG deficient pigs (16 versus 27 days), and higher HuNoV titers were detected in intestinal tissues and contents and in blood, indicating increased and prolonged HuNoV infection in RAG2/IL2RG deficient pigs. In addition, I evaluated dietary interventions including probiotics and rice bran using Gn pig model of HuNoV infection and diarrhea. While the colonization of probiotic bacteria Lactobacillus rhamnosus GG (LGG) and Escherichia coli Nissle 1917 (EcN) in Gn pigs completely inhibited HuNoV fecal shedding, the two cocktail regimens, in which rice bran feeding started either 7 days prior to or 1 day after viral inoculation in the LGG+EcN colonized Gn pigs, exhibited dramatic anti-HuNoV effects, including reduced incidence and shorter duration of diarrhea, as well as shorter duration of virus fecal shedding. The anti-HuNoV effects of the cocktail regimens were associated with the enhanced IFN-𝛾⁺ T cell responses, increased production of intestinal IgA and IgG, and longer villus length. Taken together, my dissertation work improves our understanding of HuNoV infection and immunity, and further supports for Gn pigs as a valuable model for future studies of human enteric virus infection, host immunity, and interventions. / Ph. D. / Human noroviruses (HuNoVs) are the leading cause of viral epidemic acute gastroenteritis. Using the gnotobiotic pig model of HuNoV infection and diarrhea, we found that (1) the colonization of a commensal bacterium E. cloacae inhibited HuNoV infectivity, and B cells were not a target cell type for HuNoV in gnotobiotic pigs. (2) Increased and prolonged HuNoV infection in RAG2/IL2RG deficient pigs, which had severe combined immunodeficiency. (3) The dietary supplementation of rice bran and colonization of two probiotic bacteria significantly reduced HuNoV infectivity and diarrhea, and the beneficial effects were associated with enhanced intestinal immunity and health. Taken together, the dissertation work improves our understanding of HuNoV infection and immunity, and further supports for gnotobiotic pigs as a valuable model for future studies of human enteric virus infection, host immunity, and interventions.

Human rotavirus (HRV) is a major causative agent of acute gastroenteritis (AGE), which causes severe dehydrating diarrhea in children under the age of five and results in up to 215,000 deaths worldwide each year. There are two live oral attenuated vaccines licensed for use in the United States that are highly effective in high-income countries but much less so in low-and middle-income countries (LMICs). Several factors contributing to decreased efficacy in these areas include chronic malnutrition, gut dysbiosis, and concurrent viral infection. Along with this, currently used vaccines require constant cold-chain storage to maintain vaccine stability, and those resources can be scarce in LMICs. These areas continue to maintain a high burden of HRV morbidity and mortality, and more efficacious vaccines are needed. The gnotobiotic (Gn) pig model of HRV infection and diarrhea has long been used in the evaluation of novel HRV vaccines due to Gn pigs' susceptibility to HRV infection, development of clinical signs, histopathological changes in the intestine, and the infection kinetics that mimic those seen in human infants. The first project in this dissertation used the Gn pig model to evaluate a thermostable live oral attenuated vaccine administered as a dissolvable film. Two doses of the tetravalent dissolvable film vaccine conferred significant protection from virus shedding by delaying its onset and reducing peak titers in feces. It also significantly delayed the onset of diarrhea and reduced the duration and area under the curve (AUC) of diarrhea. The dissolvable film was highly immunogenic, inducing high titers of serum virus neutralizing (VN) antibodies specific to each of the four G-types included in the vaccine formulation, HRV-specific serum IgA and IgG, and intestinal IgA. These data confirm the thermostable platform as a useful alternative to liquid vaccines that require cold-chain. The second project evaluated three mRNA-based nonreplicating vaccine candidates in the Gn pig model. All three mRNA candidates encoded a universal CD4+ T cell epitope, P2, derived from tetanus toxoid, fused with the encoded VP8* from P[4], P[6], and P[8] HRVs. Two candidates also encoded for a lumazine synthase (LS) domain fused with the P2-VP8*. A dose response study of the LS-P2-VP8* candidates was conducted simultaneously. Significant protection against virus shedding was induced by all three candidates, with LS-P2-VP8* candidates inducing significantly higher VP8*-specific serum IgG. All three candidates induced significantly higher numbers of P[8]-VP8*-specific IgG antibody-secreting cells (ASCs) and IFN-γ-producing T cells in the ileum, spleen and blood. These data provide guidance for further development of the relatively new mRNA-based technology for use in HRV vaccine development. In the final study of this dissertation, we used the Gn pig model of both P[8] and P[6] HRV infection to evaluate a cocktail nanoparticle-based HRV vaccine. This vaccine was made up of an S60 nanoparticle, self-assembled from the S domain of the human norovirus capsid protein. The exposed C-termini on the S60 nanoparticle were utilized as an antigen display platform, where VP8* from P[4], P[6] and P[8] HRVs was fused. This vaccine was tested as both a two-dose intramuscular (IM) regimen, or as an IM booster preceded by an oral priming immunization with commercial monovalent Rotarix®. Pigs were challenged with either P[6] or P[8] HRV to evaluate cross-protection of the nanoparticle vaccine. Both regimens were highly immunogenic, inducing high titers of serum VN, IgG and IgA antibodies. Furthermore, the prime-boost regimen conferred significant protection against virus shedding in P[8] HRV-challenged pigs as evidenced by the shortened duration of fecal virus shedding. There was also significant protection in P[6] HRV-challenged pigs vaccinated with the prime-boost regimen, as evidenced by the shortened duration, reduced mean peak titer and AUC of virus shedding. Prime-boost-vaccinated pigs challenged with P[8] HRV had significantly higher P[8]-specific IgG ASCs in the spleen post-challenge. Prime-boost-vaccinated pigs challenged with P[6] HRV had significantly higher numbers of P[6] and P[8]-specific IgG ASCs in the ileum, as well as significantly higher numbers of P[8]-specific IgA ASCs in the spleen post-challenge. Oral priming followed by parenteral boosting appears to be a promising vaccination strategy for HRV and these data warrant further investigation into this regimen. Through these studies, we improved our understanding of the effect of different vaccination routes and formulations in the effectiveness of conferring protection against an enteric virus. The knowledge will facilitate the development of more effective vaccination strategies against HRV, the leading cause of infantile diarrhea in LMICs, as well as other enteric viruses. / Doctor of Philosophy / Human rotavirus (HRV) is a major causative agent of acute gastroenteritis (AGE) in children under the age of five. Acute gastroenteritis is characterized by nausea, vomiting, and potentially deadly dehydrating diarrhea. There are two highly effective vaccines licensed for use in the United States; however, these vaccines are much less effective in low- and middle-income countries (LMICs), where HRV disease burden is the highest. There are several reasons thought to be responsible for the decrease in effectiveness seen in these areas, including chronic malnutrition and gut dysbiosis. Non-biological reasons for decreased efficacy may include the breakdown of cold-chain storage for these vaccines, which require constant low temperature storage that is often unavailable in LMICs. Thermostable vaccines are necessary for increasing vaccine distribution and efficacy in these areas. Because many of the biologic factors thought to interfere with the effectiveness of these vaccines appear to be confined to the gastrointestinal tract, development of next generation HRV vaccines has focused on the parenteral route of administration. The gnotobiotic (Gn) pig model is a highly relevant animal model that has been used for decades to evaluate novel HRV vaccine efficacy. Our first study evaluated a thermostable, dissolvable live oral vaccine administered as a dissolvable film in our Gn pig model. Two doses of this vaccine significantly reduced the severity of diarrhea and virus shedding in the stool. Our second study evaluated three mRNA-based intramuscular (IM) vaccines in the Gn pig model. Three doses of all mRNA candidates provided significant protection from virus shedding in the stool, as well as inducing the production of strong HRV-specific antibodies in the serum and high numbers of virus-specific T cells in the tissues. In our final study, we evaluated a nanoparticle-based vaccine as a two-dose IM regimen or as an IM booster preceded by an oral immunization using the commercially available Rotarix® vaccine. The prime-boost regimen significantly shortened the duration and severity of virus shedding in the stool. We also detected more cross-strain HRV-specific antibody-secreting cells in the tissues. All three vaccines evaluated in this dissertation offer differing novelty in the field of HRV vaccine development, and the Gn pig model has been instrumental in the evaluation of these vaccines.

<i>Escherichia coli </i> remains a significant cause of diarrhea worldwide and in recent years a relatively high number of E. coli carrying gene for AIDA-I (adhesin involved in diffuse adherence) has been isolated from cases of neonatal and post-weaning diarr<i>Escherichia coli</i> remains a significant cause of diarrhea worldwide and in recent years a relatively high number of <i>E. coli</i> carrying gene for AIDA-I (adhesin involved in diffuse adherence) has been isolated from cases of neonatal and post-weaning diarrhea in pigs. AIDA-I adhesin and its gene aidA were first identified and characterized in <i>E. coli</i> isolated from a human case of infantile diarrhea. Recent studies have demonstrated a significant degree of homology between the AIDA-I adhesin isolated from porcine neonatal diarrheagenic <i>E. coli</i> isolates and that from a human <i>E. coli</i> isolate; however, the role of AIDA-I adhesin in the pathogenesis of diarrhea and the clinical significance of the AIDA-I <i>E. coli</i> virotype are unknown in humans or in animals. <p>First, in order to evaluate the role of AIDA-I adhesin, colostrum deprived newborn pigs were infected with: i) a wild strain PD20 (AIDA-I+/STb+) <i>E. coli</i>; ii) a mutant strain PD20M (AIDA-I-/STb+), generated by partial deletion of the aidA gene from the wild strain, iii) a complemented strain PD20C (AIDA-I+/STb+), generated by reintroducing the full length aidA gene into PD20M strain, and iv) a nonpathogenic <i>E. coli</i> strain PD71 used as negative control. Pigs infected with wild type (PD20) and complemented (PD20C) strains developed diarrhea between 15-19 h and 27-31 h after oral inoculation, respectively, in contrast to pigs infected with strains PD20M or PD71 that did not developed diarrhea. Intestinal colonization was evaluated by histology, imunohistochemistry (IHC), transmission electron microscopy (TEM), including immunogold electron microscopy (IGEM), and showed heavy bacterial colonization with biofilm formation in the large intestine with AIDA-I+ strains (PD20 and PD20C), but not in pigs infected with AIDA-I- strains (PD20M and PD71). In vitro assays showed marked diffuse adherence to HeLa cells, enhanced bacterial autoaggregation and significant biofilm formation by AIDA-I+ strains, when compared to AIDA-I- strains.<p>Second, 110 F4 negative <i>E. coli</i> isolates from problematic cases of diarrhea in pigs were subjected to multiplex polymerase chain reaction (M-PCR) for detection of the genes encoding the virulence factors F4, F5, F6, F18, F41, AIDA-I, EAE, STa, STb, LT, EAST1 and Stx2e. In this study, the prevalence of aidA gene among the 110 isolates was 8.2%, and the aidA gene was shown to be associated most commonly with EAST1 and STb genes. The genes for the F4, F5, F6 and F41 fimbriae were absent in all the AIDA-I+ <i>E. coli</i> isolates. <p>The clinical significance of the AIDA-I+ <i>E. coli</i> was studied using clinical data available for 35 of the 110 <i>E. coli</i> isolates, originating from 18 cases of diarrhea. Among these 18 diarrhea cases, 3 cases (5 isolates) were found to have AIDA-I+ <i>E. coli</i> and these were significantly associated with diarrhea cases of post-weaning age group. Enterotoxigenic <i>E. coli</i> strains were isolated from the majority (72.5%) of 18 diarrhea cases and a high proportion (23.1%) of these ETEC cases carried AIDA-I+ <i>E. coli</i>. <p>In conclusion, AIDA-I adhesin appears to be a significant virulence factor for intestinal colonization and induction of biofilm formation. Further, experimental studies and clinical data suggest that the AIDA-I/STb virotype may be important in the pathogenesis of pre-weaning and post-weaning diarrhea in pigs. Our results suggest that AIDA-I may play a significant role in the development of diarrhea in pigs. .hea in pigs. AIDA-I adhesin and its gene aidA were first identified and characterized in E. coli isolated from a human case of infantile diarrhea. Recent studies have demonstrated a significant degree of homology between the AIDA-I adhesin isolated from porcine neonatal diarrheagenic E. coli isolates and that from a human E. coli isolate; however, the role of AIDA-I adhesin in the pathogenesis of diarrhea and the clinical significance of the AIDA-I E. coli virotype are unknown in humans or in animals. First, in order to evaluate the role of AIDA-I adhesin, colostrum deprived newborn pigs were infected with: i) a wild strain PD20 (AIDA-I+/STb+) E. coli; ii) a mutant strain PD20M (AIDA-I-/STb+), generated by partial deletion of the aidA gene from the wild strain, iii) a complemented strain PD20C (AIDA-I+/STb+), generated by reintroducing the full length aidA gene into PD20M strain, and iv) a nonpathogenic E. coli strain PD71 used as negative control. Pigs infected with wild type (PD20) and complemented (PD20C) strains developed diarrhea between 15-19 h and 27-31 h after oral inoculation, respectively, in contrast to pigs infected with strains PD20M or PD71 that did not developed diarrhea. Intestinal colonization was evaluated by histology, imunohistochemistry (IHC), transmission electron microscopy (TEM), including immunogold electron microscopy (IGEM), and showed heavy bacterial colonization with biofilm formation in the large intestine with AIDA-I+ strains (PD20 and PD20C), but not in pigs infected with AIDA-I- strains (PD20M and PD71). In vitro assays showed marked diffuse adherence to HeLa cells, enhanced bacterial autoaggregation and significant biofilm formation by AIDA-I+ strains, when compared to AIDA-I- strains. Second, 110 F4 negative E. coli isolates from problematic cases of diarrhea in pigs were subjected to multiplex polymerase chain reaction (M-PCR) for detection of the genes encoding the virulence factors F4, F5, F6, F18, F41, AIDA-I, EAE, STa, STb, LT, EAST1 and Stx2e. In this study, the prevalence of aidA gene among the 110 isolates was 8.2%, and the aidA gene was shown to be associated most commonly with EAST1 and STb genes. The genes for the F4, F5, F6 and F41 fimbriae were absent in all the AIDA-I+ E. coli isolates. The clinical significance of the AIDA-I+ E. coli was studied using clinical data available for 35 of the 110 E. coli isolates, originating from 18 cases of diarrhea. Among these 18 diarrhea cases, 3 cases (5 isolates) were found to have AIDA-I+ E. coli and these were significantly associated with diarrhea cases of post-weaning age group. Enterotoxigenic E. coli strains were isolated from the majority (72.5%) of 18 diarrhea cases and a high proportion (23.1%) of these ETEC cases carried AIDA-I+ E. coli. In conclusion, AIDA-I adhesin appears to be a significant virulence factor for intestinal colonization and induction of biofilm formation. Further, experimental studies and clinical data suggest that the AIDA-I/STb virotype may be important in the pathogenesis of pre-weaning and post-weaning diarrhea in pigs. Our results suggest that AIDA-I may play a significant role in the development of diarrhea in pigs.

<i>Escherichia coli </i> remains a significant cause of diarrhea worldwide and in recent years a relatively high number of E. coli carrying gene for AIDA-I (adhesin involved in diffuse adherence) has been isolated from cases of neonatal and post-weaning diarr<i>Escherichia coli</i> remains a significant cause of diarrhea worldwide and in recent years a relatively high number of <i>E. coli</i> carrying gene for AIDA-I (adhesin involved in diffuse adherence) has been isolated from cases of neonatal and post-weaning diarrhea in pigs. AIDA-I adhesin and its gene aidA were first identified and characterized in <i>E. coli</i> isolated from a human case of infantile diarrhea. Recent studies have demonstrated a significant degree of homology between the AIDA-I adhesin isolated from porcine neonatal diarrheagenic <i>E. coli</i> isolates and that from a human <i>E. coli</i> isolate; however, the role of AIDA-I adhesin in the pathogenesis of diarrhea and the clinical significance of the AIDA-I <i>E. coli</i> virotype are unknown in humans or in animals. <p>First, in order to evaluate the role of AIDA-I adhesin, colostrum deprived newborn pigs were infected with: i) a wild strain PD20 (AIDA-I+/STb+) <i>E. coli</i>; ii) a mutant strain PD20M (AIDA-I-/STb+), generated by partial deletion of the aidA gene from the wild strain, iii) a complemented strain PD20C (AIDA-I+/STb+), generated by reintroducing the full length aidA gene into PD20M strain, and iv) a nonpathogenic <i>E. coli</i> strain PD71 used as negative control. Pigs infected with wild type (PD20) and complemented (PD20C) strains developed diarrhea between 15-19 h and 27-31 h after oral inoculation, respectively, in contrast to pigs infected with strains PD20M or PD71 that did not developed diarrhea. Intestinal colonization was evaluated by histology, imunohistochemistry (IHC), transmission electron microscopy (TEM), including immunogold electron microscopy (IGEM), and showed heavy bacterial colonization with biofilm formation in the large intestine with AIDA-I+ strains (PD20 and PD20C), but not in pigs infected with AIDA-I- strains (PD20M and PD71). In vitro assays showed marked diffuse adherence to HeLa cells, enhanced bacterial autoaggregation and significant biofilm formation by AIDA-I+ strains, when compared to AIDA-I- strains.<p>Second, 110 F4 negative <i>E. coli</i> isolates from problematic cases of diarrhea in pigs were subjected to multiplex polymerase chain reaction (M-PCR) for detection of the genes encoding the virulence factors F4, F5, F6, F18, F41, AIDA-I, EAE, STa, STb, LT, EAST1 and Stx2e. In this study, the prevalence of aidA gene among the 110 isolates was 8.2%, and the aidA gene was shown to be associated most commonly with EAST1 and STb genes. The genes for the F4, F5, F6 and F41 fimbriae were absent in all the AIDA-I+ <i>E. coli</i> isolates. <p>The clinical significance of the AIDA-I+ <i>E. coli</i> was studied using clinical data available for 35 of the 110 <i>E. coli</i> isolates, originating from 18 cases of diarrhea. Among these 18 diarrhea cases, 3 cases (5 isolates) were found to have AIDA-I+ <i>E. coli</i> and these were significantly associated with diarrhea cases of post-weaning age group. Enterotoxigenic <i>E. coli</i> strains were isolated from the majority (72.5%) of 18 diarrhea cases and a high proportion (23.1%) of these ETEC cases carried AIDA-I+ <i>E. coli</i>. <p>In conclusion, AIDA-I adhesin appears to be a significant virulence factor for intestinal colonization and induction of biofilm formation. Further, experimental studies and clinical data suggest that the AIDA-I/STb virotype may be important in the pathogenesis of pre-weaning and post-weaning diarrhea in pigs. Our results suggest that AIDA-I may play a significant role in the development of diarrhea in pigs. .hea in pigs. AIDA-I adhesin and its gene aidA were first identified and characterized in E. coli isolated from a human case of infantile diarrhea. Recent studies have demonstrated a significant degree of homology between the AIDA-I adhesin isolated from porcine neonatal diarrheagenic E. coli isolates and that from a human E. coli isolate; however, the role of AIDA-I adhesin in the pathogenesis of diarrhea and the clinical significance of the AIDA-I E. coli virotype are unknown in humans or in animals. First, in order to evaluate the role of AIDA-I adhesin, colostrum deprived newborn pigs were infected with: i) a wild strain PD20 (AIDA-I+/STb+) E. coli; ii) a mutant strain PD20M (AIDA-I-/STb+), generated by partial deletion of the aidA gene from the wild strain, iii) a complemented strain PD20C (AIDA-I+/STb+), generated by reintroducing the full length aidA gene into PD20M strain, and iv) a nonpathogenic E. coli strain PD71 used as negative control. Pigs infected with wild type (PD20) and complemented (PD20C) strains developed diarrhea between 15-19 h and 27-31 h after oral inoculation, respectively, in contrast to pigs infected with strains PD20M or PD71 that did not developed diarrhea. Intestinal colonization was evaluated by histology, imunohistochemistry (IHC), transmission electron microscopy (TEM), including immunogold electron microscopy (IGEM), and showed heavy bacterial colonization with biofilm formation in the large intestine with AIDA-I+ strains (PD20 and PD20C), but not in pigs infected with AIDA-I- strains (PD20M and PD71). In vitro assays showed marked diffuse adherence to HeLa cells, enhanced bacterial autoaggregation and significant biofilm formation by AIDA-I+ strains, when compared to AIDA-I- strains. Second, 110 F4 negative E. coli isolates from problematic cases of diarrhea in pigs were subjected to multiplex polymerase chain reaction (M-PCR) for detection of the genes encoding the virulence factors F4, F5, F6, F18, F41, AIDA-I, EAE, STa, STb, LT, EAST1 and Stx2e. In this study, the prevalence of aidA gene among the 110 isolates was 8.2%, and the aidA gene was shown to be associated most commonly with EAST1 and STb genes. The genes for the F4, F5, F6 and F41 fimbriae were absent in all the AIDA-I+ E. coli isolates. The clinical significance of the AIDA-I+ E. coli was studied using clinical data available for 35 of the 110 E. coli isolates, originating from 18 cases of diarrhea. Among these 18 diarrhea cases, 3 cases (5 isolates) were found to have AIDA-I+ E. coli and these were significantly associated with diarrhea cases of post-weaning age group. Enterotoxigenic E. coli strains were isolated from the majority (72.5%) of 18 diarrhea cases and a high proportion (23.1%) of these ETEC cases carried AIDA-I+ E. coli. In conclusion, AIDA-I adhesin appears to be a significant virulence factor for intestinal colonization and induction of biofilm formation. Further, experimental studies and clinical data suggest that the AIDA-I/STb virotype may be important in the pathogenesis of pre-weaning and post-weaning diarrhea in pigs. Our results suggest that AIDA-I may play a significant role in the development of diarrhea in pigs.

MSc (Microbiology) / Department of Microbiology / See the attached abstract below