Thesis (Ph.D.)--Memorial University of Newfoundland, 2005. / Includes bibliographical references.

Diss. (sammanfattning) Umeå : Univ., 2005. / Härtill 5 uppsatser.

Thesis (M.S.)---University of Nevada, Reno, 2001. / Includes bibliographical references. Online version available on the World Wide Web.

Master of Science in Biomedical Sciences / Department of Diagnostic Medicine/Pathobiology / Weiping Zhang / Heat-labile enterotoxin (LT) is one of the most important toxins produced by enterotoxigenic Escherichia coli (ETEC). It consists of one A subunit (LTA) for intracellular enzymatic activity and five B subunits (LTB) forming a pentamer for binding to host cell receptors. In the last few decades, LT has been extensively studied as a strong immune stimulator, as well as an effective adjuvant with multiple immunomodulatory properties. To understand better the features of LT, we mapped B-cell linear epitopes of the enzymatic A subunit and explored the relationship between these epitopes and the toxicity of LT. Eleven B-cell linear (continuous) epitopes were in silico identified based on online software. In part one of the study, all 11 epitopes were fused into a modified ovalbumin carrier protein respectively. Each recombinant fusion protein was expressed and purified, and was characterized in ELISA and Western Blot using the anti-LT serum. Moreover, each fusion protein was used to immunize mice to determine immune response specific to LT in vivo. A total of eleven epitopes were identified from the LTA subunit. Results showed that anti-LT serum recognized all 11 epitopes, while the mouse immunization study indicated that antibodies derived from epitope 7 (₁₀₅SPHPYEQEVSA₁₁₅) had significantly greater anti-LT antibody titers and neutralized LT enterotoxicity more efficiently than the other epitopes. In part two of the study, to test whether individual epitope plays a role in LT toxicity, 10 epitopes in the A1 domain of LTA subunit were replaced by a foreign peptide respectively and the mutant LTs were examined for enterotoxicity. Data indicated that all these LT mutants showed enterotoxicity abolished. However, these LT mutants formed holotoxin structure and bound to GM1 in vitro. Results from this study indicated that replacement of these LT epitopes did not affect the forming of LT holotoxin structure and the binding to host receptors, indicating LT can serve as a safe vaccine platform to carry foreign antigens. With the immunodominant epitope 7 being kept while other LTA epitopes replaced by epitopes from other ETEC virulence factors, this platform can be used to construct broadly protective multivalent mucosal vaccines against ETEC, and perhaps as a universal platform for vaccines against other enteric diseases.

and Key words This diploma thesis is focused on assessing the potential benefit of HLA epitopes for the prediction of de novo antibody production at kidney transplant recipients. The topic and patient selection criteria were selected in accordance with the 18th International HLA and Immunogenetics workshop (IHIWS), which is taking place in May 2022 in the Netherlands, where our data will also be contributed. Our aims were to compare HLA antigens mismatches (counted as total number of mismatched alleles) defined on the high-resolution level by NGS sequencing, HLA eplets mismatches defined by HLA matchmaker, and amino acid mismatches defined by HLA EMMA in their capacity to predict de novo antibody production and compare these results to other works by different authors from this field. We have identified N= 28 patients who developed de novo antibodies and N= 19 who didn't develop de novo antibodies in 5 years follow up their transplant. These two cohorts were compared based on all three approaches and correlation between number of mismatches and number of patients with de novo antibodies were made using ROC curves. Superiority of eplet mismatches over HLA antigen mismatches (total number of mismatched alleles) defined on high resolution was not detected. The HLA epitopes identified by the HLA...

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 5 uppsatser.

No description available.

Lipopolysaccharides (LPS), major virulence determinants in Gram–negative bacteria, are responsible for many pathophysiological responses and can elicit strong immune responses. In order to better understand the role of LPS in host–pathogen interactions and elucidate the immunogenic properties of LPS outer core oligosaccharide, an all α–linked Escherichia coli R3 outer core pentasaccharide was first synthesized with a propyl amino linker at the reducing end. This oligosaccharide was also covalently conjugated to a carrier protein (CRM197) via the reducing end propyl amino linker. An immunological analysis demonstrated that this glycoconjugate can elicit specific anti-pentasaccharide antibodies with in vitro bactericidal activity. These findings will contribute to further exploring this pentasaccharide antigen as a vaccine candidate. Human milk oligosaccharides (HMOs) are a family of diverse unconjugated glycans that exist in human milk as one of the major components. Characterization, quantification and biofunctional studies of HMOs remain a big challenge due to their diversity and complexity. The accessibility of homogenous HMOs library is essential to solve these issues which have beset academia for several decades. In this study, an efficient chemoenzymatic strategy, namely Core Synthesis/Enzymatic Extension (CSEE), for rapid production of diverse HMOs was reported. Based on 3 versatile building blocks and 4 robust glycosyltransferases, a library of 31 HMOs were chemoenzymatically synthesized and characterized by MS and NMR. CSEE indeed provides a practical approach to harvest structurally defined HMOs for various applications. Glycoproteins are extremely important for all life on the planet. Glycoproteins play important roles in various biological processes. Increasing evidences demonstrate that glycosylation of proteins could improve stability of proteins by stabilizing their tertiary structure and protecting them from proteolysis. Besides, glycosylation of proteins could provide targeting effects through glycan-lectin interaction. Furthermore, carbohydrates play crucial roles in humoral immunity in that many sugar epitopes are identified as antigens for antibodies. Glycoprotein could boost strong T cells mediated intercellular immune responses because homogeneous antigens present on the surface of proteins by multivalent bonds. In this study, the three advantages of glycoproteins, namely stabilizing proteins, targeting effects and eliciting immunological response, were extensively explored by broad collaboration with other groups.

Ph.D., Faculty of Health Sciences, University of the Witwatersrand, 2006. / Objectives. Autoantibodies to the 65kDa isoform of glutamic acid decarboxylase (GAD65Abs) are accepted markers for type 1 diabetes and, together with autoantibodies to insulin (IAA) and a protein tyrosine phosphatase-like islet cell antigen (IA-2), predict the disease. IAA are often the first autoantibodies detected in type 1 diabetics and can be present before the onset of clinical diabetes. These autoantibodies and their epitopes are however not well characterized. We explored the use of monoclonal antibodies and their recombinant Fab (rFab) as reagents for epitope analysis. Methods and Results. Four rFab specific for insulin were cloned from murine monoclonal antibodies (mAbs) 1E2, HB-126, HB-123, HB-127, and one rFab specific for GAD65 was cloned from human mAb IgG antibody DP-D (derived from autoimmune disease patients), to characterise insulin and GAD65 autoantibodies present in the sera of patients with type 1 diabetes. Only rFab 126 and DP-D showed insulin and GAD65 specific binding, respectively in radiobinding assays. In competition experiments with sera positive for autoantibodies to insulin the rFab 126 significantly reduced the binding to 125I-insulin by sera of type 1 (n=35) and type 1.5 diabetes (or LADA) (n=14) patients (p<0.0001). There was no difference in the competition pattern in IAA positive type 1 diabetes patients (n=35) and IAA positive type 1.5 diabetes patients (n=14). The insulin epitope that the rFab binds to was mapped using competitive radiobinding assays with two monoclonal antibodies (mAb 1 and mAb 125) whose epitopes are on the B chain and A chain loop of insulin, respectively. We found the epitope of this recombinant antibody to be located on the A chain loop of the insulin molecule. The 3-dimensional structure of rFab 123, 126 and DP-D were determined using an automated homology modelling programme. Using the computer programme ‘PatchDock’ we attempted to further map the epitope that rFab 126 binds to on insulin. Of the three models generated, only one supported our findings that rFab 126 binds to the A chain loop of insulin. The binding of GAD65Ab in 61 type 1 diabetes patients to GAD65 was analyzed by competitive radioimmunoassays with rFab DP-D to ascertain disease-specific GAD65Ab binding specificities. The median binding was reduced significantly by rFab DP-D (80%) (p<0.0001). The competition pattern in type 1 diabetes patients was different from that in GAD65Ab-positive type 1.5 diabetes patients (n=44), first degree relatives (n=38), and healthy individuals (n=14) (Padoa et al., 2003). Conclusions. We have shown that rFab specific for insulin and GAD65 can be generated using PCR technology and that such agents can be used to determine the insulin/GAD65 epitopes recognized by autoantibodies from type 1 and 1.5 diabetics. These novel findings with GAD65- and insulin-specific rFab support the view that type 1 diabetes is associated with disease- and epitope-specific GAD65- and insulin-autoantibodies and supports the notion that the middle epitope of GAD65 is disease-specific. These GAD65-specific rFab should prove useful in predicting type 1 diabetes. Furthermore, rFabs may be a novel method for blocking autoimmune responses against β cell autoantigens in type 1 diabetics.

As formulações vacinais contra o Vírus Respiratório Sincicial Humano, HRSV, estão associadas à indução de eosinofilia pulmonar mediada por uma resposta de células TCD4+ Th2, após exposição ao HRSV selvagem. Foi identificado um peptídeo da proteína viral G, que modificado perde a capacidade de predispor à eosinofilia, tornando-o um imunógeno atraente. Células T CD8+ específicas para HRSV reduzem a resposta Th2, mediam resistência a desafio com o vírus, e estão relacionadas à redução dos sintomas. Assim, neste trabalho buscamos e identificamos epítopos de células TCD8+ na polimerase viral, utilizando programas de predição, imunização com peptídeos e avaliação da resposta celular. Também construímos vacinas de DNA contendo a seqüência nucleotídica do peptídeo da proteína G modificado. A caracterização da resposta imune estimulada por essas vacinas e por peptídeos purificados revelou que o plasmídio pTGMCTB, bem como os peptídeos GM e GMCTB, foram capazes de induzir anticorpos que, porém, não se mostraram neutralizantes de HRSV e protetores frente a desafio. / Vaccines against human respiratory syncytial virus (HRSV) are associated with pulmonary eosinophilia induction mediated by a TCD4+ Th2 response, after exposition to wild HRSV. A peptide from the viral protein G was identified to predispose to eosinophilia and loses this ability when mutated, making it an interesting immunogen. CD8+ T cells specific to HRSV reduce the Th2 response, mediate resistance to virus challenge, and are related to symptom-reduction. Thus, in the present work, we searched for and identified CD8+ T cell epitopes in the viral polymerase; using prediction programs, peptide immunization and evaluation of the cellular response. We also constructed DNA vaccines containing the nucleotide sequence of the mutated peptide from G protein mentioned above. The characterization of the immune response elicited by these vaccines and purified peptides showed that the pTGMCTB plasmid, as well as GM and GMCTB peptides were able to induce antibody response; however they are not neutralizing and protective against HRSV challenge.