Die angeborene Immunität ist in der Lage, Pathogene schon beim erstmaligen Eindringen zu erkennen und zu bekämpfen. Haupteffektoren der schnellen, angeborenen Immunantwort sind Makrophagen und polymorphkernige neutrophile Granulozyten. Diese erkennen und phagozytieren Pathogene und koordinieren die weitere Immunantwort durch die Freisetzung von inflammatorischen Mediatoren und Zytokinen. Die Erkennung mikrobieller Bestandteile, wie Lipopolysaccharid (LPS) Gram-negativer Bakterien bzw. Peptidoglykan (PG) und Lipoteichonsäuren (LTA) Gram-positiver Bakterien, führt zur Aktivierung von unterschiedlichen Proteinkinasen, des Transkriptionsfaktors NF-(B und zur Freisetzung von Zytokinen. Mitglieder der Toll-Proteinfamilie, sogenannte Toll-like-Rezeptoren (TLR), wurden kürzlich als Rezeptoren auf Immunzellen identifiziert, die für die Erkennung solcher mikrobieller Bestandteile verantwortlich sind. Während TLR-4 der LPS-Erkennung dient, und TLR-2 und -6 verschiedene Liganden von Gram-positiven Bakterien binden, blieb die Frage der Erkennung von LTA und verwandten Glykolipiden strittig. Sowohl TLR-2 als auch TLR-4 wurden für diese Rolle diskutiert. Zielsetzung dieser Arbeit war, die Rolle von TLRs in der LTA- und Glykolipid-Erkennung zu untersuchten. Glykolipide von zwei eng verwandten Treponemen-Spezies, T. maltophilum (TM) und T. brennaborense (TB), sowie neuartig aufgereinigte Lipoteichonsäuren von Staphylococcus aureus (SA) und Bacillus subtilis (BS) wurden eingesetzt, um die nukleäre Translokation von NF-(B in verschiedenen Zellsystemen zu induzieren. Diese Zellstimulationsexperimente wurden mit verschiedenen TLR-2-negativen Zellinien sowie mit Peritonealexsudatzellen TLR-4-defizienter C3H/HeJ-Mäuse durchgeführt. Weitere Informationen lieferten TLR-2-Überexpressions-Experimente sowie Zellstimulationen unter Verwendung von anti-TLR-4-Antikörpern. Die Aktivierung von NF-(B wurde anhand von Gelshifts nachgewiesen. Mit der Überexpression von dominant-negativen Mutanten verschiedener Moleküle der Signalkaskade, mit Kinase-Hemmstoffen und mit Western Blots wurden die intrazellulären Signaltransduktionswege untersucht. Für Glykolipide von T. maltophilum und beide verwendeten Lipoteichonsäuren ließ sich eine klare TLR-2-Abhängigkeit in der Aktivierung von NF-(B und der Induktion von proinflammatorischen Zytokinen zeigen. Die Glykolipide von T. brennaborense hingegen waren überraschender Weise gleichzeitig auch TLR-4-Liganden. Beide untersuchten Glykolipide sowie beide LTAs aktivierten einen Signalweg unter Einbeziehung des Adaptermoleküls MyD88 und der NF-(B-induzierenden Kinase (NIK). Des weiteren konnte der Einfluß der MAP-Kinasen p42/44 und p38 auf die Treponema-Glykolipid- und LPS-induzierte TNF-(-Ausschüttung dargestellt werden. Zusammenfassend zeigen diese Ergebnisse, daß TLR-2 der Hauptrezeptor von Lipoteichonsäuren ist, und TLR-2 und -4 beide Rezeptoren der Treponema-Glykolipide sein können. Diese Ergebnisse sollten dazu beitragen, die molekularen Grundlagen der Reaktionen des Immunsystems auf Gram-positive Bakterien und Treponemen zu verstehen. / The innate immune response to microbial pathogens is able to protect the host after a first pathogen contact. This immediate immune response is largely mediated by macrophages and neutrophils. They recognize and phagocytose pathogens, and coordinate host responses by secreting inflammatory mediators, such as cytokines. The recognition of lipopolysaccharide (LPS) of Gram-negative bacteria, or peptidoglycan (PG) and lipoteichoic acids (LTAs) of Gram-positive bacteria leads to the induction of protein-kinases, the transcription factor NF-(B, and subsequently the release of proinflammatory cytokines. Recently, members of the Toll-protein-family, the so-called Toll-like receptors (TLRs) have been found to be involved in immune cell activation by microbial products. While TLR-4 has been identified as the transmembrane signal transducer for LPS, and TLR-2 and -6 for different ligands originating from Gram-positive bacteria, the molecular basis of recognition of lipoteichoic acids and related glycolipids has not been completely understood: Both, TLR-4 and -2 have been postulated as receptors. In order to determine the role of TLRs in immune cell activation by Treponema glycolipids and LTAs experiments involving TLR-2-negative cell lines, macrophages from TLR-4-deficient C3H/HeJ-mice, cells overexpression TLR-2, and inhibitory TLR-4 antibodies were performed. The induction of NF-(B was assessed by electrophoretic mobility shift assays. Glycolipids of two related Treponema species, T. maltophilum (TM) and T. brennaborense (TB), and LTAs from Staphylococcus aureus (SA) and Bacillus subtilis (BS) were investigated for induction of nuclear translocation of NF-(B in different cell systems. Glycolipids from T. maltophilum and both LTAs studied revealed TLR-2-dependency in induction of NF-(B and proinflammatory cytokines. Surprisingly, glycolipids from T. brennaborense were found to be TLR-4-ligands. Furthermore an involvement of the signaling molecules MyD88 and NIK in cell stimulation by LTAs and glycolipids was revealed by dominant-negative overexpression experiments. The induction of TNF-( by Treponema glycolipids furthermore was dependent on activation of MAP kinases p42/44 and p38, as indicated by specific kinase inhibitors. Tyrosinephosporylation of the p42/44 kinase induced by Treponema glycolipids were detected by western blots. In summary, the results presented here indicate that TLR-2 is the main receptor for LTAs. Both TLR-2 and -4 serve as receptors for Treponema glycolipids. These results may potentially contribute to explain immune responses to Gram-positive bacteria and treponemes.

Abscessos e granulomas periapicais são considerados lesões inflamatórias relacionadas a elementos dentários, com origem em infecções do tecido pulpar e periapical. É pouco conhecido o papel da interleucina 17 (IL-17) nessas lesões, uma citocina que participa ativamente de uma classe de resposta imunológica recentemente descrita, denominada Th17. A resposta Th17 tem sido caracterizada pela produção de IL-17 por linfócitos CD4+ e tem sido associada à instalação e perpetuação do processo inflamatório, bem como a intenso recrutamento de neutrófilos. Este estudo tem como foco investigar a expressão dessa citocina em lesões de abscesso e granuloma periapicais, com a intenção de verificar se há diferenças de expressão entre essas duas lesões, já que a presença de infiltrado neutrofílico difere bastante entre elas. Testes imuno-histoquímicos para IL-17, CD4 (para identificação de linfócitos T CD4+), CD8 (para identificação de linfócitos T CD8+) e elastase (para identificação de células inflamatórias polimorfonucleadas) foram realizados em casos de abscesso (n=25) e granuloma (n=25) periapicais, selecionados do acervo do Serviço de Patologia Cirúrgica da Disciplina de Patologia Bucal da FOUSP. Foi obtida a porcentagem da área de células com expressão positiva para os marcadores citados. Também foi realizada a quantificação de células CD4+/IL-17+ e CD8+/IL-17+ detectadas por imunofluorescência nessas mesmas biópsias. Foram realizados testes estatísticos de Friedman e Mann-Whitney, para se verificarem as diferenças entre as porcentagens de marcação imuno-histoquímica obtidas para o abscesso e o granuloma, bem como teste de correlação de Spearman, para se verificar se havia correlação entre a expressão de IL-17 e os demais marcadores. Nos casos de abscesso periapical, houve expressão intensa de elastase, seguida de IL-17 e CD8, cujas respectivas porcentagens de expressão não diferiram estatisticamente entre si, mas foram significativamente maiores do que a da expressão do CD4 (p<0,0001). No teste de correlação de Spearman, houve correlação positiva significante entre IL-17 e CD8 (rs = 0,5944, p=0,0415), mas não entre IL-17 e elastase e IL-17 e CD4. Na quantificação de células duplamente positivas pela técnica da imunofluorescência houve significantemente mais células CD4+/IL-17+ do que CD8+/IL-17+ (p=0,0250). Nos casos de granuloma periapical, observou-se que a porcentagem de área de marcação do CD4 foi significativamente maior em relação a da elastase (p=0,0055), do CD8 (p=0,0200) e da IL-17 (p=0,0210). Houve correlação positiva significativa entre IL-17 e elastase (rs = 0,5604, p=0,0463), mas não entre IL-17 e os demais marcadores. Na quantificação de células duplamente positivas pela técnica da imunofluorescência houve significância maior para células CD4+/IL-17 do que de células CD8+/IL-17+ (p=0,0470). Na comparação da porcentagem de área de marcação entre abscesso e granuloma, a porcentagem de IL-17 foi significativamente maior nos abscessos (p=0,0114). Concluiu-se que há maior expressão da IL-17 em abscessos do que em granulomas e que, nesses últimos, essa citocina é mais expressa quando há maior expressão de células polimorfonucleadas. Isso parece evidenciar a participação da resposta Th17 em fases agudas do processo inflamatório. Apesar de haver diferenças significativas entre as lesões quanto ao predomínio das subpopulações de linfócitos T, em ambas as lesões há maior co-expressão da IL-17 em linfócitos CD4+, indicando que provavelmente essa população linfocitária seja a principal responsável pela secreção dessa citocina nas lesões estudadas. / Periapical abscess and periapical granulomas are considered inflammatory lesions related to dental infections originated from pulpal and periodontal tissues. There is little information about the role of interleukin 17 (IL-17) on these lesions. IL-17 is a cytokine pertaining to a new class of immunological response termed Th17. Th17 response has been characterized by the IL-17 release by CD4+ lymphocytes and has been associated to stabilization and perpetuation of the inflammatory process, as well as to neutrophil recruitment. The present study focused on the investigation of the IL-17 expression in periapical abscess and periapical granuloma, in order to verify if there are differences between the lesions that could be related to level of neutrophil infiltrate. Immunohistochemical tests to IL-17, CD4 and CD8 (to identify different lymphocyte population) and elastase (to detect neutrophils) were performed in the periapical abscess (n=25) and granuloma (n=25) biopsies, selected from the collection of Surgical Pathology Service of the Department of Oral Pathology FOUSP. Percentage of the labeling area showing positive expression was obtained for the all cited markers. Counting of CD4+/IL17+ and CD8+/IL7+ cells detected by immunofluorescence was also performed. Friedman´s and Mann-Whitney non-parametric statistical tests were applied for the labeling area percentages in order to detect the significant differences between abscess and granuloma. Spearman´s correlation test was adopted to verify whether there was a correlation between IL-17 and the other markers. In the periapical abscess biopsies, elastase, IL-17, and CD8 were intensively labeled, with area percentage significantly higher than that observed for CD4 (p<0.0001). By the Spearman correlation test, there was significant positive correlation between IL-17 and CD8 (rs = 0.5944, p=0.0415), but not between IL-17 and elastase, and IL-17 and CD4. In the double staining by immunofluorescence there was significantly more CD4+/IL17+ cells than CD8+/IL17+ cells (p=0.0250). In the periapical granulomas, CD4 labeling area percentage was significantly higher than those for elastase (p=0.0055), CD8 (p=0.0200), and IL-17 (p=0.0210). There was significant positive correlation between IL-17 and elastase (rs = 0.5604, p=0.0463), but not between IL-17 and the other markers. The most frequent double staining cells were CD4+/IL17+ cells in the comparison with CD8+/IL17+ cells (p=0.0114). In conclusion, IL-17 labeling area percentage is higher in the abscess than in the granuloma; in the granulomatous lesions the IL-17 expression is directly proportional to the neutrophil infiltration. These results may indicate that the Th17 response participates to the acute phase of the apical inflammatory process. Although there were significant differences regarding the predominant T lymphocytes types, the co-expression of IL-17 and CD4 in the both inflammatory processes may suggest that this CD4+ lymphocytes are the main responsible for IL-17 release in the analyzed periapical lesions.

Francisella tularensis, l'agent de la tularémie, est une bactérie intracellulaire capable d'infecter un grand nombre de cellules dont les macrophages. Le système immunitaire inné cytosolique est capable de détecter la bactérie à différents stades de son cycle d'infection. Dans un premier temps, le macrophage détecte la bactérie cytosolique et produit de l'interféron de type I. Cet interféron induit l'expression de milliers de gènes. Le macrophage est ensuite capable de détecter l'ADN cytosolique de la bactérie via un récepteur spécifique AIM2. La liaison AIM2-ADN entraine la formation d'un complexe multi-protéique appelé inflammasome et se composant de AIM2-ASC-caspase-1. L'activation de ce complexe conduit à la maturation de la caspase-1. Caspase-1 permet la sécrétion de deux cytokines majeures antimicrobiennes : l'IL-1beta et l'IL-18. De plus, caspase-1 induit une mort programmée des cellules infectées appelée pyroptose. La sécrétion de cytokines et la pyroptose sont deux évènements majeurs pour lutter contre les pathogènes. Ma thèse a consisté à identifier le lien entre l'interféron et l'activation de l inflammasome AIM2 dans des macrophages infectés par la bactérie Francisella. En réalisant un crible a l'aide d'ARNs interférents, j'ai découvert que 2 protéines sont impliquées dans l'activation de cet inflammasome, les guanylate binding proteins 2 et 5 (GBP2 et GBP5). En collaboration avec l'équipe du Dr. Broz en Suisse, nous avons démontré que les GBPs étaient impliquées dans le contrôle de la réplication intracellulaire de Francisella et également dans la lyse de la bactérie permettant le relargage d'ADN et l'activation de l'inflammasome AIM2. Les GBPs sont induites par l'interféron de type I mais très majoritairement par l'interféron de type II (IFN- gamma). Nous avons mis en évidence que le contrôle de la réplication bactérienne est GB dépendant et inflammasome-dépendant en absence d'IFN- gamma mais qu'il devient totalement GB dépendant et inflammasome-indépendant dans des macrophages pré-stimulés avec de l'IFN- gamma. De plus, la mort des macrophages pré-stimulés avec de l'IFN- gamma et infectés par Francisella est également GBP-dépendante et inflammasome-indépendante. En prenant en compte tous ces résultats, nous concluons que les GBPs sont des protéines impliquées dans l'immunité des macrophages infectés par Francisella mais qu'elles ont un double rôle : d'une part celui d'induire l'activation de l'inflammasome (la pyroptose) sous le contrôle de l'interféron de type I et d'autre part, d'induire une mort cellulaire et la lyse des bactéries cytosoliques de manière indépendante de l'inflammasome sous le contrôle d'IFN- gamma. Nos résultats placent donc les GBPs comme les effecteurs majeurs de l'immunité cytosolique antibactérienne suite au traitement par l'IFN-gamma / Francisella tularensis is an intracellular bacterium, and the causative agent of tularemia, capable of infecting a large number of cells including macrophages. The innate cytosolic immune system is capable of detecting the bacterium at different stages of its infection cycle. Macrophages first detect the DNA of the cytosolic bacterium and produce type I interferon. Type I interferon subsequently induces the expression of thousands of genes. The macrophages then detect the cytosolic DNA of the bacterium via a cytosolic DNA sensor called AIM2. The AIM2-DNA binding results in the formation of a multi-protein complex called the AIM2 inflammasome composed of AIM2-ASC-caspase-1. Activation of this complex leads to the maturation of caspase-1. Caspase-1 activation leads to the secretion of two major antimicrobial cytokines, IL-1ß and IL-18. In addition, caspase-1 induces a programmed cell death termed pyroptosis. Cytokine secretion and pyroptosis are two major events in the control of pathogens. My PhD focused in identifying the link between interferon and activation of the AIM2 inflammasome in macrophages infected with the pathogenic bacterium Francisella. I performed a RNA interference screening and identified two proteins involved in the activation of the AIM2 inflammasome: guanylate binding proteins 2 and 5 (GBP2 and GBP5). In collaboration with Dr. Broz’s team in Switzerland, we demonstrated that GBPs are involved in the control of intracellular replication of Francisella and also in the lysis of the bacterium allowing the release of bacterial DNA and the activation of inflammasome AIM2. GBPs are induced by type I interferon but to a much greater extent by type II interferon (IFN-gamma). In the second part of my work, we demonstrate that the control of bacterial replication is GBP-dependent and inflammasome-dependent in the absence of IFN-gamma but that it becomes fully GBP-dependent and inflammasome-independent in macrophages primed with IFN-gamma. Cell-death of macrophages primed with IFN-? and infected with Francisella is also GBP-dependent and inflammasome-independent. Taken together, these results demonstrate that GBPs are innate immunity proteins involved in the death of macrophages and the bacterial growth restriction through two differents pathways : one induces the activation of inflammasome (induction of Pyroptosis) controlled with type I interferon signaling and, another induces cell-death and bacterial killing in an inflammasome-independent manner under the control of IFN-gamma. Our results thus discriminates the antimicrobial action of the inflammasome and of GBPs and position GBPs as the master antibacterial effectors of IFN-gamma, a key cytokine to fight cytosolic bacteria

Le virus de l’hépatite B (HBV) est l’agent étiologique de l’hépatite B. Ce virus est responsable d’hépatite chronique B, de cirrhose et de cancer du foie au niveau mondial. L’absence d’activation de la voie Interféron (IFN) suite à l’infection par HBV est encore mal comprise. Récemment, le senseur cellulaire cytosolic GMP-AMP synthase (cGAS) a été décrit comme un senseur efficace de DNA double brin possédant également une activité antivirale envers des virus à ADN et à ARN. Le but de mes travaux de thèse a été de contribuer à la compréhension des relations existants entre le HBV et cGAS, à des stades précoces et tardifs de l’infection HBV en utilisant des expériences de perte- et gain- de function ainsi que du profilage génomique des génes apparentés à cGAS dans un modéle cellulaire permissif au HBV. Mes travaux ont démontré (1) que cGAS exerce une forte activité antivirale envers le HBV incluant une réduction de la forme nucléaire du génome, le cccDNA; (2) alors que le rcDNA génomique nu est reconnu par la voie cGAS/STING et induit une réponse IFN efficace, la nucléocapside virale protège le DNA génomique viral et l’empêche d’être détecté par la réponse immunitaire innée; et (3) que l’infection par HBV diminue l’expression des acteurs de la voie cGAS-STING et des gènes impliqués dans la réponse immunitaire innée in vitro et in vivo. Ce dernier point met en lumière le rôle de cGAS dans un nouveau mécanisme d’échappement du HBV au système immunitaire inné dans les cellules hépatocytaires et dans ce mécanisme. / Chronic hepatitis B virus (HBV) infection is a major cause of liver disease and cancer worldwide. The mechanisms of viral genome sensing and the evasion of innate immune responses by HBV infection are still poorly understood. Recently, the cyclic GMP-AMP synthase (cGAS) was identified as a DNA sensor. In this PhD work, we aimed to investigate the functional role of cGAS in sensing of HBV infection and elucidate the mechanisms of viral evasion. We performed functional studies including loss- and gain-of-function experiments combined with cGAS effector gene expression profiling in an HBV infection-susceptible cell culture model. Collectively, our data show that (1) the cGAS-STING pathway exhibits robust antiviral activity against HBV infection including reduction of viral cccDNA levels; (2) naked HBV genomic rcDNA is sensed in a cGAS-dependent manner whereas packaging of the viral genome during infection abolishes host cell recognition of viral nucleic acids; (3) HBV infection down-regulates the cGAS/STING pathway actors as well as innate immune effector gene expression in vitro and vivo. Overall, this work led to describing new aspects of the complex interaction between HBV and the DNA sensor cGAS in hepatocytes.

Abscessos e granulomas periapicais são considerados lesões inflamatórias relacionadas a elementos dentários, com origem em infecções do tecido pulpar e periapical. É pouco conhecido o papel da interleucina 17 (IL-17) nessas lesões, uma citocina que participa ativamente de uma classe de resposta imunológica recentemente descrita, denominada Th17. A resposta Th17 tem sido caracterizada pela produção de IL-17 por linfócitos CD4+ e tem sido associada à instalação e perpetuação do processo inflamatório, bem como a intenso recrutamento de neutrófilos. Este estudo tem como foco investigar a expressão dessa citocina em lesões de abscesso e granuloma periapicais, com a intenção de verificar se há diferenças de expressão entre essas duas lesões, já que a presença de infiltrado neutrofílico difere bastante entre elas. Testes imuno-histoquímicos para IL-17, CD4 (para identificação de linfócitos T CD4+), CD8 (para identificação de linfócitos T CD8+) e elastase (para identificação de células inflamatórias polimorfonucleadas) foram realizados em casos de abscesso (n=25) e granuloma (n=25) periapicais, selecionados do acervo do Serviço de Patologia Cirúrgica da Disciplina de Patologia Bucal da FOUSP. Foi obtida a porcentagem da área de células com expressão positiva para os marcadores citados. Também foi realizada a quantificação de células CD4+/IL-17+ e CD8+/IL-17+ detectadas por imunofluorescência nessas mesmas biópsias. Foram realizados testes estatísticos de Friedman e Mann-Whitney, para se verificarem as diferenças entre as porcentagens de marcação imuno-histoquímica obtidas para o abscesso e o granuloma, bem como teste de correlação de Spearman, para se verificar se havia correlação entre a expressão de IL-17 e os demais marcadores. Nos casos de abscesso periapical, houve expressão intensa de elastase, seguida de IL-17 e CD8, cujas respectivas porcentagens de expressão não diferiram estatisticamente entre si, mas foram significativamente maiores do que a da expressão do CD4 (p<0,0001). No teste de correlação de Spearman, houve correlação positiva significante entre IL-17 e CD8 (rs = 0,5944, p=0,0415), mas não entre IL-17 e elastase e IL-17 e CD4. Na quantificação de células duplamente positivas pela técnica da imunofluorescência houve significantemente mais células CD4+/IL-17+ do que CD8+/IL-17+ (p=0,0250). Nos casos de granuloma periapical, observou-se que a porcentagem de área de marcação do CD4 foi significativamente maior em relação a da elastase (p=0,0055), do CD8 (p=0,0200) e da IL-17 (p=0,0210). Houve correlação positiva significativa entre IL-17 e elastase (rs = 0,5604, p=0,0463), mas não entre IL-17 e os demais marcadores. Na quantificação de células duplamente positivas pela técnica da imunofluorescência houve significância maior para células CD4+/IL-17 do que de células CD8+/IL-17+ (p=0,0470). Na comparação da porcentagem de área de marcação entre abscesso e granuloma, a porcentagem de IL-17 foi significativamente maior nos abscessos (p=0,0114). Concluiu-se que há maior expressão da IL-17 em abscessos do que em granulomas e que, nesses últimos, essa citocina é mais expressa quando há maior expressão de células polimorfonucleadas. Isso parece evidenciar a participação da resposta Th17 em fases agudas do processo inflamatório. Apesar de haver diferenças significativas entre as lesões quanto ao predomínio das subpopulações de linfócitos T, em ambas as lesões há maior co-expressão da IL-17 em linfócitos CD4+, indicando que provavelmente essa população linfocitária seja a principal responsável pela secreção dessa citocina nas lesões estudadas. / Periapical abscess and periapical granulomas are considered inflammatory lesions related to dental infections originated from pulpal and periodontal tissues. There is little information about the role of interleukin 17 (IL-17) on these lesions. IL-17 is a cytokine pertaining to a new class of immunological response termed Th17. Th17 response has been characterized by the IL-17 release by CD4+ lymphocytes and has been associated to stabilization and perpetuation of the inflammatory process, as well as to neutrophil recruitment. The present study focused on the investigation of the IL-17 expression in periapical abscess and periapical granuloma, in order to verify if there are differences between the lesions that could be related to level of neutrophil infiltrate. Immunohistochemical tests to IL-17, CD4 and CD8 (to identify different lymphocyte population) and elastase (to detect neutrophils) were performed in the periapical abscess (n=25) and granuloma (n=25) biopsies, selected from the collection of Surgical Pathology Service of the Department of Oral Pathology FOUSP. Percentage of the labeling area showing positive expression was obtained for the all cited markers. Counting of CD4+/IL17+ and CD8+/IL7+ cells detected by immunofluorescence was also performed. Friedman´s and Mann-Whitney non-parametric statistical tests were applied for the labeling area percentages in order to detect the significant differences between abscess and granuloma. Spearman´s correlation test was adopted to verify whether there was a correlation between IL-17 and the other markers. In the periapical abscess biopsies, elastase, IL-17, and CD8 were intensively labeled, with area percentage significantly higher than that observed for CD4 (p<0.0001). By the Spearman correlation test, there was significant positive correlation between IL-17 and CD8 (rs = 0.5944, p=0.0415), but not between IL-17 and elastase, and IL-17 and CD4. In the double staining by immunofluorescence there was significantly more CD4+/IL17+ cells than CD8+/IL17+ cells (p=0.0250). In the periapical granulomas, CD4 labeling area percentage was significantly higher than those for elastase (p=0.0055), CD8 (p=0.0200), and IL-17 (p=0.0210). There was significant positive correlation between IL-17 and elastase (rs = 0.5604, p=0.0463), but not between IL-17 and the other markers. The most frequent double staining cells were CD4+/IL17+ cells in the comparison with CD8+/IL17+ cells (p=0.0114). In conclusion, IL-17 labeling area percentage is higher in the abscess than in the granuloma; in the granulomatous lesions the IL-17 expression is directly proportional to the neutrophil infiltration. These results may indicate that the Th17 response participates to the acute phase of the apical inflammatory process. Although there were significant differences regarding the predominant T lymphocytes types, the co-expression of IL-17 and CD4 in the both inflammatory processes may suggest that this CD4+ lymphocytes are the main responsible for IL-17 release in the analyzed periapical lesions.

Les IgIV, une préparation thérapeutique d'IgG normales, sont utilisées dans le traitement de diverses maladies auto-immunes et inflammatoires. Les mécanismes par lesquels les IgIV exercent une activité anti-inflammatoire ne sont pas complètement compris. Elles interagissent avec de nombreux composants du système immunitaire et modulent leurs fonctions. Des études récentes ont rapporté que l'hème oxygénase-1 (HO-1) joue un rôle important dans la régulation de la réponse inflammatoire dans un certain nombre de pathologies. Plusieurs agents thérapeutiques exercent des effets anti-inflammatoires grâce à l'induction de l'HO-1. Etant donné le rôle commun anti-inflammatoire de l'HO-1 et des IgIV, j'ai étudié l'implication de l'HO-1 dans les mécanismes d'action des IgIV. J'ai montré que les effets des IgIV ne sont pas associés à l'induction de l'HO-1, que ce soit dans des cellules de l'immunité innée comme les monocytes, cellules dendritiques ou macrophages, ou dans les reins et foie de souris avec une encéphalomyélite auto-immune expérimentale traitées par les IgIV. Des données récentes dans des modèles expérimentaux suggèrent que les IgIV induisent la sécrétion d’IL-4 des basophiles en augmentant l’IL-33 des cellules innées SIGN-R1+. J’ai rapporté que les IgIV induisent directement l’activation de basophiles pré-stimulés avec l’IL-3 alors que contrairement au modèle murin, l’IL-33 n’est pas indispensable. L’activation des basophiles par les IgIV est associée à l’expression augmentée de CD69 et la sécrétion d’IL-4, d’IL-6 et d’IL-8. Ces fonctions sont médiées par les fragments F(ab’)2 qui se lient à des IgE membranaires et activent la voie Syk. / Intravenous immunoglobulin (IVIG), a therapeutic normal immunoglobulin G preparation, is used in the therapy of various autoimmune and inflammatory conditions. The mechanisms by which IVIG exerts anti-inflammatory effects are not completely understood. It interacts with numerous components of the immune system including dendritic cells, macrophages, T and B cells and modulates their functions. Recent studies have reported that heme oxygenase-1 (HO-1) pathway plays an important role in the regulation of inflammatory response in several pathologies. Several therapeutic agents exert anti-inflammatory effects via induction of HO-1. Therefore, in view of common anti-inflammatory role exerted by both HO-1 and IVIG, I investigated if mechanisms of IVIG implicate HO-1. I show that anti-inflammatory effects of IVIG were not associated with an induction of HO-1 either in innate cells such as monocytes, dendritic cells and macrophages or in the kidneys or liver of experimental autoimmune encephalomyelitis. Recent data in experimental models suggest that IVIG induces IL-4 in basophils by enhancing IL-33 in SIGN-R1+ innate cells. I reported that IVIG directly induces activation of IL-3-primed basophils while unlike mice IL-33 was dispensable. The activation of basophils by IVIG was associated with enhanced expression of CD69 and secretion of IL-4, IL-6 and IL-8. These functions of IVIG are mediated via F(ab’)2 fragments that bind to basophil surface IgE and activate Syk pathway.

The innate immune protein surfactant protein (SP-) D is a carbohydrate binding protein that was originally isolated from mucosal lung tissues. Recently, studies show that SP-D binds to antibodies, including immunoglobulin M (IgM), which interacts with late apoptotic cells. Here we focus on the interaction between SP-D and IgM as they pertain to late apoptotic cell clearance. We hypothesized that the three-way interaction between IgM, SP-D and late apoptotic cells is functionally applicable to clearing late apoptotic cells from the lungs, thereby reducing lung inflammation. We show that SP-D binds to IgM and that IgM binds to the late apoptotic subclass of dying cells. We demonstrate that IgM and SP-D can both bind to late apoptotic cells in mutually distinct regions while also displaying some regional overlap. We show evidence that during LPS-induced lung inflammation both IgM and SP-D levels are elevated and this corresponds to an augmentation of apoptotic cell clearance. We illustrate that the protein interaction of IgM and SP-D is functionally relevant to apoptotic cell clearance in the lungs by showing that late apoptotic cells coated in IgM and/or SP-D are cleared more efficiently than control cells, by alveolar macrophages in vivo. Our ex vivo studies further show that these cells internalize apoptotic cells by engulfing very small particles released from the dying cells. We then showed that IgM preferentially directs the engulfment of small particles (~1 μm) by macrophages, in an apparent size-specific antibody-dependent particle clearance function. Our data reveals a novel relationship amongst IgM, SP-D, apoptotic cells, and alveolar macrophages that contributes to our understanding of apoptotic cell clearance, which may be used in the future to generate strategies addressing apoptotic cell accumulation or clearance deficiency in disease.

The innate immune protein surfactant protein (SP-) D is a carbohydrate binding protein that was originally isolated from mucosal lung tissues. Recently, studies show that SP-D binds to antibodies, including immunoglobulin M (IgM), which interacts with late apoptotic cells. Here we focus on the interaction between SP-D and IgM as they pertain to late apoptotic cell clearance. We hypothesized that the three-way interaction between IgM, SP-D and late apoptotic cells is functionally applicable to clearing late apoptotic cells from the lungs, thereby reducing lung inflammation. We show that SP-D binds to IgM and that IgM binds to the late apoptotic subclass of dying cells. We demonstrate that IgM and SP-D can both bind to late apoptotic cells in mutually distinct regions while also displaying some regional overlap. We show evidence that during LPS-induced lung inflammation both IgM and SP-D levels are elevated and this corresponds to an augmentation of apoptotic cell clearance. We illustrate that the protein interaction of IgM and SP-D is functionally relevant to apoptotic cell clearance in the lungs by showing that late apoptotic cells coated in IgM and/or SP-D are cleared more efficiently than control cells, by alveolar macrophages in vivo. Our ex vivo studies further show that these cells internalize apoptotic cells by engulfing very small particles released from the dying cells. We then showed that IgM preferentially directs the engulfment of small particles (~1 μm) by macrophages, in an apparent size-specific antibody-dependent particle clearance function. Our data reveals a novel relationship amongst IgM, SP-D, apoptotic cells, and alveolar macrophages that contributes to our understanding of apoptotic cell clearance, which may be used in the future to generate strategies addressing apoptotic cell accumulation or clearance deficiency in disease.

Alzheimer’s Disease (AD) is a chronic progressive neurological condition, clinically characterized by memory deficits, cognitive and physical impairment, and personality changes. Traditionally, AD was considered a type of protein folding disorder. Here, the concept of AD as an autoimmune disease of the innate immune system was developed. After exploring evolutionary connections between the AD peptide β-amyloid (Aβ) and known antimicrobial peptides (AMPs), and elucidating the structural similarities between Aβ and AMPs, a mechanism of action for Aβ’s antimicrobial activity is proposed that is based on the compromise of bacterial membranes. Following these theoretical considerations, experimental evidence is presented for the production of Aβ by cells in response to infection, and for Aβ’s antibacterial and antiviral activity. Rooted in similarities of the cell membranes of neuronal and bacterial cells in terms of lipid composition and transmembrane potential, it is hypothesised that Aβ’s neurotoxicity is caused by its misguided attack on neurons as an AMP. In reversing the concept of Aβ as an AMP, the similarity of AMPs to Aβ is demonstrated in experiments revealing the neurotoxicity of two AMPs, LL 37, and cecropin A. To determine a mechanism for the progressive nature of AD, it was shown that, although apoptosis may be involved in AD, it is actually necrosis that is responsible for the propagation of neuronal cell death so characteristic of AD. With the Vicious Cycle of AD, a scheme was devised, integrating the results obtained here with data and research from other groups, which explains the chronic and progressive nature of AD as a result of Aβ’s physiological role as an AMP and innate immune system effector. Borne from Aβ’s activity as an AMP and its central role in the Vicious Cycle of AD, a question was investigated: do antibiotics, such as penicillin, that cause release of bacterial endotoxins due to their mechanism of action, trigger the Vicious Cycle of AD and thus lead to the development of AD? Preliminary evidence supporting this notion was presented.

Reverse genetics systems that are based on either viral transcripts or cDNA genome segments cloned in plasmids have recently been reported for some of the dsRNA viruses of the Reoviridae family, namely African horsesickness virus, bluetongue virus and orthoreovirus. For rotaviruses, three reverse genetics systems which only allow the manipulation of a single genome segment have been described. These rotavirus single genome segment reverse genetics systems are not true stand-alone systems because they require a helper virus and a recombinant virus selection step. A true selection-free, plasmid- only or transcript-based reverse genetics system for rotaviruses is lacking. This study sought to identify and characterise the factors that need to be understood and overcome for the development of a rotavirus reverse genetics system using mRNA derived from the in vitro transcription of a consensus nucleotide sequence as well as from double-layered particles. The consensus whole genome sequence of the prototype rotavirus DS-1 and SA11 strains was determined using sequenceindependent whole genome amplification and 454® pyrosequencing. For the rotavirus DS-1 strain, a novel isoleucine in a minor population variant was found at position 397 in a hydrophobic region of VP4. NSP1 contained seven additional amino acids MKSLVEA at the N-terminal end due to an insertion in the consensus nucleotide sequence of genome segment 5. The first 34 nucleotides at the 5'- terminus and last 30 nucleotides at the 3'-terminal end of genome segment 10 (NSP4) of the DS-1 strain were determined in this study. The consensus genome segment 11 (NSP5/6) sequence was 821 bp in length, 148 bp longer than previously reported. The 454® pyrosequence data for a rotavirus SA11 sample with no known passage history revealed a mixed infection with two SA11 strains. One of the strains was a reassortant which contained genome segment 8 (NSP2) from the bovine rotavirus O agent. The other ten consensus genome segments of the two strains could not be differentiated. Novel minor population variants of genome segments 4 (VP4), 9 (VP7) and 10 (NSP4) were identified. Molecular clock phylogenetic analyses of the rotavirus SA11 genomes showed that the two SA11 strains were closely related to the original SA11-H96 strain isolated in 1958. Plasmids containing inserts of the consensus cDNA of the rotavirus DS-1 strain were purchased and used to generate exact capped transcripts by in vitro transcription with a T7 polymerase. Wild-type transcripts of rotavirus SA11 were obtained from in vitro transcription using purified rotavirus SA11 double-layered particles. The purified rotavirus DS-1 and SA11 transcripts were transfected into BSR, COS-7 and MA104 cells. Work on MA104 cells was discontinued due their very low transfection efficacy. In BSR and COS-7 cells, rotavirus DS-1 and SA11 transcripts induced cell death. However, no viable rotavirus was recovered following attempts to infect MA104 cells with the BSR and COS-7 transfected cell lysates. The cell death was determined to be due to apoptotic cell death mechanisms. Immunostaining showed that the DS-1 genome segment 6 (VP6) and SA11 transcripts were translated in transfected BSR and COS-7 cells. Based on visual inspection, the translation seemed to be higher in the retinoic acid-inducible gene-I (RIG-I) deficient BSR cells than in COS-7 cells. This suggested that the transfection of rotavirus transcripts induced an innate immune response which could lead to the development of an antiviral state. Therefore, the innate immune response to rotavirus transcripts was investigated in HEK 293H cells using qRT-PCR and western blot analyses. Results of this investigation showed that RIG-I, but not MDA5 sensed rotavirus transcripts in transfected HEK 293H cells. Furthermore, rotavirus transcripts induced high levels of cellular mRNA encoding the cytokines IFN-1β, IFN-λ1, CXCL10 and TNF-α. Other cytokines namely, IFN-α, IL-10, IL-12 p40 and the kinase RIP1 were not significantly induced. Inhibiting the RNA-dependent protein kinase R (PKR) reduced the induction of cytokines IFN-1β, IFN-λ1, CXCL10 and TNF-α, but the expression levels were not abrogated. The importance of a consensus sequence and the insights gained in the current study regarding the role of the innate immune response after transfection of rotavirus transcripts into cells in culture, should aid the development of a true rotavirus reverse genetics system. / Thesis (PhD (Biochemistry))--North-West University, Potchefstroom Campus, 2013