Thesis (Ph. D.)--West Virginia University, 2005 / Title from document title page. Document formatted into pages; contains ix, 210 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

Leptospirose é uma zoonose causada pela espiroqueta pertencente ao gênero Leptospira. LipL32 é um antígeno de superfície altamente conservado somente entre as espécies de leptospiras patogênicas e é expresso em altos níveis tanto in vitro com in vivo. HlyX é relatada como sendo uma proteína que possui um provável peptídeo sinal e cinco tetratricopeptídeos repetidos (TPR) em sua sequência de aminoácidos. Neste trabalho, mostrou-se que HlyX é expressa somente em cepas patogênicas, não sendo detectada a sua expressão na cepa saprofítica. HlyX foi reconhecida somente por soros de pacientes da fase convalescente da doença. Em constraste, LipL32 foi reconhecida por soros de pacientes colhidos tanto na fase aguda quanto na fase convalescente da infecção. Nossos resultados de immunoblot indicam que os domínios imunodominantes da proteína são os fragmentos C-terminal e intermediário. Uma resposta IgM foi detectada exclusivamente contra o fragmento C-terminal de LipL32 em ambas as fases da infecção. Com relação à capacidade de LipL32 e HlyX de interagir com componentes de matriz extracelular (CME), foi observada uma interação específica e dose-dependente de LipL32 e HlyX com colágeno tipo IV e fibronectina plasmática. O fragmento C-terminal de LipL32 é responsável por esta interação. Tanto a heparina quanto a gelatina foram capazes de inibir a ligação de LipL32 à fibronectina plasmática de forma dose-dependente, indicando que os domínios de ligação à heparina (30 kDa) e gelatina (45 kDa) da fibronectina estão envolvidos nesta interação. Por outro lado, apenas o domínio de ligação à heparina participa da interação da fibronectina com a proteína HlyX. A capacidade protetora das duas proteínas estudadas foi avaliada através de ensaios de imunização e desafio realizados em modelo animal (hamsters). A proteína HlyX induziu altos títulos de anticorpos IgG (1:128.000), mas somente a co-administração HlyX e LipL32 e a proteína LipL32 pura conferiram proteção, 100% e 80% respectivamente. HlyX não foi capaz de conferir proteção quando administrada apenas com o adjuvante Al(OH)3. Em conclusão, os resultados indicam que o domínio C-terminal de LipL32 é reconhecido desde o início da infecção e este domínio é responsável por mediar a interação de LipL32 com CME. Os dados obtidos com HlyX demonstram um possível papel desta proteína na patogênese, pelo fato de ser expressa e conservada em cepas patogênicas, e também por interagir com CME. Porém, apesar de HlyX apresentar altos títulos de anticorpos IgG, não conferiu atividade protetora quando administrada individualmente. / Leptospirosis, a spirochaetal zoonotic disease caused by Leptospira, has been recognized as na important emerging infectious disease. LipL32 is a surface lipoprotein which is highly conserved among pathogenic Leptospira species and is also expressed at high levels either during cultivation and natural infection. Regarding HlyX, it has been annotated as a protein containing a signal peptide and five tetratricopeptide repeats (TPR). Immunoblot analyses concerning HlyX distribution on Leptospira spp. indicate that this protein is expressed exclusively by pathogenic species. Moreover, HlyX was only recognized by sera of patients in the second week of leptospirosis infection. In contrast, LipL32 was recognized by acute and convalescent sera from leptospirosis patients. Our immunoblot results indicate that both the C-terminal and the intermediate domains of LipL32 are recognized by sera of patients. An IgM response was detected exclusively against the LipL32 C-terminus in both the acute and convalescent phases of illness. Concerning the capacity of LipL32 and HlyX to interact with extracellular matrix (ECM) components, a dose-dependent specific binding of LipL32 and HlyX to collagen IV and plasma fibronectin was observed. The LipL32 binding capacity could be attributed to the C-terminal portion of this molecule. Both heparin and gelatin could inhibit LipL32 binding to fibronectin in a concentration-dependent manner, indicating that the 30-kDa heparin- and the 45-kDa gelatin-binding domains of fibronectin are involved in this interaction. However, HlyX binding to fibronectin could only be inhibited by heparin in a concentration-dependent manner. We also evaluated whether HlyX and LipL32 could induce protective immunity against the challenge with a homologous serovar in hamsters. Although high anti-HlyX (IgG) titers (1:128,000) have been achieved upon immunization, no protection was observed. However, a combined HlyX and LipL32 immunization could induce a protective response (100%). The protection observed for LipL32 immunization was 80%. Altogether, the results provide evidence that the LipL32 C-terminus is recognized early in the course of infection and is the domain responsible for mediating interaction with ECM proteins. HlyX protein may contribute to the pathogenesis of the disease by interacting with host proteins. However, HlyX is not a protective antigen when administered alone.

Leptospirose é uma zoonose causada pela espiroqueta pertencente ao gênero Leptospira. LipL32 é um antígeno de superfície altamente conservado somente entre as espécies de leptospiras patogênicas e é expresso em altos níveis tanto in vitro com in vivo. HlyX é relatada como sendo uma proteína que possui um provável peptídeo sinal e cinco tetratricopeptídeos repetidos (TPR) em sua sequência de aminoácidos. Neste trabalho, mostrou-se que HlyX é expressa somente em cepas patogênicas, não sendo detectada a sua expressão na cepa saprofítica. HlyX foi reconhecida somente por soros de pacientes da fase convalescente da doença. Em constraste, LipL32 foi reconhecida por soros de pacientes colhidos tanto na fase aguda quanto na fase convalescente da infecção. Nossos resultados de immunoblot indicam que os domínios imunodominantes da proteína são os fragmentos C-terminal e intermediário. Uma resposta IgM foi detectada exclusivamente contra o fragmento C-terminal de LipL32 em ambas as fases da infecção. Com relação à capacidade de LipL32 e HlyX de interagir com componentes de matriz extracelular (CME), foi observada uma interação específica e dose-dependente de LipL32 e HlyX com colágeno tipo IV e fibronectina plasmática. O fragmento C-terminal de LipL32 é responsável por esta interação. Tanto a heparina quanto a gelatina foram capazes de inibir a ligação de LipL32 à fibronectina plasmática de forma dose-dependente, indicando que os domínios de ligação à heparina (30 kDa) e gelatina (45 kDa) da fibronectina estão envolvidos nesta interação. Por outro lado, apenas o domínio de ligação à heparina participa da interação da fibronectina com a proteína HlyX. A capacidade protetora das duas proteínas estudadas foi avaliada através de ensaios de imunização e desafio realizados em modelo animal (hamsters). A proteína HlyX induziu altos títulos de anticorpos IgG (1:128.000), mas somente a co-administração HlyX e LipL32 e a proteína LipL32 pura conferiram proteção, 100% e 80% respectivamente. HlyX não foi capaz de conferir proteção quando administrada apenas com o adjuvante Al(OH)3. Em conclusão, os resultados indicam que o domínio C-terminal de LipL32 é reconhecido desde o início da infecção e este domínio é responsável por mediar a interação de LipL32 com CME. Os dados obtidos com HlyX demonstram um possível papel desta proteína na patogênese, pelo fato de ser expressa e conservada em cepas patogênicas, e também por interagir com CME. Porém, apesar de HlyX apresentar altos títulos de anticorpos IgG, não conferiu atividade protetora quando administrada individualmente. / Leptospirosis, a spirochaetal zoonotic disease caused by Leptospira, has been recognized as na important emerging infectious disease. LipL32 is a surface lipoprotein which is highly conserved among pathogenic Leptospira species and is also expressed at high levels either during cultivation and natural infection. Regarding HlyX, it has been annotated as a protein containing a signal peptide and five tetratricopeptide repeats (TPR). Immunoblot analyses concerning HlyX distribution on Leptospira spp. indicate that this protein is expressed exclusively by pathogenic species. Moreover, HlyX was only recognized by sera of patients in the second week of leptospirosis infection. In contrast, LipL32 was recognized by acute and convalescent sera from leptospirosis patients. Our immunoblot results indicate that both the C-terminal and the intermediate domains of LipL32 are recognized by sera of patients. An IgM response was detected exclusively against the LipL32 C-terminus in both the acute and convalescent phases of illness. Concerning the capacity of LipL32 and HlyX to interact with extracellular matrix (ECM) components, a dose-dependent specific binding of LipL32 and HlyX to collagen IV and plasma fibronectin was observed. The LipL32 binding capacity could be attributed to the C-terminal portion of this molecule. Both heparin and gelatin could inhibit LipL32 binding to fibronectin in a concentration-dependent manner, indicating that the 30-kDa heparin- and the 45-kDa gelatin-binding domains of fibronectin are involved in this interaction. However, HlyX binding to fibronectin could only be inhibited by heparin in a concentration-dependent manner. We also evaluated whether HlyX and LipL32 could induce protective immunity against the challenge with a homologous serovar in hamsters. Although high anti-HlyX (IgG) titers (1:128,000) have been achieved upon immunization, no protection was observed. However, a combined HlyX and LipL32 immunization could induce a protective response (100%). The protection observed for LipL32 immunization was 80%. Altogether, the results provide evidence that the LipL32 C-terminus is recognized early in the course of infection and is the domain responsible for mediating interaction with ECM proteins. HlyX protein may contribute to the pathogenesis of the disease by interacting with host proteins. However, HlyX is not a protective antigen when administered alone.

Indiana University-Purdue University Indianapolis (IUPUI) / Lyme disease, the most prevalent vector-borne illness in the United States, is a multisystem inflammatory disorder caused by infection with the spirochete Borrelia burgdorferi (Bb). This spirochete is maintained in nature through an enzootic cycle involving ticks and small mammals. The Bb genome encodes a large number of surface lipoproteins, many of which are expressed during mammalian infection. One of these lipoproteins is the major outer surface protein C (OspC) whose production is induced during transmission as spirochetes transition from ticks to mammals. OspC is required for Bb to establish infection in mice and has been proposed to facilitate evasion of innate immunity. However, the exact biological function of OspC remains elusive. Our studies show the ospC-deficient spirochete could not establish infection in NOD-scid IL2rγnull mice that lack B cells, T cells, NK cells, and lytic complement, whereas the wild-type spirochete was fully infectious in these mice. The ospC mutant also could not establish infection in SCID and C3H mice that were transiently neutropenic during the first 48 h post-challenge. However, depletion of F4/80+ phagocytes at the skin-site of inoculation in SCID mice allowed the ospC mutant to establish infection in vivo. In phagocyte-depleted SCID mice, the ospC mutant was capable to colonize the joints and triggered neutrophilia during dissemination in a similar pattern as wild-type bacteria. We then constructed GFP-expressing Bb strains to evaluate the interaction of the ospC mutant with phagocytes. Using flow cytometry and fluorometric assay for phagocytosis, we found that phagocytosis of GFP-expressing ospC mutant spirochetes by murine peritoneal macrophages and human THP-1 cells was significantly higher than parental wild-type Bb strains, suggesting that OspC has an anti-phagocytic property. This enhancement in phagocytosis was not mediated by MARCO and CD36 scavenger receptors and was not associated with changes in mRNA levels of TNFα, IL-1β, and IL-10. Phagocytosis assays with HL60 neutrophil-like cells showed that uptake of Bb strains was independent to OspC. Together, our findings reveal that F4/80+ phagocytes are important for clearance of the ospC mutant, and suggest that OspC promotes spirochetes' evasion of macrophages in the skin of mice during early Lyme borreliosis.

Indiana University-Purdue University Indianapolis (IUPUI) / Borrelia burgdorferi, a bacterium which causes Lyme disease, is maintained in nature through a cycle involving two distinct hosts: a tick vector and a mammalian host. To adapt to these two diverse environments, B. burgdorferi undergoes dramatic alterations in its surface lipoprotein. Two essential lipoproteins, outer surface protein A (OspA) and outer surface protein C (OspC), are reciprocally regulated throughout the B. burgdorferi lifecycle. Very little is known about the regulation of OspA. These studies elucidate the regulatory mechanisms controlling the expression of OspA. Various truncations of the ospA promoter were created and then studied in our novel in vitro model of ospA repression or grown within the host-adapted model. A T-Rich region of the ospA promoter was determined to be a cis-element essential for both the full expression and full repression of ospA.