16 resultados para Pneumonia
Filtro por publicador
- ABACUS. Repositorio de Producción Científica - Universidad Europea (1)
- Aberdeen University (3)
- AMS Tesi di Dottorato - Alm@DL - Università di Bologna (4)
- Archivo Digital para la Docencia y la Investigación - Repositorio Institucional de la Universidad del País Vasco (5)
- Aston University Research Archive (5)
- B-Digital - Universidade Fernando Pessoa - Portugal (2)
- Biblioteca de Teses e Dissertações da USP (1)
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- Bioline International (8)
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- Brock University, Canada (2)
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- Dalarna University College Electronic Archive (3)
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- DI-fusion - The institutional repository of Université Libre de Bruxelles (5)
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- Duke University (4)
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- Indian Institute of Science - Bangalore - Índia (5)
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- Instituto Gulbenkian de Ciência (2)
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- QUB Research Portal - Research Directory and Institutional Repository for Queen's University Belfast (64)
- Queensland University of Technology - ePrints Archive (41)
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- Repositório Científico do Instituto Politécnico de Lisboa - Portugal (1)
- Repositorio de la Universidad de Cuenca (1)
- Repositório do Centro Hospitalar de Lisboa Central, EPE - Centro Hospitalar de Lisboa Central, EPE, Portugal (2)
- Repositório Institucional da Universidade de Aveiro - Portugal (1)
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- Repositório Institucional UNESP - Universidade Estadual Paulista "Julio de Mesquita Filho" (128)
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- SAPIENTIA - Universidade do Algarve - Portugal (3)
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- Universidad del Rosario, Colombia (24)
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- Universidade Federal do Pará (8)
- Universidade Federal do Rio Grande do Norte (UFRN) (10)
- Universita di Parma (1)
- Université de Lausanne, Switzerland (14)
- Université de Montréal, Canada (15)
- Université Laval Mémoires et thèses électroniques (1)
- University of Canberra Research Repository - Australia (1)
- University of Connecticut - USA (2)
- University of Michigan (12)
- University of Queensland eSpace - Australia (42)
- University of Washington (1)
Resumo:
Group B streptococci (GBS) are the most common cause of neonatal sepsis, pneumonia, and meningitis. The alpha C protein is a surface-associated antigen; the gene (bca) for this protein contains a series of tandem repeats (each encoding 82 aa) that are identical at the nucleotide level and express a protective epitope. We previously reported that GBS isolates from two of 14 human maternal and neonatal pairs differed in the number of repeats contained in their alpha C protein; in both pairs, the alpha C protein of the neonatal isolate was smaller in molecular size. We now demonstrate by PCR that the neonatal isolates contain fewer tandem repeats. Maternal isolates were susceptible to opsonophagocytic killing in the presence of alpha C protein-specific antiserum, whereas the discrepant neonatal isolates proliferated. An animal model was developed to further study this phenomenon. Adult mice passively immunized with antiserum to the alpha C protein were challenged with an alpha C protein-expressing strain of GBS. Splenic isolates of GBS from these mice showed a high frequency of mutation in bca--most commonly a decrease in repeat number. Isolates from non-immune mice were not altered. Spontaneous deletions in the repeat region were observed at a much lower frequency (6 x 10(-4)); thus, deletions in that region are selected for under specific antibody pressure and appear to lower the organism's susceptibility to killing by antibody specific to the alpha C protein. This mechanism of antigenic variation may provide a means whereby GBS evade host immunity.