Suchergebnisse

Enterotoxigenic Escherichia coli (ETEC) causes significant diarrheal illness in infants in the developing world and travelers to endemic countries including military personnel. Infection of the host involves bacterial colonization of the small intestinal epithelium and toxin secretion leading to watery diarrhea. CFA/I is the most common colonizing factor antigens expressed on the surface of ETEC isolates. The CFA/I adhesin, CfaE, appears to be required for ETEC binding to human intestinal cells for colonization. Human antibodies against the binding domain of CfaE have potential to block colonization of ETEC and serve as a potent immunoprophylactic therapeutic for ETEC-related diarrhea. In the current study, we generated a panel of fully human monoclonal antibodies (HuMabs) against the adhesin domain of CfaE using mice transgenic for human immunoglobulin genes and identified lead antibodies utilizing a series of in vitro assays. Mice were immunized with the N-terminal binding domain of CfaE fused to maltose binding protein. Over thirty unique IgG1 HuMabs were identified with binding activity to recombinant CfaE. These antibodies were tested for inhibition of hemagglutination of type A human erythrocytes by ETEC. Two lead HuMabs, 837-6 and 840-53, inhibited hemagglutination at low concentrations (< 1 nM). Both antibodies also blocked the binding of ETEC with intestinal epithelial cells. Biacore analysis revealed an affinity of less than 2 nM with distinct epitopes of CfaE. Our analysis suggests that CfaE specific HuMabs 837-6 and 840-53, as the first isolated fully human monoclonal antibodies against CfaE adhesion domain, could potentially be used in combination with heat labile toxin neutralizing antibodies to prevent traveler's diarrhea.

Background. Enterotoxigenic Escherichia coli (ETEC) cause diarrheal illness in infants in the developing world and travelers to endemic countries including military personnel. ETEC infection of the host involves colonization of the small intestinal epithelium and toxin secretion leading to watery diarrhea. There is currently no vaccine licensed to prevent ETEC. CFA/I is one of the most common colonization factor antigens (CFAs). The CFA/I adhesin subunit, CfaE, is required for ETEC adhesion to host intestinal cells. Human antibodies against CfaE have potential to block colonization of ETEC and serve as an immunoprophylactic against ETEC-related diarrhea. Methods. Mice transgenic for human immunoglobulin genes were immunized with CfaE to generate a panel of human monoclonal IgG1 antibodies (HuMAbs). The most potent IgG1 identified in the in vitro functional assays were selected and isotype switched to secretory IgA (sIgA) and tested in animal colonization assays via oral administration. Results. Over 300 unique anti-CfaE IgG1 HuMabs were identified. The lead IgG1 anti-CfaE HuMAbs completely inhibited hemagglutination and blocked adhesion of ETEC to Caco-2 cells. Epitope mapping studies revealed that HuMAbs recognized epitopes in the N-terminal domain of CfaE near the putative receptor binding site. Oral administration of anti-CfaE antibodies in either IgG or secretory IgA isotypes inhibited intestinal colonization in mice challenged with ETEC. A two to four log decrease of colony forming units was observed as compared to irrelevant isotype controls. Conclusions. We identified fully human monoclonal antibodies against CfaE adhesion domain that can be potentially employed as an immunoprophylaxis to prevent ETEC-related diarrhea.

Although BRCA1 function is essential for maintaining genomic integrity in all cell types, it is unclear why increased risk of cancer in individuals harbouring deleterious mutations in BRCA1 is restricted to only a select few tissues. Here we show that human mammary epithelial cells (HMECs) from BRCA1-mutation carriers (BRCA1(mut/+)) exhibit increased genomic instability and rapid telomere erosion in the absence of tumour-suppressor loss. Furthermore, we uncover a novel form of haploinsufficiency-induced senescence (HIS) specific to epithelial cells, which is triggered by pRb pathway activation rather than p53 induction. HIS and telomere erosion in HMECs correlate with misregulation of SIRT1 leading to increased levels of acetylated pRb as well as acetylated H4K16 both globally and at telomeric regions. These results identify a novel form of cellular senescence and provide a potential molecular basis for the rapid cell- and tissue- specific predisposition of breast cancer development associated with BRCA1 haploinsufficiency. ; This work was supported by grants from the Raymond and Beverly Sackler Foundation (M.S.), the Breast Cancer Research Foundation (B.K. and C.K.), the Silvian Foundation (C.K. and A.S.) and the NIH/NCI CA125554 (C.K.), CA092644 (C.K.). Research in the Blasco laboratory was funded by ERC Project Project TEL STEM CELL, FP7 Projects MARK-AGE and EuroBATS, Spanish Ministry of Economy and Competitiveness Projects SAF2008-05384 and CSD2007-00017, Regional of Government of Madrid Project S2010/BMD-2303, AXA Research Fund, Fundacion Botin (Spain) and Fundacion Lilly (Spain). We thank members of the Kuperwasser laboratory for valuable discussions as well as Benjamin Dake, Sarah Phillips and Agueda Tejera for their help with experiments. ; Sí