Our laboratory recently reported that synthetic Abeta peptide has in vitro antimicrobial activity against at least six human pathogens. More recently we presented data suggesting Abeta binding and antimicrobial activity against pathogenic forms of Candida albicans is increased 2-3 orders of magnitude by oligomerization. In this study we present data on the in vivo efficacy of soluble oligomeric Abeta as a protective antimicrobial peptide (AMP). Experiments used cultured transfected cell monolayers and transgenic (Tg) Caenorhabditis elegans as host models and the intracellular bacterial pathogen Salmonella typhimurium as the infecting agent. Data is consistent with a in vivo role for Abeta as an AMP.
METHODS;
Abeta-mediated protection was first tested in a cultured cell monolayer model. Monolayers of naive or transfected cells expressing the 42 residue Abeta isoform (Abeta42) were prepared and infected with S. typhimurium bacteria labeled with red fluorescent protein (Salmonella-RFP) using the gentamycin infection assay protocol. Experiments next characterized resistance to Salmonella-RFP infection in a C. Elegans model. Infection of CL2122 control worms expressing green fluorescent protein (GFP) alone was compared to GMC101 Tg animals co-expressing GFP and Abeta42. Infection in both models was monitored using confocal microscopy, and viability, behavioral and biochemical assays. Experiments included immunochemical and chromatographic characterization of the oligomerization state of Abeta in host models.
RESULTS;
For cultured cells Abeta42 expression was associated with a 1-2 order of magnitude reduction in Salmonella invasion. In addition, survival of transfection Abeta expressing cells was significantly extended compared to naive cells. In the C. elegans infection model the spread of Salmonella-RFP was significantly inhibited in Abeta42 expressing tissues while overall bacterial load was significantly lower for GMC101 Tg worms compared to the CL2122 control strain. Biochemical data was consistent with an Abeta oligomer mediated antimicrobial mechanism.
CONCLUSION; Data is consistent with our previous findings of a potent in vitro antimicrobial activity for Abeta. The new finding confirm that expression of Abeta is also protective against invasive bacterial pathogens in vivo in cultured cells and C. elegans host models. Our data is further evidence that Abeta is an AMP and normally functions as part of the brains innate immune system.
METHODS;
Abeta-mediated protection was first tested in a cultured cell monolayer model. Monolayers of naive or transfected cells expressing the 42 residue Abeta isoform (Abeta42) were prepared and infected with S. typhimurium bacteria labeled with red fluorescent protein (Salmonella-RFP) using the gentamycin infection assay protocol. Experiments next characterized resistance to Salmonella-RFP infection in a C. Elegans model. Infection of CL2122 control worms expressing green fluorescent protein (GFP) alone was compared to GMC101 Tg animals co-expressing GFP and Abeta42. Infection in both models was monitored using confocal microscopy, and viability, behavioral and biochemical assays. Experiments included immunochemical and chromatographic characterization of the oligomerization state of Abeta in host models.
RESULTS;
For cultured cells Abeta42 expression was associated with a 1-2 order of magnitude reduction in Salmonella invasion. In addition, survival of transfection Abeta expressing cells was significantly extended compared to naive cells. In the C. elegans infection model the spread of Salmonella-RFP was significantly inhibited in Abeta42 expressing tissues while overall bacterial load was significantly lower for GMC101 Tg worms compared to the CL2122 control strain. Biochemical data was consistent with an Abeta oligomer mediated antimicrobial mechanism.
CONCLUSION; Data is consistent with our previous findings of a potent in vitro antimicrobial activity for Abeta. The new finding confirm that expression of Abeta is also protective against invasive bacterial pathogens in vivo in cultured cells and C. elegans host models. Our data is further evidence that Abeta is an AMP and normally functions as part of the brains innate immune system.
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