Type 1 fimbriae are adhesion organelles expressed by many Gram-negative bacteria. They facilitate adherence to mucosal surfaces and inflammatory cells in vitro, but their contribution to virulence has not been defined. This study presents evidence that type 1 fimbriae increase the virulence ofEscherichia coli for the urinary tract by promoting bacterial persistence and enhancing the inflammatory response to infection. In a clinical study, we observed that disease severity was greater in children infected with E. coli O1:Kl:H7 isolates expressing type 1 fimbriae than in those infected with type 1 negative isolates of the same serotype. The E. coli O1:Kl:H7 isolates had the same electrophoretic type, were hemolysin-negative, expressed P fimbriae, and carried thefim DNA sequences. When tested in a mouse urinary tract infection model, the type 1-positive E. coli O1:Kl:H7 isolates survived in higher numbers, and induced a greater neutrophil influx into the urine, than O1:Kl:H7 type 1-negative isolates.To confirm a role of type 1 fimbriae, a flmH null mutant (CN1016) was constructed from an O1:Kl:H7 type 1-positive parent. E. coli CN1016 had reduced survival and inflammatogenicity in the mouse urinary tract infection model. E. coli CN1016 reconstituted with type 1 fimbriae (E. coli CN1018) had restored virulence similar to that of the wild-type parent strain. These results show that type 1 fimbriae in the genetic background of a uropathogenic strain contribute to the pathogenesis of E. coli in the urinary tract.

Pathogenic microbes have evolved sophisticated molecular strategies to subvert host defenses. Here we show that virulent bacteria interfere directly with Toll-like receptor (TLR) function by secreting inhibitory homologs of the Toll/interleukin-1 receptor (TIR) domain. Genes encoding TIR domain containing-proteins (Tcps) were identified in Escherichia coli CFT073 (TcpC) and Brucella melitensis (TcpB). We found that TcpC is common in the most virulent uropathogenic E. coli strains and promotes bacterial survival and kidney pathology in vivo. In silico analysis predicted significant tertiary structure homology to the TIR domain of human TLR1, and we show that the Tcps impede TLR signaling through the myeloid differentiation factor 88 (MyD88) adaptor protein, owing to direct binding of Tcps to MyD88. Tcps represent a new class of virulence factors that act by inhibiting TLR- and MyD88-specific signaling, thus suppressing innate immunity and increasing virulence.

In this study ␣-lactalbumin was converted from the regular, native state to a folding variant with altered biological function. The folding variant was shown to induce apoptosis in tumor cells and immature cells, but healthy cells were resistant to this effect. Conversion to HAMLET (human ␣-lactalbumin made lethal to tumor cells) required partial unfolding of the protein and a specific fatty acid, C18:1, as a necessary cofactor. Conversion was achieved with ␣-lactalbumin derived from human milk whey and with recombinant protein expressed in Escherichia coli. We thus have identified the folding change and the fatty acid as two key elements that define HAMLET, the apoptosis-inducing functional state of ␣-lactalbumin. Although the environment in the mammary gland favors the native conformation of ␣-lactalbumin that serves as a specifier in the lactose synthase complex, the conditions under which HAMLET was formed resemble those in the stomach of the nursing child. Low pH is known to release Ca 2؉ from the highaffinity Ca 2؉ -binding site and to activate lipases that hydrolyze free fatty acids from milk triglycerides. We propose that this single amino acid polypeptide chain may perform vastly different biological functions depending on its folding state and the in vivo environment. It may be speculated that molecules like HAMLET can aid in lowering the incidence of cancer in breast-fed children by purging of tumor cells from the gut of the neonate.

To the breast-fed infant, human milk is more than a source of nutrients; it furnishes a wide array of molecules that restrict microbes, such as antibodies, bactericidins, and inhibitors of bacterial adherence. However, it has rarely been considered that human milk may also contain substances bioactive toward host cells. While investigating the effect of human milk on bacterial adherence to a human lung cancer cell line, we were surprised to discover that the milk killed the cells. Analysis of this effect revealed that a component of milk in a particular physical state-multimeric a-lactalbumin-is a potent Ca2+-elevating and apoptosis-inducing agent with broad, yet selective, cytotoxic activity. Multimeric a-lactalbumin killed all transformed, embryonic, and lymnphoid cells tested but spared mature epithelial elements.These findings raise the possibility that milk contributes to mucosal immunity not only by furnishing antimicrobial molecules but also by policing the function of lymphocytes and epithelium. Finally, analysis of the mechanism by which multimeric a-lactalbumin induces apoptosis in transformed epithelial cells could lead to the design of antitumor agents.Through programmed cell death the human body eliminates unwanted cells without evoking an inflammatory response. Cells undergoing programmed cell death show a distinct morphological appearance characterized by cell shrinkage, membrane blebbing, nuclear condensation, and fragmentation with the formation of "apoptotic bodies"; this type of cell death is generally referred to as apoptosis (1, 2).Human milk provides the breast-fed child not only with nutrients but also with a mucosal immune -system. Milk contains a wide array of molecules with antimicrobial activity: antibodies to bacterial, viral, and protozoal antigens (3-5); potentially bactericidal molecules like lysozyme and lactoferrin; fatty acids that lyse' bacteria and viral particles; and glycoconjugates that inhibit bacterial adherence to epithelial cells (6-8). These components reach mucosal surfaces in the respiratory and gastrointestinal tracts of the breast-fed child and are thought to interfere with various steps in the pathogenesis of infections at these sites (8, 9). As a result, breastfeeding protects the infant from respiratory and gastrointestinal infections.During our recent studies of human milk and its antibacterial properties, we observed that transformed cell lines exposed to human milk underwent morphological changes compatible with apoptosis. The active component was identified as multimeric a-lactalbumin (MAL), which was found to induce apoptosis in a variety of transformed and immature mammalian cells but not in other cells. This report describes these effects and provides preliminary characterization of the cytotoxic mechanism. MATERIALS AND METHODSMaterials. Human and bovine a,-lactalbumin, bovine serum albumin (BSA), human and chicken lysozyme, human lactoferrin, and cycloheximide were from Sigma. Thapsigargin was from Gibco.Cells. The A549, NCI H292, A-498, J 82, C...

Lyme disease is very common in southern Sweden, with a relatively high frequency of neurologic complications and arthritis. With the exception of the low incidence of carditis, the pattern of disease we found in Sweden was similar to that reported in the United States.