No abstract

Leptospirosis, the most widespread zoonosis in the world, is an emerging public health problem, particularly in large urban centers of developing countries. Several pathogenic species of the genus Leptospira can cause a wide range of clinical manifestations, from a mild, flu-like illness to a severe disease form characterized by multiorgan system complications leading to death. However, the mechanisms of pathogenesis of Leptospira are largely unknown. This article will address the animal models of acute and chronic leptospire infections, and the recent developments in the genetic manipulation of the bacteria, which facilitate the identification of virulence factors involved in pathogenesis and the assessment of their potential values in the control and prevention of leptospirosis.

Since its identification nearly 30 years ago, Lyme disease has continued to spread, and there have been increasing numbers of cases in the northeastern and north central US. The Lyme disease agent, Borrelia burgdorferi, causes infection by migration through tissues, adhesion to host cells, and evasion of immune clearance. Both innate and adaptive immune responses, especially macrophage- and antibody-mediated killing, are required for optimal control of the infection and spirochetal eradication. Ecological conditions favorable to the disease, and the challenge of prevention, predict that Lyme disease will be a continuing public health concern

SummaryThe spirochaetal agents of Lyme disease, Borrelia burgdorferi (sensu lato) bind to integrins ␣ IIb ␤ 3 , ␣ v ␤ 3 and ␣ 5 ␤ 1 in purified form and on the surfaces of human cells. Using a phage display library of B. burgdorferi (sensu stricto) DNA, a candidate ligand for ␤ 3 -chain integrins was identified. The native B. burgdorferi protein, termed p66, is known to be recognized by human Lyme disease patient sera and to be expressed on the surface of the spirochaete. We show here that recombinant p66 binds specifically to ␤ 3 -chain integrins and inhibits attachment of intact B. burgdorferi to the same integrins. When expressed on the surface of Escherichia coli, this protein increases the attachment of E. coli to a transfected cell line that expresses ␣ v ␤ 3 , but not to the parental cell line, which expresses no ␤ 3 -chain integrins. Localization of p66 on the surface of B. burgdorferi, the ability of recombinant forms of the protein to bind to ␤ 3 -chain integrins and the fact that p66 and B. burgdorferi bind to ␤ 3 -chain integrins in a mutually exclusive manner make p66 an attractive candidate bacterial ligand for integrins ␣ IIb ␤ 3 and ␣ v ␤ 3 .

Exoenzyme S (ExoS), which has been implicated as a virulence factor of Pseudomonas aeruginosa, catalyzes transfer of the ADP-ribose moiety of NADI to many eukaryotic cellular proteins. Its preferred substrates include Ras and several other 21-to 25-kDa GTP-binding proteins.

Lyme disease is a chronic, multisystemic infection caused by the tick-borne spirochete Borrelia burgdor- One-letter code is used for amino acids.tTo whom reprint requests should be addressed.7059

Borrelia burgdorferi, the agent of Lyme disease, expresses several adhesion molecules that are probably required for initial establishment of infection in mammalian hosts, and for colonization of various tissues within the host. The B. burgdorferi outer membrane protein P66 was previously identified as a ligand for ␤3-chain integrins by using a variety of biochemical approaches. Although the earlier data suggested that P66 is an adhesin that mediates B. burgdorferi attachment to ␤3-chain integrins, lack of genetic systems in B. burgdorferi precluded definitive demonstration of a role for P66 in ␤3 integrin attachment by intact borreliae. Recent advances in the genetic manipulation of B. burgdorferi have now made possible the targeted disruption of the p66 gene. Mutants in p66 show dramatically reduced attachment to integrin ␣v␤3. This is, to our knowledge, the first description of the targeted disruption of a candidate B. burgdorferi virulence factor with a known biochemical function that can be quantified, and demonstrates the importance of B. burgdorferi P66 in the attachment of this pathogenic spirochete to a human cell-surface receptor.

SummaryBorrelia burgdorferi, the agent of Lyme disease, disseminates from the site of deposition by Ixodes ticks to cause systemic infection. Dissemination occurs through the circulation and through tissue matrices, but the B. burgdorferi molecules that mediate interactions with the endothelium in vivo have not yet been identified. In vivo selection of filamentous phage expressing B. burgdorferi protein fragments on the phage surface identified several new candidate adhesins, and verified the activity of one adhesin that had been previously characterized in vitro. P66, a B. burgdorferi ligand for b 3-chain integrins, OspC, a protein that is essential for the establishment of infection in mammals, and Vls, a protein that undergoes antigenic variation in the mammal, were all selected for binding to the murine endothelium in vivo. Additional B. burgdorferi proteins for which no functions have been identified, including all four members of the OspF family and BmpD, were identified as candidate adhesins. The use of in vivo phage display is one approach to the identification of adhesins in pathogenic bacteria that are not easily grown in the laboratory, or for which genetic manipulations are not straightforward.