However, besides MRP and EF, additional proteins may be important in the pathogenesis of an infection (5, 8, 9, 13, 14, 28, 29)

However, besides MRP and EF, additional proteins may be important in the pathogenesis of an infection (5, 8, 9, 13, 14, 28, 29). a polypeptide linker to form a single-chain fragment (scFv). These scFvs are fused to a minor coat protein of bacteriophage M13, pIII, resulting in phages showing antibody fragments. The display of scFvs on a filamentous phage offers the possibility to select phage antibodies without using hybridoma technology. Phage antibodies are selected by panning the library for a number of rounds on an immobilized antigen. At present, large synthetic libraries are available, which are created from unrearranged V gene segments from nonimmunized healthy human being donors. These libraries can be used to select antibodies against any given antigen, including foreign antigens, self antigens, nonimmunogenic antigens, and harmful antigens (30). In addition, subtractive selection strategies to select for phage antibodies against differentially indicated structures on the surface of different cell types, like thymic cells (25) and human being blood cells (16), as well as against proteins differentially indicated on two types of strains of the gram-negative bacterium (2), have been described. is definitely a gram-positive bacterium that can cause severe infections in pigs. Young pigs can suffer from meningitis, septicemia, and arthritis and often do not survive an infection Benzyl chloroformate (3, 27). Occasionally, can also cause meningitis in humans (1). Until now, no effective vaccines have been available. Besides, very little is known of in general and its pathogenesis in particular. This makes it difficult to control the disease. So far, 35 capsular serotypes of have been explained (6, 7, 12, 19). Worldwide, serotype 2 is the most frequently isolated serotype. Strains of serotype 2 can differ in their virulence: pathogenic, weak-pathogenic, and nonpathogenic strains are acknowledged (26, 28). Previously, we showed that the manifestation of two proteins, muramidase-released protein (MRP) and extracellular element (EF) is strongly associated with pathogenic strains of serotype 2 (28, 29). Consequently, these proteins are considered virulence markers for serotype 2. MSN However, besides MRP and EF, additional proteins may be important in the pathogenesis of an infection (5, 8, 9, 13, 14, 28, 29). The use of a phage display library may be of Benzyl chloroformate great help in identifying these proteins and in determining the difference between pathogenic and nonpathogenic strains. Since a considerable number of virulence Benzyl chloroformate factors of pathogenic bacteria are either secreted or located on the cell surface, we first tried to select phage antibodies against whole cells of a virulent strain of serotype 2. In addition, phage antibodies were selected against EF. Finally, phage antibodies were selected against cell-associated constructions of a pathogenic strain of after subtraction having a nonpathogenic strain. Three unique anti-EF phage antibodies, as well as three unique anti-phage antibodies, were selected. After subtraction, one phage antibody remained, which acknowledged EF. Benzyl chloroformate These data clearly show the successful selection of a phage antibody directed against a protein exclusively expressed by a pathogenic strain of serotype 2 and that EF is a very dominant protein in phage antibody selections. MATERIALS AND METHODS Bacterial strains and growth conditions. Two strains were used in this study Benzyl chloroformate as hosts for bacteriophages: TG1 [K-12 ((strain 10 expresses EF and MRP, while strain T15 does not (23, 29). Strain 10 was proven to be pathogenic,.