Kiyoshi Moriyama

By Yoshifumi Naito, Kiyoshi Moriyama and Teiji Sawa

Propagation of multidrug‐resistant Pseudomonas aeruginosa, which causes endemic nosocomial infections, has become a major concern in various parts of the world. In patients with cystic fibrosis, a major cause of death is respiratory tract infections with antibiotic‐resistant P. aeruginosa. This condition has prompted medical research aimed at developing effective prophylaxis and treatments that do not rely on conventional antimicrobial agents. The pathogenesis that results in cytotoxicity and mortality in immunocompromised patients infected with P. aeruginosa is associated with the type III secretion system of this bacterium. Clinical isolates that are cytotoxic and drug‐resistant are involved in acute exacerbation of chronic infectious diseases. The P. aeruginosa V‐antigen PcrV, a Yersinia V‐antigen LcrV homolog, is involved as an indispensable component in the translocational process of type III secretory (TTS) toxins. Vaccination against PcrV ensures survival of infection‐challenged mice and decreases lung inflammation and injury. Furthermore, anti‐PcrV IgG can inhibit translocation of TTS toxins. These observations support the hypothesis that anti‐PcrV strategies have the potential as nonantibiotic immune strategies for preventing aggravation of P. aeruginosa infections in patients with cystic fibrosis.

Part of the book: Progress in Understanding Cystic Fibrosis

By Teiji Sawa, Atsushi Kainuma, Kiyoshi Moriyama and Yoshifumi Naito

Pseudomonas aeruginosa, a Gram-negative pathogen, causes life-threatening infections. Lung injury and the development of sepsis depend largely on expression of the virulence genes associated with the type III secretion system of this bacterium. The type III secretion system functions as a molecular syringe to deliver type III secretory toxins directly into the cytosol of eukaryotic cells and also acts to inhibit innate immune mechanisms, thereby preventing bacterial clearance. Antibodies against PcrV, the cap structure in the translocational needle of type III secretory apparatus of P. aeruginosa, block toxin translocation of the type III secretion system. We have been investigating the therapeutic use of a recombinant anti-PcrV single-chain antibody. In this chapter, as a preliminary step toward an antibody-based immunotherapy against bacterial infections, we summarize our experience of constructing a recombinant single-chain antibody (called scFv166), in which the heavy (VH) and light chain (VL) variable regions of the anti-PcrV monoclonal IgG are joined by a flexible peptide linker. The practical methodologies used to make recombinant scFv166 against a bacterial protein component are described in detail.

Part of the book: Antibody Engineering