Anti-InlA single-domain antibodies that inhibit the cell invasion of Listeria monocytogenes
Taichi Yamazaki, Satoru Nagatoishi, Tsukushi Yamawaki, Takashi Nozawa, Ryo Matsunaga, Makoto Nakakido, José M. M. Caaveiro, Ichirô Nakagawa, Kouhei Tsumoto
Abstract
Listeriosis, caused by infection with Listeria monocytogenes , is a severe disease with a high mortality rate. The L. monocytogenes virulence factor, internalin family protein InlA, which binds to the host receptor E-cadherin, is necessary to invade host cells. Here, we isolated two single-domain antibodies (V H Hs) that bind to InlA with picomolar affinities from an alpaca immune library using the phage display method. These InlA-specific V H Hs inhibited the binding of InlA to the extracellular domains of E-cadherin in vitro as shown by biophysical interaction analysis. Furthermore, we determined that the V H Hs inhibited the invasion of L. monocytogenes into host cells in culture. High-resolution X-ray structure analyses of the complexes of V H Hs with InlA revealed that the V H Hs bind to the same binding site as E-cadherin against InlA. We conclude that these V H Hs have the potential for use as drugs to treat listeriosis.