Single domain llama antibodies as specific intracellular inhibitors as SpvB, the actin ADP-ribosylating toxin of Salmonella typhimurium

VANINA ALZOGARAY; WELBECK DANQUAH; ANDRÉS AGUIRRE; MARIELA URRUTIA; PAULA BERGUER; ELEONORA GARCÍA VÉSCOVI; FRIEDRICH HAAG; FRIEDRICH KOCH-NOLTE; FERNANDO GOLDBAUM

Ghent

Congreso; Single Domain Antibodies Come of Age; 2010

ADP-ribosylation of host cell proteins is a common mode of cell intoxication by pathogenic bacterial toxins. Antibodies induced by immunization with inactivated ADP-ribosylating toxins provide efficient protection in case of some secreted toxins, e.g. diphtheria and pertussis toxins. However, other ADP-ribosylating toxins such as Salmonella SpvB toxin, are directly secreted from the Salmonella-containing vacuole into the cytosol of target cells via the SPI-2 encoded bacterial type III secretion system and thus, inaccessible to conventional antibodies. Small molecule ADP-ribosylation inhibitors are fraught with potential side effects caused by inhibition of endogenous ADP-ribosyltransferases. Here we report the development of a single domain antibody from an immunized llama that blocks the capacity of SpvB to ADP-ribosylate actin at a molar ratio of 1:1. The single domain antibody, when expressed as an intrabody, effectively protected cells from the cytotoxic activity of a translocation competent chimeric C2IN-C/SpvB toxin. Transfected cells were also protected against cytoskeletal alterations induced by wild type SpvB-expressing strains of Salmonella. This proof of principle paves the way for developing new antidotes against intracellular toxins.