Despite the huge decrease in deaths caused by Shigella worldwide in recent decades,
shigellosis still causes over 200,000 deaths every year. No
vaccine is currently available, and the morbidity of the disease coupled with the rise of antimicrobial resistance renders the introduction of an effective
vaccine extremely urgent. Although a clear immune correlate of protection against
shigellosis has not yet been established, the demonstration of the bactericidal activity of
antibodies induced upon vaccination may provide one means of the functionality of
antibodies induced in protecting against Shigella. The method of choice to evaluate the
complement-mediated functional activity of
vaccine-induced
antibodies is the Serum Bactericidal Assay (SBA). Here we present the development and intra-laboratory characterization of a high-throughput luminescence-based SBA (L-SBA) method, based on the detection of
ATP as a proxy of surviving bacteria, to evaluate the
complement-mediated killing of human sera. We demonstrated the high specificity of the assay against a homologous strain without any heterologous aspecificity detected against species-related and non-species-related strains. We assessed the linearity, repeatability and reproducibility of L-SBA on human sera. This work will guide the bactericidal activity assessment of clinical sera raised against S. sonnei. The method has the potential of being applicable with similar performances to determine the bactericidal activity of any non-clinical and clinical sera that rely on
complement-mediated killing.