High-Throughput Luminescence-Based Serum Bactericidal Assay Optimization and Characterization to Assess Human Sera...

Area of Science:

• Microbiology
• Immunology
• Vaccinology

Background:

• Shigellosis is a major global health threat, especially in children under 5 in low- and middle-income countries (LMICs), linked to stunting and antimicrobial resistance.
• An effective vaccine for broad protection against diverse Shigella serotypes is urgently needed.
• Anti-O-Antigen-specific IgG and its functionality via Serum Bactericidal Assay (SBA) are considered crucial correlates of protection.

Purpose of the Study:

• To characterize and extend a high-throughput luminescence-based SBA (L-SBA) to seven prevalent Shigella serotypes.
• To validate the assay's performance for analyzing functional antibody responses against Shigella.

Main Methods:

• Refinement and extension of a previously developed L-SBA for Shigella sonnei and S. flexneri serotypes 1b, 2a, 3a.
• Characterization of the L-SBA for five additional serotypes: S. flexneri 4a, 5b, 6, X, and Y.
• Evaluation of assay repeatability, precision, linearity, specificity, and limit of detection/quantification using human sera and baby rabbit complement.

Main Results:

• The L-SBA was successfully extended to cover seven widespread Shigella serotypes.
• Assay characterization confirmed its repeatability, intermediate precision, linearity, and specificity.
• No significant impact on L-SBA output was observed with different sources of baby rabbit complement.

Conclusions:

• The developed L-SBA is a robust tool for analyzing functional antibody responses against a broad range of Shigella serotypes.
• This assay can facilitate epidemiological studies on natural Shigella infections and assess the efficacy of candidate vaccines in eliciting cross-functional antibodies.
• The L-SBA supports the development of vaccines offering broad protection against prevalent Shigella strains.