Mapping population immunity: How protease and antibody fragmentation shape wastewater findings

Area of Science:

• Environmental microbiology
• Immunology
• Public health surveillance

Background:

• Wastewater-based surveillance traditionally uses nucleic acid detection.
• Antibody detection in wastewater offers a longer-term view of population immunity.
• Wastewater's complex matrix challenges immunoassay sensitivity.

Purpose of the Study:

• To assess the feasibility of detecting antigen-specific antibodies in wastewater.
• To identify and overcome challenges in wastewater antibody detection using immunoassays.
• To develop a modified protocol for reliable wastewater serology.

Main Methods:

• Analysis of antibody profiles in stool and wastewater samples.
• Evaluation of enzyme-linked immunosorbent assays (ELISA) performance.
• Investigation of wastewater protease effects on antigen-antibody interactions.
• Application of protease inhibitors and antibody concentration techniques.
• Quantification of SARS-CoV-2 specific antibodies (RBD and N protein).

Main Results:

• Antibodies in wastewater exist as cleaved fragments retaining antigen-binding domains.
• Wastewater proteases interfere with ELISA by altering antigens in an antigen-dependent manner.
• Protease inhibitors and an anti-CH1 based ELISA improved detection sensitivity.
• A modified protocol successfully detected and quantified SARS-CoV-2 specific antibodies.

Conclusions:

• Wastewater-based serology is a viable tool for population-level infection surveillance.
• Optimized immunoassay protocols can overcome challenges posed by wastewater components.
• Detecting antibodies in wastewater provides valuable insights into past infections and population immunity.