Application of a Receptor-Binding-Domain-Based Simple Immunoassay for Assessing Humoral Immunity against Emerging...

Area of Science:

• Immunology
• Virology
• Biotechnology

Background:

• Emerging SARS-CoV-2 variants pose a continuous threat to public health.
• Assessing humoral immunity against these variants is crucial for vaccine efficacy and therapeutic strategies.
• Existing methods for antibody detection can be time-consuming or lack variant specificity.

Purpose of the Study:

• To develop a simple, rapid, and high-throughput enzyme-linked immunosorbent assay (ELISA) for assessing humoral immunity against SARS-CoV-2 variants.
• To validate the assay's performance against established methods and its applicability in real-world scenarios.
• To provide a tool for monitoring immune responses to vaccination and infection over time.

Main Methods:

• Engineered HEK cells to express His-tagged receptor-binding domain (RBD) proteins of SARS-CoV-2 variants.
• Purified RBD proteins using Ni-chromatography and buffer exchange via membrane filtration.
• Developed a simplified ELISA using single serum dilutions, purified RBD, and a chromogenic substrate for antibody detection.

Main Results:

• The RBD-based ELISA demonstrated strong correlation with a commercial immunoassay for Wuhan strain antibodies.
• Assay results correlated with direct virus neutralization assays against Wuhan and Omicron (BA.5) variants.
• The ELISA successfully assessed variant-specific humoral immunity in vaccinated and convalescent individuals, tracking vaccination responses.

Conclusions:

• The developed RBD-based ELISA is a simple, rapid, and high-throughput method for assessing humoral immunity against SARS-CoV-2 variants.
• This assay can be easily modified to detect immune responses to emerging viral strains.
• The tool aids in evaluating antiviral protection levels following vaccination or infection, supporting ongoing public health efforts.