Analytical characterization of the SARS-CoV-2 EURM-017 reference material

Area of Science:

• Immunology
• Infectious Diseases
• Biotechnology

Background:

• Current SARS-CoV-2 serological assays lack standardization to a universal reference material, hindering result comparability.
• SARS-CoV-2 European Reference Material 017 (EURM-017) provides human sera with antibodies against SARS-CoV-2 proteins (S, S1 RBD, S2, N).
• Standardization is essential for comparing results across diverse laboratory-developed and commercial assays and publications.

Purpose of the Study:

• To characterize five antigen-specific serum fractions within EURM-017.
• To establish standardization methods for SARS-CoV-2 serology assays using EURM-017.
• To enable traceable comparisons of serological assay results globally.

Main Methods:

• Affinity purification and quantification of five antigen-specific serum fractions.
• Comparison of PRNT50 titers for neutralization activity.
• Development of standardization methods for anti-S1 RBD (IgG and Total Ig) and anti-N protein assays.
• Determination of assay index values and correlation with PRNT50 titers for patient sera.

Main Results:

• Quantified anti-sera protein content: S1 (17.7 µg/mL), S1 RBD (17.4 µg/mL), S1/S2 (34.1 µg/mL), S2 (29.7 µg/mL), and N protein (72.5 µg/mL).
• S1 anti-serum exhibited the highest neutralization activity.
• A linear equation (y=0.75x-0.10) was established for standardizing anti-S1 RBD IgG assays, showing strong correlation with PRNT50 titers (r=0.84).

Conclusions:

• Standardization of SARS-CoV-2 serology assays to EURM-017 antigen-specific anti-sera is achievable.
• This standardization ensures traceability to a single reference material, facilitating global comparison of assay results.
• The characterized reference material supports the development of reliable and comparable diagnostic tools for SARS-CoV-2.