Validation of the Rapid Fluorescent Focus Inhibition Test for Rabies Virus Neutralizing Antibodies - China, 2025

Area of Science:

• Immunology
• Virology
• Vaccinology

Background:

• The rapid fluorescent focus inhibition test (RFFIT) is the gold standard for quantifying rabies virus neutralizing antibodies (RVNA).
• RFFIT is crucial for assessing rabies vaccine efficacy and protective immunity in humans and animals.
• Thorough validation of RFFIT is essential for ensuring reliable results.

Purpose of the Study:

• To validate the RFFIT assay for quantifying rabies virus neutralizing antibodies (RVNA) in serum samples.
• To ensure the reliability and accuracy of RFFIT for biological efficacy assessments of rabies vaccines.

Main Methods:

• Validation of RFFIT according to FDA and ICH Q2 (R1) guidelines.
• Assessment of assay parameters including precision, dilutability, linearity, range, accuracy, specificity, robustness, and stability.
• Utilized the third World Health Organization international standard for anti-rabies immunoglobulin (WHO-3 SRIG) and negative human sera.

Main Results:

• RFFIT demonstrated good precision (intra-assay and intermediate-precision GCV <30%).
• Assay showed acceptable dilutability, linearity, and accuracy (95.56% recovery within 70%-130%).
• Specificity was confirmed, and the assay proved robust and stable under various conditions.

Conclusions:

• The RFFIT assay was successfully validated for the reliable quantification of RVNA.
• Validated RFFIT provides a dependable method for evaluating rabies vaccine efficacy and immunity.