Facile quantitative diagnostic testing for neutralizing antibodies against Chikungunya virus

Area of Science:

• Virology
• Immunology
• Infectious Diseases

Background:

• Viral neutralization tests (NT) are crucial for assessing immune status and evaluating vaccine/antibody potency.
• Conventional NTs like FRNT offer specificity but require BSL3 facilities for chikungunya virus (CHIKV), increasing costs and limiting accessibility.
• A safe surrogate virus neutralization test (sVNT) using CHIKV replicon particles (VRPs) was developed for rapid detection and quantification of neutralizing activity.

Purpose of the Study:

• To evaluate a novel, safe surrogate virus neutralization test (sVNT) for chikungunya virus (CHIKV).
• To assess the sensitivity, specificity, and reproducibility of sVNT using VRPs expressing eGFP and luciferase.
• To compare the performance of sVNT with the conventional focus reduction neutralization test (FRNT).

Main Methods:

• A case-control study utilized serum samples from CHIKV, dengue virus, Japanese encephalitis virus, and healthy individuals.
• Mosquito cell-derived CHIK VRPs were used for sVNT to detect (eGFP) and quantify (Luc) neutralizing activity.
• Correlation analysis was performed between sVNT (20h) and FRNT (72h) using Pearson's correlation coefficient and sigmoidal curve fitting.

Main Results:

• sVNT-eGFP screening demonstrated 100% sensitivity and specificity.
• Quantitative sVNT-Luc assays showed a strong correlation (Pearson's r = 0.83) with FRNT for NT50 values.
• The sVNT method provided results within 24 hours, significantly faster than FRNT.

Conclusions:

• The VRP-based sVNT is a reliable and rapid method for identifying and quantifying CHIKV neutralizing activity in clinical samples.
• This assay offers a safe, cost-effective, and accessible alternative to BSL3-dependent FRNT for CHIKV.
• sVNT facilitates timely assessment of CHIKV immunity and therapeutic responses.