Development and validation of a pseudotyped virus neutralization assay for quantification of anti-Lassa virus...

Lassa virus is endemic in many West African countries and has significant epidemic/pandemic potential. The Coalition for Epidemic Preparedness Innovations (CEPI) Centralized Laboratory Network (CLN) is developing validated, harmonized methods to support and accelerate vaccine development in the event of an outbreak. We present here the development and validation of an assay to quantify anti-Lassa virus neutralizing antibodies. As the method uses a pseudotyped virus (PV) instead of authentic Lassa virus-a pathogen listed as hazard group 4-it can be performed at a lower containment level, making it widely accessible especially in those regions where Lassa fever is circulating.

A recombinant vesicular stomatitis virus (rVSV)-based pseudotyped virus neutralization assay (PVNA) was developed. A working standard was prepared and calibrated against the International Standard (IS) for Lassa virus neutralizing antibodies, enabling results to be expressed in International Units. The method was validated according to the International Council for Harmonisation (ICH) Q2(R2) guidelines.

The rVSV-based PVNA was successfully developed and validated. The analytical range of the assay was established as 10-100 IU/mL, and seropositive samples from a Lassa vaccine clinical trial fell within this range. Results from the PVNA showed direct correlation with results obtained from authentic virus neutralization methods. The method was, therefore, concluded to be fit-for-purpose.

We have successfully developed and validated a PVNA for the quantification of neutralizing antibodies against Lassa virus. We have also provided a practical example of how to calibrate a serological method to the WHO International Standard to achieve greater harmonization and comparability between studies. The method is now being transferred to partner laboratories within the CLN to enable harmonized testing of clinical trial samples and support the development and evaluation of Lassa vaccine candidates.