Development and qualification of an enzyme-linked immunosorbent assay to detect human serum immunoglobulin G reactive to multiple lineages of Lassa virus nucleoprotein

Abstract

Lassa fever is a severe, often fatal febrile illness endemic to West Africa caused by Lassa virus (LASV), with different virus lineages predominating across West African countries. The viral nucleoprotein (NP) is a target antigen for serological assays to identify previous exposure to LASV. To our knowledge, there is no commercially available assay that reliably quantifies anti-LASV-NP IgG antibodies in human serum. We report the development and qualification of an ELISA designed to detect and quantify anti-LASV-NP IgG in human serum samples. Following assay optimization, performance was assessed through assay qualification at clinical trial laboratories within Ghana. Assay positivity criteria, lower limit of detection, upper and lower limits of quantification, inter-assay precision, selectivity and dilutional linearity were determined. A new reference standard prepared from pooled sera from donors in endemic Lassa fever regions was established and calibrated to the first WHO international standard for LASV antibodies. One ELISA assay utilizing lineage IV LASV-NP was applicable for detection of anti-LASV-NP IgG antibodies in serum samples from different West African countries where either LASV lineages I, II, III and IV predominate. The ELISA remained selective in hemolysed serum samples with minimal loss of signal across repeated sample freeze-thaw cycles. Crucially, the developed ELISA was fully concordant with a now discontinued commercially available ELISA kit for quantification of anti-LASV-NP antibodies. Our anti-LASV-NP IgG ELISA was shown to reliably measure anti-LASV-NP IgG levels in human serum. Establishing and conducting this assay within West Africa represents an essential step towards strengthening LASV epidemiology research and supporting urgently needed development of a vaccine to prevent Lassa Fever.