Field validation of recombinant antigen immunoassays for diagnosis of Lassa fever

Abstract

Lassa fever, a hemorrhagic fever caused by Lassa virus (LASV), is endemic in West Africa. It is difficult to distinguish febrile illnesses that are common in West Africa from Lassa fever based solely on a patient’s clinical presentation. The field performance of recombinant antigen-based Lassa fever immunoassays was compared to that of quantitative polymerase chain assays (qPCRs) using samples from subjects meeting the case definition of Lassa fever presenting to Kenema Government Hospital in Sierra Leone. The recombinant Lassa virus (ReLASV) enzyme-linked immunosorbant assay (ELISA) for detection of viral antigen in blood performed with 95% sensitivity and 97% specificity using a diagnostic standard that combined results of the immunoassays and qPCR. The ReLASV rapid diagnostic test (RDT), a lateral flow immunoassay based on paired monoclonal antibodies to the Josiah strain of LASV (lineage IV), performed with 90% sensitivity and 100% specificity. ReLASV immunoassays performed better than the most robust qPCR currently available, which had 82% sensitivity and 95% specificity. The performance characteristics of recombinant antigen-based Lassa virus immunoassays indicate that they can aid in the diagnosis of LASV Infection and inform the clinical management of Lassa fever patients.

Diagnostics for Lassa fever virus: a genetically diverse pathogen found in low-resource settings

“…As more lineages and clades are revealed, and as mutations occur, tests will need to be revalidated and enriched to encompass variations observed at the nucleotide (20%–25%) and amino acid (8%–12%) levels 66. For some use cases, tests developed for a specific lineage or region may be appropriate; other cases may require detection of all known strains 62 105–108…”

“…While genetic sequence diversity and minor genetic mutations typically have less of an impact on protein sequence, early antigen tests have shown some variation in LASV lineage sensitivity. In tandem, detection of LASV NP antigen and anti-LASV IgM demonstrated 88% sensitivity and 90% specificity for early stage infection, sufficient for diagnosis in ~90% of PCR-positive cases 108 131…”

“…LASV RDTs, which leverage the same antibody/antigen capture agents as an ELISA but packaged in a stripped-down lateral flow format, can play an important role for patient care and outbreak response in outlying laboratories and clinics. A dipstick-based RDT for LASV has been developed that detects NP from fingerstick whole blood specimens 7 108 134 135. For LASV lineage IV (Josiah strain), the dipstick LASV RDT performed with good sensitivity (91% sensitivity, 86% specificity) compared with its progenitor ELISA (94% sensitivity, 84% specificity; both relative to qPCR).…”

“…For LASV lineage IV (Josiah strain), the dipstick LASV RDT performed with good sensitivity (91% sensitivity, 86% specificity) compared with its progenitor ELISA (94% sensitivity, 84% specificity; both relative to qPCR). The monoclonal capture agents developed for this LASV RDT showed reduced sensitivity to LASV lineages II and III; improvements to the assay using a polyclonal approach suggest increased pan-lineage antigen sensitivity 108…”

Detection of Antibody and Antigen for Lassa Virus Nucleoprotein in Monkeys from Southern Nigeria

“…The ELISA Kit used for the LASV NP antigen assay has been shown to have 95% sensitivity and 97% specificity when compared with standard quantitative polymerase chain reaction [16]. However, performance characteristics of the LASV NP IgG and IgM assays have not been published.…”