Immuno-Colorimetric Neutralization Test: A Surrogate for Widely Used Plaque Reduction Neutralization Tests in Public Health Virology

Abstract

Since their first documentation in 1952, plaque reduction neutralization tests (PRNTs) have become the choice of test for the measurement of neutralizing antibodies against a particular virus. However, PRNTs can be performed only against viruses that cause cytopathic effects (CPE). PRNTs also require skilled personnel and can be time-consuming depending on the time required for the virus to cause CPE. Hence, their application limits large-scale studies or epidemiological and laboratory investigations. Since 1978, many surrogate PRNTs or immunocolorimetric assay (ICA)-based focus reduction neutralization tests (FRNT) have been developed. In this article, ICAs and their utility in FRNTs for the characterization of neutralizing antibodies, homologous or heterologous cross-neutralization, and laboratory diagnosis of viruses of public health importance have been discussed. Additionally, possible advancements and automations have been described that may help in the development and validation of novel surrogate tests for emerging viruses.

Clinical validation of an RSV neutralization assay and testing of cross-sectional sera pre- and post- RSV outbreaks from 2021-2023

“…In addition, the past two years have seen global resurgence of aseasonal RSV infections thought to be related to limited circulation and immunity debt attributed to the COVID-19 pandemic [3,[5][6][7][8]. These developments necessitate monitoring population immunity and vaccine immunogenicity, both best assessed by measuring neutralizing antibodies against RSV [9][10][11][12]. RSV neutralizing antibody titer is a major correlate of protection, with higher neutralizing titers being associated with lower viral load and reduced risk of severe RSV-induced disease [13][14][15][16][17][18].…”

“…The standard for neutralization assays, the plaque-reduction neutralization test (PRNT), requires 3-5 days of incubation time and is less amenable to high-throughput applications [12]. An alternative is the focus-reduction neutralization test (FRNT), which often requires less sample, reagent volume, and incubation time (26-30 hours) to measure neutralizing titers.…”