Development and validation of a quantitative, non-invasive, highly sensitive and specific, electrochemical assay for anti-SARS-CoV-2 IgG antibodies in saliva

Abstract

Amperial™ is a novel assay platform that uses immobilized antigen in a conducting polymer gel followed by detection via electrochemical measurement of oxidation-reduction reaction between H2O2/Tetrametylbenzidine and peroxidase enzyme in a completed assay complex. A highly specific and sensitive assay was developed to quantify levels of IgG antibodies to SARS-CoV-2 in saliva. After establishing linearity and limit of detection we established a reference range of 5 standard deviations above the mean. There were no false positives in 667 consecutive saliva samples obtained prior to 2019. Saliva was obtained from 34 patients who had recovered from documented COVID-19 or had documented positive serologies. All of the patients with symptoms severe enough to seek medical attention had positive antibody tests and 88% overall had positive results. We obtained blinded paired saliva and plasma samples from 14 individuals. The plasma was analyzed using an EUA-FDA cleared ELISA kit and the saliva was analyzed by our Amperial™ assay. All 5 samples with negative plasma titers were negative in saliva testing. Eight of the 9 positive plasma samples were positive in saliva and 1 had borderline results. A CLIA validation was performed as a laboratory developed test in a high complexity laboratory. A quantitative non-invasive saliva based SARS-CoV-2 antibody test was developed and validated with sufficient specificity to be useful for population-based monitoring and monitoring of individuals following vaccination.

Natural SARS-CoV-2 Infection Affects Neutralizing Activity in Saliva of Vaccinees

“…SARS-CoV-2 is an airborne virus that infects epithelial cells of the mucosa of the upper airways to eventually spread further, causing pulmonary and multi-organ infection and damage in some patients ( 20 ). Several studies have shown that saliva contains infectious SARS-CoV-2 particles in both symptomatic and asymptomatic individuals, and it can provide useful information on local immunity at the primary site of virus acquisition ( 8 , 19 , 21 , 22 ). Such knowledge is of pivotal importance for the development of effective immunomodulatory strategies to prevent and cure the infection, including vaccines.…”

A Novel Approach for Evaluating Antibodies Against SARS-CoV-2 Using Menstrual Blood Collected from Sanitary Napkins Before and after Vaccination and Evaluation of the Visual Napkin Score

“…Since saliva is a non-invasive specimen for vaccination or antibody evaluation after SARS-CoV-2 infection, studies have been conducted on its usefulness as described above 20,24 . Like saliva, menstrual blood in a napkin can be collected non-invasively, but the napkin may have the advantage of being a wearable device.…”

Variability in SARS-Cov-2 IgG Antibody Affinity To Omicron and Delta Variants in Convalescent and Community mRNA Vaccinated Individuals

“…As previously described, the Amperial® platform uses an integrated electrode and electrochemical reader system (EZLife Bio Inc, Los Angeles, CA) to read the oxidation-reduction byproduct of the antibody capture process. The detailed description of the Amperial® COVID-19 Antibody assay and the assay performance and validation have been described previously (3). We reported the utility of this assay in monitoring the kinetics of antibody response (4) using immobilized S1 subunit to the wild-type virus immobilized in a conducting gel on the surface of the gold electrode.…”

“…Our laboratory has previously developed a non-invasive saliva-based quantitative biosensor assay for Anti-S1 IgG antibody levels to the wild-type SARS-CoV-2 using a proprietary platform called AMPERIAL™. We demonstrated that this assay is highly specific to COVID-19 infection (3) and can be used to serially monitor vaccinated patients for waning antibody levels (4). As the COVID-19 pandemic continues with a number of variants being monitored to determine their potential harm and differences in transmission rate, a major point of interest is whether existing mRNA vaccines based on the wild-type S1 sequence would remain efficacious with successive new variants.…”