ABSTRACT
SARS-CoV-2 viremia has been demonstrated in some patients using molecular assays. Here we demonstrate detection of SARS-CoV-2 antigen in a cohort of hospitalized patients using a rapid diagnostic test from Anhui Deepblue Medical Technology Co., Ltd. We detected antigen in serum from 11 of 13 patients at time points ranging from three to eighteen days from symptom onset and observed that the disappearance of an antigen signal was associated with seroconversion. These results demonstrate proof of principle use of a rapid antigen test with serum samples in a format compatible with point of care testing.
Subject(s)
ViremiaABSTRACT
As increasing numbers of people recover from and are vaccinated against COVID-19, tests are needed to measure levels of protective, neutralizing antibodies longitudinally to help determine duration of immunity. We developed a lateral flow assay (LFA) that measures levels of neutralizing antibodies in plasma, serum or whole blood. The LFA is based on the principle that neutralizing antibodies inhibit binding of the spike protein receptor-binding domain (RBD) to angiotensin-converting enzyme 2 (ACE2). The test classifies high levels of neutralizing antibodies in sera that were titered using authentic SARS-CoV-2 and pseudotype neutralization assays with an accuracy of 98%. Sera obtained from patients with seasonal coronavirus did not prevent RBD from binding to ACE2. As a demonstration for convalescent plasma therapy, we measured conversion of non-immune plasma into strongly neutralizing plasma. This is the first report of a neutralizing antibody test that is rapid, highly portable and relatively inexpensive that might be useful in assessing COVID-19 vaccine immunity.
Subject(s)
COVID-19ABSTRACT
Coronavirus disease 2019 (COVID-19) is a potentially life-threatening respiratory infection caused by severe acute respiratory coronavirus 2 (SARS-CoV-2), for which numerous serologic assays are available. In a CLIA laboratory setting, we used a retrospective sample set (n = 457) to evaluate two lateral flow immunoassays (LFIAs; two iterations of Rapid Response COVID-19 Test Cassette, BTNX Inc.) and a subset of to evaluate SARS-COV-2 IgG/IgM Rapid Test, ACON Laboratories (n = 200); and Standard Q COVID-19 IgM/IgG Duo, SD BIOSENSOR (n = 155) for their capacity to detect of SARS-CoV-2 IgG. In a cohort of primarily hospitalized patients with RT-PCR confirmed COVID-19, the BTNX assays demonstrated 95% and 92% agreement with the Abbott SARS-CoV-2 IgG assay and sensitivity was highest at [≥] 14 days from symptom onset [BTNX kit 1, 95%; BTNX kit 2, 91%]. ACON and SD assays demonstrated 99% and 100% agreement with the Abbott assay at [≥] 14 days from symptom onset. Specificity was measured using 74 specimens collected prior to SARS-CoV-2 circulation in the United States and 31 "cross-reactivity challenge" specimens, including those from patients with a history of seasonal coronavirus infection and was 98% for BTNX kit 1 and ACON and 100% for BTNX kit 2 and SD. Taken with data from EUA assays, these results suggest that LFIAs may provide adequate results for rapid detection of SARS-CoV-2. Replicating these results in fingerstick blood in outpatient populations, would further support the possibility that LFIAs may be useful to increase access to serologic testing