Stability of SARS-CoV-2 IgG in multiple laboratory conditions and blood sample types

Abstract

BACKGROUND : COVID-19 seroprevalence studies use serum/plasma samples to detect SARS-CoV-2 IgG. Data supporting alternate specimen types and freeze-thaw antibody stability is lacking. The stability of IgG and other immunoglobulins in multiple blood sample types stored in differing conditions and multiple freeze-thaw cycles (FTCs) was evaluated. MATERIALS AND METHODS : Serum, plasma, and heparinized-plasma samples were collected from COVID-19 recovered individuals. Samples underwent testing for SARS-CoV-2 antibodies upon collection, after each of 10-12 FTCs, and storage at -70°C, -20°C, 4°C, and room-temperature for 10-12 days using four high-throughput commercial assays, two rapid-test cassettes, a manual ELISA, and a surrogate neutralization assay. RESULTS : All three specimen types were collected from 34 COVID-19 recovered seropositive individuals (≥21 days post-symptoms). Using the Architect and Liaison assays, a positive qualitative SARS-CoV-2 IgG result was detected daily up to 12 FTCs and up to 10 days of storage at different temperatures. An additional 25 plasma samples consistently demonstrated detection of SARS-CoV-2 antibodies daily after 12 FTCs and storage at -20°C using two rapid test cassette assays (SD Biosensor and Hangzhou All Test), manual (Beijing Wantai) and surrogate neutralization (GenScript) ELISAs, and two high-throughput assays (Roche Elecsys nucleocapsid and spike). IgM antibodies were less frequently detected by one of the rapid test cassette assays. CONCLUSIONS : Serum, plasma, and heparinized-plasma constitute reliable samples for SARS-CoV-2 antibody detection. In particular, the IgG response was stable and reliably detected after multiple FTCs and storage at common laboratory conditions. IgM detection was variable due to the labile nature of this antibody class.

Is there an immunological cross-reactivity of antibodies to the myelin oligodendrocyte glycoprotein and coronaviruses?

“…This finding might be caused either by increased MOG-IgM having initially resulted in falsely positive MOG-IgG titres in assays using H + L-specific rather than Fc(gamma)-specific detection antibodies, 28 , 41 by isolated CSF MOG-IgG but negative serum MOG-IgG positivity, 43 , 44 by immunosuppressive treatments, 6 , 23 the timing of sample collection in regard to the neurological presentation 45 , 46 or by the degradation of antibodies due to repeated freeze-thaw cycles. 47 , 48 This is important because the purification of antigen-specific antibodies is dependent on antibody titre and consequently was less efficient in samples with lower antibody levels to MOG or SARS-CoV-2 S and N proteins. However, only few (15%) of the included patients were on suppressive treatment at sampling with comparable frequencies in all groups ( Table 1 ) and most samples (71%) were obtained within 3 months after the neurological event.…”

Preserved SARS-CoV-2 neutralizing IgG activity of in-house manufactured COVID-19 convalescent plasma

“…Several studies investigated antibody activity or titer after freeze-thaw cycles, and most of the results described that antibody activity or titer were preserved after the freeze-thaw process [10] , [15] . Plasma antibodies against SARS-CoV-2 collected from convalescent participants were also evaluated after the freeze-thaw cycle, and the activities did not change significantly [16] . However, to the best of our knowledge, there are no studies evaluating convalescent plasma products manufactured for clinical usage.…”

Evolution of anti-SARS-CoV-2 spike protein titers after two-dose of COVID-19 vaccination among people living with HIV

“…In addition, the storage of the serum sample at −20 °C before testing might also contribute the lower antibody responses observed in our study, although previous studies have demonstrated that multiple freeze--thaw cycles had no effect on the ability of the ELISA assay to detect SARS-CoV-2 IgG antibodies. 25 , 26 …”