Rapid Generation of In-House Serological Assays Is Comparable to Commercial Kits Critical for Early Response to Pandemics: A Case With SARS-CoV-2

Abstract

IntroductionAccurate and sensitive measurement of antibodies is critical to assess the prevalence of infection, especially asymptomatic infection, and to analyze the immune response to vaccination during outbreaks and pandemics. A broad variety of commercial and in-house serological assays are available to cater to different laboratory requirements; however direct comparison is necessary to understand utility.Materials and MethodsWe investigate the performance of six serological methods against SARS-CoV-2 to determine the antibody profile of 250 serum samples, including 234 RT-PCR-confirmed SARS-CoV-2 cases, the majority with asymptomatic presentation (87.2%) at 1–51 days post laboratory diagnosis. First, we compare to the performance of two in-house antibody assays: (i) an in-house IgG ELISA, utilizing UV-inactivated virus, and (ii) a live-virus neutralization assay (PRNT) using the same Cambodian isolate as the ELISA. In-house assays are then compared to standardized commercial anti-SARS-CoV-2 electrochemiluminescence immunoassays (Elecsys ECLIAs, Roche Diagnostics; targeting anti-N and anti-S antibodies) along with a flow cytometry based assay (FACS) that measures IgM and IgG against spike (S) protein and a multiplex microsphere-based immunoassay (MIA) determining the antibodies against various spike and nucleoprotein (N) antigens of SARS-CoV-2 and other coronaviruses (SARS-CoV-1, MERS-CoV, hCoVs 229E, NL63, HKU1).ResultsOverall, specificity of assays was 100%, except for the anti-S IgM flow cytometry based assay (96.2%), and the in-house IgG ELISA (94.2%). Sensitivity ranged from 97.3% for the anti-S ECLIA down to 76.3% for the anti-S IgG flow cytometry based assay. PRNT and in-house IgG ELISA performed similarly well when compared to the commercial ECLIA: sensitivity of ELISA and PRNT was 94.7 and 91.1%, respectively, compared to S- and N-targeting ECLIA with 97.3 and 96.8%, respectively. The MIA revealed cross-reactivity of antibodies from SARS-CoV-2-infected patients to the nucleocapsid of SARS-CoV-1, and the spike S1 domain of HKU1.ConclusionIn-house serological assays, especially ELISA and PRNT, perform similarly to commercial assays, a critical factor in pandemic response. Selection of suitable immunoassays should be made based on available resources and diagnostic needs.

Utility of Roche Elecsys anti-SARS-CoV-2 S in ascertaining post-vaccine neutralizing antibodies

“…There is more diversity, however, of reported outcomes with regards to the strength of this correlation than there is with sensitivity and specificity. Wilkins et al [12] , Jochum et al [23] , Auerswald et al [25] , and Takei et al [31] report relatively high correlation coefficients (Spearman's / Pearson’ r in the range of 0.7 – 0.85), while Einhauser et al [14] have reported moderate correlation (0.53) between the two assays. Rus et al [24] reported a Cohen's Kappa of 0.56.…”

“…Several other studies [12] , [13] , [14] , [15] , [16] , [17] , [18] , [19] , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] have also ascertained clinical sensitivity of the assay after exposure to the SARS-CoV-2 virus or vaccine or both, and specificity through evaluation of pre-pandemic specimens. Sensitivities have been reported at time intervals varying from 14 days to 240 days post-exposure.…”

Potential use of endemic human coronaviruses to stimulate immunity against pathogenic SARS-CoV-2 and its variants

“…There is also strong evidence that in the areas of the globe with low income and high population density, where there is a high probability of eCOVID exposure, the mortality and morbidity from SARS-CoV-2 have been low (discussed in a later section; Tables 4–6 ). Our understanding of the cross-immunity induced by eCOVID infection is limited and the only evidence is that children are significantly less susceptible to SARS-CoV-2 and in low-income, high-density regions of the world where continuous exposure to eCOVIDs is evident, the serious incidence of SARS-CoV-2 associated hospitalization and death are significantly low [ 22–27 ]. Several recent studies have shown that a considerable proportion of individuals without a history of SARS-CoV-2 infection possess antibodies to SARS-CoV-2 and SARS-CoV-2-reactive T cells, indicating that cross-reactive T cell subsets originating from past infections by eCOVID may play a role in the clinical outcome of infection with the phylogenetically related eCOVID [ 3–8 ].…”