Changes in SARS-CoV-2 Antibody Responses Impact the Estimates of Infections in Population-Based Seroprevalence Studies

Abstract

We have determined SARS-CoV-2-specific antibody responses in a cohort of 96 individuals with acute infection and in 578 individuals enrolled in a seroprevalence population study in Switzerland including three groups, i.e. subjects with previous RT-PCR confirmed SARS-CoV-2 infections (n=90), positive patient contacts (n=177) and random selected subjects (n=311). SARS-CoV-2 antibody responses specific to the Spike (S), in the monomeric and native trimeric forms, and/or the nucleocapsid (N) proteins were equally sensitive in the acute infection phase. Interestingly, as compared to anti-S antibody responses, those against the N protein appear to wane in the post-infection and substantially underestimated the proportion of SARS-CoV-2 infections in the groups of patient positive contacts, i.e. 10.9 to 32.2% reduction and in the random selected general population, i.e. up to 45% reduction. The overall reduction in seroprevalence targeting only anti-N IgG antibodies for the total cohort ranged from 9.4 to 31%. Of note, the use of the S protein in its native trimer form was more sensitive as compared to monomeric S proteins. These results indicate that the assessment of anti-S IgG antibody responses against the native trimeric S protein should be implemented to estimate SARS-CoV-2 infections in population-based seroprevalence studies.

High prevalence of SARS-CoV-2 antibodies in pets from COVID-19+ households

“…A recent Swiss study found that anti-N antibody assays substantially underestimate (i.e., by 30% to 45%) the proportion of SARS-CoV-2 exposed humans compared to anti-S antibody assays in population-based seroprevalence studies [ 15 ]. Assuming similar dynamics in pets, the actual seropositivity in COVID-19+ households is likely closer to 53% than 21%, indicating that infection risk in the pets of COVID-19 positive owners is much higher than previously described.…”

High prevalence of SARS-CoV-2 antibodies in pets from COVID-19+ households

“…The highly variable antibody responses to SARS-CoV-2 in human infections 13,14 A recent Swiss study found that anti-N antibody assays substantially underestimate (i.e., by 30% to 45%) the proportion of SARS-CoV-2 exposed individuals compared to anti-S antibody assays in population-based seroprevalence studies 15 . Assuming similar dynamics in pets, the actual seropositivity in COVID-19+ households is likely closer to 53% than 21%, indicating that infection risk in the pets of COVID-19 positive owners is much higher than previously described.…”

Stepwise anti-inflammatory and anti-SARS-CoV-2 effects following convalescent plasma therapy with full clinical recovery

“…Preparation of the Luminex beads coupled with the S protein trimer was performed as described in 16 . S protein-coupled Luminex beads were added to Bio-Plex Pro 96-well at bottom plates, washed with PBS, before adding 50 l of a 1/300 dilution of individual serum (from the patient) or plasma (from the donors) to the wells 16 . Plates were agitated at 500 rpm for 60 minutes on a plate shaker.…”

“…Beads were resuspended in 80 l of reading buffer and read directly on a Luminex FLEXMAP 3D plate reader (ThermoFisher). MFI signal of each test serum or plasma sample was divided by the mean signal for the negative control samples yielding a MFI ratio 16 .…”