Serological surveys in Reunion Island of the first hospitalized patients revealed that long-lived immunoglobulin G antibodies specific against SARS-CoV2 virus are rapidly vanishing in severe cases

Abstract

Both cellular and humoral immunities are critically important to control COVID19 infection but little is known about the kinetics of those responses and, in particular, in patients who will go on to develop a severe form of the disease over several weeks. We herein report the first set of data of our prospective cohort study of 90 hospitalized cases. Serological surveys were thoroughly performed over 2 month period by assessing IgG and IgM responses by immunofluorescence, immunoblot, Western blot and conventional ELISA using clinical RUN isolates of SARS-CoV-2 immobilized on 96 well plates. While the IgM and, unexpectedly, the IgG responses were readily detected early during the course of the disease (5-7 days post-first symptoms), our results (n=3-5 and over the full dilution set of the plasma 1/200 to 1/12800) demonstrated a significant decrease (over 2.5-fold) of IgG levels in severe (ICU) hospitalized patients (exemplified in patient 1) by WB and ELISA. In contrast, mild non-ICU patients had a steady and yet robust rise in their specific IgG levels against the virus. Interestingly, both responses (IgM and IgG) were initially against the nucleocapsid (50kDa band on the WB) and spreading to other major viral protein S and domains (S1 and S2. In conclusion, serological testing may be helpful for the diagnosis of patients with negative RT-PCR results and for the identification of asymptomatic cases. Moreover, medical care and protections should be maintained particularly for recovered patients (severe cases) who may remain at risk of relapsing or reinfection. Experiments to ascertain T cell responses but although their kinetics overtime are now highly warranted. All in all, these studies will help to delineate the best routes for vaccination.

Antibody response to SARS-CoV-2 infection in humans: A systematic review

“…• One study reports lower seroconversion rate amongst asymptomatic compared to symptomatic cases [73]. • Two other studies on this association were limited by lack of detail on methodology and participant selection [74,75].…”

SARS-CoV-2 Prevalence and Seroprevalence among Healthcare Workers in Belgian Hospitals: Baseline Results of a Prospective Cohort Study

“…Also, two of the selected hospitals entered the cohort in May and were not included in these baseline results, reducing the statistical power of the study. Recent evidence 26,27 suggest that antibodies tend to wane in the early convalescent phase (8 weeks after infection), which means that HCW infected in the beginning of the epidemic might not have been detected. This could explain why in four participants who reported a previous positive PCR, no antibodies were detected.…”

Deciphering SARS-CoV-2 Virologic and Immunologic Features

“…In severe cases, a strong acute humoral response level has been reported [ 185 ] with increased proportion of plasmablasts in COVID-19 patients [ 153 ]. Nevertheless, a rapid decrease of the SARS-CoV-2 specific antibodies titers has been demonstrated in severe cases [ 186 , 187 , 188 ]. Variation of antibody response kinetic with disease severity [ 188 , 189 ], anti-N and anti-S antibodies antigen specificity [ 187 , 189 ], cytokine environment variation or major lymphopenia with disease severity [ 190 ] has been described.…”