Temporal development and neutralising potential of antibodies against SARS-CoV-2 in hospitalised COVID-19 patients: An observational cohort study

Abstract

Antibody responses are important in the control of viral respiratory infection in the human host. What is not clear for SARS-CoV-2 is how rapidly this response occurs, or when antibodies with protective capability evolve. Hence, defining the events of SARS-CoV-2 seroconversion and the time frame for the development of antibodies with protective potential may help to explain the different clinical presentations of COVID-19. Furthermore, accurate descriptions of seroconversion are needed to inform the best use of serological assays for diagnostic testing and serosurveillance studies. Here, we describe the humoral responses in a cohort of hospitalised COVID-19 patients (n = 19) shortly following the onset of symptoms. Commercial and ‘in-house’ serological assays were used to measure IgG antibodies against different SARS-CoV-2 structural antigens–Spike (S) S1 sub-unit and Nucleocapsid protein (NP)–and to assess the potential for virus neutralisation mediated specifically by inhibition of binding between the viral attachment protein (S protein) and cognate receptor (ACE-2). Antibody response kinetics varied amongst the cohort, with patients seroconverting within 1 week, between 1–2 weeks, or after 2 weeks, following symptom onset. Anti-NP IgG responses were generally detected earlier, but reached maximum levels slower, than anti-S1 IgG responses. The earliest IgG antibodies produced by all patients included those that recognised the S protein receptor-binding domain (RBD) and were capable of inhibiting binding to ACE-2. These data revealed events and patterns of SARS-CoV-2 seroconversion that may be important predictors of the outcome of infection and guide the delivery of clinical services in the COVID-19 response.

Whole blood-based measurement of SARS-CoV-2-specific T cell responses reveals asymptomatic infection and vaccine efficacy in healthy subjects and patients with solid organ cancers

“…After washing (x3), plates were developed using O-phenylenediamine dihydrochloride (OPD, SIGMAFASTTM; Sigma-Aldrich, # P9187-50SET) and the optical density (OD) measured at 492 nm. Assay validation, including intra-/inter-assay CVs for this assay have been previously described (17, 19).…”

“…An in-house direct ELISA was developed as previously described (16)(17)(18)(19), with some modifications. Maxisorp (Nunc, Loughborough, UK) 96-well plates were coated with RBD protein (recombinantly generated in a mammalian expression system, in house) at 2 µg/ml in bicarbonate buffer, pH 9.6 at 4°C overnight; wells were blocked for 1 hour at room temperature with 3% w/v non-fat dried milk powder (Sigma Aldrich, # 70166-500G) in phosphate-buffered saline containing 0.1% Tween 20 (PBS-T), washed in PBS-T. Dilutions of patient sera (1 in 50 in 1% Milk PBS-T), were added in duplicate to wells coated with RBD protein and incubated for 2 hours at room temperature.…”

A Reliable Indirect ELISA Protocol for Detection of Human Antibodies Directed to SARS-CoV-2 NP Protein

“…However, there is lack of positive correlation between OD 450 values obtained from these ELISAs ( Figure 4 C,D). The level of antibodies to different viral antigens does not necessary correlate [ 37 , 38 ]. Thus, the lack of correlation between results obtained from NP- and S-based ELISAs might reflect differences in the expression level of the corresponding antibodies.…”

Temporal Associations of the SARS-CoV-2 NP Antigen and Anti-Spike Total Ig Levels with Laboratory Parameters in a Greek Cohort of Hospitalized COVID-19 Patients

“…Despite these constraints, in this study, we performed repeated measurements of SARS-CoV-2 and host-related variables, thus providing insight into viral/host temporal dynamics in relation to the severity of COVID-19. Comprehensive information on virus and host kinetics during hospitalization and knowledge of SARS-CoV-2 seroconversion patterns [ 33 ] are important for the evaluation of therapy effectiveness and for clinical outcome improvement.…”