Neutralizing antibody responses to SARS-CoV-2 in COVID-19 patients

Abstract

Background & objectives: The global pandemic caused by SARS-CoV-2 virus has challenged public health system worldwide due to the unavailability of approved preventive and therapeutic options. Identification of neutralizing antibodies (NAb) and understanding their role is important. However, the data on kinetics of NAb response among COVID-19 patients are unclear. To understand the NAb response in COVID-19 patients, we compared the findings of microneutralization test (MNT) and plaque reduction neutralization test (PRNT) for the SARS-CoV-2. Further, the kinetics of NAb response among COVID-19 patients was assessed. Methods: A total of 343 blood samples (89 positive, 58 negative for SARS-CoV-2 and 17 cross-reactive and 179 serum from healthy individuals) were collected and tested by MNT and PRNT. SARS-CoV-2 virus was prepared by propagating the virus in Vero CCL-81 cells. The intra-class correlation was calculated to assess the correlation between MNT and PRNT. The neutralizing endpoint as the reduction in the number of plaque count by 90 per cent (PRNT 90 ) was also calculated. Results: The analysis of MNT and PRNT quantitative results indicated that the intra-class correlation was 0.520. Of the 89 confirmed COVID-19 patients, 64 (71.9%) showed NAb response. Interpretation & conclusions: The results of MNT and PRNT were specific with no cross-reactivity. In the early stages of infection, the NAb response was observed with variable antibody kinetics. The neutralization assays can be used for titration of NAb in recovered/vaccinated or infected COVID-19 patients.

Evaluation of Safety and Immunogenicity of an Adjuvanted, TH-1 Skewed, Whole Virion InactivatedSARS-CoV-2 Vaccine - BBV152

“…The virus–serum mixtures were added onto the preformed Vero CCL-81 cell monolayers and incubated 1 h at 37°C in a 5% CO 2 incubator. The number of plaques was counted, and the Neutralizing antibody titer was determined based on the 90% reduction in the number of plaque count, which was further analyzed using 50% ProbitAnalysis 38 . A neutralization antibody titer < 1:20 considered negative, while that of > 1:20 considered as positive.…”

Neutralization of UK-variant VUI-202012/01 with COVAXIN vaccinated human serum

“…The sero-conversion rate with neutralizing antibodies (NAb) following vaccination with BBV152 was 99.6%. 5 Here, we present the NAb titers (PRNT 50 ) to underline the efficacy of BBV152 vaccine candidate against SARS-CoV-2 UK-variant and one of the heterologous strains hCoV-19/India/2020Q111 (unclassified cluster) 6 . Sera collected from 38 vaccine recipients, who received BBV152 vaccine-candidate in phase-II trial4 had equivalent NAb titers to hCoV-19/India/2020770 homologous strain and two heterologous strains with the characteristic N501Y substitution of the UK-variant; hCoV-19/India/20203522 (UK strain) as well as hCoV-19/India/2020Q111 (Figure 1 A and B).…”

Development of equine antisera with high neutralizing activity against SARS-CoV-2

“…Plaque reduction neutralization test (PRNT): PRNT was performed as described by Deshpande et al, (2020) 17 . Brie y, four-fold serial dilutions of heat inactivated (56°C for 1 h) horse plasma samples were mixed with an equal amount of virus suspension containing 50-60 plaque forming units (pfu) in 0.1 ml.…”