Identification of SARS-CoV-2 Neutralizing Potency of Human Convalescent
Plasma Using Pseudovirus Neutralization Assay
Abstract
Convalescent plasma samples that can be collected from individuals after
the resolution of infection and vaccination are an invaluable source of
neutralization antibodies against the virus. Although plaque reduction
assay with replicative virus is the gold standard of analyzing
neutralization potency of convalescent plasma, it is a technically
demanding procedure requiring high biosafety level (BSL-3/4) laboratory
and equipment. The abundance of neutralizing antibodies varies among
individuals, therefore fast and reliable methods to identify
neutralization potency of plasma samples are needed. In this paper,
G-protein deficient vesicular stomatitis virus (VSV-ΔG) carrying a
C-terminal 21 amino acid truncated severe acute respiratory syndrome
coronavirus 2 (SARS-CoV-2) Spike protein was generated for pseudovirus
neutralization assay. We analyzed SARS-CoV-2 neutralizing potency of
vaccinated human convalescent plasma samples (n=13) and plasma samples
of healthy people (n=2). Human convalescent plasma samples were examined
against the ancestral Wuhan strain and two SARS-CoV-2 variants (B.1.1.7,
and B.1.351) using a VSV-ΔG-Sdel21 pseudovirus and Vero E6 cell line.
Neutralization values against pseudotyped virus were compared to those
of plaque reduction assay against authentic virus. The serum
neutralizing titer of convalescent plasma measured by pseudovirus assay
has a good correlation with that measured by plaque reduction assay (R
2= 0.7). The pseudovirus assay is safer and timesaving
than the replicative virus-based plaque reduction assay, and has several
advantages in evaluating a new vaccine, newly emergent variants, and
approved vaccine efficacy against variants of concern as well as in
viral fusion-focused treatment analysis that can be performed under
BSL-2 conditions.