Increased antibody affinity confers broad in vitro protection against escape mutants of severe acute respiratory syndrome coronavirus.
Even though the effect of antibody affinity on neutralization potency is well documented, surprisingly, its impact on neutralization breadth and escape has not been systematically determined. Here, random mutagenesis and DNA shuffling of the single-chain variable fragment of the neutralizing antibody 80R followed by bacterial display screening using anchored periplasmic expression (APEx) were used to generate a number of higher-affinity variants of the severe acute respiratory syndrome coronavirus (SARS-CoV)-neutralizing antibody 80R with equilibrium dissociation constants (K(D)) as low as 37 pM, a >270-fold improvement relative to that of the parental 80R single-chain variable fragment (scFv). As expected, antigen affinity was shown to correlate directly with neutralization potency toward the icUrbani strain of SARS-CoV. Additionally, the highest-affinity antibody fragment displayed 10-fold-increased broad neutralization in vitro and completely protected against several SARS-CoV strains containing substitutions associated with antibody escape. Importantly, higher affinity also led to the suppression of viral escape mutants in vitro. Escape from the highest-affinity variant required reduced selective pressure and multiple substitutions in the binding epitope. Collectively, these results support the hypothesis that engineered antibodies with picomolar dissociation constants for a neutralizing epitope can confer escape-resistant protection.
Institute of Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, USA.
Mridula
M
Rani
Meagan
M
Bolles
Eric F
EF
Donaldson
Thomas
T
Van Blarcom
Ralph
R
Baric
Brent
B
Iverson
George
G
Georgiou
D000595:Amino Acid Sequence; D000818:Animals; D057134:Antibodies, Neutralizing / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology; D000914:Antibodies, Viral / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology; D000915:Antibody Affinity; D002460:Cell Line; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D009500:Neutralization Tests; D045473:Severe acute respiratory syndrome-related coronavirus / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000276:immunology*; D016415:Sequence Alignment; D045169:Severe Acute Respiratory Syndrome / Q000276:immunology* / Q000517:prevention & control* / Q000821:virology; D057127:Single-Chain Antibodies / Q000235:genetics / Q000276:immunology / Q000494:pharmacology
D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D057127:Single-Chain Antibodies