Interference of coronavirus infection by expression of IgG or IgA virus neutralizing antibodies

Abstract

Mouse immunoglobulin gene fragments encoding the variable modules of the heavy (VH) and light (VL) chains of a transmissible gastroenteritis coronavirus (TGEV) neutralizing monoclonal antibody (MAb) have been cloned and sequenced. The selected MAb recognizes a highly conserved viral epitope and does not lead to the selection of neutralization escape mutants. Chimeric immunoglobulin genes with the variable modules from the murine MAb and constant modules of human gamma I and kappa chains were constructed using RT- PCR. These chimeric immunoglobulins were stably or transiently expressed in murine myelomas and COS cells, respectively. The secreted recombinant antibodies had radioimmunoassay (RIA) titers higher than 103 and reduced the infectious virus more than 104-fold. Recombinant dimeric IgA showed a 50- fold enhanced neutralization of TGEV relative to a recombinant monomeric IgG1 which contained the identical antigen binding site. Epithelial cell lines stably-transformed with these constructs and expressing either recombinant IgG or IgA TGEV neutralizing antibodies reduced virus production by >105- fold after infection with homologous virus, although a residual level of virus production (<102 PFU/ml) remained in less than 0.1 % of the cells.