TRANSGENIC MICE SECRETING CORONAVIRUS NEUTRALIZING ANTIBODIES INTO THE MILK

Ten lines of transgenic mice secreting transmissible gastroenteritis c oronavirus (TGEV) neutralizing recombinant monoclonal antibodies (rMAb s) into the milk were generated. The rMAb light-and heavy-chain genes were assembled by fusing the genes encoding the variable modules of th e murine MAb 6A.C3, which binds an interspecies conserved coronavirus epitope essential for virus infectivity, and a constant module from a porcine myeloma with the immunoglobulin A (IgA) isotype. The chimeric antibody led to dimer formation in the presence of J chain. The neutra lization specific activity of the recombinant antibody produced in tra nsiently or stably transformed cells was 50-fold higher than that of a monomeric rMAb with the IgG1 isotype and an identical binding site. T his rMAb had titers of up to 10(4) by radioimmunoassay (RIA) and neutr alized virus infectivity up to 10(4)-fold. Of 23 transgenic mice, 17 i ntegrated both light and heavy chains, and at least 10 of them transmi tted both genes to the progeny, leading to 100% of animals secreting f unctional TGEV neutralizing antibody during lactation. Selected mice p roduced milk with TGEV-specific antibody titers higher than 10(6) as d etermined by RIA, neutralized virus infectivity by 10(6)-fold, and pro duced up to 6 mg of antibody per ml. Antibody expression levels were t ransgene copy number independent and integration site dependent. Comic roinjection of the genomic beta-lactoglobulin gene with rMAb light and heavy-chain genes led to the generation of transgenic mice carrying t he three transgenes. The highest antibody titers mere produced by tran sgenic mice that had integrated the antibody and beta-lactoglobulin ge nes, although the number of transgenic animals generated does not allo w a definitive conclusion on the enhancing effect of beta-lactoglobuli n cointegration. This approach may lead to the generation of transgeni c animals providing lactogenic immunity to their progeny against enter ic pathogens.