INHIBITION OF AFRICAN SWINE FEVER VIRUS BINDING AND INFECTIVITY BY PURIFIED RECOMBINANT VIRUS ATTACHMENT PROTEIN P12

The African swine fever virus protein p12, involved in virus attachmen t to the host cell, has an apparent molecular mass of 17 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing conditions. We have also identified 12- and 10-kDa forms of the p12 pr otein in infected Vero cells and found that the mature 17-kDa protein is the only form present in virus particles. The p12 protein has been produced in large amounts in Spodoptera frugiperda insect cells infect ed with a recombinant baculovirus. A 17-kDa protein that possessed the biological properties of the viral protein was produced, since it bou nd to susceptible Vero cells and not to receptor-negative L cells, whi ch do not support virus replication. The binding of the baculovirus-ex pressed protein pl2 to Vero cells was specifically blocked by virus pa rticles. In addition, the recombinant protein purified by immunoaffini ty chromatography blocked the specific binding of virus particles to s usceptible cells and prevented infection, demonstrating that the p12 p rotein mediates the attachment of virions to specific receptors and in dicating that blocking the p12-mediated interaction between African sw ine fever virus and receptors in Vero cells can inhibit infection. How ever, although antibodies specific for protein p12 are induced in natu ral infections and in animals inoculated with inactivated virus or rec ombinant protein p12, these antisera did not inhibit virus binding to the host cell or neutralize virus infectivity.