IDENTIFICATION OF A VACCINIA VIRUS PENETRATION PROTEIN

A vaccinia virus structural protein responsible for infection was iden tified by monoclonal antibodies (mAb). Two mAbs (2D5 and 8C2) neutrali zed the virus at a dilution of about 10(5). The 2D5 mAb reacted with V P29K under standard immunoblotting conditions and with a 23-kDa protei n when virus was dissociated under nonreducing conditions. The 8C2 mAb reacted with the 23-kDa protein, but not with VP29K. Two-dimensional electrophoresis demonstrated that the 23-kDa protein was the nonreduce d form of VP29K. Since they possess the same N-terminal amino acid seq uence, the protein was renamed VP23-29K. The gene that encoded it was HindIII A17L ORF. The VP23-29K-dependent process of infection did not occur during the adsorption phase at 4 degrees, and trypsin-treated vi rus could complete the process within 10 min at 37 degrees. One half o f the trypsin-treated intracellular mature virus (IMV) achieved the pr ocess within 20 min, but for normal IMV this time period was 2 hr. VP2 3-29K had function for the early step of penetration, and the function al site in the nonreduced 23-kDa form was masked to some extent in nor mal virus. The late cell fusion by the fusion positive (F+) D1 mutant proceeded in neutral pH. Cells infected with F- IHD-J strain Virus did not fuse, but a short treatment with pH 5 medium developed cell fusio n. Both of the cell fusions were inhibited by the 2D5 and 8C2 mAbs. Vi rion VP23-29K was suggested to be the fusion protein for the early pen etration and the late cell fusion phases of vaccinia infection cycle. (C) 1994 Academic Press, Inc.