PROKARYOTIC EXPRESSION OF AN IMMEDIATE-EARLY GENE OF HUMAN HERPESVIRUS-6 AND ANALYSIS OF ITS VIRAL-ANTIGEN EXPRESSION IN HUMAN-CELLS

Segments of an immediate-early (IE) protein (1E03; 958 amino acids (aa )), encoded by done pSTY03, of human herpesvirus 6 (HHV-6) variant B s train HST were expressed as beta-galactosidase fusion proteins in Esch erichia coli. Using Western blot analysis, and the serum of a patient having high titer anti-HHV-6 antibodies, an antigenic region of the IE 03 protein was mapped between residues 340 and 505 (pUE03IE-M). The fu sion protein expressed in E. coli harboring plasmid pUE03IE-M was puri fied after electrophoresis in SDS-PAGE, and then immunized in mice to obtain a monospecific antibody. Monospecific antibody raised against t he fusion protein reacted with IE03 protein species with apparent mole cular weights of 155 and 170 kDa, and was detected as granular fluores cence in nuclei of infected cells by an immunofluorescence antibody te st. Furthermore, this antibody reacted only with HHV-6 variant B, but did not react with HHV-6 variant A. The IE03 protein was confirmed to be an IE protein, since the synthesis of this protein was observed in infected cells that were first treated with cycloheximide, which was t hen replaced with actinomycin D. Further, it was also detected as earl y as 4 h after infection.