Immunostained viral plaques of recombinant viruses derived by the BAC allele replacement technique. Virus was isolated following transfection of Vero cells with recombinant HSV2-BACs expressing A33R or B5R, titered and used to infect plates of Vero cells. Monolayers were fixed and then probed with mouse anti-HA monoclonal antibody, followed by AP-conjugated goat anti-mouse antibody. (A) B5R-expressing HSV2-BAC virus infected cells. (B) A33R-expressing HSV2-BAC virus infected cells.