FIG. 2.

Antibody cross-reactivity between YLD virus and VV. The top bar graph demonstrates the presence of anti-VV antibodies in serum from a patient recently immunized against VV (+Serum). The serum reacts against VV-coated ELISA plates at a dilution of 1:3,000, whereas no reaction is seen against fowlpox (FP)- or YLD virus-coated ELISA plates. The negative serum (-Serum) represents the serum of a patient not previously immunized with VV. Three other patients who were immunized with VV showed similar results, with reactivity only against VV-coated ELISA plates but not YLD virus-coated plates. The bottom graph demonstrates the development of IgG against VV and YLD virus after immunizing mice with VV or YLD virus (n = 5/group). The antibody titers increased significantly over the first 3 weeks and then leveled off. There was no demonstrable cross-reactivity against VV or YLD virus in these animals.