Reactivity of expressed gD with monkey sera in WB analysis. The extracts from COS7 cells transfected with pBgD (A) or pcDNA3.1(−) (B) were examined for reactivity with sera obtained from monkeys. Sera from monkeys regarded as B virus infected (no. 37, 41, 42, 46, 49, 82, 83, and 84) and noninfected (no. 991,992, 993, 994, and 995) were used. Anti-gD(SA8) serum was also included. The position of gD (arrow) and molecular mass standards (in kilodaltons) are indicated on the left.