Figure 1. Western blot assays using human serum. Dilutions of human serum (lanes 2–11) or a foamy virus–-positive Macaca mulatta MBG8 (lane 1) were used to probe filter strips containing equal amounts of lysates from simian foamy virus–infected cells (from M. fascicularis; i lanes) or noninfected cells (u lanes). Individual strips were developed by using TMB reagent (3,3′,5,5′-tetramethylbenzidine; Promega, Madison, WI, USA). The positions of the viral proteins Gag and Bet are indicated. Lanes 10 and 11 show the range of reactivity seen with negative serum; lane 10 shows serum with nonspecific reactivity to proteins of approximately the same size as viral proteins; lane 11 shows serum negative for both lysates.