Identification of human infection with simian foamy virus (SFV) in the Democratic Republic of Congo. Detection of plasma antibodies to SFV from chimp (SFVcpz) and monkey (SFVagm) using a combined antigen Western blot assay. Upper panel shows reactivity to the combined antigen, lower panel shows reactivity to crude cell lysate antigens from uninfected canine thymocytes (Cf2Th). Seroreactivity was defined as those specimens with reactivity specific to the diagnostic Gag doublet proteins in the combined viral antigens. Lanes 1 and 2 show positive plasma controls from an SFV-infected chimpanzee and monkey, respectively. Lane 3 is a pedigreed negative human plasma control. Study participant plasma samples that were also PCR-positive are marked with an asterisk.