LCMV binding affinity to α-DG. Virus overlay protein binding assay (VOPBA) was done with purified α-DG and LCMV variants and strains as described by Sevilla et al. (2000). Decreasing amounts of purified α-DG were loaded on an SDS-PAGE, electrophoresed, and transferred onto nitrocellulose. The nitrocellulose was incubated with 107 PFUs of each viral isolate, and viral proteins were detected with monoclonal antibodies specific for LCMV GP. The top panel shows the VOPBA of immunosuppressive LCMV strains (Traub and WE 54) and variants (Cl 13, PBL 67–3, PBL 36–4, and TNPBL 4–2); the bottom panel shows the VOPBA of nonimmunosuppressive LCMV strains (ARM 53b and E-350) and variants (WE 2.2, CD8–4, CD4–1, and TNB 2–1)