S100B and infection: PS-mediated inhibition of infection of MDMs was analyzed with an R5 reporter virus that coexpresses Nef and EGFP from a bicistronic mRNA (R5 HIV-1NL4-3 IRES-eGFP [20]) and analyzing proportions of EGFP-positive cells by flow cytometry (EC50 = 8.27±2.75 μg/ml; n = 3).