S100B and infection: Similarly, F2 inhibited infection of primary human peripheral blood mononuclear cells (PBMCs) by a replication-competent HIV-1 vector (NL4-3 Nef + IRES rluc) with a measured EC50 of 0.865 ± 0.222 μM (Figure 1D) in the absence of cell toxicity, up to 10μM of compound tested (data not shown, selectivity index > 11.6).