Combination treatment of unfractionated heparin and 800C produces no additive effects. Cells were infected with SH1000 for 60 min at an MOI = 50. (A) WT or CD9−/− A549 cells were treated with UFH, 800C peptide, or a combination of both for 60 min prior to treatment. (B) WT or CD9-/- A549 cells were treated with peptide (200 nM) for 60 mins prior to infection. UFH (10 U/ml), either in combination with 800C peptide or as a singular treatment, was added at the start of infection. (D) WT or CD9−/− cells were treated with fondaparinux (10 µg/mL), 800C peptide (200 nM), or a combination of both 60 min prior to infection. (E) WT cells treated with 800C peptide (200 nM), UFH (10 U/mL), or a combination of the two and infected with either SH1000 or SH1000 Δfnb at an MOI = 50. (F) NTKs treated with 800C peptide (200 nM), UFH (10 I.U./mL) or a combination of the two and infected with SH1000 for 60 min at an MOI = 50. n ≥ 3, mean ± SEM, and one-way ANOVA.