We observed similar results in infection assays performed with both CXCR4-tropic (IIIB) and CCR5-tropic (BaL) HIV-1 isolates, with the all-β, alternatively-folded conformation (W55D) conferring inhibition, and the chemokine-folded conformation (CC3) showing minimal, if any, activity (Figure S1). Here, CXCR4 is linked to infection.