SMPD2 and infection: To further validate this, BSR cells were treated with 10μM of GW4869, a potent exosome inhibitor at 1h post-infection, which showed no cytotoxic effect in an MTT assay (Fig 6C), was capable to inhibit neutral sphingomyelinase-2 (SMPD2), the enzyme that plays a crucial role in exosome formation [23] (Fig 6D).