Mouthwashes with CPC Reduce the Infectivity of SARS-CoV-2 Variants In Vitro.

Oral mouthwashes decrease the infectivity of several respiratory viruses including SARS-CoV-2. However, the precise agents with antiviral activity in these oral rinses and their exact mechanism of action remain unknown. Here we show that cetylpyridinium chloride (CPC), a quaternary ammonium compound in many oral mouthwashes, reduces SARS-CoV-2 infectivity by inhibiting the viral fusion step with target cells after disrupting the integrity of the viral envelope. We also found that CPC-containing mouth rinses decreased more than a thousand times the infectivity of SARS-CoV-2 in vitro, while the corresponding vehicles had no effect. This activity was effective for different SARS-CoV-2 variants, including the B.1.1.7 or Alpha variant originally identified in United Kingdom, and in the presence of sterilized saliva. CPC-containing mouth rinses could therefore represent a cost-effective measure to reduce SARS-CoV-2 infectivity in saliva, aiding to reduce viral transmission from infected individuals regardless of the variants they are infected with.

A subset of cytolytic dendritic cells in rat.

Dendritic cells (DCs) are a rare population of leukocytes specialized in Ag processing and presentation to T cells. We have previously shown that cultured rat splenic DCs exhibit a cytotoxic activity against selected target cells. In this study, we analyzed this function in DCs freshly prepared from lymphoid organs using the DC-specific OX62 mAb and magnetic beads. Freshly extracted splenic DCs, but not lymph node and thymic DCs, exhibited a strong and moderate cytotoxic activity against YAC-1 and K562 target cells, respectively. FACS analyses showed that spleen contained a minor subset (10-15%) of CD4(+) and class II(int) DCs that also expressed the OX41 Ag and the lymphoid-related Ags CD5 and CD90 (Thy-1) and a major (80-85%) subset of CD4(-)/OX41(-)/CD5(-) and class II(int) DCs. The cytotoxic activity of splenic DCs was strictly restricted to the CD4(-) DCs, a subset poorly represented in LN and thymus. Contrasting with our previous report using cultured splenic DCs, freshly isolated splenic DCs killed YAC-1 cells using a Ca(2+)-independent mechanism, but this function did not appear mediated by Fas ligand, TNF-related apoptosis-inducing ligand, or TNF-alpha. Therefore, rat DCs contain a subset of naturally cytolytic cells that could play a role in both innate and acquired immune responses. Together with our previous report, these data suggest that rat DCs can use two mechanisms of cytotoxicity depending on their maturation/activation state.