Antibody and T cell memory immune response after two doses of the BNT162b2 mRNA vaccine in older adults with and without prior SARS-CoV-2 infection (preprint)

We quantified S1-specific IgG, neutralizing antibody titers, specific IFN{gamma} secreting T cells and functionality of specific CD4+ and CD8+ T cells in 130 young adults (median age 44.0 years) and 106 older residents living in a long-term care facility (86.5 years) after 2 doses of BNT162b2. Three months after the first injection, humoral and cellular memory responses were dramatically impaired in the 54 COVID-19-naive older compared to the 121 COVID 19 naive younger adults. Notably, older participants' neutralizing antibodies, detected in 76.5% (versus 100% in young adults, P < 0.0001), were ten times lower than the younger's antibody titers (P < 0.0001). Antibody and T cell responses were greater among the 52 COVID 19-recovered than among the 54 COVID-19-naive older adults (P < 0.0001). Our study shows that 2 doses of BNT162b2 does not guarantee long-term protection against SARS-CoV-2 in the older. An additional dose should be considered to boost their specific memory response.

Large scale screening discovers clofoctol as an inhibitor of SARS-CoV-2 replication that reduces COVID-19-like pathology (preprint)

The fastest way to implement a treatment against a new rapidly emerging viral disease consists in screening the potential antiviral activity of drugs approved for human use. This has the advantage of shortening regulatory preclinical development steps. Here, we screened a library of drug compounds, already registered in one or several geographical areas, to identify those exhibiting antiviral activity against SARS-CoV-2 with relevant potency. Of the 1,942 compounds tested, 21 exhibited a substantial antiviral activity in Vero-81 cells. Among them, clofoctol, an antibacterial drug used for the treatment of bacterial respiratory tract infections, was further investigated due to its favorable safety profile and its pharmacokinetic properties. Notably, the peak concentration of clofoctol that can be achieved in human lungs is more than 20 times higher than its IC95 measured against SARS-CoV-2 in human pulmonary cells. Mechanistically, this compound inhibits SARS-CoV-2 at a post-entry step by specifically blocking translation initiation of viral RNA. Lastly, therapeutic treatment of human ACE2 receptor transgenic mice decreased viral load, reduced inflammatory gene expression and improved pulmonary pathology. Altogether, these data strongly support clofoctol as a therapeutic candidate for the treatment of COVID-19 patients.