Major royal jelly proteins elicited suppression of SARS-CoV-2 entry and replication with halting lung injury.

For reasons of high transmissibility and virulence, Alpha (UK, B.1.1.7) and Beta (South African, B.1.351) SARS-CoV-2 variants are classified with other types as variants of concern. Here we report on the influence of royal jelly (RJ) protein fraction (PF)50 (major RJ protein 2 and its isoform X1) on the entry of these variants into the ACE2-human embryonic kidney (HEK) 293 cells using the lentiviral system. The efficiency of PF50 on SARS-CoV-2 replication (RNA-dependent RNA polymerase "RdRp" activity), as well as its impact on bleomycin-induced lung injury in vitro, were also assessed. The PF50 efficiently inhibited infection of kidney cells with the UK and S. African variant spikes of pseudotyped lentivirus particles (IC50 = 7.25 μM and 16.92 μM, respectively) and suppressed the RdRp activity (IC50 = 29.93 μM). Moreover, PF50 displayed protective and therapeutic efficacy against lung injury due to its antioxidant, anti-inflammatory, and angiotensin II blocking activities. The current findings, taken together, offer a novel perspective on PF50 as a promising agent against COVID-19.