ABSTRACT
Since the first report on November 24, 2021, the Omicron SARS-CoV-2 variant is now overwhelmingly spreading across the world. Two SARS-CoV-2 inactivated vaccines (IAVs), one recombinant protein subunit vaccine (PRV), and one adenovirus-vectored vaccine (AdV) have been widely administrated in many countries including China to pursue herd immunity. Here we investigated cross-neutralizing activities in 341 human serum specimens elicited by full-course vaccinations with IAV, PRV and AdV, and by various vaccine boosters following prime IAV and AdV vaccinations. We found that all types of vaccines induced significantly lower neutralizing antibody titers against the Omicron variant than against the prototype strain. For prime vaccinations with IAV and AdV, heterologous boosters with AdV and PRV, respectively, elevated serum Omicron-neutralizing activities to the highest degrees. In a mouse model, we further demonstrated that among a series of variant-derived RBD-encoding mRNA vaccine boosters, it is only the Omicron booster that significantly enhanced Omicron neutralizing antibody titers compared with the prototype booster following a prime immunization with a prototype S-encoding mRNA vaccine candidate. In summary, our systematical investigations of various vaccine boosters inform potential booster administrations in the future to combat the Omicron variant.
ABSTRACT
BackgroundA safe and effective coronavirus disease 2019 (COVID-19) vaccine is urgently needed to control the ongoing pandemic. Although progress has been made recently with several candidates reporting positive efficacy results, COVID-19 vaccines developed so far cannot meet the global vaccine demand. We developed a protein subunit vaccine against COVID-19, using dimeric form of receptor-binding domain (RBD) as the antigen. We aimed to assess the safety and immunogenicity of this vaccine in humans and determine the appropriate dose and schedule for an efficacy study. MethodsWe did two randomized, double-blind, placebo-controlled, phase 1 and 2 trials for an RBD-based protein subunit vaccine, ZF2001. In phase 1 study, 50 healthy adults aged 18-59 years were enrolled and randomly allocated to three groups to receive three doses of vaccine (25 g or 50 g RBD-dimer, with adjuvant) or placebo (adjuvant-only) intramuscularly, 30 days apart. In phase 2 study, 900 healthy adults aged 18-59 years were enrolled and randomly allocated to six groups to receive vaccine (25 g or 50 g RBD-dimer, with adjuvant) or placebo (adjuvant-only) intramuscularly, with the former 3 groups given two doses and the latter 3 groups given three doses, 30 days apart. For phase 1 trial, the primary outcome was safety, as measured by the occurrence of adverse events and serious adverse events. The secondary outcome was immunogenicity as measured by the seroconversion rate and magnitude of antigen-binding antibodies, neutralizing antibodies and T-cell cytokine production. For phase 2 trial, the primary outcome included both safety and immunogenicity. These trials are registered with ClinicaTrials.gov, NCT04445194 and NCT04466085. FindingsBetween June 22 and September 15, 2020, 50 participants were enrolled to the phase 1 study (mean age 32.6 years) and 900 participants were enrolled to phase 2 study (mean age 43.5 years), to receive vaccine or placebo with a two-dose or three-dose schedule. For both trials, local and systemic adverse reactions were absent or mild in most participants. There were no serious adverse events related to vaccine in either trial. After three doses, neutralizing antibodies were detected in all participants receiving either 25 g or 50 g dose of vaccine in phase 1 study, and in 97% (the 25 g group) and 93% (the 50 g group) of participants, respectively, in phase 2 study. The SARS-CoV-2-neutralizing geometric mean titres (GMTs) were 94.5 for the 25 g group and 117.8 for the 50 g group in phase 1, and 102.5 for the 25 g group and 69.1 for the 50 g group in phase 2, exceeding the level of a panel of COVID-19 convalescent samples (GMT, 51). Vaccine induced balanced TH1 and TH2 responses. The 50 g group did not show enhanced immunogenicity compared with the 25 g group. InterpretationThe protein subunit vaccine ZF2001 is well-tolerated and immunogenic. The safety and immunogenicity data from phase 1 and 2 trials for ZF2001 support the use of 25 g vaccine dose with three-dose schedule to an ongoing phase 3 large-scale evaluation for safety and efficacy. FundingNational Program on Key Research Project of China, National Science and Technology Major Projects of Drug Discovery, Strategic Priority Research Program of the Chinese Academy of Sciences, and Anhui Zhifei Longcom Biopharmaceutical.
ABSTRACT
Aim To observe the influences of dexmen-detomidine on the spontaneous contraction of duodenal smooth muscle of rabbits in vitro and explore the mech-anisms.Methods The rabbits ( male or female ) were stunned and the duodenums were isolated .The sam-ples of duodenal segments were connected with tension transducer , which were then put into oxygen saturation Krebs-Henseleit ( K-H) solution .The influences of dex-mendetomidine on amplitude ( AM ) and frequency ( FR ) of duodenal smooth muscle were recorded by BL-420 F biological signal processing system .The cu-mulative dosing method was used to observe the differ-ent concentrations of dexmedetomidine on duodenal smooth muscle spontaneous contraction .Glibenclamide ( Gli) was added to K-H solution before dexmendeto-midine.In the calcium-free K-H solution, calcium chloride and rynodine were added before dexmendeto-midine.The mechanisms of dexmendetomidine were studied .Results ① Dexmendetomidine reduced the amplitude of spontaneous contraction of duodenal smooth muscle in rabbits in a dose-dependent manner ( P0.05 ) .② Gli ( P <0.05 ) partly abolished the inhibitory effects of dexmendetomi-dine on duodenal smooth muscle .③ Dexmendetomi-dine inhibited the contraction of duodenum smooth muscle induced by calcium chloride ( P <0.05 ) and rynodine ( P<0.05 ) application into calcium-free K-H solution.Conclusion Dexmendetomidine inhibits the spontaneous contraction of duodenal smooth muscle of rabbits in vitro.The mechanisms may be related to ac-tivating ATP sensitive potassium channels , inhibition of the extracellular calcium influx via cell membrane and intracellular calcium release via sarcoplasmic reticulum in duodenal smooth muscle .
