Immunogenicity and safety of a recombinant fusion protein vaccine(V-01)against coronavirus disease 2019 in healthy adults:a randomized,double-blind,placebo-controlled,phaseⅡtrial

Background:Innovative coronavirus disease 2019(COVID-19)vaccines,with elevated global manufacturing capacity,enhanced safety and efficacy,simplified dosing regimens,and distribution that is less cold chain-dependent,are still global imperatives for tackling the ongoing pandemic.A previous phase I trial indicated that the recombinant COVID-19 vaccine(V-01),which contains a fusion protein(IFN-PADRE-RBD-Fc dimer)as its antigen,is safe and well tolerated,capable of inducing rapid and robust immune responses,and warranted further testing in additional clinical trials.Herein,we aimed to assess the immunogenicity and safety of V-01,providing rationales of appropriate dose regimen for further efficacy study.Methods:A randomized,double-blind,placebo-controlled phaseⅡclinical trial was initiated at the Gaozhou Municipal Centre for Disease Control and Prevention(Guangdong,China)in March 2021.Both younger(n=440;18–59 years of age)and older(n=440;≥60 years of age)adult participants in this trial were sequentially recruited into two distinct groups:two-dose regimen group in which participants were randomized either to follow a 10 or 25 mg of V-01 or placebo given intramuscularly 21 days apart(allocation ratio,3:3:1,n=120,120,40 for each regimen,respectively),or one-dose regimen groups in which participants were randomized either to receive a single injection of 50 mg of V-01 or placebo(allocation ratio,3:1,n=120,40,respectively).The primary immunogenicity endpoints were the geometric mean titers of neutralizing antibodies against live severe acute respiratory syndrome coronavirus 2,and specific binding antibodies to the receptor binding domain(RBD).The primary safety endpoint evaluation was the frequencies and percentages of overall adverse events(AEs)within 30 days after full immunization.Results:V-01 provoked substantial immune responses in the two-dose group,achieving encouragingly high titers of neutralizing antibody and anti-RBDimmunoglobulin,which peaked at day 35(161.9[95%confidence interval[CI]:133.3–196.7]and 149.3[95%CI:123.9–179.9]in 10 and 25 mg V-01 group of younger adults,respectively;111.6[95%CI:89.6–139.1]and 111.1[95%CI:89.2–138.4]in 10 and 25 mg V-01 group of older adults,respectively),and remained high at day 49 after a day-21 second dose;these levels significantly exceed those in convalescent serum from symptomatic COVID-19 patients(53.6,95%CI:31.3–91.7).Our preliminary data showthat V-01 is safe andwell tolerated,with reactogenicity predominantly being absent or mild in severity and only one vaccinerelated grade 3 or worse AE being observed within 30 days.The older adult participants demonstrated a more favorable safety profile compared with those in the younger adult group:with AEs percentages of 19.2%,25.8%,17.5%in older adults vs.34.2%,23.3%,26.7%in younger adults at the 10,25 mg V-01 two-dose group,and 50 mg V-01 one-dose group,respectively.Conclusions:The vaccine candidate V-01 appears to be safe and immunogenic.The preliminary findings support the advancement of the two-dose,10 mg V-01 regimen to a phaseⅢtrial for a large-scale population-based evaluation of safety and efficacy.

Humoral immune responses induced by anti-idiotypic antibody fusion protein of 6B11scFv/hGM-CSF in BALB/c mice

Background We have previously developed and characterized a monoclonal anti-idiotype antibody, designated 6B 11, which mimics an ovarian carcinoma associated antigen OC166-9 and whose corresponding monoclonal antibody is COC166-9 （Abl）. In this study, we evaluate the humoral immune responses induced by the fusion protein 6B11 single-chain variable fragment （scFv）/human granulocyte macrophage colony-stimulating factor （hGM-CSF） and 6B 1 lscFv in BALB/c mice. Methods The fusion protein 6B 11 scFv/hGM-CSF was constructed by fusing a recombinant single-chain variable fragment of 6B11scFv to GM-CSE BALB/c mice were administrated by 6B11scFv/hGM-CSF and 6B11scFv, respectively. Results The fusion protein 6B11scFv/hGM-CSF retained binding to the anti-mouse F（ab）2＇ and was also biologically active as measured by proliferation of human GM-CSF dependent cell TF1 in vitro. After immunization with the 6B11scFv/hGM-CSF and 6BllScFv, BALB/c mice showed significantly enhanced Ab3 antibody responses to 6B11 scFv/hGM-CSF compared with the 6B11 scFv alone. The level of Ab3 was the highest after the first week and maintained for five weeks after the last immunization. Another booster was given when the Ab3 titer descended, and it would reach to the high level in a week. Conclusion The fusion protein 6B11scFv/hGM-CSF can induce humoral immunity against ovarian carcinoma in vivo. We also provide the theoretical foundation for the application of the fusion protein 6B11 scFv/hGM-CSF for active immunotherapy of ovarian cancer.

Urokinase-targeted recombinant bacterial protein toxins-a rationally designed and engineered anticancer agent for cancer therapy

Urokinase-targeted recombinant bacterial protein toxins are a sort of rationally designed and engineered anticancer recombinant fusion proteins representing a novel class of agents for cancer therapy.Bacterial protein toxins have long been known as the primary virulence factor(s)for a variety of pathogenic bacteria and are the most powerful human poisons.On the other hand,it has been well documented that urokinase-type plasminogen activator(uPA)and urokinase plasminogen activator receptor(uPAR),making up the uPA system,are overexpressed in a variety of human tumors and tumor cell lines.The expression of uPA system is highly correlated with tumor invasion and metastasis.To exploit these characteristics in the design of tumor cell-selective cytotoxins,two prominent bacterial protein toxins,i.e.,the diphtheria toxin and anthrax toxin are deliberately engineered through placing a sequence targeted specifically by the uPA system to form anticancer recombinant fusion proteins.These uPA system-targeted bacterial protein toxins are activated selectively on the surface of uPA systemexpressing tumor cells,thereby killing these cells.This article provides a review on the latest progress in the exploitation of these recombinant fusion proteins as potent tumoricidal agents.It is perceptible that the strategies for cancer therapy are being innovated by this novel therapeutic approach.