Recombinant Adenovirus Type-5 Ebola Virus Vaccine Clinical Trial And Human Neutralizing Monoclonal Antibody Sorting

Objectives:(1)We aimed to assess the safety,tolerance and immunogenicity of a novel recombinant adenovirus type-5 vector-based Ebola vaccine(Ad5-EBOV)developed by Chinese Ministry of Science and Technology and The National Health and Family Planning Commission,Beijing Institute of Biotechnology,and Tianjin CanSino Biotechnology in 18-60 years old healthy adults in China.(2)We sorted human neutralizing monoclonal antibody against Ebola virus by using glycoprotein(GP)specific probes and further verified the binding activity and neutralizing activity of these antibody with GP.which will provide technolog support for designing new vaceines and drugs.Methods:We did this single center,dose-escalating,randomized,double-blind,placebo-controlled,phasc Ⅰ clinical trial and boost extanding clinical trial in Vaccine Engineering Center in Taizhou and Jiangsu Provincial Center for Disease Control and Prevention.Healthy adults(aged 18-60 years)were sequentially enrolled and randomly assigned(1:1:1)to receive placebo,low-dose or high-dose Ad5-EBOV.A boosting vaccination with homologous vaccine was proceeded at month 6 after the prime immunization.The primary safety endpoint was occurrence of solicited adverse reactions within 7 days of vaccination.The prinmary immunogenicity endpoints were glycoprotein-specific antibody titres and T-cell responses at day 28 after the vaccination.We selected 8 volunteers with high GP specific antibody titers to isolate peripheral blood mononuelear cells(PBMC)at the 2 weeks after boost vaccination.Then we sorted the GP specific memory B cells by flow eytometry and amplified antiboy genes to construct antibody expression Iecombinant vector.At last we verified the binding activity and neutralizing activity of these antibodies.Results:(1)120 participants were enrolled and randomly assigned to receive placebo(n=40),low-dose vaccine(n=40),or high-dose vaccine(n=40)at the prime vaccination stage,Participants were followed up for safety and immunogenicity observations for 28 days without dropout and lost follow-up.10 participants dropped out since refusing to get boost vaccination with no statistical differences at months 6 after prime vaccination.The total solicited adverse reaction within 7 days of vaccination was mild and showed a clear dose-response relationship.GP-specific antibody titers were significantly increased in participants in the low-dose and high-dose vaccine groups at both day 14 and day 28.The level of geometric mean titre(GMT)is also dose-dependent.(2)In total,we selected 8 experiment volunteers and 1 control volunteer to isolate PBMC.The cell concentrations are among 3.3×106-8×106.Then we choose 4 volunteers with high cell concentrations to sort cell by flow cytometry and obtained 153 GP specific B cells.Only 10 heavy chain gene segments were amplilfied without pairing antibody segments.Conclusions:Our findings showed that the Ad5-EBOV viaccine is quite safe and immunogenic.One shot of the high-dose vaccine could mount GP-specifie humoral and T-cell response against !:bola virus in 14 days.The lower dose vaccine was also safe,but immunogenicity seemed to be more vulnerable to the pre-existing immunity of adenovirus 5.A homologous priming-boosting regimen with adenovirus type-5 Ebola vaccine at 6 months interval was able to elicit greater antibody responses with longer duration.For now,we sorted only 10 heavy chain gene segments,which is hard to verify the neutralizing activity of the antibody elicited by Ad5-EBOV.Therefore,we need to further investigate the functional verification and optimize the methods to sort more target antibodys.