Safety and immunogenicity of heterologous boost immunization with an adenovirus type-5-vectored and protein-subunit-based COVID-19 vaccine (Convidecia/ZF2001): a randomized, observer-blinded, placebo-controlled trial

BackgroundHeterologous boost vaccination has been proposed as an option to elicit stronger and broader, or longer-lasting immunity. We assessed the safety and immunogenicity of heterologous immunization with a recombinant adenovirus type-5-vectored COVID-19 vaccine (Convidecia) and a protein-subunit-based COVID-19 vaccine (ZF2001). Methods and FindingsWe did a randomized, observer-blinded, placebo-controlled trial in healthy adults previously received one dose of Convidecia. Participants were randomly assigned (2:1) to receive either ZF2001 (vaccine group) or a trivalent inactivated influenza vaccine (TIV) (placebo group) at either 28-day or 56-day intervals. For both regimens, all participants received the 2nd injection with ZF2001 at 4 months after a dose of ZF2001 or TIV, with three-dose schedules of Convidecia/Convidecia/ZF2001 at day 0, day 28 and month 5 (referred to as CV/ZF/ZF (D0-D28-M5)) and CV/ZF/ZF (D0-D56-M6), and two-dose schedules of CV/ZF (D0-M5) and CV/ZF (D0-M6). The primary outcome was the geometric mean titer (GMT) of the neutralizing antibodies against live SARS-CoV-2 virus 14 days after each boost vaccination. The safety outcome was 7-day reactogenicity, measured as solicited local or systemic adverse reactions after each vaccination. Between April 7, 2021, and May 6, 2021, 120 participants were enrolled, among whom 60 were randomly assigned to receive ZF2001 (n=40) or TIV (n=20) at a 28-day interval, and 60 were randomly assigned to receive ZF2001 (n=40) or TIV (n=20) at a 56-day interval. 113 (94.2%) participants received the 2nd injection with ZF2001 4 months after a dose of ZF2001 or TIV. A total of 26 participants (21.7%) reported solicited adverse events within 7 days post boost vaccinations, and all the reported adverse reactions were mild. Among participants receiving ZF001 as second dose, the GMTs of neutralizing antibodies increased to 58.4 IU/ml (42.8-79.8) in 0-28 regimen, and to 80.8 IU/ml (53.1-122.9) in 0-56 regimen at 14 days post first boost dose. The GMTs of neutralizing antibodies increased to 334.9 IU/ml (95% CI 230.4, 486.9) in C/Z/Z (D0-D28-M5) regimen, and 441.2 IU/ml (260.8, 746.4) in C/Z/Z (D0-D56-M6) regimen at 14 days after the third dose. Two-dose schedules of CV/ZF (D0-M5) and CV/ZF (D0-M6) induced comparable antibody level comparable with that elicited by three-dose schedules, with the GMTs of 282.9 IU/ml (142.5, 561.8) and 293.9 IU/ml (137.6, 627.9), respectively. Study limitations include the absence of vaccine effectiveness in real-world, and current lack of immune persistence data and the neutralizing antibodies to Omicron. ConclusionsHeterologous boosting with ZF001 following primary vaccination of Convidecia is safe and more immunogenic than a single dose of Convidecia. These results support flexibility in cooperating viral vectored vaccines and recombinant protein vaccine. Trial RegistrationClinicalTrial.gov NCT04833101

Reduced sera neutralization to Omicron SARS-CoV-2 by bothinactivated and protein subunit vaccines and the convalescents

Omicron variant continues to spread all over the world. There are lots of scientific questions remaining to be answered for such a devastating variant. There are a dozen of vaccines already in clinical use. The very urgent scientific question would be whether or not these vaccines can protect Omicron variant. Here, we tested the sera from both convalescents and vaccine recipients receiving either inactivated or protein subunits vaccines (CoronaVac from Sinovac, or BBIBP-CoV from Sinopharm, or ZF2001 from Zhifei longcom) for the binding antibody titers (ELISA) and neutralization antibodies titers (pseudovirus neutralization assay). We showed that Omicron do have severe immune escape in convalescents, with 15 of 16 were negative in neutralization. By contrast, in vaccinees who received three jabs of inactivated or protein subunit vaccine, the neutralizing activity was much better preserved. Especially in the ZF2001 group with an extended period of the second and third jab (4-6 months) remains 100% positive in Omicron neutralization, with only 3.1-folds reduction in neutralizing antibody (NAb) titer. In this case, we proposed that, the multi-boost strategy with an extended interval between the second and third jab for immune maturation would be beneficial for NAb against devastating variants such as Omicron.

Neutralization of recombinant RBD-subunit vaccine ZF2001-elicited antisera to SARS-CoV-2 variants including Delta

SARS-CoV-2 variants brought new waves of infection worldwide. In particular, Delta variant (B.1.617.2 lineage) has become predominant in many countries. These variants raised the concern for their potential immune escape to the currently approved vaccines. ZF2001 is a subunit vaccine received emergency use authorization (EUA) in both China and Uzbekistan, with more than 100-million doses administrated with a three-dose regimen. The tandem-repeat dimer of SARS-CoV-2 spike protein receptor binding domain (RBD) was used as the antigen. In this work, we evaluated the neutralization of ZF2001-elicited antisera to SARS-CoV-2 variants including all four variants of concern (Alpha, Beta, Gamma and Delta) and other three variants of interest (Epsilon, Eta and Kappa) by pseudovirus-based assay. We found antisera preserved majority of the neutralizing activity against these variants. E484K/Q substitution is the key mutation to reduce the RBD-elicited sera neutralization. Moreover, ZF2001-elicited sera with a prolonged intervals between the second and third dose enhanced the neutralizing titers and resilience to SARS-CoV-2 variants.

A tandem-repeat dimeric RBD protein-based COVID-19 vaccine ZF2001 protects mice and nonhuman primates

A safe, efficacious and deployable vaccine is urgently needed to control COVID-19 pandemic. We report here the preclinical development of a COVID-19 vaccine candidate, ZF2001, which contains tandem-repeat dimeric receptor-binding domain (RBD) protein with alum-based adjuvant. We assessed vaccine immunogenicity and efficacy in both mice and non-human primates (NHPs). ZF2001 induced high levels of RBD-binding and SARS-CoV-2 neutralizing antibody in both mice and NHPs, and also elicited balanced TH1/TH2 cellular responses in NHPs. Two doses of ZF2001 protected Ad-hACE2-transduced mice against SARS-CoV-2 infection, as detected by reduced viral RNA and relieved lung injuries. In NHPs, vaccination of either 25 g or 50 g ZF2001 prevented infection with SARS-CoV-2 in lung, trachea and bronchi, with milder lung lesions. No evidence of disease enhancement is observed in both models. ZF2001 is being evaluated in the ongoing international multi-center Phase 3 trials (NCT04646590) and has been approved for emergency use in Uzbekistan.

Recombinant chimpanzee adenovirus AdC7 expressing dimeric tandem-repeat RBD of SARS-CoV-2 spike protein protects mice against COVID-19

A safe and effective vaccine is urgently needed to control the unprecedented COVID-19 pandemic. Four adenovirus vectored vaccines expressing spike (S) protein have advanced into phase 3 trials, with three approved for use. Here, we generated several recombinant chimpanzee adenovirus (AdC7) vaccines expressing S, receptor-binding domain (RBD) or dimeric tandem-repeat RBD (RBD-tr2). We found vaccination via either intramuscular or intranasal route was highly immunogenic in mice to elicit both humoral and cellular (Th1-based) immune responses. AdC7-RBD-tr2 showed higher antibody responses compared with both AdC7-S and AdC7-RBD. Intranasal administration of AdC7-RBD-tr2 additionally induced mucosal immunity with neutralizing activity in bronchoalveolar lavage fluid. Either single-dose or two-dose mucosal administration of AdC7-RBD-tr2 protected mice against SARS-CoV-2 challenge, with undetectable subgenomic RNA in lung and relieved lung injury. These results support AdC7-RBD-tr2 as a promising COVID-19 vaccine candidate.

Neutralization of SARS-CoV-2 VOC 501Y.V2 by human antisera elicited by both inactivated BBIBP-CorV and recombinant dimeric RBD ZF2001 vaccines

Recently, the emerged and rapidly spreading SARS-CoV-2 variant of concern (VOC) 501Y.V2 with 10 amino acids in spike protein were found to escape host immunity induced by infection or vaccination. Global concerns have been raised for its potential to affect vaccine efficacy. Here, we evaluated the neutralization activities of two vaccines developed in China against 501Y.V2. One is licensed inactivated vaccine BBIBP-CorV and the other one is recombinant dimeric receptor-binding domain (RBD) vaccine ZF2001. Encouragingly, both vaccines largely preserved neutralizing titres, with slightly reduction, against 501Y.V2 authentic virus compare to their titres against both original SARS-CoV-2 and the currently circulating D614G virus. These data indicated that 501Y.V2 variant will not escape the immunity induced by vaccines targeting whole virus or RBD.

Avian influenza A (H7N9) virus: from low pathogenic to highly pathogenic / 医学前沿

The avian influenza A (H7N9) virus is a zoonotic virus that is closely associated with live poultry markets. It has caused infections in humans in China since 2013. Five waves of the H7N9 influenza epidemic occurred in China between March 2013 and September 2017. H7N9 with low-pathogenicity dominated in the first four waves, whereas highly pathogenic H7N9 influenza emerged in poultry and spread to humans during the fifth wave, causing wide concern. Specialists and officials from China and other countries responded quickly, controlled the epidemic well thus far, and characterized the virus by using new technologies and surveillance tools that were made possible by their preparedness efforts. Here, we review the characteristics of the H7N9 viruses that were identified while controlling the spread of the disease. It was summarized and discussed from the perspectives of molecular epidemiology, clinical features, virulence and pathogenesis, receptor binding, T-cell responses, monoclonal antibody development, vaccine development, and disease burden. These data provide tools for minimizing the future threat of H7N9 and other emerging and re-emerging viruses, such as SARS-CoV-2.

Safety and immunogenicity of a recombinant tandem-repeat dimeric RBD protein vaccine against COVID-19 in adults: pooled analysis of two randomized, double-blind, placebo-controlled, phase 1 and 2 trials

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.

Purification, crystallographic analysis of rhesus MHC-I Mamu-A*02 complexed with simian immunodeficiency virus nonapeptide / 生物工程学报

Rhesus macaque (Macaca mulatta) is the best model to study of human immunodeficiency virus (HIV) infection and to develop acquired immunodeficiency syndrome (AIDS) vaccine. The crystal structure of its major histocompatibility antigen complex (MHC) is helpful to understand the mechanism of HIV immune evasion. In this study, we cloned the light chain (beta2m) of MHC class I allele of rhesus macaques, Mamu-A*02, and inserted it into pET21a(+) vector. We transfected the recombinant plasmid pET21a(+)-Mamu-beta2m and pET21a(+)-Mamu-alpha into BL21(DE3). Mamu-A*02 and beta2m were expressed in the form of inclusion bodies in BL21 (DE3). We co-refolded the inclusion bodies of Mamu-alpha and Mamu-beta2m with SIV nonapeptide YY9 and obtained the correct refolded protein complex. Then we purified the protein complex by the gel filtration and anion-exchange column. With hanging-drop method, we screened and optimized for the protein crystal. We managed to collect a X-ray diffraction with the resolution to 2.8 angstroms in the condition of 0.1 mol/L BIS-TRIS (pH5.5), 2.0 mol/L(NH4)2SO4. This crystal belong to perpendicular space group P2(1)2(1)2(1), with unit-cell parameters a = 128.99 angstroms, b = 129.01 angstroms, c = 129.03 angstroms. This data is available for the structure determination.