Your browser doesn't support javascript.
Show: 20 | 50 | 100
Results 1 - 3 de 3
Add filters

Document Type
Year range
Preprint in English | bioRxiv | ID: ppbiorxiv-486173


Large-scale populations in the world have been vaccinated with COVID-19 vaccines, however, breakthrough infections of SARS-CoV-2 are still growing rapidly due to the emergence of immune-evasive variants, especially Omicron. It is urgent to develop effective broad-spectrum vaccines to better control the pandemic of these variants. Here, we present a mosaic-type trimeric form of spike receptor-binding domain (mos-tri-RBD) as a broad-spectrum vaccine candidate, which carries the key mutations from Omicron and other circulating variants. Tests in rats showed that the designed mos-tri-RBD, whether used alone or as a booster shot, elicited potent cross-neutralizing antibodies against not only Omicron but also other immune-evasive variants. Neutralizing antibody titers induced by mos-tri-RBD were substantially higher than those elicited by homo-tri-RBD (containing homologous RBDs from prototype strain) or the inactivated vaccine BBIBP-CorV. Our study indicates that mos-tri-RBD is highly immunogenic, which may serve as a broad-spectrum vaccine candidate in combating SARS-CoV-2 variants including Omicron.

Preprint in English | medRxiv | ID: ppmedrxiv-21268499


BackgroundThe increased coronavirus disease 2019 (COVID-19) breakthrough cases pose the need of booster vaccinations. In this study, we reported the safety and immunogenicity of a heterologous boost with a recombinant COVID-19 vaccine (CHO cells), named NVSI-06-07, as a third dose in participants who have previously received two doses of the inactivated vaccine (BBIBP-CorV) at pre-specified time intervals. Using homologous boost with BBIBP-CorV as control, the safety and immunogenicity of the heterologous boost with NVSI-06-07 against various SARS-CoV-2 strains, including Omicron, were characterized. MethodsThis study is a single-center, randomised, double-blinded, controlled phase 2 trial for heterologous boost of NVSI-06-07 in BBIBP-CorV recipients from the United Arab Emirates (UAE). Healthy adults (aged [≥]18 years) were enrolled and grouped by the specified prior vaccination interval of BBIBP-CorV, i.e., 1-3 months, 4-6 months or [≥]6 months, respectively, with 600 individuals per group. For each group, participants were randomly assigned at 1:1 ratio to receive either a heterologous boost of NVSI-06-07 or a homologous booster dose of BBIBP-CorV. The primary outcome was to comparatively assess the immunogenicity between heterologous and homologous boosts at 14 and 28 days post-boosting immunization, by evaluation of the geometric mean titers (GMTs) of IgG and neutralizing antibodies as well as the corresponding seroconversion rate ([≥]4-fold rise in antibody titers). The secondary outcomes were the safety profile of the boosting strategies within 30 days post vaccination. The exploratory outcome was the immune efficacy against Omicron and other variants of concern (VOCs) of SARS-CoV-2. This trial is registered with, NCT05033847. FindingsA total of 1800 individuals who have received two doses of BBIBP-CorV were enrolled, of which 899 participants received a heterologous boost of NVSI-06-07 and 901 received a homologous boost for comparison. No vaccine-related serious adverse event (SAE) and no adverse events of special interest (AESI) were reported. 184 (20{middle dot}47%) participants in the heterologous boost groups and 177 (19{middle dot}64%) in the homologous boost groups reported at least one adverse reaction within 30 days. Most of the local and systemic adverse reactions reported were grades 1 (mild) or 2 (moderate), and there was no significant difference in the overall safety between heterologous and homologous boosts. Immunogenicity assays showed that the seroconversion rates in neutralizing antibodies against prototype SARS-CoV-2 elicited by heterologous boost were 89{middle dot}96% - 97{middle dot}52% on day 28 post-boosting vaccination, which was much higher than what was induced by homologous boost (36{middle dot}80% - 81{middle dot}75%). Similarly, in heterologous NVSI-06-07 booster groups, the neutralizing geometric mean titers (GMTs) against the prototype strain increased by 21{middle dot}01 - 63{middle dot}85 folds from baseline to 28 days post-boosting vaccination, whereas only 4{middle dot}20 - 16{middle dot}78 folds of increases were observed in homologous BBIBP-CorV booster group. For Omicron variant, the neutralizing antibody GMT elicited by the homologous boost of BBIBP-CorV was 37{middle dot}91 (95%CI, 30{middle dot}35-47{middle dot}35), however, a significantly higher level of neutralizing antibodies with GMT 292{middle dot}53 (95%CI, 222{middle dot}81-384{middle dot}07) was induced by the heterologous boost of NVSI-06-07, suggesting that it may serve as an effective boosting strategy combating the pandemic of Omicron. The similar results were obtained for other VOCs, including Alpha, Beta and Delta, in which the neutralizing response elicited by the heterologous boost was also significantly greater than that of the homologous boost. In the participants primed with BBIBP-CorV over 6 months, the largest increase in the neutralizing GMTs was obtained both in the heterologous and homologous boost groups, and thus the booster vaccination with over 6 months intervals was optimal. InterpretationOur findings indicated that the heterologous boost with NVSI-06-07 was safe, well-tolerated and immunogenic in adults primed with a full regimen of BBIBP-CorV. Compared to homologous boost with a third dose of BBIBP-CorV, incremental increases in immune responses were achieved by the heterologous boost with NVSI-06-07 against SARS-CoV-2 prototype strain, Omicron variant, and other VOCs. The heterologous BBIBP-CorV/NVSI-06-07 prime-boosting vaccination may be valuable in preventing the pandemic of Omicron. The optimal booster strategy was the heterologous boost with NVSI-06-07 over 6 months after a priming with two doses of BBIBP-CorV. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSWe searched PubMed for clinical trials or prospective/cohort studies involving heterologous booster vaccination in non-immunocompromised population published up to Dec 25, 2021, using the term "(COVID) AND (vaccin*) AND (clinical trial OR cohort OR prospective) AND (heterologous) AND (booster OR prime-boost OR third dose)" with no language restrictions. Nine studies of heterologous prime-boost vaccinations with adenovirus-vector vaccines (ChAdOx1 nCov-19, Oxford-AstraZeneca, Ad26.COV2.S, Janssen) and mRNA vaccines (BNT162b2, Pfizer-BioNtech; mRNA1273, Moderna) were identified. The adenovirus-vector and mRNA heterologous prime-boost vaccination was found to be well tolerated and immunogenic. In individuals primed with adenovirus-vector vaccine, mRNA booster vaccination led to greater immune response than homologous boost. However, varied results were obtained on whether heterologous boost was immunogenically superior to the homologous mRNA prime-boost vaccination. Besides that, A preprint trial in population previously immunized with inactivated vaccines (CoronaVac, Sinovac Biotech) showed that the heterologous boost with adenovirus-vector vaccine (Convidecia, CanSino Biologicals) was safe and induced higher level of live-virus neutralizing antibodies than by the homogeneous boost. A pilot study reported that boosting with BNT162b2 in individuals primed with two doses of inactivated vaccines (BBIBP-CorV) was significantly more immunogenic than homologous vaccination with two-dose of BNT162b2. In addition, a preprint paper demonstrated that heterologous boost of ZF2001, a recombinant protein subunit vaccine, after CoronaVac or BBIBP-CorV vaccination potently improved the immunogenicity. But only a small size of samples was tested in this study and the live-virus neutralization was not detected. Till now, it is still lacking a formal clinical trial to evaluate the immunogenicity and safety of the heterologous prime-boost vaccination with an inactivated vaccine followed by a recombinant protein subunit-based vaccine. Added value of this studyTo our knowledge, this is the first reported result of a large-scale randomised, controlled clinical trial of heterologous prime-boost vaccination with an inactivated vaccine followed by a recombinant protein subunit vaccine. This trial demonstrated that the heterologous prime-booster vaccination with BBIBP-CorV/NVSI-06-07 is safe and immunogenic. Its immunoreactivity is similar to that of homologous vaccination with BBIBP-CorV. Compared to homologous boost, heterologous boost with NVSI-06-07 in BBIBP-CorV recipients elicited significantly higher immunogenicity not only against the SARS-CoV-2 prototype strain but also against Omicron and other variants of concern (VOCs). Implications of all the available evidenceBooster vaccination is considered an effective strategy to improve the protection efficacy of COVID-19 vaccines and control the epidemic waves of SARS-CoV-2. Data from our trial suggested that the booster vaccination of NVSI-06-07 in BBIBP-CorV recipients significantly improved the immune responses against various SARS-CoV-2 strains, including Omicron. Due to no Omicron-specific vaccine available currently, the BBIBP-CorV/NVSI-06-07 heterologous prime-boost might serve as an effective strategy combating Omicron variant. Besides that, BBIBP-CorV has been widely inoculated in population, and thus further boosting vaccination with NVSI-06-07 is valuable in preventing the COVID-19 pandemic. But further studies are needed to assess the long-term protection of BBIBP-CorV/NVSI-06-07 prime-booster vaccination.

Preprint in English | bioRxiv | ID: ppbiorxiv-448958


The spike (S) protein receptor-binding domain (RBD) of SARS-CoV-2 is an attractive target for COVID-19 vaccine developments, which naturally exists in a trimeric form. Here, guided by structural and computational analyses, we present a mutation-integrated trimeric form of RBD (mutI tri-RBD) as a broadly protective vaccine candidate, in which three RBDs were individually grafted from three different circulating SARS-CoV-2 strains including the prototype, Beta (B.1.351) and Kappa (B.1.617). The three RBDs were then connected end-to-end and co-assembled to possibly mimic the native trimeric arrangements in the natural S protein trimer. The recombinant expression of the mutI tri-RBD, as well as the homo-tri-RBD where the three RBDs were all truncated from the prototype strain, by mammalian cell exhibited correct folding, strong bio-activities, and high stability. The immunization of both the mutI tri-RBD and homo-tri-RBD plus aluminum adjuvant induced high levels of specific IgG and neutralizing antibodies against the SARS-CoV-2 prototype strain in mice. Notably, regarding to the "immune-escape" Beta (B.1.351) variant, mutI tri-RBD elicited significantly higher neutralizing antibody titers than homo-tri-RBD. Furthermore, due to harboring the immune-resistant mutations as well as the evolutionarily convergent hotspots, the designed mutI tri-RBD also induced strong broadly neutralizing activities against various SARS-CoV-2 variants, especially the variants partially resistant to homo-tri-RBD. Homo-tri-RBD has been approved by the China National Medical Products Administration to enter clinical trial (No. NCT04869592), and the superior broad neutralization performances against SARS-CoV-2 support the mutI tri-RBD as a more promising vaccine candidate for further clinical developments.