Project description:The disease caused by SARS-CoV-2 infection threatens human health. In this study, we used high-pressure homogenization technology not only to efficiently drive the bacterial membrane to produce artificial vesicles but also to force the fusion protein ClyA-receptor binding domain (RBD) to pass through gaps in the bacterial membrane to increase the contact between ClyA-RBD and the membrane. Therefore, the load of ClyA-RBD on the membrane is substantially increased. Using this technology, we constructed a "ring-like" bacterial biomimetic vesicle (BBV) loaded with polymerized RBD (RBD-BBV). RBD-BBVs injected subcutaneously can accumulate in lymph nodes, promote antigen uptake and processing, and elicit SARS-CoV-2-specific humoral and cellular immune responses in mice. In conclusion, we evaluated the potential of this novel bacterial vesicle as a vaccine delivery system and provided a new idea for the development of SARS-CoV-2 vaccines.
Project description:There is an urgent need to develop new vaccination strategies to elevate the cross-neutralization against different SARS-CoV-2 strains. In this study, we construct the spherical amantadine-assembled nanostimulator (AAS). Amantadine as immunostimulating molecules are displayed on the outermost layer of AAS. Molecular mechanism analysis reveals that AAS can activate RIG-I-like receptor (RLR) signaling pathway to increase the expression of type I interferons in vivo. AAS-mediated activation of RLR signaling pathway further promotes the maturation and proliferation of dendritic cells (DCs) and T helper cells (Ths), finally activating B cells to produce potent antibody responses. In performance evaluation experiments, the mixture of AAS and dimeric RBD significantly enhances RBD-specific humoral responses (4-fold IgG, 3.5-fold IgG2a, 3.3-fold IgG2b, 3.8-fold IgG3 and 1.3-fold IgM), in comparison to aluminum adjuvant-assistant dimeric RBD. Importantly, AAS dramatically elevates dimeric RBD-elicited cross-neutralization against different SARS-CoV-2 strains such as Wuhan-Hu-1 (9-fold), B.1.1.7 (UK variant, 15-fold), B.1.351 (South African variant, 4-fold) and B.1.617.2 (India variant, 7-fold). Our study verifies the mechanism of AAS in activating RLR signaling pathway in host immune system and highlights the power of AAS in improving antigen-elicited cross-neutralization against different SARS-CoV-2 strains.
Project description:SARS-CoV-2 variants could induce immune escape by mutations on the receptor-binding domain (RBD) and N-terminal domain (NTD). Here we report the humoral immune response to circulating SARS-CoV-2 variants, such as 501Y.V2 (B.1.351), of the plasma and neutralizing antibodies (NAbs) elicited by CoronaVac (inactivated vaccine), ZF2001 (RBD-subunit vaccine) and natural infection. Among 86 potent NAbs identified by high-throughput single-cell VDJ sequencing of peripheral blood mononuclear cells from vaccinees and convalescents, near half anti-RBD NAbs showed major neutralization reductions against the K417N/E484K/N501Y mutation combination, with E484K being the dominant cause. VH3-53/VH3-66 recurrent antibodies respond differently to RBD variants, and K417N compromises the majority of neutralizing activity through reduced polar contacts with complementarity determining regions. In contrast, the 242-244 deletion (242-244Δ) would abolish most neutralization activity of anti-NTD NAbs by interrupting the conformation of NTD antigenic supersite, indicating a much less diversity of anti-NTD NAbs than anti-RBD NAbs. Plasma of convalescents and CoronaVac vaccinees displayed comparable neutralization reductions against pseudo- and authentic 501Y.V2 variants, mainly caused by E484K/N501Y and 242-244Δ, with the effects being additive. Importantly, RBD-subunit vaccinees exhibit markedly higher tolerance to 501Y.V2 than convalescents, since the elicited anti-RBD NAbs display a high diversity and are unaffected by NTD mutations. Moreover, an extended gap between the third and second doses of ZF2001 leads to better neutralizing activity and tolerance to 501Y.V2 than the standard three-dose administration. Together, these results suggest that the deployment of RBD-vaccines, through a third-dose boost, may be ideal for combating SARS-CoV-2 variants when necessary, especially for those carrying mutations that disrupt the NTD supersite.
Project description:Variants of SARS-CoV-2 continue to emerge and evade immunity, resulting in breakthrough infections in vaccinated populations. Continued vaccination with vaccines based on the antigens of newly emerged variants does not necessarily result in long-lasting protection. Thus, there is an urgent need for the development of vaccines with a broad spectrum of protective effects. In this study, we selected hotspot mutations in the receptor binding domain (RBD) based on immune escape properties and integrated them into the original RBD protein to obtain a complexed RBD protein (cRBD). We designed a total of three cRBD (cRBD1-3) and thoroughly evaluated their immunological properties. Compared with the BA.1 RBD protein, the cRBDs induced higher levels and broader spectrum of neutralizing antibodies, with cRBD3 being the best performer. In vivo protective capacity of cRBDs was further validated in Balb/c mice attacked by live virus. In order to investigate the reason for the broad protective efficacy of cRBD, whole blood from mice that had completed the immunization process was subjected to BCR sequencing. BCR transcriptome analysis found differences in the use of VJ pairs in IGH among the groups.
Project description:Coronavirus Disease 2019 (COVID-19) caused by a novel betacoronavirus SARS-CoV-2 has been an ongoing global pandemic. Several vaccines have been developed to control the COVID-19, but the potential effectiveness of the mucosal vaccine remains to be documented. In this study, we constructed a recombinant L. plantarum LP18:RBD expressing the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein via the surface anchoring route. The amount of the RBD protein was maximally expressed under the culture condition with 200 ng/mL of inducer at 33 °C for 6 h. Further, we evaluated the immune response in mice via the intranasal administration of LP18:RBD. The results showed that the LP18:RBD significantly elicited RBD-specific mucosal IgA antibodies in respiratory tract and intestinal tract. The percentages of CD3 + CD4+ T cells in spleens of mice administrated with the LP18:RBD were also significantly increased. This indicated that LP18:RBD could induce a humoral immune response at the mucosa, and it could be used as a mucosal vaccine candidate against the SARS-CoV-2 infection. We provided the first experimental evidence that the recombinant L. plantarum LP18:RBD could initiate immune response in vivo, which implies that the mucosal immunization using recombinant LAB system could be a promising vaccination strategy to prevent the COVID-19 pandemic.
Project description:The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) kappa (B.1.617.1) variant represented the main variant of concern (VOC) for the epidemic in India in May 2021. We have previously established a technology platform for rapidly preparing SARS-CoV-2 receptor-binding domain (RBD) candidate vaccines based on glycoengineered Pichia pastoris. Our previous study revealed that the wild-type RBD (WT-RBD) formulated with aluminum hydroxide and CpG 2006 adjuvant effectively induces neutralizing antibodies in BALB/c mice. In the present study, a glycoengineered P. pastoris expression system was used to prepare recombinant kappa-RBD candidate vaccine. Kappa-RBD formulated with CpG and alum induced BALB/c mice to produce a potent antigen-specific antibody response and neutralizing antibody titers against pseudoviruses of SARS-CoV-2 kappa, delta, lambda, beta, and omicron variants and WT. Therefore, the recombinant kappa-RBD vaccine has sufficient potency to be a promising COVID-19 vaccine candidate.
Project description:We analyzed data from two ongoing COVID-19 longitudinal serological surveys in Orange County, CA., between April 2020 and March 2021. A total of 8476 finger stick blood specimens were collected before and after a vaccination campaign. IgG levels were determined using a multiplex antigen microarray containing antigens from SARS-CoV-2, SARS, MERS, Common CoV, and Influenza. Twenty-six percent of specimens from unvaccinated Orange County residents in December 2020 were SARS-CoV-2 seropositive; out of 852 seropositive individuals 77 had symptoms and 9 sought medical care. The antibody response was predominantly against nucleocapsid (NP), full length, and S2 domain of spike. Anti-receptor binding domain (RBD) reactivity was low and not cross-reactive against SARS S1 or SARS RBD. A vaccination campaign at the University of California Irvine Medical Center (UCIMC) started on December, 2020 and 6724 healthcare workers were vaccinated within 3 weeks. Seroprevalence increased from 13% pre-vaccination to 79% post-vaccination in January, 93% in February, and 99% in March. mRNA vaccination induced higher antibody levels than natural exposure, especially against the RBD domain and cross-reactivity against SARS RBD and S1 was observed. Nucleocapsid protein antibodies can be used to distinguish vaccinees to classify pre-exposure to SARS-CoV-2 Previously infected individuals developed higher antibody titers to the vaccine than non pre-exposed individuals. Hospitalized patients in intensive care with severe disease reach significantly higher antibody levels than mild cases, but lower antibody levels compared to the vaccine. These results indicate that mRNA vaccination rapidly induces a much stronger and broader antibody response than SARS-CoV-2 infection.
Project description:Global concerns arose as the emerged and rapidly spreading SARS-CoV-2 variants might escape host immunity induced by vaccination. In this study, a heterologous prime-boost immunization strategy for COVID-19 was designed to prime with a DNA vaccine encoding wild type (WT) spike protein receptor-binding domain (RBD) followed by S1 protein-based vaccine in rabbits. Four vaccine-elicited rabbit monoclonal antibodies (RmAbs), including 1H1, 9H1, 7G5, and 5E1, were isolated for biophysical property, neutralization potency and sequence analysis. All RmAbs recognized RBD or S1 protein with KD in the low nM or sub nM range. 1H1 and 9H1, but neither 7G5 nor 5E1, can bind to all RBD protein variants derived from B.1.351. All four RmAbs were able to neutralize wild type (WT) SARS-CoV-2 strain in pseudovirus assay, and 1H1 and 9H1 could neutralize the SARS-CoV-2 WT authentic virus with IC50 values of 0.136 and 0.026 μg/mL, respectively. Notably, 1H1 was able to neutralize all 6 emerging SARS-CoV-2 variants tested including D614G, B.1.1.7, B.1.429, P.1, B.1.526, and B.1.351 variants, and 5E1 could neutralize against the above 5 variants except P.1. Epitope binning analysis revealed that 9H1, 5E1 and 1H1 recognized distinct epitopes, while 9H1 and 7G5 may have overlapping but not identical epitope. In conclusion, DNA priming protein boost vaccination was an effective strategy to induce RmAbs with potent neutralization capability against not only SARS-CoV-2 WT strain but also emergent variants, which may provide a new avenue for effective therapeutics and point-of-care diagnostic measures.