The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in an unprecedented public health crisis. Because of the novelty ...of the virus, there are currently no SARS-CoV-2-specific treatments or vaccines available. Therefore, rapid development of effective vaccines against SARS-CoV-2 are urgently needed. Here, we developed a pilot-scale production of PiCoVacc, a purified inactivated SARS-CoV-2 virus vaccine candidate, which induced SARS-CoV-2-specific neutralizing antibodies in mice, rats, and nonhuman primates. These antibodies neutralized 10 representative SARS-CoV-2 strains, suggesting a possible broader neutralizing ability against other strains. Three immunizations using two different doses, 3 or 6 micrograms per dose, provided partial or complete protection in macaques against SARS-CoV-2 challenge, respectively, without observable antibody-dependent enhancement of infection. These data support the clinical development and testing of PiCoVacc for use in humans.
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.
•ACE2 is abundantly expressed in gastrointestinal system, kidney, testis and heart.•The expression of ACE2 is upregulated in smokers, but not affected by sex and age.•Amino acids that form polar ...contacts between ACE2 and RBD are essential for binding.•Variants may change binding ability to ACE2 and cause cross‐species transmission.
Since the outbreak at the end of 2019, SARS-CoV-2 has been spreading around the world for more than one year. Scientists have been intensely conducting research on this newly emerged coronavirus and the disease caused by it. Angiotensin-converting enzyme 2 (ACE2), as a receptor mediating the cellular entry of SARS-CoV-2, has become a hot spot for researchers. Here, we summarized the recent progresses on the function, expression and distribution characteristics of ACE2 in human body and among populations. We further discussed the interaction mechanism of ACE2 and SARS-CoV-2 S protein, focusing on key residues that effect interaction and binding ability of SARS-CoV-2 variants. This will facilitate researchers to better understand SARS-CoV-2 infection and transmission route, adaptation mechanism, and designing treatment strategies.
An avian-origin human-infecting influenza (H7N9) virus was recently identified in China. We have evaluated the viral hemagglutinin (HA) receptor-binding properties of two human H7N9 isolates, ...A/Shanghai/1/2013 (SH-H7N9) (containing the avian-signature residue Gln²²⁶) and A/Anhui/1/2013 (AH-H7N9) (containing the mammalian-signature residue Leu²²⁶). We found that SH-H7N9 HA preferentially binds the avian receptor analog, whereas AH-H7N9 HA binds both avian and human receptor analogs. Furthermore, an AH-H7N9 mutant HA (Leu²²⁶ → Gln) was found to exhibit dual receptor-binding property, indicating that other amino acid substitutions contribute to the receptor-binding switch. The structures of SH-H7N9 HA, AH-H7N9 HA, and its mutant in complex with either avian or human receptor analogs show how AH-H7N9 can bind human receptors while still retaining the avian receptor-binding property.
C-type lectins are a family of proteins with carbohydrate-binding activity. Several C-type lectins in mammals or arthropods are employed as receptors or attachment factors to facilitate flavivirus ...invasion. We previously identified a C-type lectin in Aedes aegypti, designated as mosquito galactose specific C-type lectin-1 (mosGCTL-1), facilitating the attachment of West Nile virus (WNV) on the cell membrane. Here, we first identified that 9 A. aegypti mosGCTL genes were key susceptibility factors facilitating DENV-2 infection, of which mosGCTL-3 exhibited the most significant effect. We found that mosGCTL-3 was induced in mosquito tissues with DENV-2 infection, and that the protein interacted with DENV-2 surface envelop (E) protein and virions in vitro and in vivo. In addition, the other identified mosGCTLs interacted with the DENV-2 E protein, indicating that DENV may employ multiple mosGCTLs as ligands to promote the infection of vectors. The vectorial susceptibility factors that facilitate pathogen invasion may potentially be explored as a target to disrupt the acquisition of microbes from the vertebrate host. Indeed, membrane blood feeding of antisera against mosGCTLs dramatically reduced mosquito infective ratio. Hence, the immunization against mosGCTLs is a feasible approach for preventing dengue infection. Our study provides a future avenue for developing a transmission-blocking vaccine that interrupts the life cycle of dengue virus and reduces disease burden.
The ongoing COVID‐19 pandemic caused by SARS‐CoV‐2 has led to millions of deaths worldwide. Streptococcus pneumoniae (S. pneumoniae) remains a major cause of mortality in underdeveloped countries. A ...vaccine that prevents both SARS‐CoV‐2 and S. pneumoniae infection represents a long‐sought “magic bullet”. Herein, a nanoparticle vaccine, termed SCTV01B, is rationally developed by using the capsular polysaccharide of S. pneumoniae serotype 14 (PPS14) as the backbone to conjugate with the recombinant receptor‐binding domain (RBD) of the SARS‐CoV‐2 spike protein. The final formulation of conjugated nanoparticles in the network structure exhibits high thermal stability. Immunization with SCTV01B induces potent humoral and Type 1/Type 2 T helper cell (Th1/Th2) cellular immune responses in mice, rats, and rhesus macaques. In particular, SCTV01B‐immunized serum not only broadly cross‐neutralizes all SARS‐CoV‐2 variants of concern (VOCs), including the most recent Omicron variant, but also shows high opsonophagocytic activity (OPA) against S. pneumoniae serotype 14. Finally, SCTV01B vaccination confers protection against challenges with the SARS‐CoV‐2 mouse‐adapted strain and the original strain in established murine models. Collectively, these promising preclinical results support further clinical evaluation of SCTV01B, highlighting the potency of polysaccharide‐RBD‐conjugated nanoparticle vaccine platforms for the development of vaccines for COVID‐19 and other infectious diseases.
A bivalent nanoparticle vaccine is rationally developed by conjugating capsular polysaccharide of Streptococcus pneumoniae serotype 14 with the receptor‐binding domain (RBD) of SARS‐CoV‐2 spike protein. Immunization with this vaccine induces potent protective immune responses against both SARS‐CoV‐2 variants and S. pneumoniae. This universal polysaccharide–protein‐conjugated vaccine platform provides a new tool to fight against cocirculating viral and bacterial pathogens.
An epidemic of an avian-origin H7N9 influenza virus has recently emerged in China, infecting 134 patients of which 45 have died. This is the first time that an influenza virus harboring an N9 ...serotype neuraminidase （NA） has been known to infect humans. H7N9 viruses are divergent and at least two distinct NAs and hemagglutinins （HAs） have been found, respectively, from clinical isolates. The prototypes of these viruses are A/Anhui/1/2013 and A/ Shanghai/I/2013. NAs from these two viruses are distinct as the A/Shanghai/I/2013 NA has an R294K substitution that can confer NA inhibitor oseltamivir resistance. Oseltamivir is by far the most commonly used anti-influenza drug due to its potency and high bioavailability. In this study, we show that an R294K substitution results in multidrug resistance with extreme oseltamivir resistance （over 100 000-fold） using protein- and virus-based assays. To determine the molecular basis for the inhibitor resistance, we solved high-resolution crystal structures of NAs from A/Anhui/1/2013 N9 （R294-containing） and A/Shanghai/I/2013 N9 （K294-containing）. R294K substitution results in an unfavorable E276 conformation for oseltamivir binding, and consequently loss of inhibitor carboxylate interactions, which compromises the binding of all classical NA ligands/inhibitors. Moreover, we found that R294K substitution results in reduced NA catalytic efficiency along with lower viral fitness. This helps to explain why K294 has predominantly been found in clinical cases of H7N9 infection under the selective pressure of oseltamivir treatment and not in the dominant human-infecting viruses. This implies that oseltamivir can still be efficiently used in the treatment of H7N9 infections.
Viral antigen detection test is the most common method used to detect viruses in the field rapidly. However, due to the low sensitivity, it can only be used as an auxiliary diagnosis method for virus ...infection. Improving sensitivity is crucial for developing more accurate viral antigen tests. Nano luciferase (Nluc) is a sensitive reporter that has not been used in virus detection. In this study, we produced an intracellularly Nluc labeled detection antibody (Nluc-ch2C5) and evaluated its ability to improve the detection sensitivity of respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens. Compared with the traditional horse-radish peroxidase (HRP) labeled antibody (HRP-ch2C5), Nluc-ch2C5 was 41 times more sensitive for inactivated SARS-CoV-2 virus by sandwich chemiluminescence ELISA. Then we applied Nluc-ch2C5 to establish an automatic magnet chemiluminescence immune assay (AMCA) for the SARS-CoV-2 viral spike protein, the limit of detection was 68 pfu/reaction. The clinical sensitivity and specificity reached 75% (24/32) and 100% (48/48) using 32 PCR-positive and 48 PCR-negative swab samples for clinical evaluation, which is more sensitive than the commercial ELSA kit and colloid gold strip kit. Here, monoclonal antibody ch2C5 served as a model antibody and the SARS-CoV-2 served as a model pathogen. The Nluc labeled detecting antibody (Nluc-ch2C5) significantly improved the detection sensitivity of SARS-CoV-2 antigen. This labeling principle applies to other viral infections, so this labeling and test format could be expected to play an important role in detecting other virus antigens.
Dengue is the most widespread vector-borne viral disease caused by dengue virus (DENV) for which there are no safe, effective drugs approved for clinical use. Here, by using sequential antigen ...panning of a yeast antibody library derived from healthy donors against the DENV envelop protein domain III (DIII) combined with depletion by an entry defective DIII mutant, we identified a cross-reactive human monoclonal antibody (mAb), m366.6, which bound with high affinity to DENV DIII from all four DENV serotypes. Immunogenetic analysis indicated that m366.6 is a germline-like mAb with very few somatic mutations from the closest VH and Vλ germline genes. Importantly, we demonstrated that it potently neutralized DENV both in vitro and in the mouse models of DENV infection without detectable antibody-dependent enhancement (ADE) effect. The epitope of m366.6 was mapped to the highly conserved regions on DIII, which may guide the design of effective dengue vaccine immunogens. Furthermore, as the first germline-like mAb derived from a naïve antibody library that could neutralize all four DENV serotypes, the m366.6 can be a tool for exploring mechanisms of DENV infection, and is a promising therapeutic candidate.
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