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1.
Cell Host Microbe ; 2022 Oct 18.
Article in English | MEDLINE | ID: covidwho-2068781

ABSTRACT

SARS-CoV-2 spread in humans results in continuous emergence of new variants, highlighting the need for vaccines with broad-spectrum antigenic coverage. Using inter-lineage chimera and mutation-patch strategies, we engineered a recombinant monomeric spike variant (STFK1628x) that contains key regions and residues across multiple SAR-CoV-2 variants. STFK1628x demonstrated high immunogenicity and mutually complementary antigenicity to its prototypic form (STFK). In hamsters, a bivalent vaccine composed of STFK and STFK1628x elicited high titers of broad-spectrum neutralizing antibodies to 19 circulating SARS-CoV-2 variants, including Omicron sublineages BA.1, BA.1.1, BA.2, BA.2.12.1, BA.2.75, and BA.4/5. Furthermore, this vaccine conferred robust protection against intranasal challenges by either SARS-CoV-2 ancestral strain or immune-evasive Beta and Omicron BA.1. Strikingly, vaccination with the bivalent vaccine in hamsters effectively blocked within-cage virus transmission of ancestral SARS-CoV-2, Beta variant, and Omicron BA.1 to unvaccinated sentinels. Thus, our study provided insight and antigen candidates for the development of next-generation COVID-19 vaccines.

2.
Nat Biotechnol ; 2022 Aug 11.
Article in English | MEDLINE | ID: covidwho-1996868

ABSTRACT

CRISPR-Cas13 systems have recently been used for targeted RNA degradation in various organisms. However, collateral degradation of bystander RNAs has limited their in vivo applications. Here, we design a dual-fluorescence reporter system for detecting collateral effects and screening Cas13 variants in mammalian cells. Among over 200 engineered variants, several Cas13 variants including Cas13d and Cas13X exhibit efficient on-target activity but markedly reduced collateral activity. Furthermore, transcriptome-wide off-targets and cell growth arrest induced by Cas13 are absent for these variants. High-fidelity Cas13 variants show similar RNA knockdown activity to wild-type Cas13 but no detectable collateral damage in transgenic mice or adeno-associated-virus-mediated somatic cell targeting. Thus, high-fidelity Cas13 variants with minimal collateral effects are now available for targeted degradation of RNAs in basic research and therapeutic applications.

3.
Cell Rep ; 38(12): 110558, 2022 03 22.
Article in English | MEDLINE | ID: covidwho-1797096

ABSTRACT

Mutations in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike receptor-binding domain (RBD) may alter viral host tropism and affect the activities of neutralizing antibodies. Here, we investigated 153 RBD mutants and 11 globally circulating variants of concern (VOCs) and variants of interest (VOIs) (including Omicron) for their antigenic changes and cross-species tropism in cells expressing 18 ACE2 orthologs. Several RBD mutations strengthened viral infectivity in cells expressing ACE2 orthologs of non-human animals, particularly those less susceptible to the ancestral strain. The mutations surrounding amino acids (aas) 439-448 and aa 484 are more likely to cause neutralization resistance. Strikingly, enhanced cross-species infection potential in the mouse and ferret, instead of the neutralization-escape scores of the mutations, account for the positive correlation with the cumulative prevalence of mutations in humans. These findings present insights for potential drivers of circulating SARS-CoV-2 variants and provide informative parameters for tracking and forecasting spreading mutations.


Subject(s)
COVID-19 , SARS-CoV-2 , Animals , Ferrets , Humans , Membrane Glycoproteins/metabolism , Mice , SARS-CoV-2/genetics , Spike Glycoprotein, Coronavirus , Tropism , Viral Envelope Proteins
4.
Cell reports ; 2022.
Article in English | EuropePMC | ID: covidwho-1728589

ABSTRACT

Zhang et al. show in vitro cross-species infectivity and neutralization-escape characteristics of 153 SARS-CoV-2 RBD mutants and 11 globally circulating VOC/VOI variants. They reveal an association between enhanced cross-species infection potential and the current cumulative prevalence of mutations, which can inform surveillance and forecasting of SARS-CoV-2 spike mutations.

5.
EuropePMC;
Preprint in English | EuropePMC | ID: ppcovidwho-327136

ABSTRACT

The widespread SARS-CoV-2 in humans results in the continuous emergence of new variants. Recently emerged Omicron variant with multiple spike mutations sharply increases the risk of breakthrough infection or reinfection, highlighting the urgent need for new vaccines with broad-spectrum antigenic coverage. Using inter-lineage chimera and mutation patch strategies, we engineered a recombinant monomeric spike variant (STFK1628x), which showed high immunogenicity and mutually complementary antigenicity to its prototypic form (STFK). In hamsters, a bivalent vaccine comprised of STFK and STFK1628x elicited high titers of broad-spectrum antibodies to neutralize all 14 circulating SARS-CoV-2 variants, including Omicron;and fully protected vaccinees from intranasal SARS-CoV-2 challenges of either the ancestral strain or immune-evasive Beta variant. Strikingly, the vaccination of hamsters with the bivalent vaccine completely blocked the within-cage virus transmission to unvaccinated sentinels, for either the ancestral SARS-CoV-2 or Beta variant. Thus, our study provides new insights and antigen candidates for developing next-generation COVID-19 vaccines.

6.
EuropePMC; 2020.
Preprint in English | EuropePMC | ID: ppcovidwho-324292

ABSTRACT

Recently emerging SARS-CoV-2 virus has caused a global pandemic, with millions of infections and over 200, 000 deaths1. However, development of effective anti-coronavirus treatments has lagged behind. Competitive co-evolution between microbes and viruses has led to the diversification of microbe’s CRISPR/Cas defense systems against infectious viruses2,3. Among class-2 single effector systems, Cas13 is effective in combating RNA phages4. Previous studies have discovered novel Cas9 and Cas12 systems from metagenomic sequence of natural microbes5-7. Here we report the identification of two additional compact Cas13 families from natural microbes that are effective in degrading RNA viruses in mammalian cells. Using metagenomic terabase data sets, we searched for previously uncharacterized Cas13 genes proximal to the CRISPR array with a customized computational pipeline, and identified two most compact families (775 to 803 amino acids) of CRISPR-Cas ribonucleases, named hereafter as CRISPR/Cas type VI-E and VI-F. Out of seven Cas13 proteins, we found that Cas13e.1 was the smallest and could be engineered for efficient RNA interference and base editing in cultured mammalian cell lines. Moreover, Cas13e.1 has a high activity for degrading SARS-CoV-2 sequences and the genome of live influenza A virus (IAV). Together with a minimal pool of 10 crRNAs, Cas13e.1 could target over 99% of all known 3,137 coronavirus genomes for achieving antiviral defense. Overall, our results demonstrated there exist untapped bacterial defense systems in natural microbes that can function efficiently in mammalian cells, thus potentially useful for preventing viral infection in humans such as COVID-19.

8.
Sci Transl Med ; 13(606)2021 08 11.
Article in English | MEDLINE | ID: covidwho-1319371

ABSTRACT

Multiple safe and effective vaccines that elicit immune responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are necessary to respond to the ongoing coronavirus disease 2019 (COVID-19) pandemic. Here, we developed a protein subunit vaccine composed of spike ectodomain protein (StriFK) plus a nitrogen bisphosphonate-modified zinc-aluminum hybrid adjuvant (FH002C). StriFK-FH002C generated substantially higher neutralizing antibody titers in mice, hamsters, and cynomolgus monkeys than those observed in plasma isolated from COVID-19 convalescent individuals. StriFK-FH002C also induced both TH1- and TH2-polarized helper T cell responses in mice. In hamsters, StriFK-FH002C immunization protected animals against SARS-CoV-2 challenge, as shown by the absence of virus-induced weight loss, fewer symptoms of disease, and reduced lung pathology. Vaccination of hamsters with StriFK-FH002C also reduced within-cage virus transmission to unvaccinated, cohoused hamsters. In summary, StriFK-FH002C represents an effective, protein subunit-based SARS-CoV-2 vaccine candidate.


Subject(s)
COVID-19 , Animals , Antibodies, Neutralizing , Antibodies, Viral , COVID-19 Vaccines , Cricetinae , Humans , Mice , Protein Subunits , SARS-CoV-2 , Spike Glycoprotein, Coronavirus/genetics
9.
Nat Methods ; 18(5): 499-506, 2021 05.
Article in English | MEDLINE | ID: covidwho-1220210

ABSTRACT

Competitive coevolution between microbes and viruses has led to the diversification of CRISPR-Cas defense systems against infectious agents. By analyzing metagenomic terabase datasets, we identified two compact families (775 to 803 amino acids (aa)) of CRISPR-Cas ribonucleases from hypersaline samples, named Cas13X and Cas13Y. We engineered Cas13X.1 (775 aa) for RNA interference experiments in mammalian cell lines. We found Cas13X.1 could tolerate single-nucleotide mismatches in RNA recognition, facilitating prophylactic RNA virus inhibition. Moreover, a minimal RNA base editor, composed of engineered deaminase (385 aa) and truncated Cas13X.1 (445 aa), exhibited robust editing efficiency and high specificity to induce RNA base conversions. Our results suggest that there exist untapped bacterial defense systems in natural microbes that can function efficiently in mammalian cells, and thus potentially are useful for RNA-editing-based research.


Subject(s)
CRISPR-Cas Systems , RNA Editing , RNA, Bacterial , Animals , Bacterial Proteins , Cell Line , Cloning, Molecular , Databases, Nucleic Acid , Dogs , Humans , Mice , RNA Interference
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