SARS-CoV-2 Omicron strain exhibits potent capabilities for immune evasion and viral entrance

Dear Editor,Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)Omicron strain(as Rnown as B.1.1.529)was identified in Botswana and South Africa in early November 2021 and was later defined as a new variant of concern(VOC)by the World Health Organization on November 26,2021.1,2 To date,the con firmed cases of Omicro n have been reported in more than 38 countries,and the number of cases appears to be rapidly in creasing.SARS-CoV-2 Omicron could give rise to the fourth wave of the COVID-19 epidemic spreading around the world,following the D614G,Beta/Gamma,and Delta VOCs.

Differential efficiencies to neutralize the novel mutants B.1.1.7 and 501Y.V2 by collected sera from convalescent COVID-19 patients and RBD nanoparticle-vaccinated rhesus macaques

New strains of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)with several dominant mutations in the spike protein have been identified recently,and crucial issues associated with the possible reinfection of recovered patients and the efficiencies of vaccines designed based on epidemic strains in early 2020.

Antibody response and cross-neutralization after Omicron BA.2 infection

Dear Editor,The Omicron(B.1.1.529)variant of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)was first identified in November 2021,in South Africa and Botswana.The first Omicron sub-lineage that emerged was BA.1,which was supplanted by BA.2 in many countries.One of the most notable features of the Omicron variant is its ability to evade neutralizing antibodies(nAbs)targeting the original virus lineages.

Enhancement of CAR-T cell activity against cholangiocarcinoma by simultaneous knockdown of six inhibitory membrane proteins

Background:Existing treatments for cholangiocarcinoma have poor efficacy.However,chimeric antigen receptor-T(CAR-T)cells are emerging as a potential therapeutic strategy.Solid tumors possess multiple adverse factors in an immunosuppressive microenvironment that impair CAR-T cell infiltration and function.This study aimed to improve the function of CAR-T cells through knock down immune checkpoints and immunosuppressive molecular receptors.Methods:We evaluated the expression of epidermal growth factor receptor(EGFR)and B7 homolog 3 protein(B7H3)antigens in cholangiocarcinoma tissues using immunohistochemistry and screened specific immune checkpoints in the cholangiocarcinoma microenvironment via flow cytometry.Subsequently,we engineered CAR-T cells targeting EGFR and B7H3 antigens.We simultaneously knocked down immune checkpoints and immunosuppressive molecular receptors in CAR-T cells by constructing two clusters of small hairpin RNAs and evaluated the engineered CAR-T cells for antitumor activity both in vitro,using tumor cell lines and cholangiocarcinoma organoid models,and in vivo,using humanized mouse models.Results:We observed high expression of EGFR and B7H3 antigens in cholangiocarcinoma tissues.EGFR-CAR-T and B7H3-CAR-T cells demonstrated specific anti-tumor activity.We found an abundance of programmed cell death protein 1(PD-1),T cell immunoglobulin and mucin domain-containing protein 3(Tim-3),and T cell immunoglobulin and ITIM domain(Tigit)on infiltrated CD8^(+)T cells in the cholangiocarcinoma microenvironment.We then decreased the expression of these 3 proteins on the surface of CAR-T cells,named PTG-scFV-CAR-T cells.Furthermore,we knocked-down the expression of transforming growth factor beta receptor(TGFβR),interleukin-10 receptor(IL-10R),and interleukin-6 receptor(IL-6R)of PTG-scFV-CAR-T cells.Those cells,named PTG-T16R-scFVCAR-T cells,potently killed tumor cells in vitro and promoted apoptosis of tumor cells in a cholangiocarcinoma organoidmodel.Finally,the PTG-T16R-scFv-CART cells showed greater inhibitory effect on tumor growth in vivo,and were superior in prolonging the survival of mice.Conclusions:Our results revealed that PTG-T16R-scFV-CAR-T cells with knockdown of sextuplet inhibitory molecules exhibited strong immunity against cholangiocarcinoma and long-term efficacy both in vitro and in vivo.This strategy provides an effective and personalized immune cell therapy against cholangiocarcinoma.

The interferon-stimulated exosomal hACE2 potently inhibits SARS-CoV-2 replication through competitively blocking the virus entry

Since the outbreak of coronavirus disease 2019(COVID-19),it has become a global pandemic.The spike(S)protein of etiologic severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)specifically recognizes human angiotensin-converting enzyme 2(hACE2)as its receptor,which is recently identified as an interferon(IFN)-stimulated gene.Here,we find that hACE2 exists on the surface of exosomes released by different cell types,and the expression of exosomal hACE2 is increased by IFNα/β treatment.In particular,exosomal hACE2 can specifically block the cell entry of SARS-CoV-2,subsequently inhibit the replication of SARS-CoV-2 in vitro and ex vivo.Our findings have indicated that IFN is able to upregulate a viral receptor on the exosomes which competitively block the virus entry,exhibiting a potential antiviral strategy.

Transcriptome analysis of CD4^(+)T cells from HIV-infected individuals receiving ART with LLV revealed novel transcription factors regulating HIV-1 promoter activity

Some HIV-infected individuals receiving ART develop low-level viremia(LLV),with a plasma viral load of 50-1000 copies/mL.Persistent low-level viremia is associated with subsequent virologic failure.The peripheral blood CD4^(+)T cell pool is a source of LLV.However,the intrinsic characteristics of CD4^(+)T cells in LLV which may contribute to low-level viremia are largely unknown.We analyzed the transcriptome profiling of peripheral blood CD4^(+)T cells from healthy controls(HC)and HIV-infected patients receiving ART with either virologic sup-pression(VS)or LLV.To identify pathways potentially responding to increasing viral loads from HC to VS and to LLV,KEGG pathways of differentially expressed genes(DEGs)were acquired by comparing VS with HC(VS-HC group)and LLV with VS(LLV-VS group),and overlapped pathways were analyzed.Characterization of DEGs in key overlapping pathways showed that CD4^(+)T cells in LLV expressed higher levels of Th1 signature transcription factors(TBX21),toll-like receptors(TLR-4,-6,-7 and-8),anti-HIV entry chemokines(CCL3 and CCL4),and anti-IL-1βfactors(ILRN and IL1R2)compared to VS.Our results also indicated activation of the NF-κB and TNF signaling pathways that could promote HIV-1 transcription.Finally,we evaluated the effects of 4 and 17 tran-scription factors that were upregulated in the VS-HC and LLV-VS groups,respectively,on HIV-1 promoter activity.Functional studies revealed that CXXC5 significantly increased,while SOX5 markedly suppressed HIV-1 tran-scription.In summary,we found that CD4^(+)T cells in LLV displayed a distinct mRNA profiling compared to that in VS,which promoted HIV-1 replication and r+eactivation of viral latency and may eventually contribute to virologic failure in patients with persistent LLV.CXXC5 and SOX5 may serve as targets for the development of latency-reversing agents.

The challenge of emerging SARS-CoV-2 mutants to vaccine development

Since the outbreak of the pandemic,waves of epidemics caused by severe acute respiratory syndrome coronavirus 2(SARS-Co V-2)variants that harbor novel mutations have never paused.Globally,it undergoes rapid mutations that involve single-nucleotide polymorphism(SNP)dominantly,whereas ORF1ab and spike genes contain the most of more than 20,000 mutation sites reported within a year(Fang et al.,2021).Mutations inside spike protein are highly concerned for their potential impact on viral transmissibility and immune evasion,as spike protein is responsible for the interaction with the viral receptor angiotensin-converting enzyme 2(ACE2)to mediate viral entry to the target cells.D614G identified in early 2020 is a globally dominant mutation(Korber et al.,2020).In late 2020,several variants were reported,which had caused continental and eventually worldwide epidemics.These notable variants include B.1.1.7 lineage(501Y.V1,Variant of Concern[VOC]202012/01),501Y.V2 variant(known as B.1.351 lineage),and P.1 lineage(also named 501Y.V3).In comparison with the D614G and D614 lineages identified in early 2020,they contain a large number of mutations within spike protein(Fig.1).

Improvement of a SARS-CoV-2 vaccine by enhancing the conjugation efficiency of the immunogen to self-assembled nanoparticles

To the Editor:Coronavirus disease 2019(COVID-19)has become a worldwide public health emergency,threatening public health and global stability[1].The development of a safe and effective vaccine is urgently needed to control the pandemic.Generally,nanoparticle(NP)vaccines can generate a more potent immune response than mRNA vaccines[2].

Significantly reduced abilities to cross-neutralize SARS-CoV-2 variants by sera from convalescent COVID-19 patients infected by Delta or early strains

The worldwide pandemic caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has resulted in more than 4.5 million deaths.Although coronaviruses have a proofreading mechanism to maintain the stability of their long genomic RNAs,mutations emerge continuously,and new variants conferring advantages rapidly become the dominant lineages[1].Strategies to fight the COVID-19 pandemic using either vaccines or nonpharmaceutical interventions have specifically been threatened by the emergence of SARS-CoV-2 variants of concern(VOCs)[2].

USP10 regulates B cell response to SARS-CoV-2 or HIV-1 nanoparticle vaccines through deubiquitinating AID

Activation-induced cytidine deaminase(AID)initiates class-switch recombination and somatic hypermutation(SHM)in antibody genes.Protein expression and activity are tightly controlled by various mechanisms.However,it remains unknown whether a signal from the extracellular environment directly affects the AID activity in the nucleus where it works.Here,we demonstrated that a deubiquitinase USP10,which specifically stabilizes nuclear AID protein,can translocate into the nucleus after AKT-mediated phosphorylation at its T674 within the NLS domain.Interestingly,the signals from BCR and TLR1/2 synergistically promoted this phosphorylation.The deficiency of USP10 in B cells significantly decreased AID protein levels,subsequently reducing neutralizing antibody production after immunization with severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)or human immunodeficiency virus type 1(HIV-1)nanoparticle vaccines.Collectively,we demonstrated that USP10 functions as an integrator for both BCR and TLR signals and directly regulates nuclear AID activity.Its manipulation could be used for the development of vaccines and adjuvants.

Infection of wild-type mice by SARS-CoV-2 B.1.351 variant indicates a possible novel cross-species transmission route

COVID-19 is identified as a zoonotic disease caused by SARS-CoV-2,which also can cross・transmit to many animals but not mice.Genetic modifications of SARS-CoV-2 or mice enable the mice susceptible to viral infection.Although neither is the natural situation,they are currently utilized to establish mouse infection models.Here we report a direct contact transmission of SARS-CoV-2 variant B.1.351 in wild-type mice.The SARS-CoV-2(B.1.351)re plicated efficiently and induced significant pathological changes in lungs and tracheas,accompanied by elevated proinflammatory cytokines in the lungs and sera.Mechanistically,the receptor-binding domain(RBD)of SARS-CoV-2(B.1.351)spike protein turned to a high binding affinity to mouse angiotensin-converting enzyme 2(mACE2),allowing the mice highly susceptible to SARS-CoV-2(B.1.351)infection.Our work suggests that SARS-CoV-2(B.1.351)expands the host range and therefore increases its transmission route without adapted mutation.As the wild house mice live with human populations quite closely,this possible transmission route could be potentially risky.In addition,because SARS-CoV-2(B.1.351)is one of the major epidemic strains and the mACE2 in laboratory-used mice is naturally expressed and regulated,the SARS-CoV-2(B.1.351)/mice could be a much convenient animal model system to study COVID-19 pathogenesis and evaluate antiviral inhibitors and vaccines.