HIV reservoir: antiviral immune responses and immune interventions for curing HIV infection

Antiretroviral therapy against human immunodeficiency virus (HIV) is effective in controlling viral replication but cannot completely eliminate HIV due to the persistence of the HIV reservoir. Innate and adaptive immune responses have been proposed to contribute to preventing HIV acquisition, controlling HIV replication and eliminating HIV-infected cells. However, the immune responses naturally induced in HIV-infected individuals rarely eradicate HIV infection, which may be caused by immune escape, an inadequate magnitude and breadth of immune responses, and immune exhaustion. Optimizing these immune responses may solve the problems of epitope escape and insufficient sustained memory responses. Moreover, immune interventions aimed at improving host immune response can reduce HIV reservoirs, which have become one focus in the development of innovative strategies to eliminate HIV reservoirs. In this review, we focus on the immune response against HIV and how antiviral immune responses affect HIV reservoirs. We also discuss the development of innovative strategies aiming to eliminate HIV reservoirs and promoting functional cure of HIV infection.

Identification and characterization of a TLR13 gene homologue from Laodelphax striatellus involved in the immune response induced by rice stripe virus

Toll-like receptors(TLRs) are the critical superfamily homologues that initiate sensing of the invasion of pathogens by the Toll pathway. As one of several intracellular nucleic acid-sensing TLRs, TLR13 is activated by an unmethylated motif present in the large ribosomal subunit of bacterial RNA. However, little attention has been paid to the function of TLR13 gene homologue from Laodelphax striatellus(designated as LsToll-13) in the immune response to rice stripe virus(RSV). Herein, LsToll-13 was cloned and characterized using RACE-PCR. Phylogenetic analysis showed that LsToll-13 was clustered with the TLR13 from six insects. Real-time PCR analysis demonstrated that the expression level of LsToll-13 was significantly reduced in L. striatellus with RSV infection compared with that in the naive strain. When the expression of LsToll-13 was significantly up-regulated at 6 h after bacterial infection, the expression of ribonucleoprotein(RNP) indicated that the RSV titer in the host insect was significantly suppressed. Upon knockdown of LsToll-13, using RNA interference(RNAi) in L. striatellus, the expression level of RNP was significantly increased with enhanced RSV accumulation, suggesting that LsToll-13 potentially protects L. striatellus from RSV infection. Taken together, our results indicated that LsToll-13 might be involved in the immune response of L. striatellus to RSV infection, and provided a new insight into further elucidating the molecular mechanisms of complex pathogen-host interactions and integrative pest management.

Harnessing immunity:Immunomodulatory therapies in COVID-19

An overly exuberant immune response,characterized by a cytokine storm and uncontrolled inflammation,has been identified as a significant driver of severe coronavirus disease 2019(COVID-19)cases.Consequently,deciphering the intricacies of immune dysregulation in COVID-19 is imperative to identify specific targets for intervention and modulation.With these delicate dynamics in mind,immunomodulatory therapies have emerged as a promising avenue for miti-gating the challenges posed by COVID-19.Precision in manipulating immune pathways presents an opportunity to alter the host response,optimizing antiviral defenses while curbing deleterious inflammation.This review article compre-hensively analyzes immunomodulatory interventions in managing COVID-19.We explore diverse approaches to mitigating the hyperactive immune response and its impact,from corticosteroids and non-steroidal drugs to targeted biologics,including anti-viral drugs,cytokine inhibitors,JAK inhibitors,convalescent plasma,monoclonal antibodies(mAbs)to severe acute respiratory syndrome coronavirus 2,cell-based therapies(i.e.,CAR T,etc.).By summarizing the current evidence,we aim to provide a clear roadmap for clinicians and researchers navigating the complex landscape of immunomodulation in COVID-19 treatment.CS Glucocorticoids are among the most widely prescribed drugs with their immune-suppressive and anti-inflammatory effect[84].The current guidelines for the treatment of COVID-19 recommend against the use of dexamethasone or other systemic CS in non-hospitalized patients in the absence of another indication[70].The RECOVERY trial demonstrates the reduced 28-d mortality among hospitalized patients with COVID-19 using dexamethasone compared to the usual standard of care,along with other investigators,such as Ahmed and Hassan[85].The benefit of dexamethasone was seen only among participants receiving either oxygen alone or invasive mechanical ventilation at randomization but not among those receiving no respiratory support at enrollment[85].In a systematic review and meta-analysis,Albuquerque et al[86]showed that in comparison to tocilizumab,baricitinib,and sarilumab are associated with high probabilities of similar mortality reductions among hospitalized COVID-19 concurrently treated with CS.As a result of the absence of SARS-CoV-2-specific antiviral medications,the effectiveness of COVID-19 treatments is reduced.Several COVID-19 therapies are now under investigation.However,the majority of them lack specificity,efficacy,and safety[87].Immunotherapy is a ground-breaking medical treatment that manipulates the immune system to fight diseases.Translational research is rapidly progressing,recognized as a significant breakthrough in 2013[88].Among the immunotherapeutic options for treating COVID-19 are Immunoglobulin,CP,antibodies,mAbs(mAbs),NK cells,T cells,TLR,cytokine therapies and immune modulators.

Characterization of Domeless receptors and the role of Bd Domeless3 in anti-symbiont-like virus defense in Bactrocera dorsalis

The Janus kinase/signal transducers and activators of transcription(JAK/STAT)signaling pathway play a pivotal role in innate immunity.Among invertebrates,Domeless receptors serve as the key upstream regulators of this pathway.In our study on Bactrocera dorsalis,we identified three cytokine receptors:BdDomeless1,BdDomeless2,and BdDomeless3.Each receptor encompasses five fibronectin-type-III-like(FN III)extracellular domains and a transmembrane domain.Furthermore,these receptors exhibit the increased responsiveness to diverse pathogenic challenges.Notably,only BdDomeless3 is upregulated during symbiont-like viral infections.Moreover,silencing BdDomeless3 enhanced the infectivity of Bactrocera dorsalis cripavirus(BdCV)and B.dorsalis picorna-like virus(BdPLV),underscoring BdDomeless3’s crucial role in antiviral defense of B.dorsalis.Following the suppression of Domeless3 expression,six antimicrobial peptide genes displayed decreased expression,potentially correlating with the rise in viral infectivity.To our knowledge,this is the first study identifying cytokine receptors associated with the JAK/STAT pathway in tephritid flies,shedding light on the immune mechanisms of B.dorsalis.

Single-nucleus transcriptomic profiling of multiple organs in a rhesus macaque model of SARS-CoV-2 infection

Infection with severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) causes diverse clinical manifestations and tissue injuries in multiple organs.However, cellular and molecular understanding of SARS-CoV-2 infection-associated pathology and immune defense features in different organs remains incomplete. Here, we profiled approximately 77 000single-nucleus transcriptomes of the lung, liver,kidney, and cerebral cortex in rhesus macaques(Macaca mulatta) infected with SARS-CoV-2 and healthy controls. Integrated analysis of the multiorgan dataset suggested that the liver harbored the strongest global transcriptional alterations. We observed prominent impairment in lung epithelial cells, especially in AT2 and ciliated cells, and evident signs of fibrosis in fibroblasts. These lung injury characteristics are similar to those reported in patients with coronavirus disease 2019(COVID-19).Furthermore, we found suppressed MHC class I/II molecular activity in the lung, inflammatory response in the liver, and activation of the kynurenine pathway,which induced the development of an immunosuppressive microenvironment. Analysis of the kidney dataset highlighted tropism of tubule cells to SARS-CoV-2, and we found membranous nephropathy(an autoimmune disease) caused by podocyte dysregulation. In addition, we identified the pathological states of astrocytes and oligodendrocytes in the cerebral cortex, providing molecular insights into COVID-19-related neurological implications. Overall, our multi-organ single-nucleus transcriptomic survey of SARS-CoV-2-infected rhesus macaques broadens our understanding of disease features and antiviral immune defects caused by SARS-CoV-2 infection,which may facilitate the development of therapeutic interventions for COVID-19.

Current research progress on the viral immune evasion mechanisms of African swine fever virus

African swine fever(ASF),caused by the ASF virus(ASFV),is an acute,severe,and highly contagious infectious disease in domestic pigs and wild boars.Domestic pigs infected with a virulent ASFV strain can have morbidity and mortality rates of up to 100%.The epidemic of ASF has caused serious economic losses to the global pig industry.Currently,there is no safe and efective vaccine or specifc drug for treating ASF.Therefore,ASFV still poses a great threat to pig factories.ASFV is a double-stranded DNA virus with a complex icosahedral multilayer structure.The ASFV genome contains 150-170 open reading frames(ORFs)that encode 150-200 proteins.Some ASFV-encoded proteins are involved in virus invasion,genome replication,DNA repair,and virion formation.Some ASFV proteins execute immunomodulatory functions by regulating the host antiviral innate immune response.Accumulating studies have shown that the immunomodulatory functions of ASFV genes are closely related to the virulence and pathogenicity of ASFV isolates.This review summarizes the research advances on ASFV immune evasion mechanisms in African swine fever patients and provides new insights for developing attenuated live vaccine candidates to prevent and control ASF.

Tom70 mediates activation of interferon regulatory factor 3 on mitochondria

Intracellular RNA viruses are sensed by receptors retinoic acid-inducible gene 1 （RIG-I）/melanoma differentiation-associated gene 5 （MDA5） that trigger the formation of MAVS signal complex on mitochondria. Consequently, this leads to the activation of TANK-binding kinase 1 （TBK1） and phosphorylation of interferon regulatory factor 3 （IRF3）, both of which constitutively associate with cytosolic chaperone Hsp90. It remains largely unknown how MAVS activates TBK1/IRF3. In this study, we identified translocases of outer membrane 70 （Tom70）, a mitochondrial import receptor, to interact with MAVS upon RNA virus infection. Ectopic expression or knockdown of Tom70 could enhance or impair IRF3-mediated gene expression, respectively. Mechanistically, the clamp domain （R192） of Tom70 interacts with the C-terminal motif （EEVD） of Hsp90, thus recruiting TBK1/IRF3 to mitochondria. Disruption of this interaction or mislocation of Tom70 sharply impairs activation of TBK1 and IRF3. Furthermore, host antiviral responses are significantly boosted or crippled in the presence or absence of Tom70. Collectively, our study characterizes Tom70 as a critical adaptor linking MAVS to TBK1/IRF3, revealing that mitochondrion is evolutionarily integrated with innate immunity.

Gene expression profiles in peripheral blood mononuclear cells of SARS patients

AIM： To investigate the role of inflammatory and anti-vira genes in the pathogenesis of SARS. METHODS： cDNA microarrays were used to screen the gene expression profiles of peripheral blood mononuclear cells （PBMCs） in two SARS patients （one in the acute severe phase and the other in the convalescent phase） and a healthy donor. In addition, real-time qualitative PCR was also performed to verify the reproducibility of the microarray results. The data were further analyzed. RESULTS： Many inflammatory and anti-viral genes were differentially expressed in SARS patients. Compared to the healthy control or the convalescent case, plenty of pro-inflammatory cytokines such as IL-1, TNF-α, IL-8, and MAPK signaling pathway were significantly upregulated in the acute severe case. However, anti-inflammatory agents such as IL-4 receptor, IL-13 receptor, IL-1Ra, and TNF-α-induced proteins 3 and 6 also increased dramatically in the acute severe case. On the contrary, a lot of IFN-stimulated genes like PKR, GBP-1 and 2, CXCL-10 and 11, and JAK/STAT signal pathway were downregulated in the acute severe case compared to the convalescent case. CONCLUSION： Gene expression in SAPS patients mirrors a host state of inflammation and anti-viral immunity at the transcription level, and understanding of gene expression profiles may make contribution to further studies of the SAPS pathogenesis.

Near-infrared light and PIF4 promote plant antiviral defense by enhancing RNA interference

The molecular mechanism underlying phototherapy and light treatment,which utilize various wavelength spectra of light,including near-infrared(NIR),to cure human and plant diseases,is obscure.Here we re-vealed that NIR light confers antiviral immunity by positively regulating PHYTOCHROME-INTERACTING FACTOR 4(PIF4)-activated RNA interference(RNAi)in plants.PIF4,a central transcription factor involved in light signaling,accumulates to high levels under NIR light in plants.PIF4 directly induces the transcription of two essential components of RNAi,RNA-DEPENDENT RNA POLYMERASE 6(RDR6)and ARGONAUTE 1(AGO1),which play important roles in resistance to both DNA and RNA viruses.Moreover,the pathogenic determinant bC1 protein,which is evolutionarily conserved and encoded by betasatellites,interacts with PIF4 and inhibits its positive regulation of RNAi by disrupting PIF4 dimerization.Thesefindings shed light on the molecular mechanism of PIF4-mediated plant defense and provide a new perspective for the explo-ration of NIR antiviral treatment.

Sex differences in SARS-CoV-2 infections,anti-viral immunity and vaccine responses

The COVID-19 pandemic has revealed sex-based differences in anti-viral responses,with a higher rate of SARS-CoV-2 infections as well as a higher rate of morbidity and mortality in men than in women.Males and females also show disparate immune responses to COVID-19 infection,which may be important contributors to lower rates of infection,disease severity and deaths in women than in men.Here,the authors review sex differences in SARS-CoV-2 infections,anti-viral immunity and vaccine responses,putting forth the importance of sex,the underappreciated variables in vaccine response and disease infectivity.

Abscisic Acid Connects Phytohormone Signaling with RNA Metabolic Pathways and Promotes an Antiviral Response that Is Evaded by a Self- Controlled RNA Virus

A complex network of cellular receptors,RNA targeting pathways,and small-molecule signaling provides robust plant immunity and tolerance to viruses.To maximize their fitness,viruses must evolve control mechanisms to balance host immune evasion and plant-damaging effects.The genus Potyvirus comprises plant viruses characterized by RNA genomes that encode large polyproteins led by the P1 protease.A P1 autoinhibitory domain controls polyprotein processing,the release of a downstream functional RNAsilencing suppressor,and viral replication.Here,we show that P1Pro,a plum pox virus clone that lacks the P1 autoinhibitory domain,triggers complex reprogramming of the host transcriptome and high levels of abscisic acid(ABA)accumulation.A meta-analysis highlighted ABA connections with host pathways known to control RNA stability,turnover,maturation,and translation.Transcriptomic changes triggered by P1Pro infection or ABA showed similarities in host RNA abundance and diversity.Genetic and hormone treatment assays showed that ABA promotes plant resistance to potyviral infection.Finally,quantitative mathematical modeling of viral replication in the presence of defense pathways supported self-control of polyprotein processing kinetics as a viral mechanism that attenuates the magnitude of the host antiviral response.Overall,our findings indicate that ABA is an active player in plant antiviral immunity,which is nonetheless evaded by a self-controlled RNA virus.

The immune tolerant phase of chronic HBV infection： new perspectives on an old concept

Chronic hepatitis B virus （HBV） infection progresses through distinct disease phases that are strongly associated with patient age. The so-called immune tolerant （IT） phase represents the classical early phase of infection; it is associated with high levels of HBV replication and lack of clinical signs of liver Inflammation. Whether this phase of HBV infection is also associated with immunological features of ＂tolerance＇ has recently been challenged. Here, we review the data that dispute this concept of immune tolerance and then propose an alternative interpretation of the immunopathological events that take place during this early phase of CHB infection.

Coronavirus membrane-associated papain-like proteases induce autophagy through interacting with Beclinl to negatively regulate antiviral innate immunity

Autophagy plays important roles in modulating viral replication and antiviral immune response. Coronavirus infection is associated with the autophagic process, however, little is known about the mechanisms of autophagy induction and its contribution to coronavirus regulation of host innate responses. Here, we show that the membrane-associated papain-like protease PLP2 （PLP2-TM） of coronaviruses acts as a novel autophagy- inducing protein. Intriguingly, PLP2-TM induces incom- plete autophagy process by increasing the accumula- tion of autophagosomes but blocking the fusion of autophagosomes with lysosomes. Furthermore, PLP2- TM interacts with the key autophagy regulators, LC3 and Beclinl, and promotes Beclinl interaction with STING, the key regulator for antiviral IFN signaling. Finally, knockdown of Beclinl partially reverses PLP2-TM＇s inhibitory effect on innate immunity which resulting in decreased coronavirus replication. These results sug- gested that coronavirus papain-like protease induces incomplete autophagy by interacting with Beclinl, which in turn modulates coronavirus replication and antiviral innate immunity.

OTUD5 promotes innate antiviral and antitumor immunity through deubiquitinating and stabilizing STING

Stimulator of interferon genes(STING)is an adaptor protein that is critical for effective innate antiviral and antitumor immunity.The activity of STING is heavily regulated by protein ubiquitination,which is fine-tuned by both E3 ubiquitin ligases and deubiquitinases.Here,we report that the deubiquitinase OTUD5 interacts with STING,cleaves its K48-linked polyubiquitin chains,and promotes its stability.Consistently,knockout of OTUD5 resulted in faster turnover of STING and subsequently impaired type I IFN signaling following cytosolic DNA stimulation.More importantly,Lyz2-Cre Otud5^(fl/Y) mice and CD11-Cre Otud5^(fl/Y) mice showed more susceptibility to herpes simplex virus type 1(HSV-1)infection and faster development of melanomas than their corresponding control littermates,indicating that OTUD5 is indispensable for STING-mediated antiviral and antitumor immunity.Our data suggest that OTUD5 is a novel checkpoint in the cGAS-STING cytosolic DNA sensing pathway.

The methyltransferase PRMT6 attenuates antiviral innate immunity by blocking TBK1–IRF3 signaling

Protein arginine methyltransferases(PRMTs)play diverse biological roles and are specifically involved in immune cell development and inflammation.However,their role in antiviral innate immunity has not been elucidated.Viral infection triggers the TBK1–IRF3 signaling pathway to stimulate the production of type-I interferon,which mediates antiviral immunity.We performed a functional screen of the nine mammalian PRMTs for regulators of IFN-βexpression and found that PRMT6 inhibits the antiviral innate immune response.Viral infection also upregulated PRMT6 protein levels.We generated PRMT6-deficient mice and found that they exhibited enhanced antiviral innate immunity.PRMT6 deficiency promoted the TBK1–IRF3 interaction and subsequently enhanced IRF3 activation and type-I interferon production.Mechanistically,viral infection enhanced the binding of PRMT6 to IRF3 and inhibited the interaction between IRF3 and TBK1;this mechanism was independent of PRMT6 methyltransferase activity.Thus,PRMT6 inhibits antiviral innate immunity by sequestering IRF3,thereby blocking TBK1-IRF3 signaling.Our work demonstrates a methyltransferase-independent role for PRMTs.It also identifies a negative regulator of the antiviral immune response,which may protect the host from the damaging effects of an overactive immune system and/or be exploited by viruses to escape immune detection.

A molecular arms race between host innate antiviral response and emerging human coronaviruses

Coronaviruses have been closely related with mankind for thousands of years. Communityacquired human coronaviruses have long been recognized to cause common cold. However,zoonotic coronaviruses are now becoming more a global concern with the discovery of highly pathogenic severe acute respiratory syndrome(SARS) and Middle East respiratory syndrome(MERS) coronaviruses causing severe respiratory diseases. Infections by these emerging human coronaviruses are characterized by less robust interferon production. Treatment of patients with recombinant interferon regimen promises beneficial outcomes, suggesting that compromised interferon expression might contribute at least partially to the severity of disease. The mechanisms by which coronaviruses evade host innate antiviral response are under intense investigations. This review focuses on the fierce arms race between host innate antiviral immunity and emerging human coronaviruses. Particularly, the host pathogen recognition receptors and the signal transduction pathways to mount an effective antiviral response against SARS and MERS coronavirus infection are discussed. On the other hand, the counter-measures evolved by SARS and MERS coronaviruses to circumvent host defense are also dissected. With a better understanding of the dynamic interaction between host and coronaviruses, it is hoped that insights on the pathogenesis of newly-identified highly pathogenic human coronaviruses and new strategies in antiviral development can be derived.

The RNA helicase DDX46 inhibits innate immunity by entrapping m^6 A-demethylated antiviral transcripts in the nucleus

With the support by the National Natural Science Foundation of China,the research team directed by Prof.Cao Xuetao(曹雪涛)at the National Key Laboratory of Medical Molecular Biology&Department of Immunology,Chinese Academy of Medical Sciences,and the National Key Laboratory of Medical Immunology,Second Military Medical University,recently reported that RNA helicase DDX46is

Regulation of antiviral innate immunity by deubiquitinase CYLD

An antiviral innate immune response involves induction of type I interferons(IFNs)and their subsequent autocrine and paracrine actions,but the underlying regulatory mechanisms are incompletely understood.Here we report that CYLD,a deubiquitinase that specifically digests lysine 63-linked ubiquitin chains,is required for antiviral host defense.Loss of CYLD renders mice considerably more susceptible to infection by vesicular stomatitis virus(VSV).Consistently,CYLD-deficient dendritic cells are more sensitive to VSV infection.This functional defect was not due to lack of type I IFN production but rather because of attenuated IFN receptor signaling.In the absence of CYLD,IFN-b is ineffective in the induction of antiviral genes and protection of cells from viral infection.These findings establish CYLD as a novel regulator of antiviral innate immunity and suggest a role for CYLD in regulating IFN receptor signaling.

RNAi can be an antiviral immunity in mammals

Subject Code:H19With the support by the National Natural Science Foundation of China,a collaborative study by the research groups led by Prof.Zhou Xi(周溪)from the State Key Laboratory of Virology,Wuhan Institute of Virology,Chinese Academy of Sciences and Prof.Qin Chengfeng(秦成峰)from Beijing Institute

TRIM35 mediates protection against influenza infection by activating TRAF3 and degrading viral PB2

Tripartite motif(TRIM)family proteins are important effectors of innate immunity against viral infections.Here we identified TRIM35 as a regulator of TRAF3 activation.Deficiency in or inhibition of TRIM35 suppressed the production of type I interferon(IFN)in response to viral infection.777m35-deficient mice were more susceptible to influenza A virus(IAV)infection than were wild-type mice.TRIM35 promoted the RIG-Imediated signaling by catalyzing Lys63-linked polyubiquitination of TRAF3 and the subsequent formation of a signaling complex with VISA and TBK1.IAV PB2 polymerase countered the innate antiviral immune response by impeding the Lys63-linked polyubiquitination and activation of TRAF3.TRIM35 mediated Lys48-linked polyubiquitination and proteasomal degradation of IAV PB2,thereby antagonizing its suppression of TRAF3 activation.Our in vitro and in vivo findings thus reveal novel roles of TRIM35,through catalyzing Lys63-or Lys48-linked polyubiquitination,in RIG-I antiviral immunity and mechanism of defense against IAV infection.