Role In Viral Infection Research Articles

Identification of Three Novel O-Linked Glycans in the Envelope Protein of Tick-Borne Encephalitis Virus

The tick-borne encephalitis virus is a pathogen endemic to northern Europe and Asia, transmitted through bites from infected ticks. It is a member of the Flaviviridae family and possesses a positive-sense, single-stranded RNA genome encoding a polypeptide that is processed into seven non-structural and three structural proteins, including the envelope (E) protein. The glycosylation of the E protein, involving a single N-linked glycan at position N154, plays a critical role in viral infectivity and pathogenesis. Here, we dissected the entire glycosylation profile of the E protein using liquid chromatography-tandem mass spectrometry and identified three novel O-linked glycans, which were found at relatively low frequency. One of the O-linked glycans was positioned close to the highly conserved N-linked glycan site, and structural analysis suggested that it may be relevant for the function of the E 150-loop. The N154 site was found to be glycosylated with a high frequency, containing oligomannose or complex-type structures, some of which were fucosylated. An unusually high portion of oligomannose N-linked glycan structures exhibited compositions that are normally observed on proteins when they are translocated from the endoplasmic reticulum to the trans-Golgi network, suggesting disruption of the glycan processing pathway in the infected cells from which the E protein was obtained.

Stillbirth: the role of viral infections

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Severe fever with thrombocytopenia syndrome virus induces lactylation of m6A reader protein YTHDF1 to facilitate viral replication

Severe fever with thrombocytopenia syndrome virus (SFTSV), an emerging infectious pathogen with a high fatality rate, is an enveloped tripartite segmented single-stranded negative-sense RNA virus. SFTSV infection is characterized by suppressed host innate immunity, proinflammatory cytokine storm, failure of B-cell immunity, and robust viral replication. m6A modification has been shown to play a role in viral infections. However, interactions between m6A modification and SFTSV infection remain poorly understood. Through MeRIP-seq, we identify m6A modifications on SFTSV RNA. We show that YTHDF1 can bind to m6A modification sites on SFTSV, decreasing the stability of SFTSV RNA and reducing the translation efficiency of SFTSV proteins. The SFTSV virulence factor NSs increases lactylation of YTHDF1 and YTHDF1 degradation, thus facilitating SFTSV replication. Our findings indicate that the SFTSV protein NSs induce lactylation to inhibit YTHDF1 as a countermeasure to host’s YTHDF1-mediated degradation of m6A-marked viral mRNAs.

Tissue specific innate immune responses impact viral infection in Drosophila.

All organisms sense and respond to pathogenic challenge. Tissue-specific responses are required to combat pathogens infecting distinct cell types. Cyclic dinucleotides (CDNs) are produced endogenously downstream of pathogen recognition or by pathogens themselves which bind to STING to activate NF-kB-dependent antimicrobial gene expression programs. It remains unknown whether there are distinct immune responses to CDNs in Drosophila tissues. Here, we investigated tissue specific CDN-STING responses and uncovered differences in gene-induction patterns across tissues that play important roles in viral infections. Using tissue-and cell-specific genetic studies we found that dSTING in the fat body controls CDN-induced expression of dSTING-regulated gene 1 (Srg1) but not dSTING-regulated gene 2 (Srg2) or 3 (Srg3). In contrast, the gastrointestinal tract largely controls expression of Srg2 and Srg3. We found that Srg3 is antiviral against the natural fly pathogen Drosophila C virus and the human arthropod-borne Rift Valley Fever virus (RVFV), but not other arthropod-borne viruses including Sindbis virus and dengue virus. Furthermore, we found that Srg3 has an important role in controlling RVFV infection of the ovary which has important implications in understanding vertical transmission of viruses and RVFV in mosquitoes. Overall, our study underscores the importance of tissue-specific responses in antiviral immunity and highlights the complex tissue regulation of the CDN-STING pathway.

Extracellular vesicles containing SARS-CoV-2 proteins are associated with multi-organ dysfunction and worse outcomes in patients with severe COVID-19.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19) and has been related to more than 7 million deaths globally since 2019. The association of high levels of IL-6 with severe cases led to the early evaluation of the anti-IL6 inhibitor tocilizumab as a potential treatment, which unfortunately failed to improve survival in many trials. Moreover, little is known about the development of COVID-19 sequelae, and biomarkers are needed to understand and anticipate these processes. Because extracellular vesicles (EVs) play an important role in viral infection and immune response, they could potentially serve as predictive and prognostic biomarkers. We isolated EVs from 39 patients with severe COVID-19, from which 29 received tocilizumab and 10 were considered controls. Blood samples, which were collected at hospitalisation before treatment, at Day 7, and Day 15 during follow-up, were assessed by immunoblot for longitudinal expression of spike (S) and nucleocapsid (N) proteins. Dynamic expression was calculated and compared with clinicopathological and experimental variables. Expression of EV S was validated by immunogold and imaging flow-cytometry, revealing an enrichment in CD9+ EVs. As a result, decreasing expression of EV viral proteins was observed in patients treated with tocilizumab. Moreover, higher increase in EV S was observed in patients with lower antibody response, hyperfibrinogenemia, lower respiratory function, higher blood pressure and shorter outcomes. These findings lay the foundation for future studies characterizing the role of EVs in multiorgan assessment and identifying biomarkers in patients with severe COVID-19 and possible long COVID.

Characterization of bi-segmented and tri-segmented recombinant Pichinde virus particles.

Mammarenaviruses include several highly virulent pathogens (e.g., Lassa virus) capable of causing severe hemorrhagic fever diseases for which there are no approved vaccines and limited treatment options. Mammarenaviruses are enveloped, bi-segmented ambisense RNA viruses. There is limited knowledge about cellular proteins incorporated into progeny virion particles and their potential biological roles in viral infection. Pichinde virus (PICV) is a prototypic arenavirus used to characterize mammarenavirus replication and pathogenesis. We have developed a recombinant PICV with a tri-segmented RNA genome as a viral vector platform. Whether the tri-segmented virion differs from the wild-type bi-segmented one in viral particle morphology and protein composition has not been addressed. In this study, recombinant PICV (rPICV) virions with a bi-segmented (rP18bi) and a tri-segmented (rP18tri) genome were purified by density-gradient ultracentrifugation and analyzed by cryo-electron microscopy and mass spectrometry. Both virion types are pleomorphic with spherical morphology and have no significant difference in size despite rP18tri having denser particles. Both virion types also contain similar sets of cellular proteins. Among the highly enriched virion-associated cellular proteins are components of the endosomal sorting complex required for transport pathway and vesicle trafficking, such as ALIX, Tsg101, VPS, CHMP, and Ras-associated binding proteins, which have known functions in virus assembly and budding. Other enriched cellular proteins include peripheral and transmembrane proteins, chaperone proteins, and ribosomal proteins; their biological roles in viral infection warrant further analysis. Our study provides important insights into mammarenavirus particle formation and aids in the future development of viral vectors and antiviral discovery.IMPORTANCEMammarenaviruses, such as Lassa virus, are enveloped RNA viruses that can cause severe hemorrhagic fever diseases (Lassa fever) with no approved vaccine and limited therapeutic options. Cellular proteins incorporated into progeny virion particles and their biological roles in mammarenavirus infection have not been well characterized. Pichinde virus (PICV) is a prototypic mammarenavirus used as a surrogate model for Lassa fever. We used cryo-electron microscopy and proteomic analysis to characterize the morphology and protein contents of the purified PICV particles that package either two (bi-segmented) or three (tri-segmented) genomic RNA segments. Our results demonstrate a similar virion morphology but different particle density for the bi- and tri-segmented viral particles and reveal major virion-associated cellular proteins. This study provides important insights into the virus-host interactions that can be used for antiviral development and optimizing arenavirus-based vaccine vectors.

Two plant membrane-shaping reticulon-like proteins play contrasting complex roles in turnip mosaic virus infection.

Positive-sense RNA viruses remodel cellular cytoplasmic membranes as the membranous sources for the formation of viral replication organelles (VROs) for viral genome replication. In plants, they traffic through plasmodesmata (PD), plasma membrane-lined pores enabling cytoplasmic connections between cells for intercellular movement and systemic infection. In this study, we employed turnip mosaic virus (TuMV), a plant RNA virus to investigate the involvement of RTNLB3 and RTNLB6, two ER (endoplasmic reticulum) membrane-bending, PD-located reticulon-like (RTNL) non-metazoan group B proteins (RTNLBs) in viral infection. We show that RTNLB3 interacts with TuMV 6K2 integral membrane protein and RTNLB6 binds to TuMV coat protein (CP). Knockdown of RTNLB3 promoted viral infection, whereas downregulation of RTNLB6 restricted viral infection, suggesting that these two RTNLs play contrasting roles in TuMV infection. We further demonstrate that RTNLB3 targets the α-helix motif 42LRKSM46 of 6K2 to interrupt 6K2 self-interactions and compromise 6K2-induced VRO formation. Moreover, overexpression of AtRTNLB3 apparently promoted the selective degradation of the ER and ER-associated protein calnexin, but not 6K2. Intriguingly, mutation of the α-helix motif of 6K2 that is required for induction of VROs severely affected 6K2 stability and abolished TuMV infection. Thus, RTNLB3 attenuates TuMV replication, probably through the suppression of 6K2 function. We also show that RTNLB6 promotes viral intercellular movement but does not affect viral replication. Therefore, the proviral role of RTNLB6 is probably by enhancing viral cell-to-cell trafficking. Taken together, our data demonstrate that RTNL family proteins may play diverse complex, even opposite, roles in viral infection in plants.

Functional analyses of dopamine receptors involved in virus transmission and reproduction in the small brown planthopper Laodelphax striatellus

Dopamine (DA) is the most abundant biogenic amine present in the insect central nervous system, and regulates multiple functions in physiology and behaviors through dopamine receptors (DARs). The small brown planthopper Laodelphax striatellus is an important agricultural pest and causes serious damage by transmitting diverse plant viruses, such as rice stripe virus (RSV). However, DARs have not yet been molecularly characterized in planthoppers, and their roles in virus infection and transmission remain largely unknown in insect vectors. In this study, we cloned four LsDARs (LsDOP1, LsDOP2, LsDOP3 and LsDopEcR) from L.striatellus. LsDARs share considerable sequence identity with their orthologous DARs, and cluster nicely with their corresponding receptor groups. The transcript levels of LsDARs varied in different developmental stages and adult tissues, with the highest expressions in the egg stage and in the brain. The expression levels of LsDARs were significantly higher in RSV-viruliferous L.striatellus. Knockdown of LsDOP2 and LsDOP3 significantly downregulated the expressions of viral genes of capsid protein (CP) and RNA3 segment (RNA3), while LsDOP1 knockdown upregulated their expressions. Silencing LsDopEcR upregulated and then downregulated CP and RNA3 expressions. Moreover, LsDOP2 and LsDOP3 knockdown significantly decreased the vertical transmission rates of RSV. Meanwhile, DA injection promoted RSV transmission and accumulation. We further demonstrated that silencing of LsDARs significantly altered the expressions of vitellogenin (LsVg) and Vg receptor (LsVgR). Furthermore, the reproduction performance of L.striatellus was reduced by LsDOP2 and LsDOP3 knockdown, but increased by LsDopEcR knockdown, and not affected by LsDOP1 silencing. These results provide critical information concerning the roles of DARs in virus transmission and reproduction in L.striatellus, and open the way for the development of innovative strategies for planthopper control.

The Role of Viral Infections in the Development and Progression of COPD.

Chronic obstructive pulmonary disease (COPD) is a common chronic disease seen in smokers associated with poor functional status, quality of life, and morbidity and mortality from acute worsening of chronic symptoms, also called exacerbations. As a disease, the risk factors for COPD are well defined; however, there is room for innovation in identifying underlying biological processes, or "endotypes," that lead to the emergence and/or progression of COPD. Identifying endotypes allows for more thorough understanding of the disease, may reveal the means of disease prevention, and may be leveraged in novel therapeutic approaches. In this review, we discuss the interface of viral infections with both cellular and epithelial immunity as a potential endotype of interest in COPD.

The composition and unrevealed immune role of non-RLR DExD/H box RNA helicases in fish

The large superfamily of DExD/H box RNA helicases are involved in various life processes, such as RNA metabolism, transcriptional regulation, translation, tumorigenesis, cell cycle, and viral infection, and RIG-like receptors (RLRs) in the superfamily have been confirmed with crucial roles in viral infection by recognizing viral RNA. In this review, non-RLR DExD/H box RNA helicases were possibly summarized in relation with their composition and antiviral immune responses in teleost, with at least 52 genes in the helicase subfamily. Compared with mammals, most DExD/H box RNA helicases in teleost are conservatively present, but some are present in a fish-specific gene duplication manner or have been lost in evolution, which may imply the obvious compositional difference in fish. The comparison in innate immune roles of mammalian and teleost DExD/H box RNA helicases indicated that DDX3a, DDX3b, DHX9, DDX41, DDX43 are functional positively in anti-viral/bacterial immunity in fish, while DDX1, DDX3a, DDX5, DDX19, DDX23 negatively in the immunity. In the future, the composition, possible immune recognition, signalling and interaction with other immune pathways, as well as other biological functions are all of significant importance for research, which may contribute to the development of disease prevention and control strategies in aquaculture.

Precise location of three novel linear epitopes using the generated monoclonal antibodies against the Knob domain of FAdV-4 surface structural protein, fiber1.

Fowl adenovirus serotype 4 (FAdV-4) is the main pathogen of hepatitis-hydropericardium syndrome (HHS), which brings huge economic losses to the poultry industry worldwide. Fiber-1 protein plays an important role in viral infection and pathogenesis by binding directly to cellular receptors of FAdV-4. In particular, the knob domain of fiber-1 protein has been reported to induce the production of neutralizing antibodies and arouse protection against the lethal challenge of chickens with FAdV-4. The fiber-1 knob (F1K) protein was expressed in a prokaryotic expression system and purified using Ni-NTA affinity chromatography. Monoclonal antibodies (mAbs) against FAdV-4 were generated by immunizing BALB/c mice with the purified F1K protein and screened using a series of immunoassays. Potential B cell epitopes on the knob domain of fiber-1 protein were mapped using enzyme-linked immunosorbent assay (ELISA) and dot-blot. Precious location and crucial amino acids of the identified epitopes were determined using peptide array scanning, truncations and alanine-scanning mutagenesis. The epitopes were analyzed and visualized on the knob trimer of FAdV-4 fiber-1 protein using the PyMOL software. Water-soluble recombinant fiber-1 knob (F1K) protein was obtained with the assistance of chaperone. Four monoclonal antibodies (5C10, 6F8, 8D8, and 8E8) against FAdV-4 were generated and characterized using indirect ELISA, Western blot, dot-blot, and immunological fluorescence assay (IFA). The mAbs were demonstrated to be from different hybridoma cell lines based on the sequences of the variable regions. Meanwhile, three distinct novel linear B-cell epitopes (319SDVGYLGLPPH329, 328PHTRDNWYV336, and 407VTTGPIPFSYQ417) on the knob domain of fiber-1 protein were identified and the key amino acid residues in the epitopes were determined. Structural analysis showed that the two adjacent epitopes 319SDVGYLGLPPH329 and 328PHTRDNWYV336 were exposed on the surface of the fiber-1 knob trimer, whereas the epitope 407VTTGPIPFSYQ417 was located inside of the spatial structure. This was the first identification of B-cell epitopes on the knob domain of fiber-1 protein and these findings provided a sound basis for the development of subunit vaccines, therapeutics, and diagnostic methods to control FAdV infections.

Protective role of cytosolic prion protein against virus infection in prion-infected cells.

Cytosolic PrP has been detected in prion-infected cells and suggested to be involved in the neurotoxicity of prions. Here, we also detected cytosolic PrP in prion-infected cells. We further found that the nuclear translocation of NF-κB was disturbed in prion-infected cells and that the N-terminal potential nuclear translocation signal of PrP expressed in the cytosol disturbed the nuclear translocation of NF-κB. Thus, the N-terminal nuclear translocation signal of cytosolic PrP might play a role in prion neurotoxicity. Prion-like protein aggregates in other protein misfolding disorders, including Alzheimer's disease were reported to play a protective role against various environmental stimuli. We here showed that prion-infected cells were partially resistant to IAV/WSN infection due to the cytosolic PrP-mediated disturbance of the nuclear translocation of NF-κB, which consequently activated NLRP3 inflammasomes after IAV/WSN infection. It is thus possible that prions could also play a protective role in viral infections.

The Role of Viruses in the Pathogenesis of Immune-Mediated Gastro-Intestinal Diseases.

Immune-mediated gastrointestinal (GI) diseases, including achalasia, celiac disease, and inflammatory bowel diseases, pose significant challenges in diagnosis and management due to their complex etiology and diverse clinical manifestations. While genetic predispositions and environmental factors have been extensively studied in the context of these conditions, the role of viral infections and virome dysbiosis remains a subject of growing interest. This review aims to elucidate the involvement of viral infections in the pathogenesis of immune-mediated GI diseases, focusing on achalasia and celiac disease, as well as the virome dysbiosis in IBD. Recent evidence suggests that viral pathogens, ranging from common respiratory viruses to enteroviruses and herpesviruses, may trigger or exacerbate achalasia and celiac disease by disrupting immune homeostasis in the GI tract. Furthermore, alterations in the microbiota and, specifically, in the virome composition and viral-host interactions have been implicated in perpetuating chronic intestinal inflammation in IBD. By synthesizing current knowledge on viral contributions to immune-mediated GI diseases, this review aims to provide insights into the complex interplay between viral infections, host genetics, and virome dysbiosis, shedding light on novel therapeutic strategies aimed at mitigating the burden of these debilitating conditions on patients' health and quality of life.

The Central Conserved Peptides of Respiratory Syncytial Virus G Protein Enhance the Immune Response to the RSV F Protein in an Adenovirus Vector Vaccine Candidate.

Respiratory syncytial virus (RSV) is a serious human respiratory pathogen that commonly affects children, older adults, and immunocompromised individuals. At present, the design of licensed vaccines focuses on the incorporation of the pre-fusion protein (PreF protein) of RSV, as this protein has the ability to induce antibodies that offer a high level of protection. Moreover, the G protein contains the CX3C motif that binds the chemokine receptor CX3CR1 in respiratory epithelial cells, which plays an essential role in viral infection. Therefore, incorporating the G antigen into vaccine design may prove more advantageous for RSV prevention. In this study, we developed a human adenoviral vector-based RSV vaccine containing highly neutralizing immunogens, a modified full-length PreF protein fused with the central conserved peptides of the G protein (Gcc) from both RSV subgroups trimerized via a C-terminal foldon, and evaluated its immune response in mice through intranasal (i.n.) immunization. Our results showed that immunization with Ad5-PreF-Qa-Gcc elicited a balanced Th1/Th2 immune response and robust mucosal immunity with higher neutralizing antibody titers against RSV Long and RSV B1. Importantly, immunization with Ad5-PreF-Qa-Gcc enhanced CD4+ CD25+ FoxP3+ Treg cell response and protected the mice against RSV infection. Our data demonstrate that the combination of Gcc and the PreF antigen is a viable strategy for developing effective RSV vaccines.

Research progress on the mechanism of exosome-mediated virus infection.

Exosomes are extracelluar vesicles that facilitate intercellular communication and are pivotal in post-transcriptional regulation within cellular gene regulatory networks, impacting pathogen dynamics. These vesicles serve as crucial regulators of immune responses, mediating cellular interactions and enabling the introduction of viral pathogenic regions into host cells. Exosomes released from virus-infected cells harbor diverse microRNAs (miRNAs), which can be transferred to recipient cells, thereby modulating virus infection. This transfer is a critical element in the molecular interplay mediated by exosomes. Additionally, the endosomal sorting complex required for transport (ESCRT) within exosomes plays a vital role in virus infection, with ESCRT components binding to viral proteins to facilitate virus budding. This review elucidates the roles of exosomes and their constituents in the invasion of host cells by viruses, aiming to shed new light on the regulation of viral transmission via exosomes.

Viral miRNA delivered by exosomes from Marek's disease virus-transformed lymphoma cell line exerts regulatory function in internalized primary chicken embryo fibroblast cells

In the past decade, research has demonstrated that viral miRNAs encoded by a number of viral genomes, particularly by most of the herpesvirus including Marek's disease virus (MDV), play important regulatory roles in viral infection, replication, and regulation of tumorigenesis. As macrovesicles in cells, exosomes can deliver viral miRNAs and exert gene regulatory functions. Whether the exosomes play a role in the replication, pathogenesis/tumorigenesis of avian herpesviruses such as oncogenic Marek's disease virus (MDV) remains unclear. Herein we extracted and identified the exosomes from MDV-transformed T cell line MSB-1 and demonstrated high abundance of MDV-1 miRNA expression. Using dual luciferase-based reporter assay, we also demonstrated that the exosomes derived from MSB-1 can deliver functional miRNA successfully into primary chicken embryo fibroblasts. These findings provide new insights into the role of exosomes and the mechanisms of how virus-encoded miRNA function in MDV latency/activation switching, viral replication, pathogenesis and/or tumorigenesis.

C-Terminal Binding Protein: Regulator between Viral Infection and Tumorigenesis.

C-terminal binding protein (CtBP), a transcriptional co-repressor, significantly influences cellular signaling, impacting various biological processes including cell proliferation, differentiation, apoptosis, and immune responses. The CtBP family comprises two highly conserved proteins, CtBP1 and CtBP2, which have been shown to play critical roles in both tumorigenesis and the regulation of viral infections. Elevated CtBP expression is noted in various tumor tissues, promoting tumorigenesis, invasiveness, and metastasis through multiple pathways. Additionally, CtBP's role in viral infections varies, exhibiting differing or even opposing effects depending on the virus. This review synthesizes the advances in CtBP's function research in viral infections and virus-associated tumorigenesis, offering new insights into potential antiviral and anticancer strategies.

Nucleic Acid Sensor-Mediated PANoptosis in Viral Infection.

Innate immunity, the first line of host defense against viral infections, recognizes viral components through different pattern-recognition receptors. Nucleic acids derived from viruses are mainly recognized by Toll-like receptors, nucleotide-binding domain leucine-rich repeat-containing receptors, absent in melanoma 2-like receptors, and cytosolic DNA sensors (e.g., Z-DNA-binding protein 1 and cyclic GMP-AMP synthase). Different types of nucleic acid sensors can recognize specific viruses due to their unique structures. PANoptosis is a unique form of inflammatory cell death pathway that is triggered by innate immune sensors and driven by caspases and receptor-interacting serine/threonine kinases through PANoptosome complexes. Nucleic acid sensors (e.g., Z-DNA-binding protein 1 and absent in melanoma 2) not only detect viruses, but also mediate PANoptosis through providing scaffold for the assembly of PANoptosomes. This review summarizes the structures of different nucleic acid sensors, discusses their roles in viral infections by driving PANoptosis, and highlights the crosstalk between different nucleic acid sensors. It also underscores the promising prospect of manipulating nucleic acid sensors as a therapeutic approach for viral infections.

Increased expression of miR-320b in blood plasma of patients in response to SARS-CoV-2 infection

Coronavirus disease 2019 (COVID-19) is caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Recent research has demonstrated how epigenetic mechanisms regulate the host–virus interactions in COVID-19. It has also shown that microRNAs (miRNAs) are one of the three fundamental mechanisms of the epigenetic regulation of gene expression and play an important role in viral infections. A pilot study published by our research group identified, through next-generation sequencing (NGS), that miR-4433b-5p, miR-320b, and miR-16–2-3p are differentially expressed between patients with COVID-19 and controls. Thus, the objectives of this study were to validate the expression of these miRNAs using quantitative real-time polymerase chain reaction (qRT-PCR) and to perform in silico analyses. Patients with COVID-19 (n = 90) and healthy volunteers (n = 40) were recruited. MiRNAs were extracted from plasma samples and validated using qRT-PCR. In addition, in silico analyses were performed using mirPath v.3 software. MiR-320b was the only miRNA upregulated in the case group com-pared to the control group. The in silico analyses indicated the role of miR-320b in the regulation of the KITLG gene and consequently in the inflammatory process. This study confirmed that miR-320b can distinguish patients with COVID-19 from control participants; however, further research is needed to determine whether this miRNA can be used as a target or a biomarker.

Intermediate open state of CD4-bound HIV-1 env heterotrimers in asia CRFs

The HIV-1 envelope glycoprotein (Env) plays crucial role in viral infection by facilitating viral attachment to host cells and inducing fusion of the virus with the host cell membrane. This fusion allows the HIV-1 viral genome to enter the target cell then triggering various stages of the viral life cycle. The native Env directly interacts with the main receptor CD4 and the co-receptor (CCR5 or CXCR4) in human cell membrane then induces membrane fusion. The elucidation of the structure of Env with CD4 and co-receptors in different HIV-1 subtypes is essential for the understanding of the mechanism of virus entry. Here we report the Cryo-EM structure of the CD4-bound HIV-1 heterotrimeric Env from Asia prevalent CRF07_BC CH119 strain. In this structure, the binding of three CD4 molecules with Env induced extensively conformational changes in gp120, resulting in the transformation of the Env from close state to intermediate open state. Additionally, the conformational shift of V1/V2 loops of the heterotrimeric Env allosterically expose the V3 loop and promoting the further interactions with co-receptor CCR5 or CXCR4. These findings not only illustrate the structural complexity and plasticity of HIV-1 Env but also give new insights how the biological trimeric Env initialize the immune recognition and membrane fusion.