Identification of fangchinoline as a broad-spectrum enterovirus inhibitor through reporter virus based high-content screening.

Hand, foot, and mouth disease (HFMD) is a common pediatric illness mainly caused by enteroviruses, which are important human pathogens. Currently, there are no available antiviral agents for the therapy of enterovirus infection. In this study, an excellent high-content antiviral screening system utilizing the EV-A71-eGFP reporter virus was developed. Using this screening system, we screened a drug library containing 1042 natural compounds to identify potential EV-A71 inhibitors. Fangchinoline (FAN), a bis-benzylisoquinoline alkaloid, exhibits potential inhibitory effects against various enteroviruses that cause HFMD, such as EV-A71, CV-A10, CV-B3 and CV-A16. Further investigations revealed that FAN targets the early stage of the enterovirus life cycle. Through the selection of FAN-resistant EV-A71 viruses, we demonstrated that the VP1 protein could be a potential target of FAN, as two mutations in VP1 (E145G and V258I) resulted in viral resistance to FAN. Our research suggests that FAN is an efficient inhibitor of EV-A71 and has the potential to be a broad-spectrum antiviral drug against human enteroviruses.

A Chimeric Classical Insect-Specific Flavivirus Provides Complete Protection Against West Nile Virus Lethal Challenge in Mice.

West Nile virus (WNV), an arthropod-borne flavivirus, can cause severe symptoms, including encephalitis, and death, posing a threat to public health and the economy. However, there is still no approved treatment or vaccine available for humans. Here, we developed a novel vaccine platform based on a classical insect-specific flavivirus (cISF) YN15-283-02, which was derived from Culicoides. The cISF-WNV chimera was constructed by replacing prME structural genes of the infectious YN15-283-02 cDNA clone with those of WNV and successfully rescued in Aedes albopictus cells. cISF-WNV was nonreplicable in vertebrate cells and nonpathogenic in type I interferon receptor (IFNAR)-deficient mice. A single-dose immunization of cISF-WNV elicited considerable Th1-biased antibody responses in C57BL/6 mice, which was sufficient to offer complete protection against lethal WNV challenge with no symptoms. Our studies demonstrated the potential of the insect-specific cISF-WNV as a prophylactic vaccine candidate to prevent infection with WNV.

Mechanism for Improved Curie Temperature and Magnetic Entropy Change in Sm-Doped Fe88Zr8B4 Amorphous Alloys.

In the present work, Fe88Zr8-xSmxB4 (x = 2, 4) amorphous alloys (AAs) were successfully synthesized into the shape of 40-micrometer-thick ribbons and their magnetic properties were measured. The Fe88Zr8-xSmxB4 (x = 2, 4) AAs exhibited a rather high maximum magnetic entropy change (-ΔSmpeak): ~3.53 J/(K × kg) near 317 K for x = 2 and ~3.79 J/(K × kg) near 348 K for x = 4 under 5 T. The effects of a Sm substitution for Zr on the Curie temperature (Tc) and -ΔSmpeak were studied and compared to those of Nd and Pr substitutions, for the purpose of revealing the mechanism involved in more detail.

Newcastle Disease Virus (NDV)-based vaccine candidate against SARS-CoV-2 Omicron by intranasal immunization.

Despite global vaccination efforts, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to evolve and spread globally. Currently, the development of affordable vaccine against Omicron variant of concern (VOC) is necessary. Here, we assessed the safety and immunogenicity of a SARS-CoV-2 vaccine consisting of a live Newcastle disease virus vector expressing the spike (S) protein of Omicron BA.1 administrated intranasally (IN) or intramuscularly (IM) in Golden Syrian hamster model. Immunogenicity studies showed that the prime-boost regimen elicited high antibody titers and the modified S antigen (Sm-F) could induce robust antibody response in low dosage immunization through IN route. Sera of the immunized hamsters provided effective cross-neutralizing activity against different Omicron variants, the prototype and delta strains of SARS-CoV-2. Moreover, the vaccine could provide complete immunoprotection in hamsters against the Omicron BA.1 challenge by either intranasal or intramuscular immunization. Overall, our study provides an alternative nasal vaccine against the SARS-CoV-2 Omicron variants.

PF-D-Trimer, a protective SARS-CoV-2 subunit vaccine: immunogenicity and application.

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has had and continues to have a significant impact on global public health. One of the characteristics of SARS-CoV-2 is a surface homotrimeric spike protein, which is primarily responsible for the host immune response upon infection. Here we present the preclinical studies of a broadly protective SARS-CoV-2 subunit vaccine developed from our trimer domain platform using the Delta spike protein, from antigen design through purification, vaccine evaluation and manufacturability. The pre-fusion trimerized Delta spike protein, PF-D-Trimer, was highly expressed in Chinese hamster ovary (CHO) cells, purified by a rapid one-step anti-Trimer Domain monoclonal antibody immunoaffinity process and prepared as a vaccine formulation with an adjuvant. Immunogenicity studies have shown that this vaccine candidate induces robust immune responses in mouse, rat and Syrian hamster models. It also protects K18-hACE2 transgenic mice in a homologous viral challenge. Neutralizing antibodies induced by this vaccine show cross-reactivity against the ancestral WA1, Delta and several Omicrons, including BA.5.2. The formulated PF-D Trimer is stable for up to six months without refrigeration. The Trimer Domain platform was proven to be a key technology in the rapid production of PF-D-Trimer vaccine and may be crucial to accelerate the development and accessibility of updated versions of SARS-CoV-2 vaccines.

Intranasal delivery of replicating mRNA encoding hACE2-targeting antibody against SARS-CoV-2 Omicron infection in the hamster.

The Omicron variant is sweeping the world, which displays striking immune escape potential through mutations at key antigenic sites on the spike protein, making broad-spectrum SARS-CoV-2 prevention or therapeutical strategies urgently needed. Previously, we have reported a hACE2-targeting neutralizing antibody 3E8, which could efficiently block both prototype SARS-CoV-2 and Delta variant infections in prophylactic mouse models, having the potential of broad-spectrum to prevent SARS-CoV-2. However, preparation of monoclonal neutralizing antibodies is severely limited by the time-consuming process and the relative high cost. Here, we utilized a modified VEEV replicon with two subgenomic (sg) promoters engineered to express the light and heavy chains of the 3E8 mAb. The feasibility and protective efficacy of replicating mRNA encoding 3E8 against Omicron infection in the hamster were demonstrated through the lung targeting delivery with the help of VEEV-VRP. Overall, we developed a safe and cost-effective platform of broad-spectrum to prevent SARS-CoV-2 infection.

Attenuated WNV-poly(A) exerts a broad-spectrum oncolytic effect by selective virus replication and CD8+ T cell-dependent immune response.

As an emerging tumor therapy, ideal oncolytic viruses preferentially replicate in malignant cells, reverse the immunosuppressive tumor microenvironment, and eventually can be eliminated by the patient. It is of great significance for cancer treatment to discover new excellent oncolytic viruses. Here, we found that WNV live attenuated vaccine WNV-poly(A) could be developed as a novel ideal oncolytic agent against several types of cancers. Mechanistically, due to its high sensitivity to type Ι interferon (IFN-Ι), WNV-poly(A) could specifically kill tumor cells rather than normal cells. At the same time, WNV-poly(A) could activate Dendritic cells (DCs) and trigger tumor antigen specific response mediated by CD8 + T cell, which contributed to inhibit the propagation of original and distal tumor cells. Like intratumoral injection, intravenous injection with WNV-poly(A) also markedly delays Huh7 hepatic carcinoma (HCC) transplanted tumor progression. Most importantly, in addition to an array of mouse xenograft tumor models, WNV-poly(A) also has a significant inhibitory effect on many different types of patient-derived tumor tissues and HCC patient-derived xenograft (PDX) tumor models. Our studies reveal that WNV-poly(A) is a potent and excellent oncolytic agent against many types of tumors and may have a role in metastatic and recurrent tumors.

Berbamine hydrochloride potently inhibits SARS-CoV-2 infection by blocking S protein-mediated membrane fusion.

COVID-19 caused by SARS-CoV-2 has posed a significant threat to global public health since its outbreak in late 2019. Although there are a few drugs approved for clinical treatment to combat SARS-CoV-2 infection currently, the severity of the ongoing global pandemic still urges the efforts to discover new antiviral compounds. As the viral spike (S) protein plays a key role in mediating virus entry, it becomes a potential target for the design of antiviral drugs against COVID-19. Here, we tested the antiviral activity of berbamine hydrochloride, a bis-benzylisoquinoline alkaloid, against SARS-CoV-2 infection. We found that berbamine hydrochloride could efficiently inhibit SARS-CoV-2 infection in different cell lines. Further experiments showed berbamine hydrochloride inhibits SARS-CoV-2 infection by targeting the viral entry into host cells. Moreover, berbamine hydrochloride and other bis-benzylisoquinoline alkaloids could potently inhibit S-mediated cell-cell fusion. Furthermore, molecular docking results implied that the berbamine hydrochloride could bind to the post fusion core of SARS-CoV-2 S2 subunit. Therefore, berbamine hydrochloride may represent a potential efficient antiviral agent against SARS-CoV-2 infection.

High-Titer Self-Propagating Capsidless Chikungunya Virus Generated in Vero Cells as a Strategy for Alphavirus Vaccine Development.

In our previous study, we found that a new type of Chikungunya virus particle with a complete capsid deletion (ΔC-CHIKV) is still infectious in BHK-21 cells and demonstrated its potential as a live attenuated vaccine candidate. However, the low yield as well as the disability to propagate in vaccine production cell line Vero of ΔC-CHIKV are not practical for commercial vaccine development. In this study, we not only achieved the successful propagation of the viral particle in Vero cells, but significantly improved its yield through construction of a chimeric VEEV-ΔC-CHIKV and extensive passage in Vero cells. Mechanistically, high production of VEEV-ΔC-CHIKV is due to the improvement of viral RNA packaging efficiency conferred by adaptive mutations, especially those in envelope proteins. Similar to ΔC-CHIKV, the passaged VEEV-ΔC-CHIKV is safe, immunogenic, and efficacious, which protects mice from CHIKV challenge after only one shot of immunization. Our study demonstrates that the utilization of infectious capsidless viral particle of CHIKV as a vaccine candidate is a practical strategy for the development of alphavirus vaccine. IMPORTANCE Chikungunya virus (CHIKV) is one of important emerging alphaviruses. Currently, there are no licensed vaccines against CHIKV infection. We have previously found a new type of Chikungunya virus particle with a complete capsid deletion (ΔC-CHIKV) as a live attenuated vaccine candidate that is not suitable for commercial vaccine development with the low viral titer production. In this study, we significantly improved its production through construction of a chimeric VEEV-ΔC-CHIKV. Our results proved the utilization of infectious capsidless viral particle of CHIKV as a safe and practical vaccine candidate.

A new screening system for entry inhibitors based on cell-to-cell transmitted syncytia formation mediated by self-propagating hybrid VEEV-SARS-CoV-2 replicon.

The extremely high transmission rate of SARS-CoV-2 and severe cases of COVID-19 pose the two critical challenges in the battle against COVID-19. Increasing evidence has shown that the viral spike (S) protein-driven syncytia may be responsible for these two events. Intensive attention has thus been devoted to seeking S-guided syncytium inhibitors. However, the current screening campaigns mainly rely on either live virus-based or plasmid-based method, which are always greatly limited by the shortage of high-level biosafety BSL-3 facilities or too much labour-intensive work. Here, we constructed a new hybrid VEEV-SARS-CoV-2-S-eGFP reporter vector through replacement of the structural genes of Venezuelan equine encephalitis virus (VEEV) with the S protein of SARS-CoV-2 as the single structural protein. VEEV-SARS-CoV-2-S-eGFP can propagate steadily through cell-to-cell transmission pathway in S- and ACE2-dependent manner, forming GFP positive syncytia. In addition, a significant dose-dependent decay in GFP signals was observed in VEEV-SARS-CoV-2-S-eGFP replicating cells upon treatment with SARS-CoV-2 antiserum or entry inhibitors, providing further evidence that VEEV-SARS-CoV-2-S-eGFP system is highly sensitive to characterize the anti-syncytium-formation activity of antiviral agents. More importantly, the assay is able to be performed in a BSL-2 laboratory without manipulation of live SARS-CoV-2. Taken together, our work establishes a more convenient and efficient VEEV-SARS-CoV-2-S-eGFP replicating cells-based method for rapid screening of inhibitors blocking syncytium formation.

Intranasal delivery of replicating mRNA encoding neutralizing antibody against SARS-CoV-2 infection in mice.

The lung is the prophylaxis target against SARS-CoV-2 infection, and neutralizing antibodies are a leading class of biological products against various infectious viral pathogen. In this study, we develop a safe and cost-effective platform to express neutralizing antibody in the lung with replicating mRNA basing on alphavirus replicon particle (VRP) delivery system, to prevent SARS-CoV-2 infections. First, a modified VEEV replicon with two subgenomic (sg) promoters was engineered to translate the light and heavy chains of antibody simultaneously, for expression and assembly of neutralizing anti-SARS-CoV-2 antibody CB6. Second, the feasibility and protective efficacy of replicating mRNA against SARS-CoV-2 infection were demonstrated through both in vitro and in vivo assays. The lung target delivery with the help of VRP system resulted in efficiently block SARS-CoV-2 infection with reducing viral titer and less tissue damage in the lung of mice. Overall, our data suggests that expressing neutralizing antibodies in the lungs with the help of self-replicating mRNA could potentially be a promising prophylaxis approach against SARS-CoV-2 infection.

In Vitro Inhibition of Alphaviruses by Lycorine.

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus. As an emerging virus, CHIKV imposes a threat to public health. Currently, there are no vaccines or antivirals available for the prevention of CHIKV infection. Lycorine, an alkaloid from Amaryllidaceae plants, has antiviral activity against a number of viruses such as coronavirus, flavivirus and enterovirus. In this study, we found that lycorine could inhibit CHIKV in cell culture at a concentration of 10 µmol/L without apparent cytotoxicity. In addition, it exhibited broad-spectrum anti-alphavirus activity, including Sindbis virus (SINV), Semliki Forest virus (SFV), and Venezuelan equine encephalomyelitis virus (VEEV). The time of addition studies indicated that lycorine functions at an early post-entry stage of CHIKV life cycle. The results based on two different CHIKV replicons provided further evidence that lycorine exerts its antiviral activity mainly by inhibiting CHIKV translation. Overall, our study extends the antiviral spectrum of lycorine.

ACE2-targeting monoclonal antibody as potent and broad-spectrum coronavirus blocker.

The evolution of coronaviruses, such as SARS-CoV-2, makes broad-spectrum coronavirus preventional or therapeutical strategies highly sought after. Here we report a human angiotensin-converting enzyme 2 (ACE2)-targeting monoclonal antibody, 3E8, blocked the S1-subunits and pseudo-typed virus constructs from multiple coronaviruses including SARS-CoV-2, SARS-CoV-2 mutant variants (SARS-CoV-2-D614G, B.1.1.7, B.1.351, B.1.617.1, and P.1), SARS-CoV and HCoV-NL63, without markedly affecting the physiological activities of ACE2 or causing severe toxicity in ACE2 "knock-in" mice. 3E8 also blocked live SARS-CoV-2 infection in vitro and in a prophylactic mouse model of COVID-19. Cryo-EM and "alanine walk" studies revealed the key binding residues on ACE2 interacting with the CDR3 domain of 3E8 heavy chain. Although full evaluation of safety in non-human primates is necessary before clinical development of 3E8, we provided a potentially potent and "broad-spectrum" management strategy against all coronaviruses that utilize ACE2 as entry receptors and disclosed an anti-coronavirus epitope on human ACE2.

A replication-defective Japanese encephalitis virus (JEV) vaccine candidate with NS1 deletion confers dual protection against JEV and West Nile virus in mice.

In our previous study, we have demonstrated in the context of WNV-ΔNS1 vaccine (a replication-defective West Nile virus (WNV) lacking NS1) that the NS1 trans-complementation system may offer a promising platform for the development of safe and efficient flavivirus vaccines only requiring one dose. Here, we produced high titer (107 IU/ml) replication-defective Japanese encephalitis virus (JEV) with NS1 deletion (JEV-ΔNS1) in the BHK-21 cell line stably expressing NS1 (BHKNS1) using the same strategy. JEV-ΔNS1 appeared safe with a remarkable genetic stability and high degrees of attenuation of in vivo neuroinvasiveness and neurovirulence. Meanwhile, it was demonstrated to be highly immunogenic in mice after a single dose, providing similar degrees of protection to SA14-14-2 vaccine (a most widely used live attenuated JEV vaccine), with healthy condition, undetectable viremia and gradually rising body weight. Importantly, we also found JEV-ΔNS1 induced robust cross-protective immune responses against the challenge of heterologous West Nile virus (WNV), another important member in the same JEV serocomplex, accounting for up to 80% survival rate following a single dose of immunization relative to mock-vaccinated mice. These results not only support the identification of the NS1-deleted flavivirus vaccines with a satisfied balance between safety and efficacy, but also demonstrate the potential of the JEV-ΔNS1 as an alternative vaccine candidate against both JEV and WNV challenge.