Adjuvant-free parenterally injectable vaccine platform that harnesses previously induced IgG as an antigen delivery carrier

Subunit vaccines are among the most useful vaccine modalities; however, their low immunogenicity necessitates the addition of adjuvants. Although adjuvants improve immune responses induced by vaccines, they often cause adverse reactions. To address this, we developed an adjuvant-free subunit vaccine platform that uses pre-existing antibodies generated from past infections or vaccinations as carriers for the delivery of vaccine antigens. Although we have confirmed the usefulness of this platform for nasal vaccines, its suitability as a parenterally injectable vaccine remains uncertain. Here, we verified the potential of our vaccine platform to harness pre-existing immunity for parenterally injectable vaccines. We generated RBD-HA by combining the receptor binding domain (RBD) derived from SARS-CoV-2 as a vaccine antigen with hemagglutinin (HA) sourced from influenza viruses to serve as the carrier protein. We revealed that subcutaneous vaccination with RBD-HA effectively triggered strong RBD-specific IgG responses in mice previously infected with the influenza A virus, even in the absence of adjuvants, and conferred protection to mice against SARS-CoV-2 upon challenge. Furthermore, we revealed that vaccination with RBD-HA did not induce an inflammatory response, such as inflammatory cytokine production, swelling, and recruitment of inflammatory immune cells, whereas conventional vaccines combined with adjuvants induced these adverse reactions. In addition, we demonstrated the remarkable versatility of this platform using a vaccine antigen derived from Streptococcus pneumoniae. These findings indicate the potential of this adjuvant-free vaccine platform to enhance the efficacy of parenterally injectable subunit vaccines and reduce adverse reactions.

Genes involved in the limited spread of SARS-CoV-2 in the lower respiratory airways of hamsters may be associated with adaptive evolution

Novel respiratory viruses can cause a pandemic and then evolve to coexist with humans. The Omicron strain of severe acute respiratory syndrome coronavirus 2 has spread worldwide since its emergence in late 2021, and its sub-lineages are now established in human society. Compared to previous strains, Omicron is markedly less invasive in the lungs and causes less severe disease. One reason for this is that humans are acquiring immunity through previous infection and vaccination, but the nature of the virus itself is also changing. Using our newly established low-volume inoculation system, which reflects natural human infection, we show that the Omicron strain spreads less efficiently into the lungs of hamsters compared with an earlier Wuhan strain. Furthermore, by characterizing chimeric viruses with the Omicron gene in the Wuhan strain genetic background and vice versa, we found that viral genes downstream of ORF3a, but not the S gene, were responsible for the limited spread of the Omicron strain in the lower airways of the virus-infected hamsters. Moreover, molecular evolutionary analysis of SARS-CoV-2 revealed a positive selection of genes downstream of ORF3a (M and E genes). Our findings provide insight into the adaptive evolution of the virus in humans during the pandemic convergence phase.IMPORTANCEThe severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant has spread worldwide since its emergence in late 2021, and its sub-lineages are established in human society. Compared to previous strains, the Omicron strain is less invasive in the lower respiratory tract, including the lungs, and causes less severe disease; however, the mechanistic basis for its restricted replication in the lower airways is poorly understood. In this study, using a newly established low-volume inoculation system that reflects natural human infection, we demonstrated that the Omicron strain spreads less efficiently into the lungs of hamsters compared with an earlier Wuhan strain and found that viral genes downstream of ORF3a are responsible for replication restriction in the lower respiratory tract of Omicron-infected hamsters. Furthermore, we detected a positive selection of genes downstream of ORF3a (especially the M and E genes) in SARS-CoV-2, suggesting that these genes may undergo adaptive changes in humans.

JAK inhibition during the early phase of SARS-CoV-2 infection worsens kidney injury by suppressing endogenous antiviral activity in mice

Coronavirus disease 2019 (COVID-19) induces respiratory dysfunction as well as kidney injury. Although the kidney is considered a target organ of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and affected by COVID-19-induced cytokine storm, the mechanisms of renal reaction in SARS-CoV-2 infection are unknown. In this study, a murine COVID-19 model was induced by nasal infection with mouse-adapted SARS-CoV-2 (MA10). MA10 infection induced body weight loss along with lung inflammation in mice four days after infection. Serum creatinine levels and the urinary albumin/creatinine ratio increased on day 4 after MA10 infection. Measurement of the urinary neutrophil gelatinase-associated lipocalin/creatinine ratio and hematoxylin and eosin staining revealed tubular damage in MA10-infected murine kidneys, indicating kidney injury in the murine COVID-19 model. Interferon (IFN)-γ and interleukin-6 upregulation in the sera of MA10-infected mice, along with the absence of MA10 in the kidneys, implied that the kidneys were affected by the MA10 infection-induced cytokine storm rather than by direct MA10 infection of the kidneys. RNA-sequencing analysis revealed that antiviral genes, such as the IFN/Janus kinase (JAK) pathway, were upregulated in MA10-infected kidneys. Upon administration of the JAK inhibitor baricitinib on days 1-3 after MA10 infection, an antiviral pathway was suppressed, and MA10 was detected more frequently in the kidneys. Notably, JAK inhibition upregulated the hypoxia response and exaggerated kidney injury. These results suggest that endogenous antiviral activity protects against SARS-CoV-2-induced kidney injury in the early phase of infection, providing valuable insights into the pathogenesis of COVID-19-associated nephropathy.

Vero cell-adapted SARS-CoV-2 strain shows increased viral growth through furin-mediated efficient spike cleavage

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) utilizes several host proteases to cleave the spike (S) protein to enter host cells. SARS-CoV-2 S protein is cleaved into S1 and S2 subunits by furin, which is closely involved in the pathogenicity of SARS-CoV-2. However, the effects of the modulated protease cleavage activity due to S protein mutations on viral replication and pathogenesis remain unclear. Herein, we serially passaged two SARS-CoV-2 strains in Vero cells and characterized the cell-adapted SARS-CoV-2 strains in vitro and in vivo. The adapted strains showed high viral growth, effective S1/S2 cleavage of the S protein, and low pathogenicity compared with the wild-type strain. Furthermore, the viral growth and S1/S2 cleavage were enhanced by the combination of the Δ68-76 and H655Y mutations using recombinant SARS-CoV-2 strains generated by the circular polymerase extension reaction. The recombinant SARS-CoV-2 strain, which contained the mutation of the adapted strain, showed increased susceptibility to the furin inhibitor, suggesting that the adapted SARS-CoV-2 strain utilized furin more effectively than the wild-type strain. Pathogenicity was attenuated by infection with effectively cleaved recombinant SARS-CoV-2 strains, suggesting that the excessive cleavage of the S proteins decreases virulence. Finally, the high-growth-adapted SARS-CoV-2 strain could be used as the seed for a low-cost inactivated vaccine; immunization with this vaccine can effectively protect the host from SARS-CoV-2 variants. Our findings provide novel insights into the growth and pathogenicity of SARS-CoV-2 in the evolution of cell-cell transmission.

IMPORTANCE

The efficacy of the S protein cleavage generally differs among the SARS-CoV-2 variants, resulting in distinct viral characteristics. The relationship between a mutation and the entry of SARS-CoV-2 into host cells remains unclear. In this study, we analyzed the sequence of high-growth Vero cell-adapted SARS-CoV-2 and factors determining the enhancement of the growth of the adapted virus and confirmed the characteristics of the adapted strain by analyzing the recombinant SARS-CoV-2 strain. We successfully identified mutations Δ68-76 and H655Y, which enhance viral growth and the S protein cleavage by furin. Using recombinant viruses enabled us to conduct a virus challenge experiment in vivo. The pathogenicity of SARS-CoV-2 introduced with the mutations Δ68-76, H655Y, P812L, and Q853L was attenuated in hamsters, indicating the possibility of the attenuation of excessive cleaved SARS-CoV-2. These findings provide novel insights into the infectivity and pathogenesis of SARS-CoV-2 strains, thereby significantly contributing to the field of virology.

Characterization of a neutralizing antibody that recognizes a loop region adjacent to the receptor-binding interface of the SARS-CoV-2 spike receptor-binding domain

Although the global crisis caused by the coronavirus disease 2019 (COVID-19) pandemic is over, the global epidemic of the disease continues. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the cause of COVID-19, initiates infection via the binding of the receptor-binding domain (RBD) of its spike protein to the human angiotensin-converting enzyme II (ACE2) receptor, and this interaction has been the primary target for the development of COVID-19 therapeutics. Here, we identified neutralizing antibodies against SARS-CoV-2 by screening mouse monoclonal antibodies and characterized an antibody, CSW1-1805, that targets a narrow region at the RBD ridge of the spike protein. CSW1-1805 neutralized several variants in vitro and completely protected mice from SARS-CoV-2 infection. Cryo-EM and biochemical analyses revealed that this antibody recognizes the loop region adjacent to the ACE2-binding interface with the RBD in both a receptor-inaccessible "down" state and a receptor-accessible "up" state and could stabilize the RBD conformation in the up-state. CSW1-1805 also showed different binding orientations and complementarity determining region properties compared to other RBD ridge-targeting antibodies with similar binding epitopes. It is important to continuously characterize neutralizing antibodies to address new variants that continue to emerge. Our characterization of this antibody that recognizes the RBD ridge of the spike protein will aid in the development of future neutralizing antibodies.IMPORTANCESARS-CoV-2 cell entry is initiated by the interaction of the viral spike protein with the host cell receptor. Therefore, mechanistic findings regarding receptor recognition by the spike protein help uncover the molecular mechanism of SARS-CoV-2 infection and guide neutralizing antibody development. Here, we characterized a SARS-CoV-2 neutralizing antibody that recognizes an epitope, a loop region adjacent to the receptor-binding interface, that may be involved in the conformational transition of the receptor-binding domain (RBD) of the spike protein from a receptor-inaccessible "down" state into a receptor-accessible "up" state, and also stabilizes the RBD in the up-state. Our mechanistic findings provide new insights into SARS-CoV-2 receptor recognition and guidance for neutralizing antibody development.

Intranasal immunization with an RBD-hemagglutinin fusion protein harnesses preexisting immunity to enhance antigen-specific responses

Intranasal vaccines are anticipated to be powerful tools for combating many infectious diseases, including SARS-CoV-2, because they induce not only systemic immunity but also mucosal immunity at the site of initial infection. However, they are generally inefficient in inducing an antigen-specific immune response without adjuvants. Here, we developed an adjuvant-free intranasal vaccine platform that utilizes the preexisting immunity induced by previous infection or vaccination to enhance vaccine effectiveness. We made RBD-HA, a fusion of the receptor-binding domain (RBD) of spike derived from SARS-CoV-2 as a vaccine target with HA derived from influenza A virus (IAV) as a carrier protein. Intranasal immunization of previously IAV-infected mice with RBD-HA without an adjuvant elicited robust production of RBD-specific systemic IgG and mucosal IgA by utilizing both HA-specific preexisting IgG and CD4+ T cells. Consequently, the mice were efficiently protected from SARS-CoV-2 infection. Additionally, we demonstrated the high versatility of this intranasal vaccine platform by assessing various vaccine antigens and preexisting immunity associated with a variety of infectious diseases. The results of this study suggest the promising potential of this intranasal vaccine platform to address problems associated with intranasal vaccines.

Electrolyzed hypochlorous acid water exhibits potent disinfectant activity against various viruses through irreversible protein aggregation

It is essential to employ efficient measures to prevent the transmission of pathogenic agents during a pandemic. One such method involves using hypochlorous acid (HClO) solution. The oxidative properties of HClO water (HAW) can contribute to its ability to eliminate viral particles. Here, we examined a highly purified slightly acidic hypochlorous acid water (Hp-SA-HAW) obtained from the reverse osmosis membrane treatment of an electrolytically-generated SA-HAW for its anti-viral activity and mode of action on viral proteins. Hp-SA-HAW exhibited broad-spectrum antiviral effects against various viruses, including adenovirus, hepatitis B virus, Japanese encephalitis virus (JEV), and rotavirus. Additionally, Hp-SA-HAW treatment dose-dependently resulted in irreversibly aggregated multimers of the JEV envelope and capsid proteins. However, Hp-SA-HAW treatment had no discernible effect on viral RNA, indicating that Hp-SA-HAW acts against amino acids rather than nucleic acids. Furthermore, Hp-SA-HAW substantially reduced the infectivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), including the ancestral variant and other multiple variants. Hp-SA-HAW treatment induced the aggregation of the SARS-CoV-2 spike and nuclear proteins and disrupted the binding of the purified spike protein of SARS-CoV-2 to human ACE2. This study demonstrates that the broad-spectrum virucidal activity of highly purified HClO is attributed to viral protein aggregation of virion via protein oxidation.

A nasal vaccine with inactivated whole-virion elicits protective mucosal immunity against SARS-CoV-2 in mice

Introduction

Vaccinations are ideal for reducing the severity of clinical manifestations and secondary complications of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); however, SARS-CoV-2 continues to cause morbidity and mortality worldwide. In contrast to parenteral vaccines such as messenger RNA vaccines, nasal vaccines are expected to be more effective in preventing viral infections in the upper respiratory tract, the primary locus for viral infection and transmission. In this study, we examined the prospects of an inactivated whole-virion (WV) vaccine administered intranasally against SARS-CoV-2.

Methods

Mice were immunized subcutaneously (subcutaneous vaccine) or intranasally (nasal vaccine) with the inactivated WV of SARS-CoV-2 as the antigen.

Results

The spike protein (S)-specific IgA level was found to be higher upon nasal vaccination than after subcutaneous vaccination. The level of S-specific IgG in the serum was also increased by the nasal vaccine, although it was lower than that induced by the subcutaneous vaccine. The nasal vaccine exhibited a stronger defense against viral invasion in the upper respiratory tract than the subcutaneous vaccine and unimmunized control; however, both subcutaneous and nasal vaccines provided protection in the lower respiratory tract. Furthermore, we found that intranasally administered inactivated WV elicited robust production of S-specific IgA in the nasal mucosa and IgG in the blood of mice previously vaccinated with messenger RNA encoding the S protein.

Discussion

Overall, these results suggest that a nasal vaccine containing inactivated WV can be a highly effective means of protection against SARS-CoV-2 infection.

Neutralizing Antibody Response of the Wild-Type/Omicron BA.1 Bivalent Vaccine as the Second Booster Dose against Omicron BA.2 and BA.5

In addition to the original monovalent vaccines available for SARS-CoV-2, bivalent vaccines covering wild-type (WT) and Omicron BA.1 are also available. However, there is a lack of real-world data on the immunogenicity of bivalent vaccines as second boosters against the dominant Omicron sublineages, including BA.2 and BA.5. Healthcare workers (n = 565) who received the first booster vaccination were followed for 2 weeks after the second booster dose of the monovalent mRNA-1273 (WT group, n = 168) and bivalent BNT162b2 (WT+BA.1 group, n = 23) vaccines. Participants with previous SARS-CoV-2 infections were excluded from the study. The anti-receptor binding domain (RBD) antibody levels after the second booster dose in the WT and WT+BA.1 group were similar (median [interquartile range], 26,262.0 [16,951.0 to 38,137.0] U/mL versus 24,840.0 [14,828.0 to 41,460.0] U/mL, respectively). Although the neutralization activities of the pooled sera were lower against BA.5 than against other variants in both groups, the activities against BA.2 and BA.5 in the WT+BA.1 group were higher than those of the WT group in both pseudotyped and live virus assays. Vaccine-related symptoms, including systemic and local symptoms, were strongly correlated with anti-RBD antibody levels and neutralizing titers. In conclusion, the second booster dose of the bivalent (WT/Omicron BA.1) vaccine induced higher neutralizing activity against BA.2 and BA.5 than that of the original monovalent vaccine. IMPORTANCE Although Omicron BA.1-containing bivalent vaccines have been authorized, real-world data validating their safety and antibody responses remain scarce. We conducted a prospective longitudinal study to assess the safety, immunogenicity, and reactogenicity of the second booster dose with the Omicron BA.1 bivalent vaccine in health care workers. Compared with the original monovalent vaccine, the bivalent (WT+BA.1) vaccine elicited higher levels of neutralizing antibodies against the Omicron BA.2 and BA.5 subvariants. The frequency of adverse events after the second booster dose was similar to that of the monovalent vaccine. BA.5-neutralizing antibodies induced by the bivalent Omicron BA.1-containing vaccine were expected to decline. A prospective longitudinal study should be performed to determine the persistence of the humoral immunity.

Global survival trends for brain tumors, by histology: analysis of individual records for 556,237 adults diagnosed in 59 countries during 2000-2014 (CONCORD-3)

BACKGROUND

Survival is a key metric of the effectiveness of a health system in managing cancer. We set out to provide a comprehensive examination of worldwide variation and trends in survival from brain tumors in adults, by histology.

METHODS

We analyzed individual data for adults (15-99 years) diagnosed with a brain tumor (ICD-O-3 topography code C71) during 2000-2014, regardless of tumor behavior. Data underwent a 3-phase quality control as part of CONCORD-3. We estimated net survival for 11 histology groups, using the unbiased nonparametric Pohar Perme estimator.

RESULTS

The study included 556,237 adults. In 2010-2014, the global range in age-standardized 5-year net survival for the most common sub-types was broad: in the range 20%-38% for diffuse and anaplastic astrocytoma, from 4% to 17% for glioblastoma, and between 32% and 69% for oligodendroglioma. For patients with glioblastoma, the largest gains in survival occurred between 2000-2004 and 2005-2009. These improvements were more noticeable among adults diagnosed aged 40-70 years than among younger adults.

CONCLUSIONS

To the best of our knowledge, this study provides the largest account to date of global trends in population-based survival for brain tumors by histology in adults. We have highlighted remarkable gains in 5-year survival from glioblastoma since 2005, providing large-scale empirical evidence on the uptake of chemoradiation at population level. Worldwide, survival improvements have been extensive, but some countries still lag behind. Our findings may help clinicians involved in national and international tumor pathway boards to promote initiatives aimed at more extensive implementation of clinical guidelines.

Antibody feedback contributes to facilitating the development of Omicron-reactive memory B cells in SARS-CoV-2 mRNA vaccinees

In contrast to a second dose of the SARS-CoV-2 mRNA vaccine, a third dose elicits potent neutralizing activity against the Omicron variant. To address the underlying mechanism for this differential antibody response, we examined spike receptor-binding domain (RBD)-specific memory B cells in vaccinated individuals. Frequency of Omicron-reactive memory B cells increased ∼9 mo after the second vaccine dose. These memory B cells show an altered distribution of epitopes from pre-second memory B cells, presumably due to an antibody feedback mechanism. This hypothesis was tested using mouse models, showing that an addition or a depletion of RBD-induced serum antibodies results in a concomitant increase or decrease, respectively, of Omicron-reactive germinal center (GC) and memory B cells. Our data suggest that pre-generated antibodies modulate the selection of GC and subsequent memory B cells after the second vaccine dose, accumulating more Omicron-reactive memory B cells over time, which contributes to the generation of Omicron-neutralizing antibodies elicited by the third vaccine dose.

Establishment and clinical application of SARS-CoV-2 catch column

BACKGROUND

A certain number of patients with coronavirus disease 2019 (COVID-19), particularly those who test positive for SARS-CoV-2 in the serum, are hospitalized. Further, some even die. We examined the effect of blood adsorption therapy using columns that can eliminate SARS-CoV-2 on the improvement of the prognosis of severe COVID-19 patients.

METHODS

This study enrolled seven patients receiving mechanical ventilation. The patients received viral adsorption therapy using SARS-catch column for 3 days. The SARS-catch column was developed by immobilizing a specific peptide, designed based on the sequence of human angiotensin-converting enzyme 2 (hACE2), to an endotoxin adsorption column (PMX). In total, eight types of SARS-CoV-2-catch (SCC) candidate peptides were developed. Then, a clinical study on the effects of blood adsorption therapy using the SARS-catch column in patients with severe COVID-19 was performed, and the data in the present study were compared with historical data of severe COVID-19 patients.

RESULTS

Among all SCC candidate peptides, SCC-4N had the best adsorption activity against SARS-CoV-2. The SARS-catch column using SCC-4N removed 65% more SARS-CoV-2 than PMX. Compared with historical data, the weaning time from mechanical ventilation was faster in the present study. In addition, the rate of negative blood viral load in the present study was higher than that in the historical data.

CONCLUSION

The timely treatment with virus adsorption therapy may eliminate serum SARS-CoV-2 and improve the prognosis of patients with severe COVID-19. However, large-scale studies must be performed in the future to further assess the finding of this study (jRCTs052200134).

Versatile live-attenuated SARS-CoV-2 vaccine platform applicable to variants induces protective immunity

Live-attenuated vaccines are generally highly effective. Here, we aimed to develop one against SARS-CoV-2, based on the identification of three types of temperature-sensitive (TS) strains with mutations in nonstructural proteins (nsp), impaired proliferation at 37-39ºC, and the capacity to induce protective immunity in Syrian hamsters. To develop a live-attenuated vaccine, we generated a virus that combined all these TS-associated mutations (rTS-all), which showed a robust TS phenotype in vitro and high attenuation in vivo. The vaccine induced an effective cross-reactive immune response and protected hamsters against homologous or heterologous viral challenges. Importantly, rTS-all rarely reverted to the wild-type phenotype. By combining these mutations with an Omicron spike protein to construct a recombinant virus, protection against the Omicron strain was obtained. We show that immediate and effective live-attenuated vaccine candidates against SARS-CoV-2 variants may be developed using rTS-all as a backbone to incorporate the spike protein of the variants.

SARS-CoV-2 disrupts respiratory vascular barriers by suppressing Claudin-5 expression

In the initial process of coronavirus disease 2019 (COVID-19), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects respiratory epithelial cells and then transfers to other organs the blood vessels. It is believed that SARS-CoV-2 can pass the vascular wall by altering the endothelial barrier using an unknown mechanism. In this study, we investigated the effect of SARS-CoV-2 on the endothelial barrier using an airway-on-a-chip that mimics respiratory organs and found that SARS-CoV-2 produced from infected epithelial cells disrupts the barrier by decreasing Claudin-5 (CLDN5), a tight junction protein, and disrupting vascular endothelial cadherin-mediated adherens junctions. Consistently, the gene and protein expression levels of CLDN5 in the lungs of a patient with COVID-19 were decreased. CLDN5 overexpression or Fluvastatin treatment rescued the SARS-CoV-2-induced respiratory endothelial barrier disruption. We concluded that the down-regulation of CLDN5 expression is a pivotal mechanism for SARS-CoV-2-induced endothelial barrier disruption in respiratory organs and that inducing CLDN5 expression is a therapeutic strategy against COVID-19.

SARS-CoV-2 ORF8 is a viral cytokine regulating immune responses

Many patients with severe COVID-19 suffer from pneumonia and the elucidation of the mechanisms underlying the development of this severe condition is important. The in vivo function of the ORF8 protein secreted by SARS-CoV-2 is not well understood. Here, we analyzed the function of ORF8 protein by generating ORF8-knockout SARS-CoV-2 and found that the lung inflammation observed in wild-type SARS-CoV-2-infected hamsters was decreased in ORF8-knockout SARS-CoV-2-infected hamsters. Administration of recombinant ORF8 protein to hamsters also induced lymphocyte infiltration into the lungs. Similar pro-inflammatory cytokine production was observed in primary human monocytes treated with recombinant ORF8 protein. Furthermore, we demonstrated that the serum ORF8 protein levels are well-correlated with clinical markers of inflammation. These results demonstrated that the ORF8 protein is a SARS-CoV-2 viral cytokine involved in the immune dysregulation observed in COVID-19 patients, and that the ORF8 protein could be a novel therapeutic target in severe COVID-19 patients.

Immune response induced in rodents by anti-CoVid19 plasmid DNA vaccine via pyro-drive jet injector inoculation

There is an urgent need to stop the coronavirus disease 2019 (COVID-19) pandemic through the development of efficient and safe vaccination methods. Over the short term, plasmid DNA vaccines can be developed as they are molecularly stable, thus facilitating easy transport and storage. pVAX1-SARS-CoV2-co was designed for the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) S protein. The antibodies produced led to immunoreactions against the S protein, an anti-receptor-binding-domain, and a neutralizing action of the pVAX1-SARS-CoV2-co, as previously confirmed. To promote the efficacy of the pVAX1-SARS-CoV2-co vaccine a pyro-drive jet injector (PJI) was used. An intradermally adjusted PJI demonstrated that the pVAX1-SARS-CoV2-co vaccine injection caused a high production of anti-S protein antibodies, triggered immunoreactions, and neutralized the actions against SARS-CoV-2. A high-dose pVAX1-SARS-CoV2-co intradermal injection using PJI did not cause any serious disorders in the rat model. A viral challenge confirmed that intradermally immunized mice were potently protected from COVID-19. A pVAX1-SARS-CoV2-co intradermal injection using PJI is a safe and promising vaccination method for overcoming the COVID-19 pandemic.

Establishment of Neutralizing Monoclonal Antibodies Against Severe Acute Respiratory Syndrome Coronavirus 2 by the Screening with Exosomes Expressing the Viral Spike Protein

Monoclonal antibodies (mAbs) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes COVID-19, are the important tools both for the diagnosis and therapeutics of this infectious disease. The high-performance antibody against spike protein of SARS-CoV-2 is expected to inhibit the binding of viruses to their receptors on the surface of their target cells. In this study, we propose the novel screening method for mAbs against the pathogenic infectious virus using exosome. By this method, the exosome that artificially expresses SARS-CoV-2 spike protein was purified and used as a virus-like vesicle, which could bind to the viral receptor, angiotensin-converting enzyme 2 (ACE2). As a result, seven mAbs that could bind to the spike protein were obtained and six of these clones could strongly inhibit the binding to ACE2 of both the protein corresponding to the receptor binding domain (RBD) and the exosome expressing the spike protein. Interestingly, some of these antibodies seemed to share their epitopes in RBD, suggesting that highly antigenic sites exist in the spike protein. In view of the neutralizing activities on infection, five clones of these antibodies could inhibit the internalization of vesicular stomatitis virus-based pseudo viruses expressing various types of spike proteins derived from SARS-CoV-2 variants. In addition, these antibodies inhibited the infection of SARS-CoV-2 to cultured mammalian cells. These antibodies are expected to be utilized for both diagnosis and therapeutics of COVID-19.

Effectiveness of the third dose of BNT162b2 vaccine on neutralizing Omicron variant in the Japanese population

Introduction

The vaccine against SARS-CoV-2 provides humoral immunity to fight COVID-19; however, the acquired immunity gradually declines. Booster vaccination restores reduced humoral immunity; however, its effect on newly emerging variants, such as the Omicron variant, is a concern. As the waves of COVID-19 cases and vaccine programs differ between countries, it is necessary to know the domestic effect of the booster.

Methods

Serum samples were obtained from healthcare workers (20–69 years old) in the Pfizer BNT162b2 vaccine program at the Toyama University Hospital 6 months after the second dose (6mA2D, n = 648) and 2 weeks after the third dose (2wA3D, n = 565). The anti-SARS-CoV-2 antibody level was measured, and neutralization against the wild-type and variants (Delta and Omicron) was evaluated using pseudotyped viruses. Data on booster-related events were collected using questionnaires.

Results

The median anti-SARS-CoV-2 antibody was >30.9-fold elevated after the booster (6mA2D, 710.0 U/mL [interquartile range (IQR): 443.0–1068.0 U/mL]; 2wA3D, 21927 U/mL [IQR: 15321.0–>25000.0 U/mL]). Median neutralizing activity using 100-fold sera against wild-type-, Delta-, and Omicron-derived variants was elevated from 84.6%, 36.2%, and 31.2% at 6mA2D to >99.9%, 99.1%, and 94.6% at 2wA3D, respectively. The anti-SARS-CoV-2 antibody levels were significantly elevated in individuals with fever ≥37.5 °C, general fatigue, and myalgia, local swelling, and local hardness.

Conclusion

The booster effect, especially against the Omicron variant, was observed in the Japanese population. These findings contribute to the precise understanding of the efficacy and side effects of the booster and the promotion of vaccine campaigns.

Secretory glycoprotein NS1 plays a crucial role in the particle formation of flaviviruses

Flaviviruses, which are globally distributed and cause a spectrum of potentially severe illnesses, pose a major threat to public health. Although Flaviviridae viruses, including flaviviruses, possess similar genome structures, only the flaviviruses encode the non-structural protein NS1, which resides in the endoplasmic reticulum (ER) and is secreted from cells after oligomerization. The ER-resident NS1 is known to be involved in viral genome replication, but the essential roles of secretory NS1 in the virus life cycle are not fully understood. Here we characterized the roles of secretory NS1 in the particle formation of flaviviruses. We first identified an amino acid residue essential for the NS1 secretion but not for viral genome replication by using protein-protein interaction network analyses and mutagenesis scanning. By using the recombinant flaviviruses carrying the identified NS1 mutation, we clarified that the mutant flaviviruses employed viral genome replication. We then constructed a recombinant NS1 with the identified mutation and demonstrated by physicochemical assays that the mutant NS1 was unable to form a proper oligomer or associate with liposomes. Finally, we showed that the functions of NS1 that were lost by the identified mutation could be compensated for by the in trans-expression of E^rns of pestiviruses and host exchangeable apolipoproteins, which participate in the infectious particle formation of pestiviruses and hepaciviruses in the family Flaviviridae, respectively. Collectively, our study suggests that secretory NS1 plays a role in the particle formation of flaviviruses through its interaction with the lipid membrane.

It is difficult to characterize the function of NS1 in the post-genome replication stages in the virus life cycle of flaviviruses. Here, by means of protein-protein interaction network analyses and mutagenesis scanning, we identified a unique mutation in NS1 by which the protein loses its secretory capacity while retaining its genome replication activity. Physicochemical assays using the mutant NS1 revealed that oligomerization of NS1 is responsible for the lipid association and secretion of NS1. In addition, we established a complementation assay that can evaluate the particle formation of Flaviviridae viruses. By using recombinant flaviviruses possessing the identified mutation in NS1, we clarified that NS1 is involved in particle formation. Our findings reveal that the flavivirus NS1 has at least two roles in the virus life cycles—namely, a role in infectious particle formation and a role in viral genome replication.

SARS-CoV-2 infection triggers paracrine senescence and leads to a sustained senescence-associated inflammatory response

Reports of post-acute COVID-19 syndrome, in which the inflammatory response persists even after SARS-CoV-2 has disappeared, are increasing¹, but the underlying mechanisms of post-acute COVID-19 syndrome remain unknown. Here, we show that SARS-CoV-2-infected cells trigger senescence-like cell-cycle arrest^2,3 in neighboring uninfected cells in a paracrine manner via virus-induced cytokine production. In cultured human cells or bronchial organoids, these SASR-CoV-2 infection-induced senescent cells express high levels of a series of inflammatory factors known as senescence-associated secretory phenotypes (SASPs)⁴ in a sustained manner, even after SARS-CoV-2 is no longer detectable. We also show that the expression of the senescence marker CDKN2A (refs. ^5,6) and various SASP factor⁴ genes is increased in the pulmonary cells of patients with severe post-acute COVID-19 syndrome. Furthermore, we find that mice exposed to a mouse-adapted strain of SARS-CoV-2 exhibit prolonged signs of cellular senescence and SASP in the lung at 14 days after infection when the virus was undetectable, which could be substantially reduced by the administration of senolytic drugs⁷. The sustained infection-induced paracrine senescence described here may be involved in the long-term inflammation caused by SARS-CoV-2 infection.

Age-Dependent Reduction in Neutralization against Alpha and Beta Variants of BNT162b2 SARS-CoV-2 Vaccine-Induced Immunity

Vaccines against severe acute respiratory syndrome coronavirus-2 have been introduced. To investigate the relationship between vaccine-induced humoral immunity and patient age, we measured antibody levels and neutralization in vaccinated sera. Sera from 13 to 17 days after the second dose of the BNT162b2 vaccine were collected from health care workers at the University of Toyama (n = 740). Antibody levels were measured by the anti-receptor binding domain antibody test (anti-RBD test), and neutralization against wild-type (WT), α- and β-variant pseudotyped viruses were assayed using a high-throughput chemiluminescent reduction neutralizing test (htCRNT; positivity cutoff, 50% neutralization at serum dilution 1:100). Basic clinical characteristics were obtained from questionnaires. Antibodies were confirmed in all participants in both the anti-RBD test (median, 2,112 U/ml; interquartile range [IQR], 1,275 to 3,390 U/ml) and the htCRNT against WT (median % inhibition, >99.9; IQR, >99.9 to >99.9). For randomly selected sera (n = 61), 100.0% had positive htCRNT values against the α- and β-derived variants. Among those who answered the questionnaire (n = 237), the values of the anti-RBD test were negatively correlated with age in females (P < 0.01). An age-dependent decline in neutralization was observed against the variants but not against the wild-type virus (wild type, P = 0.09; α, P < 0.01; β, P < 0.01). The neutralizing activity induced by BNT162b2 was obtained not only against the wild-type virus, but also against the variants; however, there was an age-dependent decrease in the latter. Age-related heterogeneity of vaccine-acquired immunity is a concern in preventive strategies in the era dominated by variants. IMPORTANCE Since mRNA vaccines utilize wild-type SARS-CoV-2 spike protein as an antigen, there are potential concerns about acquiring immunity to variants of this virus. The neutralizing activity in BNT162b2-vaccinated individuals was higher against the wild-type virus than against its variants; this effect was more apparent in older age groups. This finding suggests that one of the weaknesses of the mRNA vaccine is the high risk of variant infection in the elderly population. Because the elderly are at a higher risk of SARS-CoV-2 infection, the age-dependent decline of neutralization against viral variants should be considered while planning vaccination programs that include boosters.

Glycan engineering of the SARS-CoV-2 receptor-binding domain elicits cross-neutralizing antibodies for SARS-related viruses

Broadly protective vaccines against SARS-related coronaviruses that may cause future outbreaks are urgently needed. The SARS-CoV-2 spike receptor-binding domain (RBD) comprises two regions, the core-RBD and the receptor-binding motif (RBM); the former is structurally conserved between SARS-CoV-2 and SARS-CoV. Here, in order to elicit humoral responses to the more conserved core-RBD, we introduced N-linked glycans onto RBM surfaces of the SARS-CoV-2 RBD and used them as immunogens in a mouse model. We found that glycan addition elicited higher proportions of the core-RBD–specific germinal center (GC) B cells and antibody responses, thereby manifesting significant neutralizing activity for SARS-CoV, SARS-CoV-2, and the bat WIV1-CoV. These results have implications for the design of SARS-like virus vaccines.

DsRNA Sequencing for RNA Virus Surveillance Using Human Clinical Samples

Although viruses infect various organs and are associated with diseases, there may be many unidentified pathogenic viruses. The recent development of next-generation sequencing technologies has facilitated the establishment of an environmental viral metagenomic approach targeting the intracellular viral genome. However, an efficient method for the detection of a viral genome derived from an RNA virus in animal or human samples has not been established. Here, we established a method for the efficient detection of RNA viruses in human clinical samples. We then tested the efficiency of the method compared to other conventional methods by using tissue samples collected from 57 recipients of living donor liver transplantations performed between June 2017 and February 2019 at Kyushu University Hospital. The viral read ratio in human clinical samples was higher by the new method than by the other conventional methods. In addition, the new method correctly identified viral RNA from liver tissues infected with hepatitis C virus. This new technique will be an effective tool for intracellular RNA virus surveillance in human clinical samples and may be useful for the detection of new RNA viruses associated with diseases.

Combining machine learning and nanopore construction creates an artificial intelligence nanopore for coronavirus detection

High-throughput, high-accuracy detection of emerging viruses allows for the control of disease outbreaks. Currently, reverse transcription-polymerase chain reaction (RT-PCR) is currently the most-widely used technology to diagnose the presence of SARS-CoV-2. However, RT-PCR requires the extraction of viral RNA from clinical specimens to obtain high sensitivity. Here, we report a method for detecting novel coronaviruses with high sensitivity by using nanopores together with artificial intelligence, a relatively simple procedure that does not require RNA extraction. Our final platform, which we call the artificially intelligent nanopore, consists of machine learning software on a server, a portable high-speed and high-precision current measuring instrument, and scalable, cost-effective semiconducting nanopore modules. We show that artificially intelligent nanopores are successful in accurately identifying four types of coronaviruses similar in size, HCoV-229E, SARS-CoV, MERS-CoV, and SARS-CoV-2. Detection of SARS-CoV-2 in saliva specimen is achieved with a sensitivity of 90% and specificity of 96% with a 5-minute measurement.

An infectivity-enhancing site on the SARS-CoV-2 spike protein targeted by antibodies

Antibodies against the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein prevent SARS-CoV-2 infection. However, the effects of antibodies against other spike protein domains are largely unknown. Here, we screened a series of anti-spike monoclonal antibodies from coronavirus disease 2019 (COVID-19) patients and found that some of antibodies against the N-terminal domain (NTD) induced the open conformation of RBD and thus enhanced the binding capacity of the spike protein to ACE2 and infectivity of SARS-CoV-2. Mutational analysis revealed that all of the infectivity-enhancing antibodies recognized a specific site on the NTD. Structural analysis demonstrated that all infectivity-enhancing antibodies bound to NTD in a similar manner. The antibodies against this infectivity-enhancing site were detected at high levels in severe patients. Moreover, we identified antibodies against the infectivity-enhancing site in uninfected donors, albeit at a lower frequency. These findings demonstrate that not only neutralizing antibodies but also enhancing antibodies are produced during SARS-CoV-2 infection.

Establishment of a reverse genetics system for SARS-CoV-2 using circular polymerase extension reaction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been identified as the causative agent of coronavirus disease 2019 (COVID-19). Although multiple mutations have been observed in SARS-CoV-2, functional analysis of each mutation of SARS-CoV-2 has been limited by the lack of convenient mutagenesis methods. In this study, we establish a PCR-based, bacterium-free method to generate SARS-CoV-2 infectious clones. Recombinant SARS-CoV-2 could be rescued at high titer with high accuracy after assembling 10 SARS-CoV-2 cDNA fragments by circular polymerase extension reaction (CPER) and transfection of the resulting circular genome into susceptible cells. The construction of infectious clones for reporter viruses and mutant viruses could be completed in two simple steps: introduction of reporter genes or mutations into the desirable DNA fragments (∼5,000 base pairs) by PCR and assembly of the DNA fragments by CPER. This reverse genetics system may potentially advance further understanding of SARS-CoV-2.

Ponesimod suppresses hepatitis B virus infection by inhibiting endosome maturation

The discovery of novel antivirals to treat hepatitis B virus (HBV) infection is urgently needed, as the currently available drugs mainly target viral proteins at replication step, whereas host factors also play significant roles in HBV infection. Although numerous studies have reported candidate drugs for HBV treatment, there remains a need to find a new drug that may target other steps of the HBV life cycle. In this study, by drug screening of a 533 G-protein-coupled receptors (GPCRs)-associated compound library, we identified ponesimod, a selective agonist of sphingosine-1-phosphate receptor 1 (S1P₁), as a drug candidate for the suppression of HBV infection. However, the anti-HBV effect of ponesimod is independent of S1P₁ and other sphingosine-1-phosphate receptors (S1PRs). Treatment with ponesimod at an early step of infection but not at a post-entry step significantly reduced the HBV relaxed circular DNA (rcDNA) level in a dose-dependent manner. Ponesimod treatment did not inhibit attachment, binding, or internalization of HBV particles via endocytosis through an interaction with sodium taurocholate cotransporting polypeptide (NTCP) or epidermal growth factor receptor (EGFR). Importantly, during the transportation of HBV particles to the nucleus, co-localization of HBV with early endosomes but not with late endosomes and lysosomes was induced by the treatment with ponesimod, suggesting that ponesimod interferes with the conversion of early endosomes to late endosomes without significant damage to cellular growth. Conclusion: Ponesimod is a promising anti-HBV drug targeting the endosome maturation of HBV. This finding can be applied to the development of novel antivirals that target the trafficking pathway of HBV particles.

Various miRNAs compensate the role of miR-122 on HCV replication

One of the determinants for tissue tropism of hepatitis C virus (HCV) is miR-122, a liver-specific microRNA. Recently, it has been reported that interaction of miR-122 to HCV RNA induces a conformational change of the 5'UTR internal ribosome entry site (IRES) structure to form stem-loop II structure (SLII) and hijack of translating 80S ribosome through the binding of SLIII to 40S subunit, which leads to efficient translation. On the other hand, low levels of HCV-RNA replication have also been detected in some non-hepatic cells; however, the details of extrahepatic replication remain unknown. These observations suggest the possibility that miRNAs other than miR-122 can support efficient replication of HCV-RNA in non-hepatic cells. Here, we identified a number of such miRNAs and show that they could be divided into two groups: those that bind HCV-RNA at two locations (miR-122 binding sites I and II), in a manner similar to miR-122 (miR-122-like), and those that target a single site that bridges sites I and II and masking both G28 and C29 in the 5'UTR (non-miR-122-like). Although the enhancing activity of these non-hepatic miRNAs were lower than those of miR-122, substantial expression was detected in various normal tissues. Furthermore, structural modeling indicated that both miR-122-like and non-miR-122-like miRNAs not only can facilitate the formation of an HCV IRES SLII but also can stabilize IRES 3D structure in order to facilitate binding of SLIII to the ribosome. Together, these results suggest that HCV facilitates miR-122-independent replication in non-hepatic cells through recruitment of miRNAs other than miR-122. And our findings can provide a more detailed mechanism of miR-122-dependent enhancement of HCV-RNA translation by focusing on IRES tertiary structure.

Rimonabant suppresses RNA transcription of hepatitis B virus by inhibiting hepatocyte nuclear factor 4α

Chronic infection with hepatitis B virus (HBV) sometime induces lethal cirrhosis and hepatocellular carcinoma. Although nucleot(s)ide analogs are used as main treatment for HBV infection, the emergence of the drug-resistant viruses has become a problem. To discover novel antivirals with low side effects and low risk of emergence of resistant viruses, screening for anti-HBV compounds was performed with compound libraries of inhibitors targeting G-protein-coupled receptors (GPCRs). HepG2-hNTCP C4 cells infected with HBV were treated with various GPCR inhibitors and harvested at 14 day postinfection for quantification of core protein in the first screening or relaxed circular DNA in the second screening. Finally, we identified a cannabinoid receptor 1 inhibitor, rimonabant, as a candidate showing anti-HBV effect. In HepG2-hNTCP C4 cells, treatment with rimonabant suppressed HBV propagation at the viral RNA transcription step but had no effect on entry or covalently closed circular DNA level. The values of half maximal inhibitory concentration, half maximal effective concentration, and selectivity index of rimonabant in primary human hepatocyte (PHH) are 2.77 μm, 40.4 μm, and 14.6, respectively. Transcriptome analysis of rimonabant-treated primary hepatocytes by RNA sequencing revealed that the transcriptional activity of hepatocyte nuclear factor 4α (HNF4α), which is known to stimulate viral RNA synthesis, was depressed. By treatment of PHH with rimonabant, the expression level of HNF4α protein and the production of the messenger RNAs (mRNAs) of downstream factors promoted by HNF4α were reduced while the amount of HNF4α mRNA was not altered. These results suggest that treatment with rimonabant suppresses HBV propagation through the inhibition of HNF4α activity.

Characterization of human pegivirus infection in liver transplantation recipients

Approximately 2% of healthy persons are infected with human pegivirus (HPgV). HPgV is transmitted via vertical, sexual, and blood-borne routes. Recently, the association of HPgV infection with the risk of lymphoma was reported. Here, we examined the prevalence of chronic HPgV infection in liver transplantation (LT) recipients and patients with hepatectomy and the influence of HPgV infection after LT on clinical and perioperative factors. We enrolled 313 LT recipients and 187 patients with hepatectomy who received care at the Kyusyu University Hospital between May 1997 and September 2017. Of the 313 recipients and 187 patients enrolled in this study, 44 recipients (14.1%) and 2 patients (1.1%) had HPgV viremia, respectively. There was no significant association between HPgV infection and LT outcomes. Interestingly, one recipient was infected with HPgV during the peritransplant period, which was likely transmitted via blood transfusion because HPgV RNA was detected from the blood bag transfused to the recipient during LT. We reviewed the available literature on the prevalence HPgV infections in other organ-transplanted patients and whether they impacted clinical outcomes. They also had the higher prevalence of HPgV infection, while it appears to be of low or no consequences. In addition, HPgV infection induced the upregulation of interferon-stimulated gene (ISG) expression in peripheral blood mononuclear cells. LT recipients had higher HPgV viremia compared to patients with hepatectomy. Although HPgV infection was not associated with LT-related outcomes, it induced ISG expression in recipients.

A novel occludin-targeting monoclonal antibody prevents hepatitis C virus infection in vitro

Since hepatitis C virus (HCV) is thought to enter into host hepatocytes using the same cellular pathways regardless of the genotypes, the host factors are promising targets to prevent and treat HCV infection. Human occludin (hOCLN) is one representative entry factor, and its second extracellular loop (EC2) contributes to the species selectivity of HCV-susceptibility. However, the exact function of hOCLN during HCV entry remains unknown, and no hOCLN-targeting antibodies or synthetic drugs that prevent and treat HCV infection have yet been developed. Here we generated the anti-hOCLN-EC2 monoclonal antibody (mAb) 67-2, and demonstrated that it efficiently inhibited HCV infection in the HCV-permissive human cell line Huh7.5.1. We also showed, using three different culture systems of Huh7.5.1 cells, that this novel mAb is accessible to OCLN from the basolateral side of hepatocytes but not from the apical side. In addition, our Western blot analyses indicated that the established 67-2 mAb reacted not only with hOCLN but also with mouse OCLN, strongly suggesting that 67-2 does not recognize the human-specific amino acids in OCLN-EC2. Moreover, we revealed that the anti-hOCLN-EC2 mAb 67-2 showed no adverse effects on cell viability or the barrier function of tight junctions.

Evaluation of viral contamination in a baculovirus expression system

Insect expression systems based on baculovirus are widely used for generating recombinant proteins. Here, the infectivity of baculoviruses under the physiological stresses of 'freeze-thaw' and sonication and the baculoviral contamination of recombinant proteins after protein purification were evaluated. Our findings suggest that Nonidet P-40 (NP-40) treatment of baculoviruses completely abolishes their infectivity and that recombinant proteins purified with affinity beads do not include infectious baculoviruses. We therefore suggest that baculovirus is completely inactivated by NP-40 treatment and that recombinant proteins are unlikely to be contaminated with infectious baculoviruses after their affinity purification.

Suppression of HBV replication by the expression of nickase- and nuclease dead-Cas9

Complete removal of hepatitis B virus (HBV) DNA from nuclei is difficult by the current therapies. Recent reports have shown that a novel genome-editing tool using Cas9 with a single-guide RNA (sgRNA) system can cleave the HBV genome in vitro and in vivo. However, induction of a double-strand break (DSB) on the targeted genome by Cas9 risks undesirable off-target cleavage on the host genome. Nickase-Cas9 cleaves a single strand of DNA, and thereby two sgRNAs are required for inducing DSBs. To avoid Cas9-induced off-target mutagenesis, we examined the effects of the expressions of nickase-Cas9 and nuclease dead Cas9 (d-Cas9) with sgRNAs on HBV replication. The expression of nickase-Cas9 with a pair of sgRNAs cleaved the target HBV genome and suppressed the viral-protein expression and HBV replication in vitro. Moreover, nickase-Cas9 with the sgRNA pair cleaved the targeted HBV genome in mouse liver. Interestingly, d-Cas9 expression with the sgRNAs also suppressed HBV replication in vitro without cleaving the HBV genome. These results suggest the possible use of nickase-Cas9 and d-Cas9 with a pair of sgRNAs for eliminating HBV DNA from the livers of chronic hepatitis B patients with low risk of undesirable off-target mutation on the host genome.

Host-derived apolipoproteins play comparable roles with viral secretory proteins Erns and NS1 in the infectious particle formation of Flaviviridae

Amphipathic α-helices of exchangeable apolipoproteins have shown to play crucial roles in the formation of infectious hepatitis C virus (HCV) particles through the interaction with viral particles. Among the Flaviviridae members, pestivirus and flavivirus possess a viral structural protein E^rns or a non-structural protein 1 (NS1) as secretory glycoproteins, respectively, while Hepacivirus including HCV has no secretory glycoprotein. In case of pestivirus replication, the C-terminal long amphipathic α-helices of E^rns are important for anchoring to viral membrane. Here we show that host-derived apolipoproteins play functional roles similar to those of virally encoded E^rns and NS1 in the formation of infectious particles. We examined whether E^rns and NS1 could compensate for the role of apolipoproteins in particle formation of HCV in apolipoprotein B (ApoB) and ApoE double-knockout Huh7 (BE-KO), and non-hepatic 293T cells. We found that exogenous expression of either E^rns or NS1 rescued infectious particle formation of HCV in the BE-KO and 293T cells. In addition, expression of apolipoproteins or NS1 partially rescued the production of infectious pestivirus particles in cells upon electroporation with an E^rns-deleted non-infectious RNA. As with exchangeable apolipoproteins, the C-terminal amphipathic α-helices of E^rns play the functional roles in the formation of infectious HCV or pestivirus particles. These results strongly suggest that the host- and virus-derived secretory glycoproteins have overlapping roles in the viral life cycle of Flaviviridae, especially in the maturation of infectious particles, while E^rns and NS1 also participate in replication complex formation and viral entry, respectively. Considering the abundant hepatic expression and liver-specific propagation of these apolipoproteins, HCV might have evolved to utilize them in the formation of infectious particles through deletion of a secretory viral glycoprotein gene.

The family Flaviviridae consists of 4 genera, namely Flavivirus, Pestivirus, Pegivirus, and Hepacivirus. Flaviviruses and pestiviruses can infect various species and tissues; however, infection of pegivirus and hepacivirus is observed in a strikingly restricted range of tissue and hosts. Although all the Flaviviridae viruses possess a similar genome structure, hepatitis C virus (HCV) from Hepacivirus encodes no secretory glycoprotein, such as E^rns of pestivirus and NS1 of flavivirus. The apolipoproteins, one of the host secretory glycoproteins, play important roles in the formation of infectious HCV particles through the interaction with viral particles. The data presented here show that the host-derived apolipoproteins and viral-derived E^rns and NS1 have overlapping roles in the maturation of infectious particles of Flaviviridae. Considering an abundant expression of apolipoproteins in the liver and their liver-specific propagation, HCV might have evolved to utilize the apolipoproteins in the formation of infectious particles through deletion of a gene encoding a secretory viral glycoprotein. The data of this manuscript also suggest that utilization of host factors in the viral life cycle is closely associated with the tissue- and species-specificities and evolution among Flaviviridae viruses.

Characterization of miR-122-independent propagation of HCV

miR-122, a liver-specific microRNA, is one of the determinants for liver tropism of hepatitis C virus (HCV) infection. Although miR-122 is required for efficient propagation of HCV, we have previously shown that HCV replicates at a low rate in miR-122-deficient cells, suggesting that HCV-RNA is capable of propagating in an miR-122-independent manner. We herein investigated the roles of miR-122 in both the replication of HCV-RNA and the production of infectious particles by using miR-122-knockout Huh7 (Huh7-122KO) cells. A slight increase of intracellular HCV-RNA levels and infectious titers in the culture supernatants was observed in Huh7-122KO cells upon infection with HCV. Moreover, after serial passages of HCV in miR-122-knockout Huh7.5.1 cells, we obtained an adaptive mutant, HCV_122KO, possessing G28A substitution in the 5’UTR of the HCV genotype 2a JFH1 genome, and this mutant may help to enhance replication complex formation, a possibility supported by polysome analysis. We also found the introduction of adaptive mutation around miR-122 binding site in the genotype 1b/2a chimeric virus, which originally had an adenine at the nucleotide position 29. HCV_122KO exhibited efficient RNA replication in miR-122-knockout cells and non-hepatic cells without exogenous expression of miR-122. Competition assay revealed that the G28A mutant was dominant in the absence of miR-122, but its effects were equivalent to those of the wild type in the presence of miR-122, suggesting that the G28A mutation does not confer an advantage for propagation in miR-122-rich hepatocytes. These observations may explain the clinical finding that the positive rate of G28A mutation was higher in miR-122-deficient PBMCs than in the patient serum, which mainly included the hepatocyte-derived virus from HCV-genotype-2a patients. These results suggest that the emergence of HCV mutants that can propagate in non-hepatic cells in an miR-122-independent manner may participate in the induction of extrahepatic manifestations in chronic hepatitis C patients.

A liver-specific microRNA, miR-122, is one of the key determinants of hepatitis C virus (HCV) hepatotropism and is required for efficient propagation of HCV. On the other hand, chronic infection with HCV is often associated with extrahepatic manifestations (EHMs), and a low level of HCV-RNA replication has been detected in some non-hepatic cells. Nonetheless, the detailed mechanisms underlying these phenomena remain unknown. Here, we show that miR-122 is dispensable for low-level replication or infectious particle formation, and a mutant virus adapted to miR-122-knockout cells exhibited efficient but miR-122-independent propagation. The adaptive virus of HCV genotype 2a possessed a G28A substitution in the 5’UTR and facilitated efficient replication complex formation under an miR-122-deficient condition, while it propagated at a level comparable to the wild type HCV in the presence of miR-122. Moreover, various adaptive mutations including C30U were introduced into genotype 1b, which originally had an adenine at the nucleotide position 29. These observations suggest that substitutions that yield miR-122-independent propagation are not induced during propagation in hepatocytes; however, treatment with an miR-122 inhibitor or persistent infection of HCV in non-hepatic cells may induce the emergence of mutant viruses, as evidenced by clinical samples.

Quasispecies of Hepatitis C Virus Participate in Cell-Specific Infectivity

It is well documented that a variety of viral quasispecies are found in the patients with chronic infection of hepatitis C virus (HCV). However, the significance of quasispecies in the specific infectivity to individual cell types remains unknown. In the present study, we analyzed the role of quasispecies of the genotype 2a clone, JFH1 (HCVcc), in specific infectivity to the hepatic cell lines, Huh7.5.1 and Hep3B. HCV RNA was electroporated into Huh7.5.1 cells and Hep3B/miR-122 cells expressing miR-122 at a high level. Then, we adapted the viruses to Huh7 and Hep3B/miR-122 cells by serial passages and termed the resulting viruses HCVcc/Huh7 and HCVcc/Hep3B, respectively. Interestingly, a higher viral load was obtained in the homologous combination of HCVcc/Huh7 in Huh7.5.1 cells or HCVcc/Hep3B in Hep3B/miR-122 cells compared with the heterologous combination. By using a reverse genetics system and deep sequence analysis, we identified several adaptive mutations involved in the high affinity for each cell line, suggesting that quasispecies of HCV participate in cell-specific infectivity.

Lipoprotein Receptors Redundantly Participate in Entry of Hepatitis C Virus

Scavenger receptor class B type 1 (SR-B1) and low-density lipoprotein receptor (LDLR) are known to be involved in entry of hepatitis C virus (HCV), but their precise roles and their interplay are not fully understood. In this study, deficiency of both SR-B1 and LDLR in Huh7 cells was shown to impair the entry of HCV more strongly than deficiency of either SR-B1 or LDLR alone. In addition, exogenous expression of not only SR-B1 and LDLR but also very low-density lipoprotein receptor (VLDLR) rescued HCV entry in the SR-B1 and LDLR double-knockout cells, suggesting that VLDLR has similar roles in HCV entry. VLDLR is a lipoprotein receptor, but the level of its hepatic expression was lower than those of SR-B1 and LDLR. Moreover, expression of mutant lipoprotein receptors incapable of binding to or uptake of lipid resulted in no or slight enhancement of HCV entry in the double-knockout cells, suggesting that binding and/or uptake activities of lipid by lipoprotein receptors are essential for HCV entry. In addition, rescue of infectivity in the double-knockout cells by the expression of the lipoprotein receptors was not observed following infection with pseudotype particles bearing HCV envelope proteins produced in non-hepatic cells, suggesting that lipoproteins associated with HCV particles participate in the entry through their interaction with lipoprotein receptors. Buoyant density gradient analysis revealed that HCV utilizes these lipoprotein receptors in a manner dependent on the lipoproteins associated with HCV particles. Collectively, these results suggest that lipoprotein receptors redundantly participate in the entry of HCV.

Hepatitis C virus (HCV) utilizes several receptors to enter hepatocytes, including scavenger receptor class B type 1 (SR-B1) receptor and low-density lipoprotein receptor (LDLR). HCV particles interact with lipoprotein and apolipoproteins to form complexes termed lipoviroparticles. Several reports have shown that SR-B1 and LDLR participate in the entry of lipoviroparticles through interaction with lipoproteins. However, the precise roles of SR-B1 and LDLR in HCV entry have not been fully clarified. In this study, we showed that SR-B1 and LDLR have a redundant role in HCV entry. In addition, we showed that very low-density lipoprotein receptor (VLDLR) played a role in HCV entry similar to the roles of SR-B1 and LDLR. Interestingly, VLDLR expression was low in the liver in contrast to the abundant expressions of SR-B1 and LDLR, but high in several extrahepatic tissues. Our data suggest that lipoprotein receptors participate in the entry of HCV particles associated with various lipoproteins.

Roles of Lipoproteins and Apolipoproteins in Particle Formation of Hepatitis C Virus

More than 160 million people worldwide are infected with hepatitis C virus (HCV), and cirrhosis and hepatocellular carcinoma induced by HCV infection are life-threatening diseases. HCV takes advantage of many aspects of lipid metabolism for an efficient propagation in hepatocytes. Due to the morphological and physiological similarities of HCV particles to lipoproteins, lipid-associated HCV particles are named lipoviroparticles. Recent analyses have revealed that exchangeable apolipoproteins directly interact with the viral membrane to generate infectious HCV particles. In this review, we summarize the roles of lipid metabolism in the life cycle of HCV.

Analysis of the Bombyx mori nucleopolyhedrovirus ie-1 promoter in insect, mammalian, plant, and bacterial cells

The Bombyx mori nucleopolyhedrovirus (BmNPV) ie-1 promoter exhibits strong transcriptional activity and is used in transient foreign gene expression systems in insect cells. In a reporter assay experiment using the BmNPV ie-1 promoter, we found that it exhibited activity even in non-host mammalian BHK cells, plant BY-2 cells, and also bacterial Escherichia coli cells. An analysis using a deletion series of the BmNPV ie-1 promoter demonstrated that the core promoter region of this promoter was sufficient to display promoter activity in BHK cells, BY-2 cells, and E. coli cells, whereas upstream elements were required for higher activity in insect cells. Furthermore, we found that the BmNPV ie-1 promoter exhibited sufficient activity for a β-galactosidase assay in E. coli cells. The results obtained here suggest that the BmNPV ie-1 promoter has potential as a universal promoter for transient expression systems in insect, mammalian, plant, and bacterial cells.

Tightly regulated expression of Autographa californica multicapsid nucleopolyhedrovirus immediate early genes emerges from their interactions and possible collective behaviors

To infect their hosts, DNA viruses must successfully initiate the expression of viral genes that control subsequent viral gene expression and manipulate the host environment. Viral genes that are immediately expressed upon infection play critical roles in the early infection process. In this study, we investigated the expression and regulation of five canonical regulatory immediate-early (IE) genes of Autographa californica multicapsid nucleopolyhedrovirus: ie0, ie1, ie2, me53, and pe38. A systematic transient gene-expression analysis revealed that these IE genes are generally transactivators, suggesting the existence of a highly interactive regulatory network. A genetic analysis using gene knockout viruses demonstrated that the expression of these IE genes was tolerant to the single deletions of activator IE genes in the early stage of infection. A network graph analysis on the regulatory relationships observed in the transient expression analysis suggested that the robustness of IE gene expression is due to the organization of the IE gene regulatory network and how each IE gene is activated. However, some regulatory relationships detected by the genetic analysis were contradictory to those observed in the transient expression analysis, especially for IE0-mediated regulation. Statistical modeling, combined with genetic analysis using knockout alleles for ie0 and ie1, showed that the repressor function of ie0 was due to the interaction between ie0 and ie1, not ie0 itself. Taken together, these systematic approaches provided insight into the topology and nature of the IE gene regulatory network.

High-Level Secretory Production of Phospholipase A1by Saccharomyces cerevisiae and Aspergillus oryzae

Phospholipase A1 (PLA1) is a hydrolytic enzyme that catalyzes the removal of the acyl group from position 1 of lecithin to form lysolecithin. The PLA1 gene, which had been cloned from Aspergillus oryzae, was expressed in Saccharomyces cerevisiae and A. oryzae. Through the modification of the medium composition and the feeding conditions of substrate, the production level of PLA1 by S. cerevisiae was increased to a level fivefold higher than that indicated in a previous report. In the case of A. oryzae, introduction of multicopies of PLA1 expression units, and the morphological change from the pellet form to the filamentous form were effective for the enhancement of PLA1 production. We succeeded in producing 3,500 U/ml of PLA1 using an industrial-scale fermentor.

Baculovirus: an insect-derived vector for diverse gene transfer applications

Insect-derived baculoviruses have emerged as versatile and safe workhorses of biotechnology. Baculovirus expression vectors (BEVs) have been applied widely for crop and forest protection, as well as safe tools for recombinant protein production in insect cells. However, BEVs ability to efficiently transduce noninsect cells is still relatively poorly recognized despite the fact that efficient baculovirus-mediated in vitro and ex vivo gene delivery into dormant and dividing vertebrate cells of diverse origin has been described convincingly by many authors. Preliminary proof of therapeutic potential has also been established in preclinical studies. This review summarizes the advantages and current status of baculovirus-mediated gene delivery. Stem cell transduction, preclinical animal studies, tissue engineering, vaccination, cancer gene therapy, viral vector production, and drug discovery are covered.

Ultrasonic evaluation of the radial artery diameter in a local population from Texas

BACKGROUND

Radial access is the preferred route for cardiac catheterization; however, small radial arterial diameters can make complex procedures difficult. The assessment of radial artery diameters prior to intervention may be beneficial for the interventional cardiologist. Our aim was to measure the diameter of radial arteries in a study sample from our population, and to analyze the feasibility of using larger sheaths for radial interventions.

METHODS

The right radial artery diameter of 100 volunteers was measured using an ultrasound technique. A logistic regression analysis was performed to identify factors associated with small arterial diameters.

RESULTS

The average age of our sample was 35 years, 40% were male, and the mean body mass index (BMI) was 27 kg/m². The mean right arterial diameter for our population was 2.22 ± 0.35 mm. No strong direct association was found between diameters with age, height, weight, and body surface area. Forty-two percent of the patients had diameters larger than 5 Fr sheaths, 20% of the subjects had a diameter larger than 6 Fr sheaths, and 5% of the patients had diameters larger than 7 Fr sheaths. Logistic regression analysis revealed that female volunteers were associated with smaller arterial diameters (odds ratio [OR], 4.0; confidence interval [CI], 1.51-10.51; P=.005), while increases in BMI were associated with larger arterial diameters (OR, 0.21; CI, 0.07-0.61; P=.004).

CONCLUSION

Six Fr sheaths can be used in a significant proportion of our population. Careful selection of male patients with a larger BMI may help the interventionist in advance for planning a radial procedure with larger sheaths.