Correction: A vesicular stomatitis virus-based prime-boost vaccination strategy induces potent and protective neutralizing antibodies against SARS-CoV-2.

[This corrects the article DOI: 10.1371/journal.ppat.1010092.].

A vesicular stomatitis virus-based prime-boost vaccination strategy induces potent and protective neutralizing antibodies against SARS-CoV-2.

The development of safe and effective vaccines to prevent SARS-CoV-2 infections remains an urgent priority worldwide. We have used a recombinant vesicular stomatitis virus (rVSV)-based prime-boost immunization strategy to develop an effective COVID-19 vaccine candidate. We have constructed VSV genomes carrying exogenous genes resulting in the production of avirulent rVSV carrying the full-length spike protein (SF), the S1 subunit, or the receptor-binding domain (RBD) plus envelope (E) protein of SARS-CoV-2. Adding the honeybee melittin signal peptide (msp) to the N-terminus enhanced the protein expression, and adding the VSV G protein transmembrane domain and the cytoplasmic tail (Gtc) enhanced protein incorporation into pseudotype VSV. All rVSVs expressed three different forms of SARS-CoV-2 spike proteins, but chimeras with VSV-Gtc demonstrated the highest rVSV-associated expression. In immunized mice, rVSV with chimeric S protein-Gtc derivatives induced the highest level of potent neutralizing antibodies and T cell responses, and rVSV harboring the full-length msp-SF-Gtc proved to be the superior immunogen. More importantly, rVSV-msp-SF-Gtc vaccinated animals were completely protected from a subsequent SARS-CoV-2 challenge. Overall, we have developed an efficient strategy to induce a protective response in SARS-CoV-2 challenged immunized mice. Vaccination with our rVSV-based vector may be an effective solution in the global fight against COVID-19.

Pharmaceutical and Immunological Evaluation of Cholera Toxin A1 Subunit as an Adjuvant of Hepatitis B Vaccine Microneedles.

PURPOSE: For successful delivery of a solid vaccine formulation into the skin using microneedles, the solubility of an adjuvant should be considered because the decrease in the dissolution rate by the addition of adjuvant decreases the delivery efficiency of the vaccine. METHODS: In this study, cholera toxin A subunit 1 (CTA1) was examined as an adjuvant to Hepatitis B vaccine (HBV) microneedles because of its good water solubility, improved safety, and positive effect as shown in intramuscular administration of a liquid vaccine. RESULTS: All solid formulations with CTA 1 dissolved in in vivo mouse skin within 30 min, and they were successfully delivered into the skin. In experiments with mice, the addition of CTA1 led to improved IgG immune response compared to the use of an aluminum hydroxide-based formulation and intramuscular administration of HBV. In addition, CTA1 induced CD8 + T cell response as much as in which the aluminum hydroxide-based formulation induced. CONCLUSIONS: CTA1 is an adjuvant that satisfies both the delivery efficiency and the immunological characteristics required for vaccine microneedles. CTA1 will be used as a potential adjuvant through vaccine microneedles.

Cross-Protection against MERS-CoV by Prime-Boost Vaccination Using Viral Spike DNA and Protein.

Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe respiratory illness and has a high mortality of ∼34%. However, since its discovery in 2012, an effective vaccine has not been developed for it. To develop a vaccine against multiple strains of MERS-CoV, we targeted spike glycoprotein (S) using prime-boost vaccination with DNA and insect cell-expressed recombinant proteins for the receptor-binding domain (RBD), S1, S2, SΔTM, or SΔER. Our S subunits were generated using an S sequence derived from the MERS-CoV EMC/2012 strain. We examined humoral and cellular immune responses of various combinations with DNA plasmids and recombinant proteins in mice. Mouse sera immunized with SΔER DNA priming/SΔTM protein boosting showed cross-neutralization against 15 variants of S-pseudovirions and the wild-type KOR/KNIH/002 strain. In addition, these immunizations provided full protection against the KOR/KNIH/002 strain challenge in human DPP4 knock-in mice. These findings suggest that vaccination with the S subunits derived from one viral strain can provide cross-protection against variant MERS-CoV strains with mutations in S. DNA priming/protein boosting increased gamma interferon production, while protein-alone immunization did not. The RBD subunit alone was insufficient to induce neutralizing antibodies, suggesting the importance of structural conformation. In conclusion, heterologous DNA priming with protein boosting is an effective way to induce both neutralizing antibodies and cell-mediated immune responses for MERS-CoV vaccine development. This study suggests a strategy for selecting a suitable platform for developing vaccines against MERS-CoV or other emerging coronaviruses.IMPORTANCE Coronavirus is an RNA virus with a higher mutation rate than DNA viruses. Therefore, a mutation in S-protein, which mediates viral infection by binding to a human cellular receptor, is expected to cause difficulties in vaccine development. Given that DNA-protein vaccines promote stronger cell-mediated immune responses than protein-only vaccination, we immunized mice with various combinations of DNA priming and protein boosting using the S-subunit sequences of the MERS-CoV EMC/2012 strain. We demonstrated a cross-protective effect against wild-type KOR/KNIH/002, a strain with two mutations in the S amino acids, including one in its RBD. The vaccine also provided cross-neutralization against 15 different S-pseudotyped viruses. These suggested that a vaccine targeting one variant of S can provide cross-protection against multiple viral strains with mutations in S. The regimen of DNA priming/Protein boosting can be applied to the development of other coronavirus vaccines.

Real-Time Internal Steam Pop Detection during Radiofrequency Ablation with a Radiofrequency Ablation Needle Integrated with a Temperature and Pressure Sensor: Preclinical and Clinical Pilot Tests.

A radiofrequency ablation (RFA) needle integrated with a temperature sensor (T-sensor) and pressure sensor (P-sensor) is designed and utilized for real-time internal steam pop monitoring during RFA. The characteristics of the sensor-integrated RFA needle (sRFA-needle) are investigated quantitatively using a pressure chamber system, and the feasibility and usability of the needle in preclinical and clinical trials is demonstrated. The sharp changes in the temperature and normalized pressure sensor signals induced by the abrupt release of hot and high-pressure steam can be clearly monitored during the steam pop phenomena. The basic mechanism of the preliminary steam pop is hypothesized and verified using in situ ultrasound imaging data and computational analysis data of the RFA procedure. Moreover, the usability of the system in clinical trials is investigated, and the steam pop phenomena during the RFA procedure are detected using T-sensor and P-sensor. The results confirm that the sensor integration on the medical needle can provide critical data for safer and more effective medical practices.

Microneedles with dual release pattern for improved immunological efficacy of Hepatitis B vaccine.

In this study, dissolving microneedles (DMNs) with dual-release pattern, capable of both bolus release and slow release, were prepared. These DMNs were used with a hepatitis B vaccine that requires multiple shots to achieve immunological efficacy comparable to that obtained when two separate shots are administered. Dissolving microneedles with HBsAg in PLA tips and CMC coating formulation together (HBsAg-PLA/CMC-DMNs) consist of polylactic acid (PLA) tips for slow release, a carboxy-methyl cellulose (CMC) coating formulation for bolus release, and a dissolving base of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) for dissolution in the skin. The in vitro release pattern of HBsAg from the CMC coating formulation and PLA tips was observed. Through an in vivo test, 1) the delivery efficiency of HBsAg-PLA/CMC-DMNs was observed, and 2) the immunological efficacy of this method was compared with the efficacy of two shots delivered by conventional intramuscular (IM) administration and two shots delivered by HBsAg-coated microneedle (CMNs) administration. HBsAg-PLA/CMC-DMNs punctured the skin successfully. The PVA/PVP base was completely dissolved within 10 min of insertion, resulting in the delivery of all microneedle tips into the skin. In the in vitro release experiment, all of the HBsAg in the CMC coating formulation was released within 20 min, and the HBsAg present in the PLA tips was gradually released over more than 55 days. The antibody titer of one shot of HBsAg-PLA/CMC-DMNs was the same as or higher than two shots delivered by conventional IM and CMN methods. DMNs with dual-release pattern can deliver two formulations simultaneously with a single shot, resulting in improved immunological efficacy of HBsAg that requires multiple doses. In addition, this dual-release MN system can be used for the delivery of other drugs that require multiple administrations.

Broader neutralization of CT-P27 against influenza A subtypes by combining two human monoclonal antibodies.

There are several broadly neutralizing monoclonal antibodies that neutralize influenza viruses with different mechanisms from traditional polyclonal antibodies induced by vaccination. CT149, which is one of the broadly neutralizing antibodies, was also previously reported to neutralize group 2 and some of group 1 influenza viruses (13 out of 13 tested group 2 viruses and 5 out of 11 group 1 viruses). In this study, we developed another antibody with the aim of compensating partial coverage of CT149 against group 1 influenza viruses. CT120 was screened among different antibody candidates and mixed with CT149. Importantly, although the binding sites of CT120 and CT149 are close to each other, the two antibodies do not interfere. The mixture of CT120 and CT149, which we named as CT-P27, showed broad efficacy by neutralizing 37 viruses from 11 different subtypes, of both group 1 and 2 influenza A viruses. Moreover, CT-P27 showed in vivo therapeutic efficacy, long prophylactic potency, and synergistic effect with oseltamivir in influenza virus-challenged mouse models. Our findings provide a novel therapeutic opportunity for more efficient treatment of influenza.

Skin immunization with third-generation hepatitis B surface antigen using microneedles.

L-HBsAg is a third-generation hepatitis vaccine capable of inducing antibodies in non-responders and thus providing potentially therapeutic treatment. In this study, L-HBsAg was administered using microneedles (MN) without an adjuvant to induce intradermal (ID) immunization, and the efficacy of ID immunization was compared with that of intramuscular (IM) immunization that uses a conventional formulation with an adjuvant of aluminum hydroxide (L-HBsAg-AL-IM). The L-HBsAg was dip-coated onto 800-µm-long microneedles made of polylactic acid (PLA). Delivery efficiency and administration time were determined through in vitro experiments using porcine skin. The denaturation of the formulation against sterilization by gamma rays was observed. A storage test and a freeze-thaw cycle test of the microneedles with trehalose as a stabilizer (L-HBsAg-MN-Tre) were observed. An antibody titer of L-HBsAg-MN-Tre was compared with that of the conventional IM immunization of the L-HBsAg solution with aluminum hydroxide (L-HBsAg-AL-IM). The formulation containing L-HBsAg was located on the upper third of the microneedle tips. The formulation on the MN was dissolved and delivered within 30 min of insertion into porcine skin in vitro. Trehalose was selected as a stabilizer, and the stabilizing effect increased with the increase of trehalose content in the solidified formulation. L-HBsAg-MN with 15% of trehalose was stable for 7 days at 40 °C and showed increased stability compared to the conventional liquid formulations. L-HBsAg-MN-Tre showed improved stability during the freeze-thaw cycle. The antibody titer of L-HBsAg-MN-Tre at 28 days was higher than that of L-HBsAg-AL-IM. ID administration of L-HBsAg-MN-Tre showed better efficacy and improved thermal and freeze thaw stability compared to L-HBsAg-AL-IM. Therefore, L-HBsAg-MN-Tre administration showed the possibility of ID delivery of L-HBsAg without the use of an adjuvant for the efficacy, convenience, and safety of pediatric vaccination.

Heat-Killed Saccharomyces cerevisiae, A Dectin-1 Agonist, Selectively Induces IgG4 Production by Human B Cells.

Dectin-1 is a major receptor that recognizes fungal cell wall ß-glucan. We previously reported that heat-killed Saccharomyces cerevisiae (HKSC), a Dectin-1 agonist, selectively induces IgG1 class switching in mouse B cells. Dectin-1 is also expressed on human B cells; however, Dectin-1 function in human B cells remains unknown. This study aimed to investigate the direct effect of in vitro stimulation using HKSC on Ig class switching in human B cells. HKSC selectively induced the expression of germline γ4 transcripts (GLTγ4) by human B cell line 2E2, and HKSC significantly augmented GLTγ4 promoter activity. Moreover, HKSC selectively enhanced GLTγ4 expression and IgG4 production by anti-CD40-activated human tonsillar resting B cells. Thus, these results suggest that Dectin-1 maybe involved in selective IgG4 class switching by human B cells.

Aberrant expression of interleukin-10 and activation-induced cytidine deaminase in B cells from patients with Behçet's disease.

Despite extensive studies, the pathogenesis of Behçet's disease (BD) remains unclear. In particular, the roles of B cells in patients with BD have not been elucidated. Activation-induced cytidine deaminase (AID) is a critical enzyme for immunoglobulin (Ig) heavy chain class switching and somatic hypermutation in B cells and the abnormal expression of AID in various immune conditions has previously been studied. B10 cells, an interleukin (IL)-10-secreting subset of regulatory B cells, function to downregulate inflammation and autoimmunity. Thus, in the present study, the relevance of B cells in patients with BD was investigated. The plasma levels of IL-10 and IgA and the proportions of cluster of differentiation (CD)43+ B cells, excluding naïve B cells, were measured in 16 patients with BD and 16 age- and sex-matched healthy controls (HCs). Additionally, the mRNA levels of IL-10 and AID were assessed in B cells from fresh peripheral blood samples of the BD patients and HCs. The plasma level of IL-10 in patients with BD did not differ significantly from that in HCs. Similarly, there was no significant difference in the plasma level of IgA, although a slight increase was observed in patients with BD compared with that in HCs. There were no differences in CD43+CD19+ B cell numbers between patients with BD and HCs. However, IL-10 mRNA levels were significantly reduced (P<0.05), while AID mRNA levels were significantly increased (P<0.01) in the B cells of patients with BD compared with those in HCs. These results provide insight into the role of B cells in patients with BD.

Dectin-1 agonist selectively induces IgG1 class switching by LPS-activated mouse B cells.

Heat-killed Saccharomyces cerevisiae (HKSC) is an agonist for Dectin-1, a major fungal cell wall ß-glucan receptor. We previously reported that HKSC selectively enhances IgG1 production by LPS-activated mouse B cells. To determine if this IgG1 selectivity is caused by selective IgG1 class switching, we performed RT-PCRs for measuring germline transcripts (GLTs), flow cytometric analyses for detecting Ig-expressing cells, and ELISPOT assays for measuring the number of Ig-secreting cells in HKSC/LPS-stimulated mouse B cell cultures. HKSC selectively enhanced expression of GLTγ1, the number of IgG1-expressing cells, and the number of IgG1-secreting B cells in the presence of LPS stimulation. In addition, HKSC induced the expression of CD69, an activation marker for B lymphocytes, and the expression of surface Dectin-1. Two Dectin-1 antagonists, laminarin and a neutralizing Dectin-1 antibody, selectively diminished HKSC-reinforced IgG1 production by LPS-stimulated B cells. Furthermore, depleted zymosan (dzn), a Dectin-1 agonist with increased selectivity, also selectively enhanced GLTγ1 transcription. The Dectin-1 antagonists blocked dzn-induced IgG1 production by LPS-activated B cells. Collectively, these results suggest that Dectin-1 agonists selectively induce IgG1 class switching by direct stimulation of Dectin-1 on LPS-activated B cells resulting in selective production of IgG1.

Ginsenoside Rg1 and 20(S)-Rg3 Induce IgA Production by Mouse B Cells.

Ginsenosides are the major components of ginseng, which is known to modulate blood pressure, metabolism, and immune function, and has been used to treat various diseases. It has been reported that ginseng and several ginsenosides have immunoregulatory effects on the innate and T cell-mediated immune response. However, their effects on the humoral immune response have not been fully explored. The present study examined the direct effects of red ginseng extract (RGE) and ginsenosides on mouse B cell proliferation and on antibody production and the expression of germline transcripts (GLT) by mouse B cells in vitro. RGE slightly reduced B cell proliferation, but increased IgA production by LPS-stimulated B cells. Furthermore, ginsenoside Rg1 and 20(S)-Rg3 selectively induced IgA production and expression of GLTα transcripts by LPS-stimulated B cells. Collectively, these results suggest that ginsenoside Rg1 and 20(S)-Rg3 can drive the differentiation of B cells into IgA-producing cells through the selective induction of GLTα expression.

Characterization and cDNA cloning of a defensin-like peptide, harmoniasin, from Harmonia axyridis.

We compared the mRNA expression profile of the Harmonia axyridis larvae that were either untreated or treated with LPS. The extracted mRNAs were subjected to ACP RTPCR analysis using a combination of arbitrary primers and oligo (dT) primer. Among the 47 DEGs differentially expressed, we identified a cDNA showing homology with defensin-like antibacterial peptide. The cDNA showed a putative 32-residue signal sequence and a 50-residue mature peptide named harmoniasin. We also investigated the antibacterial activity of the harmoniasin analog, which exhibited potent antibacterial activities against Gramnegative and -positive bacteria strains and it also evidenced no hemolytic activity.