Measuring of IgG2c isotype instead of IgG2a in immunized C57BL/6 mice with Plasmodium vivax TRAP as a subunit vaccine candidate in order to correct interpretation of Th1 versus Th2 immune response

Immunogenicity of PvCyRPA, PvCelTOS and Pvs25 chimeric recombinant protein of Plasmodium vivax in murine model

In the Americas, P. vivax is the predominant causative species of malaria, a debilitating and economically significant disease. Due to the complexity of the malaria parasite life cycle, a vaccine formulation with multiple antigens expressed in various parasite stages may represent an effective approach. Based on this, we previously designed and constructed a chimeric recombinant protein, PvRMC-1, composed by PvCyRPA, PvCelTOS, and Pvs25 epitopes. This chimeric protein was strongly recognized by naturally acquired antibodies from exposed population in the Brazilian Amazon. However, there was no investigation about the induced immune response of PvRMC-1. Therefore, in this work, we evaluated the immunogenicity of this chimeric antigen formulated in three distinct adjuvants: Stimune, AddaVax or Aluminum hydroxide (Al(OH)3) in BALB/c mice. Our results suggested that the chimeric protein PvRMC-1 were capable to generate humoral and cellular responses across all three formulations. Antibodies recognized full-length PvRMC-1 and linear B-cell epitopes from PvCyRPA, PvCelTOS, and Pvs25 individually. Moreover, mice's splenocytes were activated, producing IFN-γ in response to PvCelTOS and PvCyRPA peptide epitopes, affirming T-cell epitopes in the antigen. While aluminum hydroxide showed notable cellular response, Stimune and Addavax induced a more comprehensive immune response, encompassing both cellular and humoral components. Thus, our findings indicate that PvRMC-1 would be a promising multistage vaccine candidate that could advance to further preclinical studies.

Strategic development of a self-adjuvanting SARS-CoV-2 RBD vaccine: From adjuvant screening to enhanced immunogenicity with a modified TLR7 agonist

Adjuvants enhance the body's immune response to a vaccine, often leading to better protection against diseases. Monophosphoryl lipid A analogues (MPLA, TLR4 agonists), α-galactosylceramide analogues (NKT cell agonists), and imidazoquinoline compounds (TLR7/8 agonists) are emerging novel adjuvants on market or under clinical trials. Despite significant interest in these adjuvants, a direct comparison of their adjuvant activities remains unexplored. We initially assessed the activities of various adjuvants from three distinct categories using the SARS-CoV-2 RBD trimer antigen. TLR4 and TLR7/8 agonists are discovered to elicit robust IgG2a/2b antibodies, which is crucial for eliciting antibody dependent cytotoxicity. While α-galactosylceramide analogs induced mainly IgG1 antibody. Then, because of the flexibility of the TLR7/8 agonist, we designed and synthesized a tri-component self-adjuvanting SARS-CoV-2 RBD vaccine, featuring a covalent TLR7 agonist and targeting mannoside. Animal studies indicated that this vaccine generated antigen-specific humoral immunity. Yet, its immunogenicity seems compromised, indicating the complexity of the vaccine.

Enhanced attenuation of chikungunya vaccines expressing antiviral cytokines

Alphaviruses are vector-borne, medically relevant, positive-stranded RNA viruses that cause disease in animals and humans worldwide. Of this group, chikungunya virus (CHIKV) is the most significant human pathogen, responsible for generating millions of infections leading to severe febrile illness and debilitating chronic joint pain. Currently, there are limited treatments to protect against alphavirus disease; thus, there is a tremendous need to generate safe and effective vaccines. Live-attenuated vaccines (LAVs) are cost-effective and potent immunization strategies capable of generating long-term protection in a single dose. However, LAVs often produce systemic viral replication, which can lead to unwanted post-vaccination side effects and pose a risk of reversion to a pathogenic phenotype and transmission to mosquitoes. Here, we utilized a chimeric infectious clone of CHIKV engineered with the domain C of the E2 gene of Semliki Forest virus (SFV) to express IFNγ and IL-21-two potent antiviral and immunomodulatory cytokines-in order to improve the LAV's attenuation while maintaining immunogenicity. The IFNγ- and IL-21-expressing vaccine candidates were stable during passage and significantly attenuated post-vaccination, as mice experienced reduced footpad swelling with minimal systemic replication and dissemination capacity compared to the parental vaccine. Additionally, these candidates provided complete protection to mice challenged with WT CHIKV. Our dual attenuation strategy represents an innovative way to generate safe and effective alphavirus vaccines that could be applied to other viruses.

Immune Potentiation of PLGA Controlled-Release Vaccines for Improved Immunological Outcomes

With the emergence of SARS-CoV-2 and the continued emergence of new infectious diseases, there is a need to improve and expand current vaccine technology. Controlled-release subunit vaccines provide several benefits over current vaccines on the market, including the use of less antigen and fewer boost doses. Previously, our group reported molecules that alter NF-κB signaling improved the vaccine's performance and improved adjuvant-related tolerability. In this report, we test how these immune potentiators will influence responses when included as part of a controlled-release poly(lactic-co-glycolic) vaccine formulation. Murine in vivo studies revealed that SN50 and honokiol improved antibody levels at early vaccine time points. Microparticles with SN50 produced strong antibody levels over a longer period compared to microparticles without SN50. The same particles also increased T-cell activity. All of the immune potentiators tested further promoted Th2 humoral responses already exhibited by the control CpG OVA microparticle formulation. Overall, under controlled-release conditions, immune potentiators enhance the existing effects of controlled-release formulations, making it a potentially beneficial additive for controlled-release vaccine formulations.

Viral nanoparticle vaccines against S100A9 reduce lung tumor seeding and metastasis

Metastatic cancer accounts for 90% of all cancer-related deaths and continues to be one of the toughest challenges in cancer treatment. A growing body of data indicates that S100A9, a major regulator of inflammation, plays a central role in cancer progression and metastasis, particularly in the lungs, where S100A9 forms a premetastatic niche. Thus, we developed a vaccine against S100A9 derived from plant viruses and virus-like particles. Using multiple tumor mouse models, we demonstrate the effectiveness of the S100A9 vaccine candidates in preventing tumor seeding within the lungs and outgrowth of metastatic disease. The elicited antibodies showed high specificity toward S100A9 without cross-reactivity toward S100A8, another member of the S100A family. When tested in metastatic mouse models of breast cancer and melanoma, the vaccines significantly reduced lung tumor nodules after intravenous challenge or postsurgical removal of the primary tumor. Mechanistically, the vaccines reduce the levels of S100A9 within the lungs and sera, thereby increasing the expression of immunostimulatory cytokines with antitumor function [(interleukin) IL-12 and interferonγ] while reducing levels of immunosuppressive cytokines (IL-10 and transforming growth factorβ). This also correlated with decreased myeloid-derived suppressor cell populations within the lungs. This work has wide-ranging impact, as S100A9 is overexpressed in multiple cancers and linked with poor prognosis in cancer patients. The data presented lay the foundation for the development of therapies and vaccines targeting S100A9 to prevent metastasis.

Engineering Protein Nanoparticles Functionalized with an Immunodominant Coxiella burnetii Antigen to Generate a Q Fever Vaccine

Coxiella burnetii is the causative agent of Q fever, for which there is yet to be an FDA-approved vaccine. This bacterial pathogen has both extra- and intracellular stages in its life cycle, and therefore both a cell-mediated (i.e., T lymphocyte) and humoral (i.e., antibody) immune response are necessary for effective eradication of this pathogen. However, most proposed vaccines elicit strong responses to only one mechanism of adaptive immunity, and some can either cause reactogenicity or lack sufficient immunogenicity. In this work, we aim to apply a nanoparticle-based platform toward producing both antibody and T cell immune responses against C. burnetii. We investigated three approaches for conjugation of the immunodominant outer membrane protein antigen (CBU1910) to the E2 nanoparticle to obtain a consistent antigen orientation: direct genetic fusion, high affinity tris-NTA-Ni conjugation to polyhistidine-tagged CBU1910, and the SpyTag/SpyCatcher (ST/SC) system. Overall, we found that the ST/SC approach yielded nanoparticles loaded with the highest number of antigens while maintaining stability, enabling formulations that could simultaneously co-deliver the protein antigen (CBU1910) and adjuvant (CpG1826) on one nanoparticle (CBU1910-CpG-E2). Using protein microarray analyses, we found that after immunization, antigen-bound nanoparticle formulations elicited significantly higher antigen-specific IgG responses than soluble CBU1910 alone and produced more balanced IgG1/IgG2c ratios. Although T cell recall assays from these protein antigen formulations did not show significant increases in antigen-specific IFN-γ production compared to soluble CBU1910 alone, nanoparticles conjugated with a CD4 peptide epitope from CBU1910 generated elevated T cell responses in mice to both the CBU1910 peptide epitope and whole CBU1910 protein. These investigations highlight the feasibility of conjugating antigens to nanoparticles for tuning and improving both humoral- and cell-mediated adaptive immunity against C. burnetii.

ProLonged Liposomal Delivery of TLR7/8 Agonist for Enhanced Cancer Vaccine

Despite numerous studies on cancer treatment, cancer remains a challenging disease to cure, even after decades of research. In recent years, the cancer vaccine has emerged as a promising approach for cancer treatment, offering few unexpected side effects compared to existing therapies. However, the cancer vaccine faces obstacles to commercialization due to its low efficacy. Particularly, the Toll-like receptor (TLR) adjuvant system, specifically the TLR 7/8 agonist, has shown potential for activating Th1 immunity, which stimulates both innate and adaptive immune responses through T cells. In this study, we developed ProLNG-S, a cholesterol-conjugated form of resiquimod (R848), to enhance immune efficacy by stimulating the immune system and reducing toxicity. ProLNG-S was formulated as ProLNG-001, a positively charged liposome, and co-administered with ovalbumin (OVA) protein in the B16-OVA model. ProLNG-001 effectively targeted secondary lymphoid organs, resulting in a robust systemic anti-tumor immune response and tumor-specific T cell activation. Consequently, ProLNG-001 demonstrated potential for preventing tumor progression and improving survival compared to AS01 by enhancing anti-tumor immunity.

Multivalent vaccines demonstrate immunogenicity and protect against Coxiella burnetii aerosol challenge

Vaccines are among the most cost-effective public health measures for controlling infectious diseases. Coxiella burnetii is the etiological agent of Q fever, a disease with a wide clinical spectrum that ranges from mild symptoms, such as fever and fatigue, to more severe disease, such as pneumonia and endocarditis. The formalin-inactivated whole-cell vaccine Q-VAX® contains hundreds of antigens and confers lifelong protection in humans, but prior sensitization from infection or vaccination can result in deleterious reactogenic responses to vaccination. Consequently, there is great interest in developing non-reactogenic alternatives based on adjuvanted recombinant proteins. In this study, we aimed to develop a multivalent vaccine that conferred protection with reduced reactogenicity. We hypothesized that a multivalent vaccine consisting of multiple antigens would be more immunogenic and protective than a monovalent vaccine owing to the large number of potential protective antigens in the C. burnetii proteome. To address this, we identified immunogenic T and B cell antigens, and selected proteins were purified to evaluate with a combination adjuvant (IVAX-1), with or without C. burnetii lipopolysaccharide (LPS) in immunogenicity studies in vivo in mice and in a Hartley guinea pig intratracheal aerosol challenge model using C. burnetii strain NMI RSA 493. The data showed that multivalent vaccines are more immunogenic than monovalent vaccines and more closely emulate the protection achieved by Q-VAX. Although six antigens were the most immunogenic, we also discovered that multiplexing beyond four antigens introduces detectable reactogenicity, indicating that there is an upper limit to the number of antigens that can be safely included in a multivalent Q-fever vaccine. C. burnetii LPS also demonstrates efficacy as a vaccine antigen in conferring protection in an otherwise monovalent vaccine formulation, suggesting that its addition in multivalent vaccines, as demonstrated by a quadrivalent formulation, would improve protective responses.

Common Variable Immunodeficiency Patient Fecal Microbiota Transplant Recapitulates Gut Dysbiosis

Purpose

Patients with non-infectious complications have worse clinical outcomes in common variable immunodeficiency (CVID) than those with infections-only. Non-infectious complications are associated with gut microbiome aberrations, but there are no reductionist animal models that emulate CVID. Our aim in this study was to uncover potential microbiome roles in the development of non-infectious complications in CVID.

Methods

We examined fecal whole genome shotgun sequencing from patients CVID, and non-infectious complications, infections-only, and their household controls. We also performed Fecal Microbiota transplant from CVID patients to Germ-Free Mice.

Results

We found potentially pathogenic microbes Streptococcus parasanguinis and Erysipelatoclostridium ramosum were enriched in gut microbiomes of CVID patients with non-infectious complications. In contrast, Fusicatenibacter saccharivorans and Anaerostipes hadrus, known to suppress inflammation and promote healthy metabolism, were enriched in gut microbiomes of infections-only CVID patients. Fecal microbiota transplant from non-infectious complications, infections-only, and their household controls into germ-free mice revealed gut dysbiosis patterns in recipients from CVID patients with non-infectious complications, but not infections-only CVID, or household controls recipients.

Conclusion

Our findings provide a proof of concept that fecal microbiota transplant from CVID patients with non-infectious complications to Germ-Free mice recapitulates microbiome alterations observed in the donors.

A Preliminary Study in Immune Response of BALB/c and C57BL/6 Mice with a Locally Allergic Rhinitis Model

BACKGROUND

BALB/c and C57BL/6 mouse strains are commonly used in allergy research. The current study investigated the immunological differences between these two mouse strains with a locally allergic rhinitis model.

METHODS

Eighteen BALB/c and eighteen C57BL/6 mice received different doses of ovalbumin (OVA) intranasally for eight weeks (each mouse strain has three subgroups, 25 mg/mL group, 0.25 mg/mL group, and the PBS group). The allergic symptoms, OVA-specific serum antibody (IgE, IgG1, IgG2a), cytokines (IL-4, IFN-γ, IL-10) in the splenic culture supernatant, infiltrating eosinophils and goblet cells in local nasal mucosa were measured. RNA-seq technology was applied to detect differential gene expression in the local nasal mucosa.

RESULTS

With the same dose of OVA stimulation, the exacerbation of allergic symptoms was more pronounced in C57BL/6 than in BALB/c. BALB/c serum IgE, IgG1, and IgG2a gradually increased, and C57BL/6 produced fewer serum antibodies IgE and IgG1, while IgG2a never increased. BALB/c spleen cell culture supernatant IL-4 and IL-10 increased with increasing dose, and IFN-γ increased significantly in the intermediate dose group, while IL-4, IL-10, and IFN-γ did not increase in C57BL/6. The infiltration of eosinophils and goblet cells in both mice was proportional to the dose, while C57BL/6 was elevated more than BALB/c. RNA-seq suggested that the innate immune response, immune system process function, Jun kinase (JNK) pathway, and MAPKK pathway were upregulated in C57BL/6 compared to BALB/c. The core genes responsible for the differential immune response in both mice with allergic rhinitis were Kng2, Kng1, Gnb3, Lpar3, Lpar1, Pik3r1, Pf4, Apob, Rps9, and Fbxo2.

CONCLUSION

There are significant differences in the immunologic responses between BALB/c mice and C57BL/6 mice. BALB/c mice developed mild local allergic inflammatory reactions and strong systemic immune responses. In contrast, C57BL/6 mice had stronger local allergic inflammatory responses and relatively mild systemic immune responses. Different mice strains can be selected according to the research purpose.

Development of a Modular NTA:His Tag Viral Vaccine for Co-delivery of Antigen and Adjuvant

The SARS-CoV-2 pandemic has highlighted the need for vaccines that are effective, but quickly produced. Of note, vaccines with plug-and-play capabilities that co-deliver antigen and adjuvant to the same cell have shown remarkable success. Our approach of utilizing a nitrilotriacetic acid (NTA) histidine (His)-tag chemistry with viral adjuvants incorporates both of these characteristics: plug-and-play and co-delivery. We specifically utilize the cowpea mosaic virus (CPMV) and the virus-like particles from bacteriophage Qβ as adjuvants and bind the model antigen ovalbumin (OVA). Successful binding of the antigen to the adjuvant/carrier was verified by SDS-PAGE, western blot, and ELISA. Immunization in C57BL/6J mice demonstrates that with Qβ - but not CPMV - there is an improved antibody response against the target antigen using the Qβ-NiNTA:His-OVA versus a simple admixture of antigen and adjuvant. Antibody isotyping also shows that formulation of the vaccines can alter T helper biases; while the Qβ-NiNTA:His-OVA particle produces a balanced Th1/Th2 bias the admixture was strongly Th2. In a mouse model of B16F10-OVA, we further demonstrate improved survival and slower tumor growth in the vaccine groups compared to controls. The NiNTA:His chemistry demonstrates potential for rapid development of future generation vaccines enabling plug-and-play capabilities with effectiveness boosted by co-delivery to the same cell.

A novel defined TLR3 agonist as an effective vaccine adjuvant

Synthetic double-stranded RNA analogs recognized by Toll-like receptor 3 (TLR3) are an attractive adjuvant candidate for vaccines, especially against intracellular pathogens or tumors, because of their ability to enhance T cell and antibody responses. Although poly(I:C) is a representative dsRNA with potent adjuvanticity, its clinical application has been limited due to heterogeneous molecular size, inconsistent activity, poor stability, and toxicity. To overcome these limitations, we developed a novel dsRNA-based TLR3 agonist named NexaVant (NVT) by using PCR-coupled bidirectional in vitro transcription. Agarose gel electrophoresis and reverse phase-HPLC analysis demonstrated that NVT is a single 275-kDa homogeneous molecule. NVT appears to be stable since its appearance, concentration, and molecular size were unaffected under 6 months of accelerated storage conditions. Moreover, preclinical evaluation of toxicity under good laboratory practices showed that NVT is a safe substance without any signs of serious toxicity. NVT stimulated TLR3 and increased the expression of viral nucleic acid sensors TLR3, MDA-5, and RIG-1. When intramuscularly injected into C57BL/6 mice, ovalbumin (OVA) plus NVT highly increased the migration of dendritic cells (DCs), macrophages, and neutrophils into inguinal lymph node (iLN) compared with OVA alone. In addition, NVT substantially induced the phenotypic markers of DC maturation and activation including MHC-II, CD40, CD80, and CD86 together with IFN-β production. Furthermore, NVT exhibited an appropriate adjuvanticity because it elevated OVA-specific IgG, in particular, higher levels of IgG2c (Th1-type) but lower IgG1 (Th2-type). Concomitantly, NVT increased the levels of Th1-type T cells such as IFN-γ⁺CD4⁺ and IFN-γ⁺CD8⁺ cells in response to OVA stimulation. Collectively, we suggest that NVT with appropriate safety and effectiveness is a novel and promising adjuvant for vaccines, especially those requiring T cell mediated immunity such as viral and cancer vaccines.

Comparing the Immunogenicity and Protective Effects of Three MERS-CoV Inactivation Methods in Mice

The Middle East respiratory syndrome (MERS) is a fatal acute viral respiratory disease caused by MERS-coronavirus (MERS-CoV) infection. To date, no vaccine has been approved for MERS-CoV despite continuing outbreaks. Inactivated vaccines are a viable option when developed using the appropriate inactivation methods and adjuvants. In this study, we evaluated the immunogenicity and protective effects of MERS-CoV vaccine candidates inactivated by three different chemical agents. MERS-CoV was effectively inactivated by formaldehyde, hydrogen peroxide, and binary ethylene imine and induced humoral and cellular immunity in mice. Although inflammatory cell infiltration was observed in the lungs four days after the challenge, the immunized hDPP4-transgenic mouse group showed 100% protection against a challenge with MERS-CoV (100 LD50). In particular, the immune response was highly stimulated by MERS-CoV inactivated with formaldehyde, and all mice survived a challenge with the minimum dose. In the adjuvant comparison test, the group immunized with inactivated MERS-CoV and AddaVax had a higher immune response than the group immunized with aluminum potassium sulfate (alum). In conclusion, our study indicates that the three methods of MERS-CoV inactivation are highly immunogenic and protective in mice and show strong potential as vaccine candidates when used with an appropriate adjuvant.

Artificial Cell Membrane Polymersome-Based Intranasal Beta Spike Formulation as a Second Generation Covid-19 Vaccine

Current parenteral coronavirus disease 2019 (Covid-19) vaccines inadequately protect against infection of the upper respiratory tract. Additionally, antibodies generated by wild type (WT) spike-based vaccines poorly neutralize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. To address the need for a second-generation vaccine, we have initiated a preclinical program to produce and evaluate a potential candidate. Our vaccine consists of recombinant Beta spike protein coadministered with synthetic CpG adjuvant. Both components are encapsulated within artificial cell membrane (ACM) polymersomes, synthetic nanovesicles efficiently internalized by antigen presenting cells, including dendritic cells, enabling targeted delivery of cargo for enhanced immune responses. ACM vaccine is immunogenic in C57BL/6 mice and Golden Syrian hamsters, evoking high serum IgG and neutralizing responses. Compared to an ACM-WT spike vaccine that generates predominantly WT-neutralizing antibodies, the ACM-Beta spike vaccine induces antibodies that neutralize WT and Beta viruses equally. Intramuscular (IM)-immunized hamsters are strongly protected from weight loss and other clinical symptoms after the Beta challenge but show delayed viral clearance in the upper airway. With intranasal (IN) immunization, however, neutralizing antibodies are generated in the upper airway concomitant with rapid and potent reduction of viral load. Moreover, antibodies are cross-neutralizing and show good activity against Omicron. Safety is evaluated in New Zealand white rabbits in a repeated dose toxicological study under Good Laboratory Practice (GLP) conditions. Three doses, IM or IN, at two-week intervals do not induce an adverse effect or systemic toxicity. Cumulatively, these results support the application for a Phase 1 clinical trial of ACM-polymersome-based Covid-19 vaccine (ClinicalTrials.gov identifier: NCT05385991).

Local TLR4 stimulation augments in situ vaccination induced via local radiation and anti-CTLA-4 checkpoint blockade through induction of CD8 T-cell independent Th1 polarization

BACKGROUND

Radiation therapy (RT) has been demonstrated to generate an in situ vaccination (ISV) effect in murine models and in patients with cancer; however, this has not routinely translated into enhanced clinical response to immune checkpoint inhibition (ICI). We investigated whether the commonly used vaccine adjuvant, monophosphoryl lipid A (MPL) could augment the ISV regimen consisting of combination RT and ICI.

MATERIALS/METHODS

We used syngeneic murine models of melanoma (B78) and prostate cancer (Myc-CaP). Tumor-bearing mice received either RT (12 Gy, day 1), RT+anti-CTLA-4 (C4, day 3, 6, 9), MPL (20 µg IT injection days 5, 7, 9), RT+C4+MPL, or PBS control. To evaluate the effect of MPL on the irradiated tumor microenvironment, primary tumor with tumor draining lymph nodes were harvested for immune cell infiltration analysis and cytokine profiling, and serum was collected for analysis of antitumor antibody populations.

RESULTS

Combination RT+C4+MPL significantly reduced tumor growth, increased survival and complete response rate compared with RT+C4 in both B78 and Myc-CaP models. MPL favorably reprogrammed the irradiated tumor-immune microenvironment toward M1 macrophage and Th1 TBET+CD4+ T cell polarization. Furthermore, MPL significantly increased intratumoral expression of several Th1-associated and M1-associated proinflammatory cytokines. In co-culture models, MPL-stimulated macrophages directly activated CD8 T cells and polarized CD4 cells toward Th1 phenotype. MPL treatment significantly increased production of Th1-associated, IgG2c antitumor antibodies, which were required for and predictive of antitumor response to RT+C4+MPL, and enabled macrophage-mediated antibody-dependent direct tumor cell killing by MPL-stimulated macrophages. Macrophage-mediated tumor cell killing was dependent on FcγR expression. In metastatic models, RT and MPL generated a systemic antitumor immune response that augmented response to ICIs. This was dependent on macrophages and CD4+ but not CD8+T cells.

CONCLUSIONS

We report the potential for MPL to augment the ISV effect of combination RT+C4 through FcγR, macrophage, and TBET+CD4+ Th1 cell dependent mechanisms. To our knowledge, this is the first report describing generation of a CD8+ T cell-independent, Th1 polarized, systemic antitumor immune response with subsequent generation of immunologic memory. These findings support the potential for vaccine adjuvants to enhance the efficacy of in situ tumor vaccine approaches.

Virus-Like Particle-Templated Silica-Adjuvanted Nanovaccines with Enhanced Humoral and Cellular Immunity

Virus-like particles (VLPs) are self-assembled viral proteins that represent a superior form of antigens in vaccine formulations. To enhance immunogenicity, adjuvants, especially the aluminum salts (Alum), are essentially formulated in VLP vaccines. However, Alum only induce biased humoral immune responses that limits further applications of VLP-based vaccines. To stimulate more balanced immunity, we, herein, develop a one-step strategy of using VLPs as the biotemplates to synthesize raspberry-like silica-adjuvanted VLP@Silica nanovaccines. Hepatitis B surface antigen (HBsAg) VLPs and human papillomavirus type 18 (HPV 18) VLPs are selected as model templates. Circular dichroism (CD) and affinity analyses demonstrate that HBsAg VLPs in the nanovaccines maintain their secondary structure and immunogenicity, respectively. VLP@Silica promote silica dissolution-induced lysosomal escape and cytosolic delivery of antigens, and enhance the secretion of both Th1 and Th2 type cytokines in murine bone marrow-derived dendritic cells (BMDCs). Additionally, they could improve antigen trafficking and mediate DC activation in draining lymph nodes (DLNs). Vaccination study demonstrate that both HBsAg VLP@Silica and HPV 18 VLP@Silica nanovaccines induce enhanced antigen-specific antibody productions and T-cell mediated adaptive immune responses. This design strategy can utilize VLPs derived from a diversity of viruses or their variants as templates to construct both prophylactic and therapeutic vaccines with improved immunogenicity.

R848 Adjuvant Laden With Self-Assembled Nanoparticle-Based mRNA Vaccine Elicits Protective Immunity Against H5N1 in Mice

In order to perfect the design strategy of messenger RNA (mRNA) vaccines against the H5N1 influenza virus, we investigated whether different antigen designs and the use of adjuvants could improve the immune effect of mRNA vaccines. We designed three different forms of antigen genes, including Flu [H1/H3/H5/B-HA2(aa90~105)-M2e(24aa)], Flu-Fe (Fe, ferritin), and CD5-Flu-Fe (CD5, a secretion signal peptide). Meanwhile, R848 (Requimod) was selected as the adjuvant of the mRNA vaccine. We prepared cationic lipid nanoparticles for mRNA delivery, named LNP-Man (mannose-modified lipid nanoparticles). Cell transfection results showed that Flu-Fe/CD5-Flu-Fe containing ferritin could express the target antigens HA2 and M2e more efficiently than Flu. In the mice immune experiment, five immune groups (LNP-Man/Flu, LNP-Man/Flu-Fe, LNP-Man/CD5-Flu-Fe, LNP-Man/Flu-Fe+R848, and LNP-Man/CD5-Flu-Fe+R848) and two control groups (LNP-Man, PBS) were set up. After being infected with the 1×LD50 H5N1 avian influenza virus, the survival rate of the mice in the LNP-Man/CD5-Flu-Fe, LNP-Man/Flu-Fe+R848, and LNP-Man/CD5-Flu-Fe+R848 were 100%. More importantly, in LNP-Man/Flu-Fe+R848 and LNP-Man/CD5-Flu-Fe+R848 groups, there was no residual virus detected in the mice lung tissue on the 5th day postchallenge. Overall, this study provides a new idea for the design of H5N1 avian influenza virus mRNA vaccines in terms of antigen designs and adjuvant selection.

A single dose, BCG-adjuvanted COVID-19 vaccine provides sterilising immunity against SARS-CoV-2 infection

Global control of COVID-19 requires broadly accessible vaccines that are effective against SARS-CoV-2 variants. In this report, we exploit the immunostimulatory properties of bacille Calmette-Guérin (BCG), the existing tuberculosis vaccine, to deliver a vaccination regimen with potent SARS-CoV-2-specific protective immunity. Combination of BCG with a stabilised, trimeric form of SARS-CoV-2 spike antigen promoted rapid development of virus-specific IgG antibodies in the blood of vaccinated mice, that was further augmented by the addition of alum. This vaccine formulation, BCG:CoVac, induced high-titre SARS-CoV-2 neutralising antibodies (NAbs) and Th1-biased cytokine release by vaccine-specific T cells, which correlated with the early emergence of T follicular helper cells in local lymph nodes and heightened levels of antigen-specific plasma B cells after vaccination. Vaccination of K18-hACE2 mice with a single dose of BCG:CoVac almost completely abrogated disease after SARS-CoV-2 challenge, with minimal inflammation and no detectable virus in the lungs of infected animals. Boosting BCG:CoVac-primed mice with a heterologous vaccine further increased SARS-CoV-2-specific antibody responses, which effectively neutralised B.1.1.7 and B.1.351 SARS-CoV-2 variants of concern. These findings demonstrate the potential for BCG-based vaccination to protect against major SARS-CoV-2 variants circulating globally.

Riboflavin as a Mucosal Adjuvant for Nasal Influenza Vaccine

Intranasal immunization with whole inactivated virus (WIV) is an important strategy used for influenza prevention and control. However, a powerful mucosal adjuvant is required to improve nasal vaccine efficacy. Riboflavin, as a food additive with the advantages of being safe and low-cost, widely exists in living organisms. In this paper, the mucosal adjuvant function of riboflavin was studied. After intranasal immunization with H1N1 WIV plus riboflavin in mice, we found that the mucosal immunity based on the secretory IgA (sIgA) levels in the nasal cavity, trachea, and lung were strongly enhanced compared with H1N1 WIV alone. Meanwhile, the IgG, IgG1, and IgG2a levels in serum also showed a high upregulation and a decreased ratio of IgG1/IgG2a, which implied a bias in the cellular immune response. Moreover, riboflavin strongly improved the protection level of H1N1 inactivated vaccine from a lethal influenza challenge. Furthermore, riboflavin was found to possess the capacity to induce dendritic cell (DC) phenotypic (MHCII, CD40, CD80, and CD86) and functional maturation, including cytokine secretion (TNF-α, IL-1β, IL-12p70, and IL-10) and the proliferation of allogeneic T cells. Lastly, we found that the DC maturation induced by riboflavin was dependent on the activation of the mitogen-activated protein kinase (MAPK) signaling pathway, which plays an important role in immune regulation. Therefore, riboflavin is expected to be developed as an alternative mucosal adjuvant for influenza nasal vaccine application.

Yeast Shells Encapsulating Adjuvant AS04 as an Antigen Delivery System for a Novel Vaccine against Toxoplasma Gondii

Toxoplasma gondii (T. gondii) infection causes severe zoonotic toxoplasmosis, which threatens the safety of almost one-third of the human population globally. However, there is no effective protective vaccine against human toxoplasmosis. This necessitates anti-T. gondii vaccine development, which is a main priority of public health. In this study, we optimized the adjuvant system 04 (AS04), a vaccine adjuvant constituted by 3-O-desacyl-4'-monophosphoryl lipid A (a TLR4 agonist) and aluminum salts, by packing it within natural extracts of β-glucan particles (GPs) from Saccharomyces cerevisiae to form a GP-AS04 hybrid adjuvant system. Through a simple mixing procedure, we loaded GP-AS04 particles with the total extract (TE) of T. gondii lysate, forming a novel anti-T. gondii vaccine GP-AS04-TE. Results indicated that the hybrid adjuvant can efficiently and stably load antigens, mediate antigen delivery, facilitate the dendritic uptake of antigens, boost dendritic cell maturation and stimulation, and increase the secretion of pro-inflammatory cytokines. In the mouse inoculation model, GP-AS04-TE significantly stimulated the function of dendritic cells, induced a very strong TE-specific humoral and cellular immune response, and finally showed a strong and effective protection against toxoplasma chronic and acute infections. This work proves the potential of GP-AS04 for exploitation as a vaccine against a range of pathogens.

T-bet represses collagen-induced arthritis by suppressing Th17 lineage commitment through inhibition of RORγt expression and function

T-bet is a key transcription factor for the T helper 1 lineage and its expression level is negatively correlated to inflammation in patients with rheumatoid arthritis (RA). Our previous study using T-bet transgenic mice revealed over-expression of T-bet completely suppressed collagen-induced arthritis (CIA), a murine model of RA, indicating a potential suppressive role of T-bet in the pathogenesis of autoimmune arthritis. Here, we show T-bet-deficiency exacerbated CIA. T-bet in CD4 + T cells, but not in CD11c + dendritic cells, was critical for regulating the production of IL-17A, IL-17F, IL-22, and TNFα from CD4 + T cells. T-bet-deficient CD4 + T cells showed higher RORγt expression and increased IL-17A production in RORγt-positive cells after CII immunization. In addition, T-bet-deficient naïve CD4 + T cells showed accelerated Th17 differentiation in vitro. CIA induced in CD4-Cre T-bet^fl/fl (cKO) mice was more severe and T-bet-deficient CD4 + T cells in the arthritic joints of cKO mice showed higher RORγt expression and increased IL-17A production. Transcriptome analysis of T-bet-deficient CD4 + T cells revealed that expression levels of Th17-related genes were selectively increased. Our results indicate that T-bet in CD4 + T cells repressed RORγt expression and function resulting in suppression of arthritogenic Th17 cells and CIA.

Multicomponent Gold-Linked Glycoconjugate Vaccine Elicits Antigen-Specific Humoral and Mixed TH1-TH17 Immunity, Correlated with Increased Protection against Burkholderia pseudomallei

Burkholderia pseudomallei is the causative agent of melioidosis, a fatal disease with a high mortality rate. The intrinsic resistance to commonly used antibiotics combined with the complex bacterial life cycle has hampered the development of preventive and therapeutic interventions and vaccines. Furthermore, the need of humoral and cell-mediated immunity in protection against B. pseudomallei has complicated the development of effective vaccines. Antigen delivery vaccine platforms that promote humoral and cellular responses while maintaining a safe profile are a roadblock to developing subunit vaccines against intracellular pathogens. Gold nanoparticles (AuNPs) were used for the delivery of multicomponent antigens with the goal of inducing vaccine-mediated immunity, promoting protection against melioidosis disease. Different nanoglycoconjugates using predicted immunogenic protein candidates, Hcp1, FlgL, OpcP, OpcP1, OmpW, and hemagglutinin, were covalently coupled to AuNPs, together with the lipopolysaccharide (LPS) from Burkholderia thailandensis, which acted as an additional antigen. Animals immunized with individually coupled (AuNP-protein-LPS) formulations containing OpcP or OpcP1, together with CpG as an adjuvant, showed a significant increase in protection, whereas a nanovaccine combination (AuNP-Combo2-LPS) showed significant and complete protection against a lethal intranasal B. pseudomallei challenge. Animals immunized with AuNP-Combo2-LPS showed robust humoral antigen-specific (IgG and IgA) responses with higher IgG2c titer, indicating a T_H1-skewed response and promotion of macrophage uptake. In addition, immunization with the nanovaccine combination resulted in a mixed antigen-specific T_H1-T_H17 cytokine profile after immunization. This study provides the basis for an elegant and refined multicomponent glycoconjugate vaccine formulation capable of eliciting both humoral and cell-mediated responses against lethal B. pseudomallei challenge.

Multicomponent gold nano-glycoconjugate as a highly immunogenic and protective platform against Burkholderia mallei

Burkholderia mallei (Bm) is a facultative intracellular pathogen and the etiological agent of glanders, a highly infectious zoonotic disease occurring in equines and humans. The intrinsic resistance to antibiotics, lack of specific therapy, high mortality, and history as a biothreat agent, prompt the need of a safe and effective vaccine. However, the limited knowledge of protective Bm-specific antigens has hampered the development of a vaccine. Further, the use of antigen-delivery systems that enhance antigen immunogenicity and elicit robust antigen-specific immune responses has been limited and could improve vaccines against Bm. Nanovaccines, in particular gold nanoparticles (AuNPs), have been investigated as a strategy to broaden the repertoire of vaccine-mediated immunity and as a tool to produce multivalent vaccines. To synthesize a nano-glycoconjugate vaccine, six predicted highly immunogenic antigens identified by a genome-wide bio- and immuno-informatic analysis were purified and coupled to AuNPs along with lipopolysaccharide (LPS) from B. thailandensis. Mice immunized intranasally with individual AuNP-protein-LPS conjugates, showed variable degrees of protection against intranasal Bm infection, while an optimized combination formulation (containing protein antigens OmpW, OpcP, and Hemagglutinin, along with LPS) showed complete protection against lethality in a mouse model of inhalational glanders. Animals immunized with different nano-glycoconjugates showed robust antigen-specific antibody responses. Moreover, serum from animals immunized with the optimized nano-glycoconjugate formulation showed sustained antibody responses with increased serum-mediated inhibition of adherence and opsonophagocytic activity in vitro. This study provides the basis for the rational design and construction of a multicomponent vaccine platform against Bm.