SARS-CoV-2 mRNA Vaccines Foster Potent Antigen-Specific Germinal Center Responses Associated with Neutralizing Antibody Generation

Looking beyond the origin of SARS-CoV-2: Significant strategic aspects during the five-year journey of COVID-19 vaccine development

It has been five years since the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and we are also approaching the five-year mark of the COVID-19 pandemic. The vaccine is a significant weapon in combating infectious diseases like SARS-CoV-2. Several vaccines were developed against SARS-CoV-2, and they demonstrated efficacy and safety during these five years. The rapid development of multiple next-generation vaccine candidates in different platforms with very little time is the success story of the vaccine development endeavor. This remarkable success of rapid vaccine development is a new paradigm for fast vaccine development that might help develop infectious diseases and fight against the pandemic. With the completion of five years since the beginning of SARS-CoV-2 origin, we are looking back on the five years and reviewing the milestones, vaccine platforms, animal models, clinical trials, successful collaborations, vaccine safety, real-world effectiveness, and challenges. Lessons learned during these five years will help us respond to public health emergencies and to fight the battle against future pandemics.

A recombinant BCG with surface-displayed antigen induces humoral and cellular immune responses

Bacillus Calmette-Guérin (BCG) is an attenuated vaccine widely used for tuberculosis prevention. While BCG has long been perceived as an intracellular candidate vector for delivering antigens against infectious diseases and cancers, challenges persist in inducing durable immune responses, particularly high-titer neutralizing antibodies (Nabs). Here we show that displaying antigens in the surface of BCG is a promising strategy to induce long-lasting Nabs production and T-cell responses. We constructed a recombinant BCG expressing the SARS-CoV-2 receptor-binding domain (RBD) antigen on its cell wall, termed CW-rBCG::RBD, which achieved an antigen yield approaching 850 nanograms per 107 colony-forming unit. Compared with both the parental BCG and the RBD protein subunit vaccine (RBDAS01), intravenous administration of CW-rBCG::RBD followed by a booster dose significantly enhanced Nab production and increased the frequencies of RBD-specific central memory T cells (Tcm) and T follicular helper (Tfh) cells in the spleen. In mice primed with a single dose of CW-rBCG::RBD and boosted with RBDAS01, we also observed elevated Nab titers and detectable levels of RBD-specific IgG2a antibodies at 8 weeks post-priming, responses that were not observed in the BCG-primed or RBDAS01-only groups. Furthermore, subcutaneous co-administration of CW-rBCG::RBD and RBDAS01 sustained Nab production for up to 31 weeks and maintained higher Tfh and Tcm cell frequencies compared to both BCG co-administration with RBDAS01 and RBDAS01 alone. These findings highlight an effective strategy for optimizing BCG-based vaccination and immunotherapy platforms. Subject terms: recombinant BCG; immune response; vaccines; cell wall; SARS-CoV-2 RBD.

Increased STAT3 Phosphorylation in CD4+ T-Cells of Treated Patients with Chronic Lymphocytic Leukemia and Changes in Circulating Regulatory T-Cell Subsets Relative to Tumor Mass Distribution Value and Disease Duration

Introduction: In mouse models of chronic lymphocytic leukemia (CLL), an effective anti-leukemia immune response was obtained by depleting a specific regulatory T-cell (Treg) subset. While STAT5 signaling could alter the homeostasis of naïve (nTreg) and activated (aTreg) subsets, which are capable of suppressing also CLL patients' responses to microbial antigens, perturbed STAT3 signaling could drive CXCR5 expression in circulating T-follicular regulatory cells (Tfr) and their entry into the lymph node/tumor microenvironment. Materials and Methods: By using phospho-specific flow cytometry, we monitored STAT signaling/phosphorylation (pSTAT), in vitro responses to Sars-Cov2-antigen-specific stimulation, and circulating Treg subsets in relation to Binet stage and total tumor mass/tumor distribution (TTM/TD) scoring in 62 patients with CLL. Results: The percentage of CXCR5+ Treg significantly increased in patients with Binet stage B disease, and Tfr-like subsets were associated with higher TTM and lower TD. The pSTAT3 levels in CD4+ T-cells were only significantly increased in patients undergoing therapy. Lower nTreg percentages correlated with increased disease duration, and an increased aTreg/nTreg ratio correlated with SARS-CoV-2-antigen-induced STAT5 signaling responses. Conclusions: The results show increased amounts of circulating CXCR5+ Tfr-like subsets in patients with extensive lymph node involvement and augmented STAT3 signaling in patients on therapy. While STAT5 responses may drive nTreg differentiation into aTreg, nTreg decline is associated with increased disease duration.

Mucosal unadjuvanted booster vaccines elicit local IgA responses by conversion of pre-existing immunity in mice

Mucosal delivery of vaccine boosters induces robust local protective immune responses even without any adjuvants. Yet, the mechanisms by which antigen alone induces mucosal immunity in the respiratory tract remain unclear. Here we show that an intranasal booster with an unadjuvanted recombinant SARS-CoV-2 spike protein, after intramuscular immunization with 1 μg of mRNA-LNP vaccine encoding the full-length SARS-CoV-2 spike protein (Pfizer/BioNTech BNT162b2), elicits protective mucosal immunity by retooling the lymph node-resident immune cells. On intranasal boosting, peripheral lymph node-primed B cells rapidly migrated to the lung through CXCR3-CXCL9 and CXCR3-CXCL10 signaling and differentiated into antigen-specific IgA-secreting plasma cells. Memory CD4+ T cells in the lung served as a natural adjuvant for developing mucosal IgA by inducing the expression of chemokines CXCL9 and CXCL10 for memory B cell recruitment. Furthermore, CD40 and TGFβ signaling had important roles in mucosal IgA development. Repeated mucosal boosting with an unadjuvanted protein amplified anamnestic IgA responses in both the upper and the lower respiratory tracts. These findings help explain why nasal boosters do not require an adjuvant to induce robust mucosal immunity at the respiratory mucosa and can be used to design safe and effective vaccines against respiratory pathogens.

An mRNA vaccine provides effective protection against Duck Tembusu Virus infection

As an emerging flavivirus, Duck Tembusu virus (DTMUV) causes severe neurological disorder and acute egg drop syndrome in poultry. Herein, we report the development of a highly effective mRNA vaccine against DTMUV using lipid nanoparticle (LNP) delivery technology. We engineered an mRNA construct encoding the pre-membrane (prM) and envelope (E) proteins of DTMUV, with an upstream signal peptide to enhance secretion. Two doses of our mRNA vaccine elicited robust neutralizing antibody titers and conferred 100% protection against challenge with a prevalent virulent DTMUV strain. Notably, in a head-to-head comparison, the neutralizing antibody titers induced by our mRNA vaccine were approximately 40-fold of a commercial live-attenuated vaccine (FX2010-180P). Importantly, our mRNA vaccine demonstrated efficient maternal antibody transfer via egg yolk deposition, indicating the potential for protecting offspring through maternal immunity. These findings demonstrate the superiority of our mRNA vaccine platform, as well as the feasibility of applying mRNA vaccines in poultry.

A T7 autogene-mediated DNA vaccine platform for SARS-CoV-2: Overcoming DNA vaccine limitations with enhanced spike mRNA production

The COVID-19 pandemic has underscored the urgent need for innovative vaccine platforms that combine potent immunogenicity, thermal stability, and global accessibility. While mRNA vaccines have proven highly efficacious, their fragility and reliance on ultracold storage complicates distribution in resource-constrained settings. DNA vaccines, by contrast, are more stable and easier to distribute but suffer from low immunogenicity due to inefficient nuclear translocation. Here, we introduce the mRNA Factory (mRF) vaccine platform, a DNA-based system that enables direct cytoplasmic transcription of spike mRNA via self-amplifying T7 RNA polymerase. The Rpol/spk mRF vaccine elicited markedly enhanced immunogenicity compared to conventional plasmid DNA vaccines, as evidenced by elevated spike protein expression, robust T cell activation, Th1-biased cytokine profiles, and higher titers of SARS-CoV-2-specific IgG. Compared with an IVT spike mRNA vaccine, the mRF vaccine elicited comparable levels of overall immune responses, including T effector cell activation, IFNγ+CD8+ cytotoxic T cell activation, Th1 polarization, and specific IgG production. These results highlight the mRF platform's potential to overcome key limitations of conventional DNA vaccines while addressing distribution challenges associated with mRNA vaccines. Our findings support the mRF platform as a promising strategy for global vaccine deployment and future pandemic preparedness.

Modulation of lipid nanoparticle-formulated plasmid DNA drives innate immune activation promoting adaptive immunity

Nucleic acid vaccines have grown in importance over the past several years, with the development of new approaches remaining a focus. We describe a lipid nanoparticle-formulated DNA (DNA-LNP) formulation which induces robust innate and adaptive immunity with similar serological potency to mRNA-LNPs and adjuvanted protein. Using an influenza hemagglutinin (HA)-encoding construct, we show that priming with our HA DNA-LNP demonstrated stimulator of interferon genes (STING)-dependent upregulation and activation of migratory dendritic cell (DC) subpopulations. HA DNA-LNP induced superior antigen-specific CD8+ T cell responses relative to mRNA-LNPs or adjuvanted protein, with memory responses persisting beyond one year. In rabbits immunized with HA DNA-LNP, we observed immune responses comparable or superior to mRNA-LNPs at the same dose. In an additional model, a SARS-CoV-2 spike-encoding DNA-LNP elicited protective efficacy comparable to spike mRNA-LNPs. Our study identifies a platform-specific priming mechanism for DNA-LNPs divergent from mRNA-LNPs or adjuvanted protein, suggesting avenues for this approach in prophylactic and therapeutic vaccine development.

COVID-19 vaccination and pregnancy-induced hypertension risk in women undergoing assisted reproduction

STUDY QUESTION

Does COVID-19 vaccination affect the risk of pregnancy-induced hypertension (PIH) in women undergoing ARTs, and does this risk differ based on vaccine type (inactivated vs recombinant) and timing relative to embryo transfer?

SUMMARY ANSWER

Women who received inactivated COVID-19 vaccines before undergoing ART had a significantly increased risk of developing PIH, particularly when vaccinated with two or more doses or when embryo transfer occurred within 1 month of vaccination.

WHAT IS KNOWN ALREADY

COVID-19 vaccination during pregnancy reduces the risk of severe COVID-19 illness with no significant safety concerns for the mother or fetus. PIH is a common complication in ART pregnancies, particularly in older women and those with higher BMI, but the effects of different COVID-19 vaccine types on PIH risk in ART pregnancies remain unclear.

STUDY DESIGN, SIZE, DURATION

A retrospective cohort study analyzing 3911 women undergoing ART after receiving COVID-19 vaccines. The study period spanned from 1 December 2020 to 30 September 2022.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants were categorized based on COVID-19 vaccination status, vaccine type (inactivated vs recombinant), and the timing of vaccination relative to embryo transfer. The primary outcome was the development of PIH. Multivariate robust Poisson regression was used to assess the association between vaccination and PIH, while subgroup analyses explored the risk across variables like age, BMI, and embryo transfer type.

MAIN RESULTS AND THE ROLE OF CHANCE

Women vaccinated with an inactivated COVID-19 vaccine prior to embryo transfer had a significantly higher incidence of PIH compared to unvaccinated counterparts (relative risk [RR] = 1.45; 95% CI 1.10-1.92; P = 0.009). In contrast, recombinant vaccines did not show a significant association with increased PIH risk (RR = 1.19; 95% CI 0.69-2.05; P = 0.537). The risk was particularly pronounced among women receiving two or more doses of the inactivated vaccines and those who had embryo transfers within 1 month of vaccination. Subgroup analyses showed elevated PIH risk in women aged ≥30 years old, those with BMI ≥22 kg/m2, individuals with secondary infertility, and those undergoing cleavage-stage or fresh embryo transfers.

LIMITATIONS, REASONS FOR CAUTION

The study's retrospective design limits causal inference. The sample is from a single ethnic background, and familial hypertension history was not available, potentially introducing residual confounding.

WIDER IMPLICATIONS OF THE FINDINGS

The study suggests that the type and timing of COVID-19 vaccination may influence PIH risk in ART pregnancies. These findings underscore the need for careful consideration of vaccination type and timing in ART protocols and highlight the importance of further prospective studies to validate these results before influencing clinical decision-making.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Hunan High-Level Talent Aggregation Project [2022RC4007]; the National Natural Science Foundation of China [72004148]; the Hunan Provincial Enterprise Joint Fund [2024JJ9093]; the Hunan Provincial Grant for Innovative Province Construction [2019SK4012]; the Deutschlandstipendium of the Charite; the non-restricted research grant of Boehringer Ingelheim Ltd.; and the Research Grant of CITIC-Xiangya [YNXM-202304, 202217]. The authors report no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Relapse Risk in Patients with Membranous Nephropathy after Inactivated COVID-19 Vaccination

BACKGROUND

Although there have been reports of relapse or worsening of membranous nephropathy after receiving vaccines against coronavirus disease 2019 (COVID-19), the causal relationship or association between them has not been established. This study aimed to investigate the occurrence of relapse or worsening of membranous nephropathy following inactivated COVID-19 vaccination.

METHODS

Patients who had been diagnosed with membranous nephropathy before receiving their first dose of vaccination, or before March 1, 2021, for unvaccinated patients, were included in the study. All patients were monitored at the Membranous Nephropathy Clinic of Huashan Hospital, Fudan University. The reasons for not receiving vaccines were investigated. The impact of COVID-19 vaccination on membranous nephropathy was assessed by comparing the relapse or worsening of membranous nephropathy within 12 months in vaccinated and unvaccinated patients with proteinuria <3.5 g/d. The baseline variables were balanced using cardinality matching.

RESULTS

A total of 353 patients with membranous nephropathy were included in the study, with 186 (53%) having received inactivated COVID-19 vaccines. Among the 167 unvaccinated participants, 114 (68%) expressed concerns about the possibility of disease relapse, and 47 (28%) were worried about the vaccine's efficacy due to their immunosuppressive therapy. Of the 239 participants with proteinuria <3.5 g/d, 152 were vaccinated, and 16 (11%) experienced a relapse or worsening of the disease during the follow-up period, which was similar to the 14 (16%) observed in the unvaccinated group. Following cardinality matching, there was no difference in the rate of relapse or worsening between the two groups, with 10 (13%) in the vaccinated group and 11 (15%) in the unvaccinated group (hazard ratio 0.98, 95% confidence interval 0.42-2.33).

CONCLUSION

Getting the inactivated COVID-19 vaccine may not increase risk of relapse or worsening in patients with membranous nephropathy.

Systemic and Mucosal Antibody Responses to SARS-CoV-2 Variant-Specific Prime-and-Boost and Prime-and-Spike Vaccination: A Comparison of Intramuscular and Intranasal Bivalent Vaccine Administration in a Murine Model

Background: The rapid genetic evolution of SARS-CoV-2 has led to the emergence of immune-evading, highly transmissible variants of concern (VOCs). This prompts the need for next-generation vaccines that elicit robust mucosal immunity in the airways to directly curb viral infection. Objective: Here, we investigate the impact of heterologous variant prime-boost regimens on humoral responses, focusing on intramuscular (IM) and intranasal (IN) routes of administration. Using a murine model, we assessed the immunogenicity of unadjuvanted protein boosts with Wu-1, Omicron BA.4/5, or Wu-1 + BA.4/5 spike antigens following monovalent or bivalent IM priming with mRNA-LNP vaccines. Results: IM priming induced strong systemic total and neutralizing antibody responses that were further enhanced by IN boosts with BA.4/5. IN boosting achieved the broadest serum neutralization across all VOCs tested. Notably, bivalent mRNA-LNP IM priming induced robust, cross-variant serum neutralizing antibody production, independent of subsequent IN boost combinations. Conclusions: Our findings highlight the benefit of including distinct antigenic variants in the prime vaccination followed by a variant-tailored IN boost to elicit both systemic and mucosal variant-specific responses that are potentially capable of reducing SARS-CoV-2 transmission.

A-910823, a squalene-based emulsion adjuvant, enhances robust and broad immune responses of quadrivalent influenza vaccine in ferrets

Robust and broad protective immunity is typically elicited by co-administration of an adjuvant with vaccine antigens. A-910823, a squalene-based emulsion adjuvant, has been approved in Japan. It effectively enhances the humoral and cellular immunity of S-268019-b, a recombinant COVID-19 vaccine; however, the adjuvant effects of A-910823 on other vaccines, including influenza vaccine, have not been evaluated. Here, a ferret model was employed to investigate the adjuvant effects of A-910823 when combined with split-inactivated quadrivalent influenza vaccine (QIV). We demonstrate that combination of A-910823 with QIV enhances the neutralizing antibody titer and its breadth against non-vaccine strains. Also, the protective efficacy of A-910823-adjuvanted QIV against virus challenge has been confirmed. Of note, QIV combined with A-910823 caused only minor detectable side effects, whereas a significant increase in fever was observed after two doses of mRNA-LNP in ferrets. This study provides information on the effectiveness and safety of A-910823-adjuvanted QIV and suggests the usefulness of the ferret model for evaluating vaccine-induced reactogenicity.

Current innovations in mRNA vaccines for targeting multidrug-resistant ESKAPE pathogens

The prevalence of multidrug-resistant (MDR) ESKAPE pathogens, including Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa, represents a critical global public health challenge. In response, mRNA vaccines offer an adaptable and scalable platform for immunotherapy against ESKAPE pathogens by encoding specific antigens that stimulate B-cell-driven antibody production and CD8+ T-cell-mediated cytotoxicity, effectively neutralizing these pathogens and combating resistance. This review examines recent advancements and ongoing challenges in the development of mRNA vaccines targeting MDR ESKAPE pathogens. We explore antigen selection, the nuances of mRNA vaccine technology, and the complex interactions between bacterial infections and antibiotic resistance. By assessing the potential efficacy of mRNA vaccines and addressing key barriers to their paraclinical implementation, this review highlights the promising function of mRNA-based immunization in combating MDR ESKAPE pathogens.

A SARS-CoV-2 vaccine on an NIR-II/SWIR emitting nanoparticle platform

The COVID-19 pandemic caused a global health crisis that resulted in millions of deaths. Effective vaccines have played central roles in curtailing the pandemic. Here, we developed a down-converting near-infrared IIb (NIR-IIb; 1500 to 1700 nanometers) luminescent, pure NaErF4@NaYF4 rare-earth nanoparticle (pEr) as vaccine carriers. The pEr nanoparticles were coated with three layers of cross-linked biocompatible polymers (pEr-P3; ~55 nanometers) and conjugated to the receptor binding domain (RBD) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein. Upon subcutaneous injection of the pEr-P3-RBD nanovaccine in mice, in vivo NIR-IIb imaging revealed active vaccine trafficking and migration to lymph nodes through lymphatic vessels. Two doses of the adjuvant-free vaccine elicited long-lasting (>7 months) high titers of serum viral neutralization antibody and anti-RBD immunoglobulin G, along with robust RBD-specific germinal center B cells and T follicular helper cells. We devised in vivo NIR-II molecular imaging of RBD-specific cells in lymph nodes, opening noninvasive assessments of vaccine-elicited immune responses longitudinally.

A nucleoside-modified rabies mRNA vaccine induces long-lasting and comprehensive immune responses in mice and non-human primates

Rabies is a lethal zoonotic infectious disease. Vaccines against the rabies virus have significantly reduced the number of deaths from the disease. However, all licensed rabies vaccines are inactivated vaccines, which have limited immunogenicity and complicated immunization procedures. A novel vaccine that provides sustained and comprehensive protection is urgently needed. Here, we developed a novel rabies mRNA vaccine candidate containing sequence-optimized mRNAs encoding full-length glycoprotein encapsulated in ionizable lipid nanoparticles. In mice and rhesus macaques, the rabies mRNA exhibited superior immunogenicity over licensed vaccines, especially in inducing long-lasting neutralizing antibodies and memory B cells. A single administration of 1.5 μg mRNA vaccine could provide complete protection against a lethal rabies virus challenge in mice. Additionally, the mRNA vaccine could robustly activate cellular immune responses with moderate release of several cytokines. In summary, our data demonstrated that the rabies mRNA vaccine outperformed approved inactivated vaccines in both mice and rhesus macaques. This highlights the potential of the mRNA platform in developing next-generation rabies vaccines.

Boosting with Omicron-specific mRNA vaccine or historical SARS-CoV-2 vaccines elicits discriminating immune responses against Omicron variants

Booster vaccinations are highly recommended in combating the SARS-CoV-2 Omicron variant and its subvariants. However, the optimal booster vaccination strategies and related immune mechanisms with different prior vaccinations are under-revealed. In this study, we systematically evaluated the immune responses in mice and hamsters with different prime-boost regimens before their protective efficacies against Omicron were detected. We found that boosting with Ad5-nCoV, SWT-2P or SOmicron-6P induced significantly higher levels of neutralization activities against Omicron variants than CoronaVac and ZF2001 by eliciting stronger germinal center (GC) responses. Specifically, SOmicron-6P induced even stronger antibody responses against Omicron variants in CoronaVac and Ad5-nCoV-primed animals than non-Omicron-specific vaccines but with limited differences as compared to Ad5-nCoV and SWT-2P. In addition, boosting with a specific vaccine has the potential to remodel the existing immune profiles. These findings indicated that adenovirus-vectored vaccines and mRNA vaccines would be more effective than other types of vaccines as booster shots in combating Omicron infections. Moreover, the protective efficacies of the vaccines in booster vaccinations are highly related to GC reactions in secondary lymphatic organs. In summary, these findings provide timely important information on prime-boost regimens and future vaccine design.

An oral vaccine based on the Ad5 vector with a double-stranded RNA adjuvant protects mice against respiratory syncytial virus

A safe and effective vaccine is urgently needed to prevent acute respiratory infections caused by respiratory syncytial virus (RSV). Oral administration offers several advantages, including ease of delivery, minimal stress for vaccine recipients, and greater safety than the systemic injection. In this study, we developed an oral vaccine candidate based on the human adenovirus serotype 5 (Ad5) vector, Ad5-PreF-DS2, encoding a prefusion protein of RSV with a dsRNA as an endogenous adjuvant. We evaluated the immunogenicity and protective efficacy of oral immunization against an RSV challenge in mice, comparing it with those of IM and IN immunizations. Subsequently, we performed an in-depth analysis of the B cell immune response to the oral vaccine. Our findings indicate that oral vaccines elicited a robust antibody response, T-cell response, and B-cell response, and provide effective protection against RSV infection in mice. Importantly, dsRNA adjuvants significantly enhanced T-cell immune responses and increased neutralizing antibody levels when administered via oral vaccination (P < 0.05). These preclinical data demonstrate the capacity of an oral vaccine to induce protective immunity against RSV and support further development of RSV vaccine.

M cells targeted H. pylori antigen SAM-FAdE displayed on bacterium-like particles induce protective immunity

BACKGROUND

Helicobacter pylori (H. pylori), a specific bacterium capable of surviving in the acidic environment of the stomach, has been recognized as a group of causative agents of gastric cancer. Therefore, the development of mucosal vaccines against H. pylori is expected to provide an important direction for the treatment of chronic gastritis and the prevention of gastric cancer.

METHODS AND RESULTS

In this study, we used bacteria-like particles (BLPs) obtained by treating Lactic acid bacteria (L. lactis) with hot acid, and successfully displayed the M cell-targeted H. pylori multi-epitope purified antigen SAM-FAdE, with 90% display efficiency. In addition, BLPs-SAM-FAdE can effectively target M ​​cell models and M cells of mouse Peyer's patches (PPs) through oral immunization, promote the transport of particulate vaccines to dendritic cells (BMDCs) and stimulate their maturation, significantly increased proportion of plasma cells and germinal centers B cells. This indicates that the vaccination can induce notable antigen-specific mucosal immune responses (production of sIgA), CD4+ T cell responses (Th1/Th2/Th17) and humoral immune responses (production of serum IgG). Furthermore, oral BLPs-SAM-FAdE dramatically reduced the H. pylori adhesion and specific 16S rRNA expression of H. pylori in gastric mucosal tissue, protecting gastric tissue from damage.

CONCLUSION

BLPs-SAM-FAdE can significantly reduce the adhesion of H. pylori in gastric mucosal tissue and inhibit gastritis and gastric damage caused by H. pylori infection.

Impact of Metabolic States on SARS-CoV-2 Vaccine Responses in Mouse Models of Obesity and Diabetes

The emergence of SARS-CoV-2 has resulted in a significant impact on public health, particularly for individuals with underlying health conditions such as obesity and diabetes. While vaccination efforts have played a crucial role in reducing hospitalizations, it remains unclear whether the effectiveness of these vaccines varies among different population groups. In this study, we investigated the immune responses generated by various SARS-CoV-2 vaccine platforms in mouse models with obesity and diabetes, focusing on both cell-mediated and humoral immune responses. Our findings revealed diminished immune responses in diabetic and obese mice compared to healthy counterparts. After vaccination with adjuvanted subunit or mRNA lipid nanoparticle (LNP) vaccines, both humoral and cell-mediated responses were significantly reduced in diabetic mice. Obese mice also exhibited decreased immunogenicity, albeit to a lesser extent. However, it should be noted that mRNA vaccines demonstrated strong neutralizing responses across all metabolic states, while adjuvanted subunit vaccines elicited higher antibody avidity in mice with type 2 diabetes (T2D) and obesity compared to healthy mice. These results suggest that the impaired humoral and cell-mediated responses observed in altered metabolic states may be linked to chronic inflammation associated with obesity and suboptimal glycemic control in diabetes. Understanding the impact of these metabolic disturbances on vaccine immunogenicity is crucial for developing optimized vaccines that can effectively enhance immune responses and provide long-lasting protection against SARS-CoV-2, even in individuals with obesity and diabetes. By contributing these findings, we support efforts to improve vaccine efficacy in populations affected by metabolic disorders, advancing effective immunization against SARS-CoV-2.

Immune imprinting: The persisting influence of the first antigenic encounter with rapidly evolving viruses

Immune imprinting is a phenomenon that stems from the fundamentals of immunological memory. Upon recurrent exposures to an evolving pathogen, the immune system must weigh the benefits of rapidly recalling established antibody repertoires with greater affinity to the initial variant or invest additional time and energy in producing de novo responses specific to the emerging variant. In this review, we delve into the mechanistic complexities of immune imprinting and its role in shaping subsequent immune responses, both de novo and recall, against rapidly evolving respiratory viruses such as influenza and coronaviruses. By exploring the duality of immune imprinting, we examine its potential to both enhance or hinder immune protection against disease, while emphasizing the role of host and viral factors. Finally, we explore how different vaccine platforms may affect immune imprinting and comment on vaccine strategies that can favor de novo variant-specific antibody responses.

COVID-19 vaccines: Immune correlates and clinical outcomes

Severe disease due to COVID-19 has declined dramatically as a result of widespread vaccination and natural immunity in the population. With the emergence of SARS-CoV-2 variants that largely escape vaccine-elicited neutralizing antibody responses, the efficacy of the original vaccines has waned and has required vaccine updating and boosting. Nevertheless, hospitalizations and deaths due to COVID-19 have remained low. In this review, we summarize current knowledge of immune responses that contribute to population immunity and the mechanisms how vaccines attenuate COVID-19 disease severity.

Regulating Immune Responses Induced by PEGylated Messenger RNA-Lipid Nanoparticle Vaccine

Messenger RNA (mRNA)-based therapeutics have shown remarkable progress in the treatment and prevention of diseases. Lipid nanoparticles (LNPs) have shown great successes in delivering mRNAs. After an mRNA-LNP vaccine enters a cell via an endosome, mRNA is translated into an antigen, which can activate adaptive immunity. mRNAs can bind to various pattern recognition receptors (PRRs), including toll-like receptors (TLRs), and increase the production of inflammatory cytokines. This review summarizes mechanisms of innate immunity induced by mRNAs. Polyethylene glycol (PEG) has been employed as a component of the mRNA-LNP vaccine. PEGylated nanoparticles display enhanced stability by preventing aggregation of particles. However, PEGylation can cause adverse reactions, including blood clearance (ABC) of nanoparticles via complement activation and anaphylaxis. Mechanisms of PEG-induced ABC phenomenon and anaphylaxis are presented and discussed. There have been studies aimed at reducing immune responses associated with PEG to make safe and effective vaccines. Effects of modifying or replacing PEG in reducing immune responses associated with PEGylated nanoparticles are also discussed. Modifying mRNA can induce immune tolerance, which can prevent hypersensitivity reactions induced by PEGylated mRNA-LNP vaccines. Current progress of immune tolerance induction in association with mRNA-LNP is also summarized. This review might be helpful for developing safe and effective PEGylated mRNA-LNP vaccines.

The physiological landscape and specificity of antibody repertoires are consolidated by multiple immunizations

Diverse antibody repertoires spanning multiple lymphoid organs (i.e., bone marrow, spleen, lymph nodes) form the foundation of protective humoral immunity. Changes in their composition across lymphoid organs are a consequence of B-cell selection and migration events leading to a highly dynamic and unique physiological landscape of antibody repertoires upon antigenic challenge (e.g., vaccination). However, to what extent B cells encoding identical or similar antibody sequences (clones) are distributed across multiple lymphoid organs and how this is shaped by the strength of a humoral response remains largely unexplored. Here, we performed an in-depth systems analysis of antibody repertoires across multiple distinct lymphoid organs of immunized mice and discovered that organ-specific antibody repertoire features (i.e., germline V-gene usage and clonal expansion profiles) equilibrated upon a strong humoral response (multiple immunizations and high serum titers). This resulted in a surprisingly high degree of repertoire consolidation, characterized by highly connected and overlapping B-cell clones across multiple lymphoid organs. Finally, we revealed distinct physiological axes indicating clonal migrations and showed that antibody repertoire consolidation directly correlated with antigen specificity. Our study uncovered how a strong humoral response resulted in a more uniform but redundant physiological landscape of antibody repertoires, indicating that increases in antibody serum titers were a result of synergistic contributions from antigen-specific B-cell clones distributed across multiple lymphoid organs. Our findings provide valuable insights for the assessment and design of vaccine strategies.

Lipid nanoparticles as adjuvant of norovirus VLP vaccine augment cellular and humoral immune responses in a TLR9- and type I IFN-dependent pathway

Norovirus (NoV) virus-like particles (VLPs) adjuvanted with aluminum hydroxide (Alum) are common vaccine candidates in clinical studies. Alum adjuvants usually inefficiently assist recombinant proteins to induce cellular immune responses. Thus, novel adjuvants are required to develop NoV vaccines that could induce both efficient humoral and robust cellular immune responses. Lipid nanoparticles (LNPs) are well-known mRNA delivery vehicles. Increasing evidence suggests that LNPs may have intrinsic adjuvant activity and can be used as adjuvants for recombinant protein vaccines; however, the underlying mechanism remains poorly understood. In this study, we compared the adjuvant effect of LNPs and Alum for a bivalent GI.1/GII.4 NoV VLP vaccine. Compared with Alum, LNP-adjuvanted vaccines induced earlier production of binding, blocking, and neutralizing antibodies and promoted a more balanced IgG2a/IgG1 ratio. It is crucial that LNP-adjuvanted vaccines induced stronger Th1-type cytokine-producing CD4+ T cell and CD8+ T cell responses than Alum. The adjuvant activity of LNPs depended on the ionizable lipid components. Mechanistically, LNPs activated innate immune responses in a type I IFN-dependent manner and were partially dependent on Toll-like receptor (TLR) 9, thus affecting the adaptive immune responses of the vaccine. This conclusion was supported by RNA-seq analysis and in vitro cell experiments and by the deeply blunted T cell responses in IFNαR1-/- mice immunized with LNP-adjuvanted vaccines. This study not only identified LNPs as a high quality adjuvant for NoV VLP vaccines, but also clarified the underlying mechanism of LNPs as a potent immunostimulatory component for improving protein subunit vaccines.IMPORTANCEWith the rapid development of mRNA vaccines, recurrent studies show that lipid nanoparticles (LNPs) have adjuvant activity. However, the mechanism of its adjuvant effect in protein vaccines remains unknown. In this study, we found that the LNP-adjuvanted norovirus bivalent virus-like particle vaccines led to durable antibody responses as well as Th1-type cytokine-producing CD4+ T cell and CD8+ T cell responses, which exceeded the efficiency of the conventional adjuvant aluminum hydroxide. Mechanistically, LNPs activated innate immune responses in a type I IFN-dependent manner and were partially dependent on Toll-like receptor 9, thus affecting the adaptive immune responses of the vaccine. This work unveils that LNPs as a potent immunostimulatory component may be ideal for generating CD8+ T cell and B cell responses for recombinant protein vaccines.

Optimizing immunogenicity and product presentation of a SARS-CoV-2 subunit vaccine composition: effects of delivery route, heterologous regimens with self-amplifying RNA vaccines, and lyophilization

Introduction

Dozens of vaccines have been approved or authorized internationally in response to the ongoing SARS-CoV-2 pandemic, covering a range of modalities and routes of delivery. For example, mucosal delivery of vaccines via the intranasal (i.n.) route has been shown to improve protective mucosal responses in comparison to intramuscular (i.m.) delivery. As we gain knowledge of the limitations of existing vaccines, it is of interest to understand if changes in product presentation or combinations of multiple vaccine modalities can further improve immunological outcomes.

Methods

We investigated a commercial-stage SARS-CoV-2 receptor binding domain (RBD) antigen adjuvanted with a clinical-stage TLR-7/8 agonist (3M-052) formulated on aluminum oxyhydroxide (Alum). In a murine immunogenicity model, we compared i.n. and i.m. dosing of the RBD-3M-052-Alum vaccine. We measured the magnitude of antibody responses in serum and lungs, the antibody-secreting cell populations in bone marrow, and antigen-specific cytokine-secreting splenocyte populations. Similarly, we compared different heterologous and homologous prime-boost regimens using the RBD-3M-052-Alum vaccine and a clinical-stage self-amplifying RNA (saRNA) vaccine formulated on a nanostructured lipid carrier (NLC) using the i.m. route alone. Finally, we developed a lyophilized presentation of the RBD-3M-052-Alum vaccine and compared it to the liquid presentation and a heterologous regimen including a previously characterized lyophilized form of the saRNA-NLC vaccine.

Results and discussion

We demonstrate that i.n. dosing of the RBD-3M-052-Alum vaccine increased IgA titers in the lung by more than 1.5 logs, but induced serum IgG titers 0.8 logs lower, in comparison to i.m. dosing of the same vaccine. We also show that the homologous prime-boost RBD-3M-052-Alum regimen led to the highest serum IgG and bronchial IgA titers, whereas the homologous saRNA-NLC regimen led to the highest splenocyte interferon-γ response. We found that priming with the saRNA-NLC vaccine and boosting with the RBD-3M-052-Alum vaccine led to the most desirable immune outcome of all regimens tested. Finally, we show that the lyophilized RBD-3M-052-Alum vaccine retained its immunological characteristics. Our results demonstrate that the route of delivery and the use of heterologous regimens each separately impacts the resulting immune profile, and confirm that multi-product vaccine regimens can be developed with stabilized presentations in mind.

Expression, purification and immunogenicity analyses of receptor binding domain protein of severe acute respiratory syndrome coronavirus 2 from delta variant

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the COVID-19 pandemic. The receptor binding domain (RBD), located at the spike protein of SARS-CoV-2, contains most of the neutralizing epitopes during viral infection and is an ideal antigen for vaccine development. In this study, bioinformatic analysis of the amino acid sequence data of SARS-CoV-2 RBD protein for the better understanding of molecular characteristics was performed. The SARS-CoV-2 RBD gene was inserted into pET-28a vector, and efficiently expressed in E. coli system. Then, the recombinant proteins (RBD monomer and RBD dimer protein) were purified as antigen for animal immunization. Furthermore, the results showed that the recombinant proteins (RBD monomer and RBD dimer protein) had adequate immunogenicity to stimulate specific antibodies against the corresponding protein in immunized mice. Taken together, the results of this study revealed that RBD protein had a high immuno-genicity. This study might have implications for future development of SARS-CoV-2 detection.

Staggered immunization with mRNA vaccines encoding SARS-CoV-2 polymerase or spike antigens broadens the T cell epitope repertoire

Combining a T cell-targeting mRNA vaccine encoding the conserved SARS-CoV-2 RNA-dependent RNA polymerase, RdRp, with a Spike-encoding mRNA vaccine may offer an additional pathway toward COVID-19 protection. Here, we show that a nucleoside-modified RdRp mRNA vaccine raises robust and durable CD8+ T cell responses in mice. Immunization drives a CD8+ T cell response enriched toward a specific RdRp epitope. Unexpectedly, coadministration of mRNA vaccines encoding RdRp or the Spike Receptor Binding Domain (RBD) dampens RBD-specific immune responses. Contralateral administration reduces the suppression of RBD-specific T cell responses while type I interferon signaling blockade restores RBD-specific antibodies. A staggered immunization strategy maintains both RBD vaccine-mediated antibody and T cell responses as well as protection against lethal SARS-CoV-2 challenge in human ACE2 transgenic mice. In HLA-A2.1 transgenic mice, the RdRp vaccine elicits CD8+ T cell responses against HLA-A*02:01-restricted epitopes recognized by human donor T cells. These results highlight RdRp as a candidate antigen for COVID-19 vaccines. The findings also offer insights into crafting effective multivalent mRNA vaccines to broaden CD8+ T cell responses against SARS-CoV-2 and potentially other viruses with pandemic potential.

Fc-empowered exosomes with superior epithelial layer transmission and lung distribution ability for pulmonary vaccination

Mucosal vaccines offer potential benefits over parenteral vaccines for they can trigger both systemic immune protection and immune responses at the predominant sites of pathogen infection. However, the defense function of mucosal barrier remains a challenge for vaccines to overcome. Here, we show that surface modification of exosomes with the fragment crystallizable (Fc) part from IgG can deliver the receptor-binding domain (RBD) of SARS-CoV-2 to cross mucosal epithelial layer and permeate into peripheral lung through neonatal Fc receptor (FcRn) mediated transcytosis. The exosomes F-L-R-Exo are generated by genetically engineered dendritic cells, in which a fusion protein Fc-Lamp2b-RBD is expressed and anchored on the membrane. After intratracheally administration, F-L-R-Exo is able to induce a high level of RBD-specific IgG and IgA antibodies in the animals' lungs. Furthermore, potent Th1 immune-biased T cell responses were also observed in both systemic and mucosal immune responses. F-L-R-Exo can protect the mice from SARS-CoV-2 pseudovirus infection after a challenge. These findings hold great promise for the development of a novel respiratory mucosal vaccine approach.

Advances in the study of LNPs for mRNA delivery and clinical applications

Messenger ribonucleic acid (mRNA) was discovered in 1961 as an intermediary for transferring genetic information from DNA to ribosomes for protein synthesis. The COVID-19 pandemic brought worldwide attention to mRNA vaccines. The emergency use authorization of two COVID-19 mRNA vaccines, BNT162b2 and mRNA-1273, were major achievements in the history of vaccine development. Lipid nanoparticles (LNPs), one of the most superior non-viral delivery vectors available, have made many exciting advances in clinical translation as part of the COVID-19 vaccine and therefore has the potential to accelerate the clinical translation of many gene drugs. In addition, due to these small size, biocompatibility and excellent biodegradability, LNPs can efficiently deliver nucleic acids into cells, which is particularly important for current mRNA therapeutic regimens. LNPs are composed cationic or pH-dependent ionizable lipid bilayer, polyethylene glycol (PEG), phospholipids, and cholesterol, represents an advanced system for the delivery of mRNA vaccines. Furthermore, optimization of these four components constituting the LNPs have demonstrated enhanced vaccine efficacy and diminished adverse effects. The incorporation of biodegradable lipids enhance the biocompatibility of LNPs, thereby improving its potential as an efficacious therapeutic approach for a wide range of challenging and intricate diseases, encompassing infectious diseases, liver disorders, cancer, cardiovascular diseases, cerebrovascular conditions, among others. Consequently, this review aims to furnish the scientific community with the most up-to-date information regarding mRNA vaccines and LNP delivery systems.

Mechanisms and implications of IgG4 responses to SARS-CoV-2 and other repeatedly administered vaccines

Vaccine-induced immunoglobulin G (IgG) profiles can vary with respect to the predominant subclasses that characterize the response. Among IgG subclasses, IgG4 is reported to have anti-inflammatory properties, but can also exhibit reduced capacity for virus neutralization and activation of Fc-dependent effector functions. Here, we review evidence that IgG4 subclass responses can be disproportionately increased in response to some types of vaccines targeting an array of diseases, including pertussis, HIV, malaria, and COVID-19. The basis for enhanced IgG4 induction by vaccines is poorly understood but may be associated with platform- or dose regimen-specific differences in antigen exposure and/or cytokine stimulation. The clinical implications of vaccine-induced IgG4 responses remain uncertain, though collective evidence suggests that proportional increases in IgG4 might reduce vaccine antigen-specific immunity. Additional work is needed to determine underlying mechanisms and to elucidate what role IgG4 may play in modifications of vaccine-induced immunity to disease.

A nucleoside-modified mRNA vaccine forming rabies virus-like particle elicits strong cellular and humoral immune responses against rabies virus infection in mice

Rabies is a lethal zoonotic disease that threatens human health. As the only viral surface protein, the rabies virus (RABV) glycoprotein (G) induces main neutralizing antibody (Nab) responses; however, Nab titre is closely correlated with the conformation of G. Virus-like particles (VLP) formed by the co-expression of RABV G and matrix protein (M) improve retention and antigen presentation, inducing broad, durable immune responses. RABV nucleoprotein (N) can elicit humoral and cellular immune responses. Hence, we developed a series of nucleoside-modified RABV mRNA vaccines encoding wild-type G, soluble trimeric RABV G formed by an artificial trimer motif (tG-MTQ), membrane-anchored prefusion-stabilized G (preG). Furthermore, we also developed RABV VLP mRNA vaccine co-expressing preG and M to generate VLPs, and VLP/N mRNA vaccine co-expressing preG, M, and N. The RABV mRNA vaccines induced higher humoral and cellular responses than inactivated rabies vaccine, and completely protected mice against intracerebral challenge. Additionally, the IgG and Nab titres in RABV preG, VLP and VLP/N mRNA groups were significantly higher than those in G and tG-MTQ groups. A single administration of VLP or VLP/N mRNA vaccines elicited protective Nab responses, the Nab titres were significantly higher than that in inactivated rabies vaccine group at day 7. Moreover, RABV VLP and VLP/N mRNA vaccines showed superior capacities to elicit potent germinal centre, long-lived plasma cell and memory B cell responses, which linked to high titre and durable Nab responses. In summary, our data demonstrated that RABV VLP and VLP/N mRNA vaccines could be promising candidates against rabies.

Bivalent norovirus mRNA vaccine elicits cellular and humoral responses protecting human enteroids from GII.4 infection

Nucleoside-modified mRNA-LNP vaccines have revolutionized vaccine development against infectious pathogens due to their ability to elicit potent humoral and cellular immune responses. In this article, we present the results of the first norovirus vaccine candidate employing mRNA-LNP platform technology. The mRNA-LNP bivalent vaccine encoding the major capsid protein VP1 from GI.1 and GII.4 of human norovirus, generated high levels of neutralizing antibodies, robust cellular responses, and effectively protected human enteroids from infection by the most prevalent genotype (GII.4). These results serve as a proof of concept, demonstrating that a modified-nucleoside mRNA-LNP vaccine based on norovirus VP1 sequences can stimulate an immunogenic response in vivo and generates neutralizing antibodies capable of preventing viral infection in models of human gastrointestinal tract infection.

Ipsilateral or contralateral boosting of mice with mRNA vaccines confers equivalent immunity and protection against a SARS-CoV-2 Omicron strain

Boosting with mRNA vaccines encoding variant-matched spike proteins has been implemented to mitigate their reduced efficacy against emerging SARS-CoV-2 variants. Nonetheless, in humans, it remains unclear whether boosting in the ipsilateral or contralateral arm with respect to the priming doses impacts immunity and protection. Here, we boosted K18-hACE2 mice with either monovalent mRNA-1273 (Wuhan-1 spike) or bivalent mRNA-1273.214 (Wuhan-1 + BA.1 spike) vaccine in the ipsilateral or contralateral leg after a two-dose priming series with mRNA-1273. Boosting in the ipsilateral or contralateral leg elicited equivalent levels of serum IgG and neutralizing antibody responses against Wuhan-1 and BA.1. While contralateral boosting with mRNA vaccines resulted in the expansion of spike-specific B and T cells beyond the ipsilateral draining lymph node (DLN) to the contralateral DLN, administration of a third mRNA vaccine dose at either site resulted in similar levels of antigen-specific germinal center B cells, plasmablasts/plasma cells, T follicular helper cells, and CD8+ T cells in the DLNs and the spleen. Furthermore, ipsilateral and contralateral boosting with mRNA-1273 or mRNA-1273.214 vaccines conferred similar homologous or heterologous immune protection against SARS-CoV-2 BA.1 virus challenge with equivalent reductions in viral RNA and infectious virus in the nasal turbinates and lungs. Collectively, our data show limited differences in B and T cell immune responses after ipsilateral and contralateral site boosting by mRNA vaccines that do not substantively impact protection against an Omicron strain.IMPORTANCESequential boosting with mRNA vaccines has been an effective strategy to overcome waning immunity and neutralization escape by emerging SARS-CoV-2 variants. However, it remains unclear how the site of boosting relative to the primary vaccination series shapes optimal immune responses or breadth of protection against variants. In K18-hACE2 transgenic mice, we observed that intramuscular boosting with historical monovalent or variant-matched bivalent vaccines in the ipsilateral or contralateral limb elicited comparable levels of serum spike-specific antibody and antigen-specific B and T cell responses. Moreover, boosting on either side conferred equivalent protection against a SARS-CoV-2 Omicron challenge strain. Our data in mice suggest that the site of intramuscular boosting with an mRNA vaccine does not substantially impact immunity or protection against SARS-CoV-2 infection.

mRNA-based HIV-1 vaccines

SUMMARYThe success of the Severe Acute Respiratory Syndrome Coronavirus 2 mRNA vaccines to lessen/prevent severe COVID-19 opened new opportunities to develop RNA vaccines to fight other infectious agents. HIV-1 is a lentivirus that integrates into the host cell genome and persists for the lifetime of infected cells. Multiple mechanisms of immune evasion have posed significant obstacles to the development of an effective HIV-1 vaccine over the last four decades since the identification of HIV-1. Recently, attempts to address some of these challenges have led to multiple studies that manufactured, optimized, and tested, in different animal models, mRNA-based HIV-1 vaccines. Several clinical trials have also been initiated or are planned to start soon. Here, we review the current strategies applied to HIV-1 mRNA vaccines, discuss different targeting approaches, summarize the latest findings, and offer insights into the challenges and future of HIV-1 mRNA vaccines.

Waning Humoral Immune Response Following the Third and Fourth SARS-COV-2 Vaccine: A Cohort Study in Healthcare Workers

BACKGROUND

This study is aimed at providing information about the timing of booster doses and antibody kinetics in healthcare workers.

METHODS

This research extends a prospective cohort study conducted at Dokuz Eylul University Hospital in Turkey, covering the period from March 2021 to December 2021. During this timeframe, the antibody levels of the health workers were measured at four different time points. The associations of antibody levels with gender, age, occupation, body mass index (BMI), chronic disease, and smoking were analyzed.

RESULTS

There was a significant difference between antibody levels in all four blood draws (p < 0.001). Antibody levels decreased in both those vaccinated with BNT162b2 (p < 0.001) and those vaccinated with CoronaVac (p = 0.002) until the fourth blood draw. There was a significant difference between those vaccinated with one and two doses of booster BNT162b2 before the third blood draw (p < 0.001), which continued at the fourth blood draw (p < 0.001). The antibody levels of those with an interval of 41-50 days between two vaccinations decreased significantly at the fourth blood draw (p < 0.001).

CONCLUSIONS

This study provides insight into the dynamics and persistence of antibody response after additional COVID-19 vaccine doses among healthcare workers. The longer the interval between booster doses may result in greater antibody levels being maintained over time, allowing for longer durations of protection.

Individuals carrying the HLA-B*15 allele exhibit favorable responses to COVID-19 vaccines but are more susceptible to Omicron BA.5.2 and XBB.1.16 infection

Background

Natural infection or vaccination have provided robust immune defense against SARS-CoV-2 invasion, nevertheless, Omicron variants still successfully cause breakthrough infection, and the underlying mechanisms are poorly understood.

Methods

Sequential blood samples were continuously collected at different time points from 252 volunteers who were received the CanSino Ad5-nCoV (n= 183) vaccine or the Sinovac CoronaVac inactivated vaccine (n= 69). The anti-SARS-CoV-2 prototype and Omicron BA.5.2 as well as XBB.1.16 variant neutralizing antibodies (Nab) in sera were detected by ELISA. Sera were also used to measure pseudo and live virus neutralization assay. The associations between the anti-prototype Nab levels and different HLA-ABC alleles were analyzed using artificial intelligence (AI)-deep learning techniques. The frequency of B cells in PBMCs was investigated by flow cytometry assay (FACs).

Results

Individuals carrying the HLA-B*15 allele manifested the highest concentrations of anti-SARS-CoV-2 prototype Nab after vax administration. Unfortunately, these volunteers are more susceptible to Omicron BA.5.2 breakthrough infection due to their sera have poorer anti-BA.5.2 Nab and lower levels of viral neutralization efficacy. FACs confirmed that a significant decrease in CD19+CD27+RBD+ memory B cells in these HLA-B*15 population compared to other cohorts. Importantly, generating lower concentrations of cross-reactive anti-XBB.1.16 Nab post-BA.5.2 infection caused HLA-B*15 individuals to be further infected by XBB.1.16 variant.

Conclusions

Individuals carrying the HLA-B*15 allele respond better to COVID-19 vax including the CanSino Ad5-nCoV and the Sinovac CoronaVac inactivated vaccines, but are more susceptible to Omicron variant infection, thus, a novel vaccine against this population is necessary for COVID-19 pandemic control in the future.

Innate immune signatures in the nasopharynx after SARS-CoV-2 infection and links with the clinical outcome of COVID-19 in Omicron-dominant period

While severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is characterized by impaired induction of interferons (IFNs) and IFN-stimulated genes (ISGs), the IFNs and ISGs in upper airway is essential to restrict the spread of respiratory virus. Here, we identified the prominent IFN and ISG upregulation in the nasopharynx (NP) of mild and even severe coronavirus disease 2019 (COVID-19) patients (CoV2+) in Omicron era and to compare their clinical outcome depending on the level of IFNs and ISGs. Whereas the induction of IFNB was minimal, transcription of IFNA, IFNG, and IFNLs was significantly increased in the NP of CoV2 + patients. IFNs and ISGs may be more upregulated in the NP of CoV2 + patients at early phases of infection according to viral RNA levels and this is observed even in severe cases. IFN-related innate immune response might be characteristic in macrophages and monocytes at the NP and the CoV2 + patients with higher transcription of IFNs and ISGs in the NP showed a correlation with good prognosis of COVID-19. This study presents that IFNs and ISGs may be upregulated in the NP, even in severe CoV2 + patients depending on viral replication during Omicron-dominant period and the unique IFN-responsiveness in the NP links with COVID-19 clinical outcomes.

Human Cytomegalovirus mRNA-1647 Vaccine Candidate Elicits Potent and Broad Neutralization and Higher Antibody-Dependent Cellular Cytotoxicity Responses Than the gB/MF59 Vaccine

BACKGROUND

MF59-adjuvanted gB subunit (gB/MF59) vaccine demonstrated approximately 50% efficacy against human cytomegalovirus (HCMV) acquisition in multiple clinical trials, suggesting that efforts to improve this vaccine design might yield a vaccine suitable for licensure.

METHODS

A messenger RNA (mRNA)-based vaccine candidate encoding HCMV gB and pentameric complex (PC), mRNA-1647, is currently in late-stage efficacy trials. However, its immunogenicity has not been compared to the partially effective gB/MF59 vaccine. We assessed neutralizing and Fc-mediated immunoglobulin G (IgG) effector antibody responses induced by mRNA-1647 in both HCMV-seropositive and -seronegative vaccinees from a first-in-human clinical trial through 1 year following third vaccination using a systems serology approach. Furthermore, we compared peak anti-gB antibody responses in seronegative mRNA-1647 vaccinees to that of seronegative gB/MF59 vaccine recipients.

RESULTS

mRNA-1647 vaccination elicited and boosted HCMV-specific IgG responses in seronegative and seropositive vaccinees, respectively, including neutralizing and Fc-mediated effector antibody responses. gB-specific IgG responses were lower than PC-specific IgG responses. gB-specific IgG and antibody-dependent cellular phagocytosis responses were lower than those elicited by gB/MF59. However, mRNA-1647 elicited higher neutralization and antibody-dependent cellular cytotoxicity (ADCC) responses.

CONCLUSIONS

Overall, mRNA-1647 vaccination induced polyfunctional and durable HCMV-specific antibody responses, with lower gB-specific IgG responses but higher neutralization and ADCC responses compared to the gB/MF59 vaccine.

CLINICAL TRIALS REGISTRATION

NCT03382405 (mRNA-1647) and NCT00133497 (gB/MF59).

Recent Advancements in mRNA Vaccines: From Target Selection to Delivery Systems

mRNA vaccines are leading a medical revolution. mRNA technologies utilize the host's own cells as bio-factories to produce proteins that serve as antigens. This revolutionary approach circumvents the complicated processes involved in traditional vaccine production and empowers vaccines with the ability to respond to emerging or mutated infectious diseases rapidly. Additionally, the robust cellular immune response elicited by mRNA vaccines has shown significant promise in cancer treatment. However, the inherent instability of mRNA and the complexity of tumor immunity have limited its broader application. Although the emergence of pseudouridine and ionizable cationic lipid nanoparticles (LNPs) made the clinical application of mRNA possible, there remains substantial potential for further improvement of the immunogenicity of delivered antigens and preventive or therapeutic effects of mRNA technology. Here, we review the latest advancements in mRNA vaccines, including but not limited to target selection and delivery systems. This review offers a multifaceted perspective on this rapidly evolving field.

Immune responses in COVID-19 patients: Insights into cytokine storms and adaptive immunity kinetics

SARS-CoV-2 infection can trigger cytokine storm in some patients, which characterized by an excessive production of cytokines and chemical mediators. This hyperactive immune response may cause significant tissue damage and multiple organ failure (MOF). The severity of COVID-19 correlates with the intensity of cytokine storm, involving elements such as IFN, NF-κB, IL-6, HMGB1, etc. It is imperative to rapidly engage adaptive immunity to effectively control the disease progression. CD4+ T cells facilitate an immune response by improving B cells in the production of neutralizing antibodies and activating CD8+ T cells, which are instrumental in eradicating virus-infected cells. Meanwhile, antibodies from B cells can neutralize virus, obstructing further infection of host cells. In individuals who have recovered from the disease, virus-specific antibodies and memory T cells were observed, which could confer a level of protection, reducing the likelihood of re-infection or attenuating severity. This paper discussed the roles of macrophages, IFN, IL-6 and HMGB1 in cytokine release syndrome (CRS), the intricacies of adaptive immunity, and the persistence of immune memory, all of which are critical for the prevention and therapeutic strategies against COVID-19.

Plasma EV-miRNAs as Potential Biomarkers of COVID-19 Vaccine Immune Response in Cancer Patients

Cancer patients, prone to severe COVID-19, face immune challenges due to their disease and treatments. Identifying biomarkers, particularly extracellular vesicle (EV)-derived microRNAs (miRNAs), is vital for comprehending their response to COVID-19 vaccination. Therefore, this study aimed to investigate specific EV-miRNAs in the plasma of cancer patients under active treatment who received the COVID-19 booster vaccine. The selected miRNAs (EV-hsa-miR-7-5p, EV-hsa-miR-15b-5p, EV-hsa-miR-24-3p, EV-hsa-miR-145- 5p, and EV-hsa-miR-223-3p) are involved in regulating SARS-CoV-2 spike protein and cytokine release, making them potential biomarkers for vaccination response. The study involved 54 cancer patients. Plasma and serum samples were collected at pre-boost vaccination, and at 3 and 6 months post-boost vaccination. Anti-spike antibody levels were measured. Additionally, RNA was extracted from EVs isolated from plasma and the expression levels of miRNAs were assessed. The results showed a significantly positive antibody response after COVID-19 boost vaccination. The expression levels of EV-hsa-miR-7-5p, EV-hsa-miR-15b-5p, EV-hsa-miR-24-3p, and EV-hsa-miR-223-3p increased significantly after 6 months of COVID-19 booster vaccination. Interestingly, an increased expression of certain EV-hsa-miRNAs was positively correlated. Bioinformatic analysis revealed that these correlated miRNAs play a critical role in regulating the targets present in antiviral responses and cytokine production. These findings suggest that EV-hsa-miR-15b-5p, EV-hsa-miR-24-3p, and EV-hsa-miR-223-3p may be crucial in immune response induced by mRNA vaccines.

Equal Maintenance of Anti-SARS-CoV-2 Antibody Levels Induced by Heterologous and Homologous Regimens of the BNT162b2, ChAdOx1, CoronaVac and Ad26.COV2.S Vaccines: A Longitudinal Study Up to the 4th Dose of Booster

Several technological approaches have been used to develop vaccines against COVID-19, including those based on inactivated viruses, viral vectors, and mRNA. This study aimed to monitor the maintenance of anti-SARS-CoV-2 antibodies in individuals from Brazil according to the primary vaccination regimen, as follows: BNT162b2 (group 1; 22) and ChAdOx1 (group 2; 18). Everyone received BNT162b2 in the first booster while in the second booster CoronaVac, Ad26.COV2.S, or BNT162b2. Blood samples were collected from 2021 to 2023 to analyze specific RBD (ELISA) and neutralizing antibodies (PRNT50). We observed a progressive increase in anti-RBD and neutralizing antibodies in each subsequent dose, remaining at high titers until the end of follow-up. Group 1 had higher anti-RBD antibody titers than group 2 after beginning the primary regimen, with significant differences after the 2nd and 3rd doses. Group 2 showed a more expressive increase after the first booster with BNT162B2 (heterologous booster). Group 2 also presented high levels of neutralizing antibodies against the Gamma and Delta variants until five months after the second booster. In conclusion, the circulating levels of anti-RBD and neutralizing antibodies against the two variants of SARS-CoV-2 were durable even five months after the 4th dose, suggesting that periodic booster vaccinations (homologous or heterologous) induced long-lasting immunity.

Virus-Mimetic Extracellular-Vesicle Vaccine Boosts Systemic and Mucosal Immunity via Immune Recruitment

Mucosal vaccines can prevent viruses from infecting the respiratory mucosa, rather than only curtailing infection and protecting against the development of disease symptoms. The SARS-CoV-2 spike receptor-binding domain (RBD) is a compelling vaccine target but is undermined by suboptimal mucosal immunogenicity. Here, we report a SARS-CoV-2-mimetic extracellular-vesicle vaccine developed using genetic engineering and dendritic cell membrane budding. After mucosal immunization, the vaccine recruits antigen-presenting cells rapidly initiating a strong innate immune response. Notably, it obviates the need for adjuvants and can induce germinal center formation through both intramuscular and intratracheal vaccination. It not only elicits high levels of RBD-specific antibodies but also stimulates extensive cellular immunity in the respiratory mucosa. A sequential immunization strategy, starting with an intramuscular injection followed by an intratracheal booster, significantly bolsters mucosal immunity with high levels of IgA and tissue-resident memory T cell responses, thereby establishing a formidable defense against pseudovirus infection.

Trichinella spiralis Infection Inhibits the Efficacy of RBD Protein of SARS-CoV-2 Vaccination via Regulating Humoral and Cellular Immunity

Vaccines are the most effective and feasible way to control pathogen infection. Helminths have been reported to jeopardize the protective immunity mounted by several vaccines. However, there are no experimental data about the effect of helminth infection on the effectiveness of COVID-19 vaccines. Here, a mouse model of trichinosis, a common zoonotic disease worldwide, was used to investigate effects of Trichinella spiralis infection on the RBD protein vaccine of SARS-CoV-2 and the related immunological mechanism, as well as the impact of albendazole (ALB) deworming on the inhibitory effect of the parasite on the vaccination. The results indicated that both the enteric and muscular stages of T. spiralis infection inhibited the vaccine efficacy, evidenced by decreased levels of IgG, IgM, sIgA, and reduced serum neutralizing antibodies, along with suppressed splenic germinal center (GC) B cells in the vaccinated mice. Pre-exposure to trichinosis promoted Th2 and/or Treg immune responses in the immunized mice. Furthermore, ALB treatment could partially reverse the inhibitory effect of T. spiralis infection on the efficiency of the vaccination, accompanied by a restored proportion of splenic GC B cells. Therefore, given the widespread prevalence of helminth infections worldwide, deworming therapy needs to be considered when implementing COVID-19 vaccination strategies.

Development of a single-chain variable antibody fragment against a conserved region of the SARS-CoV-2 spike protein

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has prolonged the duration of the pandemic because of the continuous emergence of new variant strains. The emergence of these mutant strains makes it difficult to detect the virus with the existing antibodies; thus, the development of novel antibodies that can target both the variants as well as the original strain is necessary. In this study, we generated a high-affinity monoclonal antibody (5G2) against the highly conserved region of the SARS-CoV-2 spike protein to detect the protein variants. Moreover, we generated its single-chain variable antibody fragment (sc5G2). The sc5G2 expressed in mammalian and bacterial cells detected the spike protein of the original SARS-CoV-2 and variant strains. The resulting sc5G2 will be a useful tool to detect the original SARS-CoV-2 and variant strains.

Distinguishing Axillary Lymphadenopathy after COVID-19 Vaccination from Malignant Lymphadenopathy

Objectives: To study the differences between malignant hypermetabolic axillary lymphadenopathy (MHL) and COVID-19 vaccine-associated axillary hypermetabolic lymphadenopathy (VAHL) using clinical imaging. Methods: A total of 1096 patients underwent Positron Emission Tomography-Computed Tomography (PET-CT) between 1 June 2021 and 30 April 2022 at Ehime University Hospital. In total, 188 patients with axillary lymphadenopathy after the COVID-19 vaccination were evaluated. The patients were classified into three groups such as VAHL (n = 27), MHL (n = 21), and equivocal hypermetabolic axillary lymphadenopathy (EqHL; n = 140). Differences in lymph node (LN) swellings were statistically analyzed using clinical imaging (echography, CT, and 18F-FDG PET). Results: MHL included a higher female population (90.5%) owing to a higher frequency of breast cancer (80.9%). Axillary LNs of MHL did not show any LN fatty hilums (0%); however, those of VAHL and EqHL did (15.8 and 36%, respectively). After the logistic regression analysis of the patients who had axillary lymphadenopathy without any LN fatty hilums, the minor axis length and ellipticity (minor axis/major axis) in the largest axillary LN, SUVmax, and Tissue-to-Background Ratio (TBR) were useful in distinguishing malignant lymphadenopathies. A receiver-operating characteristic (ROC) analysis indicated that a cut-off value of ≥7.3 mm for the axillary LN minor axis (sensitivity: 0.714, specificity: 0.684) and of ≥0.671 for ellipticity (0.667 and 0.773, respectively) in the largest LN with the highest SUVmax and TBR were predictive of MHL. Conclusions: Axillary lymphadenopathy of the minor axis and ellipticity in LN without fatty hilums may be useful to be suspicious for malignancy, even in patients who have received COVID-19 vaccination. Further examinations, such as 18F-FDG PET, are recommended for such patients.

Distinct components of nucleoside-modified messenger RNA vaccines cooperate to instruct efficient germinal center responses

Nucleoside-modified mRNA vaccines elicit protective antibodies through their ability to promote T follicular helper (Tfh) cells. The lipid nanoparticle (LNP) component of mRNA vaccines possesses inherent adjuvant activity. However, to what extent the nucleoside-modified mRNA can be sensed and contribute to Tfh cell responses remains largely undefined. Herein, we deconvoluted the signals induced by LNP and mRNA that instruct dendritic cells (DCs) to promote Tfh cell differentiation. We demonstrated that the nucleoside-modified mRNA drives the production of type I interferons that act on DCs to induce their maturation and the induction of Th1-biased Tfh responses. Conversely, LNP favors the acquisition of a Tfh cell-inducing program in DCs, a stronger Th2 polarization in Tfh cells, and allows for rapid mRNA translation by DCs within the draining lymph node. Our work unravels distinct adjuvant features of mRNA and LNP necessary for the induction of Tfh cells, with implications for vaccine design.

Modulation of innate immune response to mRNA vaccination after SARS-CoV-2 infection or sequential vaccination in humans

mRNA vaccines are likely to become widely used for the prevention of infectious diseases in the future. Nevertheless, a notable gap exists in mechanistic data, particularly concerning the potential effects of sequential mRNA immunization or preexisting immunity on the early innate immune response triggered by vaccination. In this study, healthy adults, with or without documented prior SARS-CoV-2 infection, were vaccinated with the BNT162b2/Comirnaty mRNA vaccine. Prior infection conferred significantly stronger induction of proinflammatory and type I IFN-related gene signatures, serum cytokines, and monocyte expansion after the prime vaccination. The response to the second vaccination further increased the magnitude of the early innate response in both study groups. The third vaccination did not further increase vaccine-induced inflammation. In vitro stimulation of PBMCs with TLR ligands showed no difference in cytokine responses between groups, or before or after prime vaccination, indicating absence of a trained immunity effect. We observed that levels of preexisting antigen-specific CD4 T cells, antibody, and memory B cells correlated with elements of the early innate response to the first vaccination. Our data thereby indicate that preexisting memory formed by infection may augment the innate immune activation induced by mRNA vaccines.

Screening for lipid nanoparticles that modulate the immune activity of helper T cells towards enhanced antitumour activity

Lipid nanoparticles (LNPs) can be designed to potentiate cancer immunotherapy by promoting their uptake by antigen-presenting cells, stimulating the maturation of these cells and modulating the activity of adjuvants. Here we report an LNP-screening method for the optimization of the type of helper lipid and of lipid-component ratios to enhance the delivery of tumour-antigen-encoding mRNA to dendritic cells and their immune-activation profile towards enhanced antitumour activity. The method involves screening for LNPs that enhance the maturation of bone-marrow-derived dendritic cells and antigen presentation in vitro, followed by assessing immune activation and tumour-growth suppression in a mouse model of melanoma after subcutaneous or intramuscular delivery of the LNPs. We found that the most potent antitumour activity, especially when combined with immune checkpoint inhibitors, resulted from a coordinated attack by T cells and NK cells, triggered by LNPs that elicited strong immune activity in both type-1 and type-2 T helper cells. Our findings highlight the importance of optimizing the LNP composition of mRNA-based cancer vaccines to tailor antigen-specific immune-activation profiles.

pGM-CSF as an adjuvant in DNA vaccination against SARS-CoV-2

The emergence of SARS-CoV-2 presents a significant global public health dilemma. Vaccination has long been recognized as the most effective means of preventing the spread of infectious diseases. DNA vaccines have attracted attention due to their safety profile, cost-effectiveness, and ease of production. This study aims to assess the efficacy of plasmid-encoding GM-CSF (pGM-CSF) as an adjuvant to augment the specific humoral and cellular immune response elicited by DNA vaccines based on the receptor-binding domain (RBD) antigen. Compared to the use of plasmid-encoded RBD (pRBD) alone, mice that were immunized with a combination of pRBD and pGM-CSF exhibited significantly elevated levels of RBD-specific antibody titers in serum, BALF, and nasal wash. Furthermore, these mice generated more potent neutralization antibodies against both the wild-type and Omicron pseudovirus, as well as the ancestral virus. In addition, pGM-CSF enhanced pRBD-induced CD4+ and CD8+ T cell responses and promoted central memory T cells storage in the spleen. At the same time, tissue-resident memory T (Trm) cells in the lung also increased significantly, and higher levels of specific responses were maintained 60 days post the final immunization. pGM-CSF may play an adjuvant role by promoting antigen expression, immune cells recruitment and GC B cell responses. In conclusion, pGM-CSF may be an effective adjuvant candidate for the DNA vaccines against SARS-CoV-2.

Comparative single-cell RNA sequencing analysis of immune response to inactivated vaccine and natural SARS-CoV-2 infection

Uncovering the immune response to an inactivated SARS-CoV-2 vaccine (In-Vac) and natural infection is crucial for comprehending COVID-19 immunology. Here we conducted an integrated analysis of single-cell RNA sequencing (scRNA-seq) data from serial peripheral blood mononuclear cell (PBMC) samples derived from 12 individuals receiving In-Vac compared with those from COVID-19 patients. Our study reveals that In-Vac induces subtle immunological changes in PBMC, including cell proportions and transcriptomes, compared with profound changes for natural infection. In-Vac modestly upregulates IFN-α but downregulates NF-κB pathways, while natural infection triggers hyperactive IFN-α and NF-κB pathways. Both In-Vac and natural infection alter T/B cell receptor repertoires, but COVID-19 has more significant change in preferential VJ gene, indicating a vigorous immune response. Our study reveals distinct patterns of cellular communications, including a selective activation of IL-15RA/IL-15 receptor pathway after In-Vac boost, suggesting its potential role in enhancing In-Vac-induced immunity. Collectively, our study illuminates multifaceted immune responses to In-Vac and natural infection, providing insights for optimizing SARS-CoV-2 vaccine efficacy.