npj Vaccines

Development of an effective HCV vaccine requires the induction of both broadly neutralizing antibodies (bnAbs) and a robust cellular response. One issue that has arisen is that HCV subunit vaccines have limited immunogenicity, thus requiring multivalent formats in order to elicit a robust anti-HCV immune response. Toward that end, nanoparticle vaccines possess the ability to facilitate a controlled multivalent presentation and trafficking to lymph nodes, where they can interact with both arms of the immune system. Here, we used a soluble, secreted form of E1E2 (sE1E2) to assemble native E1E2 into a nanoparticle platform using a post-purification coupling assembly system. Nanoparticles were assembled by purifying sE1E2 containing a C-terminal SpyTag and an mi3-SpyCatcher fusion separately and covalently coupling the components via incubation. Free sE1E2-SpyTag was removed from nanoparticle preparations via gel filtration. The sE1E2-mi3 nanoparticles are fully competent to bind conformation-dependent bnAbs, indicating retention of a native assembly in the nanoparticle format. Electron microscopy analysis showed a clear incorporation of sE1E2 on the surface of the nanoparticle. Immunogenicity of sE1E2-mi3 nanoparticles was examined relative to sE1E2 alone and membrane-bound E1E2 (mbE1E2) following inoculation of groups of CD1 mice. Assessment of the immunogenicity of the sE1E2-mi3 nanoparticles showed that the nanoparticle assembly has a similar immunogenicity profile to that of mbE1E2 after only a prime and one boost, and overall superior to sE1E2. This proof-of-principle study sets the stage for further exploration of nanoparticles and other multivalent platforms for the development of E1E2-based vaccines. ImportanceHepatitis C virus infects approximately 50 million people, and at present no effective HCV vaccine exists. Due to the high sequence variability of HCV and the resulting difficulty in developing a vaccine that elicits a broadly neutralizing response, multiple efforts are underway to enhance the immunogenicity of HCV vaccine candidates. In this study, we incorporated native soluble, secreted E1E2 (sE1E2) into a 60-mer nanoparticle via the SpyTag-SpyCatcher system and covalent isopeptide bond attachment using the purified components. These nanoparticles are antigenically intact and elicit a neutralizing antibody response at an earlier time point in the immunization regimen than the corresponding subunit vaccine. These studies show that a well-characterized sE1E2 platform compatible with multiple genotypes can be coupled to nanoparticles for use as a vaccine candidate.

Current vaccines for respiratory viruses are primarily administered intramuscularly. Messenger RNA-lipid nanoparticle (LNP)-based intramuscular vaccination for respiratory coronaviruses induces strong systemic IgG antibody responses; they do not consistently elicit IgA in the upper and lower respiratory tracts. Using a synthetic consensus spike protein aimed to broadening immunity against SARS-like viruses, SarbConS, coupled to ferritin nanoparticles co-delivered with mastoparan-7 and an FDA-approved CpG adjuvant, we intranasally boost SARS-CoV-2-immune animals. This intranasal boosting strategy elicits durable mucosal IgA responses in the respiratory tract, along with robust systemic IgG responses, and demonstrates durable protection against SARS-CoV-2 and zoonotic SARS-like viruses from bats and pangolins. Intranasal delivery of mastoparan-7 and CpG with MERS-CoV spike protein similarly elicits MERS-CoV-specific mucosal IgA and protects against MERS-CoV challenge in mice. Moreover, we observe durable protection against these genetically divergent zoonotic SARS-like viral challenges compared to intramuscular mRNA-LNP or unadjuvanted intranasal spike boosters. Intranasal SarbConS-ferritin nanoparticle intranasal vaccination similarly elicited durable mucosal IgA and antigen-specific memory B cell responses in the airways. The protective efficacy of M7-CpG adjuvanted SarbConS ferritin nanoparticle intranasal boosters was abolished in IgA knockout mice, suggesting a requirement for IgA in mediating respiratory mucosal vaccine-mediated protection against coronavirus infection. Altogether, our results demonstrate that respiratory mucosal vaccination can elicit durable and cross-protective mucosal IgA responses against genetically diverse zoonotic coronaviruses with implications for improved mucosal vaccines for highly transmissible respiratory viral pathogens.

Background: Vaccination of people with HIV (PWH) on suppressive antiretroviral therapy (ART) represents a novel approach for evaluating candidate broadly neutralizing antibody (bnAb) immunogens for preventive and therapeutic HIV vaccines. Given pre-existing immunity in PWH, the safety of this approach requires careful assessment prior to broader application. Here, we report on the design and safety of the RENEW-SHCS study which evaluates the immunization of PWH with BG505 SOSIP.v4.1-GT1.1, an immunogen engineered to induce precursors of CD4 binding site (CD4bs)- and V2-apex targeting bnAbs. Methods. RENEW-SHCS is a phase I, open-label, non-randomized vaccination trial evaluating a single dose of the recombinant germline-targeting envelope trimer BG505 SOSIP.v4.1-GT1.1 (GT1.1), adjuvanted with 3M052-AF and Aluminum hydroxide (alum), in PWH on suppressive ART enrolled from the Swiss HIV Cohort Study. Participants were previously classified as bnAb or non-neutralizing antibody (nnAb) inducers, with a target enrollment of 15 per group, and were monitored for safety and immunogenicity for 24 weeks while continuing standard ART. Due to an out-of-specification stability measurement of adjuvant 3M052-AF the trial was paused after 23 immunizations and subjected to an unscheduled interim safety and reactogenicity assessment comprising protocol defined outcome measures (adverse events, clinical laboratory measurements and HIV-1 viral load). Results. Twenty-three participants (10 bnAb and 13 nnAb inducers, median age 59 years, 17 male / 6 female) were vaccinated between March and August 2025 before interruption of the trial. All participants completed follow-up with full protocol adherence. The interim-safety analysis confirmed that no vaccine-related serious adverse events occurred. Solicited local (96%) and systemic (83%) reactions were common, predominantly grade 1-2, transient, and self-limited. Transient laboratory changes occurred but mostly remained within the normal range, with no vaccine-related grade 3 abnormalities. We observed predominantly transient local and systemic reactions, which were similar or milder to the reactogenicity profile reported for immunization of adult people without HIV (PWOH) with GT1.1 adjuvanted with AS01b reported in the IAVI C101 trial. No viral rebound under ART occurred. One participant experienced two viral blips (>50 HIV-1 RNA copies/ml), one before and one 16 weeks after vaccination with subsequent re-suppression. All others maintained viral suppression (<50 copies/ml) throughout follow-up. Conclusion. RENEW-SHCS demonstrated a favorable safety and reactogenicity profile of single dose immunization with GT1.1 in PWH, comparable to that observed in PWOH. The findings of this phase I study support the feasibility of vaccinating ART-treated PWH in trials of preventive and therapeutic HIV vaccine strategies.

RTS,S/AS01, an adjuvanted subunit malaria vaccine, induces protective but short-lived anti- Plasmodium falciparum circumsporozoite protein (CSP) antibody titers. To better understand the lack of sustained protection post-vaccination, we analyzed CSP-specific B cells over time in malaria-naive individuals following immunization with RTS,S/AS01. Longitudinal analyses of the cellular responses revealed a shift in the specificity of CSP-specific B cells over time. Early post- vaccine responses were dominated by plamsablasts and class-switched memory B cells (MBCs) specific for the NANP-repeat region of CSP, epitopes associated with protective antibodies. However, the frequency of NANP-repeat-specific MBCs declines, while longer-term memory specific for the C-terminus of CSP persists. Despite being class-switched and affinity matured, C- term monoclonal antibodies derived from these MBCs failed to protect mice against a transgenic parasite challenge. Taken together, these findings suggest that RTS,S/AS01 induces a transient, protective NANP repeat-specific B cell response that is subsequently replaced by memory B cells with non-protective reactivities, potentially explaining its limited long-term efficacy and limited response to subsequent challenges or boosters.

Seeking a simple vaccine to protect against all cancer-associated human papillomaviruses (HPV), L2 residues 17-36 of both HPV16 and HPV31 displayed on the surface of an Adeno-Associated Virus-Like Particle (AAVLP-HPV) was developed. Here, a phase 1 randomized, placebo-controlled, double-blind clinical study has been conducted in 20 male and female subjects at a single dose level (20 ug) without an adjuvant. AAVLP-HPV vaccine administration was safe and well tolerated. Repeat vaccination with AAVLP-HPV elicited L2-specific neutralizing antibodies of modest titer in serum. Antibodies cross-reactive with L2 of diverse HPV types were detected, but responses were weak in most vaccinees. We conclude that while AAVLP-HPV vaccination is well tolerated, an adjuvant is likely needed to consistently elicit durable and broadly neutralizing responses.

Systems vaccinology approaches have identified factors affecting vaccine responses in multiple studies, but the ability of computational models to generalize these findings to unseen data remains unclear. We established a community resource to create and compare models predicting B. pertussis booster vaccination responses and put such modeling approaches to the test. We compiled multi-modal experimental training data from three independent cohorts (n=117 individuals), and asked investigators to predict vaccine responses in a cohort of 54 newly recruited individuals using only their pre-booster vaccination data. We benchmarked a total of 107 computational models. Top-performing models were characterized by workflows that prioritized rigorous data preprocessing, robust imputation of missing data, and the use of multi-omics integration or non-linear machine learning. We identified pre-existing antigen-specific antibody titers and baseline monocyte frequencies as the most consistent predictors of post-vaccination immunity, highlighting the dominant role of individual immune setpoints. We established the resulting datasets and evaluation framework as a community resource to advance predictive immunology and facilitate personalized vaccination strategies.

SARS-CoV-2 evolution has reduced the efficacy of clinical monoclonal antibodies, underscoring the need for therapeutics targeting conserved viral regions. The Spike (S) heptad repeat 2 (HR2) stem helix is highly conserved across SARS-CoV-2 variants and related betacoronaviruses. Although antibodies to this region can neutralize infection, their natural occurrence and evolution remain poorly understood. We previously identified human neutralizing antibodies to a conserved peptide within this region (HR2 coldspot). Here, we show that plasma IgG reactivity to this region remains rare, even after repeated antigen exposure. Longitudinal analysis over 30 months revealed continued somatic hypermutation of HR2-specific antibodies, yet none surpassed the potency or breadth of hr2.016, which emerged shortly after primary infection. Crystal structures of four HR2 stem helix antibodies revealed convergent recognition across distinct antibody lineages. Comparison of hr2.016 with its non-neutralizing clonal relative hr2.086 showed that structural convergence masks distinct binding kinetics. Surface plasmon resonance and molecular dynamics simulations revealed a more stable interaction network for hr2.016, with slower dissociation and prolonged S residence time. Neutralization required the IgG format, supporting an avidity-driven mechanism. Together, these findings define kinetic and avidity constraints governing neutralization at the HR2 stem helix and position hr2.016 as a resilient therapeutic candidate.

Plasmodium parasites develop in the liver and egress to infect red blood cells, causing malaria. Vaccines that generate hepatic CD8+ T cells eliminate liver-stage parasites and prevent disease, yet how these T cells are induced is incompletely understood. We report that in mice vaccinated with replication-competent genetically attenuated Plasmodium parasites, antagonism of {gamma}{delta} T cell function curtails protection. Vaccination expands hepatic IFN{gamma}+ {gamma}{delta} NKT cells, and depletion of these cells abrogates hepatic CD8+ T cell responses. IFN{gamma}+ {gamma}{delta} NKT cells are nearly undetectable in the blood at steady state but their frequencies in the periphery are significantly increased following vaccination, hinting at their utility as biomarkers of protection. To assess the relevance of these results in humans, we performed secondary analyses of peripheral blood samples from human clinical trial participants immunized with attenuated Plasmodium parasites (Trial registration: ClinicalTrials.gov NCT01994525). Flow cytometric and single cell transcriptomic characterization of {gamma}{delta} T cells in these samples unveil for the first time, increased frequency of activated V{delta}2- {gamma}{delta} T cells and gene expression in cytotoxic, tissue-homing V{delta}1+ {gamma}{delta} T cells as correlates of protection. Together, these data identify hepatic {gamma}{delta} T cells as targets for the improvement of tissue-resident CD8+ T cell responses against hepatotropic pathogens.

An uncontrolled and rapidly growing outbreak of Bundibugyo virus (BDBV) is currently gripping the Democratic Republic of the Congo and threatening health security across Central Africa. There are no available BDBV-specific vaccines, although emerging evidence suggests that the Ebola virus-specific vaccine, rVSV-EBOV (also known by its tradename ERVEBO), may offer cross-protective immunity. To directly address this question, we evaluated the efficacy of rVSV-EBOV in the uniformly lethal ferret model of BDBV infection. All vaccinated animals survived BDBV challenge and exhibited minimal clinical signs of infection, presumably as a result of a moderate--but protective--humoral immune response. These findings provide critical evidence further supporting the cross-protective efficacy of rVSV-EBOV, and they suggest a potential role for this vaccine in mitigating the ongoing BDBV outbreak.

The continued emergence of betacoronaviruses underscores the urgent need for vaccines that provide broadly protective immunity. Here, we present an epitope-focused vaccine strategy targeting the conserved S2 stem-helix region of the spike fusion machinery, a broadly neutralizing antibody-(bnAb) epitope shared across betacoronaviruses yet partially occluded on the native spike. Immunization of non-human primates with engineered S2 stem-helix nanoparticle immunogens, alone or followed by a SARS-CoV-2 BA.1 spike mRNA boost, elicited broadly cross-reactive antibody responses against sarbecoviruses, merbecoviruses, and embecoviruses and neutralized SARS-CoV-2, multiple variants, other sarbecoviruses, and MERS-CoV. Vaccine-elicited monoclonal antibodies displayed broad in-vitro neutralizing activity and protected against both SARS-CoV-2 and MERS-CoV in-vivo. Structural analyses revealed conserved features between rhesus and human stem-helix bnAbs, supporting the translational potential. Overall, our findings provide proof-of-concept that epitope-focused nanoparticle immunogens can target partially occluded, immunoquiescent bnAb epitopes, laying the groundwork for pan-betacoronavirus vaccines that provide broad protection and strengthen pandemic preparedness. ONE SENTENCE SUMMARYEpitope-focused S2 stem-helix nanoparticle immunogens elicit protective broadly neutralizing antibodies (bnAbs) against diverse betacoronaviruses in non-human primates, establishing a framework for development of pan-betacoronavirus vaccines.

Despite suppressive antiretroviral therapy, many people with HIV (PWH) retain chronic interferon-associated immune dysregulation. Observational data from the Swiss HIV Cohort Study linked asymptomatic mycobacterial exposure to lower viral set points, reduced interferon-associated activity, and attenuated HIV-specific antibody responses, a pattern sharing features with HIV elite controllers and natural hosts of primate lentiviruses. We therefore examined whether Bacillus Calmette-Guerin (BCG) vaccination could induce a related immune configuration in ART-treated PWH. Using longitudinal systems-level profiling within the BELIEVE trial, we found that BCG reduced constitutive NK cell IFN-{gamma} production and PBMC-mediated direct cytotoxicity without impairing inducible cytokine responses or antibody-dependent cellular cytotoxicity. Multiomic and proteomic analyses showed reduced interferon- and activation-associated programs, while adaptive immune parameters remained largely stable and follow-up revealed no obvious adverse clinical pattern. This configuration, reduced baseline interferon activity coexisting with preserved Fc-dependent effector function, shares selected features with immune states described in natural lentiviral control and provides a rationale for testing BCG in combination with antibody-based HIV interventions.

With the rapid advancement of mRNA vaccines, lipid nanoparticles (LNPs) have emerged as pivotal carriers and adjuvants for non-mRNA vaccine modalities, driven by their superior nucleic acid delivery efficiency and intrinsic self-adjuvanting properties. In this study, we systematically evaluated various formulation strategies combining LNPs and the CpG adjuvant within a varicella-zoster virus glycoprotein E (VZV-gE) subunit vaccine framework. We demonstrated that uniform nanoparticles formed by LNP-encapsulated CpG (LNP-CpG), when simply admixed with the gE antigen, elicited superior immunogenicity compared to alternative encapsulation configurations. Intramuscular administration of a two-dose (LNP-CpG)+gE regimen significantly augmented both humoral and cellular immune responses in mice, markedly outperforming the commercial vaccine Shingrix (administered at a 1/10 human dose). Crucially, the identical regimen induced robust, comparable immune profiles to a full human dose of Shingrix in rhesus macaques. Furthermore, LNP-CpG displayed broad-spectrum utility across diverse vaccine platforms, demonstrating efficacy against both respiratory (RSV) and neurotropic (HSV) pathogens, compatibility with multiple modalities, including subunit (VZV-gE, RSV-Pre-F), live-attenuated (LA-HSV), and inactivated (i-HSV) vaccines; and versatile implementation in a combined VZV+RSV formulation. Collectively, our findings position LNP-CpG as a versatile, safe, highly efficacious adjuvant platform with substantial clinical translational potential, offering a compelling paradigm for next-generation vaccine development.

Echovirus 18 (E18) is a predominant pathogen causing aseptic meningitis in children, and post-E18 infection frequently triggers myasthenia gravis-like autoimmune neurological damage. This pathological process relies on neonatal Fc receptor (FcRn)-mediated IgG transcytosis across mucosal barriers, and FcRn also acts as an essential functional receptor required for E18 attachment and uncoating during host cell invasion. At present, no E18-specific prophylactic vaccine has been clinically approved, and anti-FcRn monoclonal antibodies are the available therapeutics to alleviate autoantibody-mediated tissue injury. We constructed an integrated automated phylogenetic pipeline named evolution_conservation, which enables rapid tracing of the evolutionary position and genetic relatedness of clinical isolates to identify closely related strains from previous outbreaks. Serving as an in silico alternative to animal experiments, this pipeline supports reference-guided vaccine design and longitudinal comparative assessment of vaccine safety and efficacy, facilitates identification of patient populations presenting rare post-viral sequelae, and accelerates clinical trial progression. In this study, we inserted the pre-screened linear epitope E18-3 into a truncated hepatitis B core (HBc) scaffold to generate chimeric virus-like particles (VLPs). A non-invasive floss-based gingival mucosal immunization mouse model was established, with subcutaneous Freunds adjuvant immunization set as the control group. ELISA results confirmed that gingival mucosal delivery of particulate HBc-E18-3 VLPs alone could induce sustained high levels of antigen-specific intestinal IgG in vivo. Drawing on research paradigms of therapeutic neoantigen vaccines for tumor recurrence prevention, the evolution_conservation bioinformatic pipeline and mucosal VLP platform described herein establish an innovative framework for developing antigen-competitive prophylactic and therapeutic vaccines targeting FcRn for myasthenia gravis and autoimmune encephalitis.

Introduction Respiratory syncytial virus (RSV) is an important cause of respiratory disease in older adults and adults with chronic medical conditions, contributing substantially to the healthcare burden in Italy. The availability of effective RSV vaccines provides an opportunity to reduce RSV-related morbidity, mortality, and healthcare costs in populations at high risk of severe disease. This study evaluates the potential public health impact and cost-effectiveness of vaccination using mRNA-1345 administered as a single dose compared with no vaccination in Italian high-risk adults aged 60-74 years and all adults aged [&ge;]75 years. Methods A static decision-analytic model was developed to project clinical and economic outcomes over a 5-year time horizon. Economic outcomes were evaluated from the Italian National Health Service (Servizio Sanitario Nazionale, SSN) perspective. Model inputs were informed by the most recent Italian epidemiological, clinical, and economic evidence, supplemented by published international data when necessary. Deterministic, probabilistic, and scenario analyses were conducted to assess the impact of uncertainty in model inputs and assumptions on the study results. Results Vaccination with mRNA-1345 in high-risk adults aged 60-74 years and all adults aged [&ge;]75 years was projected to avert over 19,800 hospitalizations, 4,000 emergency department visits, 381,000 outpatient visits, 6,000 RSV-attributable deaths, and 212,000 antibiotic prescriptions compared with no vaccination over a 5-year period. The total incremental cost of {euro}1,143 million and the additional 47,477 QALYs gained resulted in an ICER of {euro}24,078, which was below the commonly referenced willingness to-pay range of {euro}33,000-40,000 per QALY gained. Sensitivity analyses confirmed robustness of the analysis results. Conclusions Vaccination with mRNA-1345 is a cost-effective strategy for the prevention of RSV in high-risk adults aged 60-74 years and all adults [&ge;]75 years in Italy and has the potential to provide substantial public health benefits.

Background: Peptide cancer vaccines can elicit antigen-specific immunity, but peripheral immunogenicity often does not translate into durable tumor control. Methods: We analyzed transcriptomic profiles across three public human peptide-vaccine cohorts: C1/GSE278476, a MUC1 plus Poly-ICLC PBMC RNA-seq cohort with ordered anti-MUC1 IgG response classes; C2/GSE85698, manufactured dendritic-cell vaccine preparations linked to TARP ELISpot response; and C3/GSE53922, baseline PBMC expression linked to overall survival after personalized peptide vaccination in castration-resistant prostate cancer. Prespecified gene modules were summarized as mean standardized scores and tested with endpoint-appropriate cohort-level models with within-family FDR control. Results: Baseline immune-readiness was favorable in C1 (beta=0.301, p=0.0072, q=0.093; permutation p=0.0088) and associated with longer survival in C3 (HR=0.662, 95% CI 0.532-0.823, p=0.000206, q=0.00126). Baseline erythroid/inflammatory drag showed the opposite direction in C1 (beta=-0.258, p=0.031, q=0.202; permutation p=0.0324) and was associated with inferior survival in C3 (HR=1.390, 95% CI 1.181-1.636, p=0.0000755, q=0.000982). In C2, lower tolerogenic/myeloid dendritic-cell product-state expression was observed in strong ELISpot responders (8/19 focused genes q<0.05). At C1 week 2, a priming/costimulation/mTOR-AKT module showed an FDR-significant cross-sectional association with response class (permutation p=0.0026), but paired within-person change was not significant. Conclusions: Public peptide-vaccine transcriptomic data support a phase-linked model in which host readiness, erythroid/inflammatory drag, dendritic-cell product state, and early priming are measurable response-linked layers. These retrospective cohorts do not establish causality, biomarker status, clinical utility, or durable tumor control.

Efforts to develop a universal influenza vaccine have primarily focused on the surface-exposed viral hemagglutinin (HA), but neuraminidase (NA) is an additional target for cross-reactive, protective responses. Here, we used hyperglycosylation as an immunogen design approach to reshape anti-NA humoral immunity toward conserved antigenic regions. Iterative design produced a hyperglycosylated NA immunogen that retained enzymatic activity and reactivity to a conformation-specific antibody recognizing the conserved catalytic site. In mice, the hyperglycosylated immunogen elicited serum antibody responses of comparable magnitude to those elicited by the wild-type NA immunogen. However, serum antibodies elicited by the hyperglycosylated immunogen had increased breadth, recognizing N2 NAs from H2N2 and H3N2 viruses spanning nearly 65 years of antigenic drift, as well as a heterosubtypic N9 NA. Single B cell analyses identified a monoclonal antibody that competed with a component of the serum antibody response elicited by the hyperglycosylated immunogen, and structural characterization showed that it recognizes a previously undefined, conserved epitope at the NA tetramer interface. Passive transfer of this interface-directed antibody partially protected mice against lethal heterologous influenza challenge. Collectively, these data show that glycan shielding can reshape and enrich humoral responses toward a conserved antigenic region on NA. The immunogen and hyperglycosylation design strategy described here provide a template for developing next- generation NA-based influenza vaccines. ONE SENTENCE SUMMARYA hyperglycosylated influenza neuraminidase immunogen reshapes humoral immunity and elicits antibodies targeting a conserved tetramer-interface epitope.

Background: Patients receiving anti-TNF treatment for chronic inflammatory disease display impaired antibody responses, but it remains unclear how immune memory formation is affected. We evaluated antibody responses and memory B cells (Bmem) after COVID-19 booster vaccination in inflammatory bowel disease (IBD) patients receiving anti-TNF treatment. Methodology: Blood was sampled at baseline, 1, and 6 months after WH1/BA.5 bivalent or XBB.1.5 monovalent vaccination from 27 IBD patients receiving intravenous anti-TNF and 44 controls. Neutralizing antibodies were measured using an infectious virus assay. SARS-CoV-2 spike receptor binding domain (RBD)-specific serum IgG was quantified by ELISA, and RBD-specific Bmem were immunophenotyped by flow cytometry using recombinant proteins from ancestral, Omicron BA.1, BA.5, XBB.1.5, and JN.1 variants. Results: Serum IgG to vaccine RBD and neutralizing antibodies in patients increased pre to 1 month post-vaccination, but were lower than controls. Ancestral-, BA.5- and XBB.1.5-specific Bmem increased after vaccination but were significantly lower in patients than controls. Within RBD-specific Bmem, frequencies of recently activated CD21lo cells were increased after vaccination, and were higher in patients than controls. Fewer antigen-specific Bmem in patients expressed IgG4, and more expressed IgG3 or IgD following vaccination. Following vaccination, more RBD-specific Bmem recognized multiple viral variants. However, patients had fewer Bmem that could bind to subvariants than controls. Conclusion: Antibody and Bmem responses to COVID-19 booster vaccination in anti-TNF-treated IBD patients displayed reduced capacity, durability and cross-reactivity, suggesting impaired immune memory for protection against breakthrough infection. This supports the recommendation for annual booster vaccination to prevent severe disease and viral spread.

The intravacuolar parasite Toxoplasma gondii scavenges fatty acids from host mammalian cells and stores excess in lipid droplets. To investigate the physiological relevance of neutral lipid storage in Toxoplasma, we generated a mutant lacking DGAT1, an ER-localized enzyme that synthesizes triacylglycerols, from the virulent type I RH strain of T. gondii. Compared to WT, RH {Delta}DGAT1 parasites grow poorly in mammalian cells, form few LD, suffer from lipotoxicity, and do not cause disease or lethality in immunocompetent or immunodeficient mice. Importantly, mice immunized with RH {Delta}DGAT1 parasites mount strong, long-term immune responses involving both cellular and humoral components, with higher levels of T. gondii-specific IgG antibodies, effector memory T cells, and both pro-inflammatory and anti-inflammatory cytokines, indicating a mixed Th1/Th2 response with Th1 predominance. This immunity provides complete, long-lasting protection (up to 6 months) against rechallenge from homologous type I (acute infection) and heterologous cyst-forming type II (chronic infection) T. gondii strains. Additional analyses reveal that IFN-{gamma}, CD8+ T cells, as well as B cells are crucial for defending against type I T. gondii in immunized mice. Overall, our live-attenuated RH {Delta}DGAT1 strain is a promising vaccine candidate and a model for studying immune responses that control T. gondii infections.

Personalized neoantigen (neoAg) vaccines have shown clinical promise in solid tumors1-8, yet their efficacy and mechanism of action in hematopoietic malignancies remain poorly defined9-11. Herein, we establish an immunocompetent syngeneic A20 B-cell lymphoma platform to test the efficacy of neoAg vaccines used either as mono- or combinatorial therapies with other immunotherapies12-17. Whereas subcutaneous A20 tumors were refractory to single-agent PD-1 or CTLA4 therapy, they were eradicated in a T cell-dependent manner in 90% of syngeneic hosts treated with dual immune checkpoint therapy (dual ICT, i.e., PD-1 + CTLA4). By mapping antigen specificity of dual-ICT-elicited T cells, we identified and validated dominant endogenous A20 MHC-I and MHC-II neoantigens and designed therapeutic synthetic long peptide (SLP) vaccines containing these neoepitopes. This vaccine (A20 neoVAX) promoted robust neoAg-specific CD4{square} and CD8{square} T cell responses in naive syngeneic BALB/c mice and induced tumor rejection in [~]70% of subcutaneous tumor-bearing mice. In addition, nearly all mice rejected their subcutaneous A20 tumors when A20 neoVAX was combined with PD-1. To render the results of this study more physiologic, we developed a systemic A20 lymphoma model and found that dual ICT failed to control tumor progression and A20 neoVAX delayed tumor progression and prolonged animal survival but did not induce tumor rejection. In contrast, A20 neoVAX plus dual ICT achieved durable systemic tumor elimination. Mechanistically, the combination of A20 neoVAX plus dual ICT amplified priming of A20 neoAg-specific T cells, prevented T cell dysfunction, sustained the cytotoxic capacity of tumor-specific CD8+ T cells, and induced Th1-skewing of CD4+ T cells in tumor and peripheral compartments. To increase the clinical relevance of these findings and to minimize potential adverse events in tumor-bearing, therapeutically treated individuals, we substituted CD8-targeted cytokine muteins (CD8-IL2 or CD8-IL21) for CTLA4. These agents represent genetically modified forms of IL-2 or IL-21 that selectively stimulate CD8+ T cells but have significantly reduced capacity to activate chronic inflammation and immunosuppressive functions of other immune cells. Whereas mice bearing systemic A20 lymphoma treated with either nothing, A20 neoVAX, or A20 neoVAX + CD8-IL2 failed to control tumor outgrowth, 66.7% of tumor-bearing mice treated with A20 neoVAX + CD8-IL2 + PD-1 rejected their tumors. In similar experiments in which CD8-IL21 was substituted for CD8-IL2, tumor clearance was also observed in two-thirds of A20-bearing mice but now rejection occurred in the absence of PD1. Together, these data define a framework for optimal personalized neoAg vaccination in B-lymphoma and demonstrate that neoAg vaccines can safely synergize with CD8+ T cell-selective immunotherapies to prevent T-cell dysfunction and generate durable systemic anti-tumor immunity.

A major goal for hepatitis C virus (HCV) vaccine development is to elicit broadly neutralizing antibodies (bNAbs) against the E1E2 glycoprotein complex located on the viral surface. Inducing HCV bNAbs requires engagement of their germline B cell precursors. HCV glycoproteins usually do not bind and activate inferred germline precursors of bNAbs (igl-bNAbs), possibly because most circulating strains contain non-conserved isolate-specific residues, even in bNAb epitopes. Here, we generated stabilized native-like soluble E1E2 (sE1E2) antigens based on a consensus sequence of HCV (HepCon) to limit the exposure of antigenically rare residues. The antigenicity and glycosylation profiles show that HepCon sE1E2 resembles a native-like E1E2 heterodimer. HepCon sE1E2 induced cross-reactive neutralizing antibody responses as a soluble protein immunogen and as membrane-anchored mRNA-delivered immunogen in animals. Importantly, HepCon sE1E2 engages multiple igl-bNAbs against two major epitopes: antigenic region 3 (AR3), which is targeted by igl-bNAbs derived from the widely expressed human VH1-69 B cell gene, and antigenic region 4 (AR4), which is only present on native-like E1E2. Nanoparticles with HepCon sE1E2 efficiently activated B cell lines expressing AR3 and AR4 igl-bNAb B cell receptors in vitro. Finally, using HepCon sE1E2 we elucidated the atomic contacts of an AR3 igl-bNAb by cryo-electron microscopy. Thus, HepCon sE1E2 is a promising candidate for germline-targeting vaccination strategies.