Pre-existing Antibodies Research Articles

Development of a validated novel bead extraction method for the detection of anti-PEG antibodies in human serum.

Polyethylene glycol (PEG) is used in many applications including drug development. Due to exposure to environmental products, there is a high prevalence of preexisting anti-PEG antibodies in the global human population. The presence of anti-PEG antibodies is a concern for potentially reducing the efficacy of therapeutics after administration and represents a risk of safety events after exposure to PEGylated drug products. We developed and validated a creative and sensitive method for the detection of anti-PEG antibodies in human serum to support clinical programs for PEGylated drugs. In this method, biotin-PEG streptavidin beads were used to extract anti-PEG antibodies from human serum for analysis in an anti-PEG ELISA assay. The same serum sample was analyzed in an anti-drug antibody assay. The anti-PEG antibody assay was validated with a screening cut point of 1.41 normalized signal, confirmatory cut point of 32.2% inhibition, sensitivity of 7.81 ng/mL and sufficient reproducibility, selectivity, and drug tolerance in accordance with the FDA 2019 Immunogenicity guidance. This method of removal of anti-PEG antibodies enables the use of a single sample to detect anti-drug and anti-PEG antibodies to support drug development programs.

Differential antigenic imprinting effects between influenza H1N1 hemagglutinin and neuraminidase in a mouse model.

Influenza viruses continue to pose a significant threat to human health, with vaccine effectiveness remaining a persistent challenge. Individual immune history is a crucial factor that can influence antibody responses to subsequent influenza exposures. While many studies have explored how pre-existing antibodies shape the induction of anti-HA antibodies following influenza virus infections or vaccinations, the impact on anti-NA antibodies has been less extensively studied. Using a mouse model, our study demonstrates that within pre-2009 H1N1 strains, an extensive immune history negatively impacted anti-HA antibody responses but enhanced anti-NA antibody responses. However, in response to the 2009 pandemic H1N1 strain, which experienced an antigenic shift, both anti-HA and anti-NA antibody responses were hindered by antibodies from prior pre-2009 H1N1 virus infections. These findings provide important insights into how antigenic imprinting affects both anti-HA and anti-NA antibody responses and underscore the need to consider immune history in developing more effective influenza vaccination strategies.

Relevance of Neutralizing Antibodies for the Pharmacokinetics of Pegunigalsidase Alfa in Patients with Fabry Disease.

Pegunigalsidase alfa is a newly approved drug for the treatment of Fabry disease, designed to increase the plasma half-life and reduce immunogenicity of infused α-galactosidase A (AGAL). We provide the first comprehensive pharmacokinetic and immunogenic data apart from industry-initiated studies. Pharmacokinetics of pegunigalsidase alfa, amino acid, and polyethylene glycol (PEG)-specific antibodies and immunecomplexes were measured in treated patients (11 switched, two naïve). Measurements were performed in serum samples drawn directly before and after infusions over three to ten consecutive infusions. Only three patients started directly with 1.0 mg/kg body weight. No infusion-associated reactions were reported under pegunigalsidase alfa during the observation. Patients without pre-existing neutralizing anti-AGAL antibodies showed high enzymatic AGAL peak activities and sustained AGAL serum concentrations until the next infusion, which was not observed in those with neutralizing anti-AGAL antibodies. Nine (69.2%) patients presented with pre-existing anti-PEG antibodies (IgG or IgM), which seemed to have no impact on pharmacokinetics during the observation. No new anti-PEG or anti-AGAL antibody formation was observed after treatment initiation. Three (75.0%) patients with pre-existing neutralizing anti-AGAL antibodies showed a titer increase and one (25.0%) patient a decrease. In patients with anti-AGAL antibodies (n = 4) immune-complex formation was detected. The pharmacokinetics of pegunigalsidase alfa show different profiles depending on the presence of pre-existing neutralizing antibodies, with reduced plasma half-life and peak enzyme activity after infusion in patients with antibodies. The clinical significance of a reduced pegunigalsidase alfa half-life and the formation of immune complexes in antibody-positive patients needs to be analyzed in future studies.

RVG29-modified oncolytic herpes simplex virus for intracranial tumor treatment

Oncolytic virus therapy for brain tumors has achieved breakthrough progress in clinical applications, yet its potential is severely constrained by the mode of administration-direct intratumoral injection into the cranial cavity. Other administration routes face rapid clearance by neutralizing antibodies and obstacles posed by the blood-brain barrier. Herein, we engineered the oncolytic herpes simplex virus type 2 (OH2) with surface modifications of polyethylene glycol (PEG) and rabies virus glycoprotein 29 (RVG29, a BBB-penetrating peptide from the rabies virus), to form OH2-PEG-RVG. OH2-PEG-RVG could efficiently traversed the blood-brain barrier even in BALB/c mice with pre-existing anti-OH2 antibodies, leading to the accumulation of OH2 in the brain. More importantly, OH2-PEG-RVG maintained blood-brain barrier integrity without causing pathological changes or behavioral abnormalities in mice. Furthermore, OH2-PEG-RVG effectively inhibited brain tumor growth, transforming immunologically "cold" tumors into "hot" tumors, inducing a robust anti-tumor immune response, and prolonging the survival of the mice. These findings underscore the potential of OH2-PEG-RVG as a multifaceted therapeutic strategy for effective brain tumor treatment, offering insights into addressing blood-brain barrier limitations.

Longitudinal Immunological Analysis of Portuguese Healthcare Workers Across the COVID-19 Pandemic Reveals Differences in the Humoral Immune Response to Vaccines

Background: A vaccination programme against severe acute respiratory syndrome coronavirus 2 was initiated in Portugal in December 2020. In this study, we report the findings of a prospective cohort study implemented with the objective of monitoring antibody production in response to COVID-19 vaccination. Methods: The humoral immune response to vaccination was followed up using blood samples collected from 191 healthcare workers. Participants were split into three groups: the Oxford-AstraZeneca (Vaxzevria) vaccine group (n = 68), the Pfizer-BioNTech COVID-19 (Comirnaty) vaccine group (n = 51), and the Post-COVID group (n = 72). The kinetics of anti-spike antibody production were evaluated until 56 days on average after the third dose (booster). Results: We observed that antibody titres peaked approximately one month after full vaccination and declined steadily thereafter. We also found that mRNA vaccination induces higher titres of antibodies than viral vector vaccination, and both generate greater antibody responses than mild or moderate COVID-19. Additionally, whilst the booster for the Oxford-AstraZeneca and Pfizer-BioNTech groups led to antibody levels higher than those at any previous sample collection point, the booster for the Post-COVID group (persons with a history of COVID-19 prior to vaccination) led to antibody levels lower than those attained one month after the second dose. Interpretation: Our results indicate that there are different kinetics of antibody production between individuals who received the Pfizer-BioNtech mRNA vaccine and those who received the Oxford-AstraZeneca vector vaccine, or individuals who had COVID-19 before being vaccinated. Additionally, we observed that exposure to either natural infection or vaccination modulates the response to subsequent vaccination. This is particularly evident after administration of the third dose to the Post-COVID group, where our findings point to a hindrance in vaccine boosting, probably due to unwanted feedback by high titres of pre-existing antibodies.

Modulation of B cell receptor activation by antibody competition.

During repeated virus exposure, pre-existing antibodies can mask viral epitopes by competing with B cell receptors for antigen. Although this phenomenon has the potential to steer B cell responses away from conserved epitopes, the factors that influence epitope masking by competing antibodies remain unclear. Using engineered, influenza-reactive B cells, we investigate how antibodies influence the accessibility of epitopes on the viral surface. We find that membrane-proximal epitopes on influenza hemagglutinin are fundamentally at a disadvantage for B cell recognition because they can be blocked by both directly and indirectly competing antibodies. While many influenza-specific antibodies can inhibit B cell activation, the potency of masking depends on proximity of the targeted epitopes as well as antibody affinity, kinetics, and valency. Although most antibodies are inhibitory, we identify one that can enhance accessibility of hidden viral epitopes. Together, these findings establish rules for epitope masking that could help advance immunogen design.

Abstract 4138738: Clinical Evidence of Immune Response to Transplanted Allogeneic iPS Cell-Derived Cardiomyocytes

Background&Purpose: The clinical application of cell transplantation therapy utilizing induced pluripotent stem cells (iPS cells) for heart failure is progressing, with the primary strategy being the use of pre-prepared allogeneic iPS cells. The immune response to these transplanted cells is crucial and may affect therapeutic efficacy, necessitating the use of immunosuppressive drugs. However, detailed clinical reports on immune responses are sparse. This study aims to analyze the immune response to transplanted cells in clinical iPS cell-derived cardiomyocyte (iPSC-CM) transplants and examine the correlation between immune response and therapeutic efficacy. Methods: In the "Phase 1 multicenter clinical trial of transplantation of iPSC-CMs for ischemic cardiomyopathy" (https://jrct.niph.go.jp/en-latest-detail/jRCT2053190081), conducted as the First-in-Human trial, the immune response to transplanted cells was analyzed in four cases at our hospital. Comprehensive analysis of anti-human leukocyte antigen (HLA) antibodies in serum and single-cell RNA sequencing in peripheral blood mononuclear cells was performed to investigate their relationship with therapeutic effects on cardiac function. Results: Patients received immunosuppressive drugs (tacrolimus, mycophenolate mofetil, and steroids) for 3 months post-transplantation, followed by a 1-year follow-up. In all cases, an increase in transplant cell HLA-specific antibodies was observed after discontinuing immunosuppressive drugs (Figure 1 and 2). Single-cell analysis revealed a decrease in immunocompetent cells in peripheral blood during immunosuppressive therapy. Cardiac function analysis showed improvements in all cases except Case 2 (Figure 3), where pre-existing anti-HLA-DQ antibodies were present before transplantation. Conclusions: No immune response to the transplanted cells was observed during immunosuppressive therapy. In a case with limited therapeutic response, pre-existing antibodies to transplanted cells were detected, potentially impacting the therapeutic outcome.

RVSV-ZEBOV vaccination in people with pre-existing immunity to Ebolavirus: an open-label safety and immunogenicity study in Guinean communities affected by Ebola virus disease (l’essai proches)

BackgroundZaire Ebolavirus disease (EVD) outbreaks can be controlled using rVSV-ZEBOV vaccination and other public health measures. People in high-risk areas may have pre-existing antibodies from asymptomatic Ebolavirus exposure that might affect response to rVSV-ZEBOV. Therefore, we assessed the impact pre-existing immunity had on post-vaccination IgG titre, virus neutralisation, and reactogenicity following vaccination.MethodsIn this prospective cohort study, 2115 consenting close contacts (“proches”) of EVD survivors were recruited. Proches were vaccinated with rVSV-ZEBOV and followed up for 28 days for safety and immunogenicity. Anti-GP IgG titre at baseline and day 28 was assessed by ELISA. Samples from a representative subset were evaluated using live virus neutralisation.ResultsTen percent were seropositive at baseline. At day 28, IgG in baseline seronegative (GMT 0.106 IU/ml, 95% CI: 0.100 to 0.113) and seropositive (GMT 0.237 IU/ml, 0.210 to 0.267) participants significantly increased from baseline (both p < 0.0001). There was strong correlation between antibody titres and virus neutralisation in day 28 samples (Spearman’s rho 0.75). Vaccinees with baseline IgG antibodies against Zaire Ebolavirus had similar safety profiles to those without detectable antibodies (63.6% vs 66.1% adults experienced any adverse event; 49.1% vs 60.9% in children), with almost all adverse events graded as mild. No serious adverse events were attributed to vaccination. No EVD survivors tested positive for Ebolavirus by RT-PCR.ConclusionsThese data add further evidence of rVSV-ZEBOV safety and immunogenicity, including in people with pre-existing antibodies from suspected natural ZEBOV infection whose state does not blunt rVSV-ZEBOV immune response. Pre-vaccination serological screening is not required.

Analysis of Measles and Rubella Immunoglobulin G Titers in COVID-19 Patients.

The objective of this study is to compare the measles immunoglobulin G (IgG) and rubella IgG levels in patient groups with mild and severe COVID-19 disease and reveal the possible relationship. This study was conducted among COVID-19-confirmed patients over 18, under 65 years of age. This study involved 75 participants- divided into two groups. The first group usually comprised asymptomatic patients who did not require hospitalization (n=43), and the second group consisted of patients who had diffuse pneumonia on thoracic CT and required hospitalization (n=32). Anti-measles and anti-rubella IgG titers were detected to be higher in the group with severe disease compared to the group with mild disease (p=0.001 and p=0.001, respectively). The analyses were repeated by taking n=27 in Group 1 and n=27 in Group 2, which were similar in terms of age, gender and number. In the analysis performed without any age difference between the groups, no significant difference was found between the two groups in terms of Anti Measles IgG antibody titers (p=0.068). However, Anti Rubella antibody titers were found to be higher in the group with severe COVID-19 disease than in those with mild disease (p=0.03). Regardless of the severity of the disease, there was a positive correlation between Anti Rubella and Anti Measles IgG antibody titers and age (p=<0.001 Spearman's rho 0.517; p=0.008 Spearman's rho 0.304, respectively). We believe that the pre-existing Anti-Rubella IgG antibodies in the patient may increase in parallel with the patient's viral load by recognizing the common macrodomain of SARS-CoV-2 and Rubella viruses. The common macrodomain of SARS-CoV-2 and Rubella viruses is also present in the attenuated rubella virus used in the MMR vaccine4. In this case, we predict that previously administered MMR vaccine may be protective for COVID-19 patients. disease compared to those with mild disease.

Complex immunogenicity assessment in caplacizumab-treated patients with immune-mediated thrombotic thrombocytopenic purpura who have received plasma exchange

BackgroundISTH guidelines for immune-mediated thrombotic thrombocytopenic purpura (iTTP) treatment recommend concurrent therapeutic plasma exchange (TPE), immunosuppressive therapy (IST), and caplacizumab. TPE can complicate anti-drug antibody (ADA) measurements by transferring pre-existing antibodies (pre-Abs) into patients via donor plasma and/or diluting treatment-emergent (TE) ADAs. ObjectivesTo assess the presence of ADAs in patients with iTTP who received caplacizumab. MethodsImmunogenicity data from patients with iTTP receiving caplacizumab once daily plus TPE/IST in four clinical trials (TITAN, HERCULES, Post-HERCULES, and a trial conducted in Japanese patients) in the clinical development program were analyzed. ADA and modified ADA (mADA) assays differentiated pre-Abs from TE ADAs. A functional neutralizing antibody (NAb) assay and neutralizing epitope characterization assay (NECA) assessed the presence of ADAs with neutralizing potential. The impact of ADAs on efficacy, pharmacokinetics/pharmacodynamics, and safety was evaluated. ResultsAmong 228 patients in four studies, prevalence of pre-Abs ranged from 17.1% (TITAN) to 56.7% (HERCULES), while TE ADA prevalence ranged from 3.1% (HERCULES) to 14.3% (Japanese study). The TE NAb-positive rate ranged from 0% (Japanese study) to 12% (Post-HERCULES) using the functional NAb assay and from 2.7% (Post-Hercules) to 14.3% (Japanese study) using NECA. The presence of these antibodies did not impact treatment efficacy or safety. ConclusionsA complex immunogenicity assay strategy was required to define the pre-Ab/TE ADA status of patients with iTTP treated with caplacizumab in a clinical trial setting. In addition to the wide range of pre-Abs observed, few patients had detectable TE ADAs or NAbs, neither of which impacted on efficacy/safety.

Comparative assessment of the transduction efficiency and safety associated with the delivery of AAV9-GFP vector via lumbar puncture route to juvenile cynomolgus macaques with and without anti-AAV9 pre-existing antibodies

Comparative assessment of the transduction efficiency and safety associated with the delivery of AAV9-GFP vector via lumbar puncture route to juvenile cynomolgus macaques with and without anti-AAV9 pre-existing antibodies

Characterization of anti-AAV2 neutralizing antibody levels in sheep prior to and following intravitreal AAV2.7m8 injection

Gene augmentation therapy is a promising treatment for incurable, blinding inherited retinal diseases, and intravitreal delivery is being studied as a safe alternative to subretinal injections. Adeno-Associated Viruses (AAV) are commonly-used vectors for ocular gene augmentation therapy. Naturally occurring pre-operative exposure and infection with AAV could result in presence of neutralizing antibodies (NAB’s) in patients’ serum, and may affect the safety and efficacy of treatment. Our aim was to characterize the humoral response against AAV pre- and post-intravitreal delivery of AAV2.7m8 vectors in a naturally-occurring sheep model of CNGA3 achromatopsia. Serial serum neutralization assays were performed to screen sheep for pre-exiting anti-AAV2 NAB’s, and to assess the effect of intravitreal AAV2.7m8 injection on post-operative NAB titers and intraocular inflammation in sheep. The effect of viral dose and transgene type were also assessed. Serological screening revealed pre-operative seropositivity in 21.4% of animals, with age being a risk factor for the presence of anti-AAV2 NAB’s. NAB titers increased following intravitreal AAV administration in the majority of sheep. There was no significant difference in the degree of post-operative serum neutralization between pre-operatively seronegative sheep and those with pre-existing antibodies. However, only sheep with pre-existing antibodies presented with signs of post-operative inflammation. We conclude that pre-existing anti-AAV2 NAB’s do not affect the level of post-operative NAB titers; however, they increase the risk of post-operative ocular inflammation. Our results could have implications for the management of AAV-mediated ocular gene therapies, a technology being increasingly studied and used in patients.

Exploring the Contrasts and Similarities of Dengue and SARS-CoV-2 Infections During the COVID-19 Era.

Extensive research has been conducted on the SARS-CoV-2 virus in association with various infectious diseases to understand the pathophysiology of the infection and potential co-infections. In tropical countries, exposure to local viruses may alter the course of SARS-CoV-2 infection and coinfection. Notably, only a portion of the antibodies produced against SARS-CoV-2 proteins demonstrate neutralizing properties, and the immune response following natural infection tends to be temporary. In contrast, long-lasting IgG antibodies are common after dengue virus infections. In cases where preexisting antibodies from an initial dengue virus infection bind to a different dengue serotype during a subsequent infection, there is a potential for antibody-dependent enhancement (ADE) and the formation of immune complexes associated with disease severity. Both SARS-CoV-2 and dengue infections can result in immunodeficiency. Viral proteins of both viruses interfere with the host's IFN-I signaling. Additionally, a cytokine storm can occur after viral infection, impairing a proper response, and autoantibodies against a wide array of proteins can appear during convalescence. Most of the reported autoantibodies are typically short-lived. Vaccines against both viruses alter the immune response, affecting the course of viral infection and enhancing clearance. A comprehensive analysis of both viral infections and pathogenicity is revisited to prevent infection, severity, and mortality.

IL-12 encoding oNDV synergizes with CAR-T cells in orthotopic models of non-small cell lung cancer

Systemic administration of oncolytic viruses (OVs) is a promising approach for targeting metastatic solid tumors, but their anti-tumor activity is limited by pre-existing neutralizing antibodies against common human viruses. Therefore, investigators have developed OVs derived from non-human host viruses. Successful implementation of this strategy requires that the viral vector selectively infects and replicates within human cancer cells. Newcastle disease virus (NDV) is an avian paramyxovirus that as NDV-based OVs (oNDVs) have demonstrated safety and activity against multiple human tumors in clinical trials. Their use as a single agent, however is insufficient to cure tumors. Similarly, CAR-T cells enable systemic targeting of cancer cells but have limited anti-tumor effects against bulky solid tumors, in part due to the immunosuppressive tumor environment. In this study, we evaluated the anti-tumor effects of combining systemic oNDV and CAR-T cell treatments. In models of non-small cell lung carcinoma (NSCLC), we found that oNDV itself and IL-12 derived from oNDV enhance HER2-directed CAR-T cell anti-tumor activity and persistence in vitro and in vivo, leading to superior control of NSCLC tumors compared with either agent alone in vivo. Our data indicate that oNDV enhances the anti-tumor effects of HER2.CAR-T cells, thus controlling the growth of orthotopic NSCLC tumors.

Plasma exchange and intravenous immunoglobulin prolonged the survival of a porcine kidney xenograft in a sensitized, deceased human recipient.

The primary limitation to kidney transplantation is organ shortage. Recent progress in gene editing and immunosuppressive regimens has made xenotransplantation with porcine organs a possibility. However, evidence in pig-to-human xenotransplantation remains scarce, and antibody-mediated rejection (AMR) is a major obstacle to clinical applications of xenotransplantation. We conducted a kidney xenotransplantation in a deceased human recipient using a porcine kidney with five gene edits (5GE) on March 25th, 2024 at Xijing Hospital, China. Clinical-grade immunosuppressive regimens were employed, and the observation period lasted 22days. We collected and analyzed the xenograft function, ultrasound findings, sequential protocol biopsies, and immune surveillance of the recipient during the observation. The combination of 5GE in the porcine kidney and clinical-grade immunosuppressive regimens prevented hyperacute rejection. The xenograft kidney underwent delayed graft function in the first week, but urine output increased later and the single xenograft kidney maintained electrolyte and pH homeostasis from postoperative day (POD) 12 to 19. We observed AMR at 24h post-transplantation, due to the presence of pre-existing anti-porcine antibodies and cytotoxicity before transplantation; this AMR persisted throughout the observation period. Plasma exchange and intravenous immunoglobulin treatment mitigated the AMR. We observed activation of latent porcine cytomegalovirus toward the end of the study, which might have contributed to coagulation disorder in the recipient. 5GE and clinical-grade immunosuppressive regimens were sufficient to prevent hyperacute rejection during pig-to-human kidney xenotransplantation. Pre-existing anti-porcine antibodies predisposed the xenograft to AMR. Plasma exchange and intravenous immunoglobulin were safe and effective in the treatment of AMR after kidney xenotransplantation.

Adverse Impacts of PEGylated Protein Therapeutics: A Targeted Literature Review.

The beneficial effects of polyethylene glycol (PEG)-conjugated therapeutics, such as increased half-life, solubility, stability, and decreased immunogenicity, have been well described. There have been concerns, however, about adverse outcomes with their use, but understanding of those adverse outcomes is still relatively limited. The present study aimed to characterize adverse outcomes associated with PEGylation of protein-based therapeutics on immunogenicity, pharmacologic properties, and safety. A targeted review of English language articles published from 1990 to September 29, 2023, was conducted. Of the 29 studies included in this review, 18 reported adverse safety outcomes such as hematologic complications, hepatic toxicity, injection site reactions, arthralgia, nausea, infections, grade 3 or 4 adverse events (AEs), and AE-related discontinuations and dose modifications. Fifteen studies reported immunogenicity-related outcomes, such as the prevalence of pre-existing antibodies to PEG, treatment-emergent antibody response, and hypersensitivity reactions to PEGylated drugs. Seven studies reported pharmacological outcomes such as increased clearance and reduced activity in response to PEGylated drugs. This review aims to contribute to a balanced view of PEGylated therapies by summarizing the adverse outcomes or lack of benefit associated with PEGylated therapeutics reported in the literature. We identified several studies characterizing adverse outcomes, pharmacological effects, and immunogenicity associated with the use of PEGylated therapeutics. Our findings suggest that using PEGylated therapeutics may require careful monitoring for adverse safety outcomes, including screening and monitoring for pre-existing antibodies and those induced in response to PEGylated therapy, as well as monitoring and adjusting the dosing of PEGylated therapeutics.

Prevalence of Antibodies against Adeno-Associated Viruses (AAVs) in Göttingen Minipigs and Its Implications for Gene Therapy and Xenotransplantation

Adeno-associated viruses (AAV) are widely used as delivery vectors in clinical trials for in vivo gene therapy due to their unique features. Göttingen minipigs are a well-established animal model for several diseases and can be used for the efficacy and safety testing of AAV-based gene therapy. Pre-existing antibodies against AAV may influence the results of testing and, therefore, the animals should be tested for the presence of antibodies against relevant AAV serotypes. The detection of AAVs in pigs may be also important for the virus safety of xenotransplantation. In this study, we screened Göttingen minipigs from Ellegaard Göttingen Minipigs A/S, Denmark, and Marshall BioResources, USA, for antibodies against AAV1, AAV2, AAV6, AAV9 serotypes. Of the 20 animals tested, 18 had no neutralizing antibodies for all AAVs tested, none had antibodies against AAV9, only one had antibodies against AAV6, and the titers of antibodies against AAV1 and AAV2 were less than 1:100, with two exceptions. For total binding IgG, more individuals showed positivity for all the tested serotypes but, in general, the levels were low or zero. Three animals had no antibodies at all against the AAVs tested. Therefore, Göttingen minipigs could be considered an attractive animal model for gene therapy studies. Since some animals were negative for all AAVs tested, these may be selected and used as donor animals for xenotransplantation.

A novel orf virus vector-based COVID-19 booster vaccine shows cross-neutralizing activity in the absence of anti-vector neutralizing immunity

ABSTRACT Next-generation COVID-19 vaccines are being developed to expand the breadth of coverage against existing and future variants and to extend the duration of protection. Prime-2-CoV_Beta is an orf virus (ORFV) based multi-antigen COVID-19 vaccine that co-expresses Spike (S) and Nucleocapsid (N) antigens. The safety and immunogenicity of Prime-2-CoV_Beta is investigated in a phase 1 first-in-human (FIH) dose-finding trial (ORFEUS study, ClinicalTrials.gov: NCT05367843). Participants of two age groups (18–55 and 65–85 years) who previously completed at least two doses of mRNA vaccines were enrolled and sequentially assigned to different dose groups to receive one intramuscular dose of 3 × 105, 3 × 106, 1.5 × 107, or 3 × 107 plaque-forming units (PFU) of Prime-2-CoV_Beta on day 1 and a second dose on day 29. Here, we report safety and immunogenicity data collected up to 6 months after the first study vaccination. Prime-2-CoV_Beta is safe and well tolerated and elicits immune responses at higher dose levels in participants aged 18–55. A single dose of 3 × 107 PFU boosted binding and cross-neutralizing antibody responses that are maintained through 6 months after the first booster vaccination. Polyfunctional S-specific CD4+ and CD8+ T cell responses are observed after vaccination. No pre-existing or vaccine-induced neutralizing anti-vector antibodies are detected. Our findings highlight the potential of the ORFV vector as a safe platform for future vaccine design, which provides the ability to deliver multiple antigens and allows for repeat immunization.

Identification of a novel neutralization epitope in rhesus AAVs

Adeno-associated viruses (AAVs) are popular gene therapy delivery vectors, but their application can be limited by anti-vector immunity. Both preexisting neutralizing antibodies (NAbs) and post-administration NAbs can limit transgene expression and reduce the clinical utility of AAVs. The development of novel AAVs will advance our understanding of AAV immunity and may also have practical applications. In this study, we identified five novel AAV capsids from rhesus macaques. RhAAV4282 exhibited 91.4% capsid sequence similarity with AAV7 and showed similar tissue tropism with slightly diminished overall signal. Despite this sequence homology, RhAAV4282 and AAV7 showed limited cross-neutralization. We determined a cryo-EM structure of the RhAAV4282 capsid at 2.57Å resolution and identified a small segment within the hypervariable region IV, involving seven amino acids that formed a shortened external loop in RhAAV4282 compared with AAV7. We generated RhAAV4282 and AAV7 mutants that involved swaps of this region and showed that this region partially determined neutralization phenotype. We termed thisregion the hypervariable region IV neutralizing epitope (HRNE). Our data suggests that modification of the HRNE can lead to AAVs with altered neutralization profiles.

Neonatal SARS-CoV-2 mRNA Vaccination Efficacy Is Influenced by Maternal Antibodies.

Vaccination in pregnancy guards against infection. Maternal antibodies, however, can inhibit antibody production in neonates. We sought to determine the effects of maternal vaccination on neonatal immune response to a SARS-CoV-2 mRNA vaccine. We hypothesized that mRNA-lipid nanoparticles (LNP) vaccination allows for a de novo neonatal antibody response even in the presence of vertically transmitted maternal antibodies. Female mice were vaccinated with SARS-CoV-2 spike receptor binding domain (RBD) mRNA-LNPs. Mice were then bred, and 21-day-old pups were inoculated with the same mRNA-LNPs. Spike-specific IgG ELISAs were performed using mouse serum. A SARS-CoV-2 spike protein peptide library to perform peptide ELISAs characterized high affinity binding domains within the spike protein. Results were analyzed with one-way ANOVAs with Tukey's multiple comparisons tests. Compared to pups of unvaccinated dams, there were high levels of spike-specific IgG detected in the pups of vaccinated dams at 3 weeks of life (p < 0.0001). After neonatal vaccination, pups of unvaccinated dams had higher spike-specific serum IgG than pups of vaccinated dams at 12 weeks of life (p < 0.001). Antibody specificity to peptide moieties within spike RBD were similar when comparing a vaccinated dam to her pup at Week 3 of life, with different binding affinities observed in the pups by Week 15 of life. Pre-existing maternal antibodies may partially blunt the initial neonatal antibody response to mRNA-LNPs vaccination. This vaccine strategy, however, does not prohibit the subsequent development of a broad range of RBD antibody specificities that may be protective.