Flow Cytometry-Based Measurement of Antibodies Specific for Cell Surface-Expressed Folded SARS-CoV-2 Receptor-Binding Domains

BACKGROUND

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has now become endemic and is currently one of the important respiratory virus infections regularly affecting mankind. The assessment of immunity against SARS-CoV-2 and its variants is important for guiding active and passive immunization and SARS-CoV-2-specific treatment strategies.

METHODS

We here devised a novel flow cytometry-based diagnostic platform for the assessment of immunity against cell-bound virus antigens. This platform is based on a collection of HEK-293T cell lines which, as exemplified in our study, stably express the receptor-binding domains (RBDs) of the SARS-CoV-2 S-proteins of eight major SARS-CoV-2 variants, ranging from Wuhan-Hu-1 to Omicron.

RESULTS

RBD-expressing cell lines stably display comparable levels of RBD on the surface of HEK-293T cells, as shown with anti-FLAG-tag antibodies directed against a N-terminally introduced 3x-FLAG sequence while the functionality of RBD was proven by ACE2 binding. We exemplify the usefulness and specificity of the cell-based test by direct binding of IgG and IgA antibodies of SARS-CoV-2-exposed and/or vaccinated individuals in which the assay shows a wide linear performance range both at very low and very high serum antibody concentrations. In another application, i.e., antibody adsorption studies, the test proved to be a powerful tool for measuring the ratios of individual variant-specific antibodies.

CONCLUSION

We have established a toolbox for measuring SARS-CoV-2-specific immunity against cell-bound virus antigens, which may be considered as an important addition to the armamentarium of SARS-CoV-2-specific diagnostic tests, allowing flexible and quick adaptation to new variants of concern.

Immunogenicity and safety of COVID-19 booster vaccination: A population-based clinical trial to identify the best vaccination strategy

BACKGROUND

Various SARS-CoV-2 variants of concerns (VOCs) characterized by higher transmissibility and immune evasion have emerged. Despite reduced vaccine efficacy against VOCs, currently available vaccines provide protection. Population-based evidence on the humoral immune response after booster vaccination is crucial to guide future vaccination strategies and in preparation for imminent COVID-19 waves.

METHODS

This multicenter, population-based cohort study included 4697 individuals ≥18 years of age who received a booster vaccination. Antibody levels against SARS-CoV-2 receptor binding domain (RBD) and neutralizing antibodies against wild-type (WT) virus and Omicron variants were assessed at baseline (day of booster vaccination) and after four weeks. Safety was evaluated daily within the first week using a participant-completed electronic diary. Antibody levels were compared across different vaccination strategies, taking into account individual host factors.

RESULTS

Our main model including 3838 participants revealed that individuals who received a booster with mRNA-1273 compared to BNT162b2 vaccine had a significantly higher increase (95 %CI) in anti-RBD-antibody levels (37,707 BAU/mL [34,575-40,839] vs. 27,176 BAU/mL [26,265-28,087]), and of neutralization levels against WT (1,681 [1490-1872] vs. 1141 [1004-1278] and Omicron variant (422 [369-474] vs. 329 [284-374]). Neutralizing antibody titres highly correlated with anti-RBD antibodies, with neutralizing capacity 4.4 fold higher against WT compared to Omicron. No differences in safety were found between the two booster vaccines.

CONCLUSION

Our study underlines the superiority of a booster vaccination with mRNA-1273, independent of the primary vaccination and therefore provides guidance on the vaccination strategy.

Complete genome sequence of Bordetella parapertussis strain 400431-b, isolated from a protracted course of whooping cough in Austria, 2023

Here, we report the complete genome of Bordetella parapertussis strain 400431-b isolated from a nasopharyngeal swab from a 4-year-old patient presenting with a protracted course of whooping cough, vaccinated with three doses of diphtheria-tetanus-acellular pertussis-hepatitis B-poliomyelitis-Haemophilus influenzae type b vaccine.

Preclinical and Clinical Observations Implying Combination Therapy to Enhance the Efficacy of the Her-2/neu B-Cell Peptide-Based Vaccine HER-Vaxx and to Prevent Immune Evasion

Her-2/neu-targeting therapy by passive application with trastuzumab is associated with acquired resistance and subsequent metastasis development, which is attributed to the upregulation of tumoral PD-L1 expression and the downregulation of Her-2/neu. We aimed to investigate this association, following active immunization with our recently constructed B-cell peptide-based Her-2/neu vaccines in both preclinical and clinical settings. Immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and combined positive score (CPS) were applied to evaluate Her-2/neu and PD-L1 expression using a murine syngeneic tumor model for Her-2/neu lung metastases and tumor biopsies from a gastric cancer patient with disease progression. A significant and concomitant reduction in Her-2/neu and the upregulation of PD-L1 expression was observed in vaccinated mice after 45 days, but not after 30 days, of metastases development. A significant increase in tumor-infiltrating B lymphocytes was observed at both time points. The downregulation of Her-2/neu and the upregulation of PD-L1 were observed in a patient's primary tumor at the disease progression time point but not prior to vaccination (Her-2/neu IHC: 3 to 0, FISH: 4.98 to 1.63; PD-L1 CPS: 0% to 5%). Our results further underline the need for combination therapy by targeting PD-L1 to prevent metastasis formation and immune evasion of Her-2/neu-positive and PD-L1-negative tumor cells.

Natural human Bet v 1-specific IgG antibodies recognize non-conformational epitopes whereas IgE reacts with conformational epitopes

BACKGROUND

The nature of epitopes on Bet v 1 recognized by natural IgG antibodies of birch pollen allergic patients and birch pollen-exposed but non-sensitized subjects has not been studied in detail.

OBJECTIVE

To investigate IgE and IgG recognition of Bet v 1 and to study the effects of natural Bet v 1-specific IgG antibodies on IgE recognition of Bet v 1 and Bet v 1-induced basophil activation.

METHODS

Sera from birch pollen allergic patients (BPA, n = 76), allergic patients without birch pollen allergy (NBPA, n = 40) and non-allergic individuals (NA, n = 48) were tested for IgE, IgG as well as IgG1 and IgG4 reactivity to folded recombinant Bet v 1, two unfolded recombinant Bet v 1 fragments comprising the N-terminal (F1) and C-terminal half of Bet v 1 (F2) and unfolded peptides spanning the corresponding sequences of Bet v 1 and the apple allergen Mal d 1 by ELISA or micro-array analysis. The ability of Bet v 1-specific serum antibodies from non-allergic subjects to inhibit allergic patients IgE or IgG binding to rBet v 1 or to unfolded Bet v 1-derivatives was assessed by competition ELISAs. Furthermore, the ability of serum antibodies from allergic and non-allergic subjects to modulate Bet v 1-induced basophil activation was investigated using rat basophilic leukaemia cells expressing the human FcεRI which had been loaded with IgE from BPA patients.

RESULTS

IgE antibodies from BPA patients react almost exclusively with conformational epitopes whereas IgG, IgG1 and IgG4 antibodies from BPA, NBPA and NA subjects recognize mainly unfolded and sequential epitopes. IgG competition studies show that IgG specific for unfolded/sequential Bet v 1 epitopes is not inhibited by folded Bet v 1 and hence the latter seem to represent cryptic epitopes. IgG reactivity to Bet v 1 peptides did not correlate with IgG reactivity to the corresponding Mal d 1 peptides and therefore does not seem to be a result of primary sensitization to PR10 allergen-containing food. Natural Bet v 1-specific IgG antibodies inhibited IgE binding to Bet v 1 only poorly and could even enhance Bet v 1-specific basophil activation.

CONCLUSION

IgE and IgG antibodies from BPA patients and birch pollen-exposed non-sensitized subjects recognize different epitopes. These findings explain why natural allergen-specific IgG do not protect against allergic symptoms and suggest that allergen-specific IgE and IgG have different clonal origin.

Malaria in Austria : A retrospective analysis of malaria cases diagnosed at a reference center in 2010-2020

BACKGROUND

Although malaria is not endemic to Austria, each year infections are imported by travellers, migrants and refugees. This study aims to provide an overview of malaria cases diagnosed at an Austrian institute for tropical medicine between 2010 and 2020.

METHODS

A retrospective, descriptive study was conducted based on the data of malaria cases confirmed at the Institute of Specific Prophylaxis and Tropical Medicine of the Medical University of Vienna. Laboratory diagnostics included microscopy, polymerase chain reaction (PCR) and real-time quantitative PCR.

RESULTS

Overall, 122 cases were identified. Annual case numbers were consistently higher from 2016 to 2020 than during the first half of the decade. Most malaria cases were diagnosed during summer and early autumn. This seasonal trend was not observed during the year 2020. With 55.1% (65/118) Plasmodium falciparum was the most common species, followed by Plasmodium vivax (19.5%, 23/118). The majority of patients were male (71.1%, 86/121) and the median age was 34.5 years (interquartile range, IQR 22.5-47.0 years). With a median age of 20.0 years (IQR 14.0-32.0 years), patients with P. vivax infections were younger than those infected with other Plasmodium species. Moreover, they were mostly male (82.6%, 19/23).

CONCLUSION

From 2010 to 2020, the number of malaria cases diagnosed at the center increased. Growing international mobility and changing travel behavior could at least partly be responsible for this trend and there are indications that particularly P. vivax infections were imported by migrants and refugees.

Extracellular vesicles of the probiotic bacteria E. coli O83 activate innate immunity and prevent allergy in mice

BACKGROUND

E. coli O83 (Colinfant Newborn) is a Gram-negative (G-) probiotic bacterium used in the clinic. When administered orally, it reduces allergic sensitisation but not allergic asthma. Intranasal administration offers a non-invasive and convenient delivery method. This route bypasses the gastrointestinal tract and provides direct access to the airways, which are the target of asthma prevention. G- bacteria such as E. coli O83 release outer membrane vesicles (OMVs) to communicate with the environment. Here we investigate whether intranasally administered E. coli O83 OMVs (EcO83-OMVs) can reduce allergic airway inflammation in mice.

METHODS

EcO83-OMVs were isolated by ultracentrifugation and characterised their number, morphology (shape and size), composition (proteins and lipopolysaccharide; LPS), recognition by innate receptors (using transfected HEK293 cells) and immunomodulatory potential (in naïve splenocytes and bone marrow-derived dendritic cells; BMDCs). Their allergy-preventive effect was investigated in a mouse model of ovalbumin-induced allergic airway inflammation.

RESULTS

EcO83-OMVs are spherical nanoparticles with a size of about 110 nm. They contain LPS and protein cargo. We identified a total of 1120 proteins, 136 of which were enriched in OMVs compared to parent bacteria. Proteins from the flagellum dominated. OMVs activated the pattern recognition receptors TLR2/4/5 as well as NOD1 and NOD2. EcO83-OMVs induced the production of pro- and anti-inflammatory cytokines in splenocytes and BMDCs. Intranasal administration of EcO83-OMVs inhibited airway hyperresponsiveness, and decreased airway eosinophilia, Th2 cytokine production and mucus secretion.

CONCLUSIONS

We demonstrate for the first time that intranasally administered OMVs from probiotic G- bacteria have an anti-allergic effect. Our study highlights the advantages of OMVs as a safe platform for the prophylactic treatment of allergy. Video Abstract.

Lower magnitude and faster waning of antibody responses to SARS-CoV-2 vaccination in anti-TNF-α-treated IBD patients are linked to lack of activation and expansion of cTfh1 cells and impaired B memory cell formation

BACKGROUND

Patients with inflammatory bowel disease (IBD) and healthy controls received primary SARS-CoV-2-mRNA vaccination and a booster after six months. Anti-TNF-α-treated patients showed significantly lower antibody (Ab) levels and faster waning than α4β7-integrin-antagonist recipients and controls. This prospective cohort study aimed to elucidate the underlying mechanisms on the basis of circulating T-follicular helper cells (cTfh) and B memory cells.

METHODS

We measured SARS-CoV-2- Wuhan and Omicron specific Abs, B- and T-cell subsets at baseline and kinetics of Spike (S)-specific B memory cells along with distributions of activated cTfh subsets before and after primary and booster vaccination.

FINDINGS

Lower and faster waning of Ab levels in anti-TNF-α treated IBD patients was associated with low numbers of total and naïve B cells vs. expanded plasmablasts prior to vaccination. Along with their low Ab levels against Wuhan and Omicron VOCs, reduced S-specific B memory cells were identified after the 2nd dose which declined to non-detectable after 6 months. In contrast, IBD patients with α4β7-integrin-antagonists and controls mounted and retained high Ab levels after the 2nd dose, which was associated with a pronounced increase in S-specific B memory cells that were maintained or expanded up to 6 months. Booster vaccination led to a strong increase of Abs with neutralizing capacity and S-specific B memory cells in these groups, which was not the case in anti-TNF-α treated IBD patients. Of note, Ab levels and S-specific B memory cells in particular post-booster correlated with the activation of cTfh1 cells after primary vaccination.

INTERPRETATIONS

The reduced magnitude, persistence and neutralization capacity of SARS-CoV-2 specific Abs after vaccination in anti-TNF-α-treated IBD patients were associated with impaired formation and maintenance of S-specific B memory cells, likely due to absent cTfh1 activation leading to extra-follicular immune responses and diminished B memory cell diversification. These observations have implications for patient-tailored vaccination schedules/vaccines in anti-TNF-α-treated patients, irrespective of their underlying disease.

FUNDING

The study was funded by third party funding of the Institute of Specific Prophylaxis and Tropical Medicine at the Medical University Vienna. The funders had no role in study design, data collection, data analyses, interpretation, or writing of report.

Lack of seroprotection against diphtheria in the Austrian population, in light of reported diphtheria cases in Europe, 2022

Following an increase in diphtheria cases in Europe since 2022, we retrospectively estimated the prevalence of seroprotection against diphtheria and tetanus in 10,247 Austrian residents (population: 8,978,929) voluntarily tested between 2018 and 2022. Lack of seroprotection against diphtheria was found in 36% compared with 4% against tetanus. The geometric mean antibody concentration against tetanus was 7.9-fold higher compared with that for diphtheria. Raising awareness of regular booster vaccinations against diphtheria in combination with tetanus and pertussis is urgently needed.

Multiparametric Prediction Models for Coronavirus Disease 2019 Vaccine Selection: Results of a Comparative Population-Based Cohort Study

BACKGROUND

An understanding vaccine-dependent effects on protective and sustained humoral immune response is crucial to planning future vaccination strategies against coronavirus disease 2019 (COVID-19).

METHODS

In this multicenter, population-based, cohort study including 4601 individuals after primary vaccination against COVID-19 ≥ 4 months earlier we compared factors associated with residual antibody levels against severe acute respiratory syndrome coronavirus-2 receptor-binding domain (RBD) across different vaccination strategies (BNT162b2, mRNA-1273, or ChAdOx1).

RESULTS

Our main model including 3787 individuals (2 × BNT162b2, n = 2271; 2 × mRNA-1273, n = 251; 2 × ChAdOx1, n = 1265), predicted significantly lower levels of anti-RBD antibodies after 6 months in individuals vaccinated with ChAdOx1 (392.7 binding antibody units per milliliter [BAU/mL]) compared with those vaccinated with BNT162b2 (1179.5 BAU/mL) or mRNA-1273 (2098.2 BAU/mL). Vaccine-dependent association of antibody levels was found for age with a significant predicted difference in BAU/ml per year for BNT162b2 (-21.5; 95% confidence interval [CI], -24.7 to -18.3) and no significant association for mRNA-1273 (-4.0; 95% CI, -20.0 to 12.1) or ChAdOx1 (1.7; 95% CI, .2 to 3.1). The predicted decrease over time since full immunization was highest in mRNA-1273 (-23.4; 95% CI, -31.4 to -15.4) compared with BNT162b2 (-5.9; 95% CI, -7 to -4.8).

CONCLUSIONS

Our study revealed population-based evidence of vaccine-dependent effects of age and time since full immunization on humoral immune response. Findings underline the importance of individualized vaccine selection, especially in elderly individuals.

HERIZON: A phase 2 study of HER-Vaxx (IMU-131), a HER2-targeting peptide vaccine, plus standard of care chemotherapy in patients with HER2-overexpressing metastatic or advanced gastric/GEJ adenocarcinoma— Overall survival analysis

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Background: Active immunization with the B-lymphocyte stimulating HER2 vaccine, HER-Vaxx (IMU-131), has shown clinical response correlated with HER2-specific antibodies (Wiedermann et. al., Clinical Cancer Research, 2021). The HER-Vaxx HERIZON study is based on the landmark ToGA study (Bang et. al., The Lancet, 2010) and included patients with HER2/neu over-expressing metastatic or advanced gastric/GEJ adenocarcinoma who were naïve to HER2 therapy. Methods: Thirty-six patients were randomized to either HER-Vaxx plus standard chemotherapy or standard chemotherapy alone. The primary endpoint was overall survival (OS). HER-Vaxx plus chemotherapy treated patients received 50 µg dose of HER-Vaxx by intra-muscular injection at Days 0, 14, 35, 77 and every 63 days until disease progression. Both groups received chemotherapy starting at Day 0 and then every 21 days for a maximum of 6 cycles or until disease progression. Standard chemotherapy consisted of cisplatin + 5FU or capecitabine, or oxaliplatin + capecitabine. Statistical analysis pre-specified a 1-sided false positive probability of 0.10. Results: Of 36 patients randomized (19 treated with HER-Vaxx plus chemotherapy and 17 with chemotherapy alone), 32 patients had a survival event (15 and 17 respectively) at the time of final analysis. All patients received oxaliplatin + capecitabine chemotherapy. Analysis showed a 42% survival benefit for patients treated with HER-Vaxx plus chemotherapy compared to chemotherapy alone. This translated into an OS HR of 0.580 (80% 2-sided CI: 0.362, 0.927) with a statistically significant p-value of 0.066. The median OS for patients receiving HER-Vaxx plus chemotherapy was 13.9 (7.5, 14.3) months, compared to 8.3 (6.0, 9.6) months in patients treated with chemotherapy alone. Median duration of response was 30 vs 19 weeks in favor of the HER-Vaxx arm. There was no difference in safety between the two treatment arms, indicating HER-Vaxx does not add toxicity to standard chemotherapy. HER-Vaxx induced persistent HER2 specific antibodies which correlated with clinical response. Additional response parameters including DOR and biomarker data will be presented at the meeting. Conclusions: These data demonstrate that in patients with HER2 over-expressing gastric/GEJ cancer active HER2 immunization with HER-Vaxx is safe and provides relevant clinical benefit over standard of care chemotherapy. Clinical trial information: NCT02795988 .

A Biomimetic, Silaffin R5-Based Antigen Delivery Platform

Nature offers a wide range of evolutionary optimized materials that combine unique properties with intrinsic biocompatibility and that can be exploited as biomimetic materials. The R5 and RRIL peptides employed here are derived from silaffin proteins that play a crucial role in the biomineralization of marine diatom silica shells and are also able to form silica materials in vitro. Here, we demonstrate the application of biomimetic silica particles as a vaccine delivery and adjuvant platform by linking the precipitating peptides R5 and the RRIL motif to a variety of peptide antigens. The resulting antigen-loaded silica particles combine the advantages of biomaterial-based vaccines with the proven intracellular uptake of silica particles. These particles induce NETosis in human neutrophils as well as IL-6 and TNF-α secretion in murine bone marrow-derived dendritic cells.

Development of the B cell cancer vaccine HER-vaxx for the treatment of her-2 expressing cancers

Her-2/neu is a tumor-associated protein that is overexpressed in a number of malignancies, including advanced cancer of the stomach, and has been proposed as a human cancer vaccine target. Overexpression of Her-2/neu in human breast and gastric carcinomas correlates with a more aggressive course of disease that results in poorer overall survival rates and shorter times to disease progression than in patients with tumors without overexpression of Her-2/neu. Cancer vaccines have the ability to stimulate the native immune system and in particular engineered B cell epitopes can elicit high affinity polyclonal antibodies with similar efficacy to Her-2 monoclonal antibodies such as trastuzumab (Roche). HER-Vaxx is under development as a therapeutic B cell vaccine for the treatment of gastric cancer in patients with Her-2/neu overexpressing metastatic or advanced adenocarcinoma of the stomach or gastroesophageal junction, referred to as advanced cancer of the stomach. P467-CRM197, the vaccine's immunogenic component, contains a single peptide antigen composed of 3 individual linear B cell epitope peptide sequences selected from the oncoprotein Her-2/neu that induce the patient's own B cells to produce endogenous anti-Her-2/neu antibodies. This review provides results from comprehensive preclinical studies encompassing primary and secondary pharmacodynamics, biodistribution and safety studies. These studies were performed to support clinical development of HER-Vaxx. Results from the GLP toxicology study in rodents showed that the vaccine did not produce any observable adverse effects suggesting that the doses proposed for the clinical trial should be well tolerated in patients.

The Association of Time of Day of ChAdOx1 nCoV-19 Vaccine Administration With SARS-CoV-2 Anti-Spike IgG Antibody Levels: An Exploratory Observational Study

Data from human and animal studies are highly suggestive of an influence of time of day of vaccine administration on host immune responses. In this population-based study, we aimed to investigate the effect of time of day of administration of a COVID-19 vector vaccine, ChAdOx1 nCoV-19 (AstraZeneca), on SARS-CoV-2 anti-spike S1 immunoglobulin (IgG) levels. Participants were 803 university employees who received their first vaccine dose in March 2021, had serology data at baseline and at 3 weeks, and were seronegative at baseline. Antibody levels were determined in binding antibody units (BAU/mL) using enzyme-linked immunosorbent assay (ELISA). Generalized additive models (GAM) and linear regression were used to evaluate the association of time of day of vaccination continuously and in hourly bins with antibody levels at 3 weeks. Participants had a mean age of 42 years (SD: 12; range: 21-74) and 60% were female. Time of day of vaccination was associated non-linearly ("reverse J-shape") with antibody levels. Morning vaccination was associated with the highest (9:00-10:00 h: mean 292.1 BAU/mL; SD: 262.1), early afternoon vaccination with the lowest (12:00-13:00 h: mean 217.3 BAU/mL; SD: 153.6), and late afternoon vaccination with intermediate (14:00-15:00 h: mean 280.7 BAU/mL; SD: 262.4) antibody levels. Antibody levels induced by 12:00-13:00 h vaccination (but not other time intervals) were significantly lower compared to 9:00-10:00 h vaccination after adjusting for potential confounders (beta coefficient = -75.8, 95% confidence interval [CI] = -131.3, -20.4). Our findings show that time of day of vaccination against SARS-CoV-2 has an impact on the magnitude of IgG antibody levels at 3 weeks. Whether this difference persists after booster vaccine doses and whether it influences the level of protection against COVID-19 needs further evaluation.

Heterologous vector versus homologous mRNA COVID-19 booster vaccination in non-seroconverted immunosuppressed patients: a randomized controlled trial

Impaired response to COVID-19 vaccination is of particular concern in immunosuppressed patients. To determine the best vaccination strategy for this vulnerable group we performed a single center, 1:1 randomized blinded clinical trial. Patients who failed to seroconvert upon two mRNA vaccinations (BNT162b2 or mRNA-1273) are randomized to receive either a third dose of the same mRNA or the vector vaccine ChAdOx1 nCoV-19. Primary endpoint is the difference in SARS-CoV-2 spike antibody seroconversion rate between vector and mRNA vaccinated patients four weeks after the third dose. Secondary outcomes include cellular immune responses. Seroconversion rates at week four are significantly higher in the mRNA (homologous vaccination, 15/24, 63%) as compared to the vector vaccine group (heterologous vaccination, 4/22, 18%). SARS-CoV-2-specific T-cell responses are reduced but could be increased after a third dose of either vector or mRNA vaccine. In a multivariable logistic regression analysis, patient age and vaccine type are associated with seroconversion. No serious adverse event is attributed to COVID-19 booster vaccination. Efficacy and safety data underline the importance of a booster vaccination and support the use of a homologous mRNA booster vaccination in immunosuppressed patients.Trial registration: EudraCT No.: 2021-002693-10.

NKG2A-checkpoint inhibition and its blockade critically depends on peptides presented by its ligand HLA-E

NKG2A has emerged as a new immunotherapy target and its blockade with the novel immune checkpoint inhibitor (ICI) monalizumab can boost both NK cell and CD8+ T cell responses. NKG2A forms heterodimers with CD94 and binds to the human non-classical MHC class I molecule HLA-E. HLA-E forms complexes with a limited set of peptides mainly derived from the leader sequences of the classical MHC class I molecules (HLA-A, HLA-B and HLA-C) and the non-classical class I paralogue HLA-G, and it is well established that the interaction between CD94/NKG2x receptors and its ligand HLA-E is peptide-sensitive. Here, we have evaluated peptide dependence of NKG2A-mediated inhibition and the efficiency of interference by monalizumab in a transcriptional T cell reporter system. NKG2A inhibition was mediated by cell-expressed HLA-E molecules stably presenting disulfate-trapped peptide ligands. We show that different HLA-class I leader peptides mediate varying levels of inhibition. We have used NKG2A/NKG2C chimeric receptors to map the binding site of NKG2A and NKG2C blocking antibodies. Furthermore, we determined the functional EC50 values of blocking NKG2A antibodies and show that they greatly depend on the HLA-leader peptide presented by HLA-E. Monalizumab was less effective in augmenting NK cell-mediated killing of target cells displaying HLA-G peptide on HLA-E, than cells expressing HLA-E complexed with HLA-A, HLA-B and HLA-C peptides. Our results indicate that peptides displayed by HLA-E molecules on tumour cells might influence the effectivity of NKG2A-ICI therapy and potentially suggest novel approaches for patient stratification, for example, based on tumoral HLA-G levels.

Autochthonous Human Dirofilaria repens Infection in Austria

PURPOSE

This report describes a rare autochthonous case of human D. repens infection in Austria. Dirofilariosis is a mosquito-borne parasitic infection that predominantly affects dogs. Human D. repens infections have primarily been reported in Mediterranean countries, but are emerging throughout Central and Northern Europe.

METHODS

The worm was removed surgically and identified using PCR and DNA sequencing. The consensus sequences were compared against reference sequences of Dirofilaria repens from GenBank.

RESULTS

The 56-year-old woman acquired the infection, which presented as a subcutaneous nodule, in Vienna, Austria. This is the second autochthonous case of human D. repens infection in Austria.

CONCLUSION

The reasons for the emergence of D. repens and other parasitic infections in Central and Northern Europe are manifold, including climate change and globalization. This case demonstrates that with the growing number of D. repens infections, health care professionals must place further emphasis on emerging infectious diseases to ensure appropriate diagnostics and treatment in the future.

SARS-CoV-2-mRNA Booster Vaccination Reverses Non-Responsiveness and Early Antibody Waning in Immunocompromised Patients – A Phase Four Study Comparing Immune Responses in Patients With Solid Cancers, Multiple Myeloma and Inflammatory Bowel Disease

Background

Individuals with secondary immunodeficiencies belong to the most vulnerable groups to succumb to COVID-19 and thus are prioritized for SARS-CoV-2 vaccination. However, knowledge about the persistence and anamnestic responses following SARS-CoV-2-mRNA vaccinations is limited in these patients.

Methods

In a prospective, open-label, phase four trial we analyzed S1-specific IgG, neutralizing antibodies and cytokine responses in previously non-infected patients with cancer or autoimmune disease during primary mRNA vaccination and up to one month after booster.

Results

263 patients with solid tumors (SOT, n=63), multiple myeloma (MM, n=70), inflammatory bowel diseases (IBD, n=130) and 66 controls were analyzed. One month after the two-dose primary vaccination the highest non-responder rate was associated with lower CD19+ B-cell counts and was found in MM patients (17%). S1-specific IgG levels correlated with IL-2 and IFN-γ responses in controls and IBD patients, but not in cancer patients. Six months after the second dose, 18% of patients with MM, 10% with SOT and 4% with IBD became seronegative; no one from the control group became negative. However, in IBD patients treated with TNF-α inhibitors, antibody levels declined more rapidly than in controls. Overall, vaccination with mRNA-1273 led to higher antibody levels than with BNT162b2. Importantly, booster vaccination increased antibody levels >8-fold in seroresponders and induced anamnestic responses even in those with undetectable pre-booster antibody levels. Nevertheless, in IBD patients with TNF-α inhibitors even after booster vaccination, antibody levels were lower than in untreated IBD patients and controls.

Conclusion

Immunomonitoring of vaccine-specific antibody and cellular responses seems advisable to identify vaccination failures and consequently establishing personalized vaccination schedules, including shorter booster intervals, and helps to improve vaccine effectiveness in all patients with secondary immunodeficiencies.

Trial registration

EudraCT Number: 2021-000291-11

Course of Fecal Calprotectin after mRNA SARS-CoV-2 Vaccination in Patients with Inflammatory Bowel Diseases

Background: Two years into the pandemic, vaccination remains the most effective option to prevent coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Preliminary studies suggest vaccination efficacy in patients with inflammatory bowel diseases (IBD), but little is known about its impact on chronic intestinal inflammation. Here we assessed the mucosal inflammatory activity in patients with IBD before and after immunization with the mRNA-1273 (Moderna) vaccine by measurement of fecal calprotectin (fCP). Methods: In 42 patients with IBD, the baseline fCP levels obtained prior to the first vaccine were compared with the highest levels measured during and after two doses of vaccination. Patients’ sera were collected after the second dose to evaluate anti-SARS-CoV-2 antibodies’ titers. Results: We observed a significant fCP elevation in 31% of patients after any dose. Vedolizumab was identified as the only agent associated with an fCP increase (OR 12.4, 95% CI [1.6; 120.2], p = 0.0171). Gastrointestinal adverse events were reported in 9.5% of all subjects and in 75% of cases accompanied by an fCP increase. Anti-SARS-CoV-2 antibodies associated only weakly with the fCP increase after the first dose (p = 0.04). Conclusions: Our findings support possible collinearity in pathways of SARS-CoV-2 antigen expression and the pathogenesis of IBD.

Active immunization with a Her-2/neu-targeting Multi-peptide B cell vaccine prevents lung metastases formation from Her-2/neu breast cancer in a mouse model

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Trastuzumab and Pertuzumab extend the overall survival of breast cancer patients.

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Unlike monoclonal antibodies B cell peptides induce immunological memory.

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A multi-peptide B cell-based vaccination prevents Her-2/neu lung metastasis in mice.

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The vaccination results in Her-2/neu-negative tumors, with increased PD-L1 expression.

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A combination/alternating therapy for a total remission of metastases is suggested.

In pre-clinical and clinical settings, active immunization with a Her-2/neu vaccine (HerVaxx), comprising B-cell peptide from Trastuzumab binding site, has been shown to reduce primary tumor growth via induction of polyclonal anti-tumor immune responses and immunological memory. Here, we tested the combination of HerVaxx and the recently identified B-cell epitope/mimotope of Pertuzumab, i.e. a multi-peptide B-cell vaccine, for preventing Her-2/neu lung metastases formation in a mouse model. Active immunization with the multi-peptide vaccine was associated with decreased lung weights, and histological evaluation of the lungs showed that the significant reduction of lung metastases was associated with increased CD4⁺ and CD8⁺ T cell infiltration. Notably, along with the overall reduction of lungs weights and Her-2 positive metastases, a formation of Her-2/neu-negative tumors but with increased PD-L1 expression was observed. Our results might pave the way to a multi-peptide B-cell Her-2/neu vaccine serving as a secondary intervention in adjuvant settings to prevent tumor recurrence and spread. Moreover, combination therapy targeting PD-L1 may result in total remission of metastases. Such a therapy may be used clinically to alternately target Her-2/neu and PD-L1 in metastatic breast cancer.

Vaccine based on folded RBD-PreS fusion protein with potential to induce sterilizing immunity to SARS-CoV-2 variants

Background

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is responsible for the ongoing global COVID‐19 pandemic. One possibility to control the pandemic is to induce sterilizing immunity through the induction and maintenance of neutralizing antibodies preventing SARS‐CoV‐2 from entering human cells to replicate in.

Methods

We report the construction and in vitro and in vivo characterization of a SARS‐CoV‐2 subunit vaccine (PreS‐RBD) based on a structurally folded recombinant fusion protein consisting of two SARS‐CoV‐2 Spike protein receptor‐binding domains (RBD) fused to the N‐ and C‐terminus of hepatitis B virus (HBV) surface antigen PreS to enable the two unrelated proteins serving as immunologic carriers for each other.

Results

PreS‐RBD, but not RBD alone, induced a robust and uniform RBD‐specific IgG response in rabbits. Currently available genetic SARS‐CoV‐2 vaccines induce mainly transient IgG₁ responses in vaccinated subjects whereas the PreS‐RBD vaccine induced RBD‐specific IgG antibodies consisting of an early IgG₁ and sustained IgG₄ antibody response in a SARS‐CoV‐2 naive subject. PreS‐RBD‐specific IgG antibodies were detected in serum and mucosal secretions, reacted with SARS‐CoV‐2 variants, including the omicron variant of concern and the HBV receptor‐binding sites on PreS of currently known HBV genotypes. PreS‐RBD‐specific antibodies of the immunized subject more potently inhibited the interaction of RBD with its human receptor ACE2 and their virus‐neutralizing titers (VNTs) were higher than median VNTs in a random sample of healthy subjects fully immunized with registered SARS‐CoV‐2 vaccines or in COVID‐19 convalescent subjects.

Conclusion

The PreS‐RBD vaccine has the potential to serve as a combination vaccine for inducing sterilizing immunity against SARS‐CoV‐2 and HBV by stopping viral replication through the inhibition of cellular virus entry.

SARS-CoV-2-Specific Antibody (Ab) Levels and the Kinetic of Ab Decline Determine Ab Persistence Over 1 Year

In a SARS-CoV-2 seroprevalence study conducted with 1,655 working adults in spring of 2020, 12 of the subjects presented with positive neutralization test (NT) titers (>1:10). They were here followed up for 1 year to assess their Ab persistence. We report that 7/12 individuals (58%) had NT_50 titers ≥1:50 and S1-specific IgG ≥50 BAU/ml 1 year after mild COVID-19 infection. S1-specific IgG were retained until a year when these levels were at least >60 BAU/ml at 3 months post-infection. For both the initial fast and subsequent slow decline phase of Abs, we observed a significant correlation between NT_50 titers and S1-specific IgG and thus propose S1-IgG of 60 BAU/ml 3 months post-infection as a potential threshold to predict neutralizing Ab persistence for 1 year. NT_50 titers and S1-specific IgG also correlated with circulating S1-specific memory B-cells. SARS-CoV-2-specific Ab levels after primary mRNA vaccination in healthy controls were higher (Geometric Mean Concentration [GMC] 3158 BAU/ml [CI 2592 to 3848]) than after mild COVID-19 infection (GMC 82 BAU/ml [CI 48 to 139]), but showed a stronger fold-decline within 5–6 months (0.20–fold, to GMC 619 BAU/ml [CI 479 to 801] vs. 0.56–fold, to GMC 46 BAU/ml [CI 26 to 82]). Of particular interest, the decline of both infection- and vaccine-induced Abs correlated with body mass index. Our data contribute to describe decline and persistence of SARS-CoV-2-specific Abs after infection and vaccination, yet the relevance of the maintained Ab levels for protection against infection and/or disease depends on the so far undefined correlate of protection.

Vaccination against Her-2/neu, with focus on peptide-based vaccines

Immunotherapy has been a milestone in combatting cancer, by complementing or even replacing classic treatments like surgery, chemotherapy, radiation, and anti-hormonal therapy. In 15%-30% of breast cancers, overexpression of the human epidermal growth factor receptor 2 (Her-2/neu) is associated with more aggressive tumor development. Passive immunization/immunotherapy with the recombinantly produced Her-2/neu-targeting monoclonal antibodies (mAbs) pertuzumab and trastuzumab has been shown to effectively treat breast cancer and lead to a significantly better prognosis. However, allergic and hypersensitivity reactions, cardiotoxicity, development of resistance, lack of immunological memory which results in continuous application over a long period, and cost-intensiveness are among the drawbacks associated with this treatment. Furthermore, intrinsic or acquired resistance is associated with the application of therapeutic mAbs, leading to the disease recurrence. Conversely, these drawbacks could be potentially overcome by vaccination, i.e. an active immunization/immunotherapy approach by activating the patient’s own immune system to target cancer, along with inducing immunological memory. This review aims to summarize the main approaches investigated and undertaken for the production of Her-2/neu vaccine candidates, with the main focus on peptide-based vaccines and their evaluation in clinical settings.

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Her-2/neu is overexpressed in 10%-30% of breast and gastric cancer patients and this correlates with poor clinical outcomes.

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Passive application of trastuzumab and pertuzumab has outstandingly improved the Her-2/neu-related clinical outcomes.

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Treatment with mAbs is associated with frequent administration, cost-intensiveness, and resistance.

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Vaccination against Her-2/neu with e.g. mimotope- or peptide-based vaccines can alternatively overcome the mAbs’ drawbacks.

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Such alternatives may pave the way to therapeutics which could be used as monotherapy or in combination therapies with mAbs.

Absent antibody production following COVID19 vaccination with mRNA in patients under immunosuppressive treatments

Patients undergoing immunosuppressive treatments have a higher need for protection against coronavirus disease (COVID19) that follows infection with the SARS-CoV-2 virus but their ability to respond sufficiently to COVID vaccines is uncertain.

We retrospectively evaluated SARS-CoV-2 spike subunit 1 (S1)-specific antibody levels after two mRNA doses in 242 patients with underlying chronic inflammatory, hematooncological or metabolic diseases and in solid organ transplant recipients. S1-specific antibodies were measured 30 days after the second dose.

In 15.9% of these patients, no S1-specific antibodies were detectable. Non-responsiveness was linked to administration of B-cell depleting therapies as well as to ongoing therapies that block lymphocyte trafficking (Fingolimod) or inhibit T cell proliferation (Tacrolimus).

Thus, it is important to inform immunosuppressed patients about the risk of vaccine non-responsiveness and the necessity to maintain non-pharmaceutical protection measures. In these risk patients antibody testing and cellular analysis are helpful to estimate the benefit/responsiveness to further booster vaccinations.

Answers to burning questions for clinical allergologists related to the new COVID-19 vaccines

Background

Along with the newly approved vaccines against coronavirus disease 2019 (COVID-19), first reports of allergic or intolerance reactions were published. Subsequently, questions arose whether these vaccines pose an increased risk for intolerance reactions and whether allergic patients may be at higher risk for this.

Results

Allergic reactions following COVID-19 vaccinations have been reported, but mostly of mild severity and at normal (Moderna®) or only slightly increased frequency (BioNTech/Pfizer®) compared to established conventional vaccines. The risk of allergic reaction to the newly licensed vector vaccines (AstraZeneca®, Johnson&Johnson®) cannot be conclusively assessed yet, but also appears to be low. There is currently no evidence that patients with allergic diseases (atopic patients) react more frequently or more severely to these vaccines. It is currently assumed that intolerance reactions of the immediate-type are either type I allergic (IgE-mediated) reactions or occur via complement activation (CARPA, “complement activation-related pseudoallergy”). Polyethylene glycol (PEG) or polysorbate, which are present as stabilizers in the vaccines, are suspected as triggers for this.

Conclusion

The data available so far do not show a significantly increased risk of immediate-type allergic reactions in atopic persons. In almost all cases, atopic patients can be vaccinated without problems. Standardized follow-up tests after suspected allergic reactions or CARPA-mediated reactions are currently limited.

Isolate-Based Surveillance of Bordetella pertussis, Austria, 2018-2020

Pertussis is a vaccine-preventable disease, and its recent resurgence might be attributable to the emergence of strains that differ genetically from the vaccine strain. We describe a novel pertussis isolate-based surveillance system and a core genome multilocus sequence typing scheme to assess Bordetella pertussis genetic variability and investigate the increased incidence of pertussis in Austria. During 2018–2020, we obtained 123 B. pertussis isolates and typed them with the new scheme (2,983 targets and preliminary cluster threshold of <6 alleles). B. pertussis isolates in Austria differed genetically from the vaccine strain, both in their core genomes and in their vaccine antigen genes; 31.7% of the isolates were pertactin-deficient. We detected 8 clusters, 1 of them with pertactin-deficient isolates and possibly part of a local outbreak. National expansion of the isolate-based surveillance system is needed to implement pertussis-control strategies.

Abstract CT107: A PHASE 1B/2 OPEN-LABEL STUDY WITH RANDOMIZATION IN PHASE 2 OF IMU-131 HER2/NEU PEPTIDE VACCINE PLUS STANDARD OF CARE CHEMOTHERAPY IN PATIENTS WITH HER2/NEU OVEREXPRESSING METASTATIC OR ADVANCED ADENOCARCINOMA OF THE STOMACH OR GASTROESOPHAGEAL JUNCTION

Background: HER2/neu is overexpressed in up to 30% of gastroesophageal adenocarcinoma (GEA) patients and associated with poor prognosis. Recombinant mAbs to treat HER2/neu-amplified malignancies are effective with limitations so alternatives are needed. Therefore, we developed a B-cell epitope immunotherapy vaccine (IMU-131/HER-Vaxx) consisting of 3 fused B-cell epitopes (P467) from the HER2/neu extracellular domain coupled to CRM197 and adjuvanted with Montanide. This open-label multicenter Phase 1b study aimed to evaluate the optimal/safe IMU-131 dose leading to immunogenicity and clinical responses.Patients & Methods: Fourteen patients with HER2/neu overexpressing GEA were enrolled and dose escalation with 10, 30, and 50µg was performed in 3 cohorts. Immunogenicity was evaluated by P467- and HER2-specific Ab levels and cellular responses, and clinical response rates by CT/MRI scan evaluated according to RECISTv1.1. Results: IMU-131 was safe with no vaccine-related significant local or systemic reactions or SAEs. 11/14 patients were evaluable for changes in tumor size and vaccine-specific immune responses. One patient showed complete response, 5 showed partial response and 4 stable disease as their best response. HER2-specific IgG levels were dose-dependent. While in cohort 1 and 2 only 1/3 and 2/5 patients respectively responded with moderate to high Ab titers, all patients in cohort 3 mounted moderate to high HER2-specific IgGs. Additionally, cellular vaccine responses were induced, e. g. Th1-biased cytokine ratios and reduction of Tregs. The clinical response (progression free survival) was significantly prolonged in cohort 3 and showed a clear association with the magnitude of humoral and cellular vaccine responses. Conclusions: IMU-131 was well tolerated and safe. The vaccine-induced HER2-specific Abs and cellular responses were dose-dependent and correlated with clinical responses. The highest dose (50 µg) was recommended for further evaluation in a Phase II trial with two arms, chemotherapy with IMU-131 vaccine or chemotherapy alone, which is currently ongoing. https://clinicaltrials.gov/ct2/show/NCT02795988

Citation Format: Marina Maglakelidze, Dinara Ryspayeva, Iurie Bulat, Zoran Andric, Ivan Nikolic, Tanuj Chawla, Rajnish Nagarkar, Vaibhav Chourdhary, Giri Venkata, Rajesh Kumar Singh, Davorin Radosavljevic, Zoran Petrovic, Ursula Wiedermann, Leslie Chong, Nicholas J. Ede, Rita Laeufle, Anthony Good. A PHASE 1B/2 OPEN-LABEL STUDY WITH RANDOMIZATION IN PHASE 2 OF IMU-131 HER2/NEU PEPTIDE VACCINE PLUS STANDARD OF CARE CHEMOTHERAPY IN PATIENTS WITH HER2/NEU OVEREXPRESSING METASTATIC OR ADVANCED ADENOCARCINOMA OF THE STOMACH OR GASTROESOPHAGEAL JUNCTION [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT107.

Immunologically relevant aspects of the new COVID-19 vaccines-an ÖGAI (Austrian Society for Allergology and Immunology) and AeDA (German Society for Applied Allergology) position paper

BACKGROUND

The vaccines against the coronavirus disease 2019 (COVID-19) approved in the European Union represent a decisive step in the fight against the pandemic. The application of these available vaccines to patients with pre-existing immunological conditions leads to a multitude of questions regarding efficacy, side effects and the necessary patient information.

RESULTS

This review article provides insight into mechanisms of action of the currently available severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines and summarises the current state of science as well as expert recommendations regarding tolerability of the vaccines. In addition, the potential to develop protective immune responses is determined. A special focus is given on patients under immunosuppression or in treatment with immunomodulatory drugs. Special groups of the population such as children, pregnant women and the elderly are also considered.

CONCLUSION

Despite the need for a patient-specific risk-benefit assessment, the consensus among experts is that patients with immunological diseases in particular benefit from the induced immune protection after COVID-19 vaccination and do not have an increased risk of side effects.

HERIZON: A phase 1B/2 open-label study of imu-131 HER2/neu peptide vaccine PLUS standard of care chemotherapy with randomization in phase 2 in patients with HER2/neu overexpressing metastatic or advanced adenocarcinoma of the stomach or gastroesophageal junction

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Background: The phase 2 part of the study hypothesizes HER-Vaxx (IMU-131) will provide treatment benefits consistent with traditional monoclonal antibodies that target HER2 in patients with confirmed Her2+ advanced or metastatic gastric cancer with a corresponding adaptive immune response without added toxicity. In the phase 1b dose finding part of the study tumor response of patients who received 50ug dose strongly correlated with antibody levels with 50ug selected as the phase 2 dose (Wiedermann et. al., 2019). Phase 2 is a randomized two arm study of either HER-Vaxx plus standard chemotherapy or standard chemotherapy alone. The primary endpoint is overall survival, with progression-free survival, safety and immune related changes in humoral and cellular immunogenicity secondary endpoints. Methods: Patients received SOC chemotherapy for a maximum of 6 cycles with the HER-Vaxx group also receiving 50ug dose of IMU-131 at Baseline/Day 0, Day 14, Day 35, Day 77 and then every 63 days until disease progression. The per protocol pre-planned first interim analysis (OS, PFS and safety) in a total of 27 patients after 15 progression events was reviewed by the independent data monitoring committee (IDMC). Results: Within ITT analysis, 8 of 27 patients died on the control arm and 4 on the HER-Vaxx plus SOC chemotherapy arm with an overall survival HR of 0.418 (2 sided 80% CI: 0.186, 0.942) and a 1-sided p-value of 0.083. Out of 27 patients, 9 patients progressed on the control arm while 6 patients progressed on the HER-Vaxx plus SOC chemotherapy arm with a HR of 0.532 (2 sided 80% CI: 0.267, 1.060) and a 1-sided p-value of 0.086. A robust HER2 specific antibody response developed in the HER-Vaxx arm compared to the control arm whereas there was no difference in safety between the two treatment arms. Conclusions: The IDMC confirmed that the safety of the study was favorable with no added toxicity of HER-Vaxx and SOC chemotherapy with a favorable risk-benefit for the combination. The study has completed enrollment and final data is expected in late 2021. Clinical trial information: NCT02795988.

Circulation of pertussis and poor protection against diphtheria among middle-aged adults in 18 European countries

Reported incidence of pertussis in the European Union (EU) and the European Economic Area (EEA) varies and may not reflect the real situation, while vaccine-induced protection against diphtheria and tetanus seems sufficient. We aimed to determine the seroprevalence of DTP antibodies in EU/EEA countries within the age groups of 40-49 and 50-59 years. Eighteen countries collected around 500 samples between 2015 and 2018 (N = 10,302) which were analysed for IgG-DTP specific antibodies. The proportion of sera with pertussis toxin antibody levels ≥100 IU/mL, indicative of recent exposure to pertussis was comparable for 13/18 countries, ranging between 2.7-5.8%. For diphtheria the proportion of sera lacking the protective level (<0.1 IU/mL) varied between 22.8-82.0%. For tetanus the protection was sufficient. Here, we report that the seroprevalence of pertussis in these age groups indicates circulation of B. pertussis across EU/EEA while the lack of vaccine-induced seroprotection against diphtheria is of concern and deserves further attention.

Targeted COVID-19 Vaccination (TAV-COVID) Considering Limited Vaccination Capacities-An Agent-Based Modeling Evaluation

(1) Background: The Austrian supply of COVID-19 vaccine is limited for now. We aim to provide evidence-based guidance to the authorities in order to minimize COVID-19-related hospitalizations and deaths in Austria. (2) Methods: We used a dynamic agent-based population model to compare different vaccination strategies targeted to the elderly (65 ≥ years), middle aged (45-64 years), younger (15-44 years), vulnerable (risk of severe disease due to comorbidities), and healthcare workers (HCW). First, outcomes were optimized for an initially available vaccine batch for 200,000 individuals. Second, stepwise optimization was performed deriving a prioritization sequence for 2.45 million individuals, maximizing the reduction in total hospitalizations and deaths compared to no vaccination. We considered sterilizing and non-sterilizing immunity, assuming a 70% effectiveness. (3) Results: Maximum reduction of hospitalizations and deaths was achieved by starting vaccination with the elderly and vulnerable followed by middle-aged, HCW, and younger individuals. Optimizations for vaccinating 2.45 million individuals yielded the same prioritization and avoided approximately one third of deaths and hospitalizations. Starting vaccination with HCW leads to slightly smaller reductions but maximizes occupational safety. (4) Conclusion: To minimize COVID-19-related hospitalizations and deaths, our study shows that elderly and vulnerable persons should be prioritized for vaccination until further vaccines are available.

Clinical and Immunologic Responses to a B-Cell Epitope Vaccine in Patients with HER2/neu-Overexpressing Advanced Gastric Cancer-Results from Phase Ib Trial IMU.ACS.001

PURPOSE

HER2/neu is overexpressed in up to 30% of gastroesophageal adenocarcinomas (GEA) and linked to poor prognosis. Recombinant mAbs to treat HER2/neu-overexpressing cancers are effective with limitations, including resistance and toxicity. Therefore, we developed a therapeutic B-cell epitope vaccine (IMU-131/HER-Vaxx) consisting of three fused B-cell epitopes from the HER2/neu extracellular domain coupled to CRM197 and adjuvanted with Montanide. This phase Ib study aimed to evaluate the optimal/safe dose leading to immunogenicity and clinical responses (https//clinicaltrials.gov/ct2/show/NCT02795988).

PATIENTS AND METHODS

A total of 14 patients with HER2/neu-overexpressing GEA were enrolled, and dose escalation (10, 30, 50 μg) was performed in three cohorts (C). Immunogenicity was evaluated by HER2-specific Abs and cellular responses, clinical responses by CT scans according to RECIST version 1.1.

RESULTS

IMU-131 was safe without vaccine-related significant local/systemic reactions or serious adverse events. A total of 11 of 14 patients were evaluable for changes in tumor size and vaccine-specific immune responses. One patient showed complete, 5 partial responses, and 4 stable diseases as their best response. HER2-specific IgG levels were dose dependent. In contrast to patients in C1 and C2, all patients in C3 mounted substantial HER2-specific Ab levels. In addition, cellular vaccine responses, such as Th1-biased cytokine ratios and reduced regulatory T cell numbers, were generated. Progression-free survival was prolonged in C3, correlating with the vaccine-specific humoral and cellular responses.

CONCLUSIONS

IMU-131 was well tolerated and safe. The induced HER2-specific Abs and cellular responses were dose dependent and correlated with clinical responses. The highest dose (50 μg) was recommended for further evaluation in a phase II trial, with chemotherapy + IMU-131 or chemotherapy alone, which is currently ongoing.

Reduction of Allergic Lung Disease by Mucosal Application of Toxoplasma gondii-Derived Molecules: Possible Role of Carbohydrates

Background

The hygiene hypothesis suggests a link between parasitic infections and immune disorders, such as allergic diseases. We previously showed that infection with Toxoplasma gondii or systemic application of T. gondii tachyzoites lysate antigen (TLA) in a prophylactic, but not therapeutic protocol, prevented allergic airway inflammation in mice. Here we tested the effect of prophylactic and therapeutic application of TLA via the mucosal route.

Methods

Mice were intranasally treated with TLA either i) prior to sensitization, ii) during sensitization and challenge, or iii) after sensitization with ovalbumin (OVA). Recruitment of inflammatory cells to the lung, cytokine levels in restimulated lung and spleen cell cultures as well as levels of OVA-specific antibodies in serum were measured. In parallel, the effect of native TLA, heat-inactivated (hiTLA) or deglycosylated TLA (dgTLA) on sensitized splenocytes was evaluated ex vivo.

Results

When applied together with OVA i) during systemic sensitization and local challenge or ii) exclusively during local challenge, TLA reduced infiltration of eosinophils into the lung, OVA-specific type 2 cytokines in restimulated lung cell cultures, and partially, type 2 cytokines in restimulated spleen cell cultures in comparison to allergic controls. No beneficial effect was observed when TLA was applied prior to the start of sensitization. Analysis of epitope sugars on TLA indicated a high abundance of mannose, fucose, N-acetylglucosamine, and N-acetylgalactosamine. Deglycosylation of TLA, but not heat-inactivation, abolished the potential of TLA to reduce type 2 responses ex vivo, suggesting a significant role of carbohydrates in immunomodulation.

Conclusion

We showed that mucosal application of TLA reduced the development of experimental allergy in mice. The beneficial effects depended on the timing of the application in relation to the time point of sensitization. Not only co-application, but also therapy in sensitized/allergic animals with native TLA reduced local allergic responses. Furthermore, we show that TLA is highly glycosylated and glycoconjugates seem to play a role in anti-allergic effects. In summary, given the powerful modulatory effect that TLA exhibits, understanding its exact mechanisms of action may lead to the development of novel immunomodulators in clinical application.

Pre- and Neonatal Imprinting on Immunological Homeostasis and Epithelial Barrier Integrity by Escherichia coli Nissle 1917 Prevents Allergic Poly-Sensitization in Mice

A steady rise in the number of poly-sensitized patients has increased the demand for effective prophylactic strategies against multi-sensitivities. Probiotic bacteria have been successfully used in clinics and experimental models to prevent allergic mono-sensitization. In the present study, we have investigated whether probiotic bacteria could prevent poly-sensitization by imprinting on the immune system early in life. We used two recombinant variants of probiotic Escherichia coli Nissle 1917 (EcN): i) EcN expressing birch and grass pollen, poly-allergen chimera construct (EcN-Chim), and ii) an “empty” EcN without allergen expression (EcN-Ctrl). Conventional mice (CV) were treated with either EcN-Chim or EcN-Ctrl in the last week of the gestation and lactation period. Gnotobiotic mice received one oral dose of either EcN-Chim or EcN-Ctrl before mating. The offspring from both models underwent systemic allergic poly-sensitization and intranasal challenge with recombinant birch and grass pollen allergens (rBet v 1, rPhl p 1, and rPhl p 5). In the CV setting, the colonization of offspring via treatment of mothers reduced allergic airway inflammation (AAI) in offspring compared to poly-sensitized controls. Similarly, in a gnotobiotic model, AAI was reduced in EcN-Chim and EcN-Ctrl mono-colonized offspring. However, allergy prevention was more pronounced in the EcN-Ctrl mono-colonized offspring as compared to EcN-Chim. Mono-colonization with EcN-Ctrl was associated with a shift toward mixed Th1/Treg immune responses, increased expression of TLR2 and TLR4 in the lung, and maintained levels of zonulin-1 in lung epithelial cells as compared to GF poly-sensitized and EcN-Chim mono-colonized mice. This study is the first one to establish the model of allergic poly-sensitization in gnotobiotic mice. Using two different settings, gnotobiotic and conventional mice, we demonstrated that an early life intervention with the EcN without expressing an allergen is a powerful strategy to prevent poly-sensitization later in life.

Cross-Reactive Effects of Vaccines: Heterologous Immunity between Tetanus and Chlamydia

Vaccines can have heterologous effects on the immune system, i.e., effects other than triggering an immune response against the disease targeted by the vaccine. We investigated whether monoclonal antibodies (mAbs) specific for tetanus could cross-react with Chlamydia and confer heterologous protection against chlamydial infection. The capability of two tetanus-specific mAbs, namely mAb26 and mAb51, to prevent chlamydial infection has been assessed: (i) in vitro, by performing a neutralization assay using human conjunctival epithelial (HCjE) cells infected with Chlamydia trachomatis serovar B, and (ii) in vivo, by using a guinea pig model of Chlamydiacaviae-induced inclusion conjunctivitis. The mAb26 has been superior in comparison with mAb51 in the prevention of chlamydial infection in HCjE cells. The mAb26 has conferred ≈40% inhibition of the infection, compared to less than 5% inhibition in the presence of the mAb51. In vivo, mAb26 significantly diminished ocular pathology intensity in guinea pigs infected with C. caviae compared to either the mAb51-treated or sham-treated guinea pigs. Our data provide insights that tetanus immunization generates antibodies which induce heterologous chlamydial immunity and promote protection beyond the intended target pathogen.

Abstract 3151: Active immunization with PD1-derived mimotope-Combination immunotherapy against Her-2/neu-expressing tumors

Application of monoclonal antibodies (mAbs) as immune checkpoint inhibitors (ICIs) has demonstrated a tremendous effect in cancer immunotherapy. However, high costs for and frequent applications of mono- or combination-therapies or possible development of resistance justify modifications of this approach. In this line, active immunization with mimotopes (B cell peptides) of ICIs, activating the patients' own immune system, rather than application of the corresponding therapeutic mAbs, may provide advantages over the costly treatment of the mAbs. Overlapping peptides spanning the extracellular domains of human PD1 (hPD1) were used to identify hPD1-derived mimotope, using the therapeutic mAb Nivolumab as a proof of concept. Additionally, for in vivo evaluation in a tumor mouse model, a mouse PD1 (mPD1)-derived mimotope was identified using an anti-mPD1 mAb with mPD1/mPDL-1 blocking capacity. The identified mimotopes were characterized by in vitro assays, including a reporter cell-based assay, and their anti-tumor effect was evaluated in a syngeneic mouse model involving grafting with human Her-2/neu-expressing tumors. The PD1-mimotopes were shown to specifically inhibit the binding of the corresponding mAbs, and also the mAbs capacity in blocking the respective PD1-PDL1 interactions. Applying the syngeneic tumor mouse model, a significant tumor growth reduction following active immunization with the mPD1-mimotope was shown. Importantly, combined vaccination with the mimotope and a multiple B-cell epitope Her-2/neu vaccine potentiated the anti-tumor effect in the syngeneic mice. Tumor growth reduction in the mice immunized with the mimotope was associated with a significant increase of the apoptotic (CC3) and significant reduction of proliferation (Ki67) markers, as evaluated by immunohistochemistry (IHC) staining. However, the tumor growth reduction following active immunization with the cancer vaccine (alone or in combination with the checkpoint mimotope) showed a different IHC picture, namely highly increased levels of CC3 without reduction of proliferation (Ki67 levels) in the tumor cells. In depth studies on the underlying mechanisms of tumor growth reduction are currently ongoing. Our results suggest active immunization with B cell mimotopes of ICIs as either monovalent vaccine or a combination therapy with tumor specific vaccines to enhance the anti-tumor efficacy. Such strategies may potentially lead to multipurpose treatment regimens adapted to the type, stage and progression phase of the various tumors.

Citation Format: Joshua Tobias, Claire Battin, Annika De Sousa Linhares, Michael Lebens, Karin Baier, Katharina Ambroz, Mirjana Drinić, Sandra Högler, Aleksandra Inic-Kanada, Erika Garner-Spitzer, Matthias Preusser, Lukas Kenner, Michael Kundi, Christoph C. Zielinski, Peter Steinberger, Ursula Wiedermann. Active immunization with PD1-derived mimotope-Combination immunotherapy against Her-2/neu-expressing tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3151.

Machine Learning-Empowered FTIR Spectroscopy Serum Analysis Stratifies Healthy, Allergic, and SIT-Treated Mice and Humans

The unabated global increase of allergic patients leads to an unmet need for rapid and inexpensive tools for the diagnosis of allergies and for monitoring the outcome of allergen-specific immunotherapy (SIT). In this proof-of-concept study, we investigated the potential of Fourier-Transform Infrared (FTIR) spectroscopy, a high-resolution and cost-efficient biophotonic method with high throughput capacities, to detect characteristic alterations in serum samples of healthy, allergic, and SIT-treated mice and humans. To this end, we used experimental models of ovalbumin (OVA)-induced allergic airway inflammation and allergen-specific tolerance induction in BALB/c mice. Serum collected before and at the end of the experiment was subjected to FTIR spectroscopy. As shown by our study, FTIR spectroscopy, combined with deep learning, can discriminate serum from healthy, allergic, and tolerized mice, which correlated with immunological data. Furthermore, to test the suitability of this biophotonic method for clinical diagnostics, serum samples from human patients were analyzed by FTIR spectroscopy. In line with the results from the mouse models, machine learning-assisted FTIR spectroscopy allowed to discriminate sera obtained from healthy, allergic, and SIT-treated humans, thereby demonstrating its potential for rapid diagnosis of allergy and clinical therapeutic monitoring of allergic patients.

A novel 5-Plex qPCR-HRM assay detecting human diarrheal parasites

Background

Intestinal parasitic diseases occur worldwide, and their diagnosis poses considerable challenges. Cryptosporidium spp., Entamoeba histolytica, Giardia intestinalis, (and, arguably, Dientamoeba fragilis and Blastocystis spp.) are among the most important and common parasitic protozoans causing diarrhea. Several multiplex real-time PCR assays have been developed for the synchronous detection of these parasites. However, most assays include the use of hydrolysis probes, increasing the cost of stool examination. In this study, we designed and evaluated a real-time PCR protocol, based on high-resolution melting (HRM) curve analysis, to simultaneously detect and differentiate five gastrointestinal parasites.

Results

Using a blinded panel of 143 clinical samples with laboratory diagnostic data to evaluate the method, we obtained a 95.8% concordance with conventional methods. Moreover, 4.2% of the samples were positive for D. fragilis and 2.8% additional Cryptosporidium infections were found with our multiplex assay. Our method is sensitive and specific for the selected parasites with the additional possibility of being run in single-plex as a backup control for mixed infections.

Conclusions

The assay is a convenient and cost-effective method that could contribute to a quicker and accurate diagnosis as well as to more targeted therapies of parasite-derived diarrhea. Finally, this new multiplex PCR assay could also be instrumental in epidemiology studies on these parasites.

Obesity and Sex Affect the Immune Responses to Tick-Borne Encephalitis Booster Vaccination

Obesity has dramatically increased over the last 30 years and reaches according to World Health Organization dimensions of a global epidemic. The obesity-associated chronic low-level inflammation contributes to severe comorbidities and directly affects many immune cells leading to immune dysfunction and increased susceptibility to infections. Thus, prophylaxis against vaccine-preventable diseases is crucial, yet the responsiveness to several vaccines is unclear under obesity. In order to assess the responsiveness to tick-borne encephalitis (TBE) vaccine, we revaccinated 37 obese individuals and 36 normal-weight controls with a licensed TBE vaccine. Metabolic, hormonal, and immunologic profiles along with vaccine-specific humoral and cellular immune responses were evaluated in sera and peripheral blood mononuclear cells (PBMCs) before, 1 week, 4 weeks, and 6 months after TBE booster. Obese adults had significantly increased metabolic (triglycerides, cholesterol ratios, leptin, insulin) and proinflammatory (C-reactive protein) parameters. They showed stronger initial increase of TBE-specific Ab titers (d7_d28) followed by a significantly faster decline after 6 months, which correlated with high body mass index and leptin and insulin levels. The fold increase of Ab-titer levels was significantly higher in obese compared to control males and linked to reduced testosterone levels. Obesity also affected cellular responses: PBMCs of the obese vaccinees had elevated interleukin 2 and interferon γ levels upon antigen stimulation, indicating a leptin-dependent proinflammatory T_H1 polarization. The expansion of total and naive B cells in obese might explain the initial increase of Ab titers, whereas the reduced B-memory cell and plasma blast generation could be related to fast Ab decline with a limited maintenance of titers. Among T follicular helper cell (Tfh) cells, the Tfh17 subset was significantly expanded particularly in obese males, where we observed a strong initial Ab increase. Systemic but not local vaccine side effects were more frequent in obese subjects as a possible consequence of their low-grade proinflammatory state. In summary, TBE booster vaccination was effective in obese individuals, yet the faster Ab decline could result in a reduced long-term protection. The sex-based differences in vaccine responses indicate a complex interplay of the endocrine, metabolic, and immune system during obesity. Further studies on the long-term protection after vaccination are ongoing, and also evaluation of primary vaccination against TBE in obese individuals is planned.

Clinical Trial Registration: NCT04017052; https://clinicaltrials.gov/ct2/show/NCT04017052.

A New Strategy Toward B Cell-Based Cancer Vaccines by Active Immunization With Mimotopes of Immune Checkpoint Inhibitors

Therapeutic monoclonal antibodies (mAbs), targeting tumor antigens, or immune checkpoints, have demonstrated a remarkable anti-tumor effect against various malignancies. However, high costs for mono- or combination therapies, associated with adverse effects or possible development of resistance in some patients, warrant further development and modification to gain more flexibility for this immunotherapy approach. An attractive alternative to passive immunization with therapeutic antibodies might be active immunization with mimotopes (B-cell peptides) representing the mAbs' binding epitopes, to activate the patient's own anti-tumor immune response following immunization. Here, we identified and examined the feasibility of inducing anti-tumor effects in vivo following active immunization with a mimotope of the immune checkpoint programmed cell death 1 (PD1), alone or in combination with a Her-2/neu B-cell peptide vaccine. Overlapping peptides spanning the extracellular domains of human PD1 (hPD1) were used to identify hPD1-derived mimotopes, using the therapeutic mAb Nivolumab as a proof of concept. Additionally, for in vivo evaluation in a tumor mouse model, a mouse PD1 (mPD1)-derived mimotope was identified using an anti-mPD1 mAb with mPD1/mPDL-1 blocking capacity. The identified mimotopes were characterized by in vitro assays, including a reporter cell-based assay, and their anti-tumor effects were evaluated in a syngeneic tumor mouse model stably expressing human Her-2/neu. The identified PD1-derived mimotopes were shown to significantly block the mAbs' capacity in inhibiting the respective PD1/PD-L1 interactions. A significant reduction in tumor growth in vivo was observed following active immunization with the mPD1-derived mimotope, associated with a significant reduction in proliferation and increased apoptotic rates in the tumors. Particularly, combined vaccination with the mPD1-derived mimotope and a multiple B-cell epitope Her-2/neu vaccine potentiated the vaccine's anti-tumor effect. Our results suggest active immunization with mimotopes of immune checkpoint inhibitors either as monotherapy or as combination therapy with tumor-specific vaccines, as a new strategy for cancer treatment.

Immunogenicity, safety, and tolerability of the measles-vectored chikungunya virus vaccine MV-CHIK: a double-blind, randomised, placebo-controlled and active-controlled phase 2 trial

BACKGROUND

Chikungunya fever is an emerging viral disease and substantial threat to public health. We aimed to assess the safety, tolerability, and immunogenicity of a live-attenuated, measles-vectored chikungunya vaccine (MV-CHIK).

METHODS

In this double-blind, randomised, placebo-controlled and active-controlled phase 2 trial, we enrolled healthy volunteers aged 18-55 years at four study sites in Austria and Germany. Participants were randomly assigned to receive intramuscular injections with MV-CHIK (5 × 10⁴ or 5 × 10⁵ 50% tissue culture infectious dose), control vaccine, or measles prime and MV-CHIK, in two different administration regimens. Randomisation was done by use of three-digit randomisation codes in envelopes provided by a data management service. The participants and investigators were masked to treatment assignment, which was maintained by use of sterile saline as a placebo injection. The primary endpoint was immunogenicity, defined as the presence of neutralising antibodies against chikungunya virus, at day 56, which is 28 days after one or two immunisations. The primary endpoint was assessed in all participants who completed the study without major protocol deviations (per-protocol population) and in all randomised participants who received at least one study treatment (modified intention-to-treat population). The safety analysis included all participants who received at least one study treatment. This trial is registered with ClinicalTrials.gov (NCT02861586) and EudraCT (2015-004037-26) and is completed.

FINDINGS

Between Aug 17, 2016, and May 31, 2017, we randomly assigned 263 participants to receive control vaccine (n=34), MV-CHIK (n=195), or measles prime and MV-CHIK (n=34). 247 participants were included in the per-protocol population. Neutralising antibodies against chikungunya virus were detected in all MV-CHIK treatment groups after one or two immunisations, with geometric mean titres ranging from 12·87 (95% CI 8·75-18·93) to 174·80 (119·10-256·50) and seroconversion rates ranging from 50·0% to 95·9% depending on the dose and administration schedule. Adverse events were similar between groups, with solicited adverse events reported in 168 (73%) of 229 participants assigned to MV-CHIK and 24 (71%) of 34 assigned to control vaccine (p=0·84) and unsolicited adverse events in 116 (51%) participants assigned to MV-CHIK and 17 (50%) assigned to control vaccine (p=1·00). No serious adverse events related to the vaccine were reported.

INTERPRETATION

MV-CHIK showed excellent safety and tolerability and good immunogenicity, independent of pre-existing immunity against the vector. MV-CHIK is a promising candidate vaccine for the prevention of chikungunya fever, an emerging disease of global concern.

FUNDING

Themis.

Vaccination of healthcare personnel in Europe: Update to current policies

We investigated and compared current national vaccination policies for health-care personnel (HCP) in Europe with results from our previous survey. Data from 36 European countries were collected using the same methodology as in 2011. National policies for HCP immunization were in place in all countries. There were significant differences in terms of number of vaccinations, target HCP and healthcare settings, and implementation regulations (recommended or mandatory vaccinations). Vaccination policies against hepatitis B and seasonal influenza were present in 35 countries each. Policies for vaccination of HCP against measles, mumps, rubella and varicella existed in 28, 24, 25 and 19 countries, respectively; and against tetanus, diphtheria, pertussis and poliomyelitis in 21, 20, 19, and 18 countries, respectively. Recommendations for hepatitis A immunization existed in 17 countries, and against meningococcus B, meningococcus C, meningococcus A, C, W, Y, and tuberculosis in 10, 8, 17, and 7 countries, respectively. Mandatory vaccination policies were found in 13 countries and were a pre-requisite for employment in ten. Comparing the vaccination programs of the 30 European countries that participated in the 2011 survey, we found that more countries had national vaccination policies against measles, mumps, rubella, hepatitis A, diphtheria, tetanus, poliomyelitis, pertussis, meningococcus C and/or meningococcus A, C, W, Y; and more of these implemented mandatory vaccination policies for HCP. In conclusion, European countries now have more comprehensive national vaccination programs for HCP, however there are still gaps. Given the recent large outbreaks of vaccine-preventable diseases in Europe and the occupational risk for HCP, vaccination policies need to be expanded and strengthened in several European countries. Overall, vaccination policies for HCP in Europe should be periodically re-evaluated in order to provide optimal protection against vaccine-preventable diseases and infection control within healthcare facilities for HCP and patients.