Abstract Background Antibody‐based tests are available for measuring SARS‐CoV‐2‐specific immune responses but fast T‐cell assays remain scarce. Robust T cell‐based tests are needed to differentiate specific cellular immune responses after infection from those after vaccination. Methods One hundred seventeen individuals (COVID‐19 convalescent patients: n = 40; SARS‐CoV‐2 vaccinees: n = 41; healthy controls: n = 36) were evaluated for SARS‐CoV‐2‐specific cellular immune responses (proliferation, Th1, Th2, Th17, and inflammatory cytokines, activation‐induced marker [AIM] expression) by incubating purified peripheral blood mononuclear cells (PBMC) or whole blood (WB) with SARS‐CoV‐2 peptides (S, N, or M), vaccine antigens (tetanus toxoid, tick borne encephalitis virus) or polyclonal stimuli ( Staphylococcal enterotoxin, phytohemagglutinin). Results N‐peptide mix stimulation of WB identified the combination of IL‐2 and IL‐13 secretion as superior to IFN‐γ secretion to discriminate between COVID‐19‐convalescent patients and healthy controls ( p < .0001). Comparable results were obtained with M‐ or S‐peptides, the latter almost comparably recalled IL‐2, IFN‐γ, and IL‐13 responses in WB of vaccinees. Analysis 10 months as opposed to 10 weeks after COVID‐19, but not allergic disease status, positively correlated with IL‐13 recall responses. WB cytokine responses correlated with cytokine and proliferation responses of PBMC. Antigen‐induced neo‐expression of the C‐type lectin CD69 on CD4 + ( p < .0001) and CD8 + ( p = .0002) T cells informed best about the SARS‐CoV‐2 exposure status with additional benefit coming from CD25 upregulation. Conclusion Along with N‐ and S‐peptide‐induced IL‐2 and CD69 neo‐expression, we suggest to include the type 2 cytokine IL‐13 as T‐cellular recall marker for SARS‐CoV‐2 specific T‐cellular immune responses after infection and vaccination.
Background: COVID-19 caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a recurrent endemic disease affecting the whole world. Since November 2021, Omicron and its subvariants are dominating. In order to prevent severe courses of disease, vaccines are needed to boost and maintain antibody levels capable of neutralizing Omicron. Recently we produced and characterized a SARS-CoV-2 vaccine based on a recombinant fusion protein consisting of hepatitis B virus (HBV)-derived PreS and two SARS-CoV-2 wild-type RBDs. Objectives: To develop a PreS-RBD vaccine which induces high levels of Omicron-specific neutralizing antibodies. Methods: We designed, produced, characterized and compared strain-specific (wild-type: W-PreS-W; Omicron: O-PreS-O), bivalent (mix of W-PreS-W and O-PreS-O) and chimeric (i.e., W-PreS-O) SARS-CoV-2 protein subunit vaccines. Immunogens were characterized in vitro by protein chemical methods, mass-spectrometry, circular dichroism in combination with thermal denaturation and immunological methods. In addition, BALB/c mice were immunized with aluminum hydroxide-adsorbed proteins and aluminum hydroxide alone (i.e., placebo) to study specific antibody and cytokine responses, safety and Omicron neutralization. Results: Defined and pure immunogens could be produced in large amounts as secreted and folded proteins in mammalian cells. Antibodies induced after vaccination with different doses of strain-specific, bivalent and chimeric PreS-RBD fusion proteins reacted with wild-type and Omicron RBD in a dose-dependent manner and resulted in a mixed Th1/Th2 immune response. Interestingly, RBD-specific IgG levels induced by the different vaccines were comparable but the W-PreS-O-induced virus neutralization titers against Omicron (median VNT50: 5000) were 7- and 2-fold higher than the W-PreS-W- and O-PreS-O-specific ones, respectively and 6-fold higher than those of the bivalent vaccine. Conclusion: Among the tested immunogens, the chimeric PreS-RBD subunit vaccine, W-PreS-O, induced the highest neutralizing antibody titers against Omicron. Thus, W-PreS-O seems to be a highly promising COVID-19 vaccine candidate for further preclinical and clinical evaluation.
Over the years, Chinese hamster ovary (CHO) cells have emerged as the major host for expressing biotherapeutic proteins. Traditional methods to generate high-producer cell lines rely on random integration(s) of the gene of interest but have thereby left the identification of bottlenecks as a challenging task. For comparison of different producer cell lines derived from various transfections, a system that provides control over transgene expression behavior is highly needed. This motivated us to develop a novel "DUKX-B11 F3/F" cell line to target different single-chain antibody fragments into the same chromosomal target site by recombinase-mediated cassette exchange (RMCE) using the flippase (FLP)/FLP recognition target (FRT) system. The RMCE-competent cell line contains a gfp reporter fused to a positive/negative selection system flanked by heterospecific FRT (F) variants under control of an external CMV promoter, constructed as "promoter trap". The expression stability and FLP accessibility of the tagged locus was demonstrated by successive rounds of RMCE. As a proof of concept, we performed RMCE using cassettes encoding two different anti-HIV single-chain Fc fragments, 3D6scFv-Fc and 2F5scFv-Fc. Both targeted integrations yielded homogenous cell populations with comparable intracellular product contents and messenger RNA (mRNA) levels but product related differences in specific productivities. These studies confirm the potential of the newly available "DUKX-B11 F3/F" cell line to guide different transgenes into identical transcriptional control regions by RMCE and thereby generate clones with comparable amounts of transgene mRNA. This new host is a prerequisite for cell biology studies of independent transfections and transgenes.
Introduction Pancreatic ductal adenocarcinoma (PDAC) remains a leading cause of cancer-related deaths worldwide with limited treatment options due to extensive radiation and chemotherapy resistance. Monotherapy with immune checkpoint blockade showed no survival benefit. A combination of immunomodulation and radiotherapy may offer new treatment strategies, as demonstrated for non-small cell lung cancer. Radiation-induced anti-tumour immunity is mediated through cytosolic nucleic acid sensing pathways that drive the expression of interferon beta-1 (IFNB1) and proinflammatory cytokines. Methods Human PDAC cell lines (PANC-1, MIA PaCa-2, BxPC-3) were treated with X-rays and protons. Immunogenic cell death was measured based on HMGB1 release. Cytosolic dsDNA and dsRNA were analysed by immunofluorescence microscopy. Cell cycle progression, MHC-I and PD-L1 expression were determined by flow cytometry. Galectin-1 and IFNB1 were measured by ELISA. The expression levels and the phosphorylation status of the cGAS/STING and RIG-I/MAVS signalling pathways were analysed by western blotting, the expression of IFNB1 and proinflammatory cytokines was determined by RT-qPCR and genome-wide by RNA-seq. CRISPR-Cas9 knock-outs and inhibitors were used to elucidate the relevance of STING, MAVS and NF-κB for radiation-induced IFNB1 activation. Results We demonstrate that a clinically relevant X-ray hypofractionation regimen (3x8 Gy) induces immunogenic cell death and activates IFNB1 and proinflammatory cytokines. Fractionated radiation induces G2/M arrest and accumulation of cytosolic DNA in PDAC cells, which partly originates from mitochondria. RNA-seq analysis shows a global upregulation of type I interferon response and NF-κB signalling in PDAC cells following 3x8 Gy. Radiation-induced immunogenic response is regulated by STING, MAVS and NF-κB. In addition to immunostimulation, radiation also induces immunosuppressive galectin-1. No significant changes in MHC-I or PD-L1 expression were observed. Moreover, PDAC cell lines show similar radiation-induced immune effects when exposed to single-dose protons or photons. Conclusion Our findings provide a rationale for combinatorial radiation-immunomodulatory treatment approaches in PDAC using conventional photon-based or proton beam radiotherapy.
This review highlights the recent key advances in the biology of CD4<sup>+</sup> effector T cells, antigen-presenting cells, Th17 and T regulatory cells, as well as immediate effector cells, such as mast cells, basophils and eosinophils, which are critically contributing to the better understanding of the pathophysiology of allergic diseases and are helping to improve their diagnosis and therapy. Some of the key advances with a direct impact on allergic asthma research and treatment are summarized.
To the Editor, As of today (February 14, 2022), more than 410 million persons (https://coronavirus.jhu.edu/map.html) have reportedly been infected by SARS-CoV-2. Furthermore, mass production and global application of COVID-19 vaccines have begun (Supplemental reference S3). Both factors certainly contribute to the fact, that although numbers of worldwide SARS-CoV-2 infections end of 2021 were more than double as high as in the end of 2020, the number of COVID-19-associated deaths has dropped to approximately 50% at the same time (https://coronavirus.jhu.edu/map.html). However, the immunity to SARS-CoV-2 which has been established so far is challenged by the appearance of SARS-CoV-2-variants which may escape cellular (Supplemental reference S4) and antibody-dependent immunity (Supplemental reference S5). The recently described variant of concern (VOC) Omicron, which has emerged in South Africa in November 2021, is spreading in the meantime rapidly all over the world and has become a matter of great concern because it shows more changes in the SARS-CoV-2 genome that may affect immunity as compared with earlier variants1 (Supplemental references S6–S9). In particular, Omicron has significantly more amino acid mutations in the SARS-CoV-2 receptor-binding domain (RBD), which binds to the ACE2 receptor on human cells, as compared with previous SARS-CoV-2 variants2 (Table S1). Antibodies directed to RBD are critically important for virus-neutralization because the RBD-ACE2 interaction represents the port of entry for the virus into cells leading to its replication in the host and to the consecutive spreading in the population.3, 4 The ability of RBD-specific antibodies to prevent RBD binding to ACE2 can be measured with surrogate molecular interaction assays,5 which mimic classical virus-neutralization tests3 and can therefore be quickly adapted to newly emerging SARS-CoV-2 variants of concern by using RBDs from the corresponding virus variants. Here, we compared the IgG recognition of RBD from the original Wuhan strain and recent variants of concern Delta (Pango B.1.617.2) and Omicron (Pango B.1.1.529) (Table S1) using sera from a random sample of adult COVID-19 convalescent patients (Table S2: C1-C20) and a random sample of adult subjects vaccinated two times (Table S3: D1-D10) or three times (Table S3: T1-T10) with a registered vector- (i.e., Vaxzevria) and/or mRNA-based vaccine (i.e., Comirnaty) (Figures 1 and 2; Table S4). Furthermore, we studied the ability of antibodies in these sera to inhibit the binding of RBD-Wuhan, RBD-Delta, and RBD-Omicron to ACE2 using the RBD-ACE2 molecular interaction assay described by Gattinger et al.5 (Figures 1 and 2, Table S4). Sera from convalescent patients had been obtained from April to July 2020,3 43–92 days (median 57.5 days) after the PCR confirmation of SARS-CoV-2 infection, sera from subjects vaccinated two times had been collected 26–31 days (median 27.5 days), and samples from subjects vaccinated three times were collected 23–40 days (median 28 days) after the last vaccination, respectively (Tables S2 and S3). There were no significant differences, regarding the levels of IgG antibodies specific for RBD-Wuhan (Table S4: Median OD C1-C20: 0.385; Median OD D1-D10: 0.453; Median OD T1-T10: 2.339) and RBD-Delta (Table S4: Median OD C1-C20: 0.379; Median OD D1-D10: 0.509; Median OD T1-T10: 2.470) (Table S4, Median reduction in binding comparing RBD-Wuhan with RBD-Delta: 4.3%), whereas RBD-Omicron-specific IgG levels (Table S4: Median OD C1-C20: 0.073; Median OD D1-D10: 0.128; Median OD T1-T10: 0.836) were significantly lower than those specific for RBD-Wuhan (Table S4, Median reduction of binding: 81.2%) and for RBD-Delta in the convalescent patients and vaccinated subjects (Figure 1A-C; Table S4). The RBD-specific IgG levels were in agreement with the results obtained regarding the inhibition of the RBD-ACE2 interaction by serum antibodies (Figure 1D-F). Antibodies from convalescent patients inhibited the binding of RBD-Wuhan and of RBD-Delta to ACE2 significantly stronger than the binding of RBD-Omicron to ACE2 (Figure 1D). In fact, RBD-Omicron binding to ACE2 was not inhibited by sera from convalescent patients in a relevant manner (Figure 1D). The inhibition of RBD-Omicron binding to ACE2 by sera from subjects who had received two immunizations was much lower than that observed for RBD-Wuhan (Table S4, Median reduction in inhibition 87.8%) and RBD-Delta but did not reach significance because a considerable number of these subjects vaccinated with Vaxzevria mounted significantly lower levels of S- and RBD-specific antibodies than those vaccinated twice with Comirnaty (Figure 2). Lower induction of Alpha and Delta neutralizing antibodies by two doses of Vaxzevria as compared with two doses of Comirnaty was also noted in another recent study.6 In subjects vaccinated three times, the inhibition of RBD-Omicron binding to ACE2 was significantly lower than that of RBD-Wuhan binding to ACE2 (Table S4, Median reduction of inhibition 27.7%) with two out of ten subjects (i.e., T1, T3, and Table S4) showing less than 50% inhibition. Figure 2 shows that the IgG antibody levels specific for S, RBD-Wuhan, RBD-Delta, and RBD-Omicron were higher in subjects who had received three immunizations than in those who had received two immunization, and this difference was significant for two doses of Vaxzevria. In fact, the inhibition of the binding of RBD-Wuhan, RBD-Delta, and RBD-Omicron to ACE2 was higher in subjects immunized with two doses of Comirnaty than in those who had received two doses of Vaxzevria (Figure 2E-G). Median RBD-Omicron-specific IgG levels were lower in subjects having received 2 doses of Vaxzevria and a third dose of Comirnaty, than in those who had been immunized with three doses of Comirnaty but this difference was not significant (Figure 2D). Interestingly, the median inhibition of RBD-Omicron binding to ACE2 was better for subjects treated 2xVaxzevria/1xComirnaty than for subjects treated with three doses Comirnaty (Figure 2G) but this difference was also not statistically significant. To study if the degree of inhibition in the RBD-ACE2 interaction of the variants is depending only on the levels of RBD-specific antibodies or if also other factors such as specificity and/or avidity of antibodies7 may play a role, we analyzed RBD levels and percentages of inhibition in parallel (Table S4). We found, that certain subjects (e.g., T1 and T3, Table S4) had relatively low levels of RBD-Omicron-specific IgG, and accordingly, there was no (i.e., T1) or low (i.e., T3) inhibition of RBD-Omicron binding to ACE2. However, we also found subjects with low levels of RBD-Omicron-specific IgG (i.e., T7, T8, and T10) with high inhibition of RBD-Omicron binding to ACE 2 (Table S4). This result together with the finding that the RBD-Omicron binding to ACE2 was even enhanced >20% for several convalescent patients (Figure 1D; Table S4: C1, C2, C4, C5, C9, C11, C16, C17, C19, and C20) would suggest, that factors, such as specificity and thus ability to form immune complexes7 as well as affinities/avidities of antibodies and not only their levels may guide the RBD-Omicron-ACE2 interaction.5, 7 In fact, we5 and later others8 noticed that sera from convalescent patients contain antibodies which seemed to be capable of forming immune complexes with RBD. Our current results indicate that this may also occur after vaccination. It is thus possible that such antibodies may form immune complexes with virus and/or S antigen produced after genetic vaccination at certain ratios of antibodies and antigen which then may result in antibody-dependent enhancement (ADE) of disease or other side effects but this has not yet been demonstrated. It may be considered as limitation of our study that we have only investigated antibody responses and their effects on the binding of RBD to ACE2 in molecular interaction assays and in a relatively limited number of subjects. However, our results are supported by three other very recent studies: One showed reduced neutralization of Omicron as compared with other variants after two doses of Vaxzevria or Comirnaty and in convalescent/vaccinated subjects6 and two others showing that even after three doses of Comirnaty neutralization of Omicron was lower than that of previous variants.1, 9 Our study provides additional information as it indicates that cross-vaccination with two doses Vaxzevria followed by a booster with Comirnaty may eventually provide slightly better Omicron neutralization than three vaccinations with Comirnaty but further studies are needed to confirm this. In summary, we demonstrate that RBD-Omicron is recognized much less by IgG antibodies from convalescent patients and by subjects immunized with vaccines based on SARS-CoV-2 Wuhan, even when immunized three times. Furthermore, antibodies from convalescent patients and vaccinated subjects inhibited the interaction of RBD-Omicron to ACE2 much less than the interaction between RBD-Wuhan and RBD-Delta and ACE2, respectively. Omicron-induced disease severity seems to be lower due to possible intrinsic features of this variant and/or the fact that a considerable proportion of the population has developed SARS-CoV-2-specific T cell (Supplemental reference S10) and antibody responses. However, Omicron has re-infected a large number of convalescent and vaccinated subjects which according to our results may be attributed to the reduced capacity of antibodies specific for earlier variants to inhibit the binding of Omicron to the ACE2 receptor. SARS-CoV-2-protective antibody responses have been shown to drop relatively quickly, and Omicron has now shown that SARS-CoV-2 variants can develop which escape protective antibody responses specific for earlier variants induced by infection or vaccination. Therefore, Omicron appears to be a variant of real concern, especially for vulnerable persons, and it will be important to adapt vaccines and vaccination strategies to SARS-CoV- 2 Omicron and newly evolving escape variants. This may be achieved by combination vaccines including the most divergent SARS-CoV-2 variants capable of inducing broad immunity. We wish to acknowledge the help of Doris Werjant-Locmele and Anna Guentcheva regarding the recruitment and administration of study subjects. We are grateful to all individuals who participated in our study. Rudolf Valenta has received research grants from HVD Life-Sciences, Vienna, Austria, WORG Pharmaceuticals, Hangzhou, China and from Viravaxx AG, Vienna, Austria. He serves as consultant for Viravaxx AG and WORG Pharmaceuticals. The other authors have no conflict of interest to declare. PG: Designed and performed experiments, analyzed data, wrote manuscript, and read manuscript; IT, KB, and AK: Performed experiments, analyzed data, read manuscript, and provided samples and clinical data; BK and DT: Performed experiments, analyzed data, and read manuscript; WFP: Analyzed data and read manuscript; RV: Analyzed data, wrote manuscript, read manuscript, and designed and supervized experiments. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.