Optogenetic manipulation identifies the roles of ERK and AKT dynamics in controlling mouse embryonic stem cell exit from pluripotency

ERK and AKT signaling control pluripotent cell self-renewal versus differentiation. ERK pathway activity over time (i.e., dynamics) is heterogeneous between individual pluripotent cells, even in response to the same stimuli. To analyze potential functions of ERK and AKT dynamics in controlling mouse embryonic stem cell (ESC) fates, we developed ESC lines and experimental pipelines for the simultaneous long-term manipulation and quantification of ERK or AKT dynamics and cell fates. We show that ERK activity duration or amplitude or the type of ERK dynamics (e.g., transient, sustained, or oscillatory) alone does not influence exit from pluripotency, but the sum of activity over time does. Interestingly, cells retain memory of previous ERK pulses, with duration of memory retention dependent on duration of previous pulse length. FGF receptor/AKT dynamics counteract ERK-induced pluripotency exit. These findings improve our understanding of how cells integrate dynamics from multiple signaling pathways and translate them into cell fate cues.

Embryonic stem cell ERK, AKT, plus STAT3 response dynamics combinatorics are heterogeneous but NANOG state independent

Signaling is central in cell fate regulation, and relevant information is encoded in its activity over time (i.e., dynamics). However, simultaneous dynamics quantification of several pathways in single mammalian stem cells has not yet been accomplished. Here we generate mouse embryonic stem cell (ESC) lines simultaneously expressing fluorescent reporters for ERK, AKT, and STAT3 signaling activity, which all control pluripotency. We quantify their single-cell dynamics combinations in response to different self-renewal stimuli and find striking heterogeneity for all pathways, some dependent on cell cycle but not pluripotency states, even in ESC populations currently assumed to be highly homogeneous. Pathways are mostly independently regulated, but some context-dependent correlations exist. These quantifications reveal surprising single-cell heterogeneity in the important cell fate control layer of signaling dynamics combinations and raise fundamental questions about the role of signaling in (stem) cell fate control.

Eliciting Patient Insights on the Burden of Nontuberculous Mycobacterial Lung Disease (NTM-LD) and Healthcare Gaps in Germany Through Qualitative Semi-structured Interviews

INTRODUCTION

Nontuberculous mycobacterial lung disease (NTM-LD) is a rare but growing health concern, particularly affecting vulnerable patients with chronic lung conditions. Understanding the patients' perspective on their disease and treatment expectations can help to identify healthcare gaps and improve overall patient care. Therefore, the main objective of the survey study was the evaluation of patient insights on the burden of the disease and healthcare gaps.

METHODS

The study used an online survey as a pre-screener to facilitate recruitment followed by semi-structured qualitative interviews. The interviews were conducted by phone from April 2019 to February 2020 in German language. Only patients with a self-reported confirmed NTM-LD diagnosis, managed and insured in Germany were included in this study.

RESULTS

In total, 20 semi-structured qualitative interviews were conducted. Most (85%) patients had at least one coexisting pulmonary condition with cystic fibrosis (CF, n = 9) being most common. Chronic cough, fatigue, and dyspnea were the most reported symptoms. Of all the symptoms reported, fatigue was perceived as the most burdensome and 85% of patients felt limited in their daily life. It took a median of 5 months for patients to receive an accurate diagnosis of NTM-LD and that time was doubled when excluding patients with CF (range 0-480 months). Ninety percent of interviewed patients (n = 18) received drug treatment for NTM-LD and most of them (n = 17) reported having experienced side effects from their treatment. Patients' expressed a particular need for more comprehensive and reliable patient-friendly information on NTM-LD and a better awareness of physicians as well.

CONCLUSIONS

NTM-LD can considerably impair the lives of patients and their families and/or caregivers. A multidisciplinary approach and establishment of more widespread regional expert centers for NTM-LD management in Germany with well-structured referral and communication pathways accompanied by peer-to-peer support of patient advocacy groups are urgently needed.

Flow chamber staining modality for real-time inspection of dynamic phenotypes in multiple histological stains

Traditional histological stains, such as hematoxylin-eosin (HE), special stains, and immunofluorescence (IF), have defined myriads of cellular phenotypes and tissue structures in a separate stained section. However, the precise connection of information conveyed by the various stains in the same section, which may be important for diagnosis, is absent. Here, we present a new staining modality-Flow chamber stain, which complies with the current staining workflow but possesses newly additional features non-seen in conventional stains, allowing for (1) quickly switching staining modes between destain and restain for multiplex staining in one single section from routinely histological preparation, (2) real-time inspecting and digitally capturing each specific stained phenotype, and (3) efficiently synthesizing graphs containing the tissue multiple-stained components at site-specific regions. Comparisons of its stains with those by the conventional staining fashions using the microscopic images of mouse tissues (lung, heart, liver, kidney, esophagus, and brain), involving stains of HE, Periodic acid-Schiff, Sirius red, and IF for Human IgG, and mouse CD45, hemoglobin, and CD31, showed no major discordance. Repetitive experiments testing on targeted areas of stained sections confirmed the method is reliable with accuracy and high reproducibility. Using the technique, the targets of IF were easily localized and seen structurally in HE- or special-stained sections, and the unknown or suspected components or structures in HE-stained sections were further determined in histological special stains or IF. By the technique, staining processing was videoed and made a backup for off-site pathologists, which facilitates tele-consultation or -education in current digital pathology. Mistakes, which might occur during the staining process, can be immediately found and amended accordingly. With the technique, a single section can provide much more information than the traditional stained counterpart. The staining mode bears great potential to become a common supplementary tool for traditional histopathology.

Definition of a sectioning plane and place for a section containing hoped-for regions using a spare counterpart specimen

Histological examination of targets in regions of interest in histological sections is one of the most frequently used tools in biomedical research. However, it is a technical challenge to secure a multitarget section for inspection of the structure’s mutual relationship of targets or a longitudinally filamentous- or tubular-formed tissue section for visitation of the overall morphological features. We present a method with a specified cutting plane and place, allowing researchers to cut directly at the multitarget centers accurately and quickly. The method is proven to be reliable with high accuracy and reproducibility and a low coefficient of variation, testing on repeat experiments of three target’s position-known models. With this method, we successfully yielded single sections containing whole intraorbital optical nerves, three aortic valves, or whole thoracic tracheas in their central positions. The adjoined custom-made tools used in the study, such as various tissue-specific formulated calibrated trimming and embedding guides, an organ-shaped cavity plaster mold, and a two-time embedding technique for optimal and identical trimming or embedding, also bear great potential to become a common supplemental tool for traditional histology and may contribute to the reduction of the labor, and the number of animals needed.

A fructosylated peptide derived from a collagen II T cell epitope for long-term treatment of arthritis (FIA-CIA) in mice

Rheumatoid arthritis (RA) is a systemic inflammatory autoimmune disease which affects primarily the joints. Peptides of several proteins have shown an effect in some experimental animal models of RA. We investigated arthritis development in male DBA/1 mice which were injected with bovine collagen II (bCII) and human fibrinogen (hFib) on days 0 and 21, leading to stable and reproducible disease induction in 100% of immunized mice (FIA-CIA). In a second study, two bCII-derived peptides were given three times in the course of 6 weeks after FIA-CIA induction to test for impact on arthritis. Mice were scored weekly for arthritis and anti-citrullinated peptide antibodies (ACPAs) were determined in the sera taken on days 0, 14, 35, 56 and 84. Histology of the hind paws was performed at the end of the experiment. Intravenous administration of peptide 90578, a novel fructosylated peptide derived from the immunodominant T cell epitope of bCII, at a dosage of 1 mg/kg resulted in significant beneficial effects on clinical outcome parameters and on the arthritis histology scores which was sustained over 12 weeks. Survival tended to be improved in peptide 90578-treated mice. Intravenous administration of pure soluble peptide 90578 without adjuvants is a promising approach to treat RA, with treatment starting at a time when ACPAs are already present. The results complement existing data on peptide "vaccination" of healthy animals, or on treatment using recombinant peptide expressing virus or complex biological compounds.

A cyclic peptide significantly improves thyroid function, thyrotropin-receptor antibodies and orbital mucine /collagen content in a long-term Graves' disease mouse model

BACKGROUND

BALB/c mice which received long-term immunizations of adenovirus (Ad) expressing thyrotropin receptor A-subunits (TSHR) developed stable Graves' disease (GD). TSHR-derived cyclic peptide 19 (P19) was identified as effective therapy in this model.

METHODS

In Ad-TSHR mice, we investigated shorter disease intervals up to 4 months for histological alterations of the orbits, fine tuning of anti-TSHR antibodies (Ab) and free thyroxine (fT4) hormone levels by using novel detection methods in an independent laboratory. Therapy (0.3 mg/kg P19 or vehicle) was given intravenously after the fourth Ad-TSHR immunization (week 11) and continued until week 19.

RESULTS

Thyrotropin binding inhibitory immunoglobulins (TBII, bridge immunoassay), blocking (TBAb) and stimulating (TSAb) TSHR-Ab (both cell-based bioassays) and serum levels of fT4 were significantly elevated at week 11 in Ad-TSHR-immunized mice versus none in control mice. For the first time, TSAb, TBAb, and thyroperoxidase-Ab were detected in 17 of 19, 12/19 and 6/19 Ad-TSHR immunized mice, respectively at week 21. Also, for the first time, this study showed that P19 treatment markedly reduced serum TBII (p < 0.0001), serum fT4 (p = 0.02), and acidic mucins and collagen content in the orbital tissue of Ad-TSHR-immunized mice.

CONCLUSION

P19 significantly improved thyroid function, confirming previous results in an independent second laboratory. A relevant shift of anti-TSHR antibody subpopulations in response to P19 therapy may help explain its immunological effects. Moreover, P19 exerted a beneficial effect on mucine and collagen content of orbital tissue. Hence, P19 offers a potential novel therapeutic approach for GD and associated orbitopathy.

Isolation and light chain shuffling of a Plasmodium falciparum AMA1-specific human monoclonal antibody with growth inhibitory activity

Background

Plasmodium falciparum, the parasite causing malaria, affects populations in many endemic countries threatening mainly individuals with low malaria immunity, especially children. Despite the approval of the first malaria vaccine Mosquirix™ and very promising data using cryopreserved P. falciparum sporozoites (PfSPZ), further research is needed to elucidate the mechanisms of humoral immunity for the development of next-generation vaccines and alternative malaria therapies including antibody therapy. A high prevalence of antibodies against AMA1 in immune individuals has made this antigen one of the major blood-stage vaccine candidates.

Material and methods

Using antibody phage display, an AMA1-specific growth inhibitory human monoclonal antibody from a malaria-immune Fab library using a set of three AMA1 diversity covering variants (DiCo 1–3), which represents a wide range of AMA1 antigen sequences, was selected. The functionality of the selected clone was tested in vitro using a growth inhibition assay with P. falciparum strain 3D7. To potentially improve affinity and functional activity of the isolated antibody, a phage display mediated light chain shuffling was employed. The parental light chain was replaced with a light chain repertoire derived from the same population of human V genes, these selected antibodies were tested in binding tests and in functionality assays.

Results

The selected parental antibody achieved a 50% effective concentration (EC₅₀) of 1.25 mg/mL. The subsequent light chain shuffling led to the generation of four derivatives of the parental clone with higher expression levels, similar or increased affinity and improved EC₅₀ against 3D7 of 0.29 mg/mL. Pairwise epitope mapping gave evidence for binding to AMA1 domain II without competing with RON2.

Conclusion

We have thus shown that a compact immune human phage display library is sufficient for the isolation of potent inhibitory monoclonal antibodies and that minor sequence mutations dramatically increase expression levels in Nicotiana benthamiana. Interestingly, the antibody blocks parasite inhibition independently of binding to RON2, thus having a yet undescribed mode of action.

Impact of device landing zone calcification patterns on paravalvular regurgitation after transcatheter aortic valve replacement with different next-generation devices

OBJECTIVE

Residual paravalvular regurgitation (PVR) has been associated to adverse outcomes after transcatheter aortic valve replacement (TAVR). This study sought to evaluate the impact of device landing zone (DLZ) calcification on residual PVR after TAVR with different next-generation transcatheter heart valves.

METHODS

642 patients underwent TAVR with a SAPIEN 3 (S3; n=292), ACURATE neo (NEO; n=166), Evolut R (ER; n=132) or Lotus (n=52). Extent, location and asymmetry of DLZ calcification were assessed from contrast-enhanced CT imaging and correlated to PVR at discharge.

RESULTS

PVR was ≥moderate in 0.7% of S3 patients, 9.6% of NEO patients, 9.8% of ER patients and 0% of Lotus patients (p<0.001), and these differences remained after matching for total DLZ calcium volume. The amount of DLZ calcium was significantly related to the degree of PVR in patients treated with S3 (p=0.045), NEO (p=0.004) and ER (p<0.001), but not in Lotus patients (p=0.698). The incidence of PVR ≥moderate increased significantly over the tertiles of DLZ calcium volume (p=0.046). On multivariable analysis, calcification of the aortic valve cusps, LVOT calcification and the use of self-expanding transcatheter aortic valve implantation (TAVI) prostheses emerged as predictors of PVR.

CONCLUSIONS

The susceptibility to PVR depending on the amount of calcium was mainly observed in self-expanding TAVI prostheses. Thus, DLZ calcification is an important factor to be considered in prosthesis selection for each individual patient, keeping in mind the trade-off between PVR reduction, risk of new pacemaker implantation and unfavourable valve ha emodynamics.

Histo-ELISA technique for quantification and localization of tissue components

A novel Histo-ELISA technique is intended to facilitate quantification of target tissue proteins in a tissue section and involves the selection of target regions in the tissue section, application of streptavidin-conjugated HRP (horseradish peroxidase), coupled with peroxidase substrate—TMB (3,3′,5,5′-tetramethylbenzidine), and staining dye evaluation with ELISA reader. The target protein content (weight per volume unit) was translated from optical densities by a reference standard curve, obtained via parallel staining of the targeted protein-coated slides. To validate the technique, we carried out quantifications of IgG extravasation in ischemic and nonischemic brain sections in a mouse stroke model. With those obtained data and the reference of immunohistochemistry scores assessed on the adjacent sections, accuracy, sensitivity, and precision for the technique were evaluated. For all evaluated parameters, Histo-ELISA performance was either comparable to or better than the standard immunohistochemistry. A comparison with the data from the repeated measurements yielded a rather low coefficient of variation. The results confirmed that the technique is a fairly reliable quantitative test with rather high sensitivity, accuracy, precision, and reproducibility for detecting target protein content in tissue sections and that its tissue distribution and related subsequent morphological changes can be observed at the same time.

Thyroid-stimulating hormone receptor (TSHR) fusion proteins in Graves' disease

Graves' disease is an autoimmune disorder, which is characterized by stimulatory antibodies targeting the human thyrotropin receptor (TSHR), resulting in hyperthyroidism and multiple organ damage. We systematically investigated monomeric and dimeric fusion proteins of the A subunit of TSHR for efficacy to bind to the monoclonal patient antibody M22, to interact with Graves' patient serum samples, and to impact on anti-TSHR antibody titers, hyperthyroidism, tachycardia and other in vivo read-outs in a long-term mouse model of Graves' disease induced by immunization with a recombinant adenovirus encoding TSHR A. Binding assays and functional measurements of TSHR-dependent cAMP formation showed binding of monomeric TSHR-His and dimeric TSHR-Fc to the anti-TSHR antibody M22 at low-effective concentrations (EC50 of 5.7 nmol/L and 8.6 nmol/L) and inhibition of the effects of this antibody at high efficiencies (IC50 values of 16-20 nmol/L). Both proteins also block the effects of polyclonal anti-TSHR antibodies occurring in Graves' patient sera with somewhat lower average efficiencies (mean IC50 values of 29 nmol/L and 68 nmol/L). However, in vivo characterization of epicutaneous patch administrations of TSHR-Fc at doses of 0.3 and 0.6 mg/kg body weight in a murine Graves' disease model did not result in any improvement of disease parameters. In conclusion, high affinity binding of TSHR-Fc to pathological anti-TSHR antibodies was not matched by efficacy to improve Graves' disease parameter in a long-term mouse model.

SAT-557 Functional Thyrotropin Receptor Antibodies Confirm a Novel Graves' Disease Animal Model

Background / Objectives: A novel long-term animal model for human Graves’ disease (GD) was recently established in mice (Endocrinology 2015; 156: 1577-1589) using nine immunizations with recombinant adenovirus (Ad) expressing the extracellular A-subunit of the human thyrotropin receptor (TSHR) over 10 months. The aim of the present study is to detect and measure TSHR-Ab in the animal model of Ad-TSHR immunized mice. Methods: Female BALB/c mice received either 10¹⁰ plaque-forming units of adenovirus carrying the A-subunit of the TSHR gene or the green fluorescent protein (GFP) gene (injected into the femoral muscles). In addition, age-matched immunologically naïve mice were studied. Blood was withdrawn out of the left or right tail vein or intracardially (end of the study). The study protocol used three three-weekly immunizations (initiation), followed by a maintenance phase with further regular four-weekly boosts until the ninth immunization. Serum TSHR stimulating (TSAb) and -blocking (TBAb) Ab were measured with reporter bioassays. TSAb was reported as percentage of specimen-to-reference ratio (cut-off SRR% <140). Blocking activity was defined as percent inhibition of luciferase expression relative to induction with bovine TSH alone (% inhibition <34). Results: A total of twenty-two BALB/c mice were studied (ten, eight, and four Ad-TSHR, control, and Ad-GFP-immunized mice, respectively). All twelve control- and Ad-GFP-immunized mice were negative for both thyrotropin-binding inhibitory immunoglobulins (TBII) as well as for TSAb and TBAb measured with the cell-based bioassays. In contrast, baseline TBII were highly positive in all Ad-TSHR-immunized mice (median 40 IU/L, 25%-75% percentiles 40-40 IU/L, normal cut-off 0.55 IU/L) All these mice also developed hyperthyroidism with elevated free T4 (fT4) levels (median 4.5 ng/dl, 25-75 percentile 4.1-6 ng/dl; normal range 0.9-1.8 ng/dl). All control (0.1, 0.1-0.1 IU/L) and Ad-GFP-immunized (0.2, 0.1-0.3 IU/L) mice were TBII negative and the corresponding fT4 levels were 2.2 ng/dl (2.1-2.4 ng/dl) and 2 ng/dl (1.9-2.1 ng/dl), respectively (p<0.001 for both TBII and fT4 versus Ad-TSHR mice). The serum positivity for TSAb and TBAb in a total of 28 consecutive samples obtained from ten Ad-TSHR mice was 12 (43%) and 21 (75%), respectively. Especially, serum samples of two (20%) Ad-TSHR mice were highly positive in the TSAb bioassay only with a SRR% value of 397 (329-465, p<0.001 vs. control mice). In comparison, sera of four Ad-TSHR mice (40%) were highly positive when measured with the TBAb bioassay only showing a % inhibition value of 69 (63-76). Furthermore, serum samples of four Ad-TSHR mice (40%) demonstrated dual TSAb/TBAb positivity. Conclusions: Functional TSHR-Ab are highly prevalent in Ad-TSHR immunized mice, thus confirming the successful establishment of a novel, long-term animal model for GD.

Automated Microfluidic System for Dynamic Stimulation and Tracking of Single Cells

Dynamic environments determine cell fate decisions and function. Understanding the relationship between extrinsic signals on cellular responses and cell fate requires the ability to dynamically change environmental inputs in vitro, while continuously observing individual cells over extended periods of time. This is challenging for nonadherent cells, such as hematopoietic stem and progenitor cells, because media flow displaces and disturbs such cells, preventing culture and tracking of single cells. Here, we present a programmable microfluidic system designed for the long-term culture and time-lapse imaging of nonadherent cells in dynamically changing cell culture conditions without losing track of individual cells. The dynamic, valve-controlled design permits targeted seeding of cells in up to 48 independently controlled culture chambers, each providing sufficient space for long-term cell colony expansion. Diffusion-based media exchange occurs rapidly and minimizes displacement of cells and eliminates shear stress. The chip was successfully tested with long-term culture and tracking of primary hematopoietic stem and progenitor cells, and murine embryonic stem cells. This system will have important applications to analyze dynamic signaling inputs controlling fate choices.

Inductive and Selective Effects of GSK3 and MEK Inhibition on Nanog Heterogeneity in Embryonic Stem Cells

Embryonic stem cells (ESCs) display heterogeneous expression of pluripotency factors such as Nanog when cultured with serum and leukemia inhibitory factor (LIF). In contrast, dual inhibition of the signaling kinases GSK3 and MEK (2i) converts ESC cultures into a state with more uniform and high Nanog expression. However, it is so far unclear whether 2i acts through an inductive or selective mechanism. Here, we use continuous time-lapse imaging to quantify the dynamics of death, proliferation, and Nanog expression in mouse ESCs after 2i addition. We show that 2i has a dual effect: it both leads to increased cell death of Nanog low ESCs (selective effect) and induces and maintains high Nanog levels (inductive effect) in single ESCs. Genetic manipulation further showed that presence of NANOG protein is important for cell viability in 2i medium. This demonstrates complex Nanog-dependent effects of 2i treatment on ESC cultures.

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Continuous long-term single-cell quantification of 2i effects on murine ESCs

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2i enriches for a Nanog high population through a selective cell death effect

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2i also upregulates Nanog expression and prevents its downregulation

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The viability of Nanog^−/− cells is compromised in 2i

Cyclic Peptides for Effective Treatment in a Long-Term Model of Graves Disease and Orbitopathy in Female Mice

A model for human Graves disease in mice was used to compare several treatment approaches. The mice received regular adenovirus (Ad) thyroid-stimulating hormone receptor (TSHR) A subunit immunizations (injections every 4 weeks). The generation of anti-TSHR antibodies, enlarged thyroid sizes (goiter), elevated serum thyroxine levels, retro-orbital fibrosis, and cardiac involvement (tachycardia and hypertrophy) were consistently observed over 9 months. Treatment of established disease in these mice using cyclic peptides that mimic one of the cylindrical loops of the TSHR leucine-rich repeat domain improved or cured all investigated parameters after six consecutive monthly injections. The first significant beneficial effects were observed 3 to 4 months after starting these therapies. In immunologically naïve mice, administration of any of the cyclic peptides did not induce any immune response. In contrast, monthly injections of the full antigenic TSHR A domain as fusion protein with immunoglobulin G crystallizable fragment induced clinical signs of allergy in Ad-TSHR-immunized mice and anti-TSHR antibodies in naïve control mice. In conclusion, cyclic peptides resolved many clinical findings in a mouse model of established Graves disease and orbitopathy. In contrast to blocking TSHR by allosteric modulation, the approach does not incur a direct receptor antagonism, which might offer a favorable side effect profile.

Immunization with the Malaria Diversity-Covering Blood-Stage Vaccine Candidate Plasmodium falciparum Apical Membrane Antigen 1 DiCo in Complex with Its Natural Ligand PfRon2 Does Not Improve the In Vitro Efficacy

The blood-stage malaria vaccine candidate Plasmodium falciparum apical membrane antigen 1 (PfAMA1) can induce strong parasite growth-inhibitory antibody responses in animals but has not achieved the anticipated efficacy in clinical trials. Possible explanations in humans are the insufficient potency of the elicited antibody responses, as well as the high degree of sequence polymorphisms found in the field. Several strategies have been developed to improve the cross-strain coverage of PfAMA1-based vaccines, whereas innovative concepts to increase the potency of PfAMA1-specific IgG responses have received little attention even though this may be an essential requirement for protective efficacy. A previous study has demonstrated that immunization with a complex of PyAMA1 and PyRON2, a ligand with an essential functional role in erythrocyte invasion, leads to protection from lethal Plasmodium yoelli challenge in an animal model and suggested to extend this strategy toward improved strain coverage by using multiple PfAMA1 alleles in combination with PfRon2L. As an alternative approach along this line, we decided to use PfRon2L in combination with three PfAMA1 diversity covering variants (DiCo) to investigate the potential of this complex to induce more potent parasite growth inhibitory immune response in combination with better cross-strain-specific efficacy. Within the limits of the study design, the ability of the PfAMA1 DiCo-Mix to induce cross-strain-specific antibodies was not affected in all immunization groups, but the DiCo-PfRon2L complexes did not improve the potency of PfAMA1-specific IgG responses.

Characterization of a novel inhibitory human monoclonal antibody directed against Plasmodium falciparum Apical Membrane Antigen 1

Malaria remains a major challenge to global health causing extensive morbidity and mortality. Yet, there is no efficient vaccine and the immune response remains incompletely understood. Apical Membrane Antigen 1 (AMA1), a leading vaccine candidate, plays a key role during merozoite invasion into erythrocytes by interacting with Rhoptry Neck Protein 2 (RON2). We generated a human anti-AMA1-antibody (humAbAMA1) by EBV-transformation of sorted B-lymphocytes from a Ghanaian donor and subsequent rescue of antibody variable regions. The antibody was expressed in Nicotiana benthamiana and in HEK239-6E, characterized for binding specificity and epitope, and analyzed for its inhibitory effect on Plasmodium falciparum. The generated humAbAMA1 shows an affinity of 106-135 pM. It inhibits the parasite strain 3D7A growth in vitro with an expression system-independent IC50-value of 35 μg/ml (95% confidence interval: 33 μg/ml-37 μg/ml), which is three to eight times lower than the IC50-values of inhibitory antibodies 4G2 and 1F9. The epitope was mapped to the close proximity of the RON2-peptide binding groove. Competition for binding between the RON2-peptide and humAbAMA1 was confirmed by surface plasmon resonance spectroscopy measurements. The particularly advantageous inhibitory activity of this fully human antibody might provide a basis for future therapeutic applications.

Analysis of the dose-dependent stage-specific in vitro efficacy of a multi-stage malaria vaccine candidate cocktail

Background

The high incidence and mortality rate of malaria remains a serious burden for many developing countries, and a vaccine that induces durable and highly effective immune responses is, therefore, desirable. An earlier analysis of the stage-specific in vitro efficacy of a malaria vaccine candidate cocktail (VAMAX) considered the general properties of complex multi-component, multi-stage combination vaccines in rabbit immunization experiments using a hyper-immunization protocol featuring six consecutive boosts and a strong, lipopolysaccharide-based adjuvant. This follow-up study investigates the effect of antigen dose on the in vitro efficacy of the malaria vaccine cocktail using a conventional vaccination scheme (one prime and two boosts) and a human-compatible adjuvant (Alhydrogel^®).

Results

IgG purified from rabbits immunized with 0.1, 1, 10 or 50 µg doses of the VAMAX vaccine candidate cocktail was analysed for total IgG and antigen-cocktail-specific titers. An increase in cocktail-specific titers was observed between 0.1 and 1 µg and between 10 and 50 µg, whereas no significant difference in titers was observed between 1 and 10 µg. Antigen component-specific antibody titers and stage-specific in vitro efficacy assays were performed with pooled IgG from animals immunized with 1 and 50 µg of the VAMAX cocktail. Here, the component-specific antibody levels showed clear dose dependency whereas the determined stage-specific in vitro IC₅₀ values (as a correlate of efficacy) were only dependent on the titer amounts of stage-specific antibodies.

Conclusions

The stage-specific in vitro efficacy of the VAMAX cocktail strongly correlates with the corresponding antigen-specific titers, which for their part depend on the antigen dose, but there is no indication that the dose has an effect on the in vitro efficacy of the induced antibodies. A comparison of these results with those obtained in the previous hyper-immunization study (where higher levels of antigen-specific IgG were observed) suggests that there is a significant need to induce an immune response matching efficacy requirements, especially for a PfAMA1-based blood stage vaccine, by using higher doses, better adjuvants and/or better formulations.

Spatio-temporal co-ordination of RhoA, Rac1 and Cdc42 activation during prototypical edge protrusion and retraction dynamics

The three canonical Rho GTPases RhoA, Rac1 and Cdc42 co-ordinate cytoskeletal dynamics. Recent studies indicate that all three Rho GTPases are activated at the leading edge of motile fibroblasts, where their activity fluctuates at subminute time and micrometer length scales. Here, we use a microfluidic chip to acutely manipulate fibroblast edge dynamics by applying pulses of platelet-derived growth factor (PDGF) or the Rho kinase inhibitor Y-27632 (which lowers contractility). This induces acute and robust membrane protrusion and retraction events, that exhibit stereotyped cytoskeletal dynamics, allowing us to fairly compare specific morphodynamic states across experiments. Using a novel Cdc42, as well as previously described, second generation RhoA and Rac1 biosensors, we observe distinct spatio-temporal signaling programs that involve all three Rho GTPases, during protrusion/retraction edge dynamics. Our results suggest that Rac1, Cdc42 and RhoA regulate different cytoskeletal and adhesion processes to fine tune the highly plastic edge protrusion/retraction dynamics that power cell motility.

Acquired immune responses to three malaria vaccine candidates and their relationship to invasion inhibition in two populations naturally exposed to malaria

Background

Malaria still represents a major cause of morbidity and mortality predominantly in several developing countries, and remains a priority in many public health programmes. Despite the enormous gains made in control and prevention the development of an effective vaccine represents a persisting challenge. Although several parasite antigens including pre-erythrocytic antigens and blood stage antigens have been thoroughly investigated, the identification of solid immune correlates of protection against infection by Plasmodium falciparum or clinical malaria remains a major hurdle. In this study, an immuno-epidemiological survey was carried out between two populations naturally exposed to P. falciparum malaria to determine the immune correlates of protection.

Methods

Plasma samples of immune adults from two countries (Ghana and Madagascar) were tested for their reactivity against the merozoite surface proteins MSP1-19, MSP3 and AMA1 by ELISA. The antigens had been selected on the basis of cumulative evidence of their role in anti-malarial immunity. Additionally, reactivity against crude P. falciparum lysate was investigated. Purified IgG from these samples were furthermore tested in an invasion inhibition assay for their antiparasitic activity.

Results

Significant intra- and inter- population variation of the reactivity of the samples to the tested antigens were found, as well as a significant positive correlation between MSP1-19 reactivity and invasion inhibition (p < 0.05). Interestingly, male donors showed a significantly higher antibody response to all tested antigens than their female counterparts. In vitro invasion inhibition assays comparing the purified antibodies from the donors from Ghana and Madagascar did not show any statistically significant difference. Although in vitro invasion inhibition increased with breadth of antibody response, the increase was not statistically significant.

Conclusions

The findings support the fact that the development of semi-immunity to malaria is probably contingent on the development of antibodies to not only one, but a range of antigens and that invasion inhibition in immune adults may be a function of antibodies to various antigens. This supports strategies of vaccination including multicomponent vaccines as well as passive vaccination strategies with antibody cocktails.

A Plant-Based Transient Expression System for the Rapid Production of Malaria Vaccine Candidates

There are currently no vaccines that provide sterile immunity against malaria. Various proteins from different stages of the Plasmodium falciparum life cycle have been evaluated as vaccine candidates, but none of them have fulfilled expectations. Therefore, combinations of key antigens from different stages of the parasites life cycle may be essential for the development of efficacious malaria vaccines. Following the identification of promising antigens using bioinformatics, proteomics, and/or immunological approaches, it is necessary to express, purify, and characterize these proteins and explore the potential of fusion constructs combining different antigens or antigen domains before committing to expensive and time-consuming clinical development. Here, using malaria vaccine candidates as an example, we describe how Agrobacterium tumefaciens-based transient expression in plants can be combined with a modular and flexible cloning strategy as a robust and versatile tool for the rapid production of candidate antigens during research and development.

Fabrication of microoptical freeform arrays on wafer level for imaging applications

Miniaturized imaging systems combining an ultra-compact form factor in combination with the ability of refocusing and depth imaging have gained much interest in the field of mobile imaging. Therefore, artificial compound eye cameras are an extremely promising approach for the realization of compact monolithic camera modules on wafer level. Up to now, their imaging performance was limited to low resolution in the range of VGA format according to fabrication constrains given by the established microoptical fabrication methods, namely the reflow of photoresist. In order to overcome these classical limitations, the use of refractive freeform arrays (RFFA) instead of conventional microlens arrays is inevitable. To enable high volume and cost efficient mass production of artificial compound eye cameras for mass markets like the consumer electronics industry, their fabrication on wafer level is essential, but has not been published up to now. We present a wafer level based process chain enabling the fabrication of these elements for the first time.

Plant expression and characterization of the transmission-blocking vaccine candidate PfGAP50

BACKGROUND

Despite the limited success after decades of intensive research and development efforts, vaccination still represents the most promising strategy to significantly reduce the disease burden in malaria endemic regions. Besides the ultimate goal of inducing sterile protection in vaccinated individuals, the prevention of transmission by so-called transmission blocking vaccines (TBVs) is being regarded as an important feature of an efficient malaria eradication strategy. Recently, Plasmodium falciparum GAP50 (PfGAP50), a 44.6 kDa transmembrane protein that forms an essential part of the invasion machinery (glideosome) multi-protein complex, has been proposed as novel potential transmission-blocking candidate. Plant-based expression systems combine the advantages of eukaryotic expression with a up-scaling potential and a good product safety profile suitable for vaccine production. In this study we investigated the feasibility to use the transient plant expression to produce PfGAP50 suitable for the induction of parasite specific inhibitory antibodies.

RESULTS

We performed the transient expression of recombinant PfGAP50 in Nicotiana benthamiana leaves using endoplasmatic reticulum (ER) and plastid targeting. After IMAC-purification the protein yield and integrity was investigated by SDS-PAGE and Western Blot. Rabbit immune IgG derived by the immunization with the plastid-targeted variant of PfGAP50 was analyzed by immune fluorescence assay (IFA) and zygote inhibition assay (ZIA). PfGAP50 could be produced in both subcellular compartments at different yields IMAC (Immobilized Metal Affinity Chromatography) purification from extract yielded up to 4.1 μg/g recombinant protein per fresh leaf material for ER-retarded and16.2 μg/g recombinant protein per fresh leave material for plasmid targeted PfGAP50, respectively. IgG from rabbit sera generated by immunization with the recombinant protein specifically recognized different parasite stages in immunofluorescence assay. Furthermore up to 55 % inhibition in an in vitro zygote inhibition assay could be achieved using PfGAP50-specific rabbit immune IgG.

CONCLUSIONS

The results of this study demonstrate that the plant-produced PfGAP50 is functional regarding the presentation of inhibitory epitopes and could be considered as component of a transmission-blocking malaria vaccine formulation.

SrGAP2-Dependent Integration of Membrane Geometry and Slit-Robo-Repulsive Cues Regulates Fibroblast Contact Inhibition of Locomotion

Migrating fibroblasts undergo contact inhibition of locomotion (CIL), a process that was discovered five decades ago and still is not fully understood at the molecular level. We identify the Slit2-Robo4-srGAP2 signaling network as a key regulator of CIL in fibroblasts. CIL involves highly dynamic contact protrusions with a specialized actin cytoskeleton that stochastically explore cell-cell overlaps between colliding fibroblasts. A membrane curvature-sensing F-BAR domain pre-localizes srGAP2 to protruding edges and terminates their extension phase in response to cell collision. A FRET-based biosensor reveals that Rac1 activity is focused in a band at the tip of contact protrusions, in contrast to the broad activation gradient in contact-free protrusions. SrGAP2 specifically controls the duration of Rac1 activity in contact protrusions, but not in contact-free protrusions. We propose that srGAP2 integrates cell edge curvature and Slit-Robo-mediated repulsive cues to fine-tune Rac1 activation dynamics in contact protrusions to spatiotemporally coordinate CIL.

Isolation, production and characterization of fully human monoclonal antibodies directed to Plasmodium falciparum MSP10

BACKGROUND

Semi-immunity against the malaria parasite is defined by a protection against clinical episodes of malaria and is partially mediated by a repertoire of inhibitory antibodies directed against the blood stage of Plasmodium falciparum, in particular against surface proteins of merozoites, the invasive form of the parasite. Such antibodies may be used for preventive or therapeutic treatment of P. falciparum malaria. Here, the isolation and characterization of novel human monoclonal antibodies (humAbs) for such applications is described.

METHODS

B lymphocytes had been selected by flow cytometry for specificity against merozoite surface proteins, including the merozoite surface protein 10 (MSP10). After Epstein-Barr virus (EBV) transformation and identification of promising resulting lymphoblastoid cell lines (LCLs), human immunoglobulin heavy and light chain variable regions (Vh or Vl regions) were secured, cloned into plant expression vectors and transiently produced in Nicotiana benthamiana in the context of human full-size IgG1:κ. The specificity and the affinity of the generated antibodies were assessed by ELISA, dotblot and surface plasmon resonance (SPR) spectroscopy. The growth inhibitory activity was evaluated based on growth inhibition assays (GIAs) using the parasite strain 3D7A.

RESULTS

Supernatants from two LCLs, 5E8 and 5F6, showed reactivity against the second (5E8) or first (5F6) epidermal growth factor (EGF)-like domain of MSP10. The isolated V regions were recombinantly expressed in their natural pairing as well as in combination with each other. The resulting recombinant humAbs showed affinities of 9.27 × 10(-7) M [humAb10.1 (H5F6:κ5E8)], 5.46 × 10(-9) M [humAb10.2 (H5F6:κ5F6)] and 4.34 × 10(-9) M [humAb10.3 (H5E8:κ5E8)]. In GIAs, these antibodies exhibited EC50 values of 4.1 mg/ml [95% confidence interval (CI) 2.6-6.6 mg/ml], 6.9 mg/ml (CI 5.5-8.6 mg/ml) and 9.5 mg/ml (CI 5.5-16.4 mg/ml), respectively.

CONCLUSION

This report describes a platform for the isolation of human antibodies from semi-immune blood donors by EBV transformation and their subsequent characterization after transient expression in plants. To our knowledge, the presented antibodies are the first humAbs directed against P. falciparum MSP10 to be described. They recognize the EGF-like folds of MSP10 and bind these with high affinity. Moreover, these antibodies inhibit P. falciparum 3D7A growth in vitro.

Analysis of a Multi-component Multi-stage Malaria Vaccine Candidate--Tackling the Cocktail Challenge

Combining key antigens from the different stages of the P. falciparum life cycle in the context of a multi-stage-specific cocktail offers a promising approach towards the development of a malaria vaccine ideally capable of preventing initial infection, the clinical manifestation as well as the transmission of the disease. To investigate the potential of such an approach we combined proteins and domains (11 in total) from the pre-erythrocytic, blood and sexual stages of P. falciparum into a cocktail of four different components recombinantly produced in plants. After immunization of rabbits we determined the domain-specific antibody titers as well as component-specific antibody concentrations and correlated them with stage specific in vitro efficacy. Using purified rabbit immune IgG we observed strong inhibition in functional in vitro assays addressing the pre-erythrocytic (up to 80%), blood (up to 90%) and sexual parasite stages (100%). Based on the component-specific antibody concentrations we calculated the IC₅₀ values for the pre-erythrocytic stage (17–25 μg/ml), the blood stage (40–60 μg/ml) and the sexual stage (1.75 μg/ml). While the results underline the feasibility of a multi-stage vaccine cocktail, the analysis of component-specific efficacy indicates significant differences in IC₅₀ requirements for stage-specific antibody concentrations providing valuable insights into this complex scenario and will thereby improve future approaches towards malaria vaccine cocktail development regarding the selection of suitable antigens and the ratios of components, to fine tune overall and stage-specific efficacy.

Heat-precipitation allows the efficient purification of a functional plant-derived malaria transmission-blocking vaccine candidate fusion protein

Malaria is a vector-borne disease affecting more than two million people and accounting for more than 600,000 deaths each year, especially in developing countries. The most serious form of malaria is caused by Plasmodium falciparum. The complex life cycle of this parasite, involving pre-erythrocytic, asexual and sexual stages, makes vaccine development cumbersome but also offers a broad spectrum of vaccine candidates targeting exactly those stages. Vaccines targeting the sexual stage of P. falciparum are called transmission-blocking vaccines (TBVs). They do not confer protection for the vaccinated individual but aim to reduce or prevent the transmission of the parasite within a population and are therefore regarded as an essential tool in the fight against the disease. Malaria predominantly affects large populations in developing countries, so TBVs need to be produced in large quantities at low cost. Combining the advantages of eukaryotic expression with a virtually unlimited upscaling potential and a good product safety profile, plant-based expression systems represent a suitable alternative for the production of TBVs. We report here the high level (300 μg/g fresh leaf weight (FLW)) transient expression in Nicotiana benthamiana leaves of an effective TBV candidate based on a fusion protein F0 comprising Pfs25 and the C0-domain of Pfs230, and the implementation of a simple and cost-effective heat treatment step for purification that yields intact recombinant protein at >90% purity with a recovery rate of >70%. The immunization of mice clearly showed that antibodies raised against plant-derived F0 completely blocked the formation of oocysts in a malaria transmission-blocking assay (TBA) making F0 an interesting TBV candidate or a component of a multi-stage malaria vaccine cocktail.

The stage-specific in vitro efficacy of a malaria antigen cocktail provides valuable insights into the development of effective multi-stage vaccines

Multicomponent vaccines targeting different stages of Plasmodium falciparum represent a promising, holistic concept towards better malaria vaccines. Additionally, an effective vaccine candidate should demonstrate cross-strain specificity because many antigens are polymorphic, which can reduce vaccine efficacy. A cocktail of recombinant fusion proteins (VAMAX-Mix) featuring three diversity-covering variants of the blood-stage antigen PfAMA1, each combined with the conserved sexual-stage antigen Pfs25 and one of the pre-erythrocytic-stage antigens PfCSP_TSR or PfCelTOS, or the additional blood-stage antigen PfMSP1_19, was produced in Pichia pastoris and used to immunize rabbits. The immune sera and purified IgG were used to perform various assays determining antigen specific titers and in vitro efficacy against different parasite stages and strains. In functional in vitro assays we observed robust inhibition of blood-stage (up to 90%), and sexual-stage parasites (up to 100%) and biased inhibition of pre-erythrocytic parasites (0-40%). Cross-strain blood-stage efficacy was observed in erythrocyte invasion assays using four different P. falciparum strains. The quantification of antigen-specific IgGs allowed the determination of specific IC50 values. The significant difference in antigen-specific IC50 requirements, the direct correlation between antigen-specific IgG and the relative quantitative representation of antigens within the cocktail, provide valuable implementations for future multi-stage, multi-component vaccine designs.

Efficient transduction and optogenetic stimulation of retinal bipolar cells by a synthetic adeno-associated virus capsid and promoter

In this report, we describe the development of a modified adeno-associated virus (AAV) capsid and promoter for transduction of retinal ON-bipolar cells. The bipolar cells, which are post-synaptic to the photoreceptors, are important retinal targets for both basic and preclinical research. In particular, a therapeutic strategy under investigation for advanced forms of blindness involves using optogenetic molecules to render ON-bipolar cells light-sensitive. Currently, delivery of adequate levels of gene expression is a limiting step for this approach. The synthetic AAV capsid and promoter described here achieves high level of optogenetic transgene expression in ON-bipolar cells. This evokes high-frequency (∼100 Hz) spiking responses in ganglion cells of previously blind, rd1, mice. Our vector is a promising vehicle for further development toward potential clinical use.

Prolonged TSH receptor A subunit immunization of female mice leads to a long-term model of Graves' disease, tachycardia, and cardiac hypertrophy

A transient model for human Graves' disease was successfully established in mice using up to 3 immunizations with recombinant adenovirus expressing the extracellular A-subunit of the human TSH receptor (TSHR) (Ad-TSHR). We studied extension of adenovirally induced TSHR A-subunit immunization in mice by using a novel protocol of long-term 3- and 4-weekly injections. Generation of TSHR binding stimulatory antibodies (capacity to stimulate cAMP activity in TSHR-expressing test cells), goiter, and histological thyroid alterations were maintained for at least 9 months in all Ad-TSHR-immunized mice. In response to injection of 10(10) plaque-forming units of Ad-TSHR, also elevated mean serum T4 levels were observed throughout the study. Moreover, cardiac organ involvement (tachycardia and hypertrophy) were consistently observed in these mice. Higher doses of Ad-TSHR (10(11) plaque-forming units) did not produce consistent elevation of T4 and were not associated with a clear increase in heart rate vs controls, probably because these high doses provoked an immune response-induced tachycardia on their own. In summary, a long-term model of Graves' disease induced by a relatively simple protocol of continuing monthly immunizations should allow to investigate long-term disease mechanisms and may possibly obviate the need for more complicated disease models. Moreover, the clinical outcome predictor of tachycardia and cardiac involvement was reliably detected in the model.

Fast track antibody V-gene rescue, recombinant expression in plants and characterization of a PfMSP4-specific antibody

BACKGROUND

Monoclonal antibodies (mAbs) are essential tools in biological research, diagnosis and therapy, and are conventionally produced in murine hybridoma cell lines. Professional applications of mAbs depend on the steady supply of material. Because hybridoma cultures can stop producing the antibody or even die, preservation of the unique epitope specificity of mAbs by rescue of the sequences encoding the antibody variable domains (V regions) is important. The availability of these sequences enables not only the recombinant expression of the original antibody for further applications, but opens the road for antibody engineering towards innovative diagnostic or therapeutic applications. A time- and cost-efficient production system enabling the detailed analysis of the antibodies is an essential requirement in this context.

METHODS

Sequences were rescued from three hybridoma cell lines, subjected to sequence analysis, subcloned into binary expression vectors and recombinantly expressed as chimeric mAb (constant regions of human IgG1:k1) in Nicotiana benthamiana plants. The properties of the recombinant and the murine mAbs were compared using competition enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR) spectroscopy. The recognition of native PfMSP4 by the recombinant mAb was analysed by immunofluorescence staining of Pf 3D7A schizonts and by western blot analysis of merozoite extract.

RESULTS

The rescued sequences of all three hybridoma cell lines were identical. The recombinant mAb was successfully expressed as IgG in plants at moderate levels (45 mg/kg fresh leaf weight). Preservation of the original epitope was demonstrated in a competition ELISA, using recombinant mAb and the three murine mAbs. EGF_PfMSP4-specific affinities were determined by SPR spectroscopy to 8 nM and 10 nM for the murine or recombinant mAb, respectively. Binding to parasite PfMSP4 was confirmed in an immunofluorescence assay showing a characteristic staining pattern and by western blot analysis using merozoite extract.

CONCLUSIONS

As demonstrated by the example of an EGF_PfMSP4-specific antibody, the described combination of a simple and efficient hybridoma antibody cloning approach with the flexible, robust and cost-efficient transient expression system suitable to rapidly produce mg-amounts of functional recombinant antibodies provides an attractive method for the generation of mAbs and their derivatives as research tool, novel therapeutics or diagnostics.

Detailed functional characterization of glycosylated and nonglycosylated variants of malaria vaccine candidate PfAMA1 produced in Nicotiana benthamiana and analysis of growth inhibitory responses in rabbits

One of the most promising malaria vaccine candidate antigens is the Plasmodium falciparum apical membrane antigen 1 (PfAMA1). Several studies have shown that this blood-stage antigen can induce strong parasite growth inhibitory antibody responses. PfAMA1 contains up to six recognition sites for N-linked glycosylation, a post-translational modification that is absent in P. falciparum. To prevent any potential negative impact of N-glycosylation, the recognition sites have been knocked out in most PfAMA1 variants expressed in eukaryotic hosts. However, N-linked glycosylation may increase efficacy by improving immunogenicity and/or focusing the response towards relevant epitopes by glycan masking. We describe the production of glycosylated and nonglycosylated PfAMA1 in Nicotiana benthamiana and its detailed characterization in terms of yield, integrity and protective efficacy. Both PfAMA1 variants accumulated to high levels (>510 μg/g fresh leaf weight) after transient expression, and high-mannose-type N-glycans were confirmed for the glycosylated variant. No significant differences between the N. benthamiana and Pichia pastoris PfAMA1 variants were detected in conformation-sensitive ligand-binding studies. Specific titres of >2 × 10(6) were induced in rabbits, and strong reactivity with P. falciparum schizonts was observed in immunofluorescence assays, as well as up to 100% parasite growth inhibition for both variants, with IC₅₀ values of ~35 μg/mL. Competition assays indicated that a number of epitopes were shielded from immune recognition by N-glycans, warranting further studies to determine how glycosylation can be used for the directed targeting of immune responses. These results highlight the potential of plant transient expression systems as a production platform for vaccine candidates.

Application of a Scalable Plant Transient Gene Expression Platform for Malaria Vaccine Development

Despite decades of intensive research efforts there is currently no vaccine that provides sustained sterile immunity against malaria. In this context, a large number of targets from the different stages of the Plasmodium falciparum life cycle have been evaluated as vaccine candidates. None of these candidates has fulfilled expectations, and as long as we lack a single target that induces strain-transcending protective immune responses, combining key antigens from different life cycle stages seems to be the most promising route toward the development of efficacious malaria vaccines. After the identification of potential targets using approaches such as omics-based technology and reverse immunology, the rapid expression, purification, and characterization of these proteins, as well as the generation and analysis of fusion constructs combining different promising antigens or antigen domains before committing to expensive and time consuming clinical development, represents one of the bottlenecks in the vaccine development pipeline. The production of recombinant proteins by transient gene expression in plants is a robust and versatile alternative to cell-based microbial and eukaryotic production platforms. The transfection of plant tissues and/or whole plants using Agrobacterium tumefaciens offers a low technical entry barrier, low costs, and a high degree of flexibility embedded within a rapid and scalable workflow. Recombinant proteins can easily be targeted to different subcellular compartments according to their physicochemical requirements, including post-translational modifications, to ensure optimal yields of high quality product, and to support simple and economical downstream processing. Here, we demonstrate the use of a plant transient expression platform based on transfection with A. tumefaciens as essential component of a malaria vaccine development workflow involving screens for expression, solubility, and stability using fluorescent fusion proteins. Our results have been implemented for the evidence-based iterative design and expression of vaccine candidates combining suitable P. falciparum antigen domains. The antigens were also produced, purified, and characterized in further studies by taking advantage of the scalability of this platform.

Optimization of a multi-stage, multi-subunit malaria vaccine candidate for the production in Pichia pastoris by the identification and removal of protease cleavage sites

We demonstrated the successful optimization of a recombinant multi-subunit malaria vaccine candidate protein for production in the methylotrophic yeast Pichia pastoris by the identification and subsequent removal of two protease cleavage sites. After observing protein degradation in the culture supernatant of a fed-batch fermentation, the predominant proteolytic fragment of the secreted recombinant protein was analyzed by mass spectrometry. The MS data indicated the cleavage of an amino acid sequence matching the yeast KEX2-protease consensus motif EKRE. The cleavage in this region was completely abolished by the deletion of the EKRE motif in a modified variant. This modified variant was produced, purified, and used for immunization of rabbits, inducing high antigen specific antibody titers (2 × 10(6) ). Total IgG from rabbit immune sera recognized different stages of Plasmodium falciparum parasites in immunofluorescence assays, indicating native folding of the vaccine candidate. However, the modified variant was still degraded, albeit into different fragments. Further analysis by mass spectrometry and N-terminal sequencing revealed a second cleavage site downstream of the motif PEVK. We therefore removed a 17-amino-acid stretch including the PEVK motif, resulting in the subsequent production of the full-length recombinant vaccine candidate protein without significant degradation, with a yield of 53 mg per liter culture volume. We clearly demonstrate that the proteolytic degradation of recombinant proteins by endogenous P. pastoris proteases can be prevented by the identification and removal of such cleavage sites. This strategy is particularly relevant for the production of recombinant subunit vaccines, where product yield and stability play a more important role than for the production of a stringently-defined native sequence which is necessary for most therapeutic molecules.

Malaria vaccine candidate antigen targeting the pre-erythrocytic stage of Plasmodium falciparum produced at high level in plants

Plants have emerged as low-cost production platforms suitable for vaccines targeting poverty-related diseases. Besides functional efficacy, the stability, yield, and purification process determine the production costs of a vaccine and thereby the feasibility of plant-based production. We describe high-level plant production and functional characterization of a malaria vaccine candidate targeting the pre-erythrocytic stage of Plasmodium falciparum. CCT, a fusion protein composed of three sporozoite antigens (P. falciparum cell traversal protein for ookinetes and sporozoites [PfCelTOS], P. falciparum circumsporozoite protein [PfCSP], and P. falciparum thrombospondin-related adhesive protein [PfTRAP]), was transiently expressed by agroinfiltration in Nicotiana benthamiana leaves, accumulated to levels up to 2 mg/g fresh leaf weight (FLW), was thermostable up to 80°C and could be purified to >95% using a simple two-step procedure. Reactivity of sera from malaria semi-immune donors indicated the immunogenic conformation of the purified fusion protein consisting of PfCelTOS, PfCSP_TSR, PfTRAP_TSR domains (CCT) protein. Total IgG from the CCT-specific mouse immune sera specifically recognized P. falciparum sporozoites in immunofluorescence assays and induced up to 35% inhibition in hepatocyte invasion assays. Featuring domains from three promising sporozoite antigens with different roles (attachment and cell traversal) in the hepatocyte invasion process, CCT has the potential to elicit broader immune responses against the pre-erythrocytic stage of P. falciparum and represents an interesting new candidate, also as a component of multi-stage, multi-subunit malaria vaccine cocktails.

High-throughput quantification of stabilizers in polymeric materials by flow injection tandem mass spectrometry

RATIONALE

High-throughput methods for identification and quantification of stabilizers in plastic materials are of significant importance in order to evaluate the suitability of materials of unknown origin for specific application areas, to clarify reasons for failure of materials, or for comparison of materials from different sources.

METHODS

In the present study, a highly sensitive and rapid flow injection method coupled to selected reaction monitoring mass spectrometry (MS) for comprehensive analysis of 21 polymer stabilizers in polyolefins is demonstrated. A critical factor for this approach is the choice of ionization mode, as no separation was performed prior to MS detection. Differences between several ionization techniques regarding matrix effects are reported.

RESULTS

Atmospheric pressure chemical ionization was found to be the most suitable ionization technique, with no significant matrix effects observed. The developed method has a linear dynamic range over two to three orders of magnitude with correlation coefficients better than 0.99 for all studied analytes. Following a multistep sample preparation protocol, the method allowed quantification down to minimum values of between 0.0001 and 0.04 wt% depending on the type of stabilizer. Results were compared to an established chromatographic approach and showed very good correlation (bias below 7.5%).

CONCLUSIONS

The applicability of the optimized method could be demonstrated for both the qualitative and quantitative determination of polymer stabilizers in polyolefins. Furthermore, the described approach yields a complete analysis in a much shorter time than can be achieved with commonly applied chromatographic methods.

Plant-based production of recombinant Plasmodium surface protein pf38 and evaluation of its potential as a vaccine candidate

Pf38 is a surface protein of the malarial parasite Plasmodium falciparum. In this study, we produced and purified recombinant Pf38 and a fusion protein composed of red fluorescent protein and Pf38 (RFP-Pf38) using a transient expression system in the plant Nicotiana benthamiana. To our knowledge, this is the first description of the production of recombinant Pf38. To verify the quality of the recombinant Pf38, plasma from semi-immune African donors was used to confirm specific binding to Pf38. ELISA measurements revealed that immune responses to Pf38 in this African subset were comparable to reactivities to AMA-1 and MSP119. Pf38 and RFP-Pf38 were successfully used to immunise mice, although titres from these mice were low (on average 1∶11.000 and 1∶39.000, respectively). In immune fluorescence assays, the purified IgG fraction from the sera of immunised mice recognised Pf38 on the surface of schizonts, gametocytes, macrogametes and zygotes, but not sporozoites. Growth inhibition assays using αPf38 antibodies demonstrated strong inhibition (≥60%) of the growth of blood-stage P. falciparum. The development of zygotes was also effectively inhibited by αPf38 antibodies, as determined by the zygote development assay. Collectively, these results suggest that Pf38 is an interesting candidate for the development of a malaria vaccine.

A versatile toolkit to produce sensitive FRET biosensors to visualize signaling in time and space

Genetically encoded, ratiometric biosensors based on fluorescence resonance energy transfer (FRET) are powerful tools to study the spatiotemporal dynamics of cell signaling. However, many biosensors lack sensitivity. We present a biosensor library that contains circularly permutated mutants for both the donor and acceptor fluorophores, which alter the orientation of the dipoles and thus better accommodate structural constraints imposed by different signaling molecules while maintaining FRET efficiency. Our strategy improved the brightness and dynamic range of preexisting RhoA and extracellular signal-regulated protein kinase (ERK) biosensors. Using the improved RhoA biosensor, we found micrometer-sized zones of RhoA activity at the tip of F-actin bundles in growth cone filopodia during neurite extension, whereas RhoA was globally activated throughout collapsing growth cones. RhoA was also activated in filopodia and protruding membranes at the leading edge of motile fibroblasts. Using the improved ERK biosensor, we simultaneously measured ERK activation dynamics in multiple cells using low-magnification microscopy and performed in vivo FRET imaging in zebrafish. Thus, we provide a construction toolkit consisting of a vector set, which enables facile generation of sensitive biosensors.

Distinct cell-specific expression of homospermidine synthase involved in pyrrolizidine alkaloid biosynthesis in three species of the boraginales

Homospermidine synthase (HSS) is the first specific enzyme in pyrrolizidine alkaloid (PA) biosynthesis, a pathway involved in the plant's chemical defense. HSS has been shown to be recruited repeatedly by duplication of a gene involved in primary metabolism. Within the lineage of the Boraginales, only one gene duplication event gave rise to HSS. Here, we demonstrate that the tissue-specific expression of HSS in three boraginaceous species, Heliotropium indicum, Symphytum officinale, and Cynoglossum officinale, is unique with respect to plant organ, tissue, and cell type. Within H. indicum, HSS is expressed exclusively in nonspecialized cells of the lower epidermis of young leaves and shoots. In S. officinale, HSS expression has been detected in the cells of the root endodermis and in leaves directly underneath developing inflorescences. In young roots of C. officinale, HSS is detected only in cells of the endodermis, but in a later developmental stage, additionally in the pericycle. The individual expression patterns are compared with those within the Senecioneae lineage (Asteraceae), where HSS expression is reproducibly found in specific cells of the endodermis and the adjacent cortex parenchyma of the roots. The individual expression patterns within the Boraginales species are discussed as being a requirement for the successful recruitment of HSS after gene duplication. The diversity of HSS expression within this lineage adds a further facet to the already diverse patterns of expression that have been observed for HSS in other PA-producing plant lineages, making this PA-specific enzyme one of the most diverse expressed proteins described in the literature.

Resource usage in outpatient care and reimbursement for cystic fibrosis in Germany

OBJECTIVE

Objective of this study is to assess and evaluate resource use in outpatient treatment in Germany and to compare it with remuneration.

METHODS

Outpatient treatment was evaluated in seven different centers for pediatric and adult CF patients. Data were recorded during one representative month in 2006. A micro-costing approach was used to value resource use data.

RESULTS

For outpatient treatment mean costs (excluding drugs) of 488 € per patient per quarter occurred. Correlation analyses identified significant cost drivers including age and co-morbidities (pancreatic insufficiency, hepatobiliary complications, lung function capacity, or bacterial lung colonization). Remuneration covered only 51% of the total costs (252 € per patient/quarter).

CONCLUSIONS

As the human resources available to these centers today are already below the requirements set by the European consensus for standards of CF care it will be important for a high level of patient care to reach a cost-covering remuneration scheme.