Typisierung beim HLA-Matching

Matching of human leukocyte antigens of donors and recipients (HLA matching) plays a significant role in kidney, heart, lung, and stem cell transplantation. New data demonstrate that HLA matching also significantly prolongs the survival of corneal grafts. The reasons for the late recognition of the significance of HLA matching in corneal transplantation are on the one hand the immune privilege of the eye, which allows corneal transplantation under certain conditions without immunosuppressive therapy, and on the other hand highly erroneous serological typing. Recent molecular DNA typing is almost without errors, and the selection of grafts on the basis of results obtained using this method will improve the long-time survival of future corneal grafts. Today, there are several reasons arguing for the general practice of HLA matching in keratoplasty.

[Incidence of hip fracture in Germany--person-related analysis of health insurance population]

BACKGROUND AND PURPOSE

An increasing number of hip fractures were reported world wide during the last decades. Up to now incidence data are rare for Germany. The aim of this study is to determine actual person-related age- and sex-specific rates of hip fractures in Germany.

METHODS

The linkable and person-specific but non-identifying database of a German statutory health insurance company, Gmuender ErsatzKasse (GEK), was used. All subjects who were admitted to hospital with a primary diagnosis of hip fracture (ICD-10: S72.0-S72.2) in 2004 were identified. Incidence rate ratios (IRR), age- and sex-specific rates (per 1000 person-years) were calculated. Annual numbers of hip fractures for all persons covered by statutory health insurances (Gesetzliche Krankenversicherung- GKV) and the German population were estimated.

RESULTS

The incidence of hip fracture increases exponentially with age. Hip fractures occur 129 times more often (IRR: 129.07; 95 % CI: 66.55 - 269.78) in women aged 90 - 94 years and 79 times more often (IRR: 78.97; 95 % CI: 30.02 - 185.87) in men aged 90 - 94 years compared to those aged 50 - 54 years. Approximately 101 037 (95 % CI: 91 779 - 110 294) persons are annually admitted to hospital in Germany due to this event.

CONCLUSION

Hip fractures are common in the elderly and especially in women. Because of demographic changes and a possible secular trend an increasing number of hip fractures are to be expected in the future.

Multicenter-study of operative treatment of intraligamentous tears of the anterior cruciate ligament in children and adolescents: comparison of four different techniques

Tears of the anterior cruciate ligament in skeletally immature patients were operated with four different methods and their outcome compared to each other. Sixty-eight patients (33 males, 35 females), mean 12.5 years, were treated in four different centers from 1984 to 2001. Twenty-eight patients underwent the ACL-reconstruction with hamstring grafts, 16 patients with bone-patella-bone autografts, 12 patients with quadriceps grafts and 12 patients with facia lata. The mean follow-up was 32 months. Postoperative evaluation included radiographs, KT-1000/2000 stability measurements, Lysholm score, The Tegner activity scale and IKDC score. Neither leg length discrepancy nor angular deformities were noted. Mean KT-1000 difference was 2.1 mm, mean postoperative Lysholm knee score 93.3, IKDC 87% normal or nearly normal. The Tegner index decreased from 6.6 to 5.7. In total, six patients developed instability due to an adequate trauma 1 year after the index operation. Two patients showed mild arthrotic changes. All but two patients were able to return to the same level of preoperative sports participation. None of the four methods studied showed major differences in outcome compared to the other. No growth disturbance could be noted.

Bendamustine in combination with thalidomide and prednisolone (BPT) in patients with refractory or relapsed multiple myeloma: Results of a phase I clinical trial

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Background: Thalidomide is an active single agent in advanced relapsed or refractory multiple myeloma (MM). Combination of low dose thalidomide with bendamustine and prednisolone might be a way to maintain efficacy of the drug without dose limiting toxicity (DLT). Methods: The treatment consists of a fixed dose of bendamustine (60mg/qm) day 1, 8, and 15 and prednisolone (100 mg) day 1, 8, 15, and 22. At the same time, thalidomide was given in patients cohorts with escalating doses, starting with 50 mg to a maximum of 200 mg daily. 8 patients (4 after conventional chemotherapy and 4 after APBSCT) were enrolled at each dose level. Cycles were repeated every 28 days for a minimum of 2 and a maximum of 10 cycles until a maximal response was achieved, a DLT or a disease progression were observed. 23 patients ( 8 in the first dose level with 50 mg thalidomide, 8 in the second dose level with 100 mg and 7 patients in the third dose level with 200 mg) are enrolled until now. The number of prior treatment regimens was 2 or more in all patients. 6 patients were refractory for the last treatment. Median age was 67 years (range: 40 - 78). Results: All patients completed 2 cycles of BPT-treatment and were hence evaluable. Response was assessed using EBMT criteria modified to include near complete remission (nCR) and very good partial remission (VGPR). 20 of 23 patients responded after at least 2 cycles of chemotherapy with 3 CR, 5 VGPR, 11 PR and 2 MR. 2 patients had stable disease. With a median follow up of ten months, EFS and OS at twelfe months were 36 % and 85 %, respectively. Most common site effects were constipation (10 patients WHO grade 1, 8 patients WHO grade 2), polyneuropathy (14 patients WHO grade 1, 2 patients WHO grade 2) and somnolence (4 patients WHO grade 1). None of the 23 patients developed dose-limiting hematoxicity as defined by an ANC < 1,0 Gpt/l for > 7 days or an ANC < 0,5 Gpt/l for > 3 days or platelet count < 25 Gpt/l. Short neutropenia was reported in 8 patients (WHO grade 3 and 4) but no thrombocytopenia was observed. Conclusions: BPT with a dose between 50 and 200 mg thalidomide daily is well tolerated in patients with relapsed or refractory MM.

No significant financial relationships to disclose.

Gelatinase B [matrix metalloproteinase (MMP)-9] and collagenases (MMP-8/-13) are upregulated in cerebrospinal fluid during aseptic and bacterial meningitis in children

We investigated the protein expression of gelatinases [matrix metalloproteinase (MMP)-2 and -9] and collagenases (MMP-8 and -13) in cerebrospinal fluid (CSF) from patients with bacterial (BM, n = 17) and aseptic (AM, n = 14) meningitis. In both, MMP-8 and -9 were increased in 100% of patients, whereas MMP-13 was detectable in 53% and 82% respectively. Three patients with clinical signs of meningitis, without CSF pleocytosis, scored positive for all three MMPs. MMP-8 appeared in two isoforms, granulocyte-type [polymorphonuclear cell (PMN)] and fibroblast/macrophage (F/M) MMP-8. Analysis of kinetic changes from serial lumbar punctures showed that these MMPs are independently regulated, and correlate only partly with CSF cytosis or levels of the endogenous inhibitor, tissue inhibitor of matrix metalloproteinase-1. In vitro, T cells, peripheral blood mononuclear cells (PBMCs) and granulocytes (PMN) release MMP-8 and -9, whereas MMP-13 could be found only in the former two cell types. Using models of exogenous (n-formyl-Met-Leu-Phe, T cell receptor cross-linking) and host-derived stimuli (interleukin-2), the kinetics and the release of the MMP-8, -9 and -13 showed strong variation between these immune cells and suggest release from preformed stocks. In addition, MMP-9 is also synthesized de novo in PBMCs and T cells. In conclusion, invading immune cells contribute only partially to MMPs in CSF during meningitis, and parenchymal cells are an equally relevant source. In this context, in patients with clinical signs of meningitis, but without CSF pleocytosis, MMPs seem to be a highly sensitive marker for intrathecal inflammation. The present data support the concept that broad-spectrum enzyme inhibition targeting gelatinases and collagenases is a potential strategy for adjunctive therapy in infectious meningitis.

Posttraumatic anterior-inferior instability of the shoulder: arthroscopic findings and clinical correlations

INTRODUCTION

The main purpose of our study was to evaluate intra-articular lesions in glenohumeral-instability with arthroscopy and correlate them with clinical findings as well as history of instability.

MATERIAL AND METHODS

In this prospective multi-centre study, we evaluated arthroscopic findings in 303 patients with posttraumatic anterior-inferior instability of the shoulder. The study cohort was divided into 2 groups: patients with a history of one dislocation (Group 1, n=61, 20.1%) and patients with a history of more than one dislocation (Group 2, n=242, 79.9%).

RESULTS

In Group 1, 37 patients had an IGHL-lesion, 31 a MGHL-lesion and 41 a Hill-Sachs lesion. In Group 2, 182 patients had an IGHL-lesion, 172 a MGHL-lesion and 203 a Hill-Sachs lesion. The percentage of lesions in Group 2 (IGHL-75.2%, MGHL-71.1%, Hill-Sachs-83.9%) was significantly higher than in Group 1 (IGHL-60.7%, MGHL-50.8%, Hill-Sachs-67.2%, P=0.0233, P=0.0026, and P=0.0033, respectively). Within Group 2 we found significantly more Hill-Sachs-lesions with a history of an increasing number of recurrences (P=0.0436). We also found an increase of IGHL- and MGHL-lesions with an increasing number of recurrences, but this difference was not significant. The distribution of lesion types of the anterior labrum-ligament complex showed no significant difference between the two groups, apart from a higher incidence of ALPSA-lesions within Group 2 (34.7% versus 18.0% in Group 1). The results of this study show that recurrences after primary posttraumatic anterior-inferior shoulder dislocation cause increasing ligamental damage as well as increasing Hill-Sachs lesions within the gleno-humeral joint.

CONCLUSION

Thus we conclude that early surgical stabilization after posttraumatic anterior-inferior shoulder dislocation is necessary to prevent increasing damage within the shoulder joint.

Neugebrauch von Benzodiazepinen und das Risiko einer proximalen Femurfraktur

Benzodiazepines appear to increase the incidence of hip fractures. Their role as a time-dependent risk factor remains unclear. We therefore conducted a case-crossover study to determine whether the new use of benzodiazepines is associated with a rise in hip fractures. We analysed 49 months of the statutory health insurance Gmünder Ersatzkasse (GEK) and enrolled all first hip fractures. The index date was the day of hospital admission. Exposure to new use of benzodiazepines was compared within the five periods preceding the index date. Out of 1630 subjects, 223 (13.7%) had at least one prescription of benzodiazepines in the preceding 150 days before the index date, 74 (4.5%) of them as a first prescription. The average age of the population was 79.8 years (SD: 7.7). Odds ratio (OR) of hip fracture was highest during the initial 5 days of new use (OR: 3.43; 95% CI 1.15-10.20) and then declined to a non-significant OR of 1.59 (95% CI 0.96-2.63) after 30 days. In conclusion, the start of a new benzodiazepine is associated with an increased risk of hip fractures. However, the population attributable risk (PAR) and, therefore, the percentage of preventable events is small (PAR: 0.55%; 95% CI 0.05-1.06%).

No Indication for a Defect in Toll-Like Receptor Signaling in Patients with Hyper-IgE Syndrome

Hyper-IgE syndrome is a rare primary immunodeficiency of unknown etiology characterized by recurrent infections of the skin and respiratory system, chronic eczema, elevated total serum IgE, and a variety of associated skeletal symptoms. Recent reports about susceptibility to pyogenic bacterial infections and high IgE levels in patients and animals with defects in toll-like receptor (TLR) signaling pathways prompted us to search for TLR signaling defects as an underlying cause of hyper-IgE syndrome. Blood samples from six patients with hyper-IgE syndrome were analyzed for serum cytokine levels, intracellular cytokine production in T cells after stimulation with PMA/ionomycin, and cytokine production from peripheral blood mononuclear cells stimulated by TLR ligands and bacterial products including LPS (TLR4), peptidoglycan (TLR2), PolyIC (TLR3), R848 (TLR7/8), CpG-A, and CpG-B (TLR9), zymosan and heat killed Listeria monocytogenes. All results were compared to data from healthy controls. A reduction in IFN-gamma, IL-2, and TNF-alpha producing T cells after PMA stimulation suggested a reduced inflammatory T cell response in patients with hyper-IgE syndrome. Increased serum levels of IL-5 indicated a concomitant Th2 shift. However, normal production of cytokines (TNF-alpha, IL-6, IL-10, IFN-alpha, IP-10) and upregulation of CD86 on B cells and monocytes after TLR stimulation made a defect in TLR signaling pathways highly unlikely. In summary, our data confirmed an imbalance in T cell responses of patients with hyper-IgE syndrome as previously described but showed no indication for an underlying defect in toll-like receptor signaling.

Histological investigation of organisms with hard skeletons: a case study of siliceous sponges

Siliceous and calcareous sponges commonly are treated with acid to remove the spicules prior to embedding and cutting for histological investigations. Histology of spiculated sponge tissue represents a challenging problem in sponge histotechnology. Furthermore, fluorescence in situ hybridization (FISH), a key method for studying sponge-associated microbes, is not possible after acid treatment. For a broad range of siliceous sponge species, we developed and evaluated methods for embedding in paraffin, methylmethacrylate resins, LR White resin and cryomatrix. Different methods for cutting tissue blocks as well as mounting and staining sections also were tested. Our aim was to enable histological investigations and FISH without prior removal of the spicules. To obtain an overview of tissue and skeleton arrangement, we recommend embedding tissue blocks with LR White resin combined with en bloc staining techniques for large specimens with thick and numerous spicules, but paraffin embedding and subsequent staining for whole small specimens. For FISH on siliceous sponges, we recommend Histocryl embedding if the spicule content is high, but paraffin embedding if it is low. Classical histological techniques are used for detailed tissue examinations.

Long-term pharmacokinetics of amprenavir in combination with delavirdine in HIV-infected children

Five heavily pretreated HIV-infected children were put on amprenavir and delavirdine plus two nucleoside inhibitors to reverse transcriptase to boost amprenavir levels and to use the antiretroviral activity of a non-nucleoside reverse transcriptase inhibitor. No data are available about this combination in children. It w;as well tolerated, and the median reduction in viral load was 1.5 log after 18 months. Delavirdine boosted amprenavir trough levels more than 10-fold, and delavirdine trough levels remained i several fold above susceptible HIV strains.

Gewebetypisierung bei der perforierenden Keratoplastik

The demand for matched corneal grafts has risen rapidly over the last years. One reason for this is the change in the judgement of the value of tissue and especially HLA typing for prevention of an immune reaction in perforating corneal transplantation. Besides HLA or major antigens, there are other immunologically relevant tissue surface molecules such as the non-MHC antigens of which blood groups and minor antigens are the most important. With regard to effective cost-benefit and waiting time-benefit analyses, differentiated matching strategies are needed to assure optimized utilization and allocation of the still unsatisfactory number of available corneal grafts. With special matching strategies, such as the calculation of the individual waiting time, the consideration of split, non-MHC and HLA antigens, additional HLA loci as well as so-called "permissible" and "taboo" mismatches, much more has to be taken into account in the future than just the numerical correspondence of HLA antigens. This will make it possible to turn from a pure numerical approach to a functional matching strategy. This review summarizes the discussion and different matching strategies, possibilities and limitations of HLA and tissue typing in perforating corneal transplantation.

[Effect of topical dexamethasone treatment on antigen-presenting cells in murine corneas]

OBJECTIVE

To determine the influence of dexamethasone treatment on APCs and the time of graft survival of MHC-disparate grafts.

METHODS

Flatmounts of the ocular surface prepared with EDTA and tangential frozen sections of the remaining corneal stroma from untreated eyes of normal mice (n=6) and from eyes treated for 7 days with dexamethasone ( n=6) were immunohistologically examined for content of F4/80+ and MHC II+ cells.Furthermore, corneas of C(3)H mice without and with 7-day dexamethasone eye drop treatment (n=8) were grafted into BALB/c mice receiving the same treatment.

RESULTS

The number of positive cells within the epithelial flatmounts showed a dramatic reduction in the dexamethasone-pretreated group (p<0.01 compared to the untreated control group). The number of positive cells in the corneal stroma remained unchanged. The grafts of untreated control mice survived 16+/-4 days, the treated grafts 16+/-3 days.

CONCLUSIONS

Most investigators assume that normal murine corneas contain no APCs such as macrophages and Langerhans cells. For the first time we were able to detect APCs in flatmounts of the ocular surface and frozen sections of corneal stroma. Our investigations show that, in contrast to the ocular surface, the number of F4/80+ cells in the corneal stroma is not influenced by dexamethasone treatment. Transplantation of corneas containing donor-derived APCs promotes acute rejection (direct pathway of allorecognition).Thus,dexamethasone treatment did not prolong the time of allograft survival.

Effect of antiretroviral triple combinations including the protease inhibitor nelfinavir in heavily pretreated children with HIV-1 infection

BACKGROUND

In this retrospective study the effect of antiretroviral triple therapy including the protease-inhibitor nelfinavir (NFV) on CD4-cells and viral load (VL) in heavily pretreated HIV-infected children was evaluated.

PATIENTS AND METHODS

20 children (<18 years) were included. Median duration of antiretroviral pretreatment was 27 months (range, 7 65), median initial VL was 4.7 log subset 10 (3.2 6.1) and median relative CD4-cells was 17.5% (3 33). Patients were put on combinations with NFV because of treatment failure (increasing VL), intolerance to prior therapy with PIs or adherence problems with prior indinavir. Viral load (RT-PCR, detection limit 50 copies/ml) and CD4-cells were measured every 4-8 weeks.

RESULTS

Median viral load decreased 1.2 log(10) (-1.3 2.5), 0.9 log(10) (-0.8 - 2.5) and 0.4 log(10) (-0.5 - 3.0) after 12, 24 and 36 weeks. The VL of 2 patients was below the detection limit (50 copies/ml) after 24 weeks. The relative CD4-cell count increased from a median of 17.5% to 22%, 23% and 25% after 12, 24 and 36 weeks, respectively. Side effects of NFV were usually mild. WHO grade 1 or 2 diarrhea occurred in 70% and moderate elevations of triglycerides in 40% of the patients. At 48 weeks 18/20 patients had to be switched to other combinations due to virological failure.

CONCLUSIONS

In children with intensive prior antiretroviral therapy combination therapy including NFV lead to a modest short-term reduction of the VL and increase in CD4-cells. However, the long-term antiretroviral effect was poor.

[Immunomodulation after keratoplasty by CTL4-Ig and anti-CD154 antibodies]

BACKGROUND

The immunoreaction after corneal transplantation is caused by the T cell receptor interacting with the major histocompatibility complex (MHC) receptor of the antigen-presenting cell. The signal is amplified by the CD4 receptor and the costimulatory signal interactions of CD28-B7 and CD40-CD154. We investigated the influence of costimulatory signal blocking on corneal transplant survival in mice.

METHODS

Seven groups of 6 BALB/c mice received an orthotopic corneal transplant from C3H mice differing in minor and major MHC and were postoperatively treated as follows: (1) 80 micrograms of CTLA4 fusion protein intraperitoneally (i.p.) for 6 days; (2) 50 microliters of PBS i.p. for 6 days; (3) 1 mg of Solu-Decortin H i.p. for 5 days + dexamethasone AT 0.1% for 35 days; (4) therapy (3) + 50 micrograms of CTLA4 fusion protein i.p. for 6 days; (5) CTLA4-Ig as in (1) + 15 micrograms of anti-CD154 subconjunctivally (s.c.) on days 0, 2, 4, 6, and 8; (6) CTLA4-Ig as in (1) + 25 micrograms of anti-CD154 s.c. for 9 days; and (7) 25 microliters of PBS s.c. for 9 days.

RESULTS

All animals had an immunoreaction on the following days: (1) day 18 +/- 3.1; (2) day 13.6 +/- 1.6; (3) day 48 +/- 6.6; (4) day 65 +/- 41; (5) day 23.5 +/- 8.5; (6) day 16.2 +/- 3.6; (7) day 13.8 +/- 2.7.

CONCLUSION

The significant prolongation of transplant survival achieved by corticosteroids alone (P < 0.001) is again significantly increased by combining them with CTLA4-Ig (P < 0.001). Specific immunotherapy combined with nonspecific steroid therapy may also improve clinical corneal transplantation results. Compared to the two control groups, CTLA4-Ig and anti-CD154 only influenced transplant survival at a low dosage (P < 0.001).

Effect of antiretroviral combination therapies including efavirenz in heavily pretreated HIV-infected children

BACKGROUND

In this retrospective study the effect of antiretroviral combination regimens including the non nucleoside reverse transcriptase inhibitor (NNRTI) efavirenz (EFV) on viral load (VL) and CD4-cell count in heavily pretreated HIV-infected children was investigated.

DESIGN

The data of 15 children (< 16 years) were evaluated during a treatment period of at least 52 weeks. Patients received a median of 4 prior antiretroviral regimens and were changed to combinations with EFV because of renewed increasing VL.

METHODS

Viral load (Amplicor, detection limit 50 copies/ml) and CD4-cells were measured every 4-8 weeks.

RESULTS

The median reduction of the viral load for the total study population was 1.9 log10 (0.8 - 4.7), 2.3 log(10) (0.5 - 4.7) and 2.6 log(10) (0-4.7) after 12, 24 and 52 weeks, respectively. After 24 weeks 7/15 children and after 52 weeks 9/15 patients had reductions of the VL below the detection limit. The median increase of CD4-cells in the study population during the treatment period were 104 cells/microl (189-969), 220 cells/microl (170-831) and 321 cells/ml (162-574) after 12, 24 and 52 weeks, respectively.

CONCLUSIONS

In children with intensive prior antiretroviral therapy and multiple therapeutic failures with PI-containing regimens, combination therapy including EFV resulted in an excellent antiretroviral efficacy. After 52 weeks 9/15 patients had persistent reductions of the VL below 50 copies/ml, although none of these children reached this level of viral suppression during their multiple prior protease inhibitor-containing regimens.

On-line estimation of the metabolic burden resulting from the synthesis of plasmid-encoded and heat-shock proteins by monitoring respiratory energy generation

Human basic fibroblast growth factor (hFGF-2) was produced in high-cell density cultures of recombinant Escherichia coli using a temperature-inducible expression system. The synthesis rates of proteins were followed by two-dimensional gel electrophoresis of the (35)S-methionine-labeled proteom. After temperature induction of hFGF-2 synthesis, the rate of total protein synthesis per biomass increased by a factor of three, mainly as a result of the additional synthesis of hFGF-2 and heat-shock proteins. The synthesis rates of heat-shock proteins and constitutive plasmid-encoded proteins increased after the temperature upshift also in the control strain without hFGF-2 gene but followed time profiles different from the producing strain. The energy demand for the extra synthesis of plasmid-encoded and heat-shock proteins resulted in an elevated respiratory activity and, consequently, in a reduction of the growth rate and the biomass yield. A procedure was developed to relate the energy demand for the additional synthesis of these proteins to the generation of energy in the respiratory pathway. Specific energy production was estimated based on on-line measurable rates of oxygen consumption, or carbondioxide evolution and growth, respectively. In this way, the metabolic burden resulting from the synthesis of plasmid-encoded and heat-shock proteins was quantified from on-line accessible data.

Contribution of lymphatic drainage system in corneal allograft rejection in mice

PURPOSE

To modulate aqueous outflow via the uveoscleral pathway and to determine its influence on corneal graft survival in mice.

METHODS

BALB/c mice received corneal transplants from C3H mice and were placed randomly in three treatment groups: saline, pilocarpine or latanoprost. Three further groups received adjuvant systemic and topical corticosteroids. The kinetics of infiltrating lymphocytes, neutrophils and macrophages in the transplants was investigated in an additional 96 animals. Cytokine expression in the submandibular lymph nodes and spleen was investigated using in-situ hybridization and RNAse protection assay. Tracer experiments were conducted using 99mTC colloidal albumin Nanocoll; count rates were determined in the submandibular lymph nodes, spleen and blood following both subconjunctival and intracameral injection.

RESULTS

Neither pilocarpine nor latanoprost had any influence on aqueous outflow or allograft survival in mice. Neutrophils and macrophages dominated the infiltrating cells 11 days postoperative in both treated and untreated grafts. On postoperative day 13, a greater increase in lymphocytes than in other cell groups was observed in allogeneic grafts. Following allogeneic transplantation, 1% of lymphocytes in ipsilateral submandibular lymph nodes were positive for IFN-gamma. Tracer studies revealed a 16% aqueous outflow via the uveoscleral routes following intracameral injection of Nanocoll; this was increased by 97% with subconjunctival injection.

CONCLUSION

Our data confirm the existence of functional lymphatic drainage via the uveoscleral pathway and conjunctiva in the mouse. Cells within the ipsilateral submandibular lymph node respond to stimuli upstream. This reaction could potentially be manipulated to improve graft survival.

Engineering regulable Escherichia coli beta-galactosidases as biosensors for anti-HIV antibody detection in human sera

The activity of engineered, peptide-displaying enzymes is modulated by binding to specific anti-peptide antibodies. This new concept of a quantitative antibody detection system allows test kits to be set up for fast diagnosis of infectious diseases. To develop a quick and homogeneous assay for the detection of human immunodeficiency virus (HIV) infection, we have explored two acceptor sites of the bacterial Escherichia coli beta-galactosidase for the accommodation of HIV antigenic peptides. Two overlapping epitopes (namely P1 and P2) from the gp41 envelope glycoprotein, contained in different sized peptides, were inserted in the vicinity of the enzyme active site to generate a set of hybrid, enzymatically active beta-galactosidases. Regulable enzymes of different responsiveness to monoclonal antibody binding were generated with both acceptor sites tested. These biosensors were also sensitive to immune sera from HIV-infected patients. Modeling data provide insight into the structural modifications in the vicinity of the active site induced by peptide insertion that strongly affect the responsiveness of the engineered proteins through different parameters of their catalytic properties.

Zinc mesoporphyrin represses induced hepatic 5-aminolevulinic acid synthase and reduces heme oxygenase activity in a mouse model of acute hepatic porphyria

Zinc mesoporphyrin (ZnMP) is a potent inhibitor of heme oxygenase (HO) and represses 5-aminolevulinic acid synthase (ALAS). These properties make it a potential candidate for treatment of inducible acute hepatic porphyrias, diseases characterized by neurovisceral symptoms, and massive ALAS induction. Effects of intraperitoneal ZnMP (2.5-10 micromol/kg/d) and heme arginate (3-6 mg/kg/d) on plasma levels of 5-aminolevulinic acid (ALA), on messenger RNA (mRNA), and activity of hepatic ALAS and HO were studied in porphobilinogen deaminase-deficient mice treated with phenobarbital (100 mg/kg/d) to induce ALAS. ZnMP (5 micromol/kg/d) led to a significant reduction of plasma ALA levels to 31% of controls (P < .01) by lowering the activity of hepatic mitochondrial and cytosolic ALAS to 29% and 25% of controls, respectively (P < .03). ZnMP decreased the mRNA levels of hepatic ALAS to 53% (P < .03) of controls and this repression was more pronounced than that achieved with heme arginate. In contrast to heme arginate, ZnMP led to a significant reduction of HO activity. We conclude that the combined effect of ZnMP on highly induced ALAS and on HO may be of potential benefit for human acute hepatic porphyrias and therefore merits further in vivo investigations addressing questions raised by this study.

Kinetic model of in vivo folding and inclusion body formation in recombinant Escherichia coli

Aggregation of misfolded proteins can reduce the yield in recombinant protein production. The underlying complex processes are additionally influenced by cellular physiology. Nevertheless, a lumped-parameter model of kinetic competition between folding and aggregation was sufficient to track properly the specific concentration of a human protein produced in E. coli and its partitioning into soluble and insoluble cell fractions. Accurate estimation of the protein-specific parameters required informative experiments, which were designed using the Fisher information matrix. The model was employed to calculate the influence of the specific glucose uptake rate in high-cell-density cultivation of E. coli on accumulation and aggregation of the recombinant protein. Despite its simplicity, the model was flexible and unbiased concerning unidentified mechanisms. Assuming an exponentially decreasing production rate, the irreversible aggregation step was found to follow first order kinetics, while assuming a constant production rate with simultaneous degradation, the model predicted transient aggregation only. Implications for strain and process development are discussed.

Kinetic model of in vivo folding and inclusion body formation in recombinant Escherichia coli

Aggregation of misfolded proteins can reduce the yield in recombinant protein production. The underlying complex processes are additionally influenced by cellular physiology. Nevertheless, a lumped-parameter model of kinetic competition between folding and aggregation was sufficient to track properly the specific concentration of a human protein produced in E. coli and its partitioning into soluble and insoluble cell fractions. Accurate estimation of the protein-specific parameters required informative experiments, which were designed using the Fisher information matrix. The model was employed to calculate the influence of the specific glucose uptake rate in high-cell-density cultivation of E. coli on accumulation and aggregation of the recombinant protein. Despite its simplicity, the model was flexible and unbiased concerning unidentified mechanisms. Assuming an exponentially decreasing production rate, the irreversible aggregation step was found to follow first order kinetics, while assuming a constant production rate with simultaneous degradation, the model predicted transient aggregation only. Implications for strain and process development are discussed.

Limited heme synthesis in porphobilinogen deaminase-deficient mice impairs transcriptional activation of specific cytochrome P450 genes by phenobarbital

Heme is not only a very important prosthetic group that modulates the structure and activity of heme proteins but also a regulatory molecule that controls metabolic pathways and the biosynthesis of various proteins. However, investigation into heme regulatory effects in higher vertebrates has been hampered by the lack of a suitable animal model. A knockout mouse with targeted disruption of porphobilinogen deaminase, the third enzyme of the heme pathway, has been generated in our laboratory and used in the present study as an in vivo model of heme deficiency to explore diverse heme regulatory properties. In this model with a defined heme disturbance, we observed a superinductive response of delta-aminolevulinate synthase, the first enzyme in heme synthesis, after phenobarbital treatment. We also found that limited heme is associated with decreased induction of cytochrome P450 by phenobarbital as a consequence of impaired gene transcription. This inhibitory effect is isoenzyme-specific, being significant for cyp2a5. The activity and mRNA level of this particular cytochrome P450 are significantly lower in the phenobarbital-induced porphobilinogen deaminase-deficient mice (55% and 43%, respectively), but its expression can be restored to normal values when exogenous heme is administered. Other heme proteins, namely neuronal nitric oxide synthase and soluble guanylate cyclase, function normally in mice with limited heme. Our results demonstrate that the expression of various heme proteins is differentially regulated in conditions of reduced heme availability. Moreover, our findings emphasize the importance of heme protein function in the genesis of pathophysiological manifestations in acute intermittent porphyria.

Simple technique for simultaneous on-line estimation of biomass and acetate from base consumption and conductivity measurements in high-cell density cultures of Escherichia coli

In high-cell density cultures of Escherichia coli, the amount of ammonia required to maintain a constant pH was an effective on-line measure of biomass. When acetic acid formation occurred, biomass estimates were corrected by additional measurements of the culture conductivity. In the absence of acetic acid excretion, the culture conductivity decreased approximately linearly during the fed-batch phase of the high-cell density cultivation. Upward deviation of the culture conductivity from this trend was proportional to the acetate concentration in the medium. Thus, simultaneous determination of the acetic acid concentration and correction of biomass estimates from ammonia consumption were possible by conductivity measurements.

Kinetics of heat-shock response and inclusion body formation during temperature-induced production of basic fibroblast growth factor in high-cell-density cultures of recombinant Escherichia coli

The kinetics of the heat-shock response and the formation of inclusion bodies in recombinant Escherichia coli TG1 were studied in glucose-limited high-cell-density cultures in response to temperature-induced production of human basic fibroblast growth factor (hFGF-2), a protein which partially aggregates into inclusion bodies. The maximum synthesis rates of heat-shock proteins were similar to those in a control cultivation with a strain carrying an expression vector without inducible structural gene. However, the maximum of induction for many heat-shock proteins including DnaK, ClpB, and HtpG was reached at least 30 min later when synthesis of hFGF-2 was simultaneously induced by the temperature upshift. During this first production phase, hFGF-2 was exclusively deposited in the insoluble cell fraction. Thereafter, accumulation of soluble hFGF-2 was observed, too, indicating that the recombinant protein needs heat-shock chaperones for proper folding at elevated temperatures. Strong recombinant protein production prolonged the synthesis of the majority of heat-shock proteins (including GroELS, DnaK, ClpB, and HtpG) even in a wildtype dnaK(+) background. In contrast, the synthesis rates of the small heat-shock proteins IbpA and IbpB declined within 1 h to preinduction values in control and hFGF-2 producing cultures. In the producing cultivation, IbpA and IbpB synthesis ceased to an undetectable level when soluble hFGF-2 started to accumulate, whereas the synthesis rates of the other heat-shock proteins including those belonging to the DnaK and GroEL families remained high throughout the entire production phase.