COVID-19 vaccination strategy for hospital staff in Germany: a cross-sectional study in March-April 2021

BACKGROUND

SARS-CoV-2 vaccination for healthcare workers (HCWs) started in Germany in December 2020. Hospitals had little time to prepare a vaccination strategy.

AIM

To gather information on the initial vaccination strategy for HCWs from the infection control practitioners in Germany.

METHODS

A cross-sectional, ethically approved questionnaire was developed, formatted as an online survey and pre-tested. Infection control practitioners responsible for hygiene/infection prevention in 987 randomly selected German hospitals were invited to participate in the survey in March and April 2021. For statistical analysis, the hospitals were categorized into two groups based on bed capacity (<500 beds: small; ≥500 beds: large).

FINDINGS

One hundred out of 987 (10%) infection control practitioners completed the survey. In 80% of the participating hospitals, HCW vaccination prioritization was based on recommendations of the German standing committee on vaccination (STIKO). Even so, only 54% prioritized the vaccination of HCWs with contact to vulnerable patients, thus deviating from STIKO recommendations. HCWs with a high personal health risk were prioritized for vaccination in 24% of the hospitals. Transferring unvaccinated HCWs to an area with less infection risk was considered by 2% of large and 12% of small hospitals.

CONCLUSION

Vaccination prioritization differed across hospitals and deviated from STIKO recommendations. A pandemic preparedness concept should address the potential impact of divergent strategies compared to a common approach. In addition, further studies analysing the reasons why HCWs remain unvaccinated are needed to adopt effective strategies. This is especially important against the background of facility-based compulsory vaccination.

Infection control strategies for patients and accompanying persons during the COVID-19 pandemic in German hospitals: a cross-sectional study in March-April 2021

BACKGROUND

Patients are at risk of nosocomial COVID-19 infection. The role of accompanying persons/visitors as potential infection donors is not yet well researched, but the risk will be influenced by prevention measures recommended by infection control practitioners.

AIM

To collect information about COVID-19 infection control strategies for patients and accompanying persons from infection control practitioners in German hospitals.

METHODS

A cross-sectional questionnaire was developed, ethically approved, pre-tested and formatted as an online tool. Infection control practitioners in 987 randomly selected German hospitals were invited to participate in March and April 2021. For statistical analysis, the hospitals were categorized as small (0-499 beds) or large (≥500 beds).

FINDINGS

One hundred surveys were completed (response rate: 10%). A higher proportion of large (71%) than small (49%) hospitals let patients decide freely whether to wear medical or FFP2 masks. Most hospitals reported spatial separation for COVID-19 patients and non-COVID-19 cases (38%) or additionally for suspected COVID-19 cases (53%). A separation of healthcare teams for these areas existed in 54% of the hospitals. Accompaniment bans were more prevalent in large (52%) than in small hospitals (29%), but large hospitals granted more exemptions.

CONCLUSION

The decision as to whether to separate areas and teams seemed to depend on the hospital's structural conditions, therefore impairing the implementation of recommendations. Accompaniment regulations differ between hospital sizes and may depend on patient numbers, case type/severity and patients' requirements. In the dynamic situation of a pandemic, it can be difficult to stay up to date with findings and recommendations on infection control.

Synthesis and pharmacological evaluation of [18F]PBR316: a novel PET ligand targeting the translocator protein 18 kDa (TSPO) with low binding sensitivity to human single nucleotide polymorphism rs6971

Radiopharmaceuticals that target the translocator protein 18 kDa (TSPO) have been investigated with positron emission tomography (PET) to study neuroinflammation, neurodegeneration and cancer. We have developed the novel, achiral, 2-phenylimidazo[1,2-a]pyridine, PBR316 that targets the translocator protein 18 kDa (TSPO) that addresses some of the limitations inherent in current TSPO ligands; namely specificity in binding, blood brain barrier permeability, metabolism and insensitivity to TSPO binding in subjects as a result of rs6971 polymorphism. PBR316 has high nanomolar affinity (4.7-6.0 nM) for the TSPO, >5000 nM for the central benzodiazepine receptor (CBR) and low sensitivity to rs6971 polymorphism with a low affinity binders (LABs) to high affinity binders (HABs) ratio of 1.5. [18F]PBR316 was prepared in 20 ± 5% radiochemical yield, >99% radiochemical purity and a molar activity of 160-400 GBq μmol-1. Biodistribution in rats showed high uptake of [18F]PBR316 in organs known to express TSPO such as heart (3.9%) and adrenal glands (7.5% ID per g) at 1 h. [18F]PBR316 entered the brain and accumulated in TSPO-expressing regions with an olfactory bulb to brain ratio of 3 at 15 min and 7 at 4 h. Radioactivity was blocked by PK11195 and Ro 5-4864 but not Flumazenil. Metabolite analysis showed that radioactivity in adrenal glands and the brain was predominantly due to the intact radiotracer. PET-CT studies in mouse-bearing prostate tumour xenografts indicated biodistribution similar to rats with radioactivity in the tumour increasing with time. [18F]PBR316 shows in vitro binding that is insensitive to human polymorphism and has specific and selective in vivo binding to the TSPO. [18F]PBR316 is suitable for further biological and clinical studies.

Reduction of nosocomial bloodstream infections and nosocomial vancomycin-resistant Enterococcus faecium on an intensive care unit after introduction of antiseptic octenidine-based bathing

BACKGROUND

Vancomycin-resistant Enterococcus faecium (VRE) is emerging in German intensive care units (ICUs). On a 32-bed surgical ICU at a university hospital, increasing numbers of nosocomial cases occurred despite enforcement of hand hygiene and environmental disinfection.

AIM

To introduce universal octenidine-based bathing in order to reduce the burden of VRE.

METHODS

Between January 2012 and March 2014, patients were screened for VRE on admission and twice weekly. Active surveillance was undertaken for VRE infections and colonizations, and for bloodstream infections (BSI) with any pathogen. Intervention in this before-after study comprised of standardized octenidine-based bathing. Distinct subgroups of VRE colonizations or infections were defined and used for statistical analysis of frequency, prevalence and incidence density.

FINDINGS

In the pre-intervention period (January 2012 to April 2013), the admission prevalence of VRE was 4/100 patients and the mean incidence density of nosocomial cases was 7.55/1000 patient-days (PD). Pulsed-field gel electrophoresis analysis revealed prevalence of three vanA and two vanB clusters. In the post-intervention period (August 2013 to March 2014), the admission prevalence of VRE was 2.41/100 patients and the mean incidence density of nosocomial cases was 2.61/1000 PD [P = 0.001 (pre- vs post-intervention)]. Thirteen nosocomial VRE infections were identified in the pre-intervention period, compared with one nosocomial VRE infection in the post-intervention period. Incidence densities of BSI pre- and post-intervention were 2.98 and 2.06/1000 PD (P = 0.15), respectively.

CONCLUSION

The epidemiology of emerging VRE appeared as a complex mix of admitted cases and transmissions in small clusters, challenging infection control measures. The implementation of universal octenidine-based bathing combined with a standardized washing regime led to a significant reduction in nosocomial VRE.

[CF Lung Disease - a German S3 Guideline: Module 2: Diagnostics and Treatment in Chronic Infection with Pseudomonas aeruginosa]

Cystic Fibrosis (CF) is the most common autosomal-recessive genetic disease affecting approximately 8000 people in Germany. The disease is caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene leading to dysfunction of CFTR, a transmembrane chloride channel. This defect causes insufficient hydration of the epithelial lining fluid which leads to chronic inflammation of the airways. Recurrent infections of the airways as well as pulmonary exacerbations aggravate chronic inflammation, lead to pulmonary fibrosis and tissue destruction up to global respiratory insufficiency, which is responsible for the mortality in over 90 % of patients. The main aim of pulmonary treatment in CF is to reduce pulmonary inflammation and chronic infection. Pseudomonas aeruginosa (Pa) is the most relevant pathogen in the course of CF lung disease. Colonization and chronic infection are leading to additional loss of pulmonary function. There are many possibilities to treat Pa-infection. This is a S3-clinical guideline which implements a definition for chronic Pa-infection and demonstrates evidence-based diagnostic methods and medical treatment for Pa-infection in order to give guidance for individual treatment options.

Preclinical in vivo and in vitro comparison of the translocator protein PET ligands [18F]PBR102 and [18F]PBR111

PURPOSE

To determine the metabolic profiles of the translocator protein ligands PBR102 and PBR111 in rat and human microsomes and compare their in vivo binding and metabolite uptake in the brain of non-human primates (Papio hamadryas) using PET-CT.

METHODS

In vitro metabolic profiles of PBR102 and PBR111 in rat and human liver microsomes were assessed by liquid chromatography-tandem mass spectrometry. [¹⁸F]PBR102 and [¹⁸F]PBR111 were prepared by nucleophilic substitution of their corresponding p-toluenesulfonyl precursors with [¹⁸F]fluoride. List mode PET-CT brain imaging with arterial blood sampling was performed in non-human primates. Blood plasma measurements and metabolite analysis, using solid-phase extraction, provided the metabolite profile and metabolite-corrected input functions for kinetic model fitting. Blocking and displacement PET-CT scans, using PK11195, were performed.

RESULTS

Microsomal analyses identified the O-de-alkylated, hydroxylated and N-de-ethyl derivatives of PBR102 and PBR111 as the main metabolites. The O-de-alkylated compounds were the major metabolites in both species; human liver microsomes were less active than those from rat. Metabolic profiles in vivo in non-human primates and previously published rat experiments were consistent with the microsomal results. PET-CT studies showed that K₁ was similar for baseline and blocking studies for both radiotracers; V_T was reduced during the blocking study, suggesting low non-specific binding and lack of appreciable metabolite uptake in the brain.

CONCLUSIONS

[¹⁸F]PBR102 and [¹⁸F]PBR111 have distinct metabolic profiles in rat and non-human primates. Radiometabolites contributed to non-specific binding and confounded in vivo brain analysis of [¹⁸F]PBR102 in rodents; the impact in primates was less pronounced. Both [¹⁸F]PBR102 and [¹⁸F]PBR111 are suitable for PET imaging of TSPO in vivo. In vitro metabolite studies can be used to predict in vivo radioligand metabolism and can assist in the design and development of better radioligands.

Radiosynthesis, In Vivo Biological Evaluation, and Imaging of Brain Lesions with [123I]-CLINME, a New SPECT Tracer for the Translocator Protein

The high affinity translocator protein (TSPO) ligand 6-chloro-2-(4'-iodophenyl)-3-(N,N-methylethyl)imidazo[1,2-a]pyridine-3-acetamide (CLINME) was radiolabelled with iodine-123 and assessed for its sensitivity for the TSPO in rodents. Moreover neuroinflammatory changes on a unilateral excitotoxic lesion rat model were detected using SPECT imaging. [(123)I]-CLINME was prepared in 70-80% radiochemical yield. The uptake of [(123)I]-CLINME was evaluated in rats by biodistribution, competition, and metabolite studies. The unilateral excitotoxic lesion was performed by injection of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid unilaterally into the striatum. The striatum lesion was confirmed and correlated with TSPO expression in astrocytes and activated microglia by immunohistochemistry and autoradiography. In vivo studies with [(123)I]-CLINME indicated a biodistribution pattern consistent with TPSO distribution and the competition studies with PK11195 and Ro 5-4864 showed that [(123)I]-CLINME is selective for this site. The metabolite study showed that the extractable radioactivity was unchanged [(123)I]-CLINME in organs which expresses TSPO. SPECT/CT imaging on the unilateral excitotoxic lesion indicated that the mean ratio uptake in striatum (lesion:nonlesion) was 2.2. Moreover, TSPO changes observed by SPECT imaging were confirmed by immunofluorescence, immunochemistry, and autoradiography. These results indicated that [(123)I]-CLINME is a promising candidate for the quantification and visualization of TPSO expression in activated astroglia using SPECT.

Synthesis and biological characterisation of 18F-SIG343 and 18F-SIG353, novel and high selectivity σ2 radiotracers, for tumour imaging properties

Background

Sigma2 (σ₂) receptors are highly expressed in cancer cell lines and in tumours. Two novel selective ¹⁸F-phthalimido σ₂ ligands, ¹⁸F-SIG343 and ¹⁸F-SIG353, were prepared and characterised for their potential tumour imaging properties.

Methods

Preparation of ¹⁸F-SIG343 and ¹⁸F-SIG353 was achieved via nucleophilic substitution of their respective nitro precursors. In vitro studies including radioreceptor binding assays in the rat brain membrane and cell uptake studies in the A375 cell line were performed. In vivo studies were carried out in mice bearing A375 tumours including positron emission tomography (PET) imaging, biodistribution, blocking and metabolite studies.

Results

In vitro studies showed that SIG343 and SIG353 displayed excellent affinity and selectivity for σ₂ receptors (Ki(σ₂) = 8 and 3 nM, σ₂:σ₁ = 200- and 110-fold, respectively). The σ₂ selectivity of ¹⁸F-SIG343 was further confirmed by blocking studies in A375 cells, however, not noted for ¹⁸F-SIG353. Biodistribution studies showed that both radiotracers had similar characteristics including moderately high tumour uptake (4%ID/g to 5%ID/g); low bone uptake (3%ID/g to 4%ID/g); and high tumour-to-muscle uptake ratios (four- to sevenfold) up to 120 min. Although radiotracer uptake in organs known to express σ receptors was significantly blocked by pre-injection of competing σ ligands, the blocking effect was not observed in the tumour. PET imaging studies indicated major radioactive localisation in the chest cavity for both ligands, with approximately 1%ID/g uptake in the tumour at 120 min. Metabolite studies showed that the original radiotracers remained unchanged 65% to 80% in the tumour up to 120 min.

Conclusions

The lead ligands showed promising in vitro and in vivo characteristics. However, PET imaging indicated low tumour-to-background ratios. Furthermore, we were unable to demonstrate that uptake in the A375 tumour was σ₂-specific. ¹⁸F-SIG343 and ¹⁸F-SIG343 do not display ideal properties for imaging the σ₂ receptor in the A375 tumour model. However, since the radiotracers show promising in vitro and in vivo characteristics, longer scans using appropriate half-life isotopes and alternative tumour models will be carried out in future studies to fully validate the imaging characteristics of these radiotracers.

Central nervous system expression and PET imaging of the translocator protein in relapsing-remitting experimental autoimmune encephalomyelitis

Glial neuroinflammation is associated with the development and progression of multiple sclerosis. PET imaging offers a unique opportunity to evaluate neuroinflammatory processes longitudinally in a noninvasive and clinically translational manner. (18)F-PBR111 is a newly developed PET radiopharmaceutical with high affinity and selectivity for the translocator protein (TSPO), expressed on activated glia. This study aimed to investigate neuroinflammation at different phases of relapsing-remitting (RR) experimental autoimmune encephalomyelitis (EAE) in the brains of SJL/J mice by postmortem histologic analysis and in vivo by PET imaging with (18)F-PBR111.

METHODS

RR EAE was induced by immunization with PLP(139-151) peptide in complete Freund's adjuvant. Naive female SJL/J mice and mice immunized with saline-complete Freund's adjuvant were used as controls. The biodistribution of (18)F-PBR111 was measured in 13 areas of the central nervous system and compared with PET imaging results during different phases of RR EAE. The extents of TSPO expression and glial activation were assessed with immunohistochemistry, immunofluorescence, and a real-time polymerase chain reaction.

RESULTS

There was significant TSPO expression in all of the central nervous system areas studied at the peak of the first clinical episode and, importantly, at the preclinical stage. In contrast, only a few TSPO-positive cells were observed at the second episode. At the third episode, there was again an increase in TSPO expression. TSPO expression was associated with microglial cells or macrophages without obvious astrocyte labeling. The dynamics of (18)F-PBR111 uptake in the brain, as measured by in vivo PET imaging and biodistribution, followed the pattern of TSPO expression during RR EAE.

CONCLUSION

PET imaging with the TSPO ligand (18)F-PBR111 clearly reflected the dynamics of microglial activation in the SJL/J mouse model of RR EAE. The results are the first to highlight the discrepancy between the clinical symptoms of EAE and TSPO expression in the brain, as measured by PET imaging at the peaks of various EAE episodes. The results suggest a significant role for PET imaging investigations of neuroinflammation in multiple sclerosis and allow for in vivo follow-up of antiinflammatory treatment strategies.

PET imaging of brain inflammation during early epileptogenesis in a rat model of temporal lobe epilepsy

BACKGROUND

Recently, inflammatory cascades have been suggested as a target for epilepsy therapy. Positron emission tomography (PET) imaging offers the unique possibility to evaluate brain inflammation longitudinally in a non-invasive translational manner. This study investigated brain inflammation during early epileptogenesis in the post-kainic acid-induced status epilepticus (KASE) model with post-mortem histology and in vivo with [18F]-PBR111 PET.

METHODS

Status epilepticus (SE) was induced (N = 13) by low-dose injections of KA, while controls (N = 9) received saline. Translocator protein (TSPO) expression and microglia activation were assessed with [125I]-CLINDE autoradiography and OX-42 immunohistochemistry, respectively, 7 days post-SE. In a subgroup of rats, [18F]-PBR111 PET imaging with metabolite-corrected input function was performed before post-mortem evaluation. [18F]-PBR111 volume of distribution (Vt) in volume of interests (VOIs) was quantified by means of kinetic modelling and a VOI/metabolite-corrected plasma activity ratio.

RESULTS

Animals with substantial SE showed huge overexpression of TSPO in vitro in relevant brain regions such as the hippocampus and amygdala (P < 0.001), while animals with mild symptoms displayed a smaller increase in TSPO in amygdala only (P < 0.001). TSPO expression was associated with OX-42 signal but without obvious cell loss. Similar in vivo [18F]-PBR111 increases in Vt and the simplified ratio were found in key regions such as the hippocampus (P < 0.05) and amygdala (P < 0.01).

CONCLUSION

Both post-mortem and in vivo methods substantiate that the brain regions important in seizure generation display significant brain inflammation during epileptogenesis in the KASE model. This work enables future longitudinal investigation of the role of brain inflammation during epileptogenesis and evaluation of anti-inflammatory treatments.

Vaccination for Parkinson's disease

Idiopathic Parkinson's disease (PD) is, like other neurodegenerative diseases such as Alzheimer's disease (AD) considered a proteinopathy. Thus, a disease that is driven by the accumulation and aggregation of misfolded proteins, in case of PD α-synuclein (aSyn) is incriminated. Accordingly, removal of aSyn is assumed of having the potential to modify the course of the disease. Both active and passive aSyn targeting immunotherapy were found to modify disease in mice overexpressing human aSyn and recapitulating various aspects of synucleopathies. Translating immunotherapy to humans needs to consider the issue of potential autoimmunity. PD vaccines developed by AFFiRiS integrate the safety concept as applied for the company's AD vaccine candidates. This includes the use of short antigens, precluding activation of aSyn-specific T cells and, thus, cellular autoimmunity. Moreover, the selection of AFFITOPES® for clinical development is based on the principle of exclusive aSyn reactivity of vaccine-induced Abs excluding crossreactivity to β-synuclein (bSyn), which is ensured by the AFFITOME® platform technology. PD01, the first in class aSyn vaccine developed by AFFiRiS is about to enter the clinical phase of development.

Increase of patients co-colonised or co-infected with methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecium or extended-spectrum β-lactamase-producing Enterobacteriaceae

PURPOSE

To determine the incidence of patients co-colonised or co-infected with methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium or extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in four German tertiary care hospitals.

METHODS

This study was conducted at four tertiary care hospitals (all with >1,000 beds) in different geographic regions in Germany (Berlin in the east, Luebeck in the north, Freiburg in the southwest and Nuernberg in the southeast). Routine surveillance data on MRSA, vancomycin-resistant enterococci (VRE) and ESBL-producing bacteria were analysed from 2007 to 2009. Co-colonisation or co-infection was defined as a patient having positive cultures for at least two of the following resistant pathogens: MRSA, VRE faecium or different species of ESBL-producing Enterobacteriaceae within one calendar year.

RESULTS

A total of 896,822 patients were analysed, of which 10,066 patients harboured MRSA, VRE faecium and/or ESBL-producing Enterobacteriaceae, and 542 patients co-harboured at least two of those resistant pathogens. In 2009, 7.6% of the MRSA patients, 13.7% of the VRE faecium patients and even 16.1% of the ESBL-producing Enterobacteriaceae patients were co-colonised or co-infected. The incidence of patients with co-infection or co-colonisation increased steadily from 5 (2007) to 7 per 10,000 patients (2009).

CONCLUSIONS

Patients harbouring ESBL-producing Enterobacteriaceae or VRE faecium had a higher risk of being co-colonised or co-infected compared to what was to be extrapolated from their overall incidence. This might be linked to their gastrointestinal reservoir and impracticality to decolonise the gut of resistant VRE and ESBL-producing Enterobacteriaceae.

A rapid solid-phase extraction method for measurement of non-metabolised peripheral benzodiazepine receptor ligands, [(18)F]PBR102 and [(18)F]PBR111, in rat and primate plasma

OBJECTIVES

To develop a rapid and reliable method for estimating non-metabolised PBR ligands fluoroethoxy ([(18)F]PBR102)- and fluoropropoxy ([(18)F]PBR111)-substituted 2-(6-chloro-2-phenyl)imidazo[1,2-a]pyridine-3-yl)-N,N-diethylacetamides in plasma.

METHODS

Rats and baboons were imaged with PET up to 2 h postinjection of [(18)F]PBR102 and [(18)F]PBR111 under baseline conditions, after pre-blocking or displacement with PK11195. Arterial plasma samples were directly analysed by reverse-phase solid-phase extraction (RP-SPE) and RP-HPLC and by normal-phase TLC. SPE cartridges were successively washed with acetonitrile/water mixtures. SPE eluant radioactivity was measured in a γ-counter to determine the parent compound fraction and then analysed by HPLC and TLC for validation.

RESULTS

In SPE, hydrophilic and lipophilic radiolabelled metabolites were eluted in water and 20% acetonitrile/water. All non-metabolised [(18)F]PBR102 and [(18)F]PBR111 were in SPE acetonitrile fraction as confirmed by HPLC and TLC analysis. Unchanged (%) [(18)F]PBR102 and [(18)F]PBR111 from SPE analysis in rat and baboon plasma agreed with those from HPLC and TLC analysis. In rats and baboons, the fraction of unchanged tracer followed a bi-exponential decrease, with half-lives of 7 to 10 min for the fast component and >80 min for the slow component for both tracers.

CONCLUSIONS

Direct plasma SPE analysis of [(18)F]PBR102 and [(18)F]PBR111 can reliably estimate parent compound fraction. SPE was superior to HPLC for samples with low activity; it allows rapid and accurate metabolite analysis of a large number of plasma samples for improved estimation of metabolite-corrected input function during quantitative PET imaging studies.

Evaluation of [¹²³I]-CLINDE as a potent SPECT radiotracer to assess the degree of astroglia activation in cuprizone-induced neuroinflammation

PURPOSE

The purpose of this study was to assess the feasibility and sensitivity of the high-affinity translocator protein (TSPO) ligand [(123)I]-CLINDE in imaging TSPO changes in vivo and characterise and compare astroglial and TSPO changes in the cuprizone model of demyelination and remyelination in C57BL/6 mice.

METHODS

C57BL/6 mice were fed with cuprizone for 4 weeks to induce demyelination followed by 2-4 weeks of standard diet (remyelination). Groups of mice were followed by in vivo single photon emission computed tomography (SPECT)/CT imaging using [(123)I]-CLINDE and uptake correlated with biodistribution, autoradiography, immunohistochemistry, immunofluorescence and real-time polymerase chain reaction (RT-PCR).

RESULTS

The uptake of [(123)I]-CLINDE in the brain as measured by SPECT imaging over the course of treatment reflects the extent of the physiological response, with significant increases observed during demyelination followed by a decrease in uptake during remyelination. This was confirmed by autoradiography and biodistribution studies. A positive correlation between TSPO expression and astrogliosis was found and both activated astrocytes and microglial cells expressed TSPO. [(123)I]-CLINDE uptake reflects astrogliosis in brain structures such as corpus callosum, caudate putamen, medium septum and olfactory tubercle as confirmed by both in vitro and in vivo results.

CONCLUSION

The dynamics in the cuprizone-induced astroglial and TSPO changes, observed by SPECT imaging, were confirmed by immunofluorescence, RT-PCR and autoradiography. The highly specific TSPO radioiodinated ligand CLINDE can be used as an in vivo marker for early detection and monitoring of a variety of neuropathological conditions using noninvasive brain imaging techniques.

Synthesis of [123I]iodine labelled imidazo[1,2-b] pyridazines as potential probes for the study of peripheral benzodiazepine receptors using SPECT

The pyridazines 3-acetamidomethyl-6-chloro-2-(4´-iodophenyl)imidazo[1,2-b]pyridazine 1 (IC50=1.6 nM) and 3-benzamidomethyl-6-iodo-2-(4´-t-butylphenyl)imidazo[1,2-b] pyridazine 2 (IC50=4.2 nM), are high affinity and selective ligands for the Peripheral Benzodiazepine Receptors (PBR) compared to the Central Benzodiazepine counterparts. The [123I] 1 and [123I] 2 labelled analogues of these compounds were subsequently synthesised for the potential study of the PBR in vivo using SPECT. Radioiodination of [123I] 1 was achieved by iododestannylation of the corresponding tributyl tin precursor with Na[ 123I] in the presence of peracetic acid or chloramine-T and the product isolated by C-18 RP HPLC. Radioiodination of [123I] 2 was achieved by copper assisted bromine [123I]iodine exchange of the corresponding bromo precursor in the presence of acetic acid and sodium bisulfate as reducing agent at 200 °C. Purification of the crude products were achieved by semi-preparative C-18 RP HPLC to give the products in radiochemical yields >90%. The products were obtained in >97% chemical and radiochemical purity and with specific activities >180 GBq/μmol.

Discovery of [18F]N-(2-(diethylamino)ethyl)-6-fluoronicotinamide: a melanoma positron emission tomography imaging radiotracer with high tumor to body contrast ratio and rapid renal clearance

The high melanoma uptake and rapid body clearance displayed by our series of [(123)I]iodonicotinamides prompted the development of [(18)F]N-(2-(diethylamino)ethyl)-6-fluoronicotinamide ([(18)F]2), a novel radiotracer for PET melanoma imaging. Significantly, unlike fluorobenzoates, [(18)F]fluorine incorporation on the nicotinamide ring is one step, facile, and high yielding. [(18)F]2 displayed high tumor uptake, rapid body clearance via predominantly renal excretion, and is currently being evaluated in preclinical studies for progression into clinical trials to assess the responsiveness of therapeutic agents.

Synthesis of substituted [123I]imidazo[1,2-α]pyridines as potential probes for the study of the peripheral benzodiazepine receptors using SPECT

The imidazo[1,2-α]pyridines [N,N´-dimethyl-6-chloro-(4´zf-iodophenyl)imidazo[1,2-α]pyridine-3-acetamide 1, [N,N´l-6-chloro-(4´-iodophenyl)imidazo[1,2-α]pyridine-3-acetamide 2, and [N-methyl-6-chloro-(4´-iodophenyl)imidazo[1,2-α]pyridine-3-acetamide 3, are high affinity and selective ligands for the Peripheral Benzodiazepine Receptors (PBR). The [123I]1-3 labelled analogues of these compounds were subsequently synthesised for the potential study of the PBR in vivo using SPECT. Radioiodination was achieved by iododestannylation reactions of the corresponding tributyl tin precursors with Na[123I] in the presence of peracetic acid, chloramine-T or Iodogen. Purification of the crude product was achieved by semipreparative C-18 RP HPLC to give the products in radiochemical yields of 40-85%. The products were obtained in >97% chemical and radiochemical purity and with specific activities >80 GBq/μmol.

Development of AFFITOPE vaccines for Alzheimer's disease (AD)--from concept to clinical testing

Based on the notion that cerebral accumulation of certain Abeta species is central to AD pathogenesis and endowed with the knowledge that emerged during clinical testing of the first human Alzheimer vaccine, AN1792, we designed a new generation of Alzheimer vaccines. Rather than relying on full-length Abeta itself or fragments thereof, AFFITOPE vaccines use short peptides, mimicking parts of the native Abeta sequence, as their antigenic component. The technology created to identify these peptides, termed AFFITOPE-technology, at the same time provides the basis for the multi-component safety concept realized in AFFITOPE vaccines. First, as they are nonself, AFFITOPES don't need to break tolerance typically established against self proteins. This allows us to use aluminium hydroxide, the agent first approved as immunological adjuvant for human use and, thus, exhibiting an excellent safety profile. Second, AFFITOPES employed in Alzheimer vaccines are only 6 amino acids in length, which precludes the activation of Abeta-specific autoreactive T cells. Third, and above all, the AFFITOPE technology allows for controlling the specificity of the vaccine-induced antibody response focusing it exclusively on Abeta and preventing crossreactivity with APP. In a program based on two AFFITOPES allowing neoepitope targeting of Abeta (free N-terminus), this approach was taken all the way from concept to clinical application. Early clinical data support the safety concept inherent to AFFITOPE Alzheimer vaccines. Further clinical testing will focus on the identification of the optimal vaccine dose and immunization schedule. Together, result of these trials will provide a solid basis for clinical POC studies.

Synthesis and evaluation of novel radioiodinated nicotinamides for malignant melanoma

INTRODUCTION

A series of iodonicotinamides based on the melanin-binding iodobenzamide compound N-2-diethylaminoethyl-4-iodobenzamide was prepared and evaluated for the potential imaging and staging of disseminated metastatic melanoma.

METHODS

[(123)I]Iodonicotinamides were prepared by iododestannylation reactions using no-carrier-added iodine-123 and evaluated in vivo by biodistribution and competition studies and by single photon emission computed tomography (SPECT) imaging in black and albino nude mice bearing B16F0 murine melanotic and A375 human amelanotic melanoma tumours, respectively.

RESULTS

The iodonicotinamides displayed low-affinity binding for sigma(1)-sigma(2) receptors (K(i)>300 nM). In biodistribution studies in mice, N-(2-(diethylamino)ethyl)-5-[(123)I]iodonicotinamide ([(123)I]1) exhibited the fastest and highest uptake of the nicotinamide series in the B16F0 tumour at 1 h ( approximately 8% ID/g), decreasing slowly over time. No uptake was observed in the A375 tumour. Clearance from the animals by urinary excretion was more rapid for N-alkyl-nicotinamides than for piperazinyl derivatives. At 1 h postinjection, the urinary excretion was 66% ID for [(123)I]1, while the gastrointestinal tract amounted to 17% ID. Haloperidol was unable to reduce the uptake of [(123)I]1 in pigmented mice, indicating that this uptake was likely due to an interaction with melanin. SPECT imaging of [(123)I]1 in black mice bearing the B16F0 melanoma indicated that the radioactivity was predominately located in the tumour and eyes. No specific localisation was observed in nude mice bearing A375 amelanotic tumours.

CONCLUSION

These findings suggest that [(123)I]1, which displays high tumour uptake with rapid clearance from the body, could be a promising imaging agent for the detection of melanotic tumours.

Synthesis and biological evaluation of substituted [18F]imidazo[1,2-a]pyridines and [18F]pyrazolo[1,5-a]pyrimidines for the study of the peripheral benzodiazepine receptor using positron emission tomography

The fluoroethoxy and fluoropropoxy substituted 2-(6-chloro-2-phenyl)imidazo[1,2- a]pyridin-3-yl)- N, N-diethylacetamides 8 (PBR102) and 12 (PBR111) and 2-phenyl-5,7-dimethylpyrazolo[1,5- a]pyrimidin-3-yl)- N, N-diethylacetamides 15 (PBR099) and 18 (PBR146) were synthesized and found to have high in vitro affinity and selectivity for the peripheral benzodiazepine receptors (PBRs) when compared with the central benzodiazepine receptors (CBRs). The corresponding radiolabeled compounds [ (18)F] 8 [ (18)F] 12, [ (18)F] 15, and [ (18)F] 18 were prepared from their p-toluenesulfonyl precursors in 50-85% radiochemical yield. In biodistribution studies in rats, the distribution of radioactivity of the [ (18)F]PBR compounds paralleled the known localization of PBRs. In the olfactory bulbs, where the uptake of radioactivity was higher than in the rest of the brain, PK11195 and Ro 5-4864 were able to significantly inhibit [ (18)F] 12, while little or no pharmacological action of these established PBR drugs were observed on the uptake of [ (18)F] 8, [ (18)F] 15, and [ (18)F] 18 compared to control animals. Hence, [ (18)F] 12 appeared to be the best candidate for evaluation as an imaging agent for PBR expression in neurodegenerative disorders.

Evaluation of CLINDE as potent translocator protein (18 kDa) SPECT radiotracer reflecting the degree of neuroinflammation in a rat model of microglial activation

BACKGROUND

The translocator protein (TSPO; 18 kDa), the new name of the peripheral-type benzodiazepine receptor, is localised in mitochondria of glial cells and expressed in very low concentrations in normal brain. Their expression rises after microglial activation following brain injury. Accordingly, TSPO are potential targets to evaluate neuroinflammatory changes in a variety of CNS disorders.

PURPOSE

To date, only a few effective tools are available to explore TSPO by SPECT. We characterised here 6-chloro-2-(4'iodophenyl)-3-(N,N-diethyl)-imidazo[1,2-a]pyridine-3-acetamide or CLINDE in a rat model with different stages of excitotoxic lesion.

METHODS

Excitotoxicity was induced in male Wistar rats by unilateral intrastriatal injection of different amounts of quinolinic acid (75, 150 or 300 nmol). Six days later, two groups of rats (n = 5-6/group) were i.v. injected with [(125)I]-CLINDE (0.4 MBq); one group being pre-injected with PK11195 (5 mg/kg). Brains were removed 30 min after tracer injection and the radioactivity of cerebral areas measured. Complementary ex vivo autoradiography, in vitro autoradiography ([(3)H]-PK11195) and immunohistochemical studies (OX-42) were performed on brain sections.

RESULTS

In the control group, [(125)I]-CLINDE binding was significantly higher (p < 0.001) in lesioned than that in intact side. This binding disappeared in rats pre-treated with PK11195 (p < 0.001), showing specific binding of CLINDE to TSPO. Ex vivo and in vitro autoradiographic studies and immunohistochemistry were consistent with this, revealing a spatial correspondence between radioactivity signal and activated microglia. Regression analysis yielded a positive relation between the ligand binding and the degree of neuroinflammation.

CONCLUSION

These results demonstrate that CLINDE is suitable for TSPO in vivo SPECT imaging to explore their involvement in neurodegenerative disorders associated with microglial activation.

[Infection control measures and surveillance of patients with ventricular assist devices]

Ventricular assist devices (VAD) are a new routine therapy option for end-stage heart failure. However, the incidence of VAD-related infections varies between 20 and 188% and makes a major contribution to VAD-related morbidity. Therefore, optimised infection control policies should be applied to prevent VAD-related infections. As to date only a few studies exist investigating particular prevention measures for VAD recipients, we have tried to adapt evidence-based guidelines. In detail the following preventive measures are discussed: antibiotic prophylaxis, endocarditis prophylaxis, dressing technique for the driveline-exit site and education of patients and medical staff. A new patient-based surveillance system is proposed which reflects the different times since implantation of VADs and therefore allows a fair method for interhospital comparison.

Adverse Effects of Rabies Pre- and Postexposure Prophylaxis in 290 Health-Care-Workers Exposed to a Rabies Infected Organ Donor or Transplant Recipients

The recent unfortunate rabies transmissions through solid organ transplants of an infected donor in Germany required the initiation of a vaccination program to protect health care workers (HCWs) with close contact to rabies-infected patients. A systematic follow-up of adverse effects was initiated. Rabies postexposure prophylaxis (PEP) was started in 269 HCWs at four German hospitals. Pre-exposure prophylaxis (PreEP) was administered to 74 HCWs caring for an already diagnosed rabies patient. At each vaccination date, HCWs were interviewed for symptoms possibly representing adverse effects. Adverse effects of PEP and PrePEP were compared. Out of 269 HCWs, 216 were included for the investigation of adverse effects. Of these 216 HCWs, 114 (53%) individuals developed at least one systemic adverse effect. Incidences of tiredness (30.6%), malaise (26.4%), headache (26.9%), dizziness (14.8%), and chills (13.0%) declined in the course of PEP (p < 0.05), whereas incidences of fever (7.4%), paraesthesias (7.9%), arthralgias (1.9%), myalgias (4.2%), nausea (9.3%), diarrheas (2.8%) and vomiting (1.4%) did not. In 11 (5.1%) HCWs PEP was discontinued mostly due to adverse reactions (four suffered strong headaches, two HCWs meningeal irritations, two chills, one paraesthesia, one malaise, and one a rush). Systemic effects of PEP or PreEP did not differ significantly. Despite relatively high incidences of moderate severe adverse reactions rabies PEP is safe. Strong headache, tiredness, dizziness, and paraesthesias are the most important postvaccinal symptoms. Vaccinees suffering from adverse effects of PEP must be strongly encouraged to complete PEP, as it is to date the only protection against fatal rabies.

Preparation and biologic evaluation of a novel radioiodinated benzylpiperazine, 123I-MEL037, for malignant melanoma

Radiopharmaceuticals that can target the random metastatic dissemination of melanoma tumors may present opportunities for imaging and staging the disease as well as potential radiotherapeutic applications. A novel molecule, 2-(2-(4-(4-(123)I-iodobenzyl)piperazin-1-yl)-2-oxoethyl)isoindoline-1,3-dione (MEL037), was synthesized, labeled with 123I, and evaluated for application in melanoma tumor scintigraphy and radiotherapy.

METHODS

The tumor imaging potential of 123I-MEL037 was studied in vivo in C57BL/6J female mice bearing the B16F0 murine melanoma tumor and in BALB/c nude mice bearing the A375 human amelanotic melanoma tumor by biodistribution, competition studies, and SPECT.

RESULTS

123I-MEL037 exhibited high and rapid uptake in the B16F0 melanoma tumor at 1 h (13 %ID/g [percentage injected dose per gram]), increasing with time to reach 25 %ID/g at 6 h. A significant uptake was also observed in the eyes (2 %ID, at 3-6 h after injection) of black mice. No uptake was observed in the tumor or in the eyes of nude mice bearing the A375 tumor. Because of high uptake and long retention in the tumor and rapid body clearance, the mean contrast ratios (MCR) of 123I-MEL037 were 30 and 60, at 24 and 48 h after injection, respectively. At 24 h after injection of mice bearing the B16 melanoma, SPECT indicated that the radioactivity was located predominately in the tumor followed by the eyes, whereas no specific localization of the radioactivity was noted in mice bearing the A375 human amelanotic tumor. In competition experiments, uptake of 123I-MEL037 in brain, lung, heart, and kidney--organs known to contain sigma-receptors--was not significantly different in haloperidol-treated animals compared with control animals. Therefore, reduction of uptake in tumor and eyes of the pigmented mice bearing the B16F0 tumor suggested that the mechanism of tumor uptake was likely due to an interaction with melanin.

CONCLUSION

These findings suggested that 123I-MEL037, which displays a rapid and very high tumor uptake, appeared to be a promising imaging agent for detection of most melanoma tumors with the potential for development as a therapeutic agent in melanoma tumor proliferation.

Synthesis and evaluation of novel radioiodinated benzamides for malignant melanoma

The imaging potential of a series of [123I]benzamides was studied in mice bearing B16F0 melanoma tumors. Compound [123I]25 exhibited tumor uptake >8 %ID/g at 1 h, while that of [123I]14d and [123I]25 reached a maximum of 9-12 %ID/g at 6 h. Standardized uptake values of [123I]14d were higher than 100 between 24 and 72 h after injection. In haloperidol treated animals, the tumor uptake of [123I]14d was not significantly different to controls, while significant reduction of [123I]25 uptake was observed, supporting that [123I]14d uptake relates to melanin interaction, whereas part of the mechanism of [123I]25 uptake is related to its sigma 1-receptor affinity. Benzamides 14d and 25, which display rapid and high tumor uptake, appear to be promising imaging agents for melanoma detection, while 14d, which displays a long lasting and high melanoma/nontarget ratio, is more suitable for evaluation as a potential radiotherapeutic.

Prävention und Kontrolle der Ausbreitung von Vancomycin-resistenten Enterokokken

The incidence of vancomycin-resistant enterococci (VRE), especially E. faecium, is increasing in several German hospitals and some facilities have experienced VRE outbreaks. The German National Nosocomial Infection Surveillance System has also noticed a sharp increase in the incidence of nosocomial VRE infections per 10,000 patients from 0.5 in 2003 to 11.0 in 2005 accompanied by a rise in VRE-associated mortality. However, the reasons of this increase remain unknown. As VRE may cause severe nosocomial infections, transmission must be restricted. This article provides the guidelines as defined by the workshop of the German Society for Hygiene and Microbiology for the prevention of VRE transmission in both, endemic and epidemic, settings. The following topics are discussed: indication for VRE screening, microbiological diagnostics, general infection control measures (isolation precautions and use of protective clothing) and additional hygiene measures in the nosocomial VRE outbreak setting.