Vaccine-induced neutralizing antibodies bind to the H protein of a historical measles virus.

Measles is a highly contagious airborne viral disease. It can lead to serious complications and death and is preventable by vaccination. The live-attenuated measles vaccine (LAMV) derived from a measles virus (MV) isolated in 1954 has been in use globally for six decades and protects effectively by providing a durable humoral and cell-mediated immunity. Our study addresses the temporal stability of epitopes on the viral surface glycoprotein hemagglutinin (H) which is the major target of MV-neutralizing antibodies. We investigated the binding of seven vaccine-induced MV-H-specific monoclonal antibodies (mAbs) to cell-free synthesized MV-H proteins derived from the H gene sequences obtained from a lung specimen of a fatal case of measles pneumonia in 1912 and an isolate from a current case. The binding of four out of seven mAbs to the H protein of both MV strains provides evidence of epitopes that are stable for more than 100 years. The binding of the universally neutralizing mAbs RKI-MV-12b and RKI-MV-34c to the H protein of the 1912 MV suggests the long-term stability of highly conserved epitopes on the MV surface.

Flowing droplet interface bilayers: A microfluidic tool to control droplet trajectories and to study mechanical properties of unsupported lipid bilayers.

We introduce the concept of Flowing Droplet Interface Bilayers (FDIBs) that are made of two droplets maintained in contact due to the presence of an adhesive lipidic surfactant. This system is similar to a flowing dumbbell made of two droplets interconnected by a lipid bilayer and driven by an external flow. Interestingly, such a dumbbell does not show a straight flow trajectory, but it oscillates between the sidewalls while moving along the microchannel. The origin of this unusual motion is hydrodynamic interactions, as demonstrated by analytical calculations and micro particle image velocimentry (µPiV) measurements. The hydrodynamic motion appears to be highly sensitive to the mechanical properties of the lipid bilayer connecting the two droplets (FDIB). Thus, droplet trajectories can be controlled by tuning the lipid bilayer composition, which enables in turn investigating mechanical properties of free-standing lipid bilayers.

Novel Polyomaviruses in Mammals from Multiple Orders and Reassessment of Polyomavirus Evolution and Taxonomy.

As the phylogenetic organization of mammalian polyomaviruses is complex and currently incompletely resolved, we aimed at a deeper insight into their evolution by identifying polyomaviruses in host orders and families that have either rarely or not been studied. Sixteen unknown and two known polyomaviruses were identified in animals that belong to 5 orders, 16 genera, and 16 species. From 11 novel polyomaviruses, full genomes could be determined. Splice sites were predicted for large and small T antigen (LTAg, STAg) coding sequences (CDS) and examined experimentally in transfected cell culture. In addition, splice sites of seven published polyomaviruses were analyzed. Based on these data, LTAg and STAg annotations were corrected for 10/86 and 74/86 published polyomaviruses, respectively. For 25 polyomaviruses, a spliced middle T CDS was observed or predicted. Splice sites that likely indicate expression of additional, alternative T antigens, were experimentally detected for six polyomaviruses. In contrast to all other mammalian polyomaviruses, three closely related cetartiodactyl polyomaviruses display two introns within their LTAg CDS. In addition, the VP2 of Glis glis (edible dormouse) polyomavirus 1 was observed to be encoded by a spliced transcript, a unique experimental finding within the Polyomaviridae family. Co-phylogenetic analyses based on LTAg CDS revealed a measurable signal of codivergence when considering all mammalian polyomaviruses, most likely driven by relatively recent codivergence events. Lineage duplication was the only other process whose influence on polyomavirus evolution was unambiguous. Finally, our analyses suggest that an update of the taxonomy of the family is required, including the creation of novel genera of mammalian and non-mammalian polyomaviruses.

Laboratory investigations of vaccinated patients with varicella.

BACKGROUND: Accompanying varicella vaccination in children in Germany recommended with one (2004) and two (2009) doses, sentinel surveillance of varicella with a sample (n∼900) of private physicians was established in 2005. Physicians reported monthly aggregated data on all varicella cases and case-based on vaccinated patients, of whom skin lesion samples were laboratory investigated to identify varicella-zoster virus (VZV). We analyzed the impact of vaccination frequency on the number of cases and on laboratory results within the sentinel. METHODS: Swabs were obtained with a Teflon tip and sent together with a case-based questionnaire to the reference laboratory. VZV wild-type and vaccine-type was identified by polymerase chain-reaction (PCR) and pyrosequencing methods. Case-based data and laboratory results were analyzed descriptively. RESULTS: From April 2005 to March 2014, of all monthly reported cases (n=111,456) 4789 were vaccinated and eligible for further analysis. No differences were found between laboratory investigated and not investigated cases (1017 vs. 3772) except that the proportion of cases vaccinated twice was higher in lab-cases (29.4% vs. 16.1%). PCR remained negative in 69.6% (197/283) of breakthrough-cases vaccinated twice, in comparison to 22.7% (147/649) breakthrough-cases vaccinated once. VZV was confirmed in 500 (81) patients with breakthrough varicella after one (two) vaccination(s); identification of VZV wild-type, vaccine-type, or no further differentiation was possible in 485 (72), 5 (6), and 10 (3) cases, respectively. CONCLUSION: Varicella breakthrough disease is rare in Germany and suspected clinical cases require laboratory confirmation. The lower confirmation rate of VZV after two vaccine doses suggests a better protection compared to one dose.

Fast kilovoltage/megavoltage (kVMV) breathhold cone-beam CT for image-guided radiotherapy of lung cancer.

Long image acquisition times of 60-120 s for cone-beam CT (CBCT) limit the number of patients with lung cancer who can undergo volume image guidance under breathhold. We developed a low-dose dual-energy kilovoltage-megavoltage-cone-beam CT (kVMV-CBCT) based on a clinical treatment unit reducing imaging time to < or =15 s. Simultaneous kVMV-imaging was achieved by dedicated synchronization hardware controlling the output of the linear accelerator (linac) based on detector panel readout signals, preventing imaging artifacts from interference of the linac's MV-irradiation and panel readouts. Optimization was performed to minimize the imaging dose. Single MV-projections, reconstructed MV-CBCT images and images of simultaneous 90 degrees kV- and 90 degrees MV-CBCT (180 degrees kVMV-CBCT) were acquired with different parameters. Image quality and imaging dose were evaluated and compared to kV-imaging. Hardware-based kVMV synchronization resulted in artifact-free projections. A combined 180 degrees kVMV-CBCT scan with a total MV-dose of 5 monitor units was acquired in 15 s and with sufficient image quality. The resolution was 5-6 line pairs cm(-1) (Catphan phantom). The combined kVMV-scan dose was equivalent to a kV-radiation scan dose of approximately 33 mGy. kVMV-CBCT based on a standard linac is promising and can provide ultra-fast online volume image guidance with low imaging dose and sufficient image quality for fast and accurate patient positioning for patients with lung cancer under breathhold.

Phantom and in-vivo measurements of dose exposure by image-guided radiotherapy (IGRT): MV portal images vs. kV portal images vs. cone-beam CT.

PURPOSE: Positioning verification is usually performed with treatment beam (MV) portal images (PI) using an electronic portal imaging device (EPID). A new alternative is the use of a low energy photon source (kV) and an additional EPID mounted to the accelerator gantry. This system may be used for PI or--with rotating gantry--as cone-beam CT (CBCT). The dose delivered to the patient by different imaging processes was measured. METHODS AND MATERIALS: A total of 15 in-vivo dose measurements were done in five patients receiving prostate IMRT. For anterior-posterior (AP) and lateral PI with MV and kV photons measurement points were inside the rectum and at the patient's skin. Dose for CBCT was measured in the rectum. Additional measurements for CBCT were done in a cylindrical CT-dose-index (CTDI) phantom to determine peripheral, central and weighted CTDI. RESULTS: The dose for AP MV PI was 57.8 mGy at the surface and 33.9 mGy in the rectum, for lateral MV PI 69.4 mGy and 31.7 mGy, respectively (5 MU/exposure). The dose for AP kV PI was 0.8 mGy at the surface and 0.2 mGy in the rectum, for lateral PI 1.1 mGy and 0. 1 mGy, respectively. For a CBCT the rectal dose was 17.2 mGy. The peripheral CTDI was 23.6 mGy and the center dose was 10.2 mGy, resulting in a weighted CTDI of 19.1 mGy in the phantom and an estimated surface dose of < or =28 mGy. CONCLUSIONS: Even taking into account an RBE (Relative Biological Effectiveness) of 2 for kV vs. MV radiation, for kV PI the delivered dose is lower and image quality is better than for MV PI. CBCT provides a 3D-image dataset and dose exposure for one scan is lower than for two MV PI, thus rendering frequent volume imaging during a fractionated course of radiotherapy possible.

Image-guided in vivo dosimetry for quality assurance of IMRT treatment for prostate cancer.

PURPOSE: In external beam radiotherapy (EBRT) and especially in intensity-modulated radiotherapy (IMRT), the accuracy of the dose distribution in the patient is of utmost importance. It was investigated whether image guided in vivo dosimetry in the rectum is a reliable method for online dose verification. METHODS AND MATERIALS: Twenty-one dose measurements were performed with an ionization chamber in the rectum of 7 patients undergoing IMRT for prostate cancer. The position of the probe was determined with cone beam computed tomography (CBCT). The point of measurement was determined relative to the isocenter and relative to an anatomic reference point. The dose deviations relative to the corresponding doses in the treatment plan were calculated. With an offline CT soft-tissue match, patient positioning after ultrasound was verified. RESULTS: The mean magnitude +/- standard deviation (SD) of patient positioning errors was 3.0 +/- 2.5 mm, 5.1 +/- 4.9 mm, and 4.3 +/- 2.4 mm in the left-right, anteroposterior and craniocaudal direction. The dose deviations in points at corresponding positions relative to the isocenter were -1.4 +/- 4.9% (mean +/- SD). The mean dose deviation at corresponding anatomic positions was 6.5 +/- 21.6%. In the rare event of insufficient patient positioning, dose deviations could be >30% because of the close proximity of the probe and the posterior dose gradient. CONCLUSIONS: Image-guided dosimetry in the rectum during IMRT of the prostate is a feasible and reliable direct method for dose verification when probe position is effectively controlled.

Optimization of extracranial stereotactic radiation therapy of small lung lesions using accurate dose calculation algorithms.

BACKGROUND: The aim of this study was to compare and to validate different dose calculation algorithms for the use in radiation therapy of small lung lesions and to optimize the treatment planning using accurate dose calculation algorithms. METHODS: A 9-field conformal treatment plan was generated on an inhomogeneous phantom with lung mimics and a soft tissue equivalent insert, mimicking a lung tumor. The dose distribution was calculated with the Pencil Beam and Collapsed Cone algorithms implemented in Masterplan (Nucletron) and the Monte Carlo system XVMC and validated using Gafchromic EBT films. Differences in dose distribution were evaluated. The plans were then optimized by adding segments to the outer shell of the target in order to increase the dose near the interface to the lung. RESULTS: The Pencil Beam algorithm overestimated the dose by up to 15% compared to the measurements. Collapsed Cone and Monte Carlo predicted the dose more accurately with a maximum difference of -8% and -3% respectively compared to the film. Plan optimization by adding small segments to the peripheral parts of the target, creating a 2-step fluence modulation, allowed to increase target coverage and homogeneity as compared to the uncorrected 9 field plan. CONCLUSION: The use of forward 2-step fluence modulation in radiotherapy of small lung lesions allows the improvement of tumor coverage and dose homogeneity as compared to non-modulated treatment plans and may thus help to increase the local tumor control probability. While the Collapsed Cone algorithm is closer to measurements than the Pencil Beam algorithm, both algorithms are limited at tissue/lung interfaces, leaving Monte-Carlo the most accurate algorithm for dose prediction.

Repositioning accuracy of two different mask systems-3D revisited: comparison using true 3D/3D matching with cone-beam CT.

PURPOSE: The repositioning accuracy of mask-based fixation systems has been assessed with two-dimensional/two-dimensional or two-dimensional/three-dimensional (3D) matching. We analyzed the accuracy of commercially available head mask systems, using true 3D/3D matching, with X-ray volume imaging and cone-beam CT. METHODS AND MATERIALS: Twenty-one patients receiving radiotherapy (intracranial/head-and-neck tumors) were evaluated (14 patients with rigid and 7 with thermoplastic masks). X-ray volume imaging was analyzed online and offline separately for the skull and neck regions. Translation/rotation errors of the target isocenter were analyzed. Four patients were treated to neck sites. For these patients, repositioning was aided by additional body tattoos. A separate analysis of the setup error on the basis of the registration of the cervical vertebra was performed. The residual error after correction and intrafractional motility were calculated. RESULTS: The mean length of the displacement vector for rigid masks was 0.312 +/- 0.152 cm (intracranial) and 0.586 +/- 0.294 cm (neck). For the thermoplastic masks, the value was 0.472 +/- 0.174 cm (intracranial) and 0.726 +/- 0.445 cm (neck). Rigid masks with body tattoos had a displacement vector length in the neck region of 0.35 +/- 0.197 cm. The intracranial residual error and intrafractional motility after X-ray volume imaging correction for rigid masks was 0.188 +/- 0.074 cm, and was 0.134 +/- 0.14 cm for thermoplastic masks. CONCLUSIONS: The results of our study have demonstrated that rigid masks have a high intracranial repositioning accuracy per se. Given the small residual error and intrafractional movement, thermoplastic masks may also be used for high-precision treatments when combined with cone-beam CT. The neck region repositioning accuracy was worse than the intracranial accuracy in both cases. However, body tattoos and image guidance improved the accuracy. Finally, the combination of both mask systems with 3D image guidance has the potential to replace therapy simulation and intracranial stereotaxy.

Frameless stereotactic radiosurgery of a solitary liver metastasis using active breathing control and stereotactic ultrasound.

BACKGROUND AND PURPOSE: Radiosurgery of liver metastases is effective but a technical challenge due to respiration-induced movement. The authors report on the initial experience of the combination of active breathing control (ABC) with stereotactic ultrasound (B-mode acquisition and targeting [BAT]) for frameless radiosurgery. PATIENTS AND METHODS: A patient with a solitary, inoperable liver metastasis from cholangiocellular carcinoma is presented (Figure 4). ABC (Figure 3) was used for tumor/liver immobilization. Tumor/liver position was controlled and corrected using ultrasound (BAT; Figure 1). The tumor was irradiated with a single dose of 24 Gy. RESULTS: Using ABC, the motion of the tumor was significantly reduced and the overall positioning error was < 5 mm (Figure 2). BAT allowed a rapid localization of the lesion during breath hold which could be performed without difficulties for 20 s. Overall treatment time was acceptable (30 min). CONCLUSION: Frameless stereotactic radiotherapy with the combination of ABC and BAT allows the delivery of high single doses to targets accessible to ultrasound with high precision comparable to a frame-based approach.

Fast rigid registration in radiation therapy.

Based on a stochastic mutual information type matching and RPROP as stochastic optimizer, an interactive image-based registration of a CT volume onto two 2D images provided by a megavoltage system is presented. The matching process is based on semi-automatic pre-segmentation, an approximate 2D-2D matching with precomputed virtual projections (DRRs) followed by an accurate 3D-2D matching step. Our sample-based approach requires only a fraction of computed DRRs for 3D-2D. A simultaneous computation of the DRR rays and their perturbations in 6 dimensions speeds up the rendering process by a factor of 6.8. The complete registration process takes 5.6 +/- 2.3 seconds on a 3 GHz Pentium IV PC, being the fastest non-parallel approach for this sort of application the authors are aware of.