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Muramyl dipeptide (MDP) is the smallest peptidoglycan fragment capable of triggering the innate immune system through interaction with the intracellular NOD2 receptor. To develop synthetic vaccine modalities composed of an antigenic entity (typically a small peptide) and a molecular adjuvant with well-defined activity, we previously assembled covalent MDP-antigen conjugates. Although these were found to be capable of stimulating the NOD2 receptor and were processed by dendritic cells (DCs) leading to effective antigen presentation, DC maturation--required for an apt immune response--could not be achieved with these conjugates. To improve the efficacy of these vaccine modalities, we equipped the MDP moiety with lipophilic tails, well-known modifications to enhance the immune-stimulatory activity of MDPs. Herein we report the design and synthesis of a lipophilic MDP-antigen conjugate and show that it is a promising vaccine modality capable of stimulating the NOD2 receptor, maturing DCs, and delivering antigen cargo into the MHC-I cross-presentation pathway., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

New analogues (UPam) of triacylated lipopeptide Pam3CysSK4, a popular agonist of Toll-like receptor 2 (TLR2), were designed making use of the cocrystal structure of a TLR2 heterodimer (with TLR1) with Pam3CysSK4. Twenty-two UPam derivatives that feature an N-tetradecylcarbamyl chain to mimic the native N-palmitoyl moiety and various small amino acids residues at the penultimate N-terminal position were prepared via solid-phase synthesis. In vitro evaluation of immunostimulatory properties revealed new potent TLR2 ligands.

The covalent attachment of an innate immune system stimulating agent to an antigen can provide active vaccine modalities capable of eliciting a potent immune response against the incorporated antigen. Here we describe the design, automated synthesis and immunological evaluation of a set of four muramyl dipeptide-peptide antigen conjugates. Muramyl dipeptide (MDP) represents a well-known ligand for the intracellular NOD2 receptor and our study shows that covalently linking an MDP-moiety to an antigenic peptide can lead to a construct that is capable of stimulating the NOD2 receptor if the ligand is attached at the anomeric center of the muramic acid. The constructs can be processed by dendritic cells (DCs) and the conjugation does not adversely affect the presentation of the incorporated SIINFEKL epitope on MHC-I molecules. However, stimulation of the NOD2 receptor in DCs was not sufficient to provide a strong immunostimulatory signal.

A concise stereoselective route providing access to both enantiomers of the bioactive quinolizidine alkaloid lasubine II has been developed. The enantioselectivity was introduced by taking advantage of a proline-catalyzed asymmetric Mannich reaction. Next, the bicyclic system was constructed via a diastereoselective Mannich cyclization and subsequent ring-closing metathesis as the key steps.

Currently total hip replacement surgery using minimally invasive techniques is a fast developing field. However, all reports concern adaptations of surgical techniques with adapted instruments using conventional implants. These conventional implants limit the minimal invasiveness to some extent. In this paper a new system is reported featuring a new surgical approach, new instrumentation and a new implant design. The purpose of this study was to introduce the system and to assess the feasibility of the system in terms of stability, range of motion and wear characteristics. The pre-clinical tests indicated that the factor of safety for this type of design is smaller than for conventional implants. However, the results show adequate performance of the system, which suggests that further development and testing is justified to advance the system for clinical use.

In this study, the initial stability of the femoral component of a minimal invasive total hip replacement was biomechanically evaluated during simulated normal walking and chair rising. A 20 mm diameter canal was created in the femoral necks of five fresh frozen human cadaver bones and the femoral heads were resected at the smallest cross-sectional area of the neck. The relatively short, polished, taper-shaped prostheses were cemented centrally in this canal according to a standardized procedure. A servohydraulic testing machine was used to apply dynamic loads to the prosthetic head. Radiostereophotogrammetric analysis was used to measure rotations and translations between the prosthesis and bone. In addition, the reconstructions were loaded until failure in a static, displacement-controlled test. During the dynamic experiments, the femoral necks did not fail and no macroscopical damage was detected. Maximal values were found for normal walking with a mean rotation of about 0.2 degrees and a mean translation of about 120 microm. These motions stabilized during testing. The mean static failure load was 4714 N. The results obtained in this study are promising and warrant further development of this type of minimal invasive hip prosthesis.

In this in vitro study we evaluated the initial stability of cementless femoral stems using an injectable calcium phosphate (Ca-P) cement. The cement was not used to form a cement mantle as is routinely done in PMMA cemented prostheses but functioned as an additive to fill the small gaps that exist between a press-fit placed titanium plasma sprayed implant and the bone bed. Six pair of Beagle femora were used in this study. In a random fashion, one femur of each pair was used for placement of a prosthesis without Ca-P cement, the contralateral was used for press-fit placement after injection of the calcium phosphate cement into the intramedullary canal. The reconstructions were placed in a MTS testing machine, tilted 15 degrees in varsus and 15 degrees of endorotation to obtain a physiological load on the femoral head. The load was applied stepwise from zero to a maximum of 100, 250 and 400 N, respectively. At each loading step the load was applied dynamically at a frequency of 1 Hz for 30 min. Between the loading steps, the load was removed for 10 min to allow elastic recovery. The stability of the stems was determined at each loading step with roentgen-stereophotogrammetric analysis. Results showed that with the prostheses without Ca-P cement the most important displacements were movement into varus (max. 818 microm under 400 N) and subsidence (max. 587 microm under 400 N). The displacements showed large variation. After unloading some elastic recovery occurred. In the specimens with Ca-P cement, displacements were negligible. As determined by an F-test the variations found were significantly smaller for the press-fit+Ca-P cement relative to the press-fit prosthesis at all loading steps (p<0.05). A paired t-test revealed significant differences in the mentioned displacements between the press-fit- and press-fit+Ca-P cement prosthesis at a loading with 400 N (P<0.05). On the basis of these results we conclude that the use of Ca-P cement increases the initial stability of press-fit inserted plasma-sprayed femoral prostheses and corrects for the high variability in displacements found with press-fit insertion of these femoral hip prostheses.

Although the revision rates for modern knee prostheses have decreased drastically, the total number of revisions a year is increasing because many more primary knee replacements are being done. At the time of revision, bone loss is common, which compromises prosthetic stability. To improve stability, intramedullary stems are often used. The aim of this study was to estimate the effects of a stem, its diameter and the interface bonding conditions on patterns of the bone remodeling in the distal femur. We created finite element models of the distal half of a femur in which 4 types of knee prostheses were placed. The bone remodeling process was simulated using a strain-adaptive bone remodeling theory. The amount of such remodeling was determined by calculating the changes in bone mineral density in 9 regions of interest from simulated DEXA scans. The computer simulation model showed that revision prostheses tend to cause more bone resorption than primary ones, especially in the most distal regions. Predicted long-term bone loss due to a revision prosthesis with a thin stem equalled that around a prosthesis with an intercondylar box. However, strong regional differences were found--the stemmed prostheses having more bone loss in the most distal areas and some bone gain in the more proximal ones. A prosthesis with a thick stem led to an increase in bone loss. When the prosthesis-cement interface was bonded, more bone loss was predicted than with an unbonded interface. These results suggest that a stem which increases stability initially may reduce stability in the long term. This is due to an increase in stress shielding and bone resorption.