Characterization of endotoxin and cationic liposome interaction

Safety assessment of a new nanoemulsion-based drug-delivery system reveals unexpected drug-free anticoagulant activity

Aim: A preclinical safety assessment of a novel nanoemulsion drug-delivery system, initially developed to improve the posology of efavirenz (EFV), was conducted with a specific focus on possible immunological and hematological complications. Materials & methods: Assessment of common acute toxicities, such as complement activation and cytokine secretion, was performed using validated assays known to have good correlation with in vivo end points. Results & conclusion: Compared with a standard aqueous solution of EFV, the EFV nanoemulsion showed no significant effect on immune cell function or phenotype. Prolongation of activated partial thromboplastin time was observed for EFV-loaded nanoemulsions (88% at 4 μg/ml) as well as unloaded nanoemulsions (52%) highlighting the potential for drug-free anticoagulant activity and warranting further investigation of the mechanism and utility of these materials.

Pre-clinical immunotoxicity studies of nanotechnology-formulated drugs: Challenges, considerations and strategy

Assorted challenges in physicochemical characterization, sterilization, depyrogenation, and in the assessment of pharmacology, safety, and efficacy profiles accompany pre-clinical development of nanotechnology-formulated drugs. Some of these challenges are not unique to nanotechnology and are common in the development of other pharmaceutical products. However, nanoparticle-formulated drugs are biochemically sophisticated, which causes their translation into the clinic to be particularly complex. An understanding of both the immune compatibility of nanoformulations and their effects on hematological parameters is now recognized as an important step in the (pre)clinical development of nanomedicines. An evaluation of nanoparticle immunotoxicity is usually performed as a part of a traditional toxicological assessment; however, it often requires additional in vitro and in vivo specialized immuno- and hematotoxicity tests. Herein, I review literature examples and share the experience with the NCI Nanotechnology Characterization Laboratory assay cascade used in the early (discovery-level) phase of pre-clinical development to summarize common challenges in the immunotoxicological assessment of nanomaterials, highlight considerations and discuss solutions to overcome problems that commonly slow or halt the translation of nanoparticle-formulated drugs toward clinical trials. Special attention will be paid to the grand-challenge related to detection, quantification and removal of endotoxin from nanoformulations, and practical considerations related to this challenge.

Ambiguities in applying traditional Limulus amebocyte lysate tests to quantify endotoxin in nanoparticle formulations

Nanotechnology is finding increasing application in biology and medicine. As with other pharmaceutical formulations and medical devices intended for use in animals and human patients, contamination of nanoparticles with bacterial endotoxins should be thoroughly investigated before preclinical in vitro and in vivo characterization. Traditional methods to study endotoxin contamination include the in vitro quantitative Limulus Amebocyte Lysate test and the in vivo qualitative rabbit pyrogen test. Both of these tests have a long history of use for traditional pharmaceuticals and medical devices and are routinely used in drug development. Here we report that nanoparticles often interfere with these traditional endotoxin detection tests and suggest approaches to detect and overcome such interferences.

Lipopolysaccharide contamination in intradermal DNA vaccination: toxic impurity or adjuvant?

PURPOSE

Lipopolysaccharides (LPS) are known both as potential adjuvants for vaccines and as toxic impurity in pharmaceutical preparations. The aim of this study was to assess the role of LPS in intradermal DNA vaccination administered by DNA tattooing.

METHOD

Mice were vaccinated with a model DNA vaccine (Luc-NP) with an increasing content of residual LPS. The effect of LPS on systemic toxicity, antigen expression and cellular immunity was studied.

RESULTS

The presence of LPS in the DNA vaccine neither induced systemic toxicity (as reflected by IL-6 concentration in serum), nor influenced antigen expression (measured by intravital imaging). Higher LPS contents however, appeared to be associated with an elevated cytotoxic T-lymphocyte (CTL) response but without reaching statistical significance. Interestingly, the DNA tattoo procedure by itself was shown to induce a serum cytokine response that was at least as potent as that induced by parenteral LPS administration.

CONCLUSION

LPS does not show toxicity in mice vaccinated by DNA tattooing at dose levels well above those encountered in GMP-grade DNA preparations. Thus, residual LPS levels in the pharmaceutical range are not expected to adversely affect clinical outcome of vaccination trials and may in fact have some beneficial adjuvant effect. The observed pro-inflammatory effects of DNA tattoo may help explain the high immunogenicity of this procedure.

Biophysical characterization of triacyl monosaccharide lipid a partial structures in relation to bioactivity

Synthetic triacyl glucosamine monosaccharide lipid A part structures corresponding to the non-reducing moiety of enterobacterial lipid A with an acyloxyacyl chain linked to position 3 of the glucosamine and an unbranched chain linked to position 2 (group 1) and vice versa (group 2) were analyzed biophysically: Fourier-transform infrared spectroscopy was performed to characterize the gel-to-liquid crystalline phase transition, the phosphate band contour, and the orientation of the glucosamine with respect to the membrane surface. Small-angle x-ray diffraction was applied for the elucidation of the supramolecular aggregate structure and, with that, of the molecular shape. With fluorescence resonance energy transfer the lipopolysaccharide-binding protein (LBP)-mediated intercalation of the lipid A partial structures into phospholipid liposomes was monitored. The physical data clearly exhibit a classification of the synthetic compounds into two groups: group 1 compounds have sharp phase transitions, indicating dense acyl chain packing and an inclination of the glucosamine backbone with respect to the membrane surface of 30 degrees with the phosphate buried in the membrane. Group 2 compounds have a very broad phase transition, indicating poorly packed acyl chains, and an inclination of -30 degrees with the phosphate group sticking outward. For the first group unilamellar phases are observed superimposed by a non-lamellar structure, and for the second one only multilamellar aggregate structures. The cytokine-inducing capacity in human mononuclear cells is relatively high for the first group and low or absent for the second group. Based on these data a model of the intra and intermolecular conformations is proposed which also extends the concept of "endotoxic conformation."