CHARACTERIZATION OF BRANCHED HISTIDINE-LYSINE POLYPEPTIDES USED FOR NUCLEIC ACID DELIVERY AND THEIR COMPLEXES WITH DNA AND SMALL INTERFERING RNA.

DNA and siRNA must be packaged for protection prior to transfection in vivo when they are administered to humans or other animals. Dr. A. J. Mixson's laboratory at the University of Maryland, Baltimore Medical School has developed a family of branched histidine-lysine (HK) peptides that confer improved transfection in mice compared to naked nucleic acid. The branched polymer denoted H3K4b has a superior ability to transfect siRNA in vitro compared to H3K(+G)4b. H3K(+G)4b, made by the addition of two glycines to each of the original H3K4b branches, is presumably a more flexible polymer, and it allows for better transfection of plasmid DNA than H3K4b. Biophysical characterization of the HK-DNA and HK-siRNA complexes is aimed at understanding how the structures of both peptides affect their biological activity. This characterization was performed using ethidium bromide exclusion from nucleic acid, DNase I plasmid degradation, dynamic light scattering, circular dichroism, isothermal titration calorimetry and atomic force microscopy. Results from the characterization suggest that H3K4b forms condensed regions of packaged plasmid with some repeating accessibility of the DNA, compared to a more even coating of plasmid by H3K(+G)4b. Based on these results a "coating versus clumping" model was developed to relate the transfection efficiency of each peptide to its binding of plasmid DNA. A specific model for packaging of siRNA with these peptides was not developed, but we believe that characteristics that lead to effective transfection of plasmid are not key to siRNA delivery. A better understanding of characteristics important to peptide-nucleic acid complex formation may lead to the development of improved transfection agents

Surface-Modified HK:siRNA Nanoplexes with Enhanced Pharmacokinetics and Tumor Growth Inhibition

We characterized in this study the pharmacokinetics and antitumor efficacy of histidine-lysine (HK):siRNA nanoplexes modified with PEG and a cyclic RGD (cRGD) ligand targeting αvβ3 and αvβ5 integrins. With noninvasive imaging, systemically administered surface-modified HK:siRNA nanoplexes showed nearly 4-fold greater blood levels, 40% higher accumulation in tumor tissue, and 60% lower luciferase activity than unmodified HK:siRNA nanoplexes. We then determined whether the surface-modified HK:siRNA nanoplex carrier was more effective in reducing MDA-MB-435 tumor growth with an siRNA targeting Raf-1. Repeated systemic administration of the selected surface modified HK:siRNA nanoplexes targeting Raf-1 showed 35% greater inhibition of tumor growth than unmodified HK:siRNA nanoplexes and 60% greater inhibition of tumor growth than untreated mice. The improved blood pharmacokinetic results and tumor localization observed with the integrin-targeting surface modification of HK:siRNA nanoplexes correlated with greater tumor growth inhibition. This investigation reveals that through control of targeting ligand surface display in association with a steric PEG layer, modified HK: siRNA nanoplexes show promise to advance RNAi therapeutics in oncology and potentially other critical diseases

Development and validation of a Luminex assay for detection of a predictive biomarker for PROSTVAC-VF therapy

<div><p>Cancer therapies can provide substantially improved survival in some patients while other seemingly similar patients receive little or no benefit. Strategies to identify patients likely to respond well to a given therapy could significantly improve health care outcomes by maximizing clinical benefits while reducing toxicities and adverse effects. Using a glycan microarray assay, we recently reported that pretreatment serum levels of IgM specific to blood group A trisaccharide (BG-A_tri) correlate positively with overall survival of cancer patients on PROSTVAC-VF therapy. The results suggested anti-BG-A_tri IgM measured prior to treatment could serve as a biomarker for identifying patients likely to benefit from PROSTVAC-VF. For continued development and clinical application of serum IgM specific to BG-A_tri as a predictive biomarker, a clinical assay was needed. In this study, we developed and validated a Luminex-based clinical assay for measuring serum IgM specific to BG-A_tri. IgM levels were measured with the Luminex assay and compared to levels measured using the microarray for 126 healthy individuals and 77 prostate cancer patients. This assay provided reproducible and consistent results with low %CVs, and tolerance ranges were established for the assay. IgM levels measured using the Luminex assay were found to be highly correlated to the microarray results with R values of 0.93–0.95. This assay is a Laboratory Developed Test (LDT) and is suitable for evaluating thousands of serum samples in CLIA certified laboratories that have validated the assay. In addition, the study demonstrates that discoveries made using neoglycoprotein-based microarrays can be readily migrated to a clinical assay.</p></div

Overview of neoglycoproteins and assay formats.

<p>Glycans or glycopeptides are covalently coupled to albumin to produce neoglycoproteins, which are then printed onto a microarray surface and used to detect IgM to BG-A_tri. Neoglycoproteins immobilized on Luminex microspheres mimic glycan presentation on the microarray surface.</p

Comparison of BG-A_tri signals measured using the Luminex assay and the microarray assay.

<p>Comparison of BG-A_tri signals measured using the Luminex assay and the microarray assay.</p

Analytical validation summary.

<p>For the analytical validation, for each sample dilution, we ran eight plates with twelve replicates on each plate (n = 96).</p

Assay specificity^a.

<p>Assay specificity<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0182739#t002fn001" target="_blank">^a</a>.</p

Selection of sample dilution.^a

<p>Selection of sample dilution.<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0182739#t001fn001" target="_blank">^a</a></p