Development of a Generic Anti-PEG Antibody Assay Using BioScale's Acoustic Membrane MicroParticle Technology

Immunogenicity testing for PEGylated biotherapeutics should include methods to detect both anti-protein and anti-PEG antibodies (anti-PEG). Although some methods have been published for the detection of anti-PEG antibodies, the information is incomplete and, in some cases, reagents used (such as Tween-20) are known to interfere with detection. This rapid communication describes the use of BioScale's Acoustic Membrane MicroParticle (AMMP®) technology using the ViBE® Workstation to measure anti-PEG antibodies in human serum samples. Briefly, a sample spiked with monoclonal human IgG anti-PEG antibody is diluted in buffer and incubated with paramagnetic beads coated with linear chain mPEG to capture anti-PEG antibodies. The complex is then captured on an acoustic membrane coated with Protein A. The change in mass on the membrane caused by the binding of the complex to the membrane results in a signal proportional to the mass of anti-PEG antibodies. The data indicate that an assay with a sensitivity of less than 1000 ng/mL for IgG is achievable. This level of sensitivity is better than current published reports on IgG anti-PEG antibody detection.

Abstract LB-94: Nanoparticle-based RNAi therapy for the delivery of personalized siRNA payloads to KRAS-driven tumors

The current landscape of druggable disease targets represents only ~10% of the human genome. Among those targets that are frequently mutated in cancer yet remain undruggable by conventional small molecules are the Ras family of GTPases. Somatic mutations in KRAS occur in 35% of colorectal cancers, 16% of lung cancers and 61% of pancreatic cancers. Common KRAS mutations lock the enzyme in the active GTP-bound state, which leads to constitutive activation of downstream effector modules such as MAPK, PI3K, Ral, Rac and Rho, which promote tumor growth, proliferation and survival.

RNAi interference allows for the ablation of any gene product through the engagement of the endogenous microRNA machinery. The successful delivery of siRNA against KRAS or downstream effectors to tumors would represent a novel alternative treatment for KRASmut cancers, which currently lack strong clinical options. We have thus developed an RNAi therapy that employs 1) a cyclodextrin-based nanoparticle with high siRNA carrying capacity and tumor-targeting modules; and 2) highly potent “Sensor” siRNAs that can be used at low dose to efficiently ablate gene targets while avoiding off-target effects.

We have assembled a library of potent Sensor siRNAs, which are identified using a massively parallel biological assay. These siRNA sequences are screened in high-throughput in KRASmut cell lines for negative effects on viability and disruption of cellular signaling pathways (ViBE, Bioscale). To subsequently assess the ability of these personalized nanoparticle-siRNA treatments to inhibit the growth of KRASmut tumors, we have developed an in vivo screening platform to monitor nanoparticle-siRNA delivery and payload efficacy at varying siRNA doses. Successful delivery of siRNAs to solid tumors has been one of the major hurdles to the advancement of RNAi therapy. Our fluorescent reporter system thus allows for the careful tracking of nanoparticle delivery and siRNA payload activity in real time using optical imaging. Additionally, the effect of different nanoparticle-siRNA treatments on transduced tumor cells can be measured non-invasively in real time.

We demonstrate that delivery of low dose Sensor siRNAs targeting KRAS and other effector genes to KRASmut xenograft tumors significantly impedes tumor growth by inhibition of MAPK signaling and induction of apoptosis. The highly customizable nature of the siRNA payload offers a promising and universal platform to access previously intractable targets such as KRAS and personalize treatment for various oncogene-addicted tumors.

Citation Format: Tina L. Yuan, Chih-Shia Lee, Christof Fellmann, Cayde Ritchie, Changwoo Lee, Colin Merrifield, Thomas Schluep, Scott W. Lowe, Ji Luo, Frank McCormick. Nanoparticle-based RNAi therapy for the delivery of personalized siRNA payloads to KRAS-driven tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-94. doi:10.1158/1538-7445.AM2013-LB-94

High-resolution CT in the evaluation of clinically suspected Pneumocystis carinii pneumonia in AIDS patients with normal, equivocal, or nonspecific radiographic findings

OBJECTIVE

We prospectively studied AIDS patients with a high clinical pretest probability of Pneumocystis carinii pneumonia (PCP) in whom chest radiographic findings were normal, equivocal, or nonspecific with high-resolution CT (HRCT) to determine the incidence of PCP in these patients, to assess the diagnostic accuracy of HRCT for the presence or absence of PCP, to evaluate the role of HRCT in patient management, and to determine the clinical outcome of all patients 1 month after evaluation.

SUBJECTS AND METHODS

All patients were referred to the Division of Pulmonary and Critical Care Medicine for diagnosis of clinically suspected PCP. Thirty-three patients were prospectively evaluated with HRCT within 24 hr of diagnostic bronchoalveolar lavage; 18 other patients who underwent HRCT were managed according to the HRCT interpretation and followed up clinically. All HRCT scans were independently reviewed by three chest radiologists; patchy or nodular ground-glass attenuation was considered to indicate "possible PCP."

RESULTS

The incidence of PCP was 12% (6/51). The sensitivity of HRCT was 100%; specificity, 89%; and accuracy, 90% (p < .005). We had five false-positive and no false-negative interpretations. Some form of "airways disease" (n = 23) was the single most common HRCT interpretation.

CONCLUSION

HRCT may allow exclusion of PCP in patients with findings that are normal, equivocal, or nonspecific on chest radiographs. Empiric therapy or immediate bronchoscopy can be avoided in many patients on the basis of the HRCT findings.

Impact of Streptococcus pneumoniae bacteremia and human immunodeficiency virus type 1 on oral mucosal immunity

To determine whether defects in mucosal immunity were associated with invasive disease caused by a mucosal pathogen, Streptococcus pneumoniae, levels of salivary immunoglobulins and nonspecific immune factors were compared in subjects with human immunodeficiency virus type 1 (HIV-1) infection and in HIV-1-seronegative subjects with and without pneumococcal bacteremia. The IgA2 subclass may be of particular importance because S. pneumoniae produces IgA1 protease, which cleaves IgA1 but not IgA2. Levels (37-56 micrograms/mL) and proportions (11%-17%) of IgA2 were similar among groups. Serotype-specific capsular salivary IgA was present in a minority of patients with acute bacteremia. Levels of lactoferrin were increased with bacteremia. Neither selective mucosal IgA2 deficiency nor impaired nonspecific upper respiratory mucosal responses were associated with invasive pneumococcal disease during HIV-1 infection; thus, other defects in mucosal cellular responses and systemic immunity may predispose HIV-1-infected patients to invasive pneumococcal disease.