Peptide mimotopes of capsular polysaccharides have been proposed as antigens for vaccines against encapsulated pathogens. In this study, we determined the antibody response to and efficacy of P13, a peptide mimetic of the Cryptococcus neoformans capsular polysaccharide glucuronoxylomannan (GXM), in mice that produce human antibodies. P13 was conjugated to tetanus toxoid (TT) or diphtheria toxoid (DT) and administered subcutaneously in Alhydrogel with or without CpG to mice transgenic for human immunoglobulin loci (XenoMouse mice) and expressing either immunoglobulin G2 (IgG2) (G2 mice) or IgG4 (G4 mice). Mice were vaccinated and revaccinated two or three times. The serum antibody responses of the mice to GXM and P13 and antibody idiotype expression were analyzed by an enzyme-linked immunosorbent assay. The results showed that both P13-TT and P13-DT were antigenic, inducing a mimetic response to P13 in both G2 and G4 mice, and immunogenic, inducing a mimotope response including V H 3 (idiotype)-positive antibodies to GXM in G2 but not G4 mice. CpG led to higher titers of IgG to P13 and GXM in P13-TT-vaccinated G2 mice. C. neoformans challenge of P13-protein conjugate-vaccinated and control G2 mice induced anamnestic IgG-and V H 3-positive responses to GXM and was associated with a significantly decreased risk of death and a prolongation of survival in P13-DT-vaccinated mice compared to phosphate-buffered saline-treated or protein carrier-vaccinated mice. These findings reveal that P13 elicited a human antibody response with V H 3 expression in human immunoglobulin transgenic mice that has been observed for human antibodies to GXM and support the concept that peptide mimotope-based vaccines may hold promise for the treatment of C. neoformans infections.

IntroductionBlisibimod is a potent B cell-activating factor (BAFF) antagonist that binds to both cell membrane-expressed and soluble BAFF. The goal of these first-in-human studies was to characterize the safety, tolerability, and pharmacokinetic and pharmacodynamic profiles of blisibimod in subjects with systemic lupus erythematosus (SLE).MethodsSLE subjects with mild disease that was stable/inactive at baseline received either a single dose of blisibimod (0.1, 0.3, 1, or 3 mg/kg subcutaneous [SC] or 1, 3, or 6 mg/kg intravenous [IV]) or placebo (phase 1a; N = 54), or four weekly doses of blisibimod (0.3, 1, or 3 mg/kg SC or 6 mg/kg IV) or placebo (phase 1b; N = 63). Safety and tolerability measures were collected, and B cell subset measurements and pharmacokinetic analyses were performed.ResultsAll subjects (93 % female; mean age 43.7 years) carried the diagnosis of SLE for ≥ 1 year. Single- and multiple-dose treatment with blisibimod produced a decrease in the number of naïve B cells (24–76 %) and a transient relative increase in the memory B cell compartment, with the greatest effect on IgD-CD27+; there were no notable changes in T cells or natural killer cells. With time, memory B cells reverted to baseline, leading to a calculated 30 % reduction in total B cells by approximately 160 days after the first dose. In both the single- and multiple-dosing SC cohorts, the pharmacokinetic profile indicated slow absorption, dose-proportional exposure from 0.3 through 3.0 mg/kg SC and 1 through 6 mg/kg IV, linear pharmacokinetics across the dose range of 1.0–6.0 mg/kg, and accumulation ratios ranging from 2.21 to 2.76. The relative increase in memory B cells was not associated with safety signals, and the incidence of adverse events, anti-blisibimod antibodies, and clinical laboratory abnormalities were comparable between blisibimod- and placebo-treated subjects.ConclusionsBlisibimod changed the constituency of the B cell pool and single and multiple doses of blisibimod exhibited approximate dose-proportional pharmacokinetics across the dose range 1.0–6.0 mg/kg. The safety and tolerability profile of blisibimod in SLE was comparable with that of placebo. These findings support further studies of blisibimod in SLE and other B cell-mediated diseases.Trial registrationClinicaltrials.gov NCT02443506. Registered 11 May 2015. NCT02411136 Registered 7 April 2015.

The aim of the study was to characterize performance of a complementary set of assays to measure antigen‐specific immune responses in subjects immunized with a neoantigen. Healthy volunteers (HV) (n = 8) and patients with systemic lupus erythematosus (SLE) (n = 6) were immunized with keyhole limpet haemocyanin (KLH) on days 1 and 29. Serum antibodies were detected using a flow cytometric bead array (CBA) that multiplexed the KLH response alongside pre‐existing anti‐tetanus antibodies. Peripheral blood mononuclear cells were studied by B cell ELISPOT. These assays were built upon precedent assay development in cynomolgus monkeys, which pointed towards their utility in humans. Primary anti‐KLH IgG responses rose to a mean of 65–93‐fold above baseline for HV and SLE patients, respectively, and secondary responses rose to a mean of 260‐170‐fold above baseline. High levels of anti‐tetanus IgG were detected in pre‐immunization samples and their levels did not change over the course of study. Anti‐KLH IgG1‐4 subclasses were characterized by a predominant IgG1 response, with no significant differences in subclass magnitude or distribution between HV and SLE subjects. Anti‐KLH IgM levels were detectable, although the overall response was lower. IgM was not detected in two SLE subjects whodid generate an IgG response. All subjects responded to KLH by B cell ELISPOT, with no significant differences observed between HV and SLE subjects. The CBA and B cell ELISPOT assays reliably measured anti‐KLH B cell responses, supporting use of this approach and these assays to assess the pharmacodynamic and potential safety impact of marketed/investigational immune‐therapeutics.

Objective: Characterization of peripheral leukocytes is an important aspect of monitoring the effect of immunotherapeutic interventions in systemic lupus erythematosus (SLE). We analyzed cell surface markers commonly used to assess patients with SLE, focusing on the effect of holding blood prior to processing/analysis and the relative reliability of the measurements that were conducted.Methods: Healthy volunteers (HV; n 5 20) and patients with SLE (n 5 42) were studied. Whole blood was collected for flow cytometric analysis on days 1, 8, 15, 105, 195, 285, and 375 and held overnight for analysis. A subset of samples was additionally analyzed on the day of collection.Results: Variability arising from overnight storage of whole blood was found to be within 20% for most lymphocyte subsets. There was greater between rather than within subject variability over a 1-year period. As anticipated, the data showed higher CD38 and lower CD19 densities on B cells from patients with SLE compared to HV. Although a higher percentage of cells with markers of plasmablasts/cells were observed in the blood of patients with SLE relative to HV, these measurements were found to be among the least reliable (i.e., most variable).Conclusions: This study provides technical perspectives for those conducting immunophenotypic analyses of B-cells in patients with SLE. We envision that our data, which addresses sample stability issues and presents a method to describe the relative reliability of one measure over another, holds value for clinical assessments of B-cells in SLE and the evaluation of investigational agents designed to modify the B-cell compartment. Numerous B-cell directed therapies are now either marketed or are under active clinical investigation for autoimmune diseases including systemic lupus erythematosus (SLE) (1). These include rituximab, which leads to rapid and profound decrease in circulating B-cells; as well as epratuzumab, an anti-CD22 antibody that also specifically targets B cells but leads to a partial depletion in peripheral B cells. Inhibition of the TNF family cytokine BAFF, either alone or with APRIL, leads to functional inhibition of B-cells and a partial decrease in the number of circulating B-cells over several months (2-4).Changes in numbers and the relative distributions of circulating B-cells and B-cell subsets as a consequence of

Background: The need to implement robust biomarkers in clinical trials has never been greater, and such efforts can be easily compromised by reagent instability or simple human error during assay setup. Many biotechnology and pharmaceutical companies are introducing efforts to conduct biomarker studies under more rigorous settings, and the use of plates or tubes pre-loaded with stimulation or staining reagents could be of value for studies that involve flow cytometry.Methods: Five reagents lyophilized from ethanol or CHAPS buffer stock solution of phorbol 12-myristate 13-acetate (PMA) and ionomycin were benchmarked against standard DMSO liquid formulation for their stimulation equivalency. The median fluorescence intensity of phosphorylated ribosomal protein S6 in lymphocytes was assessed on a BD FACSCalibur TM . Results: We demonstrate here that tubes pre-loaded with lyophilized versions of the liquid reagents can provide equivalent stimulation in healthy volunteer specimens.Conclusions: The value of this approach is that it safeguards against omission or erroneous addition of bulk liquid formulations of PMA and ionomycin to the reaction vessel (i.e., plate or tube) and also lends itself to extended stability/shelf-life of these reagents. On the basis of this initial success, we plan to expand our evaluation of lyophilized reagents so that they can be incorporated into our clinical biomarker campaigns as appropriate. V C 2009 Clinical Cytometry Society

We recommend the application of a strategically designed step-wise approach to transfer cell-based assays that includes assessing analytical performance (through a fit for purpose validation and/or design of experiment robustness characterization), clinical performance (i.e., concordance) and performance or proficiency testing for long-term method monitoring. Here we focus on the application of this strategy to cell-based assays for the measurement of neutralizing anti-drug antibodies. This application is unique in that it requires a custom cell-based assay to be used over a long period of time (potentially phase 1a through the life of a marketed product) with the confidence of consistent method performance and result reporting. But, the process is adaptable to a variety of assay types and applications. We present lessons learned from two cell-based assay transfers that met relevant challenges while implementing alternative permutations of the recommended method transfer process.

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Membrane associated receptors can undergo shedding following cross-linking with ligand. B7RP-1 receptor is present on B-cells and macrophages and binds to the inducible costimulatory (ICOS) molecule on activated and memory T cells. ICOS binding can induce B7RP-1 receptor shedding. An electrochemiluminescence assay (ECLA) on the Meso Scale Discovery Sector Imager 6000 was validated to quantitate the soluble B7RP1 (sB7RP-1) levels in plasma from normal and Systemic Lupus Erythematosus (SLE) subjects. Comparing results of untreated samples or those pretreated with acetic acid enabled the detection of free sB7RP-1 and complexed sB7RP-1 (bound with ICOS or anti-B7RP-1 antibody). Using a bivalent Fc fused B7RP-1 receptor as the standard, the assay range was validated from 0.55 to 40 ng/mL with less than 30% total bias (%relative error plus %CV) at each level. Repeat measures of 51 subjects (normal and SLE) over day 1, 8, and 15 were analyzed. Utilizing the ratio of the sB7RP-1 levels quantified at day 8 or 15 compared to day 1 (post to pre), the natural variability between subjects and over time was statistically determined. No significant differences were noted between SLE and normal subjects, hence, the post to pre ratios were pooled and the range was set between 0.63 to 1.47, representing the 2.5% and 97.5% distributions, respectively. Hence, this assay can help monitor the extent of B7RP-1 shedding following ligand binding and it's potential to form an immunocomplex.