Objective To assess the safety and efficacy of rituximab in a randomized, double-blind, placebo-phase, trial of adult and pediatric myositis. Methods Adults with refractory polymyositis and adults and children with refractory dermatomyositis were enrolled. Entry criteria included muscle weakness and ≥2 additional abnormal core set measures (CSM) for adults. JDM patients required ≥ 3 abnormal CSM with or without muscle weakness. Patients were randomized to either ‘rituximab early’ or ‘rituximab late’ and glucocorticoid and immunosuppressive therapy were allowed at entry. The primary endpoint compared the time to achieve the preliminary International Myositis Assessment and Clinical Studies Group definition of improvement (DOI) between the 2 groups. The secondary endpoints were time to achieve ≥20% improvement in muscle strength, and the proportion of early and late rituximab patients achieving DOI at week 8. Results Among 200 randomized patients (76 PM/76 DM/48 JDM), 195 showed no difference in the time to DOI between the rituximab late (n=102) and rituximab early (n=93) groups (p=0.74, log rank) with a median time to DOI of 20.2 weeks and 20.0 weeks respectively. The secondary endpoints also did not significantly differ between the two treatment groups. However, 161 (83%) of randomized patients met the DOI and individual CSM improved in both groups throughout the 44-week trial. Conclusion Although there were no significant differences in the two treatment arms for the primary and secondary endpoints, 83% of refractory adult and juvenile myositis patients met the DOI. The role of B cell depleting therapies in myositis warrants further study with consideration for a different trial design.

Defining human B cell repertoires to viral pathogens is critical for design of vaccines that induce broadly protective antibodies to infections such as HIV-1 and influenza. Single B cell sorting and cloning of immunoglobulin (Ig) heavy- and light-chain variable regions (VH and VL) is a powerful technology for defining anti-viral B cell repertoires. However, the Ig-cloning step is time-consuming and prevents high-throughput analysis of the B cell repertoire. Novel linear Ig heavy- and light-chain gene expression cassettes were designed to express Ig VH and VL genes isolated from sorted single B cells as IgG1 antibody without a cloning step. The cassettes contain all essential elements for transcriptional and translational regulation, including CMV promoter, Ig leader sequences, constant region of IgG1 heavy- or Ig light-chain, poly(A) tail and substitutable VH or VL genes. The utility of these Ig gene expression cassettes was established using synthetic VH or VL genes from an anti-HIV-1 gp41 mAb 2F5 as a model system, and validated further using VH and VL genes isolated from cloned EBV-transformed antibody-producing cell lines. Finally, this strategy was successfully used for rapid production of recombinant influenza mAbs from sorted single human plasmablasts after influenza vaccination. These Ig gene expression cassettes constitute a highly efficient strategy for rapid expression of Ig genes for high-throughput screening and analysis without cloning.

Patients with IPF with anti-HSP70 autoantibodies have more near-term lung function deterioration and mortality. These findings suggest antigen-specific immunoassays could provide useful clinical information in individual patients with IPF and may have implications for understanding IPF progression.

Studying the effects of early HIV infection on human antibody responses, M. Anthony Moody and colleagues find rapid polyclonal B cell differentiation and structural damage to gut-associated lymphoid tissue.

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Acyl-coenzyme A:cholesterol acyltransferase (ACAT)is an integral membrane protein located in the endoplasmic reticulum. It catalyzes the formation of cholesteryl esters from cholesterol and long-chain fatty acyl coenzyme A. The first gene encoding the enzyme, designated as ACAT-1, was identified in 1993 through an expression cloning approach. We isolated a Chinese hamster ovary cell line that stably expresses the recombinant human ACAT-1 protein bearing an N-terminal hexahistidine tag. We purified this enzyme approximately 7000-fold from crude cell extracts by first solubilizing the cell membranes with the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, then proceeding with an ACAT-1 monoclonal antibody affinity column and an immobilized metal affinity column. The final preparation is enzymologically active and migrates as a single band at 54 kDa on SDS-polyacrylamide gel electrophoresis. Pure ACAT-1 dispersed in mixed micelles containing sodium taurocholate, phosphatidylcholine, and cholesterol remains catalytically active. The cholesterol substrate saturation curves of the enzyme assayed either in mixed micelles or in reconstituted vesicles are both highly sigmoidal. The oleoyl-coenzyme A substrate saturation curves of the enzyme assayed under the same conditions are both hyperbolic. These results support the hypothesis that ACAT is an allosteric enzyme regulated by cholesterol. Specific polyclonal anti-ACAT-1 IgGs have been produced (19 -21). Immunoblot and immunodepletion analyses show that the ACAT-1 protein is present in homogenates from various human cells and tissues as a single 50-kDa protein band in SDS-PAGE (19) Furthermore, immunodepletion experiments using anti-ACAT-1 IgGs suggest that the ACAT-1 protein plays a major role in ACAT catalysis in human fibroblasts, HepG2 cells, human hepatocytes, macrophages, adrenal glands, and kidneys (22). In contrast, in human intestines, approximately 80% of total measurable ACAT activity is resistant to immunodepletion, suggesting that ACAT activity in this particular tissue may be largely due to the presence of a different ACAT protein (22). Judging from results currently available, it is possible that the physiological functions of ACAT-1 and ACAT-2 are different in different species. Whether ACAT-2 is responsible for most of the observed ACAT activity in human intestines is not clear at present. Acyl-coenzymeThe ACAT protein has never before been purified to homogeneity. The difficulty in doing so was largely due to its minute quantity and the lack of a suitable detergent for solubilizing the protein from the endoplasmic reticulum membrane with retention of enzyme activity (reviewed in Ref. 5). As described in this article, we have isolated a CHO cell line (HisACAT-1 cells) that stably expresses the human ACAT-1 (hACAT-1) protein bearing a hexahistidine tag at its N terminus. We report the use of this cell line as the starting material to develop a purification scheme that enables us to purify the enzyme to essential homogenei...

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We hypothesized B-cells are involved in the pathogenesis of idiopathic pulmonary fibrosis (IPF), a progressive, restrictive lung disease that is refractory to glucocorticoids and other nonspecific therapies, and almost invariably lethal. Accordingly, we sought to identify clinically-associated B-cell-related abnormalities in these patients. Phenotypes of circulating B-cells were characterized by flow cytometry. Intrapulmonary processes were evaluated by immunohistochemistry. Plasma B-lymphocyte stimulating factor (BLyS) was assayed by ELISA. Circulating B-cells of IPF subjects were more antigen-differentiated, with greater plasmablast proportions (3.1±0.8%) than in normal controls (1.3±0.3%) (p<0.03), and the extent of this differentiation correlated with IPF patient lung volumes (r=0.44, p<0.03). CD20+ B-cell aggregates, diffuse parenchymal and perivascular immune complexes, and complement depositions were all prevalent in IPF lungs, but much less prominent or absent in normal lungs. Plasma concentrations of BLyS, an obligate factor for B-cell survival and differentiation, were significantly greater (p<0.0001) in 110 IPF (2.05±0.05 ng/ml) than among 53 normal (1.40±0.04 ng/ml) and 90 chronic obstructive pulmonary disease (COPD) subjects (1.59±0.05 ng/ml). BLyS levels were uniquely correlated among IPF patients with pulmonary artery pressures (r=0.58, p<0.0001). The 25% of IPF subjects with the greatest BLyS values also had diminished one-year survival (46±11%), compared to those with lesser BLyS concentrations (81±5%) (HR=4.0, 95%CI=1.8-8.7, p=0.0002). Abnormalities of B-cells and BLyS are common in IPF patients, and highly associated with disease manifestations and patient outcomes. These findings have implications regarding IPF pathogenesis, and illuminate the potential for novel treatment regimens that specifically target B-cells in patients with this lung disease.