Overcoming anti-PEG antibody mediated accelerated blood clearance of PEGylated liposomes by pre-infusion with high molecular weight free PEG.

Antibodies that specifically bind polyethylene glycol (PEG), i.e. anti-PEG antibodies (APA), are associated with reduced efficacy and increased risk of serious adverse events for several PEGylated therapeutics. Here, we explored the concept of using free PEG molecules to saturate circulating APA. Surprisingly, we found that 40 kDa free PEG effectively restored the prolonged circulation of PEGylated liposomes in the presence of high titers of pre-existing APA for at least 48 h in mice. In contrast, lower molecular weight free PEG (≤10 kDa) failed to restore circulation beyond a few hours. These in vivo results were consistent with estimates from a minimal physiologically based pharmacokinetic model. Importantly, the infusion of free PEG appeared to be safe in mice previously sensitized by injection of PEGylated liposomes, and free PEG did not elicit excess APA production even in mice with pre-existing adaptive immunity against PEG. Our results support further investigation of high molecular weight free PEG as a potential method to control and overcome high titers of APA, restoring the prolonged circulation of PEGylated liposomes and possibly other PEGylated therapeutics.

Interstital lung disease in ANCA vasculitis.

Anti-neutrophil cytoplasmic antibodies (ANCA) vasculitides are immune-mediated disorders that primarily affect small blood vessels of the airway and kidneys. Lung involvement, one of the hallmarks of microscopic polyangiitis and granulomatosis with polyangiitis, is associated with increased mortality and morbidity. In recent years, several retrospective series and case reports have described the association of interstitial lung disease (ILD) and ANCA vasculitis, particularly those positive for ANCA specific for myeloperoxidase. In the majority of these patients pulmonary fibrosis occurs concurrently or predates the diagnosis of ANCA vasculitis. More importantly, these studies have shown that ILD has an adverse impact on the long-term prognosis of ANCA vasculitis. This review focuses on the main clinical and radiologic features of pulmonary fibrosis associated with anti-neutrophil cytoplasmic antibodies. Major histopathology features, prognosis and therapeutic options are summarized.

Overview of the Pathogenesis of ANCA-Associated Vasculitis.

BACKGROUND: Antineutrophil cytoplasmic autoantibodies (ANCA) are associated with a spectrum of necrotizing vasculitis including granulomatosis with polyangiitis, microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis, and renal-limited necrotizing and crescentic glomerulonephritis. Clinical observations and in vitro and in vivo experimental evidence strongly indicate that ANCA are pathogenic. SUMMARY: The etiology and pathogenesis of ANCA-associated vasculitis (AAV) are multifactorial, with contributions from genetic factors, environmental exposures, infections, characteristics of the innate and adaptive immune system, and the intensity and duration of the injury. Acute vascular inflammation is induced when resting neutrophils that have ANCA autoantigens sequestered in cytoplasmic granules are exposed to priming factors - for example, cytokines induced by infection or phlogogenic factors released by complement activation - that cause the release of ANCA antigens on the surface of neutrophils and in the microenvironment around the neutrophils. ANCA bind to these ANCA antigens, which activates neutrophils by Fcγ receptor engagement and F(ab')2 binding at the neutrophil cell surface. ANCA-activated neutrophils release factors that activate the alternative complement pathway, which generates C5a, a chemoattractant for neutrophils; C5a also primes the arriving neutrophils for activation by ANCA. Activated neutrophils adhere to and penetrate vessel walls, and they release toxic oxygen radicals and destructive enzymes that cause apoptosis and necrosis of the neutrophils as well as of the adjacent vessel wall cells and matrix. KEY MESSAGES: Patients with active AAV have ongoing asynchronous onsets of countless acute lesions, with each lesion evolving through stereotypical phases within 1 or 2 weeks. Induction of remission results in termination of new waves of acute lesions and allows all lesions to progress to scarring or resolution.

Genetically determined severity of anti-myeloperoxidase glomerulonephritis.

Myeloperoxidase (MPO) is a target antigen for antineutrophil cytoplasmic autoantibodies (ANCA). There is evidence that MPO-ANCA cause necrotizing and crescentic glomerulonephritis (NCGN) and vasculitis. NCGN severity varies among patients with ANCA disease, and genetic factors influence disease severity. The role of genetics in MPO-ANCA NCGN severity was investigated using 13 inbred mouse strains, F1 and F2 hybrids, bone marrow chimeras, and neutrophil function assays. Mouse strains include founders of the Collaborative Cross. Intravenous injection of anti-MPO IgG induced glomerular crescents in >60% of glomeruli in 129S6/SvEv and CAST/EiJ mice, but <1% in A/J, DBA/1J, DBA/2J, NOD/LtJ, and PWK/PhJ mice. C57BL6J, 129S1/SvImJ, LP/J, WSB/EiJ, NZO/HILtJ, and C3H mice had intermediate severity. High-density genotypes at 542,190 single nucleotide polymorphisms were used to identify candidate loci for disease severity by identifying genomic regions that are different between 129S6/SvEv and 129S1/SvImJ mice, which are genetically similar but phenotypically distinct. C57BL/6 × 129S6 F2 mice were genotyped at 76 SNPs to capture quantitative trait loci for disease severity. The absence of a dominant quantitative trait locus suggests that differences in severity are the result of multiple gene interactions. In vivo studies using bone marrow chimeric mice and in vitro studies of neutrophil activation by anti-MPO IgG indicated that severity of NCGN is mediated by genetically determined differences in the function of neutrophils.

Pathogenesis of antineutrophil cytoplasmic autoantibody-associated small-vessel vasculitis.

Clinical, in vitro, and experimental animal observations indicate that antineutrophil cytoplasmic autoantibodies (ANCA) are pathogenic. The genesis of the ANCA autoimmune response is a multifactorial process that includes genetic predisposition, environmental adjuvant factors, an initiating antigen, and failure of T cell regulation. ANCA activate primed neutrophils (and monocytes) by binding to certain antigens expressed on the surface of neutrophils in specific inflammatory microenvironments. ANCA-activated neutrophils activate the alternative complement pathway, establishing an inflammatory amplification loop. The acute injury elicits an innate inflammatory response that recruits monocytes and T lymphocytes, which replace the neutrophils that have undergone karyorrhexis during acute inflammation. Extravascular granulomatous inflammation may be initiated by ANCA-induced activation of extravascular neutrophils, causing tissue necrosis and fibrin formation, which would elicit an influx of monocytes that transform into macrophages and multinucleated giant cells. Over time, the neutrophil-rich acute necrotizing lesions cause the accumulation of more lymphocytes, monocytes, and macrophages and produce typical granulomatous inflammation.

A versatile adeno-associated virus vector producer cell line method for scalable vector production of different serotypes.

Application of adeno-associated virus (AAV) vector in large animal studies and clinical trials often requires high-titer and high-potency vectors. A number of currently used vector production methods, based on either transient transfection or helper virus infection of cell lines, have their advantages and limitations. We previously developed a 293-cell-based producer cell line method for high-titer and high-potency AAV2 vectors. Similar to several other methods, however, it requires multiple cloning steps for the vector and packaging plasmids and a two-step transfection and selection for stable cell lines. Here we report a simplified method with several key improvements and advantages: (1) a one-step cloning of AAV vector cassette into the serotype-specific packaging plasmid; (2) a single plasmid transfection and selection for stable AAV vector producer cell lines; (3) high vector yields of different serotypes, e.g., AAV2, 8, and 9, upon infection with an E1A/E1B-deleted helper adenovirus; (4) efficient packaging of both single-stranded and double-stranded (self-complementary) AAV vectors; and (5) efficient packaging of large AAV cassettes such as a mini-dystrophin vector (5.0 kb). All cell lines were stable with growth rates identical to the parental 293 cells. The vector yields were consistent among serotypes, with 5 × 10(13) to 8 × 10(13) vector genome particles per Nunc cell factory (equivalent to 40 15-cm plates). The vectors showed high potency for in vitro and in vivo transduction. In conclusion, the simple and versatile AAV producer cell line method can be useful for large scale AAV vector production in preclinical and clinical studies.

The role of neutrophils in the induction of glomerulonephritis by anti-myeloperoxidase antibodies.

In humans, circulating anti-neutrophil cytoplasm autoantibodies (ANCAs) with specificity for myeloperoxidase (MPO) are strongly associated with the development of pauci-immune necrotizing and crescentic glomerulonephritis (NCGN). In mice, we have demonstrated that intravenous injection of mouse antibodies specific for mouse MPO induces NCGN that closely mimics the human disease. We now report that the development of NCGN in this experimental model is accompanied by glomerular accumulation of neutrophils and macrophages. Neutrophil infiltration was most conspicuous at sites of glomerular necrosis and crescent formation, with macrophages also most numerous in crescents. Lymphocytes, however, were sparse in acute lesions. Importantly, mice that were depleted of circulating neutrophils with NIMP-R14 rat monoclonal antibodies were completely protected from anti-MPO IgG-induced NCGN. These findings provide direct evidence that neutrophils play a major role in the pathogenesis of anti-MPO-induced NCGN in this animal model and implicate neutrophils in the induction of human ANCA disease. This raises the possibility that therapeutic strategies to reduce circulating neutrophils could be beneficial to patients with ANCA-induced NCGN.

Antineutrophil cytoplasmic autoantibodies specific for myeloperoxidase cause glomerulonephritis and vasculitis in mice.

Antineutrophil cytoplasmic autoantibodies (ANCAs) are identified in the circulation of approximately 80% of patients with pauci-immune necrotizing and crescentic glomerulonephritis and systemic small vessel vasculitis, such as microscopic polyangiitis and Wegener granulomatosis. The most common antigen target for ANCAs is myeloperoxidase (MPO), which is found in neutrophils and monocytes. We report definitive experimental animal evidence that ANCAs are pathogenic. MPO knockout (Mpo(-/-)) mice were immunized with mouse MPO. Splenocytes from these mice or from control mice were injected intravenously into recombinase-activating gene-2-deficient (Rag2(-/-)) mice, which lack functioning B lymphocytes and T lymphocytes. All mice that received splenocytes developed mild to moderate glomerular immune deposits, but only mice that received 1 x 10(8) or 5 x 10(7) anti-MPO splenocytes developed severe necrotizing and crescentic glomerulonephritis, granulomatous inflammation, and systemic necrotizing vasculitis, including necrotizing arteritis and hemorrhagic pulmonary capillaritis. To test the pathogenic potential of antibodies alone, purified anti-MPO IgG or control IgG was injected intravenously into Rag2(-/-) mice and wild-type mice. Mice that received anti-MPO IgG but not mice that received control IgG developed focal necrotizing and crescentic glomerulonephritis with a paucity of glomerular Ig deposition. Thus, anti-MPO IgG alone was able to cause pauci-immune glomerular necrosis and crescent formation in the absence of functional T or B lymphocytes in Rag2(-/-) mice and in the presence of an intact immune system in wild-type C57BL/6J mice. This animal model offers strong support for a direct pathogenic role for ANCA IgG in human glomerulonephritis and vasculitis.