Ashley Frazer-Abel

Patients with Nontuberculous Mycobacterial Lung Disease Exhibit Unique Body and Immune Phenotypes

RATIONALE Among patients with nontuberculous mycobacterial lung disease is a subset of previously healthy women with a slender body morphotype, often with scoliosis and/or pectus excavatum. We hypothesize that unidentified factors predispose these individuals to pulmonary nontuberculous mycobacterial disease. OBJECTIVES To compare body morphotype, serum adipokine levels, and whole-blood cytokine responses of patients with pulmonary nontuberculous mycobacteria (pNTM) with contemporary control subjects who are well matched demographically. METHODS We enrolled 103 patients with pNTM and 101 uninfected control subjects of similar demographics. Body mass index and body fat were quantified. All patients with pNTM and a subset of control subjects were evaluated for scoliosis and pectus excavatum. Serum leptin and adiponectin were measured. Specific cytokines important to host-defense against mycobacteria were measured in whole blood before and after stimulation. MEASUREMENTS AND MAIN RESULTS Patients with pNTM and control subjects were well matched for age, gender, and race. Patients with pNTM had significantly lower body mass index and body fat and were significantly taller than control subjects. Scoliosis and pectus excavatum were significantly more prevalent in patients with pNTM. The normal relationships between the adipokines and body fat were lost in the patients with pNTM, a novel finding. IFN-γ and IL-10 levels were significantly suppressed in stimulated whole blood of patients with pNTM. CONCLUSIONS This is the first study to comprehensively compare body morphotype, adipokines, and cytokine responses between patients with NTM lung disease and demographically matched controls. Our findings suggest a novel, predisposing immunophenotype that should be mechanistically defined.

Canine malignant hemangiosarcoma as a model of primitive angiogenic endothelium

Hemangiosarcoma (HSA) is a common untreatable cancer of dogs that resembles human angiosarcoma. Detailed studies of these diseases have been historically hindered by the paucity of suitable reagents. Here, we show that expression of CD117 (c-Kit) can distinguish primitive (malignant) from mature (benign) proliferative endothelial lesions, and we describe eight independent cell lines derived from canine HSA explants. Endothelial origin was confirmed by sustained expression of surface CD105 (endoglin), CD146 (MUC18), and CD51/CD61 (αvβ3 integrin). The cell lines showed anchorage-independent growth and were motile and invasive when cultured on a basement membrane matrix. They required endothelial growth factors for growth and survival, and they could be induced to form tubular structures resembling blood vessels when cultured under low calcium conditions. The formation of vessel-like structures was blocked by nicotine, and restored by FK506, suggesting that ‘nuclear factor of activated T cells’ activity prevents differentiation of these cells. In summary, these cell lines represent a unique and novel resource to improve our understanding of endothelial cell biology in general and canine HSA in particular.

Mechanistic Understanding for the Greater Sensitivity of Monkeys to Antisense Oligonucleotide–Mediated Complement Activation Compared with Humans

Differences in sensitivity of monkeys and humans to antisense oligonucleotide (ASO)–induced complement alternative pathway (AP) activation were evaluated in monkeys, humans, and in serum using biochemical assays. Transient AP activation was evident in monkeys at higher doses of two 2′-O-methoxyethyl (2′-MOE) ASOs (ISIS 426115 and ISIS 183750). No evidence of AP activation was observed in humans for either ASO, even with plasma ASO concentrations that reached the threshold for activation in monkeys. The absence of complement activation in humans is consistent with a query of the Isis Clinical Safety Database containing 767 subjects. The in vivo difference in sensitivity was confirmed in vitro, as monkey and human serum exposed to increasing concentrations of ASO indicated that monkeys were more sensitive to AP activation with this class of compounds. The mechanistic basis for the greater sensitivity of monkeys to AP activation by 2′-MOE ASO was evaluated using purified human or monkey factor H protein. The binding affinities between a representative 2′-MOE ASO and either purified protein are similar. However, the IC50 of fluid-phase complement inhibition for monkey factor H is about 3-fold greater than that for human protein using either monkey serum or factor H–depleted human serum. Interestingly, there is a sequence variant in the monkey complement factor H gene similar to a single nucleotide polymorphism in humans that is correlated with decreased factor H protein function. These findings show that monkeys are more sensitive to 2′-MOE ASO–mediated complement activation than humans likely because of differences in factor H inhibitory capacity.

Update on laboratory tests for the diagnosis and differentiation of hereditary angioedema and acquired angioedema.

The importance of laboratory testing in the diagnosis of hereditary angioedema (HAE) has increased with the advent of new treatment options in recent years. It has been 50 years since HAE was linked to a decrease of C1INH (the inhibitor of complement enzyme, C1 esterase), a link that provided for the first laboratory test available for this disorder. HAE is subdivided into types that can be differentiated only by laboratory testing. The Type I form is characterized by low levels and function of C1INH in the circulation. The Type II form is characterized by normal levels of C1INH, but low function. Sample collection and handling is critical for the functional assays. The serum samples for the functional analysis must be collected, separated, and frozen at less than -60°C within 2 hours of the blood draw. Additionally some suspected Type II patients may benefit from looking closely at what method is used for the functional testing. The acquired forms of angioedema (AAE) can benefit from the same clinical testing, because most are ultimately due to decreased C1INH. Measurement of C1q levels and testing for anti-C1INH autoantibodies can help differentiate AAE from HAE. Diagnostic testing for the third hereditary form, alternately called estrogen-dependent HAE, HAE with Normal C1INH or HAE Type III, still presents challenges, and definitive testing may have to wait until there is a more complete understanding of this mixed group of patients. The next steps will include genetic analysis of C1INH and other proteins involved in HAE.

Nicotine-mediated signals modulate cell death and survival of T lymphocytes

The capacity of nicotine to affect the behavior of non-neuronal cells through neuronal nicotinic acetylcholine receptors (nAChRs) has been the subject of considerable recent attention. Previously, we showed that exposure to nicotine activates the nuclear factor of activated T cells (NFAT) transcription factor in lymphocytes and endothelial cells, leading to alterations in cellular growth and vascular endothelial growth factor production. Here, we extend these studies to document effects of nicotine on lymphocyte survival. The data show that nicotine induces paradoxical effects that might alternatively enforce survival or trigger apoptosis, suggesting that depending on timing and context, nicotine might act both as a survival factor or as an inducer of apoptosis in normal or transformed lymphocytes, and possibly other non-neuronal cells. In addition, our results show that, while having overlapping functions, low and high affinity nAChRs also transmit signals that promote distinct outcomes in lymphocytes. The sum of our data suggests that selective modulation of nAChRs might be useful to regulate lymphocyte activation and survival in health and disease.

Complement Activation in Patients with Focal Segmental Glomerulosclerosis

Background Recent pre-clinical studies have shown that complement activation contributes to glomerular and tubular injury in experimental FSGS. Although complement proteins are detected in the glomeruli of some patients with FSGS, it is not known whether this is due to complement activation or whether the proteins are simply trapped in sclerotic glomeruli. We measured complement activation fragments in the plasma and urine of patients with primary FSGS to determine whether complement activation is part of the disease process. Study Design Plasma and urine samples from patients with biopsy-proven FSGS who participated in the FSGS Clinical Trial were analyzed. Setting and Participants We identified 19 patients for whom samples were available from weeks 0, 26, 52 and 78. The results for these FSGS patients were compared to results in samples from 10 healthy controls, 10 patients with chronic kidney disease (CKD), 20 patients with vasculitis, and 23 patients with lupus nephritis. Outcomes Longitudinal control of proteinuria and estimated glomerular filtration rate (eGFR). Measurements Levels of the complement fragments Ba, Bb, C4a, and sC5b-9 in plasma and urine. Results Plasma and urine Ba, C4a, sC5b-9 were significantly higher in FSGS patients at the time of diagnosis than in the control groups. Plasma Ba levels inversely correlated with the eGFR at the time of diagnosis and at the end of the study. Plasma and urine Ba levels at the end of the study positively correlated with the level of proteinuria, the primary outcome of the study. Limitations Limited number of patients with samples from all time-points. Conclusions The complement system is activated in patients with primary FSGS, and elevated levels of plasma Ba correlate with more severe disease. Measurement of complement fragments may identify a subset of patients in whom the complement system is activated. Further investigations are needed to confirm our findings and to determine the prognostic significance of complement activation in patients with FSGS.

Review: The Evolving Landscape for Complement Therapeutics in Rheumatic and Autoimmune Diseases

The complement system is increasingly understood to play major roles in the pathogenesis of human inflammatory and autoimmune diseases. Because of this situation, there are rapidly expanding commercial efforts to develop novel complement inhibitors and effector pathway–modulating drugs. This review provides insights into the evolving understanding of the complement system components, mechanisms of activation within and across the 3 pathways (classical, alternative, and lectin), how the pathways are normally controlled and then dysregulated in target tissues, and what diseases are known to be, in large part, complement‐dependent through the successful development and approval of complement therapeutics in patients. Mechanisms of complement activation in rheumatoid arthritis, lupus, and thrombotic microangiopathies are also illustrated. In addition, the specific therapeutic drugs that are both approved and under development are discussed in the context of both nonrheumatic and rheumatic diseases. Finally, the methods by which the complement system can be assessed in humans through biomarker studies are outlined, with the goal of understanding, in specific patients, how the system is functioning.

The effect on the immunology laboratory of the expansion in complement therapeutics

The approval in the US and Europe of Eculizumab in 2007 marked a change in complement therapeutics, and with it the landscape for complement testing in the clinical immunology laboratory changed. The change had begun even before that when C1-Inhibitor preparations were approved in the 1980s in Europe. There are now two classes of approved drugs that may impact the immunology laboratory, with two dozen more with novel modalities and potential indications that are in various stages of development. Every pathway and about every component of complement has been targeted by these drug development programs, and the modalities of the drugs in development are diverse. These developments will likely result in more laboratories offering more complement testing, so this review looks forward to some of those possible changes in testing.