A comparison of biofluid cytokine markers across platform technologies: Correspondence or divergence?

BACKGROUND

Quantification of biofluid cytokines is a rapidly growing area of translational research. However, comparability across the expanding number of available assay platforms for detection of the same proteins remains to be determined. We aimed to directly compare a panel of commonly measured cytokines in plasma of typically aging adults across two high sensitivity quantification platforms, Meso Scale Discovery high performance electrochemiluminiscence (HPE) and single-molecule immunosorbent assays (Simoa) by Quanterix.

METHODS

57 community-dwelling older adults completed a blood draw, neuropsychological assessment, and brain MRI as part of a healthy brain aging study. Plasma samples from the same draw dates were analyzed for IL-10, IP-10, IL-6, TNFα, and IL-1β on HPE and Simoa, separately. Reliable detectability (coefficient of variance (CV) < 20% and outliers 3 interquartiles above the median removed), intra-assay precision, absolute concentrations, reproducibility across platforms, and concurrent associations with external variables of interest (e.g., demographics, peripheral markers of vascular health, and brain health) were examined.

RESULTS

The proportion of cytokines reliably measured on HPE (87.7-93.0%) and Simoa (75.4-93.0%) did not differ (ps > 0.32), with the exception of IL-1β which was only reliably measured using Simoa (68.4%). On average, CVs were acceptable at <8% across both platforms. Absolute measured concentrations were higher using Simoa for IL-10, IL-6, and TNFα (ps < 0.05). HPE and Simoa shared only small-to-moderate proportions of variance with one another on the same cytokine proteins (range: r = 0.26 for IL-10 to r = 0.64 for IL-6), though platform agreement did not dependent on cytokine concentrations. Cytokine ratios within each platform demonstrated similar relative patterns of up- and down-regulation across HPE and Simoa, though still significantly differed (ps < 0.001). Supporting concurrent validity, all 95% confidence intervals of the correlations between cytokines and external variables overlapped between the two platforms. Moreover, most associations were in expected directions and consistently so across platforms (e.g., IL-6 and TNFα), though with several notable exceptions for IP-10 and IL-10.

CONCLUSIONS

HPE and Simoa showed comparable detectability and intra-assay precision measuring a panel of commonly examined cytokine proteins, with the exception of IL-1β which was not reliably detected on HPE. However, Simoa demonstrated overall higher concentrations and the two platforms did not show agreement when directly compared against one another. Relative cytokine ratios and associations demonstrated similar patterns across platforms. Absolute cytokine concentrations may not be directly comparable across platforms, may be analyte dependent, and interpretation may be best limited to discussion of relative associations.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Whole-genome sequencing suggests a chemokine gene cluster that modifies age at onset in familial Alzheimer's disease

We have sequenced the complete genomes of 72 individuals affected with early-onset familial Alzheimer's disease caused by an autosomal dominant, highly penetrant mutation in the presenilin-1 (PSEN1) gene, and performed genome-wide association testing to identify variants that modify age at onset (AAO) of Alzheimer's disease. Our analysis identified a haplotype of single-nucleotide polymorphisms (SNPs) on chromosome 17 within a chemokine gene cluster associated with delayed onset of mild-cognitive impairment and dementia. Individuals carrying this haplotype had a mean AAO of mild-cognitive impairment at 51.0 ± 5.2 years compared with 41.1 ± 7.4 years for those without these SNPs. This haplotype thus appears to modify Alzheimer's AAO, conferring a large (~10 years) protective effect. The associated locus harbors several chemokines including eotaxin-1 encoded by CCL11, and the haplotype includes a missense polymorphism in this gene. Validating this association, we found plasma eotaxin-1 levels were correlated with disease AAO in an independent cohort from the University of California San Francisco Memory and Aging Center. In this second cohort, the associated haplotype disrupted the typical age-associated increase of eotaxin-1 levels, suggesting a complex regulatory role for this haplotype in the general population. Altogether, these results suggest eotaxin-1 as a novel modifier of Alzheimer's disease AAO and open potential avenues for therapy.

Increased nitric oxide accounts for decreased basal vascular tone and responsiveness in the resistance vessels of high-cholesterol-fed rabbits

The objective of this study was to determine the effects of hypercholesterolemia on basal vascular tone and vascular responses to pharmacologic agents in hindquarter resistance vessels. Blood pressure and hindquarter blood flow were measured in conscious rabbits fed a high cholesterol diet (1%) for 17 weeks (HC) compared to age-matched rabbits fed a normal diet (control). Basal hindquarter blood flow and vascular conductance were significantly higher in HC than in control rabbits. Administration of a non-selective nitric oxide synthase (NOS) inhibitor, L-NAME (100 mg/kg) decreased basal hindquarter blood flow and vascular conductance in a greater magnitude in HC than in control rabbits, thus, abolished the differences in both the flow and conductance between 2 groups, indicating that increased NO was responsible for reduced basal vascular tone in the HC rabbits. L-NIL (30 mg/kg), a selective inducible NOS (iNOS) inhibitor had no effects on either flow or conductance. This result does not support the involvement of iNOS. In separate experiments, animals were anesthetized and instrumented with an extracorporeal circuit to measure perfusion pressure under constant blood flow to the hindquarter vascular bed. In the HC group, vascular responses to acetylcholine, S-nitroso-N-acetyl-penicillamine and phenylephrine were all attenuated when compared to the responses in the control rabbits. These results indicate that local overproduction of NO due to hypercholesteremia could desensitize smooth muscle reactivity, thus causing general vascular hyporesponsiveness to vasoactive agents.

Role of endogenous nitric oxide in progression of atherosclerosis in apolipoprotein E-deficient mice

This study investigated the role of endogenous nitric oxide (NO) in the progression of atherosclerosis in apolipoprotein E-deficient [apoE-knockout (KO)] mice. Mice were treated with N(omega)-nitro-L-arginine methyl ester (L-NAME) an inhibitor of nitric oxide synthase (NOS) or with the NOS substrate L-arginine for 8 wk. L-NAME treatment resulted in a significant inhibition of NO-mediated vascular responses and a significant increase in the atherosclerotic plaque/surface area in the aorta of apoE-KO mice. L-arginine treatment had no influence on endothelial function and did not alter lesion size. Mean arterial blood pressure and serum lipid levels were not altered by the treatments. At the beginning of the study impairment in endothelial function was only apparent in the case of N(G)-nitro-L-arginine-induced, NO-mediated contraction, whereas ACh-induced, NO-mediated relaxation was not different between age-matched apoE-KO and C57Bl/6J mice. After the 8-wk treatment with the NOS inhibitor, both NO-mediated responses were significantly inhibited. The acceleration in lesion size concomitant to the severely impaired NO-mediated responses indicates that lack of endogenous NO is an important progression factor of atherosclerosis in the apoE-KO mouse.

Increased aortic stiffness assessed by pulse wave velocity in apolipoprotein E-deficient mice

Atherosclerosis develops and progresses spontaneously in apolipoprotein E-knockout (apoE-KO) mice. A direct consequence of atherosclerosis is an increase in vascular stiffness. Pulse wave velocity (PWV) has been used to assess the stiffness of large vessels and was found to be increased in patients with atherosclerosis. In the present study, aortic stiffness was assessed by PWV in 4- and 13-mo-old apoE-KO mice and age-matched controls (C57BL/6J). In 13-mo-old apoE-KO mice with extensive atherosclerotic lesions in the aorta (61 +/- 4%), PWV increased significantly (3.8 +/- 0.2 m/s) compared with controls (2.9 +/- 0.2 m/s). Endothelial nitric oxide (EDNO)-mediated vasorelaxation in response to ACh was markedly diminished in the aortic rings isolated from 13-mo-old apoE-KO mice compared with age-matched controls. In contrast, in 4-mo-old apoE-KO mice with only moderate atherosclerotic lesions in the aorta (23 +/- 5%), there were no significant changes in PWV and EDNO-mediated relaxation compared with controls. Blood pressure was not different among the four groups of mice. There were no significant differences in endothelium-independent vascular responses to sodium nitroprusside among different groups investigated. Histological evaluation revealed focal fragmentation of the elastic laminae in the aortic walls of 13-mo-old apoE-KO mice. These results demonstrate for the first time that aortic stiffness determined by PWV increases in 13-mo-old apoE-KO mice. Endothelial dysfunction and elastic destruction in vascular wall caused by atherosclerosis may have contributed.

Preliminary experience with a combined-modality approach to the management of oesophageal cancer

A synchronous chemoradiotherapy schedule of modest dosage has been used in 36 patients with oesophageal cancer since July 1984 at the Royal Adelaide Hospital. The schedule, which comprises two five-day continuous infusions of 5-fluorouracil, each of which is followed by a short cisplatin infusion, together with 30-35 Gy of megavoltage irradiation over three weeks, has been used alone, or before surgical resection or further chemo-irradiation. It has been extremely well tolerated and has caused complete endoscopic resolution of disease before surgery or further chemo-irradiation in 69% of patients. At the end of the full course of treatment, complete relief of dysphagia has been achieved in 27 (84%) of the 32 patients in whom this symptom was present at the start of treatment. The median duration of relief has not yet been reached with a median follow-up of over one year. This degree of palliation is significantly better than that which was achieved in a series of patients who were treated radically either by surgery or radiation alone between the years 1978 and 1983 at the Royal Adelaide Hospital. The 12- and 18-month actuarial survival figures of 72% and 55%, respectively, for the 30 patients in this series whose disease remained apparently localized to the thorax at presentation, compare very favourably with the corresponding figures for the much more highly-selected group of patients who were treated surgically between 1978 and 1983.

Stability of oestrogen receptor status in sequential biopsies from patients with breast cancer

Sequential biopsies of breast cancer tissue were obtained from a total of 210 women in order to assess any change in oestrogen receptor (ER) status arising spontaneously or as a result of intervening therapy. A combined assay measuring both cytosol and nuclear oestrogen receptors was used for all samples. One hundred and fifty-five patients had biopsies of their primary tumour and of a later loco-regional recurrence; 26 had biopsies of their primary tumour and a recurrence or new primary in the opposite breast; and 29 had sequential biopsies of recurrent disease only. Overall only 61.2% of the primary tumours retained their original status with respect to both cytosol and nuclear oestrogen receptors on recurrence. These results were influenced by intervening therapy, however, and if only untreated patients are considered, over 70% of their recurrences contain the same combination of cytosol and nuclear receptors as found in the primary tumours. For tumours 'recurring' in the opposite breast, the pattern was similar with 69.2% retaining the same status as the first primary. The agent found most likely to alter I:R status was tamoxifen and in the samples taken from patients undergoing treatment with this drug, no tumour was found to contain measurable receptor.

Effects on the rabbit carotid body of stimulation by almitrine, natural high altitude, and experimental normobaric hypoxia

Rabbits were given intraperitoneal injections of almitrine in ascending doses for 5 weeks. They were compared with a control group and with a group of rabbits which had been exposed from birth to the natural hypobaric hypoxia found at Cerro de Pasco (433 m) in the Peruvian Andes. A further group of animals was placed in an experimental normobaric chamber for either 3 or 6 months to subject them to the same degree of hypoxia as that occurring in Cerro. The carotid bodies of the rabbits in all these groups were processed for light and electron microscopy, and examined both qualitatively and quantitatively. The carotid bodies in the group given almitrine showed no changes in their size or in the population of their glomic cells when compared with controls. In contrast, the carotid bodies of Peruvian rabbits were greatly enlarged with a disproportionate increase in the population of the light variant of chief cell. Rabbits from the hypoxic chamber also had enlarged carotid bodies but those killed after 3 months showed an increase in the dark variant of chief cell, whereas after 6 months this cell was reduced in number. There was also intense cytoplasmic vacuolation. Election microscopy confirmed these changes and revealed that dark cells had larger, more pleomorphic granules than the light variant. Vacuolation of the granules in light cells was most pronounced in Peruvian rabbits, but was uncommon in animals exposed to hypoxia for 3 months. We suggest that the dark cell responds to the early stages of hypoxia but later matures into the light variant of chief cell.

Comparative pathology of the enlarged carotid body

A histological study was made of the carotid bodies of man and various animal species from low and high altitudes. The animals studied were the alpaca, llama, cattle, guinea-pig, rabbit, dog, rat and man. As well as a qualitative microscopic study, a differential cell count was carried out to determine the percentage of the light and dark variants of chief cells and of sustentacular cells present. The investigation showed that the carotid bodies enlarge in cattle, guinea-pigs and rabbits living in the hypobaric hypoxia of high altitude to which they have to acclimatize. The carotid bodies are not enlarged in llamas and alpacas which show Darwinian adaptation to high altitude. There is no single histopathological appearance to be found with enlargement of the carotid body; on the contrary, there appears to be a characteristic histological reaction for different species. Thus, man shows hyperplasia of sustentacular cells, cattle show focal dark cell proliferation and rabbits, guinea-pigs, and dogs show striking hyperplasia and vacuolation of chief cells. In the rat, the enlargement of the carotid body is not characterized by the differential proliferation of any specific element and, as a result, it does not appear to be a good model for the human organ. In man and rat, carotid body enlargement occurs in response to systemic hypertension as well as to chronic hypoxaemia and the histological response to the 2 stimuli is the same, depending on the species. The normal rabbit carotid body is more reminiscent of that of man but, in this species, the reaction of glomic tissue differs from that of human glomic tissue.

Nerve axons in carotid body hyperplasia. A quantitative study

The nerve density, expressed as total length of nerve fibers per square millimeter of tissue section, was measured in both carotid bodies from five subjects free from cardiopulmonary disease and from eight subjects with carotid body hyperplasia. Six of the cases with enlargement of the carotid body had been exposed to chronic hypoxemia in life (due to panacinar pulmonary emphysema in five instances and the pickwickian syndrome in one case), and the other two cases had had systemic hypertension. The cases of carotid body hyperplasia showed an increased nerve density associated with the characteristic proliferation of elongated cells. These findings confirm that the proliferating cells in carotid body hyperplasia are both sustentacular and Schwann's cells, not fibroblasts, and suggest that these cells develop to support an increased number of nerve axons. The mechanisms by which two such different stimuli as chronic hypoxemia and raised intravascular pressure bring about an increased nerve density are obscure.

The value of endoscopy and biopsy in the diagnosis of gastric carcinoma

The value of endoscopy and biopsy in the diagnosis of gastric carcinoma has been examined. Out of a total of 550 patients, gastric carcinoma was suspected in 101. Endoscopy and biopsy provided a firm diagnosis in 43 of the 44 cases of gastric carcinoma present, and effectively excluded gastric carcinoma in 48 cases. We recommend endoscopy and biopsy as valuable diagnostic procedures in the investigation of patients suspected of having gastric carcinoma. Used together they can eliminate the necessity for diagnostic laparotomy.