Revisiting the dilution factor as vital parameter for sensitivity of ELISA assay in CSF and Plasma

Semi-quantitative, high throughput analysis of SARS-CoV-2 neutralizing antibodies: Measuring the level and duration of immune response antibodies post infection/vaccination

The question associated with efficacy and longevity of SARS-CoV-2 protection post-vaccination is paramount. The cPass surrogate virus neutralization test (sVNT) has gained popularity globally as a dual application assay for: 1. Accurate SARS-CoV-2 population surveillance (seroprevalence) analysis and 2. Revealing the presence of antibodies that block and effectively neutralize the interaction between the SARS-CoV-2 receptor binding domain and the host cell ACE2 receptor in recovered or vaccinated individuals. This study describes an approach for accurate quantification of neutralizing antibodies using the cPass sVNT with an automated workflow on the Tecan EVO and Dynex Agility platforms that is applicable to other liquid handling systems. This methodology was used to assess the stability of SARS-CoV-2 neutralizing antibodies between freeze/thaw and refrigerated sample storage conditions. Furthermore, a subset of twenty-five samples from SARS-CoV-2 infected/recovered individuals revealed a 600-fold difference in the neutralizing antibody response where low titers were represented in about half of the samples. Finally, pre- and post-vaccination samples were tested for neutralizing antibodies using the qualitative and semi-quantitative cPass sVNT protocols revealing undetectable or relatively low levels after the first vaccine dose and a decline in levels longitudinally over the months following the second dose. This wide range in neutralizing (blocking) antibodies from both natural infection and vaccination supports a differential immune response that may be attributed to several physiological and genetic factors underlining the potential for measuring SARS-CoV-2 neutralizing antibody titer levels post-vaccination to help ensure robust and prolonged immunity.

Apolipoproteins A1 and B and their ratio in acute ischemic stroke patients with intracranial and extracranial arterial stenosis: an Egyptian study

Background

Apolipoprotein A1 and B and their ratio are considered a better biomarker for cardiovascular diseases than a lipid profile, but this previous finding is not proved to cerebrovascular ischemic diseases. The aim of this study is to assess the relation between apolipoprotien A1 and B and their ratio to intra- and extracranial carotid atherosclerosis in patients with ischemic acute stroke.

Methods

90 Egyptian patients with acute ischemic stroke are included in the study, and they have been classified into 3 groups: group 1 includes 30 patients with intracranial stenosis, group 2 includes 30 patients with extracranial arterial stenosis, and group 3 includes 30 patients with non-arterial stenosis. Patients were subjected to clinical assessment, routine laboratory measures, and Color-Coded Duplex Sonography for extracranial and intracranial arteries. The measurement of serum levels of apolipoproteins A1 and B was done using enzyme-linked immuno-sorbent assay (ELISA).

Results

A statistically significant difference was found between patient groups as regards the frequency of abnormal serum LDL-cholesterol (p = 0.04), being elevated in patients with extracranial stenosis (p = 0.01). There was a significant difference between patients groups as regards the frequency of abnormal serum HDL-cholesterol (p = 0.02), being lower in patients with extracranial stenosis. High Apo B/A1 ratio was an independent risk factor for intracranial arterial stenosis (p = 0.045). An abnormal elevation of serum LDL cholesterol was an independent risk factor of extracranial arterial stenosis (p = 0.021).

Conclusion

Apo B/A1 ratio is an independent risk factor for intracranial arterial stenosis, while serum LDL cholesterol is an independent risk factor for extracranial arterial stenosis. Apo B/A1 ratio and serum LDL cholesterol are reliable serum biomarkers for cranial arterial stenosis in acute ischemic stroke patients.

An Improved Enzyme-Linked Immunosorbent Assay (ELISA) Based Protocol Using Seeds for Detection of Five Major Peanut Allergens Ara h 1, Ara h 2, Ara h 3, Ara h 6, and Ara h 8

Peanut allergy is an important health concern among many individuals. As there is no effective treatment to peanut allergy, continuous monitoring of peanut-based products, and their sources is essential. Precise detection of peanut allergens is key for identification and development of improved peanut varieties with minimum or no allergens in addition to estimating the levels in peanut-based products available in food chain. The antibody based ELISA protocol along with sample preparation was standardized for Ara h 1, Ara h 2, Ara h 3, Ara h 6, and Ara h 8 to estimate their quantities in peanut seeds. Three different dilutions were optimized to precisely quantify target allergen proteins in peanut seeds such as Ara h 1 (1/1,000, 1/2,000, and 1/4,000), Ara h 2 and Ara h 3 (1/5,000, 1/10,000, and 1/20,000), Ara h 6 (1/40,000, 1/80,000, and 1/1,60,000), and Ara h 8 (1/10, 1/20, and 1/40). These dilutions were finalized for each allergen based on the accuracy of detection by achieving <20% coefficient of variation in three technical replicates. This protocol captured wide variation of allergen proteins in selected peanut genotypes for Ara h 1 (77-46,106 μg/g), Ara h 2 (265-5,426 μg/g), Ara h 3 (382-12,676 μg/g), Ara h 6 (949-43,375 μg/g), and Ara h 8 (0.385-6 μg/g). The assay is sensitive and reliable in precise detection of five major peanut allergens in seeds. Deployment of such protocol allows screening of large scale germplasm and breeding lines while developing peanut varieties with minimum allergenicity to ensure food safety.

The association of indoxyl sulfate with fibroblast growth factor-23 in cats with chronic kidney disease

Background

Indoxyl sulfate (IS) has been reported not only to increase with the severity of impaired renal function, but also possibly to be a factor associated with bone abnormalities linked to fibroblast growth factor‐23 (FGF‐23) in humans with chronic kidney disease (CKD). It is not yet known whether this correlation between IS and FGF‐23 holds true for cats with CKD.

Hypothesis

Accumulation of IS is related to FGF‐23 secretion in cats with CKD.

Animals

Twenty clinically healthy cats and 73 cats with CKD cases were evaluated retrospectively.

Methods

The concentrations of IS and FGF‐23 in plasma were determined by high‐performance liquid chromatography and ELISA, respectively. Progression was defined as an increment of 0.5 mg/dL of serum creatinine concentration within 3 months.

Results

Plasma IS and FGF‐23 concentrations were significantly increased concurrently with decreasing renal function. Higher concentration of FGF‐23 was significantly associated with higher concentration of IS after adjusting for various confounding factors including creatinine and phosphate. Furthermore, the correlation between IS and phosphate was higher than that between FGF‐23 and phosphate. When the renal progression group was compared with the non‐progression group, both IS and FGF‐23 were found to be significantly increased (P < .05). In addition, the area under receiver operator curve of the combination of IS and FGF‐23 predicted renal progression at a level >0.9.

Conclusions and Clinical Importance

Both FGF‐23 and IS are associated with phosphate metabolism and CKD progression.

The Case for Human Serum as a Highly Preferable Sample Matrix for Detection of Anthrax Toxins

This paper describes preliminary results on the surprising impact of human serum as a sample matrix on the detectability of protective antigen (PA) and lethal factor (LF), two antigenic protein markers of Bacillus anthracis, in a heterogeneous immunometric assay. Two sample matrices were examined: human serum and physiological buffer. Human serum is used as a specimen in the diagnostic testing of potentially infected individuals. Physiological buffers are often applied to the recovery of biomarkers dispersed in suspicious white powders and other suspect specimens and as a serum diluent to combat contributions to the measured test response from nonspecific adsorption. The results of these experiments using a sandwich immunoassay read out by surface-enhanced Raman scattering yielded estimates for the limit of detection (LOD) for both markers when using spiked human serum that were remarkably lower than those of spiked physiological buffer (∼70,000× for PA and ∼25,000× for LF). The difference in LODs is attributed to a degradation in the effectiveness of the capture and/or labeling steps in the immunoassay due to the known propensity for both proteins to denature in buffer. These findings indicate that the use of physiological buffer for serum dilution or recovery from a powdered matrix is counter to the low-level detection of these two antigenic proteins. The potential implications of these results with respect to the ability to detect markers of other pathogenic agents are briefly discussed.