Recent advancements in the sensors for food analysis to detect gluten: A mini-review [2019-2023].

People with celiac disease or gluten sensitivity may experience an immune reaction to the protein called gluten, which is present in wheat, barley, and rye. A strict gluten-free diet is the sole cure for these ailments. There are chances of food fraud about the claim of being gluten-free food items. As a result, there is a rising need for trustworthy and precise ways to identify gluten. There are many methods to detect gluten in food samples viz., enzyme-linked immunosorbent assay 1 Surface plasmon resonance (SPR), Electrochemical sensors, Fluorescence-based sensors, etc. The use of sensors is one of the most promising methods for gluten detection. For detecting gluten, a variety of sensors, including optical, electrochemical, and biosensors, have been developed with different limits of detection and sensitivity. The present review reports the recent advancements (2019-2023) in the development of sensors for gluten detection in food. We may conclude that sensitivity and limit of detection are not related to the type of sensor used (aptamer or antibody-based), however, there are advancements, with the year, on the simplicity of the material used like paper-based sensors and paradigm shift to reagent free sensors by the spectral analysis. Also, recent work shows the potential of IoT-based studies for gluten detection.

O efeito do tratamento com rapamicina em órgãos linfoides de camundongos propensos à senescência acelerada / The effect of rapamycin treatment on lymphoid organs of senescence accelerated mice prone

Envelhecer compreende um fenômeno complexo, natural e irreversível, que submete o organismo a inúmeras alterações nos processos biológicos, fisiológicos, ambientais, psicológicos, comportamentais e sociais. Esse processo é caracterizado por um declínio gradual dos mecanismos homeostáticos do organismo, intimamente relacionados com o estado senescente. A senescência, quando diz respeito ao sistema imunológico, é denominada de imunossenescência, que pode ser definida como uma parada estável do ciclo celular associada a mudanças, com uma resposta que limita a proliferação de células envelhecidas ou danificadas. A autofagia está diretamente relacionada com a manutenção do fenótipo senescente, em que a atividade autofágica exerce um papel essencial e ativo na influência da biossíntese de proteínas e organelas. Essa via é regulada naturalmente pela proteína mTOR e quimicamente pelo fármaco rapamicina. Assim, pretendemos investigar: (1) as alterações no perfil corporal e hematimêtrico dos animais ao longo do tratamento com rapamicina; (2) avaliar o perfil de citocinas; (3) observar as modificações histológicas em órgãos linfoides primários e secundário; (4) analisar as populações de células linfoides e mieloides; e (5) avaliar a capacidade proliferativa de linfócitos in vitro. Camundongos SAMP-8 e SAMR-1 foram tratados com rapamicina durante dois meses. A mensuração da massa corporal e análises hematológicas foram realizadas antes e durante o tratamento. Amostras de soro, medula óssea, timo e baço foram analisados em ensaios de ELISA, histologia, população e subpopulações de células. Alterações na massa corporal, parâmetros hematológicos e celularidade de células foram nítidas entre os dois modelos utilizados. Diferenças também foram percebidas na detecção de citocinas IL-1ß. IL-6 e TNF-α, com resultados significantes nas amostras de baço, timo e medula óssea. As citocinas IL-7 e IL-15 apresentaram diferenças de secreção entre os grupos, sendo a primeira maior detectada em camundongos com senescência acelerada tratados com rapamicina. Em nossa análise histológica observamos que os camundongos SAM-P8 apresentaram involução tímica. E nas subpopulações de linfócitos T do baço, células TCD4+ e TCD8+ estavam, respectivamente, em maior e menor quantidade nos camundongos SAM-P8 tratados com rapamicina. Dessa forma, o camundongo da linhagem SAM-P8 é um excelente modelo para se estudar as alterações da senescência, em que o mesmo apresenta características fisiológicas distintas dos camundongos utilizados como controle (SAM-R1). Além disso, verificamos que a dose de rapamicina empregada não desencadeou alterações que pudessem comprometer a resposta imunológica desses camundongos, bem como na possibilidade de atuar na resposta contra os efeitos complexos do envelhecimento

Aging comprises a complex, natural, and irreversible phenomenon, which subjects the organism to countless alterations in biological, physiological, environmental, psychological, behavioral, and social processes. This process is characterized by a gradual decline in the organism's homeostatic mechanisms, closely related to senescence effects. Senescence, when it concerns the immune system, is called immunosenescence, which can be defined as a stable cell cycle arrest associated with changes and is a response that limits the proliferation of aged or damaged cells. Autophagy is a genetically regulated, conserved cellular process and a metabolic pathway essential for maintaining cellular homeostasis, which plays a constitutive and active role in controlling the biosynthesis of proteins and organelles. This pathway is regulated naturally by mTOR or chemically by the drug rapamycin, having a direct relationship with cellular homeostasis and maintenance of the senescent phenotype. Thus, we intend to investigate: (1) the changes in the body and hematimetic profile of the animals throughout the rapamycin treatment; (2) evaluate the cytokine profile; (3) observe histological changes in primary and secondary lymphoid organs; (4) analyze lymphoid and myeloid cell populations; and (5) evaluate the proliferative capacity of lymphocytes in vitro. SAMP-8 and SAMR-1 mice were treated with rapamycin for two months. Body mass measurement and hematological analyses were performed before and during treatment. Serum, bone marrow, thymus and spleen samples were analyzed in ELISA assays, histology, cell population and subpopulations. Changes in body mass, hematological parameters, and cellularity were clear between the two models used. Differences were also noticed in the detection of cytokines IL-1ß. IL-6 and TNF-α, with significant results in the spleen, thymus and bone marrow samples. The cytokines IL-7 and IL-15 showed differences in secretion between groups, the former being higher detected in mice with accelerated senescence treated with rapamycin. In our histological analysis we observed that SAM-P8 mice showed thymic involution. And in the spleen T-lymphocyte subpopulations, TCD4+ and TCD8+ cells were, respectively, in higher and lower quantities in SAM-P8 mice treated with rapamycin. Thus, the SAM-P8 mouse is an excellent model to study the changes of senescence, since it presents physiological characteristics different from the control mice (SAM-R1). Furthermore, we verified that the dose of rapamycin used did not trigger changes that could compromise the immune response of these mice, as well as the possibility of acting in the modulatory response against the complex effects of aging

Evaluation of the analytical performance of anti-SARS-CoV-2 antibody test kits distributed or developed in Japan.

Background: With the spread of COVID-19, anti-SARS-CoV-2 antibody tests have been utilized. Herein we evaluated the analytical performance of anti-SARS-CoV-2 antibody test kits using a new reference standard prepared from COVID-19 patient sera. Methods: Fifty-seven kits in total (16 immunochromatography types, 11 ELISA types and 30 types for automated analyzers) were examined. By measuring serially diluted reference standards, the maximum dilution factor showing a positive result and its precision were investigated. Results: The measured cut-off titers varied largely depending on the antibody kit; however, the variability was small, with the titers obtained by each kit being within twofold in most cases. Conclusion: The current results suggest that a suitable kit should be selected depending on the intended purpose.

Paper-based microfluidic chip for rapid detection of SARS-CoV-2 N protein.

This research has developed a method for rapid detection of SARS-CoV-2 N protein on a paper-based microfluidic chip. The chitosan-glutaraldehyde cross-linking method is used to fix the coated antibody, and the sandwich enzyme-linked immunosorbent method is used to achieve the specific detection of the target antigen. The system studied the influence of coating antibody concentration and enzyme-labeled antibody concentration on target antigen detection. According to the average gray value measured under different N protein concentrations, the standard curve of the method was established and the sensitivity was tested, and its linear regression was obtained. The equation is y = 9.8286x+137.6, R2 = 0.9772 > 0.90, which shows a high degree of fit. When the concentration of coating antibody and enzyme-labeled antibody were 1 µg/mL and 2 µg/mL, P > 0.05, the difference was not statistically significant, so the lower concentration of 1 µg/mL was chosen as the coating antibody concentration. The results show that the minimum concentration of N protein that can be detected by this method is 8 µg/mL, and the minimum concentration of coating antibody and enzyme-labeled antibody is 1 µg/mL, which has the characteristics of high sensitivity and good repeatability.

Protective effects of Baicalin injection on severe acute pancreatitis through regulating follistatin-like-1 signaling pathway by down-regulating miR-429 expression in mice

Abstract In China, Scutellaria is used for treating inflammatory-related diseases. Baicalin is the main active component of Scutellaria and has protective effects on acute pancreatitis. However, the mechanism of Baicalin is still unclear. In this study, the protective effects of baicalin on acute pancreatitis induced by taurocholate and its mechanism are investigated. In this study, mice were randomly divided into three groups: sham operation, model, and treatment groups. Acute pancreatitis in mice was induced by intraperitoneal injection of taurocholate (35 mg/kg). The treatment group was given baicalin (100 mg/kg) 2 h before acute pancreatitis induction. The mRNA expression levels of miR-429, nuclear factor kappa B65(NF-kB65), toll-like receptor 4(TLR4), TNF receptor associated factor6 (TRAF6), NF-kappa-B inhibitor(IkB), Follistatin-like 1 (FSTL1), and interleukin-1 receptor-associated kinase (IRAK) in the liver tissues 24 h after intraperitoneal injection were detected by RT-PCR. Then, the expression levels of NF-kB65, p-NF-κB65, TLR4, TRAF6, IkB, FSTL1, IRAK, p- IRAK, and p- IkB-а proteins were detected by Western blot. IL-6, TNF-α and IL-1 ß in plasma were measured by ELISA, and histopathological changes in the pancreases of the mice were observed. The results showed that after baicalin treatment, miR-429 expression in the pancreatic tissues and the expression levels of NF-kB65, TLR4, TRAF6, p-IkB-а, FSTL1, and p-IRAK decreased. Similarly, pancreatic myeloperoxidase (MPO) activity and the plasma levels of IL-6, TNF-а, IL-12, IL-1ß1, endotoxin, serum amylase, and lipase were reduced. Thus, the pancreatic injury induced by taurocholate was alleviated. The present study indicates that pretreatment with Baicalin can alleviate acute pancreatic injury induced by taurocholate in mice. The mechanism may be associated with the decreased miR-429 expression, reduced FSTL1 signaling pathway activity, TLR4 and TLR4/MyD88 signaling pathway inhibition, and reduced pancreatic inflammation. FSTL1 is the regulatory target for miR-429

Evaluation of miR-15a, miR-16-1, ZAP-70, Ang-2, and Bcl-2 as potential prognostic biomarkers in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a blood cancer characterized by the accumulation of clonal B-lymphocytes. This study evaluated the mRNA gene expression of miR-15a, miR-16- 1, ZAP-70, and Ang-2 by qPCR, as well as the plasma levels of Bcl-2 by Elisa immunoassay, in CLL patients and healthy controls. Significant differences were observed when comparing patients and controls regarding miR-15a (p < 0.001), miR-16-1 (p < 0.001) mRNA, Ang-2 gene expression, and Bcl-2 plasma levels (p < 0.001). When stratified by risk, differences were maintained with a significantly reduced expression in high-risk patients. A positive correlation was observed between miR-15a and platelets (R2 = 0.340; p = 0.009) as well as between Bcl-2 and leukocytes (R2 = 0.310; p = 0.019). Conversely, negative correlations were observed between ZAP-70 and platelets (R2 = - 0.334; p = 0.011), between miR-15a and lymphocytes (R2 = - 0.376; p = 0.004), as well as between miR-16-and lymphocytes (R2 = - 0.515; p = 0.00004). The data suggest that a reduction in miR-15a and miR-16-1 expressions, in addition to an overexpression of Bcl-2, are associated with the reduction in apoptosis and, consequently, to a longer survival of lymphocytes, thus contributing to lymphocyte accumulation and aggravation of the disease. By contrast, Ang-2 expression was significantly higher in A than in B + C Binet groups. This context leads to the speculation that this biomarker should be investigated in more robust studies within populations with a still relevantly indolent form of the disease in an attempt to identify those patients with a greater potential for an aggravation of the disease

Development of a sensitive sandwich-ELISA assay for reliable detection of fish residues in foods.

A new sandwich-type Enzyme-Linked Immunosorbent Assay (ELISA) method was developed based on goat IgG as capturing antibody and rabbit IgG as detecting antibody targeting soluble antigenic fish proteins in foods as detection targets. The assay has provided a relatively lower limit of quantitation (LoQ) for fish proteins with LoQ 0.5 ng/ml and appears highly sensitive. The analysis of 24 different substances, both raw and boiled, revealed no cross-reactivity above the cut-off point of the limit of quantitation. Recoveries of the SB spiked food matrixes were in the range of 83-131%. Assay precision testing proved that repeatability (<5%) and reproducibility (<11%) had an acceptable level of variation. The sandwich ELISA was capable of detecting all tested commercially important fish. As a potential analytical tool, the newly developed immunoenzymatic method is suitable for detecting undeclared fish residues in real food samples available in the market, thereby will help to reduce the incidents of fish allergies.

Immobilization of Proteinase K for urine pretreatment to improve diagnostic accuracy of active tuberculosis.

The World Health Organization (WHO) calls for the development of a rapid, biomarker-based, non-sputum test capable of detecting all forms of tuberculosis (TB) at the point-of-care to enable immediate treatment initiation. Lipoarabinomannan (LAM) is the only WHO-endorsed TB biomarker that can be detected in urine, an easily collected sample matrix. For obtaining optimal sensitivity, we and others have shown that some form of sample pretreatment is necessary to remove background from patient urine samples. A number of systems are paper-based often destined for resource limited settings. Our current work presents incorporation of one such sample pretreatment, proteinase K (ProK) immobilized on paper (IPK) and test its performance in comparison to standard proteinase K (SPK) treatment that involves addition and deactivation at high temperature prior to performing a capture ELISA. Herein, a simple and economical method was developed for using ProK immobilized strips to pretreat urine samples. Simplification and cost reduction of the proposed pretreatment strip were achieved by using Whatman no.1 paper and by minimizing the concentration of ProK (an expensive but necessary reagent) used to pretreat the clinical samples prior to ELISA. To test the applicability of IPK, capture ELISA was carried out on either LAM-spiked urine or the clinical samples after pretreatment with ProK at 400 µg/mL for 30 minutes at room temperature. The optimal conditions and stability of the IPK were tested and validation was performed on a set of 25 previously analyzed archived clinical urine samples with known TB and HIV status. The results of IPK and SPK treated samples were in agreement showing that the urine LAM test currently under development has the potential to reach adult and pediatric patients regardless of HIV status or site of infection, and to facilitate global TB control to improve assay performance and ultimately treatment outcomes.

Paper-based ELISA diagnosis technology for human brucellosis based on a multiepitope fusion protein.

BACKGROUND: Brucellosis, as a serious zoonotic infectious disease, has been recognized as a re-emerging disease in the developing countries worldwide. In china, the incidence of brucellosis is increasing each year, seriously threatening the health of humans as well as animal populations. Despite a quite number of diagnostic methods currently being used for brucellosis, innovative technologies are still needed for its rapid and accurate diagnosis, especially in area where traditional diagnostic is unavailable. METHODOLOGY/PRINCIPAL FINDINGS: In this study, a total of 22 B cell linear epitopes were predicted from five Brucella outer membrane proteins (OMPs) using an immunoinformatic approach. These epitopes were then chemically synthesized, and with the method of indirect ELISA (iELISA), each of them displayed a certain degree of capability in identifying human brucellosis positive sera. Subsequently, a fusion protein consisting of the 22 predicted epitopes was prokaryotically expressed and used as diagnostic antigen in a newly established brucellosis testing method, nano-ZnO modified paper-based ELISA (nano-p-ELISA). According to the verifying test using a collection of sera collected from brucellosis and non-brucellosis patients, the sensitivity and specificity of multiepitope based nano-p-ELISA were 92.38% and 98.35% respectively. The positive predictive value was 98.26% and the negative predictive value was 91.67%. The multiepitope based fusion protein also displayed significantly higher specificity than Brucella lipopolysaccharide (LPS) antigen. CONCLUSIONS: B cell epitopes are important candidates for serologically testing brucellosis. Multiepitope fusion protein based nano-p-ELISA displayed significantly sensitivity and specificity compared to Brucella LPS antigen. The strategy applied in this study will be helpful to develop rapid and accurate diagnostic method for brucellosis in human as well as animal populations.

Clinical Utility of Biosensing Platforms for Confirmation of SARS-CoV-2 Infection.

Despite collaborative efforts from all countries, coronavirus disease 2019 (COVID-19) pandemic has been continuing to spread globally, forcing the world into social distancing period, making a special challenge for public healthcare system. Before vaccine widely available, the best approach to manage severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is to achieve highest diagnostic accuracy by improving biosensor efficacy. For SARS-CoV-2 diagnostics, intensive attempts have been made by many scientists to ameliorate the drawback of current biosensors of SARS-CoV-2 in clinical diagnosis to offer benefits related to platform proposal, systematic analytical methods, system combination, and miniaturization. This review assesses ongoing research efforts aimed at developing integrated diagnostic tools to detect RNA viruses and their biomarkers for clinical diagnostics of SARS-CoV-2 infection and further highlights promising technology for SARS-CoV-2 specific diagnosis. The comparisons of SARS-CoV-2 biomarkers as well as their applicable biosensors in the field of clinical diagnosis were summarized to give scientists an advantage to develop superior diagnostic platforms. Furthermore, this review describes the prospects for this rapidly growing field of diagnostic research, raising further interest in analytical technology and strategic plan for future pandemics.

An efficient peptide-based ELISA for differentiating fowl adenovirus 4-infected chickens from vaccinated chickens.

Fowl adenovirus serotype 4 (FAdV4), the causative agent of hepatitis-hydropericardium syndrome (HPS), has caused major economic losses to the poultry industry worldwide. Although inactivated vaccines have been deployed widely against FAdV4, a DIVA (differentiating infected from vaccinated animals) test specific for FAdV4 has not been available. We synthesized an immunogenic peptide, corresponding to regions 66-88 aa of the 22K nonstructural protein of FAdV4, and used the peptide as coating antigen to develop an indirect ELISA for a DIVA test specific to FAdV4. Specificity analysis showed that the ELISA only reacted with sera against FAdV4, and not with sera against other pathogens tested. Moreover, the ELISA could effectively differentiate FAdV4-infected chickens from vaccinated chickens. In a test of sera from experimentally infected chickens, the ELISA had 95% and 85% concordance with an indirect immunofluorescence assay (indirect IFA) and a commercial ELISA, respectively, and the concordance was 80.5% between the ELISA and the indirect IFA in detecting clinical infection samples. Our peptide-based ELISA provides an efficient DIVA test for FAdV4 in clinical samples.

Multicolorimetric ELISA biosensors on a paper/polymer hybrid analytical device for visual point-of-care detection of infection diseases.

Enzyme-linked immunosorbent assay (ELISA) is widely used for the detection of disease biomarkers. However, it utilizes time-consuming procedures and expensive instruments, making it infeasible for point-of-care (POC) analysis especially in resource-limited settings. In this work, a multicolorimetric ELISA biosensor integrated on a paper/polymer hybrid microfluidic device was developed for rapid visual detection of disease biomarkers at point of care, without using costly equipment. This multicolormetric ELISA platform was built on multiple distinct color variants resulted from the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) and the etching of gold nanorods (AuNRs). The vivid color changes could be easily distinguished by the naked eye, and their red mean values allowed quantitative biomarker detection, without using any sophisticated instruments. When this multicolorimetric ELISA was integrated on a paper/polymer hybrid analytical device, it not only provided integrated processing and high portability but also enabled fast assays in about 50 min due to the unique advantages of paper/polymer hybrid devices. The limit of detection of 9.1 ng/µL of the hepatitis C virus core antigen, a biomarker for hepatitis C, was achieved using this multicolorimetric ELISA platform. This multicolor ELISA analytical device provides a new versatile, user-friendly, affordable, and portable immunosensing platform with high potential for on-site detections of various viruses, proteins, and biomarkers for low-resource settings such as at home, public venues, rural areas, and developing nations.

Development and performance evaluation of a rapid in-house ELISA for retrospective serosurveillance of SARS-CoV-2.

BACKGROUND: In the ongoing pandemic situation of COVID-19, serological tests can complement the molecular diagnostic methods, and can be one of the important tools of sero-surveillance and vaccine evaluation. AIM: To develop and evaluate a rapid SARS-CoV-2 specific ELISA for detection of anti-SARS-CoV2 IgG from patients' biological samples. METHODS: In order to develop this ELISA, three panels of samples (n = 184) have been used: panel 1 (n = 19) and panel 2 (n = 60) were collected from RT-PCR positive patients within 14 and after 14 days of onset of clinical symptoms, respectively; whereas panel 3 consisted of negative samples (n = 105) collected either from healthy donors or pre-pandemic dengue patients. As a capturing agent full-length SARS-CoV2 specific recombinant nucleocapsid was immobilized. Commercial SARS-CoV2 IgG kit based on chemiluminescent assay was used for the selection of samples and optimization of the assay. The threshold cut-off point, inter-assay and intra-assay variations were determined. RESULTS: The incubation/reaction time was set at a total of 30 minutes with the sensitivity of 84% (95% confidence interval, CI, 60.4%, 96.6%) and 98% (95% CI, 91.1%, 100.0%), for panel 1 and 2, respectively; with overall 94.9% sensitivity (95% CI 87.5%, 98.6%). Moreover, the clinical specificity was 97.1% (95% CI, 91.9%, 99.4%) with no cross reaction with dengue samples. The overall positive and negative predictive values are 96.2% (95% CI 89.2%, 99.2%) and 96.2% (95% CI, 90.6% 99.0%), respectively. In-house ELISA demonstrated 100% positive and negative percent agreement with Elecsys Anti-SARS-CoV-2, with Cohen's kappa value of 1.00 (very strong agreement), while comparing 13 positive and 17 negative confirmed cases. CONCLUSION: The assay is rapid and can be applied as one of the early and retrospective sero-monitoring tools in all over the affected areas.

Reciprocating-flowing on-a-chip enables ultra-fast immunobinding for multiplexed rapid ELISA detection of SARS-CoV-2 antibody.

The worldwide epidemic of novel coronavirus disease (COVID-19) has led to a strong demand for highly efficient immunobinding to achieve rapid and accurate on-site detection of SARS-CoV-2 antibodies. However, hour-scale time-consumption is usually required to ensure the adequacy of immunobinding on expensive large instruments in hospitals, and the common false negative or positive results often occur in rapid on-site immunoassay (e.g. immunochromatography). We solved this dilemma by presenting a reciprocating-flowing immunobinding (RF-immunobinding) strategy. RF-immunobinding enabled the antibodies in fluid contacting with the corresponding immobilized antigens on substrate repeatedly during continuous reciprocating-flowing, to achieve adequate immunobinding within 60 s. This strategy was further developed into an immunoassay method for the serological detection of 13 suspected COVID-19 patients. We obtained a 100% true negative and true positive rate and a limit of quantification (LOQ) of 4.14 pg/mL. Our strategy also can be a potential support for other areas related to immunorecognition, such as proteomics, immunopharmacology and immunohistochemistry.

Development of Nano-ELISA Method for Serological Diagnosis of Toxoplasmosis in Mice.

Toxoplasmosis is a widespread parasitic disease caused by a protozoan parasite Toxoplasma gondii. Currently, nanotechnology has been used for the diagnosis of many infectious diseases. It could be due to the fact that nanoparticles play an important role in accurate and fast diagnosis. The purpose of this study was to design a Nano-enzyme linked immunosorbent assay (Nano-ELISA) kit using excreted/secreted (E/S) antigens to have higher sensitivity and specificity than those reported for the designed enzyme-linked immunosorbent assay (ELISA) kit for the diagnosis of Toxoplasmosis in mice. Firstly, the serum samples were collected from 15 infected mice with T. gondii and 15 healthy ones. Then, E/S antigens were separated from parasite tachyzoites and used for designing an ELISA kit. In addition, the mice sera were evaluated using the designed ELISA kit. Finally, the serum samples were assessed by Nano-ELISA kits designed with E/S antigen and conjugate of gold nanoparticles. The obtained results of the present study showed that the sensitivity and specificity of the designed ELISA kit were reported as 80% and 86.66%, respectively, that both improved to 93.33% in these sera with the designed Nano-ELISA kit. This finding revealed the significant improvement of sensitivity and specificity using gold nanoparticles in designing the ELISA kit. Furthermore, according to the literature, the use of E/S antigens in designing recognizable ELISA kits has been always highlighted considering the presence of numerous antigens in T. gondii. The results of this study revealed that the use of E/S antigens in the preparation of an ELISA kit was very effective. This is very important, especially in the lower titers of antibody requiring a more accurate diagnosis. On the other hand, the Nano-ELISA method designed with E/S antigens can be more sensitive and specific than ELISA for the diagnosis of Toxoplasmosis and can be the basis for further studies in this regard.

Rapid SARS-CoV-2 Detection Using Electrochemical Immunosensor.

The outbreak of the coronavirus disease (COVID-19) pandemic caused by the novel coronavirus (SARS-CoV-2) has been declared an international public health crisis. It is essential to develop diagnostic tests that can quickly identify infected individuals to limit the spread of the virus and assign treatment options. Herein, we report a proof-of-concept label-free electrochemical immunoassay for the rapid detection of SARS-CoV-2 virus via the spike surface protein. The assay consists of a graphene working electrode functionalized with anti-spike antibodies. The concept of the immunosensor is to detect the signal perturbation obtained from ferri/ferrocyanide measurements after binding of the antigen during 45 min of incubation with a sample. The absolute change in the [Fe(CN)6]3-/4- current upon increasing antigen concentrations on the immunosensor surface was used to determine the detection range of the spike protein. The sensor was able to detect a specific signal above 260 nM (20 µg/mL) of subunit 1 of recombinant spike protein. Additionally, it was able to detect SARS-CoV-2 at a concentration of 5.5 × 105 PFU/mL, which is within the physiologically relevant concentration range. The novel immunosensor has a significantly faster analysis time than the standard qPCR and is operated by a portable device which can enable on-site diagnosis of infection.

Nuclear magnetic resonance immunoassay of tetanus antibodies based on the displacement of magnetic nanoparticles.

A nuclear magnetic resonance (NMR) immunoassay based on the application of carbon-coated iron nanoparticles conjugated with recognition molecules was designed. The principle of the assay is that ELISA plates are coated with a capture element, and then an analyte is added and detected by conjugating the magnetic nanoparticles with recognition molecules. Afterwards, the elution solution (0.1-M sodium hydroxide) is added to displace the magnetic nanoparticles from the well surfaces into the solution. The detached magnetic nanoparticles reduce transverse relaxation time (T2) values of protons from the surrounding solution. A portable NMR relaxometer is used to measure the T2. Magnetic nanoparticles conjugated with streptavidin, monoclonal antibodies, and protein G were applied for the detection of biotinylated albumin, prostate-specific antigen, and IgG specific to tetanus toxoid (TT). The limit of detection of anti-TT IgG was 0.08-0.12 mIU/mL. The reproducibility of the assay was within the acceptable range (CV < 7.4%). The key novelty of the immunoassay is that the displacement of the nanoparticles from the solid support by the elution solution allows the advantages of the solid phase assay to be combined with the sensitive detection of the T2 changes in a volume of liquid.

Development of rapid gold nanoparticles based lateral flow assays for simultaneous detection of Shigella and Salmonella genera.

Salmonella and Shigella genera are common pathogens that contaminate foods and beverages. Lateral flow assays (LFA) are commonly used to detect these pathogens. However, most of the developed LFAs are for single detection. Simultaneous detection of pathogens is required to reduce cost and time. In this work, 40 nm gold nanoparticles (AuNPs) were synthesized using the seeding growth method as labeling agent. The AuNPs were characterized and conjugated with mouse anti-Gram negative endotoxin antibody. The nitrocellulose membrane HF135 was immobilized with anti-mouse IgG antibody as a control line and two separate test lines with either anti-Shigella or anti-Salmonella antibody, respectively. Color intensity of test lines was observed for positive samples. A milk sample was used as proof of concept to mimic actual contamination. The limit of detection of the LFA was 3.0 × 106 CFU/mL for multiplex detection of Shigella flexneri and Salmonella Typhi and for both single detections. The result was comparable with the enzyme-linked immunosorbent assay (ELISA) analysis. The produced LFA could differentiate between Shigella flexneri, Shigella boydii, Salmonella Enteritidis, and Salmonella Typhi. The developed LFA was able to identify Shigella flexneri and Salmonella Typhi with good sensitivity in milk samples, thus, beneficial to ensure the safety of food before entering the market.

Serum pooling for rapid expansion of anti-SARS-CoV-2 antibody testing capacity.

OBJECTIVES: Examine possible pooling strategies designed to expand SARS-CoV-2 serological testing capacity. METHODS: Negative pools were assessed to determine optimal optical density (OD) cutoffs, followed by spiking weak or strong positive samples to assess initial assay performance. Samples were then randomly subjected to pool and individual testing approaches. RESULTS: Single positive specimens consistently converted pools of 5, 10, or 20 into positive outcomes. However, weaker IgG-positive samples failed to similarly convert pools of 50 to a positive result. In contrast, a stronger individual positive sample converted all pools tested into positive outcomes. Finally, examination of 150 samples configured into pools of 5, 10, 20 or 50 accurately predicted the presence of positive or negative specimens within each pool. CONCLUSIONS: These results suggest that pooling strategies may allow expansion of serological testing capacity. While limitations exist, such strategies may aid in large-scale epidemiological screening or identification of optimal convalescent plasma donors.

Avaliação da resposta de anticorpos IgG contra diferentes variantes alélicas do Antígeno 1 de Membrana Apical (AMA-1) de Plasmodium vivax em indivíduos de áreas endêmicas de malária / Evaluation of IgG antibody response against different variants of Plasmodium vivax apical membrane antigen 1 (AMA-1) in individuals from malaria endemic areas

O Plasmodium vivax é a espécie com maior distribuição geográfica no mundo e a que predomina nas Américas, incluindo o Brasil. Comparado ao Plasmodium falciparum, poucas vacinas contra o P. vivax encontram-se em fase de testes clínicos. Um dos antígenos de formas sanguíneas de P. vivax candidato a vacina é o Antígeno 1 de Membrana Apical (PvAMA-1). Entretanto, a diversidade antigênica do mesmo na natureza representa um grande desafio para seu uso no desenvolvimento de uma vacina de ampla cobertura. No presente estudo, avaliamos se os polimorfismos de sequências já descritos são capazes de influenciar na eficácia de uma vacina baseada em PvAMA-1. Para isso, geramos 9 proteínas recombinantes a partir da levedura Pichia pastoris, as quais são representativas de diferentes variantes alélicas do antígeno PvAMA-1, a saber: Belem, Chesson I, Sal-1, Indonesia XIX, SK0814, TC103, PNG_05_ESP, PNG_62_MU e PNG_68_MAS. Após expressão e purificação das proteínas selecionadas, avaliamos comparativamente por ELISA a resposta de anticorpos IgG naturalmente adquiridos em indivíduos expostos a malária, procedentes da Região Amazônica. Todas as proteínas foram obtidas com rendimento e pureza apropriados para os estudos propostos. A prevalência total de indivíduos expostos a malária com anticorpos contra PvAMA-1 Belem foi de 53,68%, em 611 amostras de soro testadas. Entre 100 das amostras sorologicamente positivas para PvAMA-1 Belem, os maiores valores de DO492 foram obtidos para as variantes Chesson I, SK0814 e Sal-1, sugerindo que epítopos comuns ou de reatividade cruzada estão sendo reconhecidos nessas variantes. Por outro lado, níveis mais baixos de DO492 foram obtidos para as variantes Indonesia XIX, TC103, PNG_05_ESP, PNG_62_MU e PNG_68_MAS, o que pode significar que essas variantes são menos prevalentes ou não circulam no Brasil. Soros policlonais de camundongos C57BL/6 previamente imunizados com PvAMA-1 Belem foram testados quanto ao reconhecimento das diferentes variantes por ELISA. Nossos resultados demonstraram que as variantes Chesson I, Indonesia XIX, SK0814, Sal-1 e a proteína homóloga foram predominantemente reconhecidas. Por fim, ensaios de competição baseados em ELISA revelaram que as proteínas Chesson I, Indonesia XIX, SK0814 e Sal-1, na fase solúvel, foram capazes de inibir a ligação de anticorpos à variante Belem aderida a placa, sugerindo a presença de epítopos comuns ou de reatividade cruzada entre as mesmas. Nossos dados sugerem que uma vacina baseada na variante PvAMA-1 Belem gera anticorpos variante-transcendentes. Entretanto, para gerar uma vacina universal baseada em PvAMA-1, uma formulação multi-alélica, incluindo variantes da Tailândia e Papua Nova Guiné, deverão ser testadas

Plasmodium vivax has the largest geographical distribution Plasmodium species in the world, and is predominant in the Americas, including Brazil. Fewer P. vivax vaccines than P. falciparum vaccines have successfully reached clinical trials. One of the candidate antigens for a blood-stage P. vivax vaccine is the apical membrane antigen 1 (PvAMA-1). However, the high natural variability found in this antigen presents a major challenge for its development into a wide-range vaccine. In the present study, we evaluated whether sequence polymorphisms would influence a vaccine based on PvAMA-1. To achieve this, we generated 9 recombinant proteins from the yeast Pichia pastoris, representative of different allelic variants of the PvAMA-1 antigen: Belem, Chesson I, Sal-1, Indonesia XIX, SK0814, TC103, PNG_05_ESP, PNG_62_MU, and PNG_68_MAS. After expression and purification of these proteins, we compared, by ELISA and IgG blocking, the natural acquired response from malaria-exposed individuals in the Amazon Region. All proteins selected had the appropriate yield and purity for the proposed studies. The total prevalence of malaria-exposed individuals with reactivity to PvAMA-1 Belem was 53,68%, from 611 serum samples tested. One hundred of these serologically positive samples were further tested against recombinant proteins representing the other allelic variants. The highest OD values resulted from Sal-1, Chesson I and SK0814 variants, suggesting that common epitopes or cross-reactivity exist across the variants. On the other hand, the lowest OD values resulted from the variants Indonesia XIX, TC103, PNG_05_ESP, PNG_62_MU, and PNG_68_MAS, which may mean these variants are less prevalent or do not circulate in Brazil. Polyclonal sera from C57BL/6 mice immunized with PvAMA-1 Belem were tested for recognition of different variants by ELISA. Our results showed that the variants Chesson I, Sal-1, Indonesia XIX, SK0814 and the homologous protein were predominantly recognized. Lastly, ELISA-based competition assays revealed that Chesson I, Sal-1, Indonesia XIX and SK0814 proteins were able to inhibit antibody binding to the Belem variant, suggesting the presence of common epitopes or cross-reactivity between these variants. Our data suggest that a vaccine based on the PvAMA-1 Belem variant displays strain-transcendent antibodies. However, to generate a universal vaccine based on PvAMA-1, a multiallelic formulation including variants from Thailand and Papua New Guinea must be tested