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Immunological Tests for Diagnosis of Disease and Identification of Molecules
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
The enzyme-linked immunosorbent assay (ELISA) technique is a highly versatile, sensitive, and quantitative procedure that requires little equipment and for which reagents are readily available. It was first introduced in 1971 by Engvall and Perlmann. The term enzyme immunoassay (EIA) is an alternative name for this type of test and is used for the many variants of the assay. Enzymes such as alkaline phosphatase or peroxidase can be linked to antibody without destroying either the antibody′s specificity or the enzyme′s activity. The enzyme acts as a label which makes detection of the antibody possible. Both monoclonal and polyclonal antibodies can be used in this type of test. Enzyme labels are cheaper, simpler to measure, and far more stable than radioactive labels. For these reasons, ELISA or EIA assays have in many cases replaced RIA and have done so while maintaining sensitivity and specificity. Many of the assays for hepatitis A and B in use today are based on ELISA. In addition to the use of enzymes in immunoassays, nonenzy-matic markers can also be used if they can be conjugated to the antibody (e.g., colloidal gold with silver enhancement, and biotination with avidine).
Diagnosis of COVID-19 Using Clinical Examination, Immunoassays, and Molecular Diagnostic Techniques
Published in Srijan Goswami, Chiranjeeb Dey, COVID-19 and SARS-CoV-2, 2022
Srijan Goswami, Ushmita Gupta Bakshi
This serological method takes a much longer time as compared with the rapid test and is useful in gathering epidemiological data, as well as helping to develop treatments. ELISA stands for enzyme-linked immunosorbent assay. In this process, a small amount of serum sample is collected and put into the microtiter well, then IgG from recovered individuals (primary antibody) is added to it. The idea is that the primary antibody will bind to the spike protein antigen of SARS-CoV-2. After that, a secondary antibody tagged with the specific enzyme is added to the reaction mixture. The enzyme-linked secondary antibody binds to the primary antibody. A chromogenic chemical is added to the reaction mixture that acts as the substrate for the enzyme-linked secondary antibody. This enzyme substrate reaction generates a color that is sensed and analyzed by the ELISA reader. The generation of color means a positive test and the intensity of the color is directly proportional to the concentration of antigens. So these are the serology tests that are combined, in addition to RT-PCR (CDC, 2020; Center for Devices and Radiological Health, 2021; Uwamino et al., 2021; Kang et al., 2021).
Nipah encephalitis, a fatal encephalitis with bats as reservoir
Published in Avindra Nath, Joseph R. Berger, Clinical Neurovirology, 2020
IgM and IgG antibody detection in serum and CSF were critical to the diagnosis of Nipah virus infection. The antibody test utilized an IgM-capture enzyme-linked immunosorbent assay (ELISA) test while IgG antibodies were detected by an indirect IgG ELISA assay [1,3]. The ELISA tests have a high specificity and therefore is useful as a screening test [27]. The rate of positive IgM was 60%–71% by day 4 and 100% by day 12 of illness. For IgG, it was 7%–29% by day 1 and 100% by day 25–26 of illness [28]. A serum neutralization assay for Nipah virus antibodies based on second generation pseudotype virus has been developed. It appears to be a sensitive and safe method for diagnosis of Nipah virus infection, and was used in the Philippines outbreak [14,29].
Unveiling the underpinnings of various non-conventional ELISA variants: a review article
Published in Expert Review of Molecular Diagnostics, 2022
Rajesh Ahirwar, Akanksha Bhattacharya, Saroj Kumar
ELISA is a mainstream technique in clinical diagnosis, biomedical research, environmental monitoring, food control, drug discovery, and forensics analyses. These assays however require air-conditioned laboratories, facility for refrigerated storage of chemicals and reagents, stable electrical power, sophisticated and calibrated equipments, and highly trained personnel. While the western nations do support all these pre-requisites, the developing world still lags for both availability as well as affordability of basic facilities and infrastructure for these sophisticated diagnostic assays. The need to establish a balance between availability, accessibility, affordability, and acceptability, various modified versions of ELISA were tested and adopted by different laboratories across the globe. Important alternates of conventional ELISA, such as microfluidic-ELISA, paper-ELISA, aptamer-ELISA and some more time-tested protocols that allows inexpensive, but accurate and reliable diagnostic need of the developing world are overviewed in this review.
Relationship between Serum Tumor-Related Markers and Genetically Modified Rice Expressing Cry1Ab Protein in Sprague-Dawley Rats
Published in Nutrition and Cancer, 2022
Bahador Hajimohammadi, Gilda Eslami, Elahe Loni, Mohammad Hassan Ehrampoush, Seyed Mohammad Moshtaghioun, Hossein Fallahzadeh, Seyed Ali Yasini Ardakani, Saeedeh Sadat Hosseini, Vahideh Askari
The strengths of this study include good maximum sample size, parallel analyses among male and female rats, and three different diet groups that were analyzed. It can provide a more clear comparison between the probable toxicological and carcinogenic effects of each feeding group. In addition, in this study, the ELISA technique was used to detect cancer tumor markers. This assay, which can be performed in minutes, is accurate in diagnosis. ELISA tests are more accurate and are considered highly sensitive and specific. In the study carried out by Hajimohammadi et al., 2021, fed SD rats with GM rice, and the pathology of various tissues including heart, spleen, thyroid, intestine, and stomachs was examined. They concluded that GM Bt rice did not show obvious adverse effects on rat health. They also investigated a range of clinical tests, including hematology, serum chemistry parameters, urinalysis profile, thyroid, and sex hormone levels, and the results showed no significant differences among the groups (12). The present research used ELISA as a precision technique for detecting tumor markers and the obtained results are consistent with pathological results performed by other researchers. Although some studies claimed that GM foods are related to carcinogenesis (24), the current research demystifies these arguments based on the results and mentioned reports.
Diagnosis, prevention, and treatment of coronavirus disease: a review
Published in Expert Review of Anti-infective Therapy, 2022
Manoj Kumar Sarangi, Sasmita Padhi, Shrivardhan Dheeman, Santosh Kumar Karn, L. D. Patel, Dong Kee Yi, Sitansu Sekhar Nanda
Repeated RT-qPCR with high-resolution CT is used for screening patients with negative RT-qPCR results. However, CT has a few limitations: it does not provide specific information to differentiate between COVID-19 pneumonia and other viral pneumonias. Enzyme-linked immunosorbent assay (ELISA) is still in trend for the diagnosis of SARS-CoV-2 infection, using IgM/IgG assay kits. ELISA is commonly used for serological testing and takes 2–5 h on average. It typically involves a surface coated with specific viral antigen(s), and corresponding patient antibodies (IgG, IgM, IgA) present in blood, plasma, or serum samples bind to these antigens. The antigen–antibody complex is then detected using a secondary antibody and substrate that produces a color or fluorescent signal. There are various types of ELISA, including direct, competitive, and double-antigen sandwich ELISA (used most commonly) [38].