Protein microarray in the detailed study of the SARS-CoV-2

–Camelia Bhattacharyya, Amity University Kolkata

With the recent outbreak of the coronavirus and the rapid spread of the infection, the importance of quicker and more accurate tests are in demand. These tests should not just include the diagnosis of the coronavirus disease but also the identification of different strains of the virus for its detailed study. While enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction(RT-PCR) are the most common methods for the detection of the presence of coronavirus in the body, detailed study of the level of infection and its effects can be done easily and more accurately by the coronavirus antigen microarray [Oliveira et al. 2020]. To learn how it works, we first need to learn what a protein microarray is.

Protein microarray method (PMM): This is one of the very modern techniques used in proteomics. It is of three types, analytical protein array, functional protein array, and reverse-phase protein lysate microarray [RPPLM]. While analytical microarrays are greatly used to study protein expression through the production of antibodies via phage antibody-display, ribosome display, systematic evolution of ligands by exponential enrichment (SELEX), mRNA display, and affibody display to identify the proteins of interest, functional protein microarrays are used to study the interactions between a protein and another biomolecule like a protein, DNA or even lipids [Chen and Zhu.2006]. The RPPLM is used for the measurement of the expression of proteins when the number of samples is large.

Protocols to be followed: At first the protein is extracted from biological samples such as serum or plasma, fluorescent dyes are then added to label the sample, immobilization of the antibody on the array surface is done and then the sample is incubated on the protein microarray. The chip is now scanned and the image is then studied. 

Role of PMM in COVID-19 detection: The detection of coronaviruses not only helps to classify the types of coronaviruses causing the infection (whether only SARS-CoV-2 is present or some other viruses from the same family are also playing as an actor) but also helps in the study of the impact or infection rate due to different coronaviruses and the response of the antibody (IgG or immunoglobulin G shows higher reactivity for other coronaviruses when compared with its reactivity to SARS-CoV-2) developed over time which might also help in the planning of the vaccine through the identification of specific antigens to be used [Khan et al. 2020]. In a study of the SARS-CoV-2 genome, several protein sequences like ORF1ab protein, surface glycoprotein, and others were elongated and transcribed into about 5000 peptides made up of 15 amino acids. A high-resolution epitome data was obtained which was comparatively easier, more accurate, and less time consuming than most other methods like the ELISA and rtPCR [Kubina and Dziedzic 2020].

Although the PMM has many advantages, this method is not accessible to all due to the high expenses of the equipment and the test. Also, the test faces some challenges due to its repeatability.

References:

• Chen C-S, Zhu H. Protein Microarrays. BioTechniques  Vol. 40, No. 4 (2006). doi:10.2144/06404TE01
• B, Spurrier, S. Ramalingam, S. Nishizuka (2008). Reverse-phase protein microarrays for cell signalling analysis. Nature Protocols. Nature publishing Group. 3(11): 1796-1808. Doi:10.1038/nprot.2008.179
• Khan S, Nakajima R, Jain A, et al. analysis of Serologic Cross-Reactivity Between Common Human Coronavirus Antigen Microarray. Preprint. bioRxiv.2020;2020.03.24.006544. Published 2020 Mar 25. doi:10.1101/2020.03.24.006544
• Oliveira BA, Oliveira LC, Sabino EC, Okay TS. SARS-CoV-2 and the COVID-19 disease: a mini review on diagnostic methods. Rev Inst Med Trop Sao Paulo. 2020;62:e44. Published 2020 Jun 29. doi:10.1590/S1678-9946202062044
• Kubina R, Dziedzic A. Molecular and Serological Tests for COVID-19. A Comparative Review of SARS-CoV-2 Coronavirus Laboratory and Point-of-Care Diagnostics.  Diagnostics 2020, 10, 434; doi:10.3390/diagnostics10060434