Diagnosing COVID-19: The Lab Experiment

Subject: Diagnostics
Pages: 7
Words: 2001
Reading time:
9 min

The new primers’ analytical sensitivity was compared to that of previously reported N gene primers. 348 respiratory specimens were examined using this RT-PCR-hybridization approach, and 12 human coronaviruses were identified. RT-PCR-hybridization was used to amplify the M polypeptide sequences of HCoV-OC43 and the other strain of coronavirus, HCoV-229E. This strategy may be advantageous for demonstrating human hemorrhagic fever’s capacity to cause respiratory tract infections. The results suggest that using the original approach, this molecular technology is capable of detecting significance level TCID50 when 0.01 TCID50 or HCoV-229E of HCoV-OC43. This method allows the detection of HCoV-OC43 strains and HCoV-229Estrains infection in clinical specimens.

Human coronaviruses were originally identified in patients suffering from rhinitis. They represent members of the virus family that infects humans and a variety of animal species. Epidemiological studies have shown that some viruses are highly contagious during seasonal outbreaks. Coronaviruses are enclosed pleiomorphic viruses that include a substantial (30 kb) RNA portion. Human strains are divided into two antigenic groupings, each represented by a prototype virus, HCoV-229E or HCoV-OC43. They are suspected of causing respiratory tract, digestive, and central nervous system diseases. Except for rhinitis, humans coronavirus infection has been associated with more severe pulmonary disease (Alvarez, Bravo-González, González-González, & Trujillo-de Santiago, 2021). As with other chronic bronchitis, they are associated with hyperactivity of the bronchitis in non-atopic persons.

Only a few highly pathogenic virus detection methods are available at the time. As a consequence, these viruses are hardly ever discovered in diagnostic laboratories, and their clinical manifestations are unclear. Numerous molecular detection strategies for human coronavirus testing have been developed recently, including simple and nested PCR amplification employing primers placed in the N protein gene. This article discusses two methods for doing a professional and straightforward diagnosis of two kinds of human coronavirus. They begin with PCR using primers that were determined in the M protein genes and continue with genomic hybridization utilizing nonradio isotopic probes. The intrinsically related sequences of the M sequences from 229E and its counterpart OC43 have a similarity of 43%, which is insufficient to imply a shared detection mechanism (Chu et al., 2020). These detection techniques were developed on both the prototype strains HCoV-OC43 and the strain HCoV-229E and compared to the other strategy that used previously reported N protein gene primers (Corman & Drosten, 2020). The purpose of this experiment was to extract viral RNA and multiply it using the rPCR, which is the gold standard approach for diagnosing covid 19. The amplified genetic constructs will next be compared and contrasted.


RNA extraction

Naso- and oropharyngeal swabs were used to collect specimens. Each swab was rinsed for approximately 10 seconds in 1 cc 0.9 percent NaCl. Following that, 350 l of NaClspecimen extract was diluted to the Nimbus RNA extractor. RNA was extracted using STARMag 96 magnetized silica beads. Purified RNA was utilized in routine SARS-CoV-2 diagnostics and was thereafter kept at -80 °C.

Primer and probe design

Using Primers express 2.0 software, we searched the membrane protein genes of HCoV229E and HCoVOC43 for primers and probe target locations that would be consistent with TaqMan qPCR criteria. Primers with a target area of 68 bp of HCoVOC43 and 70 bp in HCoV229E were chosen. The primers showed similar breakdown temperatures and a low probability of forming duplexes or hairpins.

qRT-PCR for routinely status determination

Pure RNA was loaded into the AllplexTM 2019-nCoV (SEEGENE) assay using the purified RNA. The qRT-PCR preparation was carried out on the micro laboratory Nimbus (SEEGENE) liquid handling equipment, and the qRT-PCR was carried out with 45 repetitions on the CFX96TM qRT-PCR apparatus.

Cytecs RT-PCR

The Cytecs RT-PCR is a two-step RT-PCR that has been lyophilized. cDNA transcription and PCR master mixes are already produced and frozen dried using 0.2 ml experiment tubes. Two separate PCR tests, E N and ORF1b-nsp14, were conducted. Following cDNA synthesis with the amplification, the PCR products must be analysed using the standard DNA agarose gel-electrophoresis method. As is the case with the majority of tests, the Cytecs RT-PCR is a double target test. When run in a single plex batch, two PCR products may be visible on the agarose gel, indicating a positive test result.

Cytecs PCR cDNA synthesis

Randomized and oligo dT primers were employed to synthesize cDNA. We employed Invigate’s reverse transcriptase. The Cytecs SARS-CoV2 real-time PCR tubes (Cytecs, Münster, German) were rehydrated using 15 l of PCR grade water. RNA samples attained from patient samples of positive and negative SARS-CoV-2 were thawed, and 5 l of pure RNA was added to the cDNA synthesis. The cDNA synthesis was carried out using a Flex Cycler PCR apparatus.

E N and ORF1b-nsp14 assay

The specific primers for this assay were determined using Corman et al. [5].’s and Chu et al. [6] (Pfefferle, Reucher, Nörz & Lütgehetmann, 2020).’s publications. Segenetics provided DNA Taq-Polymerase. Rehydrate tubes for ORF1b-nsp14 and E N assays with 23 l PCR grade water. Following that, 2 l of plasmid DNA was introduced as a template. The amplification was performed 45 times on a T-Personal 48 PCR-thermocycler.


DNA agarose gel electrophoresis and documenting were carried out using the E-CUBE (Cytecs) all-in-one gel electrophoresis and documentary evidence system. We employed commercial agarose gels at a concentration of 3% in a TBE buffer solution. Gels and electrophoresis reagents were obtained from the E-CUBE Gel-Electrophoresis System (Cytecs). After 30 minutes, PCR separation is based and evaluated by matching Amplified product patterns to a 1 kb DNA marker.


Correlation investigation of 244 RNA samples revealed a 97.9 percent correlation across Cytecs RT-PCR and stated previously RNA extracted from patient specimens infected with AllplexTM 2019-nCoV. By doing standard testing on these 244 RNAs, 46 were identified as affirmative and 198 as negative. This is consistent with the FIND approach for evaluating molecular testing. The Cytecs SARS-CoV-2 reverse transcription-polymerase chain reaction (RT-PCR) failed in two positive patients and three of 198 SARS-CoV-2 negatives cases. Sensitivity and specificity are determined to be 95.5 percent and 98.5 percent, respectively, when compared to AllplexTM 2019-nCoV. The projected positive and negative values are 0.93 and 0.99, correspondingly.

Gel electrophoresis results

It is simple to evaluate an agarose gel loaded with PCR results since the positive samples of SARS-CoV-2 exhibit distinct bands for the assays of E N and ORF1b-nsp14. As mentioned before, the Cytecs RT-PCR is a double target test run in two separate batches. However, this test was ineffective during the gel electrophoresis step, and as a consequence, no data were acquired during this period.

Design Primers for the 0c43 and 229E.

Forward Reverse


The respiratory depression caused by a coronavirus is typically difficult to identify. barely a few wild strains, with the exception of prototype strains, grow in culture. The standard for detection is electron microscopy. Scanning electron microscope is a precise technique that requires the skills of a skilled operator. Coronavirus images seem to be very difficult to identify from that of other cell components in respiratory samples. Direct immunofluorescence identification of viral antigens on respiratory cells is insufficient, and many diagnostic centers avoid performing this test. Between 1999 and 2000, our laboratory used a single commercial immunoassay (PIV-11646, Argène France) to undertake a thorough screening for coronavirus 229E in pulmonary aspirates from hospitalized children and ventilatory discharges and liquids from hospitalized adults. Out of 7120 samples analyzed, only five tracheobronchial fluids and one nasal aspirate were positive for HCoV-229E (González-González et al., 2019). The sensitivity of this immunoglobulin in viral diagnosis is unknown, and for the epitopes observed is possible to be produced poorly or not at all by infections are caused by wild-type HCoV-229E. Additionally, the specificity of the monoclonal antibody is uncertain.

To corroborate immunofluorescence results and provide a diagnostic strategy for respiratory specimens, we developed a potent and selective RT-PCR-hybridization sensing technology. Due to the considerable danger of contamination involved with testing large sets of data, the use of nested PCR equivalent to that reported in the literature has been abandoned (Mohsen, 2020). Each translated PCR product is hybridized to a probe appropriate for HCoV-229E or the counter strain of this study, HCoV-OC43, enabling for fine-tuning of its specificity while enhancing its sensitivities (Nandagopal, 2021). The test is quite simple and does not require the use of radioactive materials.

Primers for amplification sentient hemorrhagic fever have been selected in the literature mostly for the N ribonucleoprotein peptide gene. Two factors support this choice: the peptide is highly conserved in definition, and the associated RNAm is plentiful in the immunocompromised person (Lo & Chiu, 2020). We chose to evaluate the two primers against a system specified by the M protein gene. By far the most profuse protein component of the virion is the M protein (González-González et al., 2020). It is a transmembrane protein with an N-terminal hydrophilic ectodomain and three hydrophilic sections composed of three intracellular helixes (Shin, Jung, Kim, Baric & Go, 2018). The nucleotidic sequence of its gene is known to be retained. The results suggest that these primers allow an extremely sensitive detection test at 0.05 Secure data transmission for 0.11 TCID50 and HCoV-229E and the counter stray, HCoV-OC43 in the prototypes strain and detection. As a consequence, these techniques allow the detection of a large number of harmful microorganisms (Udugama, Kadhiresan, Kozlowski, Malekjahani, Osborne, Li, Chen, Mubareka, Gubbay, & Chan 2020). The phenomenon can be explained by the production of a large number of defective particles during cell growth. These particles have identifiable genetic material, but they are incapable of invading other cells.

One downside of this technique is that it necessitates the development of two distinct detection mechanisms for the two hemorrhagic fever strains. Due to the low degree of commonly referred sequence homology between the N or M peptide genes, a common detection approach cannot be used (Corman et al., 2020). This technology is exciting since it has the potential to find a new coronavirus, or at the very least a mutation of the prototype strains, but the sensitivity of the method has not been determined (Lai, Shih, Ko, Tang & Hsueh, 2020). When a suspected contagious viral infection is suspected, standard diagnostic techniques provide a diagnosis in less than 40% of acquired samples (Kuznetsova, AA, MA & VA, 2020). The advancements in molecular techniques for identifying viruses that are undetectable by traditional detection methods seem to be useful.

The data generated by RT-PCR-hybridization of both M peptide gene on a variety of respiratory samples may be utilized to validate the technique’s use. These researchers were looking for coronaviruses 229E or OC43 in a large number of samples from a prospective study of 24-month-old babies who were observed and samples throughout each viral outbreak (Lai et al., 2020). The RT-PCR duplex including HCoV-229E and the other strain under study; HCoV-OC43 was used, followed by microplate-based molecular synthesis (Pfefferle, Reucher, Nörz, & Lütgehetmann, 2020). The primers are N core protein peptide gene specific and are not similar to that used in this study.

Coronavirus was found in 2.6 percent of samples, with approximately half of the samples obtained from children with a variety of infectious illnesses such as respiratory infections, pneumonitis, quinsy, laryngitis, conjunctivitis, and exanthema (Corman et al., 2020). To determine the sensitivity of the different molecular techniques discussed above for the diagnosis of respiratory pathogens OC43 and the other strain, 229E, it is desirable to utilize a substantial percentage of respiratory specimens concurrently, since the percentage of positive samples discovered in studies is modest, around 3%. (Corman et al., 2020). Additionally, it is critical to correlate these data with patients’ clinical complaints and to conduct studies on controls who do not display respiratory clinical manifestations.

To sum up, despite the culture isolation and also the search for intracellular viral proteins continue to be the primary standard for pulmonary classical viral infections. Any use of molecular diagnostic methods for viruses, including coronavirus, seems to be suitable in establishing the therapeutic value and significance of these kind of viruses in ventilatory illness.


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