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Background & Objectives: The genome of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), belonging to the family Coronaviridae, encodes for structural, non-structural, and accessory proteins, which are required for replication of the virus. These proteins are encoded by different genes present on the SARS-CoV-2 genome. The expression pattern of these genes in the host cells needs to be assessed. This study was undertaken to understand the transcription pattern of the SARS-CoV-2 genes in the Vero CCL-81 cells during the course of infection., Methods: Vero CCL-81 cells were infected with the SARS-CoV-2 virus inoculum having a 0.1 multiplicity of infection. The supernatants and cell pellets were harvested after centrifugation at different time points, post-infection. The 50% tissue culture infective dose (TCID 50 )and cycle threshold (C t ) values of the E and the RdRp-2 genes were calculated. Next-generation sequencing of the harvested sample was carried out to observe the expression pattern of the virus by mapping to the SARS-CoV-2 Wuhan HU-1 reference sequence. The expressions were in terms of the reads per kilobase million (RPKM) values., Results: In the inital six hours post-infection, the copy numbers of E and RdRp-2 genes were approximately constant, which raised 10 log-fold and continued to increase till the 12 h post-infection (hpi). The TCID 50 was observed in the supernatant after 7 hpi, indicating the release of the viral progeny. ORF8 and ORF7a, along with the nucleocapsid transcript, were found to express at higher levels., Interpretation & Conclusions: This study was a step towards understanding the growth kinetics of the SARS-CoV-2 replication cycle. The findings indicated that ORF8 and ORF7b gene transcripts were expressed in higher amounts indicating their essential role in viral replication. Future studies need to be conducted to explore their role in the SARS-CoV-2 replication., Competing Interests: None

Background & Objectives: Since the beginning of the year 2020, the pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) impacted humankind adversely in almost all spheres of life. The virus belongs to the genus Betacoronavirus of the family Coronaviridae. SARS-CoV-2 causes the disease known as coronavirus disease 2019 (COVID-19) with mild-to-severe respiratory illness. The currently available diagnostic tools for the diagnosis of COVID-19 are mainly based on molecular assays. Real-time reverse transcription-polymerase chain reaction is the only diagnostic method currently recommended by the World Health Organization for COVID-19. With the rapid spread of SARS-CoV-2, it is necessary to utilize other tests, which would determine the burden of the disease as well as the spread of the outbreak. Considering the need for the development of such a screening test, an attempt was made to develop and evaluate an IgG-based ELISA for COVID-19., Methods: A total of 513 blood samples (131 positive, 382 negative for SARS-CoV-2) were collected and tested by microneutralization test (MNT). Antigen stock of SARS-CoV-2 was prepared by propagating the virus in Vero CCL-81 cells. An IgG capture ELISA was developed for serological detection of anti-SARS-CoV-2 IgG in serum samples. The end point cut-off values were determined by using receiver operating characteristic (ROC) curve. Inter-assay variability was determined., Results: The developed ELISA was found to be 92.37 per cent sensitive, 97.9 per cent specific, robust and reproducible. The positive and negative predictive values were 94.44 and 98.14 per cent, respectively., Interpretation & Conclusions: This indigenously developed IgG ELISA was found to be sensitive and specific for the detection of anti-SARS-CoV-2 IgG in human serum samples. This assay may be used for determining seroprevalence of SARS-CoV-2 in a population exposed to the virus., Competing Interests: None