The recombinant immunodominant regions 179-344 and 550-670 from SARS-COV2 spike protein can efficiently react with patients' sera.

SARS-COV2 is related to the COVID-19 pandemic that emerged in 2019. It caused severe criticism of world health care and the economic system. Its high mutation rate increases contagiousness and gives rise to new variants, causing recurrent epidemic waves. One of the effective strategies for prevention and controlling infections is evaluating antibody existence against SARS-CoV2 to know how much individuals are protected against new infection. Therefore, it can be helpful to conduct health care strategies for vaccination and healing infected patients. In this study, we identified two immunodominant linear B cell epitopes (S179-344 and S550-670) within the S1 subunit of the spike protein using bioinformatics tools (ABCpred and BepiPred). These regions were subsequently cloned into the pET28a(+) vector, expressed in E. coli BL21 (DE3), and then purified. The recombinant antigens were then assessed for their seroreactivity using a variety of diagnostic techniques, including Western blot, dot blot, and ELISA. The study population for this assessment included 68 positive sera from patients infected with SARS-CoV2 and 63 negative control samples, both of which were screened by standard PCR. The results obtained from the ELISA assay indicated that both antigens demonstrated strong seroreactivity with high sensitivity (91-98 %) and specificity (82 %), suggesting their potential as diagnostic tools. The combination of both antigens exhibited diagnostic accuracy, further supporting their utility in clinical settings. The results of this study underscore the remarkable antigenicity of these epitopes and underscore the suitability of the assay for evaluating community immunity levels against SARS-CoV2 and vaccine efficacy.