Abstract: Compositions and immunoassays for detecting SARS-CoV-2 antigen-specific antibodies in a biological sample are provided. The compositions are antigens from SARS-CoV-2 such as the proteins N, M, S, S1, S2?, NSP1, ORF3a, ORF3b, ORF7a, ORF7b and ORF8, fused to a light emitting protein. The compositions are useful in immunoassays for detecting antibodies to the SARS-CoV-2 antigens. A preferred immunoassay is the luciferase immunoprecipitation systems (LIPS) to detect SARS-CoV-2 antigen-specific antibodies with high sensitivity and specificity. The current or present exposure or infection with SARS-CoV-2 can be detected and/or diagnosed using the disclosed compositions and methods. Typically, the presence and/or elevated amount of SARS-CoV-2 antibodies in the individual’s biological sample compared to a control is indicative of current or past exposure or infection with SARS-CoV-2 as discussed herein.