Rapid and specific antibody testing is crucial for improved understanding, control, and treatment of COVID-19 pathogenesis. Herein, we describe and apply a rapid, sensitive, and accurate virus neutralization assay for SARS-CoV-2 antibodies. The assay is based on an HIV-1 lentiviral vector that contains a secreted intron Gaussia luciferase (Gluc) or secreted nano-luciferase reporter cassette, pseudotyped with the SARS-CoV-2 spike (S) glycoprotein, and is validated with a plaque-reduction assay using an authentic, infectious SARS-CoV-2 strain. The assay was used to evaluate SARS-CoV-2 antibodies in serum from individuals with a broad range of COVID-19 symptoms; patients included those in the intensive care unit (ICU), health care workers (HCWs), and convalescent plasma donors. The highest neutralizing antibody titers were observed among ICU patients, followed by general hospitalized patients, HCWs, and convalescent plasma donors. Our study highlights a wide phenotypic variation in human antibody responses against SARS-CoV-2 and demonstrates the efficacy of a potentially novel lentivirus pseudotype assay for high-throughput serological surveys of neutralizing antibody titers in large cohorts.

T cell SERINC proteins were recently identified as human immunodeficiency virus (HIV) restriction factors that diminish viral infectivity by incorporation into virions. Here we provide evidence that SERINC3 and SERINC5 perform additional antiviral activity by enhancing the type I interferon (IFN-I) and NF-κB signaling pathways. SERINC5 interacts with the mitochondrial antiviral-signaling (MAVS) and TRAF6 proteins, resulting in MAVS aggregation and TRAF6 polyubiquitination. Knockdown of SERINC5 in the target cell increases single-round HIV-1 infectivity, as well as infection by recombinant vesicular stomatitis virus (rVSV) bearing VSV-G or Ebola virus (EBOV) glycoprotein (GP). Infection by an endemic Asian strain of Zika virus (ZIKV) FSS13025 is also enhanced by SERINC5 knockdown, suggesting that SERINC5 has direct antiviral activity. Further experiments indicated that the antiviral activity of SERINC5 is IFN-I dependent. Altogether, our work uncovered a new function of SERINC proteins that promotes IFN-I and NF-B inflammatory signaling, thus contributing to SERINC-mediated antiviral activity.