During the coronavirus disease-2019 (COVID-19) pandemic, severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) has led to the infection of millions of people and has claimed hundreds of thousands of lives. The entry of the virus into cells depends on the receptor-binding domain (RBD) of the spike (S) protein of SARS-CoV-2. Although there is currently no vaccine, it is likely that antibodies will be essential for protection. However, little is known about the human antibody response to SARS-CoV-2 1-5. Here we report on 149 COVID-19-convalescent individuals. Plasma samples collected an average of 39 days after the onset of symptoms had variable half-maximal pseudovirus neutralizing titres; titres were less than 50 in 33% of samples, below 1,000 in 79% of samples and only 1% of samples had titres above 5,000. Antibody sequencing revealed the expansion of clones of RBD-specific memory B cells that expressed closely related antibodies in different individuals. Despite low plasma titres, antibodies to three distinct epitopes on the RBD neutralized the virus with half-maximal inhibitory concentrations (IC 50 values) as low as 2 ng ml −1. In conclusion, most convalescent plasma samples obtained from individuals who recover from COVID-19 do not contain high levels of neutralizing activity. Nevertheless, rare but recurring RBD-specific antibodies with potent antiviral activity were found in all individuals tested, suggesting that a vaccine designed to elicit such antibodies could be broadly effective.

The type I interferon (IFN) response protects cells from invading viral pathogens. The cellular factors that mediate this defense are the products of interferon-stimulated genes (ISGs). Although hundreds of ISGs have been identified since their discovery over 25 years ago1,2,3, only few have been characterized with respect to antiviral activity. For most, little is known about their antiviral potential, their target specificity, and their mechanisms of action. Using an overexpression screening approach, we show that different viruses are targeted by unique sets of ISGs, with each viral species susceptible to multiple antiviral genes with a range of inhibitory activities. To conduct the screen, over 380 ISGs were tested for their ability to inhibit the replication of several important viruses including hepatitis C virus (HCV), yellow fever virus (YFV), West Nile virus (WNV), chikungunya virus (CHIKV), Venezuelan equine encephalitis virus (VEEV), and human immunodeficiency virus (HIV-1). Broadly acting effectors included IRF1, C6orf150, HPSE, RIG-I, MDA5, and IFITM3, while more targeted antiviral specificity was observed with DDX60, IFI44L, IFI6, IFITM2, MAP3K14, MOV10, NAMPT, OASL, RTP4, TREX1, and UNC84B. Combined expression of two-ISG pairs showed additive antiviral effects similar to moderate IFN doses. Mechanistic studies revealed a common theme of translational inhibition for numerous effectors. Several ISGs, including ADAR, FAM46C, LY6E, and MCOLN2, enhanced replication of certain viruses, highlighting another layer of complexity in the highly pleiotropic IFN system.