ABSTRACT
We identify the prolyl-tRNA synthetase (PRS) inhibitor halofuginone, a compound in clinical trials for anti-fibrotic and anti-inflammatory applications, as a potent inhibitor of SARS-CoV-2 infection and replication. The interaction of SARS-CoV-2 spike protein with cell surface heparan sulfate (HS) promotes viral entry. We find that halofuginone reduces HS biosynthesis, thereby reducing spike protein binding, SARS-CoV-2 pseudotyped virus, and authentic SARS-CoV-2 infection. Halofuginone also potently suppresses SARS-CoV-2 replication post-entry. Utilizing analogues of halofuginone and small molecule inhibitors of the PRS, we establish that inhibition of HS presentation and viral replication is dependent on proline tRNA synthesis opposed to PRS activation of the integrated stress response (ISR). Moreover, we provide evidence that these effects are mediated by the depletion of proline tRNAs. In line with this, we find that SARS-CoV-2 polyproteins, as well as several HS proteoglycans, are particularly proline-rich, which may make them vulnerable to halofuginone translational suppression. Halofuginone is orally bioavailable, has been evaluated in a phase I clinical trial in humans and distributes to SARS-CoV-2 target organs, including the lung, making it a promising clinical trial candidate for the treatment of COVID-19.
Subject(s)
COVID-19ABSTRACT
The human beta coronavirus SARS-CoV-2, causative virus of COVID-19, has infected more than 15 million people globally and continues to spread. Widespread, population level testing to detect active and past infections is critical to curb the COVID-19 pandemic. Antibody (serological) testing is the only option for detecting past infections outside the narrow window accessible to nucleic acid-based tests. However, currently available serological assays commonly lack scalability. Here, we describe the development of a rapid homogenous serological assay for the detection of antibodies to SARS-CoV-2 in patient plasma. We show that the fluorescence-based assay accurately detects seroconversion in COVID-19 patients from less than 1 microliter of plasma. Using a cohort of samples from COVID-19 infected or healthy individuals, we demonstrate detection with 100% sensitivity and specificity. This assay addresses an important need for a robust, low barrier to implementation, and scalable serological assay with complementary strengths to currently available serological platforms.