Biomimetic Virus-like Particles as SARS-CoV-2 Positive Controls for RT-PCR Diagnostics

Coronavirus disease 2019 (COVID-19) is a highly transmissible disease that has affected more than 90% of the countries worldwide. At least 17 million individuals have been infected, and some countries are still battling first or second waves of the pandemic. Nucleic acid tests, especially reverse-transcription polymerase chain reaction (RT-PCR), have become the workhorse for early detection of COVID-19 infection. Positive controls for the molecular assays have been developed to validate each test and to provide high accuracy. However, most available positive controls require cold-chain distribution and cannot serve as full-process control. To overcome these shortcomings, we report the production of biomimetic virus-like particles (VLPs) as SARS-CoV-2 positive controls. A SARS-CoV-2 detection module for RT-PCR was encapsidated into VLPs from a bacteriophage and a plant virus. The chimeric VLPs were obtained either by in vivo reconstitution and co-expression of the target detection module and coat proteins or by in vitro assembly of purified detection module RNA sequences and coat proteins. These VLP-based positive controls mimic SARS-CoV-2 packaged RNA while being non-infectious. Most importantly, we demonstrated that the positive controls are scalable, stable, and can serve broadly as controls, from RNA extraction to PCR in clinical settings.