NIH Scientists Identify Atomic Structure of Novel Coronavirus Protein

 
NIAID scientists working with investigators from the University of Texas at Austin (UT) have identified the atomic structure of an important protein on the surface of the novel coronavirus (SARS-CoV-2, formerly called 2019-nCoV).¹ The authors note that the findings will aid in the design of candidate vaccines and the development of treatments for COVID-19, the disease caused by the new virus, which was first identified in China in December 2019.

Like other coronaviruses, SARS-CoV-2 particles are spherical and have mushroom-shaped proteins called spikes protruding from their surface, giving the particles a crown-like appearance. The spike binds and fuses to human cells, allowing the virus to gain entry. However, coronavirus infection can be prevented or slowed if this process is disrupted.

Scientists in China shared the genome of a SARS-CoV-2 virus isolate to a global database, which NIAID and UT experts used to start their work determining the spike structure. The spike undergoes a massive rearrangement as it fuses the virus and cell membranes. The researchers confirmed that the original spike stabilized in its prefusion conformation is more likely to preserve targets for infection-blocking antibodies induced by a vaccine.

The atomic-level structure of the SARS-CoV-2 spike protein in its prefusion conformation. Illustration courtesy University of Texas, Austin, McLellan Lab.

Importantly, the new data supports NIAID’s approach to a gene-based vaccine for COVID-19 and will also be useful in other vaccine approaches including protein-based vaccines and other nucleic acid or vector-based delivery approaches. NIAID scientists designed the stabilized spike antigen based on previous knowledge obtained from studying other coronavirus spike structures. NIAID and the biotechnology company Moderna, Cambridge, Mass, are developing a messenger RNA vaccine, which directs the body’s cells to express the spike in its prefusion conformation to elicit an immune response.

The new research also confirms that the structure of the SARS-CoV-2 spike is very similar to that of the coronavirus responsible for the global outbreak of severe acute respiratory syndrome in 2003 that was eventually contained (known as SARS-CoV). However, despite the similarities, the paper shows that some monoclonal antibodies developed to target SARS-CoV do not bind to the new coronavirus, indicating that antibodies that recognize the SARS-CoV from 2003 will not necessarily be effective in preventing or treating COVID-19, the disease caused by the new virus.

Recent reports show that the novel virus and SARS-CoV also bind to the same receptor on the host cell. However, NIAID and UT scientists determined that SARS-CoV-2 binds more easily to this receptor as compared to SARS-CoV, which could potentially explain why SARS-CoV-2 appears to spread more efficiently from human to human. However, more data is needed to investigate this possibility, the authors note.

The research was supported by the NIAID intramural research program and a NIAID grant to the University of Texas at Austin (R01-AI127521).

Reference

1. Wrapp D, Wang N, Corbett KS, et al. Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation. Science. Epub February 19, 2020; doi: 10.1126/science.abb2507.