What Makes The Novel Coronavirus So Contagious?

Prion-like features may contribute to the transmissibility of COVID-19

Summary

The novel coronavirus that causes COVID-19, SARS-CoV-2, is significantly more contagious than the seasonal flu, and a preprint from the Human Microbiology Institute of New York may explain why. In this unpublished study, the authors examined the proteomic structure of the SARS-CoV-2 virus with computer modeling. They discovered that, unlike other closely related coronaviruses, SARS-CoV-2 contains prion-like domains in its receptor-binding spike proteins. These prion-like domains may contribute to a nearly 20-fold increase in affinity for the protein receptor found in human cells, ACE2. This unique structural element may contribute to the human-to-human communicability of COVID-19. So what are prions and why does it matter? Let’s start from the beginning.

How Coronaviruses Get Into Our Cells

At this point, we all know about the novel coronavirus causing the COVID-19 pandemic. The name “coronavirus” comes from the Latin word for crown or wreath, which refers to the visible structure of the viral particles in a cross-sectional microscopy image. But this two-dimensional description conceals the real shape of the viral particles — they’re more like spiky spheres than crowns or wreaths.

An electron micrograph of bronchitis viral particles. Image Credit: Wikimedia Commons

An artist’s rendition of a coronavirus. Image Credit: Nature

These spiky protrusions, aptly named spike proteins, play an important role in the replication cycle of all coronaviruses. As a quick and basic refresher, a virus doesn’t make copies of itself like most living things. Instead, it commandeers the cellular machinery of other lifeforms and uses the hijacked infrastructure to churn out more viral particles.

This parasitism allows viruses to be incredibly simple constructions with very small genomes. Because, unlike most of the genomes found in nature, viral genomes don’t need to encode for metabolic pathways, signaling molecules, or DNA replication machinery. The viral genome only needs to contain instructions for a few simple proteins. To put this into perspective, several…