Covid-19: What you need to know today
The two papers are already beginning to make waves in epidemiological circles, and have also been reported by some specialised websites.Updated: Oct 22, 2020, 01:32 IST
As some of the regular readers of this column know, my reading has expanded since March to include dense academic papers published in serious journals that make me wish I had paid more attention to science and math during my college years. Late Tuesday/early Wednesday, two papers that dropped on the journal Science’s website piqued my interest. One was titled “Neuropilin-1 is a host factor for SARS-CoV-2 infection” and another “Neuropilin-1 facilitates SARS-CoV-2 cell entry and infectivity”. The two papers are already beginning to make waves in epidemiological circles, and have also been reported by some specialised websites. There is a reason for this: 10 months into the pandemic’s run, there are still many unanswered questions about Covid-19 and the coronavirus that causes it. This isn’t surprising. What is surprising is the pace of scientific research that has helped us answer many other questions about Covid-19 and Sars-CoV-2. Among the important unanswered (or partially unanswered, because we do know some part of the answer) questions are those about the virus’s infectivity, and its ability to do more damage than typical respiratory infections do (which it does by targeting other body organs). And the two papers in Science provide answers to these, which would make them among the most important pieces of research on the coronavirus to be published in recent months.
The second paper, published by researchers from Munich’s Technical University, University of Helsinki, and other institutions, finds that neuropilin-1 (NRP1) boosts the infectivity of Sars-CoV-2. Neuropilin 1 is a protein widely present in human cells. Previous studies have shown that the Sars-CoV-2 virus has a furin cleavage site. The S-protein of the virus has a site which can be cleaved by furin (a common human protein; it is an enzyme). Think of furin, then, as a can opener of sorts. The component of the viral protein thus cleaved interacts with ACE2, a cell surface receptor. ACE stands for angiotensin-converting enzyme. And it is this receptor that provides a channel for the viral protein to enter the cell. Clearly, furin is needed for cleavage (or breaking the spike protein), and ACE 2 for facilitating entry into the cell. And the paper found that infection of the virus increased in the presence of NRP1.
The first paper, by researchers from the University of Bristol and others, showed that while furin cleaves the S protein into “two associated” proteins, S1 and S2, one of these proteins (S1) binds well with neuropilin 1, facilitating the entry of the virus into cells, and boosting infectivity. Two independent studies then have arrived at the same conclusion. And because NRP1 is found in cells in several parts of the human body, it isn’t surprising that Sars-CoV-2 is able to target several body organs and systems.
Interestingly, the second study found (on the basis of pathological analysis) that olfactory nerve cells in the nasal cavity that were infected by Sars-CoV-2 had NRP1 – something that could explain why the loss of a sense of smell is seen in some Covid-19 patients – and that a “SARS-CoV-2 mutant with an altered furin cleavage site did not depend on NRP1 for infectivity”, a finding that shows a strong relationship between the presence of neuropilin 1 and the infectivity of the virus that causes Covid.
As the first paper puts it: “NRP1 thus serves as a host factor for Sars-CoV-2 infection and may provide a therapeutic target for COVID-19.”
This could simply involve something that blocks NRP1. For instance, the second study found that an antibody that blocked neuropilin reduced Sars-CoV-2 infection by around 40%. Even as we pin hopes on a vaccine for Covid-19, research such as that detailed above points to possible therapeutical interventions that could save lives.