SARS-CoV-2 hereditary changes may have made COVID-19 more infectious

Overview

• Post By : Kumar Jeetendra


• Source: University of Texas at Austin


• Date: 31 Oct,2020

A study involving over 5,000 COVID-19 patients in Houston finds the virus which causes the disease is accumulating genetic mutations, one of which may have made it longer infectious. According to the paper published in the peer reviewed journal mBIO, that mutation, known as D614G, is found in the spike protein that pries open our cells for viral entry. It is the largest peer-reviewed study of SARS-CoV-2 genome sequences in one metropolitan region of the U.S. thus far.

The paper reveals”the virus is mutating because of mixture of neutral drift — that just means random genetic changes that don’t help or hurt the virus — and pressure from our immune systems,” said Ilya Finkelstein, associate professor of molecular biosciences at The University of Texas at Austin and co-author of the analysis. The study was carried out by scientists at Houston Methodist Hospital, UT Austin and elsewhere.

During the initial wave of the pandemic, 71 percent of this publication coronaviruses identified in patients in Houston had this mutation. When the second wave of the outbreak hit Houston during the summer, this version had leaped to 99.9% prevalence. A study published in July based on more than 28,000 genome sequences discovered that variants carrying the D614G mutation became the worldwide dominant form of SARS-CoV-2 in about a month. SARS-CoV-2 is the coronavirus that causes COVID-19.

So why did strains containing this mutation outcompete those that didn’t have it?

Perhaps they’re more contagious. A study of over 25,000 genome sequences in the U.K. discovered that viruses with the mutation tended to transmit slightly faster than those without it and caused larger clusters of infections. Natural selection would favor strains of this virus which transmit more easily. But not all scientists are convinced. Some have suggested another explanation, known as”founder’s consequences.” In that situation, the D614G mutation could have been more common in the first viruses to arrive in Europe and North America, essentially giving them a head start on other strains.

The spike protein is also continuing to collect additional mutations of unknown significance. The Houston Methodist-UT Austin team also revealed in lab experiments that at least one such mutation allows spike to prevent a neutralizing antibody that humans naturally produce to resist SARS-CoV-2 infections. This may allow that variant of this virus to more easily slip past our immune systems. Even though it is not clear yet if that translates to it also being more readily transmitted between individuals.

The fantastic thing is that this mutation is infrequent and doesn’t seem to make the disease more severe for infected patients. According to Finkelstein, the team did not see viruses that have learned to evade first-generation vaccines and therapeutic antibody formulations.

“The virus continues to mutate as it rips through the world,” Finkelstein said. “Real-time surveillance efforts like our analysis will make sure that global vaccines and therapeutics are always 1 step ahead.”

The scientists noted a total of 285 mutations across thousands of infections, though most don’t appear to have a substantial effect on how severe the disease is. Ongoing studies are continuing to surveil the third wave of COVID-19 patients and to characterize the way the virus is adapting to neutralizing antibodies that are made by our immune systems. Each new disease is a roll of the dice, an additional chance to develop more dangerous mutations.

“We have given this virus a lot of chances,” lead author James Musser of Houston Methodist told The Washington Post. “There is a massive population size out there right now.”

The UT Austin team tested different genetic variants of this virus’s spike protein, the part that allows it to infect host cells, to gauge the protein stability and to determine how well it binds to a receptor on host cells and to neutralizing antibodies. Earlier in the year, McLellan and his group at UT Austin, in collaboration with researchers at the National Institutes of Health, developed the first 3D map of the coronavirus spike protein for an innovation that currently factors into several leading vaccine candidates’ designs.

The researchers found that SARS-CoV-2 was introduced into the Houston area many times, independently, from diverse geographic regions, with virus strains from Europe, Asia, South America and elsewhere in the United States. There was widespread community dissemination soon after COVID-19 cases were reported in Houston.

This study was supported by the Fondren Foundation, Houston Methodist Hospital and Research Institute, the National Institutes of Health, the National Institute of Allergy and Infectious Diseases, the Welch Foundation, the National Science Foundation and the Defense Advanced Research Projects Agency. Ilya Finkelstein is a CPRIT scholar in cancer research, funded by the Cancer Prevention and Research Institute of Texas.