Study reveals how viral infections interact with human bodies

WASHINGTON DC: Much of our understanding of viral respiratory illnesses such as COVID-19 and influenza is based on investigations of symptomatic patients. A new longitudinal study of symptomatic, asymptomatic, and mild illnesses conducted by Columbia University researchers gives information on how our bodies respond to these infections at the molecular level. They describe the finding of a gene expression profile that may distinguish between symptomatic and asymptomatic illnesses, as well as positive asymptomatic persons from negative individuals.

The study presents a complex picture of how several common respiratory viruses interact with the human body, and with each other, as well as with common respiratory bacteria. The results are available as an interactive web tool(link is external and opens in a new window) for scientists to generate and test new hypotheses, and are described in a new peer-reviewed article in the journal PLOS Biology.

Over 19 months, 214 volunteers enrolled in the Virome of Manhattan study provided nasal swab samples, which were analyzed by molecular testing (RNA-seq and qPCR) along with daily individual reports of symptoms and demographic information. The majority of the infections were caused by rhinoviruses and coronaviruses. Only 8 percent of positive samples contained evidence of multiple viral coinfections (one case was positive for five different viruses). The study found that influenza leads to greater changes in gene expression than other viruses, such as coronavirus or rhinovirus. Their findings were also suggestive of a possible link between repeat exposure to pathogens and host responses.

"The repeated emergences of influenza and coronavirus pandemic outbreaks have emphasized the need for a better understanding of host-pathogen interactions in respiratory infections," says study co-first author Marta Galanti, PhD, an associate research scientist in environmental health sciences at Columbia University Mailman School of Public Health.

"Identifying the main biological pathways by which viruses interact with our bodies is key for developing therapeutic tools, such as antivirals or vaccines, as well as for better identifying individuals at risk, both for seasonal respiratory viruses and emerging pandemic threats," says study co-senior author Jeffrey Shaman, PhD, professor of environmental health sciences at Columbia Mailman and Interim Dean of the Columbia Climate School.

An earlier study using data from the same cohort found that reinfections with endemic coronaviruses are not uncommon, even within a year of prior infection. The study found that when reinfection occurred, it was not associated with less severe symptoms. Instead, genetic factors may be a greater determinant of the severity of an infection.