Milder Cases of COVID-19 Linked to IgA Antibodies

Dartmouth researchers shed light on broad range of disease severity

COVID-19 patients with milder cases exhibit an increased presence of Immunoglobulin A (IgA) antibodies in their mucosa, according to Dartmouth researchers. The finding represents the first antibody correlate to milder disease severity, and suggests the kind of immune response that could provide protection from infection and reduced likelihood of transmission.

“Everyone is wondering how long antibodies will be around after a positive test and how long people are protected,” said co-first author Savannah Butler, a PhD student in Dartmouth’s Molecular & Cellular Biology (MCB) program. “So, we measured diverse antibody features and functions, allowing us to see specific characteristics of those antibodies present in patients with both severe and mild disease.”

The researchers collected blood, nasal wash, and stool samples from 20 locals one month after they tested positive for COVID-19, and examined the COV-specific antibody response across the disease and six other endemic human coronaviruses. Their results have been detailed in a paper, “Features and Functions of Systemic and Mucosal Humoral Immunity Among SARS-CoV-2 Convalescent Individuals,” available on medRxiv.

PhD candidates and co-first authors Andrew Crowley, Harini Natarajan, and Savannah Butler in the Ackerman Lab at Thayer.

The study also suggested an anti-correlation between IgA and Immunoglobulin G (IgG), meaning that COVID-19 positive patients seemed to exhibit either a strong IgA response or IgG response, but not both. That divergence could in part explain the broad range of severity of the disease.

Dartmouth researchers are already working on a second study with a cohort of 100 patients and will test for antibodies three and five months after a positive COVID-19 test. Testing for antibodies multiple times will enable the researchers to understand how the antibodies look long-term and how long protection may last.

“We are still looking at similarities and differences between COVID-19 positive patients who were hospitalized and those who were able to recover at home to determine what kind of immune response might lead to a good outcome,” said co-first author Harini Natarajan, also a PhD student in Dartmouth’s MCB program.

Dartmouth PhD candidate Andrew Crowley, a student in the MCB program, also served as co-first author on the study. Dartmouth engineering professor Margie Ackerman and Peter Wright, a professor of pediatrics at Dartmouth, served as corresponding authors.

Preprint servers, such as medRxiv, contain unpublished research that has not yet been subjected to rigorous peer review by a scientific journal. Researchers often post to these servers when they feel their findings are of urgent need to the research community, but research should not be relied upon to guide clinical practice or health-related behavior.