RSV vs. COVID-19: Why Infants Get Sicker with RSV – and What It Means for Treatment
Young infants hospitalized with respiratory syncytial virus (RSV) often experience more severe illness than those with COVID-19. New research published in Science Translational Medicine from St. Jude Children’s Research Hospital and The Jackson Laboratory (JAX) reveals that these differing outcomes aren’t simply due to the viruses themselves, but to fundamentally different immune responses in infants.
The Puzzle of RSV Severity
During the COVID-19 pandemic, doctors noticed a surprising trend: infants admitted to hospitals with RSV infections frequently exhibited more severe symptoms than those hospitalized with SARS-CoV-2, despite both being respiratory RNA viruses. This observation prompted researchers to investigate the underlying immunological mechanisms driving these disparities.
A Single-Cell Seem at Immune Responses
The study compared the immune responses of infants hospitalized with either RSV or SARS-CoV-2 to those of healthy infants, analyzing blood samples at a single-cell level. Researchers measured proteins, genes, and epigenetic signatures to pinpoint the specific immune cells and signals responsible for the observed differences.
RSV Triggers a Surprisingly Weak Response
The findings revealed that severe RSV infection in infants is linked to unexpectedly low levels of systemic inflammation and a poorly coordinated early immune response, particularly from natural killer (NK) cells. This contrasts sharply with the hyperinflammatory immune response seen in infants infected with SARS-CoV-2.
“We showed, for the first time, that two similar respiratory viruses, RSV and SARS-CoV-2, cause very different types of immune dysregulation in young infants,” explained Dr. Octavio Ramilo, chair of the St. Jude Department of Infectious Diseases.
Epigenetic Reprogramming by RSV
Further analysis uncovered that RSV appears to “reprogram” parts of the infant immune system at the epigenetic level – altering molecular switches that control gene expression. This suggests RSV doesn’t just suppress the immune system; it actively changes how it functions.
“These changes may support explain why RSV can lead to more severe disease and possibly influence how the immune system responds in the future,” said Dr. Duygu Ucar, Professor at JAX.
Implications for Treatment: Rethinking Steroids
The research has direct implications for clinical practice. Unlike SARS-CoV-2, which often causes significant immune dysregulation and may benefit from anti-inflammatory treatments like steroids, RSV already suppresses the immune system. Giving steroids to infants with RSV may therefore worsen their condition by further impairing the natural killer cell response.
“One very practical implication of our work is that we should not routinely give steroids to infants with RSV,” stated Dr. Asunción Mejías.
Future Directions: Understanding Infant Immunity
RSV remains a leading cause of infant hospitalizations and the second leading cause of infant mortality worldwide. This study provides a crucial blueprint for understanding infant immunity in general, potentially leading to improved prevention and treatment strategies for a range of infectious diseases.
“Globally, five million children die before the age of 5, half occurring in the first months of life due to infection, before vaccines are given,” Dr. Ramilo noted. “With the tools we have developed, we can start to uncover what’s happening in that early immunological window to begin improving those odds.”
Frequently Asked Questions
- Why are infants more severely affected by RSV than adults? The study suggests infants have a different immune response to RSV, characterized by low inflammation and a poorly coordinated response from natural killer cells.
- Should infants with RSV receive steroids? The research indicates steroids may be harmful to infants with RSV, as the virus already suppresses the immune system.
- What is epigenetic reprogramming? It refers to changes in gene expression caused by alterations to molecular switches that control which genes are turned on or off.
- What is the role of natural killer cells in fighting RSV? The study found that severe RSV is linked to a poorly coordinated response from these cells, suggesting they are crucial for effective immune defense.
Did you know? RSV is the most common cause of bronchiolitis and pneumonia in infants and young children in the United States.
Pro Tip: Protecting infants from RSV involves practicing good hygiene, such as frequent handwashing, and limiting exposure to sick individuals.
Learn more about respiratory viruses and infant health at St. Jude Children’s Research Hospital and The Jackson Laboratory.
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