Infection with influenza virus may not always weaken white blood cells known as neutrophils, a phenomenon that could result in more secondary bacterial infections. In fact, some strains of influenza virus can enhance the neutrophil response, according to a new study published Jan. 3 in mSphere by a collaboration of NIAID bacterial immunology and virology groups.
One group of researchers specializes in studying neutrophils, white blood cells that make up the body’s primary defense against potentially harmful bacteria, such as Staphylococcus aureus – a leading cause of secondary bacterial infections. Interactions between bacteria and neutrophils are well documented in science journals, but less is known about how neutrophils interact with viruses.
Two common – but conflicting – research observations spurred the study: People with influenza A virus lung infections seemingly have more secondary bacterial infections; and during influenza A virus infection, people’s lungs can be enriched with neutrophils.
In the study, scientists exposed human neutrophils to seasonal and pandemic strains of H1N1 influenza virus in a laboratory model designed to mimic host-pathogen interaction during infection. Surprisingly, exposure to seasonal (but not pandemic) H1N1 influenza enhanced neutrophil functions, including the ability to kill S. aureus. The researchers also identified changes in neutrophil gene expression in response to both virus types. They hope that by analyzing changes in gene expression, they can determine how seasonal and pandemic influenza A viruses alter the function of neutrophils.
Reference: N Malachowa, et al. Differential ability of pandemic and seasonal H1N1 influenza A viruses to alter the function of human neutrophils. mSphere DOI: 10.1128/mSphereDirect.00567-17 (2018).