Influenza Virus Infects and Depletes Activated Adaptive Immune Responders

Area of Science:

• Immunology
• Virology
• Infectious Diseases

Background:

• Influenza infections cause significant global morbidity and mortality, with secondary infections contributing heavily.
• Increased incidence of other respiratory infections and vaccine failures occur during influenza season, even in vaccinated individuals.

Purpose of the Study:

• Investigate mechanisms behind influenza vaccine failures and increased secondary infections during flu season.
• Elucidate how influenza virus impacts adaptive immune responses to other pathogens.

Main Methods:

• Utilized peripheral blood mononuclear cells (PBMCs) from vaccinated individuals to assess immune responses.
• Examined antigen-specific responses to influenza, measles, and varicella.
• Confirmed and extended human observations in a mouse model.

Main Results:

• Influenza virus infection suppresses adaptive immune responses to influenza and other pathogens like Adenovirus and Streptococcus pneumoniae.
• Influenza virus preferentially infects and kills activated lymphocytes expressing sialic acid receptors.

Conclusions:

• Proposes a novel mechanism where influenza virus-induced lymphocyte depletion explains secondary infections and vaccine failures.
• Highlights the broad impact of influenza on the immune system beyond direct viral effects.