Impairment of human polymorphonuclear leucocyte function by influenza virus

Area of Science:

• Immunology
• Virology
• Microbiology

Background:

• Bacterial pneumonia frequently complicates influenza infections in humans.
• The underlying mechanisms for this increased susceptibility to secondary bacterial infections remain incompletely understood.

Purpose of the Study:

• To investigate the in vitro effects of influenza virus on human polymorphonuclear leucocyte (PMN) function.
• To elucidate the role of PMN dysfunction in the pathogenesis of influenza-associated bacterial pneumonia.

Main Methods:

• Human polymorphonuclear leucocytes were incubated with influenza viruses in vitro.
• Chemotaxis and phagocytosis of Staphylococcus bacteria by PMNs were assessed.
• Hexose-monophosphate-shunt activation in PMNs was measured.

Main Results:

• Influenza virus incubation significantly inhibited the chemotaxis of human PMNs.
• The ability of PMNs to phagocytose Staphylococcus bacteria was also reduced.
• Activation of the hexose-monophosphate-shunt pathway in PMNs remained unaffected.
• These inhibitory effects demonstrated specificity towards the influenza virus.

Conclusions:

• Influenza viruses directly impair key functions of polymorphonuclear leucocytes, including chemotaxis and phagocytosis.
• This virus-induced PMN dysfunction provides a potential explanation for the frequent occurrence of bacterial pneumonia following influenza.
• Targeting PMN function during influenza infection could be a therapeutic strategy to prevent secondary bacterial complications.