Immunosuppression during influenza virus infection

Area of Science:

• Immunology
• Virology
• Infectious Diseases

Background:

• Influenza viruses are significant human pathogens.
• Understanding the immunomodulatory effects of influenza infection is crucial for vaccine development and disease management.

Purpose of the Study:

• To evaluate the impact of live attenuated influenza vaccine (LAIV) and virulent influenza virus challenge on cell-mediated immunity.
• To assess the effects on delayed hypersensitivity skin tests and in vitro lymphocyte responses.

Main Methods:

• Volunteers received either LAIV or placebo, followed by challenge with virulent influenza virus.
• Skin tests were performed using purified protein derivative (PPD), candida, mumps, and trichophytin antigens.
• Lymphocyte proliferation was measured by [(3)H]thymidine uptake in response to phytohemagglutinin (PHA).

Main Results:

• A significant diminution in skin test responses was observed in 4 out of 8 volunteers after LAIV and 8 out of 13 after virulent influenza challenge.
• Twelve out of 21 infected volunteers showed suppressed PHA-induced lymphocyte proliferation.
• No suppression of T-cell or B-cell function was noted in placebo recipients or in infected individuals without viral replication.

Conclusions:

• Influenza virus infection, including LAIV, can transiently suppress T-cell mediated immunity, as evidenced by reduced skin test reactivity and lymphocyte proliferation.
• B-cell function appears to be preserved during influenza infection.
• These findings highlight the immunomodulatory capacity of influenza viruses and have implications for understanding host-pathogen interactions.