Lactoferrin and surfactant protein A exhibit distinct binding specificity to F protein and differently modulate

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Hitomi Sano1, Kazushige Nagai, Hiroyuki Tsutsumi

  • 1Department of Biochemistry, Sapporo Medical University School of Medicine, Sapporo, Japan. sanohito@sapmed.ac.jp

European Journal of Immunology
|September 30, 2003
PubMed

Insights

Surfactant protein A (SP-A) enhances respiratory syncytial virus (RSV) infection, while lactoferrin (LF) inhibits it. These opposing effects stem from distinct binding interactions with the RSV F protein, impacting innate immunity.

Area of Science:

  • Immunology
  • Virology
  • Biochemistry

Background:

  • Surfactant protein A (SP-A) and lactoferrin (LF) are key components of the innate immune system in respiratory mucous membranes.
  • Respiratory Syncytial Virus (RSV) is a significant pathogen affecting the respiratory system.

Purpose of the Study:

  • To investigate the distinct roles of SP-A and LF in modulating RSV infection.
  • To elucidate the molecular mechanisms underlying their opposing effects on RSV infectivity and immune responses.

Main Methods:

  • HEp-2 cells were used to assess RSV-induced IL-8 secretion.
  • Viral titers and FITC-labeled RSV uptake were measured to determine RSV infectivity.
  • Interactions between SP-A, LF, and the RSV F protein were analyzed, including binding to different subunits and effects on deglycosylated F protein.
  • Hemolyzing fusion activity of the F protein was evaluated.

Main Results:

  • SP-A significantly up-regulated RSV-induced IL-8 secretion and increased RSV infectivity.
  • LF markedly down-regulated IL-8 secretion and decreased RSV infectivity.
  • Both SP-A and LF bind to the RSV F protein, but through different mechanisms.
  • LF interacts with the F(1) subunit, while SP-A binds to the glycosylated F(2) subunit, initiating fusion activity.

Conclusions:

  • SP-A and LF exert opposing effects on RSV infection and immune responses.
  • These differential effects are mediated by specific binding interactions with distinct regions of the RSV F protein.
  • The findings provide insights into the complex interplay between host immune factors and viral pathogenesis.

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