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Bat and pig IFN-induced transmembrane protein 3 restrict cell entry by influenza virus and lyssaviruses

Camilla T O Benfield1, Sarah E Smith2, Edward Wright3

  • 1Department of Pathology and Pathogen Biology, The Royal Veterinary College, Hatfield, UK.

The Journal of General Virology
|January 24, 2015
PubMed

Insights

Interferon-induced transmembrane protein 3 (IFITM3) acts as a broad-spectrum antiviral in pigs and bats. This protein restricts viral entry, offering protection against emerging viruses in these key mammalian reservoirs.

Area of Science:

  • Virology
  • Immunology
  • Mammalian Genetics

Background:

  • Interferon-induced transmembrane protein 3 (IFITM3) is a known antiviral restriction factor in humans and mice, inhibiting viruses entering cells via acidic endosomes.
  • Many viruses sensitive to IFITM3 are zoonotic, raising questions about IFITM3's antiviral role in other mammalian species.
  • Pigs and bats are significant reservoirs for emerging viruses, making their antiviral mechanisms crucial to understand.

Purpose of the Study:

  • To investigate the function of IFITM3 orthologues in pigs (Sus scrofa domesticus) and microbats (Myotis myotis) as antiviral restriction factors.
  • To determine if conserved functional domains in IFITM3 are present in these species.
  • To assess the endogenous antiviral activity of IFITM3 in pig and bat cells.

Main Methods:

  • Identification of IFITM3 orthologues in microbat and pig using rapid amplification of cDNA ends.
  • Ectopic expression of pig and microbat IFITM3 in cell lines to assess co-localization with endosomal markers (transferrin, CD63).
  • Functional assays using influenza hemagglutinin and lyssavirus glycoproteins to test viral entry restriction.
  • Assessment of viral replication (influenza virus yield, nucleoprotein expression) and endogenous IFITM3 function via small interfering RNA (siRNA) knockdown in primary cells.

Main Results:

  • Conserved amino acid residues critical for IFITM3 function were identified in pig and microbat orthologues.
  • Ectopically expressed pig and microbat IFITM3 localized to early and late endosomes.
  • Both pig and microbat IFITM3 demonstrated broad-spectrum restriction of viral entry mediated by influenza hemagglutinin subtypes and lyssavirus glycoproteins.
  • Expression of pig or microbat IFITM3 reduced influenza virus replication in cell culture.
  • Knockdown of endogenous IFITM3 in pig and microbat cells enhanced influenza virus replication, confirming its functional role.

Conclusions:

  • IFITM3 functions as a potent, broad-spectrum antiviral effector in pigs and bats.
  • These findings highlight the conserved antiviral role of IFITM3 across diverse mammalian species, including important zoonotic reservoirs.
  • Understanding IFITM3's function in bats and pigs provides insights into host-pathogen interactions relevant to emerging infectious diseases.

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