Evidence for IFNα-induced, SAMHD1-independent inhibitors of early HIV-1 infection

Retrovirology. 2013 Feb 25:10:23. doi: 10.1186/1742-4690-10-23.

Abstract

Background: Type I interferon (IFN) treatment of some cells, including dendritic cells, macrophages and monocytic THP-1 cells, restricts HIV-1 infection and prevents viral cDNA accumulation. Sterile alpha motif and HD domain protein 1 (SAMHD1), a dGTP-regulated deoxynucleotide triphosphohydrolase, reduces HIV-1 infectivity in myeloid cells, likely by limiting dNTPs available for reverse transcription, and has been described as IFNα-inducible. Myeloid cell infection by HIV-1 is enhanced by HIV-2/SIVSM Vpx, which promotes SAMHD1 degradation, or by exogenous deoxyribonucleoside (dN) addition.

Findings: SAMHD1 expression was not substantially influenced by IFNα treatment of monocyte-derived macrophages or THP-1 cells. The contributions of SAMHD1 to the inhibition of HIV-1 infectivity by IFNα were assessed through the provision of Vpx, exogenous dN addition, or via RNAi-mediated SAMHD1 knock-down. Both Vpx and dN efficiently restored infection in IFNα-treated macrophages, albeit not to the levels seen with these treatments in the absence of IFNα. Similarly using differentiated THP-1 cells, the addition of Vpx or dNs, or SAMHD1 knock-down, also stimulated infection, but failing to match the levels observed without IFNα. Neither Vpx addition nor SAMHD1 knock-down reversed the IFNα-induced blocks to HIV-1 infection seen in dividing U87-MG or THP-1 cells. Therefore, altered SAMHD1 expression or function cannot account for the IFNα-induced restriction to HIV-1 infection seen in many cells and cell lines.

Conclusion: IFNα establishes an anti-HIV-1 phenotype in many cell types, and appears to accomplish this without potentiating SAMHD1 function. We conclude that additional IFNα-induced suppressors of the early stages of HIV-1 infection await identification.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Gene Knockdown Techniques
  • HIV-1 / immunology*
  • Humans
  • Interferon-alpha / immunology*
  • Macrophages / immunology*
  • Macrophages / virology*
  • Monomeric GTP-Binding Proteins / genetics
  • Monomeric GTP-Binding Proteins / metabolism*
  • Nucleotides / metabolism
  • SAM Domain and HD Domain-Containing Protein 1
  • Viral Regulatory and Accessory Proteins / metabolism

Substances

  • Interferon-alpha
  • Nucleotides
  • VPX protein, Human immunodeficiency virus 2
  • Viral Regulatory and Accessory Proteins
  • SAM Domain and HD Domain-Containing Protein 1
  • SAMHD1 protein, human
  • Monomeric GTP-Binding Proteins