During infections, the immune system recognizes microbial pathogens and activates an immediate defence response to neutralize viruses and bacteria. The exact biochemical mechanisms allowing the immune cells to sense the immunodeficiency virus, HIV, however, remain unknown.

Daxing Gao and colleagues, University of Texas Southwestern Medical Center, USA, shed light on this issue. The researchers demonstrated that, during HIV infections, the viral DNA triggers the immune response by binding and activating cyclic GMP–AMP synthase (cGAS), an enzyme that converts ATP and GTP into cyclic guanosine monophosphate–adenosine monophosphate (cGAMP). In turn, this cyclic dinucleotide stimulates the production of β interferons, glycoproteins that interfere with the viral replication.

cGAMP could be, thus, used to augment the effects of vaccines aimed at stimulating the immune system against HIV infections.

• Cyclic GMP–AMP Synthase Is an Innate Immune Sensor of HIV and Other Retroviruses,
  D. Gao, J. Wu, Y.-T. Wu, F. Du, C. Aroh, N. Yan, L. Sun, Z. J. Chen,
  Science 2013.
  DOI: 10.1126/science.1240933