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| Live from the Labs cnrs I international w 10 magazine Astrophysics For the first time, scientists were able to measure the intensity of the extragalactic background light that fills the universe from UV to near infrared. Measuring “Cosmic Big Bang Milky Way Today First stars of the galaxy Solar System Microbicide Gel Prevents HIV Infection BY Arby Gh aribi an w In the battle against AIDS, an international team led by Loïc Martin from the iBiTec-S laboratory1 has made new use of an age-old strategy: deception. The researchers relied on “miniprotein engineering” to develop a small mimetic peptide that traps HIV and inhibits its spread. Formulated into a microbicide gel, it helped prevent infection in five out of six macaques exposed to the virus.2 For years, Martin and his team have been creating these small peptides called miniCD4s, which mimic the molecular structure of the neural receptor CD4. If CD4 is known to bind with the virus and give it access to target cells, miniCD4s, on the other hand, bind with it but also trap it, blocking its propagation. “A promising new miniCD4 is M48U1,” explains Martin. “We attached the binding site of a large protein onto a small scaffold protein. Without this miniaturization process, HIV-miniCD4 binding would provoke the same reaction as HIV-CD4 binding, that is an autoimmune response compromising the immune system’s ability to combat infections.” The antiviral activity of M48U1 had already been demonstrated at the molecular level, so recent tests focused on in vitro assays on vaginal and colorectal tissue from human patients. The peptide’s propensity to neutralize HIV proved so strong that researchers began testing it on non-human primates. For the test, 12 female macaques were exposed to high doses of HIV. One hour before exposure, all received a vaginal gel treatment, half with a placebo and the other half with the gel formulated Biology Saclay - - Day post infection Viral RNA Copies/mL 7 miniCD Group 6 5 4 ³ ² BD As these streams of high-energy gamma-ray photons travel through the universe, they meet the low-energy photons that make up EBL. The fog “absorbs” the gamma rays, thus reducing the intensity of the streams: the greater the loss of gamma rays, the greater the density of EBL. Until now, this absorption rate was constrained by comparing levels of gamma rays detected on Earth with theoretical models of the make-up of the rays when released by their blazar. “We realized, however, that absorption creates inflection points in the gamma-ray spectrum and that their positions depend on the amount of cosmic fog they go through,” explains Biteau. These specific and unambiguous signatures allowed the researchers to “measure the absorption of the ‘cosmic fog’ with ground-based gamma-ray telescopes for the first time.” BY Tom Rid gway Since the Big Bang 14 billion years ago, the universe has been filling with photons. Known as diffuse extragalactic background light, or EBL, this “fog of photons is made up of all the light emitted by stars and galaxies since the birth of the universe,” explains Jonathan Biteau from the LLR,1 who led the study. Unfortunately, the light emitted by the Solar System and our own galaxy has always made it difficult to evaluate this luminous fossil record of the universe. So Biteau and his collaborators decided to use an indirect method that exploits streams of gamma rays emitted by particular quasars—blazars—around 2 billion light years away.2 This was achieved using the High Energy Stereoscopic System (HESS) telescopes located in Namibia. q HESS and Fermi-LAT data were used to analyze gamma-ray absorption levels at various stages of the formation of the universe. q When treated with miniCD4 prior to HIV exposure, 5 out of 6 female macaques (different color lines) were protected against the infection. © d 'après L. MARTIN © H.E.S.S. Coll abor ation


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