- Email: [email protected]
HIV evolves into less deadly form
This week
HIV evolves into less deadly form from South Africa, which should mean it takes longer to damage people’s immune systems and result in AIDS (PNAS, doi.org/xhc). “To show it’s adapting so rapidly is very significant,” says José Borghans of the University Medical Center Utrecht in the Netherlands. One reason could be the
HIV seems to be slowly becoming less aggressive in parts of Africa. The change so far has been small – equivalent to people developing AIDS about 2.5 years later than they did at the start of the epidemic – but if it continues, the disease could become substantially less dangerous. A number of factors, including drug treatment, seem to be responsible. It was once thought that pathogens always evolved to become less deadly, so that their hosts have more chance of surviving and spreading the disease. However, we now know that evolutionary pressures can also push in the opposite direction. To track how HIV has been evolving, Philip Goulder of the University of Oxford and his colleagues compared HIV samples from 842 pregnant women in Botswana and South Africa. In Botswana, the epidemic took off in the mid-1980s, compared with the mid-90s in South Africa – so HIV in Botswana has had about a decade longer to evolve. When tested on cells grown in a lab, the virus from Botswana reproduced more slowly than that
Once, twice, three, four times a supernova... SEEING quadruple? For the first time, astronomers have seen an image of a single supernova split into four by a gravitational lens. The splintered stellar explosion may help calibrate distances across the universe. Gravitational lenses are the result of massive celestial objects, like stars, galaxies or even dark matter, bending light as it passes near them. 14 | NewScientist | 6 December 2014
EYE OF SCIENCE/SCIENCE PHOTO LIBRARY
Clare Wilson
growing use of HIV drugs, says Goulder. People with the most virulent form of HIV get sick sooner and start drug treatment. This reduces the level of the virus in their blood and sexual fluids almost to zero, meaning that more aggressive viruses are less likely to be passed on. “It’s a benefit of therapy that nobody thought of,”
–HIV viruses: weaker than before
Sometimes gravitational lenses produce multiple images of a single object behind them. The effect is similar to looking at a candle through the base of a wine glass. If astronomers can find a supernova whose light had been bent in several directions by a gravitational lens, that might tell them how quickly the universe is expanding. Each image takes a different path to telescopes near Earth, depending on how much mass is in the way. The differences in the time it takes each image to reach Earth is proportional to the universe’s expansion rate. It can also give an
estimate of the mass of the lensing galaxy or cluster. Despite decades of searching, no such stellar explosions had turned up. But now, Patrick Kelly at the University of California, Berkeley, and his colleagues say they’ve found one. The supernova appeared in images of the galaxy cluster MACS J1149.6+2223 taken on 10 November by the Hubble Space Telescope. Four
“A supernova whose light has been bent in several directions can tell us the speed of the universe”
he says. “That’s another reason to provide it.” The number of people globally accessing HIV treatment has increased in recent years, rising from 5 million people in 2010 to 13.6 million this June. But there seems to be another factor at play too – the virus is responding to people whose immune systems are naturally better at keeping the infection under control for longer. About 15 per cent of people in southern Africa have genes that mean their immune cells are good at recognising and targeting crucial proteins belonging to the virus. In such people, HIV can only survive by mutating those proteins to evade detection, which makes it slower at reproducing. When those people pass on the virus, it retains that weakness. “The viruses that are left are the ones that are least able to cause disease,” says Goulder. His team found that in Botswana about half the viruses sampled had these mutations, compared with about 40 per cent in South Africa. It is unclear whether similar changes are occurring in Europe and the US, although major changes are less likely where infection rates are lower. n
bright sources surrounding one of the cluster’s giant galaxies all appear to be related to the same object, a smaller galaxy located behind the cluster, meaning they are probably all images of the same star. The object didn’t appear in earlier pictures of the same galaxy cluster, so the team think it is the bright, fatal explosion of a supernova (arxiv.org/abs/1411.6009). “This is a fantastic discovery,” says Robert Quimby at the University of Tokyo in Japan. “The authors make a good case that this is a supernova seen through a gravitational lens.” Liz Kruesi n
HIV evolves into less deadly form from South Africa, which should mean it takes longer to damage people’s immune systems and result in AIDS (PNAS, doi.org/xhc). “To show it’s adapting so rapidly is very significant,” says José Borghans of the University Medical Center Utrecht in the Netherlands. One reason could be the
HIV seems to be slowly becoming less aggressive in parts of Africa. The change so far has been small – equivalent to people developing AIDS about 2.5 years later than they did at the start of the epidemic – but if it continues, the disease could become substantially less dangerous. A number of factors, including drug treatment, seem to be responsible. It was once thought that pathogens always evolved to become less deadly, so that their hosts have more chance of surviving and spreading the disease. However, we now know that evolutionary pressures can also push in the opposite direction. To track how HIV has been evolving, Philip Goulder of the University of Oxford and his colleagues compared HIV samples from 842 pregnant women in Botswana and South Africa. In Botswana, the epidemic took off in the mid-1980s, compared with the mid-90s in South Africa – so HIV in Botswana has had about a decade longer to evolve. When tested on cells grown in a lab, the virus from Botswana reproduced more slowly than that
Once, twice, three, four times a supernova... SEEING quadruple? For the first time, astronomers have seen an image of a single supernova split into four by a gravitational lens. The splintered stellar explosion may help calibrate distances across the universe. Gravitational lenses are the result of massive celestial objects, like stars, galaxies or even dark matter, bending light as it passes near them. 14 | NewScientist | 6 December 2014
EYE OF SCIENCE/SCIENCE PHOTO LIBRARY
Clare Wilson
growing use of HIV drugs, says Goulder. People with the most virulent form of HIV get sick sooner and start drug treatment. This reduces the level of the virus in their blood and sexual fluids almost to zero, meaning that more aggressive viruses are less likely to be passed on. “It’s a benefit of therapy that nobody thought of,”
–HIV viruses: weaker than before
Sometimes gravitational lenses produce multiple images of a single object behind them. The effect is similar to looking at a candle through the base of a wine glass. If astronomers can find a supernova whose light had been bent in several directions by a gravitational lens, that might tell them how quickly the universe is expanding. Each image takes a different path to telescopes near Earth, depending on how much mass is in the way. The differences in the time it takes each image to reach Earth is proportional to the universe’s expansion rate. It can also give an
estimate of the mass of the lensing galaxy or cluster. Despite decades of searching, no such stellar explosions had turned up. But now, Patrick Kelly at the University of California, Berkeley, and his colleagues say they’ve found one. The supernova appeared in images of the galaxy cluster MACS J1149.6+2223 taken on 10 November by the Hubble Space Telescope. Four
“A supernova whose light has been bent in several directions can tell us the speed of the universe”
he says. “That’s another reason to provide it.” The number of people globally accessing HIV treatment has increased in recent years, rising from 5 million people in 2010 to 13.6 million this June. But there seems to be another factor at play too – the virus is responding to people whose immune systems are naturally better at keeping the infection under control for longer. About 15 per cent of people in southern Africa have genes that mean their immune cells are good at recognising and targeting crucial proteins belonging to the virus. In such people, HIV can only survive by mutating those proteins to evade detection, which makes it slower at reproducing. When those people pass on the virus, it retains that weakness. “The viruses that are left are the ones that are least able to cause disease,” says Goulder. His team found that in Botswana about half the viruses sampled had these mutations, compared with about 40 per cent in South Africa. It is unclear whether similar changes are occurring in Europe and the US, although major changes are less likely where infection rates are lower. n
bright sources surrounding one of the cluster’s giant galaxies all appear to be related to the same object, a smaller galaxy located behind the cluster, meaning they are probably all images of the same star. The object didn’t appear in earlier pictures of the same galaxy cluster, so the team think it is the bright, fatal explosion of a supernova (arxiv.org/abs/1411.6009). “This is a fantastic discovery,” says Robert Quimby at the University of Tokyo in Japan. “The authors make a good case that this is a supernova seen through a gravitational lens.” Liz Kruesi n