Immune cells in a malaria-transmitting mosquito sense the invading parasites and deploy an army of tiny messengers in response. These couriers help turn on a mosquito’s defenses, killing off the parasites, a new study suggests.

This more detailed understanding of the mosquito immune system, published January 20 in Science Immunology, might help scientists design new ways to combat malaria, which infects more than 200 million people per year.

“If we understand how the mosquito reduces the parasite to begin with, we hope we can boost these mechanisms to completely eliminate these parasites [in mosquitoes],” says Kristin Michel, an insect immunologist at Kansas State University in Manhattan who wasn’t part of the study.
Different parasites in the Plasmodium genus cause malaria. The disease is spread by certain Anopheles mosquitoes. These mosquitoes have natural defenses against Plasmodium that keep them from being overrun with the parasites when feeding on an infected person’s blood. But malaria transmission still occurs, because some Plasmodium species are particularly skilled at evading mosquito immune systems.

Previous research has shown that hemocytes, the insect equivalent of white blood cells, help mosquitoes fight off pathogens. Carolina Barillas-Mury and her colleagues at the National Institute of Allergy and Infectious Diseases in Rockville, Md., injected Anopheles gambiae mosquitoes — a primary spreader of malaria in sub-Saharan Africa — with a dye that stained their hemocytes. Those mosquitoes snacked on mice infected with a rodent version of malaria. Then the scientists watched the dyed hemocytes’ response.
Hemocytes that detected certain chemical fingerprints left by the parasites began to self-destruct. These dying hemocytes released plumes of tiny vesicles that then activated the mosquito’s defenses against the parasite, the researchers found. The vesicles triggered a protein called TEP1 to take down the parasite. Scientists already knew that TEP1 is an important part of mosquitoes’ immune response against Plasmodium parasites, but it wasn’t clear how the protein was called into action. Without the vesicles, TEP1 didn’t target the parasites.
Barillas-Mury and colleagues don’t know exactly what the microvesicles contain. But she suspects they carry messenger molecules that jump-start TEP1 and other proteins involved in this immune response.

This type of response “is a very powerful defense system because it can make holes in the parasite and kill it,” says Barillas-Mury. “You want it to be active, but in the right place and at the right time.” Plasmodium parasites set up shop in different places in the mosquito gut depending on their life stage. Microvesicles, much smaller than the hemocytes, can more easily move through different gut compartments to trigger a localized immune response right where the parasite is.

The researchers eventually hope to use their understanding of the mosquito immune response to develop new ways to stop malaria. They’re interested in creating a vaccine that prevents mosquitoes that bite an infected person from passing along the parasite. Such a vaccine could be used in combination with others under development that would prevent people infected with the parasite from becoming sick, Barillas-Mury says.

A strange X-ray signal has popped up again in new measurements, raising hopes that it could be a sign of dark matter.

Data from NASA’s Chandra X-ray Observatory reveal an excess of X-rays at a particular energy, creating a bump on a plot, scientists report online at arXiv.org on January 29. The X-ray “line,” as it is known, could reveal the presence of dark matter — an unknown substance that scientists believe constitutes most of the matter in the cosmos.
While the X-ray line has been found previously using several different telescopes, some searches have come up empty (SN: 9/3/16, p. 17). The new observation strengthens the case that the odd feature is real, and eliminates some possible mundane explanations.

“This is a very exciting thing,” says astrophysicist Nico Cappelluti of Yale University, a coauthor of the report. “This is another measurement that sees the line in another direction.”

The new analysis uses data taken when the telescope was observing deep space, rather than pointing at a particular cluster of galaxies. So if the signal indicated dark matter, it would be due to particles in the region surrounding the Milky Way, known as its halo. When hypothetical dark matter particles called sterile neutrinos decay, they could produce X-rays at the energy of the line, about 3,500 electron volts (SN Online: 12/11/15).

Cappelluti and colleagues found that the relative intensity of the line in the halo and the line previously found at the center of the Milky Way was consistent with the expected variation in concentration of dark matter in various parts the galaxy.

Dark matter isn’t the only possible explanation — standard physics might also be able to explain the line. “There’s definitely a lot of debate,” says Shunsaku Horiuchi, an astroparticle physicist at Virginia Tech in Blacksburg who was not involved with the new work. The line “looks like it’s real, but then I don’t know if it’s dark matter or some atomic physics.”
Although there’s still a small chance that the result could be a statistical fluke, the analysis eliminates some other possible explanations. Scientists had proposed that the line could be the result of sulfur ions grabbing an electron from hydrogen atoms in space, but that process couldn’t explain the new data, Cappelluti and colleagues concluded. Likewise, a quirk of the telescope itself couldn’t explain the line, they determined.

“It’s kind of getting other people excited,” says Horiuchi.

After flying more than 10,000 kilometers from South America to the Arctic, male pectoral sandpipers should be ready to rest their weary wings. But once the compact shorebirds arrive at a breeding ground in Barrow, Alaska, each spring, most keep going — an average of about 3,000 extra kilometers.

Scientists thought males, which mate with multiple females, stayed put at specific sites around the Arctic to breed. Instead, in a study of 120 male pectoral sandpipers in Barrow, most flitted all across the region looking for females. One bird flew a whopping 13,045 kilometers more after arriving, researchers report online January 9 in Nature.
“We had no clue that they range over such a wide area,” says study coauthor Bart Kempenaers, a behavioral ecologist at the Max Planck Institute for Ornithology in Seewiesen, Germany. To track the birds, the researchers placed satellite transmitters on 60 males in 2012 and another 60 in 2014.

“It doesn’t seem to be very tough for them to do these flights,” Kempenaers says. Competition for a mate, however, is cutthroat. In Barrow, just a few males sire the majority of offspring each year. The new work shows males visited as many as 24 potential breeding sites over four weeks, perhaps to boost their chances of reproducing.

Some had better stamina than luck. Kempenaers told of one male’s 2,000-kilometer Arctic odyssey: Once the bird reached Barrow, it flew north over the Arctic Ocean before turning around and landing just 300 kilometers from where it started. “There’s nothing northwards. There is only the [North] Pole, no land,” he says.

A new scorecard, devised by analyzing Ebola patients from the most recent outbreak in West Africa, may help doctors quickly decide who needs additional care to survive the virus in future epidemics.

In the latest outbreak, which raged in Guinea, Liberia and Sierra Leone from 2014 to 2016, 28,616 people were infected with virus and 11,310 people died. Doctors might be able to improve the odds of surviving by looking for a few warning signs in people who need to be treated more intensively, Mary-Anne Hartley, of the international charity GOAL Global and the University of Lausanne in Switzerland, and colleagues report February 2 in PLOS Neglected Tropical Diseases.
“It can be very difficult to avoid bias when choosing which Ebola patient should be given extra care when you have limited time and resources,” Hartley says. “Should it be that sweet 7-year-old girl in the corner with a bad cough or the really athletic 45-year-old man who was a bit confused earlier? Our score suggests that it should be the latter.”

Top risk factors for dying from Ebola:
High viral load — Patients with lots of virus in their blood were 12.6 times as likely to die as those with a low viral load.
Age — Children under 5 were 5.4 times as likely to die as were people between 5 and 25; people over age 45 were 11.6 times as likely to die.
Disorientation — The symptom was associated with more than 94 percent of Ebola fatalities and increased the risk of dying by 13.1 times.
Hiccups
Diarrhea
Red, inflamed eyes
Labored breathing or shortness of breath
Muscle pain
Delayed treatment — The risk of dying increased 12 percent each day an infected person put off treatment for the first 10 days after symptoms started.