Cold virus replicates better at cooler temperatures

Artist's rendering of a rhinovirus (stock illustration). Credit: © fotoliaxrender / Fotolia

The common cold virus can reproduce itself more efficiently in the cooler temperatures found inside the nose than at core body temperature, according to a new Yale-led study. This finding may confirm the popular yet contested notion that people are more likely to catch a cold in cool-weather conditions.

Researchers have long known that the most frequent cause of the common cold, the rhinovirus, replicates more readily in the slightly cooler environment of the nasal cavity than in the warmer lungs. However, the focus of prior studies has been on how body temperature influenced the virus as opposed to the immune system, said study senior author and Yale professor of immunobiology Akiko Iwasaki.

To investigate the relationship between temperature and immune response, Iwasaki and an interdisciplinary team of Yale researchers spearheaded by Ellen Foxman, a postdoctoral fellow in Iwasaki's lab, examined the cells taken from the airways of mice. They compared the immune response to rhinovirus when cells were incubated at 37 degrees Celsius, or core body temperature, and at the cooler 33 degrees Celsius. "We found that the innate immune response to the rhinovirus is impaired at the lower body temperature compared to the core body temperature," Iwasaki said.

The study also strongly suggested that the varying temperatures influenced the immune response rather than the virus itself. Researchers observed viral replication in airway cells from mice with genetic deficiencies in the immune system sensors that detect virus and in the antiviral response. They found that with these immune deficiencies, the virus was able to replicate at the higher temperature. "That proves it's not just virus intrinsic, but it's the host's response that's the major contributor," Iwasaki explained.

Although the research was conducted on mouse cells, it offers clues that may benefit people, including the roughly 20% of us who harbor rhinovirus in our noses at any given time. "In general, the lower the temperature, it seems the lower the innate immune response to viruses," noted Iwasaki. In other words, the research may give credence to the old wives' tale that people should keep warm, and even cover their noses, to avoid catching colds.

Yale researchers also hope to apply this insight into how temperature affects immune response to other conditions, such as childhood asthma. While the common cold is no more than a nuisance for many people, it can cause severe breathing problems for children with asthma, noted Foxman. Future research may probe the immune response to rhinovirus-induced asthma.

The study was published in the Proceedings of the National Academy of Sciences.

Source: Yale University

Potential biological control for avocado-ravaging disease

University of Florida scientists think they’ve found the first potential biological control strategy against laurel wilt, a disease that threatens Florida’s avocado industry. The redbay ambrosia beetle, see here, bores holes into avocado trees, bringing the disease that causes laurel wilt. Credit: Lyle Buss, UF/IFAS

University of Florida scientists believe they've found what could be the first biological control strategy against laurel wilt, a disease that threatens the state's $54 million-a-year avocado industry.

Red ambrosia beetles bore holes into healthy avocado trees, bringing with them the pathogen that causes laurel wilt. Growers control the beetles that carry and spread laurel wilt by spraying insecticides on the trees, said Daniel Carrillo, an entomology research assistant professor at the Tropical Research and Education Center in Homestead.

But a team of researchers from the Tropical REC and the Indian River Research and Education Center in Fort Pierce have identified a potential biological control to use against redbay ambrosia beetles that could help growers use less insecticide.

First, they exposed beetles to three commercially available fungi, and all of the beetles died. Then they sprayed the fungi on avocado tree trunks, and beetles got infected while boring into the trunk. About 75 percent of those beetles died, said Carrillo, an Institute of Food and Agricultural Sciences faculty member.

Ideally, the fungal treatments could prevent beetles from boring into the trees, eliminating the risk that the pathogen would enter the trees, the study said. But tests showed female beetles bored into the trees and built tunnels regardless of the treatment. Still, researchers say their treatment can prevent the female beetles from laying eggs.

UF/IFAS scientists don't know yet how much less chemical spray will be needed to control the redbay ambrosia beetle. But Carrillo sees this study as the first step toward controlling the beetle in a sustainable way.

"When you want to manage a pest, you want an integrated pest management approach," Carrillo said. "This provides an alternative that we would use in combination with chemical control."

The redbay ambrosia beetle -- native to India, Japan, Myanmar and Taiwan -- was first detected in 2002 in southeast Georgia. It was presumably introduced in wood crates and pallets, and its rapid spread has killed 6,000 avocado trees in Florida, or about 1 percent of the 655,000 commercial trees in Florida. The beetle was first discovered in South Florida in 2010.

Most American-grown avocados come from California, with the rest coming from Florida and Hawaii. The domestic avocado market is worth $429 million, according to Edward Evans, a UF associate professor of food and resource economics, also at the Tropical REC. Florida's avocados are valued at about $23 million, or about 5 percent of the national market.

The redbay ambrosia beetle is not an issue with California avocados, so the new tactic found by Florida scientists wouldn't apply to this pest in the Golden State, said Mark Hoddle, a biological control Extension specialist with the University of California-Riverside. Hoddle studies biological pest control for California avocados. Scientists there are exploring ways to control a different ambrosia beetle, he said, and bug-killing fungi may be useful for the new California pest.

More than 95 percent of Florida's commercial avocados grow in Miami-Dade County, although many Floridians have avocado trees in their yard.
The redbay ambrosia beetle feeds and reproduces on a very wide variety of host plants, native oaks, sycamores, and of course it is very detrimental to avocados.

Source:University of Florida Institute of Food and Agricultural Sciences

This image shows a panda eating in China's Wolong Nature Reserve. Pandas habitat choices center around the ready availability of bamboo -- lots of bamboo. Credit: Sue Nichols, Michigan State University

Walter Dodds, university distinguished professor of biology (pictured), and Allison Veach, doctoral student in biology, are researching grassland streams and the expansion of nearby woody vegetation. They have studied 25 years of data on the Konza Prairie Biological Station and found that increasing fire frequency reduces the rate of woody vegetation expansion. Credit: Image courtesy of Kansas State University

Two Kansas State University biologists are studying streams to prevent tallgrass prairies from turning into shrublands and forests.

By looking at 25 years of data on the Konza Prairie Biological Station, Allison Veach, doctoral student in biology, Muncie, Indiana, and Walter Dodds, university distinguished professor of biology, are researching grassland streams and the expansion of nearby woody vegetation, such as trees and shrubs. They have found that burn intervals may predict the rate of woody vegetation expansion along streams.

Their latest research appears in the peer-reviewed journal PLOS ONE in an article "Fire and Grazing Influences on Rates of Riparian Woody Plant Expansion along Grassland Streams."

Grasslands in North America and across the globe are rapidly disappearing, Veach said, and woody plants are expanding and converting grasslands into forest ecosystems. This change in environment can affect stream hydrology and biogeochemistry, said Dodds, who has studied streams and watersheds on the Konza prairie for more than 20 years.

"This is an important issue regionally, because as trees expand into these grassland areas, people who are using grassland for cattle production have less grass for animals, too," Dodds said.

In their latest research, the biologists studied 25 years of aerial photography on Konza and observed the expansion of trees and shrubs in riparian areas, which include areas within 30 meters of streambeds. The researchers focused on three factors that affect grassland streams: burn intervals; grazers, such as bison; and the historical presence of woody vegetation.

Their analysis revealed an important finding: Burn intervals predicted the rate of woody vegetation expansion. Burning every one to two years slowed the growth of trees and shrubs, Veach said.

"Although we can reduce woody expansion by burning more frequently, we can't prevent it from occurring over time," Veach said. "Woody plant encroachment may not be prevented by fire alone."

The research shows the importance of burning to maintain the tallgrass prairie, Dodds said. While burning can help to slow the expansion of trees and shrubs, additional actions are need to maintain quickly disappearing grassland ecosystems.

"It's clear from this research that if you don't burn at all, these grassland streams basically are going to switch to forests and will not be grassland streams anymore," Dodds said.

Dodds and Veach also found that bison do not significantly affect woody vegetation expansion along streams. Previous Konza research has shown that bison do not spend significant time near stream areas, so they may not influence the growth of nearby trees and shrubs, Veach said.

Woody vegetation also may be expanding in grasslands because of more carbon dioxide in the atmosphere, Dodds said. Grasses and trees compete for carbon dioxide, and grasses are much better at conserving water and efficiently using carbon dioxide. As atmospheric carbon dioxide levels increase, it becomes easier for trees to gather carbon dioxide and gives them a growing advantage over grasses.

"The tallgrass prairie is almost nonexistent on the globe," Veach said. "In order for us to preserve tallgrass prairie, we need to look at woody encroachment because it has been an issue. Things like no fire or differences in climate change may allow woody plant species to competitively take over grasslands."

The biologists plan to continue studying water quality and quantity issues at Konza. Konza is an 8,600-acre tallgrass prairie ecological research site jointly owned by the university and The Nature Conservancy.

Source:  Kansas State University