Blogs / 80beats

To combat the persistent scourge of dengue fever, researchers have infected the virus-carrying mosquitoes with a bacterium that kills them before they’re old enough to transmit the virus to humans. Researchers say this “biopesticide” technique could cheaply and quickly reduce deaths due to dengue fever in the tropics, as the bacterium could rapidly spread through mosquito populations. Traditional [malaria-oriented] methods for controlling the spread of mosquito-borne disease, such as using bed nets and draining wetlands, are ineffective for the Aedes aegytpi mosquitoes that spread dengue fever virus because they bite during the day and thrive in urban areas [Nature News].

While the new process has only been tested in the lab thus far, researchers are very optimistic about the possibility of whittling away at the 20,000 deaths caused each year by the disease, and say it’s conceivable that transmission of the virus could be reduced to nearly zero. “We’re not trying to eliminate the population, but to let a bacterial symbiont in, and then shift the population,” said University of Queensland bacterial geneticist Scott O’Neill. “There will still be mosquitoes around, but only young ones. It’s a biological control” [Wired News].

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Flu season is taking a toll on chicken farms across Asia, where new bird flu outbreaks are cropping up from China to India, leading to massive poultry slaughters. Health officials say the chickens are infected with the deadly bird flu strain known as H5N1, but thus far there have been only a few cases of human infection. Two human cases have been reported in Indonesia, one in Cambodia, and in Egypt a 16-year-old girl died of the virus. Yi Guan, a Hong Kong microbiology professor, says the recent spate of cases across the region may not be completely isolated and would likely get worse as winter sets in, when the risks of influenza tend to peak [The Wall Street Journal].

In China, more than 370,000 chickens were culled after an outbreak was announced in the eastern province of Jiangsu. The usual precautions have been imposed: birds have been slaughtered in the surrounding area, farms quarantined and disinfected, and the transport of fowl banned. But no information has been released about the scale of the outbreak - how many birds were found to be carrying the H5N1 strain of the virus and how many of them died [BBC News]. Chinese authorities say migrating birds probably brought the virus to local farms.

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In a remarkable announcement, German researchers have declared that they “functionally cured” a patient of AIDS, eradicating all traces of the virus from his body. The feat was accomplished with a bone marrow transplant from a donor who had a genetic resistance to the virus, and researchers say that 20 months later they can find no trace of the virus in the patient’s blood, bone marrow, or organ tissue.

But the accomplishment shouldn’t be taken as a sign that a cure for the 33 million people living with AIDS is around the corner, researchers are hasty to add. Professor Rodolf Tauber from the [German] clinic said: “This is an interesting case for research. But to promise to millions of people infected with HIV that there is hope of a cure would not be right” [BBC News]. Reasons for this caution include the small number of potential donors with the HIV-resistant mutation, and the difficulty and expense of bone marrow transplants.

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Three researchers who discovered viruses that cause serious diseases have been awarded the Nobel Prize in medicine, the Nobel Foundation announced today. The prize was awarded jointly to France’s Francoise Barre-Sinoussi and Luc Montagnier, who worked together to identify the HIV virus that causes AIDS, and also to the German scientist Harald zur Hausen who discovered the human papilloma viruses that cause cervical cancer.

Barre-Sinoussi, who is the eighth woman to win the medicine prize since the first Nobel Prizes were handed out in 1901, worked with Montagnier to discover the HIV virus. Shortly after reports in the early 1980s of a new immunodeficiency syndrome, researchers all over the world raced to find the cause. The two [researchers] cultured cells from lymph nodes of patients. They first detected the enzyme reverse transcriptase, which meant that a retrovirus was active. Further searching turned up retroviral particles, which could kill white blood cells and which also reacted with antibodies from infected patients [Scientific American].

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New genetic evidence shows that people were first infected with the HIV virus around the beginning of the 20th century, and researchers say the virus was able to take hold in human populations because of the growth of colonial cities in sub-Saharan Africa at that time. The evidence comes from a newly discovered tissue sample taken in 1960 from an HIV-infected woman who lived in Leopoldville–the city now known as Kinshasa, the capital of the Democratic Republic of the Congo.

Lead researcher Michael Worobey says that the virus may have crossed over from chimpanzees to rural humans repeatedly in the timeframe he identified, from 1884 to 1924; however, it didn’t take off in human populations until people in sub-Saharan Africa crowded together in cities. When the team looked at the region’s political history, they were struck by parallels between HIV’s spread and population expansion. The first major cities - Kinshasa, Douala, Brazzaville, Yaounde, Bangui - were founded by European colonialists in the late 1800s. Their populations started booming around 1910. “I was stunned by the timing,” says Worobey. “I would bet that cities, and the high-risk [sexual] behaviours found in them, are necessary to allow one of these sporadic viral jumps to get a toehold in the human population” [New Scientist].

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A single-celled phytoplankton that forms enormous blooms in the ocean and plays a vital role in regulating the carbon cycle has an unusual defense against a virus: When the virus appears, the microbe switches into a different life phase, thereby avoiding an attack from the virus. Researchers call the clever defense a “Cheshire Cat escape strategy” after the cat in Alice in Wonderland that occasionally vanished.

“In this paper, we show how a species can escape from [environmental] pressure by switching to a life-cycle phase or form that’s not recognizable by a predator,” said Miguel Frada, a marine microbiologist [The Scientist]. The microbe, named Emiliania huxleyi, is so abundant in the ocean that its massive blooms can form turquoise patches visible from space, yet these blooms are often cut off abruptly in a boom-and-bust cycle. The new study suggests that the busts are caused when a virus causes the microbes to switch forms.

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Researchers have found a way to create stem cells from adult liver cells without triggering DNA changes that have caused mutations and tumors in previous studies. Though demonstrated only in mice so far, the result marks another key achievement in the fledgling science of cellular reprogramming. The hope is to create human, embryonic-like stem cells — which can be turned into all the other tissue types of the body — without using eggs or destroying embryos. That freshly derived tissue could then be transplanted into patients to treat various diseases [The Wall Street Journal].

A method of using adult cells to create stem cells was debuted by Japanese researchers in 2006. By using viruses to insert key developmental genes, researchers coaxed human skin cells into an embryonic state, capable of growing into almost any other type of tissue…. But there was a catch: Viruses used to reset the cells tended to fuse with their DNA, leading to unpredictable mutations and cancer. The cells were promising in principle, but couldn’t be used medically [Wired News]. In the new breakthrough, researchers used a different kind of virus to introduce the genes, and found that it didn’t leave behind any damaging genetic code.

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