Crippling viral infections 'cause asthma'

By James GallagherHealth and science repor

They say their findings, published in the journal Nature Medicine, will help develop ways of preventing asthma.Viral infections in newborns "cripple" part of the immune system and increase the risk of asthma later in life, US researchers studying mice have said.

They showed infections by respiratory syncytial virus (RSV) stripped immune cells of their ability to calm down inflammation in the lung's airways.

The charity Asthma UK said the study had "really exciting" potential.

When something irritates the airways of a patient with asthma, the airways become tightened, inflamed and produce too much sticky mucus. All of this can make breathing difficult.

Previous studies have shown a link between repeated lung infections with RSV and developing asthma later in life.

One Swedish study showed showed 39% of infants taken to hospital with RSV had asthma when they were 18. However, only 9% of infants who were not ill developed asthma.

How the virus might be able to do this was, however, unknown. Now a team of researchers at the University of Pittsburgh School of Medicine believe they have an explanation.

Their experiments on mice showed the virus impaired the ability of a specific part of the immune system, called regulatory T cells, to calm inflammation.

Inflammation is an important part of dealing with an infection. However, for asthma patients, chemicals in air which come from ordinary things like dust mites, pets and mould can trigger an inappropriate inflammatory response.

Infection with RSV led to a "complete loss of suppressive function" of the regulatory T cells, after which the mice developed asthma-like symptoms," researchers Prof Anuradha Ray and Prof Prabir Ray told the BBC.

Early window

They said there might be a window in early life when the cells were vulnerable to being "crippled".

They think the finding could help scientists devise treatments which prevent some people developing asthma.

"We feel that both prophylactic and therapeutic approaches can be developed.

"This is especially desirable in infants who have a strong family history of asthma."

Malayka Rahman, from Asthma UK, said: "This research provides vital information on how viruses interact with our immune cells and why this might lead to an increased risk of asthma.

"What's really exciting is the potential of these findings to translate into new treatments for asthma in the future."

Ape hunters pick up new viruses

Ape hunters pick up new viruses

Chimpanzees carry viruses which can jump to humans
Two new viruses from the same family as HIV have been discovered in central Africans who hunt nonhuman primates.
Researchers say their work proves it is not unusual for potentially dangerous viruses to jump from primates to man.

They say it is important to monitor disease in bushmeat hunters closely, as any virus they contract from animals may spread to the community at large.

The study, led by the US Johns Hopkins University, is published in Proceedings of the National Academy of Sciences.

Far from being rare events, retroviruses are actively crossing into human populations

Dr Nathan Wolfe
The new viruses identified in the latest study come from a group known as the retroviruses, which are known to cause serious illnesses in humans.

They have been named Human T-lymphotropic Virus types 3 and 4 (HTLV-3 and HTLV-4).

Humans have previously been infected by HTLV-1 and HTLV-2. In most cases, infection does not produce symptoms, but it can trigger neurological problems, and even leukaemia.

Lead researcher Dr Nathan Wolfe said: "The emergence of HIV from primate origins has cost millions of lives.

"The discoveries of HTLV-3 and HTLV-4 show that, far from being rare events, retroviruses are actively crossing into human populations."

Blood samples

The research team collected and examined blood samples from more than 900 people living throughout Cameroon.

All the individuals studied reported some exposure to blood and body fluids of nonhuman primates, contact mostly due to hunting and butchering of bushmeat, and in some cases to keeping primates as pets.

Analysis of the blood samples showed that various simian (ape) viruses had infected the participants.

The two previously unknown viruses were found in two bushmeat hunters.

HTLV-3 is similar to a simian virus called STLV-3, and was most likely contracted through direct contact with a primate during hunting.

HTLV-4 does not have a known primate counterpart, making its origin less clear. The researchers believe it could have arisen through cross-species transmission from an animal carrying an unknown form of STLV.

The same team discovered another primate retrovirus - the simian foamy virus (SFV) - in bushmeat hunters last year.

Threat unclear

At this stage it is unclear whether either of the two newly discovered viruses or SFV are harmful to humans, or can be transferred from person to person.

However, the researchers say their work clearly shows that hunting provides the opportunity for viruses to jump the species barrier.

Dr Wolfe said: "Ongoing collaboration with hunters in central Africa gives us the potential to predict and prevent disease emergence.

"Given the incredible potential costs of a new human retrovirus spreading into the general population, the development of sentinel systems for forecasting disease emergence - such as long-term surveillance of hunters - should be seen as a human health imperative."

Dr Deenan Pillay, an expert in virology at University College London, UK, told the BBC News website that it had been thought few viruses jumped the species barrier.

"This research suggests that there seems to be far more transmission of a whole range of primate viruses into humans than was previously thought," he said.

"But that is not alarming in its own right. If the virus fails to replicate, or to be passed on to others, then it does not pose a threat.

"However, if cross-species transmission is such a frequent event, then all it takes is for one virus to really take hold in somebody, and be passed on to others for it to take off in humans."

animal factor

Virus linked to prostate tumours

Prostate cancer is a major killer

Scientists have produced compelling evidence that a virus known to cause cancer in animals is linked to prostate cancer in humans.

The researchers from the University of Utah and Columbia University medical schools found the virus in 27% of the 200 cancerous prostates they looked at.
They say it was associated with more aggressive tumours and found in only 6% of non-cancerous prostates.
The finding raises the prospect of one day producing a vaccine.
Previous research has linked XMRV (Xenotropic murine leukaemia virus) to prostate cancer but not specifically to the aggressive form of the disease.
Retrovirus
XMRV is a retrovirus like HIV which works by inserting a copy of its own DNA into the chromosomes of a cell they infect.

We still don't know that this virus causes cancer in people, but that is an important question we are going to investigate. Dr Ila Singh, University of Utah

Where this occurs next to a gene that regulates cell growth it can disrupt the normal development of the cell.
XMRV is known to cause leukaemia and other tumours in animals.
Dr Ila Singh, who led the study from the pathology department at the University of Utah, said: "We still don't know that this virus causes cancer in people, but that is an important question we are going to investigate.
"One of the things peculiar about this virus is that it has an androgen response element - it grows better in the presence of testosterone and possibly other steroid hormones.

PROSTATE CANCER FACTS Most common cancer in men in UK 10,000 die each year Most cases are in those aged 70-74 Higher rates in most deprived populations Source: Cancer Research UK

"This is particularly interesting because if we can prove that it responds to oestrogen it could have a role in other cancers.
"We are already looking at the bodies of 100 women and 100 men, who died from other causes, to see if any other organs carry the virus."
Risk factor
Dr Helen Rippon, Head of Research Management at The Prostate Cancer Charity, said the research was intriguing but posed several key questions about the role the infection plays in prostate cancer.

It is critically important to identify key triggers of prostate cancer to improve early detection Dr Helen Rippon, Prostate Cancer Charity

She said: "Around the world, extensive work is being undertaken to identify risk factors for prostate cancer which will enable treatments and tests for the disease to be refined.
"It is critically important to identify key triggers of prostate cancer to improve early detection of the disease in men with potentially life threatening prostate cancer."
Dr Chris Parker, Cancer Research UK's prostate cancer expert at the Institute of Cancer Research said: "This exciting study raises the possibility that the virus might contribute to the development of some prostate cancers.
"In the future, if it turns out to be true, then we could speculate about the possibility of vaccination to protect against prostate cancer, similar to the approach now used to prevent cervical cancer."

animal / disease

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