Vaccine 'could cut HIV TB deaths'

A vaccine could cut tuberculosis cases among HIV-positive Africans by almost two-fifths, a US study suggests.

The lung infection is the most common cause of death among HIV patients in the continent.

Journal Aids reports that Dartmouth Medical School research involving 2,000 people found significantly fewer TB cases in vaccinated patients.

An expert said the jab could be a cheaper option for countries struggling to find money for extra anti-HIV drugs.

HIV patients are particularly vulnerable to TB because their immune systems are compromised.

The vaccine works by boosting the immune responses of patients who have already been given the BCG vaccine earlier in life.

In itself, the BCG jab may offer some protection against TB, but this is far from certain, and protection may only last a few years after immunisation.

The researchers from Dartmouth Medical School in the US tested it among 2,000 HIV positive patients in Tanzania over a seven-year period.

The number of confirmed TB cases was 39% lower in the vaccinated group.

First vaccine

Professor Ford von Reyn, who led the study, said it was a "significant milestone".

One theory now suggests that patients could be given the booster jab as soon as they are diagnosed with HIV, before antiretroviral drugs are needed.

Alvaro Bermejo, executive director at the International HIV/Aids Alliance, said that the other way of fighting TB in HIV patients might be to give them antiretrovirals earlier, an expensive option compared with a vaccination programme.

He said: "This is a very important finding - it is the first time we are going to have a vaccine which is influential in preventing opportunistic infections in HIV patients.

"TB is a massive problem - a third of people living with HIV in Africa are infected with it.

"The reduction of 39% seen in Tanzania, although not fabulous, is a good result."

Tasmanian devil facial cancer origins 'identified'

Researchers believe they have identified the source of fatal tumours that threaten to wipe out the wild population of Tasmanian devils.

Writing in Science, an international team of scientists suggest cells that protect nerves are the likely origin of devil facial tumour disease (DFTD).

The disease is a transmissible cancer that is spread by physical contact, and quickly kills the animals.

DFTD has caused the devil population to collapse by 60% in the past decade.

"To look more closely at the tumours' origin, we sequenced the genes that are expressed in this devil cancer and compared them with other genes that are expressed in other devil tissues," explained lead author Elizabeth Murchison, from the Australian National University in Canberra.

She told the Science podcast the team's findings delivered surprising results.

"We found that the tumours expressed genes that were normally only expressed by Schwann cells, which are cells that are found in the peripheral nervous system that protect nerves."

'Genetically distinct'

The researchers sampled 25 different tumours from all over Tasmania, the only place on the planet where the world's largest carnivorous marsupials are found.

DEVILS IN DETAIL Scientific name: Sarcophilus harrisii Devils were given their common name by early settlers, who were haunted by "demonic growls" Largest living carnivorous marsupial Now only found in Tasmania Can live up to five years in wild Weight: male 10-12kg; female 6-8kg They favour habitats where they can shelter by day and scavenge by night

They found that the growths were genetically distinct from their hosts, but were identical to one another.

Dr Murchison, who is also a researcher at Cold Spring Harbor Laboratory, US, said the teams findings had a number of positive outcomes: "Most importantly, this has led to the development of a diagnostic test for the disease.

"Devils are susceptible to a number of different types of cancer. Just like humans, they can get breast cancer, leukaemia, etc - especially in their old age.

"Sometimes it can be difficult to tell the difference between these types of cancer and the transmissible disease.

"Now that we know that these very specific Schwann genes are expressed in the cancer, we can use these genes as diagnostic markers."

DFTD was first described in the mid-1990s, when devils with large facial tumours were photographed in north-eastern Tasmania.

By the end of 2008, the disease - which kills infected animals within nine weeks - had been confirmed at 64 locations, covering more than 60% of the Australian island state's mainland.

Experts warn that without intervention, the disease could wipe out the wild population of the world's largest carnivorous marsupial within decades.

Dr Murchison hoped identifying the catalogue of genes associated with DFTD would lead to the development of vaccines, or possibly therapies.

The disease usually kills infected devils within nine weeks

"As yet, unfortunately, there is nothing we can do to help the devils that have the disease," she said.

"This devil facial cancer is very unusual as it is an infection cancer; it is a little bit like an organ transplant," she said.

"In an organ transplant, you have an organ that is transplanted into an unrelated individual. In the case of the devil cancer, you have a cancer that is transplanted into another unrelated devil through biting.

"One of the big questions about this cancer is why it is not being rejected or being recognised as a foreign graft.

"If we could understand that... we could perhaps use this data to develop a vaccine that could help the devils' immune system reject the cancer before it takes hold."