West Nile lookalike gives vaccine hope

Researchers at the University of Queensland have developed a clone of the locally endemic Kunjin virus, and successfully trialled in mice it as a West Nile virus (WNV) vaccine.

According to Dr Roy Hall, from UQ's School of Molecular and Microbial Sciences, West Nile and Kunjin have very similar genetic sequences, but Kunjin produces only rare, non-fatal incidence of disease.

"I have been working on Kunjin for a long time with Dr Alex Khromykh, from the Sir Albert Sakzewski Virus Research Centre at Brisbane's Royal Children`s Hospital," he said.

"We have been looking at the epidemiology and characteristics of this virus, and having managed to clone and attenuate the virus, we trialled it on mice and found that it produced WNV antibodies and protected them from disease," he explained.

Hall, Dr Khromykh and colleagues injected mice with a vaccine in the form of attenuated Kunjin virus producing DNA. After 19 days, the mice had produced antibodies against both Kunjin and West Nile, and developed resistance to previously lethal doses of WNV.

WNV is proving an increasing threat to both North and South America, with most states in the US as well as Canada and Mexico reporting cases. The mosquito-borne virus is highly virulent, and causes flu-like symptoms and encephalitis with a very high morbidity and mortality rate.

Although not yet established in Australia, it has caused numerous human and equine fatalities in the US since 1999. Because no known cure exists, WNV diagnostics and vaccines are increasingly becoming the focus of current research.

"The problem is that if the disease reaches Australia, it could not only be a problem for humans, but its effect on birds could dramatically upset the local ecology," said Hall.

"The strain of WNV found in the US results in a much higher level of morbidity than the African or European strains, with the potential to seriously affect the numbers of birds of prey -- something that could have serious knock-on effects on the Australian rodent population.

"Partly because of this, we are working on a WNV diagnostic to enable us to identify it apart from Kunjin, which is endemic in parts of Australia. We will hopefully run more trials on horses soon," he added.

Hall said he expected the research to be submitted for publication in the near future.

US fears as West Nile spreads

Meanwhile, the West Nile virus is spreading faster and into new areas of the United States this year, prompting fears that the nation could be facing another record outbreak of the deadly mosquito-borne disease.

The Centres for Disease Control and Prevention, which has tracked the virus since it first surfaced in the Americas in 1999, reported on Thursday that the virus had killed four people and infected about 150 others in 16 states this summer.

At this same time last year, the CDC had confirmed slightly more than 100 cases in four states. The 2002 outbreak killed 284 people and infected about 4,000 others before becoming dormant in the winter.

The bulk of the record number of cases last year occurred in the six weeks after the first week of August, primarily in southern and midwestern states. This year's outbreak so far is centered in Colorado, which reported no human cases in 2002.

There have been 111 cases and four deaths due to West Nile in the state, according to Colorado health officials. The CDC, however, has positively linked only 72 cases and one death in the state to the virus.

"We are starting the epidemic with more cases and more areas affected than last year," Dr Julie Gerberding, director of the CDC, said in a news conference in Atlanta. "If the same pattern proves to hold true, we could be seeing an even greater number of affected people [this year]."

-- Additional reporting by Reuters