April 01, 2006

 

 Vaccines and veterinarians to tackle the spread of avian influenza - April 1, 2006

 
posted March 15, 2006
 

Researchers recently developed new vaccines for the H5N1 avian influenza virus, which had spread to birds on three continents by late winter—also prompting the Department of Agriculture to seek veterinarians to volunteer for overseas assignments.

A team from the Centers for Disease Control and Prevention and Purdue University published a study in the Feb. 11 issue of Lancet about a vaccine that protects mice against several strains of the H5N1 virus. A team from the University of Pittsburgh, CDC, and USDA published a study in the Feb. 15 Journal of Virology about a vaccine that protects mice and chickens.

The researchers developed the vaccines by genetically engineering adenoviruses, which cause respiratory illnesses such as the common cold. The altered adenoviruses have the same hemagglutinin protein on the surface that allows the H5N1 virus to attach to cells. The idea is that the immune system, in confronting the altered adenoviruses, learns how to fight the H5N1 virus.

In the CDC-Purdue study, an altered adenovirus caused the immune systems of mice to produce both antibodies and T-cells to attack the H5N1 virus. The vaccine provided effective protection against death and disease. In the Pittsburgh study, an altered adenovirus protected mice in a similar manner. Chickens that received subcutaneous vaccinations also survived, while all the unvaccinated chickens died within days of intranasal exposure to the H5N1 virus.

One advantage of altered adenoviruses is that they grow quickly in cell culture. The traditional approach to influenza vaccines is to grow the influenza viruses slowly inside chicken eggs, which could be scarce during an outbreak of infection with the H5N1 virus.

Another advantage of the altered adenoviruses is that they are live vaccines—though they are replication-incompetent—so they may activate the immune system better than the traditional, inactivated influenza vaccines.

Also, the altered adenoviruses show promise of being effective against mutations of the H5N1 virus, according to the researchers. Avian influenza virus would have to mutate before it could pass directly from person to person.

According to the World Organization for Animal Health, Asia has had the most outbreaks of H5N1 avian influenza. By early March, the organization had received multiple reports of outbreaks in Europe and Africa. The World Health Organization had received reports of 175 total human cases of H5N1 avian influenza, with 96 deaths. At press time, the organization had also reported that domestic cats and a stone marten in Germany had contracted the virus.

The USDA Animal and Plant Health Inspection Service is responding with expertise in epidemiology and laboratory diagnostics, as well as field experience in the eradication of avian influenza and exotic Newcastle disease. The APHIS plan includes developing a list of experts available for four types of assignments:

  • teams, to travel to countries experiencing outbreaks of avian influenza as part of a broader U.S. government team, for one to two weeks
  • teams and individuals, to build international capacity for responding to outbreaks of avian influenza, for one to three weeks
  • individuals, overseas assignments, for four to six months
  • individuals, overseas assignments, for one to two years

Veterinarians and other volunteers can express interest by e-mailing Dr. Jennifer Grannis at Jennifer.L.Grannis@aphis.usda.gov or Dr. Percy Hawkes at percywhawkes@hotmail.com. Drs. Grannis and Hawkes will contact volunteers to obtain information for the list of experts. The USDA will cover all the costs of the assignments.