Avian flu research on the move

During the past two years, outbreaks of influenza A (H5N1) occurred among poultry in nine countries in Asia. The influenza A virus is a subtype currently infecting birds in Asia. Two antiviral medications (amantadine and rimantadine) currently resistant to infected birds in Asia are commonly used for the influenza.

However, the influenza viruses have the ability to mutate, with the possibility of infecting humans with the H5N1. For this purpose, two other antiviral medications, zanamavir and oseltamavir (brand name Tamiflu), may probably work to treat flu caused by the H5N1 virus. Further trials are needed to determine how far they will be effective.

The Public Health authorities in Australia have recommended guidelines for travel to bird flu infected regions. Precautions include the need to avoid poultry farms, contact with animals in live food markets, and any surfaces that appear to be contaminated with faeces from poultry or other animals. Details of the government’s travel advisory are available at http://www.smartraveller.gov.au/.

In this connection Dr Suresh Mittal and his colleagues, from the Purdue University and Centers for Disease Control and Prevention (CDC) in USA, say that the current vaccines are designed for strains of flu found in local areas only. These vaccines are effective so long as the virus does not change form. The existing vaccines will have limited success against new strains of avian influenza. Therefore, every time bird flu mutates, vaccines must be redesigned.

New research to aid bird flu
Dr Suresh Mittal and his colleagues from the National Institute of Allergy and Infectious Diseases (NIAID) have now received a $1.6 million grant to focus on research using adenovirus — harmless virus — as a transmitting agent for a vaccine to fight off strains of the avian influenza viruses. The technology for how to grow large amounts of adenovirus and how to purify it is not new as it is already practiced in clinical trials for gene therapy using adenoviruses as vectors. The goal of this new research is to use the adenovirus ventor and develop an effective avian influenza virus vaccine that will provide long-lasting and broad immunity against multiple strains of this virus.

The approach
Dr Mittal says "The proteins that form the basis for all of today's flu vaccines are grown in fertilized chicken eggs. It takes months to produce a new vaccine for a new virus strain using this method and limits vaccine supplies due to shortages in eggs for the purpose. The egg production method also creates difficulty in redesigning vaccine to keep pace with virus mutations. When these types of viruses strike humans, they also strike poultry. In that case, the availability of fertilized eggs to make enough vaccine is compromised.

"So, do we still want to depend on the egg to make our flu vaccines? Even with a recently developed vaccine based on growing a single protein of H5N1, it would be difficult to rapidly produce enough protective medication to stem a pandemic. Furthermore, a large quantity of an adenovirus-based vaccine could easily be produced on short notice. The additional advantage of using an adenovirus as a vector, or transporter of vaccine into cells is that it could be mass produced much more quickly than with current methods”.

Suresh Mittal and Harm HogenEsch are both co-principal investigators in Purdue's Department of Veterinary Pathobiology, Centre for Comparative Medicine, College of Agriculture, School of Veterinary Medicine and the Indiana University Medical School. The co-investigators in the research are Jacqueline Katz and Suryaprakash Sambhara from the CDC. The centre researches animal and human diseases to find new treatments and cures.

References

• Susan A. Steeves, Sep 2005 http://www.medicalnewstoday.com/medicalnews.php?newsid=30832
• Purdue Department of Veterinary Pathobiology http://www.vet.purdue.edu/vpb

• Centres for Disease Control and Prevention http://www.cdc.gov

• World Health Organization http://www.who.int/en