Many experts have no doubt bird flu pandemics definitely would happen in future. That is why additional research is necessary to understand mechanisms of bird viruses infecting human beings and risks of pandemics. Such studies exist and were performed in Russia within ISRC/DARPA project, and their results were published in “Proceedings of Russian Academy of Medical Sciences” magazine.

Think-tank from Russian State science centre “Vector” and Moscow Sechenov Medical Academy suggests a technique for defining potential vulnerability of human beings to new virus strains while experimenting with cells cultures and laboratory animals. Suggested method is very accurate, though quite complicated.

Flu virus, which for several years was considered to infect only birds, now threatens mankind. Medics warn about possible danger coming from other virus strains of animal origin or their mutants. Determining human vulnerability to new viruses before they adapt themselves to human population and become pandemic, allows developing effective countermeasures against these viruses in time. But how can a virus be tested? Medics measure viral infecting power as ID50, which is an infecting dose, making half of organisms, ever contacted with virus, sick. Of course, no one is going test infecting power of bird flu on humans. Another technique exists – scientists infect cell cultures with a virus of their interest. Since flu virus first attacks respiratory tract, medics performed their experiments on trachea and lung cells. However, we should not forget that since organism cells are much more resistible to viruses than cell cultures, vulnerability is likely to be overstated. Every organism is usually protected by its immune system, which cell cultures simply do not have.

Researchers suggest following solution – testing viruses on model objects: mice or rats. The testing process has several stages: during first stage animals inhale aerosol with infecting particles, and then viral ID is determined. Second stage involves working with trachea and lung cells of a model object, and finally researchers determine a possibility of a cell being infected with said virus, as well as average yield of this virus in a cell. All these values contribute to a scale coefficient, which formula considers difference between cell culture conditions and a living organism.

Abovementioned experiment was held on laboratory animals, mice and rats, which were infected by A/Aichi/2/68 (H3N3) bird flu strain. Experiments of Russian scientists showed that key factor for animal vulnerability to flu virus is trachea. Such results correspond with data in already published articles, saying that flu infection starts in upper parts of respiratory tract, and then goes down to lungs. In almost every case real vulnerability of tracheae and lungs to this virus is the same as predicted in the experiments with cell cultures.

Source:
    Russian Science News

Kizilova Anna