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Bird flu viruses in eggshells become dangerous to humans
Several times in recent years, transmissions of the bird flu virus to humans have occurred and experts have urgently warned of an imminent pandemic, the pathogens should be transferable between people. The fact that the viruses can infect humans, according to a recent study on a kind of egg shell, which build up the pathogens in the body of the birds. However, an interpersonal transfer is unlikely.
Cause of infections in humans "could be an eggshell-like mineral layer, which get the virus due to the high calcium concentration in the intestine of birds," reports the journal "Angewandte Chemie" in a press release on the current study results of Chinese scientists. In their study, researchers from Zhejiang University (Hangzhou, China) demonstrated that the mineralized viruses are significantly more infectious and more robust and heat-stable than native viruses.
Bird flu viruses can also infect humans and usually affect the respiratory tract. A special mineral protective layer, which they build up in the body of birds, makes the pathogens especially infectious for humans. (Image: psdesign1 / fotlia.com) Bird flu viruses also pose a threat to humans
Although avian influenza is a highly contagious disease among birds and can eradicate whole populations, so far relatively few outbreaks have been reported with transmission to humans. However, according to experts, viruses are considered to be a serious threat to human health. For in close contact with sick birds or their excretions, an infection can occur. Contagion among humans remains limited, which suggests that these viruses can not directly infect humans, reports the journal "Angewandte Chemie".
Mutations do not cause infections in humans
If bird flu viruses become transmissible between humans too, a pandemic threatens in the worst case. Such interpersonal transferability could occur through mutations of the viruses, so the previous assumption. The already existing infections in humans have been attributed by medical scientists to mutations of the viruses, which, however, the current study results is a misjudgment. Because the findings show that avian influenza viruses, which were isolated from diseased humans, have the same gene sequences as the pathogens from birds. The previous assumption that the viruses could cross the species boundary through mutations or recombination with other pathogens must therefore be corrected.
Structure of a mineral protective cover
According to the results of the Chinese researchers, the cause of bird flu infections in humans is not a mutation, but the formation of a kind of egg shell around the pathogens. In the bird's intestine, the viruses build a mineral protective layer under the calcium-rich conditions, explain the scientists. "Based on experiments in a bird's milieu inspired solution, the researchers were now able to show that around H9N2 and H1N1 viruses form 5 to 6 nm thick shells of a calcium phosphate mineral," reports the journal "Angewandte Chemie". These mineralized viruses would have been found to be significantly more infectious - and more lethal - than native in both cell culture and mice.
Effects of the mineral protective layer
According to the experts, the mineral shell changes the electrical surface potential of the viruses, which allows the mineralized viruses to adsorb much more effectively to the surface of future host cells. Also, the recording mechanism in the cell is another. Because normally the virus attaches to receptors on the cell surface and is then slipped into the cell. This is prevented by the mineral layer of the viruses, but obviously at the same time stimulates a very effective intake by other means. Finally, the mineralized viruses within the cell reach the so-called lysosomes, whose slightly acidic environment dissolves the mineral coatings and releases the viruses.
Since the avian influenza viruses in humans primarily affect the respiratory tract and then move mainly in body fluids that have too low calcium concentrations for mineralization, the pathogen here lacks the protective shell and they are therefore less infectious. Overall, the findings explain why people are more likely to get infected with birds than with infected people, the scientists emphasize. It may also be possible to derive new approaches to combating bird flu, researchers hope. (Fp)