Virus with an eggshell

August 18, 2017

Avian flu can be transmitted from birds to humans; transmission among humans, however, is limited. The reason may be an eggshell-like mineral layer that the virus acquires due to the high calcium concentration in the intestines of birds. As reported by Chinese researchers in the journal Angewandte Chemie, these mineralized viruses are significantly more infectious and, in addition, more robust and heat stable than the native viruses.

Avian flu is a highly infectious disease among birds that has developed into a serious threat to human health. Close contact with diseased birds or their feces is considered to be the primary source of infections in humans. Transmission between humans is limited, however, which indicates that these viruses cannot directly infect humans. Previously it was assumed that these viruses crossed the species barrier as a result of mutation or recombination with another pathogen. More recent results demonstrate that avian flu viruses isolated from infected humans have the same gene sequences as those from birds.

So how is it that humans catch the disease from birds? Researchers working with Ruikang Tang at Zhejiang University (Hangzhou, China) claim that it is because the viruses acquire a mineral "shell" in the bird intestines. They discovered that viruses can become mineralized under calcium-rich conditions. Naturally, the digestive tract of birds--the primary location of avian flu viruses--provides just such a calcium-rich environment, so that the birds can make egg shells.

Experiments with a solution that imitates the bird intestine environment allowed the researchers to demonstrate that 5 to 6 nm shells of a calcium phosphate mineral form around H9N2 and H1N1 viruses. In both cell cultures and mice, these mineralized viruses proved to be significantly more infectious--and deadly--than the native viruses. In humans, avian flu viruses infect the airways and are then found in bodily fluids, where the calcium concentration is too low for mineralization.

The mineralized shell changes the electric surface potential of the viruses. This causes mineralized viruses to adsorb much more efficiently onto the surfaces of future host cells. The mechanism for uptake into the host is also different. Normally, the virus docks at receptors on the cell surface and is then brought into the cell. The mineral layer inhibits this--but clearly stimulates very efficient uptake on its own. Within the cell, the mineralized viruses enter into lysosomes, whose slightly acidic environment dissolves the mineral shell and releases the viruses.

This new information explains why humans are more likely to catch avian flu from birds than from their fellow humans, and may help in the development of new approaches to battling avian flu.
-end-
About the Author

Dr. Ruikang Tang is a Qiushi Chair Professor at Zhejiang University, and is the Leader of an interdisciplinary biomineralization research center in the Department Chemistry and Qiushi Academy for Advanced Studies. He has been working in the biomineralization area for over 20 years. Among other awards, he is the receipient of Changjiang Scholar Program Fellowship.

http://person.zju.edu.cn/en/0005003

Wiley

Related Calcium Articles from Brightsurf:

A new strategy for the greener use of calcium carbide
Computational chemists from St Petersburg University and the Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences have developed a new strategy for using calcium acetylide in the synthesis of organic compounds.

New link between calcium and cardiolipin in heart defects
To function properly, the heart needs energy from cells' powerhouses, the mitochondria.

'Give me the calcium!' Tulane virus takes over cellular calcium signaling to replicate
Researchers uncover the first piece of functional evidence suggesting that Tulane virus and human norovirus use viroporins to control cellular calcium signaling.

Carbon dots make calcium easier to track
Prof. DONG Wenfei's research group from the Suzhou Institute of Biomedical Engineering and Technology (SIBET) has developed a new type of fluorescent carbon dot that can effectively detect calcium levels in cells.

Calcium batteries: New electrolytes, enhanced properties
Calcium-based batteries promise to reach a high energy density at low manufacturing costs.

Chelated calcium benefits poinsettias
Cutting quality has an impact on postharvest durability during shipping and propagation of poinsettias.

New study uncovers the interaction of calcium channels
Korean researchers have identified the interactions of the combinants among calcium channel proteins that exist in nerve and heart cells.

Calcium-catalyzed reactions of element-H bonds
Calcium-catalyzed reactions of element-H bonds provide precise and efficient tools for hydrofunctionalization.

A bioengineered tattoo monitors blood calcium levels
Scientists have created a biomedical tattoo that becomes visible on the skin of mice in response to elevated levels of calcium in the blood.

The dinosaur menu, as revealed by calcium
By studying calcium in fossil remains in deposits in Morocco and Niger, researchers have been able to reconstruct the food chains of the past, thus explaining how so many predators could coexist in the dinosaurs' time.

Read More: Calcium News and Calcium Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.