For many years scientists thought that mosquitoes provided the disease organisms which they spread with a relatively free ride because the insects didn’t have much in the way of natural defenses to fight off these microscopic stowaways.
Hillyer Lab / Vanderbilt University
This microscopic fluorescent image of the mosquito's circulatory system shows muscle cells in green; cellular DNA in blue and periostal hemocytes in orange.
Recent research, however, has revealed that mosquitoes have surprisingly sophisticated immune systems. Unlike humans and most other animals, mosquitoes do not generate antibodies that identify and attack specific infectious agents. However, they have developed alternative methods for destroying various pathogens, including parasites that cause malaria.
In the latest study of the mosquito’s immune system – published online on Nov. 29 in the journal PLOS Pathogens – a pair of Vanderbilt biologists have discovered mosquitoes possess a previously unknown mechanism for destroying pathogens that takes advantage of the peculiarities of the insect’s circulatory system to increase its effectiveness.
Studies of this sort are providing the information needed to manipulate the mosquito immune system to block malaria parasites more effectively and to develop other novel disease control strategies.
“It may come as a surprise to many people, but mosquitoes get sick too and they need to protect themselves,” said Julián Hillyer, assistant professor of biological sciences, who conducted the research with graduate student Jonas King.
“The mosquito’s immune system isn’t as complex as ours. About 350 of its 12,500 genes have immune functions,” Hillyer said. “But it is remarkably effective. The vast majority of the malaria parasites that infect a mosquito die before they can get into the salivary glands where they can infect vertebrate prey, such as humans.”
“Pathogens like those that cause malaria, dengue and yellow fevers come from the female’s blood meal and end up in the mosquito’s gut,” Hillyer said. “They then leave the gut and enter the mosquito’s main body cavity, and from there they have to make their way to its salivary glands.”
Inside the body cavity, pathogens have to fight two main forces: the swift circulation of the mosquito’s own blood, and attacks from the mosquito’s immune system.
The mosquito’s circulatory system is dramatically different from that of mammals and humans. A long tube extends from the insect’s head to tail and is hung just under the cuticle shell that forms the mosquito’s back. The heart makes up the rear two-thirds of the tube and consists of a series of valves within the tube and helical coils of muscle that surround the tube. These muscles cause the tube to expand and contract, producing a worm-like peristaltic pumping action.
Most of the time, the heart pumps the mosquito’s blood—a clear liquid called hemolymph—toward the mosquito’s head, but occasionally it reverses direction. The mosquito doesn’t have arteries and veins like mammals. Instead, the blood flows from the heart into the abdominal cavity and eventually cycles back through the heart. “The mosquito’s heart works something like the pump in a garden fountain,” Hillyer said.
In order to make it to their goal, pathogens must pass through one of the heart valves. As a result, the valves act as physical bottlenecks during the migration of viruses and malaria parasites.
Cells called hemocytes are an important element in the mosquito’s defense system. These are special immune cells carried in the hemolymph that play a role analogous to white blood cells in humans. They circulate around the body with the hemolyph and attack foreign cells and viruses when they contact them.
What Hillyer and King discovered was that when a mosquito becomes infected with bacteria or malaria parasites, a population of hemocytes is recruited to the valves of the heart, where they capture and destroy invading pathogens. These new mosquito immune cells, which they have named periostial hemocytes, substantially increase their odds of encountering and destroying invaders by congregating in areas of high hemolymph flow.
“What happens to these pathogens while they are carried inside the mosquito’s body is a critical part of the infection cycle that we are just beginning to understand,” said Hillyer.
This research was funded by the National Science Foundation grant number IOS-1051636.
Visit Research News @ Vanderbilt for more research news from Vanderbilt. [Media Note: Vanderbilt has a 24/7 TV and radio studio with a dedicated fiber optic line and ISDN line. Use of the TV studio with Vanderbilt experts is free, except for reserving fiber time.]
David F. Salisbury | Vanderbilt University
Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction