Featured Research

from universities, journals, and other organizations

Tick bacteria evade the immune system by variation in surface proteins

Date:
June 7, 2010
Source:
Norwegian School of Veterinary Science
Summary:
Scientists have shown that antigenic variation occurs in the tick bacterium Anaplasma phagocytophilum in cases of prolonged infection in lambs. In addition, certain varieties of tick bacteria lead to a prolonged infection of varying levels for at least six months and that the skin can act as a storage depot for bacteria.

Lambs are frequently infected by ticks.
Credit: Copyright Erik G. Granquist

Erik Georg Granquist's thesis examines infections caused by the bacterium Anaplasma phagocytophilum in lambs. This bacterium is the cause of the disease tick-borne fever in ruminants and granulocytic anaplasmosis in humans. The bacterium is transmitted by ticks and is the indirect cause of considerable animal welfare problems and financial losses in Norwegian sheep farming.

Related Articles


Granquist's findings have contributed to a better understanding of how the bacterium survives in the host animal over time. The results are an important step towards the development of a vaccination.

Granquist has researched variations in the bacterium's surface protein MSP2 (P44) -- the antigene that gives the largest immunogenic response and that consists of conserved and varied segments. Different proteins arise when gene segments combine, as the infection progresses. This is a strategy for evading the body's immune defence system. When the gene was cloned and sequenced as codes for MSP2 (P44) at different stages of an infection, large sequence variations in the surface protein were discovered.

By employing a number of different diagnostic methods, Granquist investigated how the immune system responds to antigene variation. He found that antibodies in infected lambs are targeted specifically at the different variants and areas of the bacterium's surface protein. He also observed that the serological reaction to variable and conserved surface proteins of the bacterium was short-lived and diminished over time.

In his thesis, Granquist studied how different variants of Anaplasma phagocytophilum carry out cyclic invasions of the blood. Lambs infected with one variant showed more frequent bacteraemia and had more circulating bacteria in their blood for a long time than lambs that were infected with another variant. Both variant-specific and individual differences in cyclic variation were revealed. This may be a clue as to why certain variants become more widespread in nature and can also explain why some variants of Anaplasma phagocytophilum lead to greater losses than other tick-infested pastures.

There has been a great deal of debate about whether endothelial cells may be important components in the development of infections and prolonged infections due to Anaplasma phagocytophilum. For this reason, Granquist studied skin biopsies from tick bites on lambs which had been naturally infected with Anaplasma phagocytophilum. His research revealed that the bacterium is seldom associated with endothelial cells, but can be found in other parts of the blood vessel wall and in infiltrates in infected cells around the tick bite. By means of substances in its spit, the tick can attract infected cells which are important for the bacterium's life cycle. These discoveries indicate that the skin can act as an important storage depot for bacteria.

Doctor of Veterinary Medicine Erik Georg Granquist presented his doctoral thesis on 2nd June 2010 for the title of Philosophiae Doctor (PhD) at The Norwegian School of Veterinary Science. His thesis is entitled: "Infection strategies and immune evasion of Anaplasma phagocytophilum in lambs"


Story Source:

The above story is based on materials provided by Norwegian School of Veterinary Science. Note: Materials may be edited for content and length.


Cite This Page:

Norwegian School of Veterinary Science. "Tick bacteria evade the immune system by variation in surface proteins." ScienceDaily. ScienceDaily, 7 June 2010. <www.sciencedaily.com/releases/2010/06/100607065858.htm>.
Norwegian School of Veterinary Science. (2010, June 7). Tick bacteria evade the immune system by variation in surface proteins. ScienceDaily. Retrieved November 28, 2014 from www.sciencedaily.com/releases/2010/06/100607065858.htm
Norwegian School of Veterinary Science. "Tick bacteria evade the immune system by variation in surface proteins." ScienceDaily. www.sciencedaily.com/releases/2010/06/100607065858.htm (accessed November 28, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Friday, November 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Research on Bats Could Help Develop Drugs Against Ebola

Research on Bats Could Help Develop Drugs Against Ebola

AFP (Nov. 28, 2014) In Africa's only biosafety level 4 laboratory, scientists have been carrying out experiments on bats to understand how virus like Ebola are being transmitted, and how some of them resist to it. Duration: 01:18 Video provided by AFP
Powered by NewsLook.com
New Dinosaur Species Found in Museum Collection

New Dinosaur Species Found in Museum Collection

Reuters - Innovations Video Online (Nov. 27, 2014) A British palaeontologist has discovered a new species of dinosaur while studying fossils in a Canadian museum. Pentaceratops aquilonius was related to Triceratops and lived at the end of the Cretaceous Period, around 75 million years ago. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Tryptophan Isn't Making You Sleepy On Thanksgiving

Tryptophan Isn't Making You Sleepy On Thanksgiving

Newsy (Nov. 27, 2014) Tryptophan, a chemical found naturally in turkey meat, gets blamed for sleepiness after Thanksgiving meals. But science points to other culprits. Video provided by Newsy
Powered by NewsLook.com
Classic Hollywood Memorabilia Goes Under the Hammer

Classic Hollywood Memorabilia Goes Under the Hammer

Reuters - Entertainment Video Online (Nov. 26, 2014) The iconic piano from "Casablanca" and the Cowardly Lion suit from "The Wizard of Oz" fetch millions at auction. Sara Hemrajani reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins