Testing for "new" tick-borne diseases
Neoehrlichiosis is one of the so called "new" tick-borne diseases. The disease is caused by the bacterium Neoehrlichia mikurensis, which can be transmitted to humans via tick bites. The first case of disease in humans in Europe was registered in Sweden in 2010. Most people who become infected probably have no symptoms or mild symptoms, but it is known that the bacterium can cause blood clots and bleeding in the elderly or people with a weakened immune system. Other possible symptoms is fever (often high and recurrent), muscle and joint pain, headache, edema, skin rash, fatigue / tiredness, vomiting, diarrhea. Christine Wennerås and Anna Grankvist from Sahlgrenska University Hospital in Sweden, are now working on a sub-project in NorthTick where the goal is to develop an antibody test for Neoerlichia.
In the NorthTick project, you will, among other things, work with the development of an antibody test for Neoerlichia. Diagnostics for neoerlichia today is done by PCR testing. Why do we not have an antibody test for neoerlichia?
In order to develop an antibody test, it is necessary to be able to produce a larger amount of Neoehrlichia-specific antigens. We were not able to grow the bacterium until 2019 and even today this cultivation is very small-scale. It is possible to use synthetic antigens, but this requires knowlegde about the Neorlichia bacterium's genome- which we have recently found out by sequencing cultured bacteria.
How do you go about making an antibody test? What are the challenges?
Antigen is extracted from neo-specific antigens from cultured bacteria, or synthetic antigens can be made by looking at the bacterium's genome and cloning a selected sequence into a faster-growing bacterium that can then express the Neoehrlichia protein. When you have a protein/antigen, this can be used to find any neoehrlichia antibodies in the blood of patients. The challenge is to make an antibody test that is easy to use and that is specific against Neoehrlichia.
Why is it important to get a commercial antibody test for neoerlichia? Isn’t the PCR test good enough?
A PCR test detects bacteria circulating in the blood today (shows an ongoing infection) while antibody tests can detect previous infection. Neoehrlichia is the second most common disease-causing bacterium in ticks in the Nordic countries, after Borrelia. We still don’t know how common Neoerlichia infections are in tick-infested areas. We also do not know what different types of symptoms/diseases the bacterium can cause. Here, antibody analysis would be valuable.
In this project you have collaborated with partners in Sweden and Norway. What is the benefit of a collaborative project like NorthTick?
You can exchange experiences and learn from each other, as well as learn how diagnostics work in other countries etc.
And have there been any challenges along the way?
Because Neoehrlichia is an intracellular bacterium and patient cases are still relatively few (although they have recently increased), we always have a shortage of materials / samples to work with. Neoehrlichios is also “new” tick-borne disease and we are still learning about it! Corona has of course also been a challenge. We not only work with research on Neoehrlichia but are also active in clinical microbiology at SU.