The α-gal Syndrome - Investigating Immune Reactions to Tick Bites

Ticks bearing pathogens can transmit infectious diseases such as Lyme borreliosis, tick-borne encephalitis and others. Recently, a non-infectious human disease, namely the alpha-gal syndrome (AGS), was shown to be of tick origin. AGS, characterized by the presence of IgE antibodies directed against the carbohydrate galactose-α-1,3-galactose (alpha-gal or α-gal) is also known as 'red meat allergy'. Unlike the more 'classical' food allergies, symptoms are delayed and may appear several hours after ingestion of mammalian meat or dairy products, often hampering a timely clinical diagnosis.

Individuals with occupational or recreational outdoor activities often experience frequent tick bites and they have a higher risk of developing AGS. There are still many questions regarding the etiology and the development of the disease. Not every tick bite will lead to sensitization and it is presently unclear how the human immune system reacts to tick bites and why the initial events after a tick bite will either lead to a short-lived natural immune defense or shift the immune response to an uncontrolled Th2 response which potentially leads to allergic disease. Tick bites also bear the risk of pathogen transmission, and there is a clear need for monitoring tick bites for public health purposes.

The present study will investigate early peripheral immune responses in individuals bitten by a tick. The investigators hypothesize that the pathway to allergic sensitization to α-gal is already predictable from the peripheral immune response early after a tick bite and that an adequate protective defense against ticks can be distinguished from an allergic inflammatory response by discrete marker signatures shortly after the tick bite. Additionally, the investigators will collect population-based tick surveillance data which will be an important contribution to public health. The advertising of the study for recruitment purposes will be combined with information on tick avoidance and monitoring in case of a bite, thus contributing to public awareness and education.

The objectives of the study are:

i) To determine peripheral inflammatory protein and cellular as well as intracellular signatures leading to either a normal and self-limited human immune defense or to allergic sensitization; ii) To generate surveillance data on tick-related diseases (pathogens/allergy) in individuals experiencing a tick bite.

In order to achieve these objectives, the researchers will perform a deep immune analysis of blood samples collected upon a tick bite by using multi-omics and high-resolution techniques. They will longitudinally follow 100 study participants for several weeks and determine their serological status. Blood will be collected at day 1, then 4 to 6 weeks after the bite. For 2 subgroups of participants, selected for their sensitization to a-Gal and a control group without a-Gal sensitization, a 3rd visit is planned 8 to 12 weeks after the bite for clinical assessment. A questionnaire on the 2 first visits will collect data regarding tick bite history, current tick bite, current health status, allergic disease, diet for meat and dairy products.

The tick responsible for the bite will also be collected. The species will be identified and analysed for tick-borne pathogens by PCR. The identification of the tick species and search for tick-borne pathogens will generate crucial data that are important for tick and tick-related disease surveillance in Luxembourg.