Dortmund/Bonn, 4th March 2022
When a person’s immune system reacts to a drug in an undesired and extreme way, doctors refer to this as a drug allergy. Although allergies only make up a small amount of the side effects of drugs, the symptoms go beyond just itchy rashes and fever. In the most serious cases, drug allergies can cause severe and potentially fatal reactions such as difficulties in breathing, organ failure and circulatory arrest. According to the World Allergy Organization (WOA), drugs are among the most common triggers of anaphylactic shock, the most severe form of an allergic reaction. That is why it is important for doctors to be able to diagnose drug allergies without any risks for patients. In the project ‘Analysis of Differential Gene and Protein Expression for In-vitro Detection of Drug Allergies’ (INA), scientists at ISAS are working together with the Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), the Clinic for Dermatology and Allergology of RWTH Aachen University Hospital and the biomedicine company Life & Brain GmbH in Bonn, in order to make a simple blood test for the diagnosis of drug allergies possible.
There are different ways to diagnose drug allergies. For example, doctors can conduct skin tests like prick- or intradermal tests. Furthermore, they can directly expose patients to a suspect drug via provocation tests. For the latter, patients take the relevant medication, for example as a pill. This usually happens during a stay at the hospital. However, conducting allergy tests directly on humans (in vivo) can be dangerous. “Provocation- and intradermal tests can cause reactions that range from uncomfortable to severe events. That is why patients often refuse to take these tests,” states Dr Amol Fatangare, who conducts research for INA at ISAS. The lab tests (in vitro) that are available now, for example blood tests like a detection method for specific antibodies in cases of immediate hypersensitivity, are reportedly less dangerous than skin- or provocation tests. However, they are currently only approved for few drugs or not suitable for routine diagnostics, according to BfArM.
The samples that Dr Amol Fatangare uses for his research are being stored at minus 80 degrees Celsius.
© ISAS
New blood test for a broad application
Fatangare and his colleagues are working on improving an existing blood test to make it suitable as a routine diagnostic for many different drugs and types of allergies. For this, the scientists examine the differential gene and protein expression of certain immune cells, the so-called peripheral blood mononuclear cells (PBMCs), of patients with known drug allergies. In other words, they analyse which genes and biomolecules change in the PBMCs during a reaction and, with regard to these drug allergies, look for characteristic biological commonalities, for biomarkers. “Allergy symptoms such as rashes, dizziness or fever can vary widely depending on the person and the drug,” Fatangare explains. No matter what and how severe the allergy symptom is – the bodily mechanism that underlies the reaction is very similar in most patients. As soon as the researchers discover one or more biomarkers, they can identify them using a simple blood test and thus quickly spot a drug allergy; without exposing patients to health risks.
While their colleagues in Bonn deal with the gene expression, the scientists at ISAS concentrate on the protein expression. With the aid of mass spectrometry, they analyse the PBMCs’ proteome, the entire set of proteins at a fixed point in time. This method, called proteomics, allows the researchers to examine the interactions between the proteins and their changes. They focus on several potential biomarkers such as the messenger interleukins in particular. At the same time, they adopt a non-targeted approach: “One could say that we are deliberately blindfolded when searching for biomarkers, so that we do not only look at interleukins,” Fatangare jokes. With this strategy, the biochemist wants to keep an open mind for all kinds of discoveries, even unexpected ones.
Searching for intra-individual differences
In order to find out what has changed after an allergic reaction, the scientists first divide the patients’ blood samples. At BfArM, they treat one half with the proven allergenic drug, whereas the other half remains untreated. The researchers of Life & Brain GmbH and at ISAS look for intra-individual differences in the gene and protein expression, for instance differences in the same individual’s blood cells upon allergenic drug treatment. This approach has two crucial advantages. First of all, the researchers can do with few samples, because all of the patients are at the same time in the treatment and control group. Second, the approach helps the scientists avoid individual differences: “If the samples were from different patients, it would be difficult to tell whether deviations in the protein expression were due to the drug or the different humans,” says Fatangare. In order to assign anomalies reliably to a single drug, the scientists would have to analyse samples from hundreds of patients. But with their method, samples from 20 people might be enough to gain meaningful data.
Time between allergy and blood sampling
“In 2021, we found out that the samples of some patients showed a very severe reaction to the drugs, while others hardly reacted at all. We wanted to determine whether that could be a result of the different periods of time between the allergy and the later blood sampling,” Fatangare sums up. The researchers’ aim is to analyse more patients’ samples for biomarkers in the PBMCs, before they optimise the test for a wider use.
How do skin tests for drug allergies work?
Allergic reactions to drugs mostly arise within the first hour after administration. In order to diagnose these immediate hypersensitivities quickly, doctors often use skin tests. For the so-called skin prick test, they drip a solution with the suspect allergen onto the forearm and lighty scratch the skin on that spot. Reddened and itchy welts show whether the immune system is overreacting – and the patient thus having an allergic reaction. The intradermal test is an example of a sensitive skin test. Instead of only testing on the surface, doctors inject the solution with the allergen directly underneath patients’ skin and watch whether a reaction occurs. This test is also suitable for the detection of a late reaction which can arise even days and weeks after taking a drug.
(Cheyenne Peters)
The project 'Analysis of Differential Gene and Protein Expression for In-vitro Detection of Drug Allergies' is funded by the European Fund for Regional Development (EFRE).
