Per Venge
Professor och överläkare, klinisk kemi.
Specialområden är inflammations- och immunbristdiagnostik.
Läs mer på forskargruppens sida under Uppsala universitet.
A synopsis of our previous and current research areas and interests
In 1972 we showed the existence of several highly basic proteins in the secretory granules of neutrophils. One of these was identified as having chymotrypsin-like proteolytic activity and consequently called by us the Chymotrypsin-like Cationic Protein (CCP). Some years after our discovery this protease was renamed Cathepsin G. Cathepsin G, however, was the first in a series of secretory proteins that we purified from the granules of neutrophils and eosinophils. Some others are described below.
HNL (human neutrophil lipocalin) was purified from the secondary granules of human neutrophil granulocytes. The biological function of HNL is still unknown, but suggested to be that of a siderophore. HNL has many other names such as NGAL (neutrophil gelatinase associated lipocalin). We have developed and patented a method to measure HNL in body fluids as a reflection of neutrophil activity and turnover. Such measurement is of interest in the distinction between various causes of acute infections, since the levels of HNL are highly raised in serum or plasma in patients with acute bacterial infections as opposed to the findings in patients with acute viral infections. The sensitivity and specificity of distinguishing between these conditions are superior other means such as plasma measurements of CRP (C-reactive protein). Recently NGAL measurement in urine was shown to be an early and sensitive marker of acute renal failure.
Other proteins that have been purified from the secretory granules are CEACAM8 or CD66b, N-acetylglucosamine-6-sulphatase and a hypothetical protein with phospholipase B activity. The latter is unique, since this kind of activity has not been identified in humans before.
Our current research is focused on the application of HNL in the clinical diagnosis of acute infections and acute renal failure and the development together with commercial partners of rapid and easy-to-use tests to measure HNL in a point-of-care setting.
The distinction between acute causes of infections is a very common clinical problem and is often quite difficult. The overprescription of antibiotics to acute viral infections mistakenly diagnosed as bacterial infections is also common and adds to the problems of development of antibiotic resistance. Better clinical tools are therefore needed and this project has the aim to develop such tools. We have therefore an ongoing research in which we try to identify new molecules that may be measured in blood or other body fluids. One example of this is the use of HNL from human neutrophils. Please see the description on the HNL-page. Another is soluble CEACAM8.
We have used the flow cytometer and identified CD64 on the blood neutrophils as one useful means to diagnose acute bacterial infections, since the expression of CD64 normally is very low on neutrophils and highly raised in conjunction with bacterial infections. Our results suggest that this method is useful both in newborns, children and adults. One major problem in the evaluations of new tools for this diagnostic distinction is the patient selection i.e. what should be the gold standard. How do we know that a patient with an acute infection and judged as an acute viral infection is not challenged by a bacteria as well. Is the false-positive result with a marker actually a true-positive indication of bacterial infection? Isn’t it so that bacterial infections can heal quite quickly without antibiotics and is it so that it is only the overwhelming bacterial infections that need antibiotics that are judged as bacterial infections? In our studies our clinical colleagues at the infectious department have made every effort and any modern means to diagnose correctly these entities, but how correct are they? Nobody knows. Maybe someone who reads this page has a suggestion to this dilemma and help us solve this problem so we can evaluate our methods better.
The ECP molecule is a highly basic molecule containing a large number of arginine residues. We described and named this molecule in the mid 70tieths. ECP is produced by eosinophil granulocytes and to a minimal extent also by monocytes. It is, however, not produced by neutrophils, although small amounts of ECP may be found in these cells. The reason being that neutrophils specifically take up the molecule from the environment. ECP has several interesting biological activities. Thus, it is cytotoxic to most cells, it affects fibroblast production of proteoglycans, it has some RNase-activity, it interferes with the coagulation cascade etc. The activity of ECP is heterogeneous, since some purified protein species do not have cytotoxic activity. ECP is a genetically polymorph molecule and at one position an arginine is replaced by a threonine residue. The variant containing an arginine is the most common in the population, whereas the variant containing a threonine instead occurs in about 8% of a general population.
Sensitive immunoassays for ECP have been developed and commercialized. These assays are used in research to reflect the activity of eosinophils in vivo in health and disease. However, they are also widely used in the clinical setting in the diagnosis and monitoring of allergic disease, in particular asthma and food allergy. In this context it is important to appreciate the rigorous requirements as to sample handling of blood, since the measurement of ECP in serum is a measurement of the activity and size of the eosinophil population. Thus, the process of secretion of ECP goes on in the test tube until serum is separated from the blood cells. This, process is, as any biological, process time and temperature dependent, and falsely high levels may be obtained if this is not controlled for.
EPX is highly homologous to ECP and is a potent ribonuclease. Urine measurements of EPX is useful as a marker of eosinophil activity and involvement in various diseases.
Our current research on ECP and EPX is focused on the definition of the activity of the different molecular variants and understanding the biological role of this molecule in health and disease.
A role of the eosinophil in the defence against invading helminths and parasites has been suggested since many years. We showed in the late 70-tieth the cytotoxic activity of ECP towards the larvae of S. Mansoni. Our interest in these diseases has been revived recently, since we find intriguing associations between disease pathologies and ECP polymorphisms in populations endemically exposed to S. Mansoni.
In the upcoming projects we intend to study more closely the involvement of eosinophil and neutrophils in Leishmaniasis, Bilharzia, Malaria based on several preliminary findings of great interest.
Another project has been investigating the possible role of eosinophils in allergic disease such as asthma, rhinitis and otitis media with effusion, but also recently the role of eosinophils in inflammatory bowel disease and in patients with adverse reactions to food. The studies have employed the use of specific and sensitive immunoassays for eosinophil secretory proteins such as ECP, EPO and EPX and measured these molecules in blood, sputum, broncho-alveolar lavage fluid, urine and saliva, nasal lavage fluid, ear effusions. The presence of eosinophils in the processes of allergic disease has been quite obvious and also the relation of the activity of these cells to clinical signs and symptoms. The actual role, however, of the eosinophils in allergic disease is still somewhat enigmatic, although we have shown that the above molecules are potent biological molecules with the capacity to destroy epithelial cells and activate fibroblast to the increased production of tissue molecules.
In recent years we have studied the differences and similarities of allergic asthma and rhinitis vs non-allergic disease with respect to the inflammatory process and structural changes seen in the lungs and nose of such patients. These studies have revealed fundamental differences between allergic and non-allergic asthma and rhinitis. We have also shown the close association in our Scandinavian population between the development of allergic symptoms and one mutation in the coding part of the ECP gene.
By means of the mucosal patch technique we have demonstrated unexpected adverse reactions to food in the rectal mucosa when gluten or milk proteins have been introduced in the rectum. The results suggest that adverse reactions to food are very common and possibly underlying not only celiac disease, but also other chronic inflammatory disorders including irritable bowel syndrome. The technique opens up new possibilities to study these possible relationships.
Already in the late 70tieth we started our interest in constructing diagnostic tools for the diagnosis of acute myocardial damage and we developed a sensitive immunoassay to measure serum levels of myoglobin. We showed that this marker was superior in sensitivity in the detection of myocardial damage as compared to other biochemical markers used at that time. We also showed that it was the earliest marker of acute myocardial infarction and still more than 20 years later this is the case. The drawback of myoglobin was the lack of specificity. With the advent of new and specific markers of myocardial damage during the 90tieth i.e. the troponins the interest in the use of biochemical markers as diagnostic and prognostic tools has boosted and together with our cardiologists Bertil Lindahl and Lars Wallentin and their colleagues, we have shown troponin measurement in blood to be superior prognostic and diagnostic tools in patients with acute myocardial infarction and minor myocardial damage as is seen in unstable angina. Still, however, most assays of troponins, either T or I, lack the sensitivity in order to allow us to take full advantage of these tools. New tools under evaluation are natriuretic peptides, inflammation markers such as myeloperoxidase.
The current research interest is to find the best possible marker or combination of markers of myocardial damage for diagnostic and prognostic purposes. Another interest is therefore to assist the industry in the development of such tools.