| Abstract |
Q fever is a prevalent worldwide zoonosis, and has various acute and chronic clinical manifestations. Coxiella burnetii has been identified in a wide range of wild and domestic animals, including arthropods, birds, rodents, carnivores, ungulates and livestock. Acute Q fever is mostly a self-limiting, mild, influenza-like disease, sometimes complicated by severe pneumonia or hepatitis. A proportion of the patients infected by C. burnetii, will progress to persistent focalized Cοχiella burnetii infection after primary infection. Chronic Q fever leads to high death rates if left untreated, which makes early case-finding and preventive measures critical for patients at high risk. Q fever has a high socioeconomic burden that presents significant challenges for both public and animal health. During the past 25 years, 32 outbreaks in Europe have been identified, indicating that the number of Q fever cases is constantly increasing. Q fever has become a serious public health problem in many areas not previously known as endemic zones and represents a major health risk for humans and animals. The economic and public health importance of the disease was recently underscored following the largest ever reported outbreak, which occurred from 2007 up to 2011 in the Netherlands.
Concerning the timely diagnosis of chronic Q fever, a diagnostic problem exists since the current gold standard method for the diagnosis, immunofluorescence, has several disadvantages, such as the difference in sensitivity and specificity among commercial diagnostic kits, the objectivity of the interpretation of the results, potential antibody cross-reactions, etc.
In the present study we searched several proteins from C. burnetii for their ability to differential diagnose acute or chronic Q fever in human blood serum. As a first step, 16 different proteins were chosen, according to literature for their antigenic properties. In addition, three proteins from Coxiella’s Type IV secretion system (IcmG, IcmK and DotC) were chosen in order to be tested, since this nanomachine is important for the infection and pathogensis of Coxiella. By employing DNA cloning techniques, construction of different plasmids took place. Afterwards, proteins expression was tested in different conditions (culture temperature, IPTG concentration, time of culture after induction). When the proteins of interest were best
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expressed, they were isolated and purified. The proteins were then used for the screening of sera from patients suffering from chronic Q fever endocarditis, patients whose samples were negative for phase I IgG, patients whose at least one sample was positive for phase I IgG and patients suffering from any kind of rheumatoid disease. Blood donors were used as the control group. Statistics were used to calculate sensitivity, specificity, positive predictive value, negative predictive value and Cohen’s kappa coefficient (κ) and logistic regression binary analysis was also performed in order to find any possible combinations of proteins that could act as better diagnostic factors.
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