Abstract
The common mould Aspergillus fumigatus is the major pathogen involved in the foetal and uterine infections of cows that result in abortion. The diagnosis is at present based on the identification of the fungus in aborted tissue and is unreliable. A reliable diagnostic technique that can provide early diagnosis is required and the possibility of developing such a test based on the detection of specific antibodies is examined in this thesis. The non-invasive diagnosis of Aspergillus fumigatus infections is difficult because of the lack of reliable antigenic markers and the major part of this investigation is concerned with the study of the antigenic profile of Aspergillus fumigatus. Isoelectric focusing and immuno blotting procedures were used to evaluate the protein and antigen spectra in culture filtrates from 6 strains of Aspergillus fumigatus and 9 strains of other fungi. The protein and antigen composition of culture filtrates was found to vary between different strains, different batches of culture from the same strain and during growth cycles of the test fungi. A system for the identification of different components was established and used to study the profiles of the different fungi. The protein and antigen profiles of Aspergillus fumigatus were compared to those from the other test fungi and an antigen with an isoelectric point of pH = 4.34 and a molecular weight of 39 kD was found to be typical for Aspergillus fumigatus in vitro. A preliminary N-terminal sequence (A??GYRSV?YFVNWA) was obtained. The antigen was tested against 108 cow sera including 20 sera from cattle with confirmed mycotic abortion, 11 sera from cattle with abortion of unknown reasons and 77 normal sera using indirect ELISA. In comparison to three different crude preparations the purified antigen was the best antigen to discriminate positive and normal sera (sensitivity = 75%, specificity = 88.6%, p< 0.0001). The antigen could therefore be a useful antigen to establish a reliable test system for Aspergillus fumigatus.