Determination of Proteins in Bovinе and Avium PPD Tuberculin

Tuberculin skin test is one of the oldest and widely used in vivo methods for detection of Mycobacterium bovis infections in cattle and M. avium infections in birds and pigs. Tuberculins used for the test are purified protein derivatives (PPDs) containing a mixture of antigens - proteins, polypeptides, nucleic acids and polysaccharides. The specificity and activity of PPD depends mainly on the protein content.The aim of the development is to determine the amount of protein in Bulgaria produced dry and liquid PPDs from M. bovis and M. avium by determining the nitrogen content of the micro-Keldahl method. The process occurs in three stages - incineration, distillation and titration. Average losses of PPD tuberculins at various stages of production reached the highest values after sterile filtration, about 25-30%. At a dry substance concentration of 1 mg/ml, we obtained 0.98 mg/ml of protein, while in the non-filtered product the mean amount was 0.80 mg/ml. In a study of dry tuberculins, part of the samples were diluted in order to avoid foaming and to achieve complete burning. The protein losses were about 20%, which may be in the production process, tuberculin drying or in the analysis itself (pipetting, dilution of samples, etc.). Regardless of protein losses during the filtration of liquid unfiltered bovine and avian PPD tuberculins as well as the filtered end product, this process is necessary and of great importance for increasing the content of specific proteins, hence the antigenic activity of produced lots of PPD.