IMPROVING THE BIOLOGICAL STABILITY OF TUBERCULIN AND PROSPECTS FOR THE DEVELOPMENT OF NEXT-GENERATION DIFFERENTIAL DIAGNOSTICS

Abstract

This article discusses approaches to improving the biological stability of tuberculin preparations used for the allergic diagnosis of animal tuberculosis and outlines перспективes for the development of next-gene­ration differential diagnostic methods. The study focused on formalin-stabilized tuberculin, whose character­ristics were compared with those of conventional purified protein derivative (PPD) tuberculin preparations used in veterinary practice. Previous investigations evaluated the physicochemical, biological, and allergenic proper­ties of tuberculin produced from Mycobacterium bovis cultures using different concentrations of formalin as a stabilizing agent (0.1–10%). Among the tested formulations, a 3% formalin concentration demonstrated the most favorable balance between biological activity, storage stability, and the absence of local irritant reactions. Field clinical trials conducted in livestock farms of the Karaganda region (Kazakhstan) compared the formalin-stabilized tuberculin with two commercially available reference preparations: Mammalian PPD Tuberculin 1 (Kursk Biofactory, Russian Federation) and Mammalian PPD Tuberculin 2 (Republic of Kazakhstan). No false-positive reactions were observed in tuberculosis-free herds following administration of any of the tested pre­parations, confirming their high diagnostic specificity and biological safety. In herds affected by bovine tuber­culosis, however, the formalin-stabilized tuberculin produced more pronounced delayed-type hypersensitivity reactions, suggesting improved diagnostic sensitivity and enhanced detection of infected animals. As a promi­sing direction for further research, the development of next-generation differential diagnostic methods based on the ESAT-6 and CFP-10 antigens encoded by genes within the RD1 region has been proposed. The use of these antigens will enable the implementation of the DIVA approach (Differentiating Infected from Vaccina­ted Animals), allowing infected animals to be differentiated from those vaccinated with BCG, which is of considerable interest for improving animal tuberculosis control and eradication programs.