Obtaining and Characterization of Experimental Diagnostic Brucellosis Rabbit Sera for the Development of a National Standard for Brucellosis Serum

Abstract

Relevance. The production of brucellosis diagnosticums is currently being established in the medical and veterinary practice of the Republic of Uzbekistan. However, due to the lack of a national standard serum in the country and the high cost of analog standard serums on the market, problems may arise in the production of diagnostic tools. In addition, the lack of national standard serums causes problems in quality control of commercial and local antigens, hinders the development of local drugs – brucellosis diagnostics, which reduces the effectiveness of serological diagnosis of brucellosis in humans and animals. Given the above, it becomes necessary to develop and produce a standard serum with a high level of safety, which will improve the methods of laboratory diagnosis of various forms of brucellosis in patients and animals to identify hidden foci of infection in Uzbekistan. The aim of the study is to obtain and characterize experimental standard diagnostic brucellosis rabbit sera for the development of national and industry standard serum with appropriate titers. Materials and Methods. The experiments were carried out in full compliance with the European Council Directive 2010/63/EU on compliance with ethical principles in working with laboratory animals and the experiments were carried out on the basis of the methodological manual «Methods and rules of work» approved by the Ministry of Health of the Republic of Uzbekistan in 2016 with laboratory animals in experimental microbiological and immunological studies. To obtain positive standard sera against brucellosis pathogens, 12 rabbits weighing from 2.2 kg to 4.6 kg, aged 6 to 12 months, were used. The animals were kept under identical conditions on a standard vivarium diet. For the experiment, animals adapted to the conditions of the study were selected and kept in quarantine for 21 days. The maintenance and conduct of the studies followed international rules for the humane treatment of animals. Results and Discussion. During the evaluation of the heterologic specificity of the obtained sera for 23 collection and hospital strains, a weakly positive response (+) was observed in 16.7% of cases. Rabbit sera positive for heterologic specificity were adsorbed on suspensions of inactivated microorganisms (Citrobacter spp. and Enterobacteriaceae spp.) - no significant drop in titer was observed, and cross-agglutination was eliminated. A significant increase in the total protein level was noted after the first and fourth immunizations. Before the first immunization, the total protein level was 59.57 g/l, and after the fourth immunization, it increased threefold to 157.17 g/l. There was also an increase in albumin and globulin (33.2 g/L and 26.37 g/L, respectively) to 79.37 g/L and 77.43 g/L, respectively. IgM levels remained almost unchanged, increasing 3.5-fold after the second immunization and decreasing to 0.24 mg/ml after the fourth immunization. An increase in the level of IgG after the second and third immunizations was revealed, followed by a decrease after the fourth immunization. Conclusion. The obtained national and industry standard diagnostic polyvalent brucellosis sera, as well as the developed methods of laboratory control of its quality and efficiency testing will make it possible to produce candidate standard serum samples for agglutination reaction test and detection of Brucella strains. The obtained standard serum samples will be further used for control of the produced immunobiological diagnostic preparations and provision of unified requirements to their quality. The goal was achieved – improving the serological diagnosis of brucellosis, laying the foundation for further study and standardization of serum.