Effects of Lyophilization on Diagnostic Potential of <i>Brucella</i> Antigens

Abstract Brucella is the causative agent of brucellosis, a serious zoonotic bacterial illness that affects a variety of mammals worldwide. Brucellosis control and eradication programs mainly depend on effective and safe vaccination programs and accurate diagnostic tools. Animals are typically tested for bovine brucellosis using the complement fixation test (CFT), indirect ELISA (I-ELISA), and slide agglutination assays. The aim of the work is to produce freeze-dried slide agglutination antigens to be a strategic store for emergency outbreaks and to evaluate these antigens based on their diagnostic performance characteristics. In-house freeze-dried and liquid Rose Bengal antigens and freeze-dried and Liquid Buffered Acidified Plate Agglutination antigens were developed. I-ELISA with in-house produced antigen titrated and coated with smooth lipopolysaccharide was prepared and validated. The diagnostic performance parameters for each test were estimated using CFT as a gold standard test. The diagnostic performance characteristics for slide agglutination tests using different antigen preparations were estimated using CFT as a reference test. The study included 95 bovine sera tested for brucellosis. The Rose Bengal plate test was positive in 68 and 67 of sera by both LRB and FDRB, respectively. BAPA was positive in 72, 71, and 58 of sera when tested by LBAPA, FDBAPA, and I-ELISA respectively, while 48 sera were positive when confirmed by CFT. It was concluded that the newly prepared freeze-dried slide agglutination antigens were approximately as efficient as traditionally prepared antigens in terms of diagnostic performance items.