To establish an indirect ELISA method for the detection of human brucellosis based on signal peptide-truncated recombinant Cu/Zn SOD and its preliminary clinical verification.

Authors

Chao Wei, Chanjuan Zhang, Meiling Ren, Kaiting Zhang, Huanhuan Yang, Ruiyan Han, Zixuan Dong, Songsong Xie

Published in

Frontiers in cellular and infection microbiology. Volume 16. Pages 1933037. Epub Sep 08, 2026.

Abstract

Serological diagnosis of brucellosis is hindered by cross-reactivity with lipopolysaccharide (LPS) antigens, resulting in insufficient specificity and sensitivity, which remains one of the major bottlenecks in current clinical testing for brucellosis.
To overcome this limitation, we developed an indirect ELISA based on recombinant Cu/Zn superoxide dismutase (rSOD) from Brucella. The N-terminal signal peptide of rSOD was truncated and expressed as a soluble His-tagged protein in Escherichia coli BL21 (DE3) through codon optimization. After purification, detection parameters were optimized using checkerboard titration, and the cutoff value was established using 40 sera from healthy blood donors (mean + 3SD). We evaluated the assay's performance against LPS-ELISA using 106 clinical samples (63 from brucellosis patients and 43 from healthy controls), assessing reproducibility, cross-reactivity with endemic infections (tuberculosis, rickettsiosis, and echinococcosis), and diagnostic accuracy.
Optimal conditions were determined as 1.25 μg/mL antigen concentration, serum dilution of 1:800, and a cutoff OD₄₅₀ of 0.386. Intra-batch and inter-batch coefficients of variation ranged from 0.93% to 4.60% and 1.09% to 12.88%, respectively. Cross-reactivity rates were 15% for tuberculosis, 5% for rickettsiosis, and 0% for echinococcosis. In clinical testing, the rSOD-ELISA demonstrated a sensitivity of 82.5% (52/63, 95% CI 71.4%-89.9%) and a specificity of 90.7% (39/43, 95% CI 78.4%-96.3%), with a false positive rate of 9.3%. Compared with LPS-ELISA, it showed comparable sensitivity (82.5% vs. 80.9%), higher specificity (90.7% vs. 83.7%), a lower false positive rate (9.3% vs. 16.3%), and an overall agreement of 96.2% (Kappa = 0.92, P < 0.001).
The rSOD-ELISA demonstrates superior diagnostic performance through higher specificity and a lower false positive rate compared with conventional LPS-based tests. Although further validation through larger multicenter studies is needed, it represents a promising supplementary serological tool for brucellosis screening in areas with multiple concurrent pathogens.

PMID:
42774021
Bibliographic data and abstract were imported from PubMed on 23 Sep 2026.

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