Pathogen-specific kinetics of oxidative burst in camel leukocytes: Influence of serum opsonization on reactive oxygen species production.

Background and Aim: Dromedary camels exhibit unique immune adaptations that enable survival in harsh environments with high microbial exposure. However, the cellular mechanisms underpinning their innate immune responses, particularly oxidative respiratory bursts, remain underexplored. This study aimed to investigate the kinetics of reactive oxygen species (ROS) production in camel leukocytes in response to selected bacterial and fungal pathogens and to assess the effect of serum opsonization on ROS generation. Materials and Methods: Whole blood from six clinically healthy female dromedary camels was stimulated with opsonized and non-opsonized Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae (three strains), and Candida albicans. Luminol-enhanced chemiluminescence (CL) assays were used to quantify ROS production over a 3-h period. Colony-forming units were evaluated to confirm microbial viability post-opsonization. Key ROS metrics included area under the curve, peak emission (relative light unit), and time to peak. Results: Camel neutrophils demonstrated distinct pathogen-specific ROS kinetics. P. aeruginosa and K. pneumoniae 1705 elicited the highest total ROS on serum opsonization, whereas S. aureus and C. albicans showed minimal ROS induction. E. coli failed to induce a measurable ROS response. Serum opsonization significantly enhanced total ROS production and shortened peak response time for K. pneumoniae strains. In contrast, it reduced total ROS output for S. aureus and C. albicans without significantly affecting their peak kinetics. Conclusion: This study provides the first comprehensive analysis of microbial-specific ROS production in camel whole blood using a luminol-based CL assay. The findings underscore the variability in camel innate immune responses to different pathogens and highlight the modulatory role of serum opsonization. These insights could inform future strategies in camel immunotherapy, vaccine development, and disease diagnostics.