Development of a recombinant MOMP-based indirect ELISA for the serodiagnosis of caprine chlamydiasis

Caprine chlamydiasis, caused primarily by Chlamydia abortus, is a major cause of infectious abortion in small ruminants worldwide, leading to substantial economic losses and posing a zoonotic risk; thus, timely diagnosis is essential. The C. abortus ompA gene was cloned into the pLATE vector and expressed in Escherichia coli. Recombinant MOMP (rMOMP) was purified by affinity chromatography and evaluated as a diagnostic antigen using 82 caprine serum samples in comparison with a commercial kit. Method robustness, precision, and sample stability (freeze-thaw cycles and thermal stress) were assessed in accordance with international validation guidelines. The CA-iELISA demonstrated solid diagnostic performance, achieving an Area Under the Curve (AUC) of 0.965, a sensitivity of 91.4%, and a specificity of 89.4% relative to the commercial kit. The assay showed high repeatability (11.13% CV) and intermediate precision (17.91% CV), both well within the 20% acceptance threshold. Robustness testing indicated thermal stability but identified incubation time as a critical control parameter. Sample stability studies confirmed that serum remains reliable for up to 7 days under refrigeration (4 °C); however, aliquoting is strongly recommended to prevent the signal loss (~ 40%) observed after a single freeze-thaw cycle. The rMOMP-based CA-iELISA represents a viable candidate diagnostic assay, serving as a robust and sensitive tool for the serological screening of caprine chlamydiasis. This positions it as a potential primary epidemiological screening tool for disease surveillance and control programs in goats, particularly in resource-limited regions lacking specialized diagnostic infrastructure.