Evaluation of a chimeric recombinant protein (Spo1) for the serological diagnosis of feline sporotrichosis on ELISA platform

Introduction: Feline sporotrichosis is a zoonotic public health concern in Brazil.Caused by the Sporothrix species complex, the disease is primarily transmitted through scratches and bites from infected cats, which serve as urban reservoirs.Diagnosis remains challenging due to the reliance on slow or variable-sensitivity methods such as fungal culture and cytology, along with the lack of widely available serological tests, making effective screening and control difficult.The development of serological methods, such as ELISA, could provide more accessible, rapid, and epidemiological surveillance.Establishing reliable diagnostic tools is crucial for controlling the spread of feline sporotrichosis and mitigating its impact on both animal and human health.Objectives: This study aimed to evaluate the diagnostic potential of a chimeric recombinant protein (Spo1) using the ELISA platform.Methodology: The Spo1 protein was tested at two concentrations (400 ng and 600 ng) in a 96-well plate, along with the protein A peroxidase conjugate at 1:2000 up to 1:40,000 dilutions.Standardization was performed using three positive and four negative samples in duplicate, followed by evaluation with feline samples positive (n = 14) and negative (n = 10) for sporotrichosis, as well as a panel of feline samples with toxoplasmosis (n = 8).Results: As the first results, it was possible to verify the concentration of 600 ng of protein with the combination of conjugate 1:15,000 protein A. The results of the optical density (OD) of the samples showed that the Spo1 protein has the potential to discriminate well the positive samples (mean of 0,476) from the negative samples (mean of 0,067).After standardization, an ELISA was performed with a panel of feline samples.As the main result, it was understood that the Spo1 protein could react with 72% sensitivity and 82% specificity with a reduced panel. Conclusion:Regarding the toxoplasmosis samples, no cross-reactivity was observed.It is worth noting that all samples considered positive were reactive in fungal culture and not by serological tests, as well as negative samples, so it is necessary to expand the studies with more characterized panels for this study with the recombinant protein Spo1.