Introduction
Systemic loxoscelism, caused by the venom of the Loxosceles laeta spider, can be life-threatening. Current specific treatment relies on the administration of antivenom produced from the plasma of horses that have been hyperimmunized with spider venom. However, limited venom availability is the major production bottleneck. This study evaluates whether a genetically detoxified version of Sphingomyelinase D (SphD), the main toxin responsible for severe loxoscelism, could improve antivenom production.
Methods
Two versions of SphD were engineered using the baculovirus-insect larvae (BIL) platform: r(wtSphD), retaining its toxic functions, and r(dSphD), a detoxified variant (D259G mutation). Two horses were immunized over three cycles with r(dSphD), and their specific serum antibody responses were evaluated using an indirect ELISA. After each cycle, plasma was collected to produce pilot-scale Active Pharmaceutical Ingredients (APIs) of antivenom. Neutralizing activities of sera and APIs were tested against r(wtSphD) and native L. laeta venom using rabbit dermonecrotic assays and direct human red blood cell hemolysis test.
Results
A specific immune humoral response was developed after each immunization cycle. Higher levels of antibodies were detected in Horse 1. Dermonecrotic injuries of native L. laeta venom were partially neutralized by the sera and APIs from both animals. Moreover, sera and APIs from Horse 1 at cycles 2 and 3 effectively neutralized the r(wtSphD)´s dermonecrotic and hemolytic activities, while Horse 2 only showed similar neutralization capacity at cycle 3.
Conclusions
These promising results demonstrate that theBIL platform can be used to produce a genetically detoxified version of SphD, capable of inducing an immune-effective neutralization response of its homologous toxic form. Further ongoing research is being conducted to evaluate other detoxified versions of SphD isoforms and achieve complete protection against whole spider venom. This strategy offers a scalable, affordable, and safer alternative for venom complement or replacement in antivenom production.
