ROS (reactive oxygen species) are produced at mucosal epithelial surfaces, as part of the innate immune response to combat invading pathogens. The proteins responsible for this ROS production belong to the NOX/DUOX (NADPH Oxidase and Dual Oxidase) family and include C. elegans Ce-Duox1/BLI-3. It was previously shown that in response to infection with Enterococcus faecalis, BLI-3 released ROS, and reduction of
bli-3 expression caused the worms to be significantly more susceptible. Additionally, DUOXs are known to generate ROS for use by peroxidases, which then generate more potent oxidation products that aid in the host's innate immune response. An example is human lactoperoxidase (hLPO), which uses ROS from hDUOX2 to produce hypothiocyanite to facilitate clearance in the airway epithelia. Based on this information, we hypothesized that BLI-3-generated ROS may act as a substrate for peroxidases to generate antimicrobial agents in the C. elegans immune response. Using
bli-3 as the query, WormBase.org was searched for homologous genes. The genes-of-interest were screened for a susceptibility-to-pathogen phenotype in C. elegans using RNAi (RNA interference) to reduce their expression. Genes necessary for full resistance against pathogen were further tested for general fitness defects using longevity assays. F49E12.1 RNAi worms incubated with E. faecalis at 25 deg C displayed an increased susceptibility phenotype (P-value = 0.0011; median survival: 189 and 165 hours, V.C. and F49E12.1, respectively). As determined by Amplex Red, when infected, F49E12.1 RNAi worms display increased H2O2 levels relative to vector control (P-value = 0.0068) which suggests F49E12.1 utilizes H2O2 for a, currently, unknown purpose. Interestingly, F49E12.1 possesses significant homology to peroxidases that are crucial for innate immunity in crustaceans as well as mammals. Therefore, the current focus is to elucidate how the putative peroxidase F49E12.1 contributes to the C. elegans innate immune response.