Development of a single-chain variable fragment (scFv)-conjugated affinity silk filter for the efficient removal of Ichthyophthirius multifiliis

Ichthyophthirius multifiliis (I. multifiliis) is known to infect a wide range of freshwater teleosts worldwide and elicit white spot disease (WSD). Since WSD causes serious economic loss in global aquaculture, effective means of controlling WSD are urgently needed. In this current study, we have tried to develop the pilot model of an aquarium filter that can effectively filter out the endoparasite I. multifiliis using “anti- I. multifiliis affinity silk”. This affinity silk consists of the silk fibroin L-chain (FibL) and the single-chain variable fragment (scFv) from the anti- I. multifiliis monoclonal antibody (mAb). This affinity silk-coated glass wool was inserted into a 5 mL syringe, which was used to filter the aquarium water with I. multifiliis. The filter was washed twice after the filtration, and the number of parasites in the filtrate was calculated each time. To evaluate the number of parasites captured by the filter, the number of parasites in the first filtrate and the washes were compared with the number of parasites passed through the filter initially. The number of I. multifiliis captured by the glass wool filter coated with anti- I. multifiliis affinity silk was significantly higher than the control filters, indicating that the filter is effective against highly motile and large microorganism. These results show that anti- I. multifiliis affinity silk can be a great tool for preventing ichthyophthiriasis, the parasitic disease caused by I. multifiliis.