Joseph Salceda

Project: Assessing Split Intein Splicing Efficiency for Use in Oral Vaccines

Research Group: Mills Research Group

Graduate Mentor: Jenna Wolfanger

Abstract: The need for low-temperature storage throughout the immunization supply chain limits access to life-saving vaccines worldwide. Shelf-stable oral vaccines are a promising candidate for addressing this issue. We proposed a new oral vaccine platform, consisting of a pill containing a probiotic bacteria that produces the vaccine inside the patient’s gut. Since the bacteria only produce the vaccine after ingestion, this design circumvents typical refrigeration requirements. One of our goals is to make this vaccine platform modular, allowing for easy development of new vaccines without redesigning the system from scratch. Our modular system centers around a virus-like particle and antigens attached to its surface via split inteins, which act like biological velcro. However, we observed that these inteins exhibit low splicing efficiency in our experiments. Based on the literature, we believe this is due to intein aggregation resulting in low solubility. We hypothesize that improving solubility of the C-half will improve intein splicing. Historically, a Small Ubiquitin-like Modifier (SUMO) tag has been used to improve intein expression and solubility, so we attached a SUMO tag to the C-half of our inteins and reassessed their splicing. To conduct this experiment, we quantified splicing efficiency using a split fluorescent reporter attached to each intein half that will only fluoresce if splicing occurs. Our results indicate that the SUMO tag increases fluorescence from less than 1% to 55% of maximum fluorescence possible by the reporter. These results support our hypothesis and advance the development of our modular oral vaccine platform.