Oral DNA Vaccination against SARS-COV2
Rapid and effective vaccine strategies are needed to combat emerging highly contagious pathogens, like SARS-CoV-2. DNA vaccines are a promising platform for promoting protective immunity against pathogen-specific target antigens encoded within plasmid DNA (pDNA). pDNA-based vaccines are applicable to a wide range of infectious diseases and can overcome some current vaccine production issues, including long production times and requirements for cold chain manufacturing, distribution, and storage. Although DNA vaccines have been investigated using a variety of administration routes and delivery vehicles, oral non-viral gene delivery offers a novel DNA vaccination strategy against coronaviruses and other pathogens. The non-invasive nature of oral gene delivery offers an administration route for DNA vaccination with the potential for high patient compliance, painless administration, and simple dosing. Additionally, recent research has reported that SARS-CoV-2 is capable of infecting intestinal epithelial cells, indicating the gastrointestinal (GI) tract may serve as an alternative route of infection and make oral DNA vaccination strategies relevant for vaccination against SARS-CoV-2. However, exploiting the benefits of orally delivered DNA vaccines is limited due to the harsh environment of the GI tract.
To overcome the challenges associated with oral DNA delivery, we are developing a novel, biological-based DNA vaccine oral delivery system by loading outer membrane vesicles (OMVs) derived from commensal gut bacteria with pDNA to create DNA-loaded OMV nanocarriers (DNA-OMV NCs). OMVs are produced via budding of bacterial outer membranes and function as a natural communication system for bacteria. Similar to mammalian exosomes, OMVs protect and deliver secreted material, thereby allowing bacteria to influence their environment, including mammalian cells. Numerous commensal (non-pathogenic) bacteria residing in the human GI tract produce OMVs, which act similarly to mammalian exosomes by protecting and trafficking DNA, RNA, protein and other small molecule cargo. OMVs retain their innate biological functions after oral administration to mice, indicating that OMVs can withstand GI transit. Additionally, OMVs can bind to and be internalized by intestinal epithelial cells, making OMVs a critical mediator of bacterial-host communication via a variety of signaling pathways. Together, these qualities indicate that OMVs could protect pDNA cargo in DNA-OMV NCs through GI transit and promote uptake of DNA-OMV NCs by intestinal cells for effective oral immunization against SARS-CoV-2 or other emerging pathogens.
Engineering Stem Cell Exosomes for Cell-Free Therapies
Exosomes are nanoscale extracellular vesicles that naturally deliver various biomolecules between cells within the body, and are involved in many (patho)physiological processes. Specifically, recent studies have shown that many therapeutic effects of mesenchymal stem cells (MSCs) are due to exosomes secreted by MSCs. Many of these therapeutic effects are associated with exosomal delivery of microRNAs (miRNAs), which are short non-coding RNAs that regulate gene expression by interacting with messenger RNAs. Because exosomes are natural delivery vehicles, are non-toxic, and have therapeutic effects, exosomes are under intense research as vehicles for gene therapies. Despite the potential of natural exosomes as therapeutics, high heterogeneity and low abundance of miRNAs in natural exosomes suggests that the therapeutic properties of exosomes could be potentiated by engineering increased loading of specific miRNAs. Therefore, the Pannier Lab has developed a transgenic system that induces cells to actively load high levels of a chosen miRNA into exosomes using cellular machinery. Current studies are investigating the ability of these engineered exosomes to target and deliver miRNAs to cells of interest, towards developing potential therapeutics for specific diseases.
Oral Gene Therapy for Inflammatory Bowel Diseases
According to the Crohn’s and Colitis Foundation, inflammatory bowel diseases (IBD) impact approximately 1.6 million Americans and nearly 70,000 new cases are diagnosed each year. IBDs, like Crohn’s disease (CD) and ulcerative colitis (UC), are typically treated first with corticosteroids and immunosuppressants. Biologics, antibodies designed to sequester inflammatory factors, have been used clinically in IBD patients as a more advanced treatment option and exhibit efficacy but have a limited treatment window due to the development of anti-drug antibodies that lead to clearance of the therapy after administration. Failure of medications to alleviate inflammation can require surgical resection of the colon or parts of the gastrointestinal tract (GI). Presently, there is no cure for IBD, and current treatments do not reliably achieve disease remission. Delivery of therapeutic genes directly to the site of disease by would improve and expand treatment options for patients and reduce the need for invasive surgery. Oral gene delivery is a desirable IBD therapy option due to the high rate of patient compliance, targeted delivery to the disease site, and large cellular surface area present for transfection. Despite the positive aspects of oral gene delivery, its success is limited due to harsh conditions within the gastrointestinal (GI) tract.
To overcome challenges associated with oral gene delivery, we are developing a novel, biological-based DNA oral gene therapy system by loading outer membrane vesicles (OMVs) derived from commensal gut bacteria with pDNA to create DNA-loaded OMV nanocarriers (DNA-OMV NCs). OMVs are produced via budding of bacterial outer membranes and function as a natural communication system for bacteria. Similar to mammalian exosomes, OMVs protect and deliver secreted material, thereby allowing bacteria to influence their environment, including mammalian cells. Numerous commensal (non-pathogenic) bacteria residing in the human GI tract produce OMVs, which act similarly to mammalian exosomes by protecting and trafficking DNA, RNA, protein and other small molecule cargo. OMVs are also capable of retaining their biological function after oral administration, indicating the ability to survive gastric transit and OMVs can be internalized by intestinal epithelial cells. In addition, depending upon the bacteria they are isolated from, OMVs can promote anti-inflammatory responses that could act synergistically with the pDNA cargo loaded in our DNA-OMV NCs to treat IBD. Thus, we propose utilizing DNA-OMV NCs for oral gene therapy will result in internalization of the DNA-OMV NCs through natural host-bacteria interactions, provide immunomodulatory properties to our system and protect to our pDNA cargo during GI transit leading to more effective long term treatment options for patients suffering from IBD and other intestinal conditions.