Developing platform for mRNA vaccines against cancer and infectious diseases

Abstract

mRNA vaccines are great alternatives to traditional vaccines as they are safe, highly potent and cost effective. In vitro transcribed mRNAs are an ideal biologically active agent which can be used as therapeutics in treatment of various disorders and as vaccines against infectious diseases and cancer. An optimized delivery system which gives efficient transfection with mRNA and is stable and non-toxic to the cells and organism, is the key to the success of mRNA application. In this study, we use DC- cholesterol (P-[N-(N’,N’-dimethyaminoaminoethane) carbomyl) and DOPE ( 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine) based liposomes to deliver mRNA in vitro and in vivo. These cationic liposomes formed by simple steps of film rehydration can successfully encapsulate mRNA and facilitate strong transfection in vitro of EGFP mRNA followed in vivo delivery of luciferase mRNA without any toxic effects. There was a prolonged production of EGFP and luciferase reporters, indicating that there is a long-lasting effect of local delivery. The most common use of mRNA as vaccines in cancer therapeutics is immunizing patients with mRNAs coding for tumour neo-antigens or TAAs (tumour associated antigens). mRNA vaccines for cancer can combine the efficacy, safety and potential of mRNAs to encode any proteins. Finally, the immunogenicity of antigens delivered by this complex was investigated by subcutaneous delivery of mRNAs encoding Staphylococcus aureus antigens AdsA and PmtA along with tumour model antigen OVA. To check the therapeutic efficiency of OVA mRNA-liposome complex, OVA mRNA was delivered subcutaneously and all the vaccinated mice survived with no or very small tumours. The efficacy of mRNA was also checked with other liposomes which were with a strong core or an adjuvant. And all the mRNA-liposome complexes gave a strong T cell response and were therapeutic enough to protect the mice from tumours. Furthermore, we found that the DC cholesterol-packed mRNA is suitable for local delivery. When the packed mRNA encoding EGFP is injected intra-tumour, strong localized expression was observed in tumour. So, we tried some intra-tumour delivery of some immune modulators like cytokines (IL-2, IFN-γ, GM_CSF and IL-15). These intra-tumour deliveries of cytokines lead to a regression in tumour sizes. This shows that mRNAs encoding immune modulators which could change the tumour micro-environment and activate the immune cells against the tumour. In summary, DC-cholesterol-DOPE cationic liposomes are safe and efficient in the delivery of mRNA and can be applied in the development of mRNA-based therapies which could lead to activation of both innate and humoral immune response. (Word count: 404)