The present disclosure relates to mRNA, self-replicating RNA, and temperature-sensitive, self-replicating RNA encoding a coronavirus nucleocapsid protein or an influenza virus nucleocapsid protein in operable combination with a mammalian signal peptide. The present disclosure relates to mRNA, self-replicating RNA, and temperature-sensitive, self-replicating RNA encoding other viral nucleocapsid protein(s) in operable combination with a mammalian signal peptide. The RNA constructs are suitable for active immunization against a virus in a mammalian subject, such as a human subject.

The invention relates to compositions and methods for the preparation, manufacture and therapeutic use of oncolytic defective virus compositions and methods of in vivo synthesis thereof. The composition includes a first nucleic acid construct encoding a self-amplifying mRNA (sa-mRNA) encoding at least one gene of interest (GOI) or a plurality of GOIs, a second nucleic acid construct encoding an mRNA encoding at least one virus structural protein, and at least one payload delivery system.

Genetically engineered alphavirus constructs (e.g., Mayaro virus) attenuated in normal human by increasing CpG dinucleotides frequency and its oncolytic potential against lung and pancreatic cancer. The modified virus may also be used as a live attenuated vaccine against MAYV.