Synthetic alphavirus-derived replicon expression systems comprising nucleic acid sequences encoding at least one modified nonstructural protein, and synthetic nucleic acid sequences encoding at least one heterologous protein are described. Methods of producing at least one heterologous protein in a cell, or of inducing an immune response in a subject by administering and/or expressing the synthetic alphavirus-derived replicon expression systems are provided.

The disclosure is directed to an isolated polynucleotide encoding a modified picornavirus 3C protease, wherein the modified picornavirus 3C protease includes an altered secondary structure and one or more amino acid substitution(s) located at one or more amino acid position(s) corresponding to positions 16-25, 99-100 and 115-130 of a wild-type Fool-and-Mouth Disease Virus (FMDV) 3C protease, wherein the isolated polynucleotide encoding the modified picornavirus 3C protease, when transformed into and co-expressed in a host cell, enhances transgene expression of a P1 precursor polypeptide in comparison to an amount of P1 precursor polypeptide transgene expression exhibited in a host cell transformed and co-expressed with a control picornavirus 3C protease, wherein the one or more corresponding amino acid position(s) is/are identified by an alignment of the modified picornavirus 3C protease with the one or more of the wild type FMDV 3C protease(s). Methods for processing a picornavirus P1 precursor polypeptide into picornavirus viral proteins and/or virus-like particles using the isolated polynucleotides are also provided.

Synthetic alphavirus-derived replicon expression systems comprising nucleic acid sequences encoding at least one modified nonstructural protein, and synthetic nucleic acid sequences encoding at least one heterologous protein are described. Methods of producing at least one heterologous protein in a cell, or of inducing an immune response in a subject by administering and/or expressing the synthetic alphavirus-derived replicon expression systems are provided.

Synthetic alphavirus-derived replicon expression systems comprising nucleic acid sequences encoding at least one modified nonstructural protein, and synthetic nucleic acid sequences encoding at least one heterologous protein are described. Methods of producing at least one heterologous protein in a cell, or of inducing an immune response in a subject by administering and/or expressing the synthetic alphavirus-derived replicon expression systems are provided.

This application is directed generally to foot-and-mouth disease virus (FMDV) 3C proteases that have been modified by mutating a polynucleotide sequence coding for the FMDV 3C protease. The modified FMDV proteases exhibit proteolytic activity on FMDV P1 precursor protein and exhibit a reduction in one or more toxic or inhibitory properties associated with an unmodified FMDV 3C protease on a host cell used to recombinantly produce it. Vectors carrying polynucleotides encoding modified FMDV 3C protease sequences can induce production of FMDV virus-like particles in a host cell when expressed in the host cell. The modified FMDV 3C proteases can generally be used to produce immunogenic FMDV preparations capable of inducing an immune response against FMDV.

This application is directed generally to foot-and-mouth disease virus (FMDV) 3C proteases that have been modified by mutating a polynucleotide sequence coding for the FMDV 3C protease. The modified FMDV proteases exhibit proteolytic activity on FMDV P1 precursor protein and exhibit a reduction in one or more toxic or inhibitory properties associated with an unmodified FMDV 3C protease on a host cell used to recombinantly produce it. Vectors carrying polynucleotides encoding modified FMDV 3C protease sequences can induce production of FMDV virus-like particles in a host cell when expressed in the host cell. The modified FMDV 3C proteases can generally be used to produce immunogenic FMDV preparations capable of inducing an immune response against FMDV.

This application is directed generally to foot-and-mouth disease virus (FMDV) 3C proteases that have been modified by mutating a polynucleotide sequence coding for the FMDV 3C protease. The modified FMDV proteases exhibit proteolytic activity on FMDV P1 precursor protein and exhibit a reduction in one or more toxic or inhibitory properties associated with an unmodified FMDV 3C protease on a host cell used to recombinantly produce it. Vectors carrying polynucleotides encoding modified FMDV 3C protease sequences can induce production of FMDV virus-like particles in a host cell when expressed in the host cell. The modified FMDV 3C proteases can generally be used to produce immunogenic FMDV preparations capable of inducing an immune response against FMDV.

Methods and compositions for increasing the production of large amounts of empty capsids of the foot-and-mouth disease virus (FMDV) in a stable manner in mammalian cells by regulating the expression of FMDV 3C protease. The instant methods and compositions are based on the fact that a decreased expression of 3C protease results in a reduced cell toxicity and an increased synthesis of viral capsid proteins, as well as production of recombinant empty capsids. The invention provides recombinant plasmids that direct the expression of P1, 3C, and the use of the plasmids for producing new stable cell lines capable of generating high titers of FMDV empty capsids. The invention provides methods for regulating the expression of the FMDV 3C protease gene at a transcriptional and translational level in order to achieve the required process level of 3C protease for the selection process, as well as the production process.

Aspects of the disclosure relate to compositions of messenger RNA vaccines and methods of administration thereof. Compositions provided herein include one or more RNA polynucleotides having an open reading frame encoding a picornavirus capsid polyprotein and a protease. Compositions provided herein include one or more RNA polynucleotides having an open reading frame encoding an active product that modulates the expression, structure or function of at least one other RNA or product thereof.

The disclosure is directed to an isolated polynucleotide encoding a modified picornavirus 3C protease, wherein the modified picornavirus 3C protease includes an altered secondary structure and one or more amino acid substitution(s) located at one or more amino acid position(s) corresponding to positions 16-25, 99-100 and 115-130 of a wild-type Fool-and-Mouth Disease Virus (FMDV) 3C protease, wherein the isolated polynucleotide encoding the modified picornavirus 3C protease, when transformed into and co-expressed in a host cell, enhances transgene expression of a P1 precursor polypeptide in comparison to an amount of P1 precursor polypeptide transgene expression exhibited in a host cell transformed and co-expressed with a control picornavirus 3C protease, wherein the one or more corresponding amino acid position(s) is/are identified by an alignment of the modified picornavirus 3C protease with the one or more of the wild type FMDV 3C protease(s). Methods for processing a picornavirus P1 precursor polypeptide into picornavirus viral proteins and/or virus-like particles using the isolated polynucleotides are also provided.