Paramyxovirus immunogens and related materials and methods

A recombinant paramyxovirus composition comprising a nucleic acid molecule which encodes large RNA polymerase (L) protein having a defective mRNA cap MTase domain in a paramyxovirus viral genome, wherein the paramyxovirus viral genome is human respiratory syncytial virus (hRSV);

• and,
• wherein the nucleic acid molecule which encodes large RNA polymerase (L) protein having a defective mRNA cap MTase domain carries at least one mutation in a S-adenosyl methionine (SAM) binding site;
• wherein the at least one mutation in the SAM binding site is in a G×G×G . . . D/E/W site in an amino acid sequence corresponding to amino acid positions 31-90 of SEQ ID NO:
• 3, wherein the mutations comprise:
• at position 31, A×G×G . . . D;
• at position 33, G×A×G . . . D;
• at position 35, G×G×A . . . D;
• and,
• at position 90, G×G×G . . . A.