Described herein are RSV polynucleotide sequences that make use of multiple codons that are containing silent nucleotide substitutions engineered in multiple locations in the genome, wherein the substitutions introduce a numerous synonymous codons into the genome. Due to the large number of defects involved, the attenuated viruses disclosed herein provide a means of producing attenuated, live vaccines against RSV.

Reported herein are presumptively de-attenuating mutations that are useful, either individually or in combinations that may include other known mutations, in producing recombinant strains of human respiratory syncytial virus (RSV) exhibiting attenuation phenotypes. Also described herein is a novel RSV construct, Min_L-NPM2-1(N88K) L, which exhibits an attenuated phenotype, is stable and is as immunogenic as wild type RSV. The recombinant RSV strains described here are suitable for use as live-attenuated RSV vaccines. Exemplary vaccine candidates are described. Also provided are polynucleotide sequences capable of encoding the described viruses, as well as methods for producing and using the viruses.

The present disclosures relate to the establishment of a plasmid-based reverse genetic system for TiLV and use of the system to rescue recombinant and reporter TiLVs. The present disclosures also relate to the plasmids used for the rescue of TiLV and the recombinant and reporter TiLVs generated using the methods disclosed herein.