Importantly, we also verified the genetic stability of our engineered stop codon and mutated start codon in the original rev reading frame by sequencing proviral DNA from day 10 infections of all three viruses (8-GRev_IRES_Nef, 9-GRev_IRES_Nef, and NLRev_IRES_Nef). This evidence concerns the gene S100B and infection.