MRC-5Genomic evaluation of 5’-UTR sequence of fusion gene in vaccine strain of measles virus (AIK-C) following passage in MRC-5 cell line

Background: Multiple point mutations and deletions have been detected in the 5’-UTR non-coding region of F gene of measles virus vaccine strains that may affect the function of fusion protein and viral penetration. Objective: To study the possible alterations in 5’-UTR non-coding sequence of F gene following a change in measles virus cell culture from chicken fibroblast to MRC-5 cell line. Methods: Concerning the importance of F gene in immunogenicity and the cellular tropism of this protein, the present study was performed at the Biotechnology Department of Razi Vaccine & Serum Research Institute, Karaj, Iran. After cloning of 5’-UTR non-coding sequence of F gene and amplification using a two-step RT-PCR method, the recombinant plasmid was sequenced. Comparing this F gene 5’-UTR sequence with standard vaccine strains by DNAMAN program, the possible changes which might have been occurred in F gene non-coding sequence, was determined. Findings: Comparing the F gene 5’-UTR sequence of AIK-C vaccine strain with two sequences of Parks and Mori vaccine strains was indicative of two nucleotide variations in bases 156 and 288 after shifting the measles virus vaccine strain cell lines from chicken fibroblast to MRC-5. Conclusion: Regarding the changes in two nucleotides of F gene 5’-UTR non-coding sequence after cell culture shift from fibroblast to MRC-5 cell line for multiplication of measles virus vaccine strain, these alterations may affect the selection of AUG initiation codon, promote the translational level of fusion protein, and therefore leading to possible reduction in immunogenicity of this newly propagated virus vaccine strain.