Genetic characterization of RS-12 (S-12), an Iranian isolate of mumps virus, by sequence analysis and comparative genomics of F, SH, and HN genes.

RS-12 mumps virus strain was isolated in 1986, in monkey kidney cells, from the throat-washing of an Iranian patient and developed to RS-12 vaccine by serial passage of the pathogen in MRC-5 cells. During the present study, an early passage RS-12 containing its virulent pathogenic phenotype, was characterized genetically. Its F, SH and HN genes were isolated by RT-PCR amplification and sequenced. It is quite evident that RS-12 belongs to genotype H, closely related to European strains but distinguishable from Asian strains. The deduced amino acid sequences of HN and F proteins that comprise immunogenic epitopes, were compared to other vaccine and wild strains. The multiple sequence alignment revealed that the RS-12 has isoleucine and aspartic acid at positions 269 and 523 of its F and HN proteins, respectively, which could differentiate RS-12 from other available sequences. This isolate has trivial variations in the major antigenic sites of HN protein. The frequency and pattern of F and HN glycosylation sites seems to be similar to most other strains. It seems that the mumps regional outbreak during 1986 in Iran was caused by genotype H and this strain has been spreading in countries surrounding the Caspian sea for over 17 years. These data support the previous results that RS-12 could be an efficient vaccine, especially in the Middle East. This is the first genotype report from Iranian isolates and provides strong data on the molecular epidemiology of mumps in Iran, the Middle East, Central Asia, Russia and other countries of this region.