Phylogenetic and molecular analysis of hemagglutinin gene and Fsp-coding region of canine distemper virus: Insight into novel vaccine development.

Canine distemper virus (CDV) causes a highly contagious and lethal disease in a vast range of carnivorous and non-carnivorous species. The study aimed to genetically investigate the hemagglutinin (H) gene and Fsp-coding region of CDV isolates from vaccinated dogs. Phylogenetic analysis of the H gene and Fsp-coding region showed that our viruses belonged to the Arctic-like lineage which was distinct from two commonly used vaccine strains (America-1 lineage strains) in Iran. Our data presented a high similarity between the H gene sequences of studied viruses. The multiple sequence alignment of the H gene of our viruses against vaccine strains revealed 91.3-95.6 % and 89.9-94.4 % in the level of nucleotide and amino acid identity, respectively. Our finding identified a potential recombination breakpoint occurring between codons 520-607, along with three positive selection sites including residues 415,547, and 549 among the H gene using the Data Monkey platform. A significant variation of B cell epitopes was found in Hemagglutinating and noose epitope (HNE), with respect to America-1 vaccine strains. Moreover, the H genes of studied viruses had 8 N-glycosylation sites, which is more than the America-1 vaccine strains. Our results confirmed that the circulation of Arctic-like lineage may be a prevalent lineage. Despite widespread vaccination, it does not provide full protection against CDV infection. Due to antigenic differences between our viruses and commonly used vaccine strains, it seems a novel vaccine strain is needed to prevent and prepare full protection against Arctic-like CDV infection.