Discussion
The phylogenetic analysis shows that camel and human MERS-CoVs are
clustered together. The human-camel MERS-CoV cluster is further divided
into two clades, i.e. clade A and clade B. The earliest cases of MERS
including EMC/2012 and Jordan-N3/2012 belong to clade A clusters, and
all other cases from 2012-2015 are in clade B (7, 8). Being distinct
from phylogenetic analysis, which is biasedly based on the coding
sequence, characterization of conserved pyrimidine nucleotide in the
non-coding 5’-UTR of MERS-CoV may represent another possible mechanism
in virus adaptive evolution since the conserved nucleotide sequence and
structure of 5’-UTR directly interact with the host cellular factors
during virus replication to regulate transcription, translation, and
genomic RNA synthesis. A total of 10 complete genomes of MERS-CoV were
reported in 2012 and classified into 2 clades (clade A and clade B) in
phylogenetic analysis (7). However, all of them are the U—-U
type virus according to the conserved pyrimidine nucleotide in 5’-UTR.
Thus, the conserved pyrimidine nucleotides in 5’-UTR can serve as a
novel genetic signature in evolution of MERS-CoV.
There are no specifically effective therapeutics and vaccines for MERS.
In general, surveillance for MERS-CoV in humans and camels in affected
countries is still a priority for infection control. In addition to the
coding sequence, the variations in non-coding region, particularly in
the conserved stem-loop region of 5’-UTR can offer novel implication in
epidemiology. Its importance needs an attention without contempt in both
tracing the chain of infection transmission and algorithm of
phylogenetic analysis.