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Molecular Pathogens
MP2011, Vol.2, No.1
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Figure 6 Amino acid sequence (78~153 aa) compared by 3A gene among O/YM/YN/2000 and other 9 strains
Note: The number represents the amino acid position; “•”: Indicated same amino acid;“
-
”: Indicate missed amino acid
prevent and control the FMD disease.
Phylogenetic comparisons of the whole genome and
VP1
gene showed that the O/YM/YN/2000 belongs to
the Cathay FMDV-O topotype. It was reported that
O/Taiwan/97 should be a representative strain for the
Cathay topotype virus, which only infected pigs
instead of cattle. Molecular characterization of this
topotype virus has been revealed that a 10
-
condon
deletion exists in the C-terminal half of the 3A protein
(Beard and Mason, 2000), this deletion usually occurs
in the earliest type O virus examined from the region
(from 1970) in this lineage (Feng et al., 2004; Knowles
et al., 2001). Studies on animals experimentally
infected with the O/YM/YN/2000 strain gave some
evidences that this isolate O/YM/YN/2000 has highly
virulent in pigs but lack of ability to cause disease in
bovines (unpublished data), these genetic and
phenotypic characteristic are quite similar to the
Cathay topotype virus with a 10
-
aa deletion in 3A
region (Figure 6). The alteration in 3A of the chicken
embryo-derived attenuated FMDV strains is important
for reducing virulence in cattle (Giraudo et al., 1990).
Our present results have confirmed that the changes in
3A protein of O/Taiwan/97 are associated with that
altered in vitro host range of FMDV (Beard and
Mason, 2000; Huang et al., 2001). In addition, Nunez
et al reported that a single amino acid substitution in
nonstructural protein 3A can mediate adaptation of
foot-and-mouth disease virus to the guinea pig (Núñez
et al., 2001). Therefore, it suggested that the role for
3A in virulence and host spectrum should interact with
3A variability and diversity .
The 5´
-
UTR of FMDV S fragment were known to
fold a stem-loop structure (Clarke et al., 1987), but its
function is not yet clear. The poliovirus, sharing the
same family of picornavirus with the FMDVs, its
5´
-
terminal of RNA fold into a cloverleaf RNA
structure, which has been shown to be involved in
genome replication and RNA stability, can produce the
interactions with the viral and cellular protein (Parsley
et al., 1997). Those results suggested that the S
segment of FMDV 5´
-
UTR might be involved in
genome replication and maintaining viral RNA
stability in the infected cells. Other speculated that the
virus S segment might affect pathogenicity of virus,
but there is no evidence to be confirmed. In the S
segment of O/YM/YN/2000, 5´
-
UTR 4
nt deletion
exists there (Figure 4A), but compared to reference
strains there are no deletion in the S segment. The 4
nt
deletion would be a specific feature of O/YM/YN/
2000, and the deletion might be associated with the
biological characteristics of strain, it would be worth
studying in future. In addition, Most FMDV strains
have four of PK structures, the 43
nt deletion located
in the region containing in PK structures of
O/YM/YN/2000 5´
-
UTR might cause the loss of PK
Ⅱ
domain (Figure 4B). This deletion presents in the
seven serotype of FMDVs, it is assumed that the
deletions in the PK regions are common in the
evolution of FMDV, and loss of one or two PKs has
been reported (Escarmis et al., 1995; Feng et al.,
2004). The function of PKs is still not clear, but it is
assumed that the PK structure, combining with the S
segment and the poly (C) tract, might play a role in
genome replication (Mason et al., 2003). Qian Fang et
al proposed that the loss of PK
Ⅱ
domain of
HKN/2002 might be involved the variation in the