Page 114 - Avian Virology: Current Research and Future Trends

Avian Paramyxoviruses | 107

APMV-5 cell culture, it was observed that all four strains of APMV-6 repli-
APMV-5 (AMAvV-5) was first isolated in 1974 from an outbreak cated in a trypsin-independent manner in at least one of the cell
in budgerigars at Kunitachi, Japan (Nerome et al., 1978). APMV-5 types, but they required trypsin in one or more cell types. This
is unusual in that it lacks a virion haemagglutinin and does not suggests the existence of unexpected diversity in the ability of
grow in the allantoic cavity of embryonated chicken eggs. How- various cell lines to cleave different F proteins of an APMV (Xiao
ever, the virus grows in the amniotic cavity of embryonic chicken et al., 2010).
eggs and in various cell lines. To date, there are only four reports in Sequence comparison and cross-HI test results grouped the
the world on APMV-5 infections (Mustaffa-Babjee, 1974; Gough APMV-6 strains into two subgroups within a single serotype
et al., 1993; Yoshida et al., 1997; Hiono et al., 2016). The complete (Xiao et al., 2010). The strain from red-necked stint and the
genome sequences are available for two of the APMV-5 strains strain from Italy (IT4524-2) formed one group and the other
isolated in Japan (Samuel et al., 2010; Hiono et al., 2016). The strains formed the second group (Xiao et al., 2010; Karamendin
genome is 17,262 nt long and encodes six genes as other APMVs. et al., 2013). Recently, sequence analysis of the F gene of 11
The genome contains a 55-nt leader sequence at the 3′ end and APMV-6 isolates from wild ducks in Korea also showed exist-
a 552-nt trailer sequence at the 5′ end. The complete genome ence of two subgroups within APMV-6 (Choi et al., 2018).
sequence of TI strain shares 97% nt sequence identity with the Another recent study based on the mean inter-populational
Kunitachi strain (Hiono et al., 2016). The cleavage site of the F evolutionary distance of the F gene sequence of 24 isolates
protein (G-K-R-K-K-RF) conforms to the cleavage site motif from China also showed existence of two genotypes (I and II)
of the ubiquitous cellular protease furin. Consistent with this, within APMV-6 (Chen et al., 2018). A phylogenetic analysis of
exogenous protease is not required for virus replication in vitro. APMV-6 strains is shown in Fig. 3.13.
Infected of Vero cells by strain Kunitachi showed cell rounding
and detachment as well as syncytia formation. However, the ICPI APMV-7
value of the Kunitachi strain is 0.00, indicating that the virus is APMV-7 (AMAvV-7) was first isolated from a hunter-killed
avirulent for chickens, despite containing a multibasic F cleavage dove (Columba livia) in 1975 in Tennessee, USA (Alexander et
site. al., 1981). Since then APMV-7 viruses have been isolated mostly
from Columbiformes. Although an APMV-7 virus was isolated
APMV-6 from a natural outbreak of respiratory disease in commercial
APMV-6 (AMAvV-6) was first isolated from a domestic duck (A. turkey breeder flocks in Ohio in 1997, it has not been associated
platyrhynchos domesticus) in Hong Kong in 1977 (Shortridge et with severe disease in poultry (Saif et al., 1997). APMV-7 has also
al., 1980). Since then APMV-6 viruses have been isolated from been isolated from ostriches (Woolcock et al., 1996). Whether
a wide range of avian species, including ducks, geese, common or not the strains of APMV-7 isolated from different avian spe-
egrets and red-necked stint worldwide. To date, complete cies are the same has not been determined. The genome of the
genome sequences of eight strains of APMV-6 are available APMV-7 prototype strain dove/Tennessee/4/75 is 15,480 nt
(Chang et al., 2001; Xiao et al., 2010; Tian et al., 2012; Kara- and contains six genes (Xiao et al., 2009). The leader and trailer
mendin et al., 2013). APMV-6 is different from all other APMV regions are 55 and 127 nt, respectively. The 3′-leader contains a
45
serotypes in having an SH gene between the F and HN genes sequence ( AAUUAUUUUUU ) that is identical to the GE
35
(Chang et al., 2001; Xiao et al., 2010). The biological function signal present at two of the genes. The IGS ranges between 11 and
of APMV-6 SH gene is not known. However, the SH proteins 70 nt. The F protein has a single basic amino acid at the putative
of SV5 and mumps virus appear to play a role in blocking TNF- cleavage site (T-L-P-S-S-RF). The virus grows in only a few
alpha-mediated apoptosis pathway (Wilson et al., 2006). The established cell lines, indicating a restricted host range. APMV-7
SH protein of respiratory syncytial virus (RSV) has ion channel does not form syncytia or plaques in cell culture and its replica-
activity (Gan et al., 2008). RSV from which SH gene was deleted tion does not require exogenous protease. Sequence alignment
was fully viable in cell culture but was slightly attenuated in mice and phylogenetic analysis of the predicted amino acid sequence
and chimpanzees (Bukreyev et al., 1997; Whitehead et al., 1999). of APMV-7 proteins with the cognate proteins of the viruses of
APMV-6 strain duck/Hong Kong/18/199/1977 (Hong Kong) other members of subfamily Avulavirinae showed that APMV-7 is
is the prototype strain. more closely related to APMV-2, -5, -6, -8, -10, -14, -15, and -20
Six out of the eight available APMV-6 complete genome than to other APMV serotypes.
sequences, including strain Hong Kong, contain a genome of
16,236 nt. However, two sequences, one from a stint in Japan and APMV-8
the other from a duck in Italy, have 16,230 nt. The six-nucleotide APMV-8 (AMAvV-8) was first isolated from a Canadian goose
difference between the two viruses is due to a deletion in the non- (Branta canadensis) in 1976 in Delaware, USA (Cloud and
coding region of the F gene (Xiao et al., 2010). Rosenberger, 1980). Another APMV-8 strain was isolated from
In cell culture, APMV-6 induced cell rounding and detach- a feral pintail duck (A. acuta) in 1978 in Wakuya, Japan (Yamane
ment, and not syncytia formation (Xiao et al., 2010). The F et al., 1982). APMV-8 has not been isolated from domestic poul-
protein cleavage site of the Italian strain IT4524-2 has dibasic aa try. Determination of the first complete genome sequence of
(R-E-P-RL), compared with the monobasic F cleavage site of APMV-8 strain goose/Delaware/1053/76 (prototype strain) was
P-E-P-RL in other strains. Among four APMV-6 strains tested in independently published by two research groups (Mueller et al.,