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110 | Paldurai and Samal

that the virus is genetically related to APMV-10, -8, -2, and -20 in subgroups. The complete genome sequences have been deter-
the order of their genome nt identity values, 58.1, 56.7, 56.6, and mined for APMV-3 strains Netherlands and Wisconsin (Kumar
55.8%, respectively. The virus showed very low cross-reactivity et al., 2008, 2010b). The genome lengths differ slightly: strain
by HI test with APMV-8 and APMV-2 (Thomazelli et al., 2017). Netherlands is 16,272 nt compared with 16,182 nt for strain
The ICPI value of APMV strain RS-1177 is 0.00, indicating that Wisconsin. Both viruses have identical genome organization
the virus is avirulent to chickens. This virus represents species and highly conserved genome terminal sequences and GS and
AMAvV-15. GE sequences but substantial genome-wide nt and aa sequence
differences that are consistent with the two strains representing
APMV-20 distinct antigenic subgroups (Kumar et al., 2010b). The length of
Three novel APMVs were isolated from independent gull faecal trailer region of strain Netherlands is 707 nt compared with 681 nt
samples during 2014 AIV surveillance in Caspian seashore in for the trailer region of strain Wisconsin. The two APMV strains
Kazakhstan (Karamendin et al., 2017). This is the first report shared 67% nt identity and 78% aa identity. The envelope proteins
of isolation of an APMV serotype from gulls. It is not known (F and HN) are more divergent between the two strains. The F
whether this virus is restricted to gulls. The three viruses protein exhibited 70% aa identity and the HN protein has 73%
had no antigenic or genetic relationship to all other APMV aa identity. The F protein cleavage site of strain Wisconsin has
serotypes. The genome length of APMV-20 strain gull/Kazakh- two basic aa residues (R-P-S-G-RL) compared with three basic
stan/5976/2014 (Kazakhstan/5976) is 15,954 nt (refer updated aa residues (R-P-R-G-RL) of strain Netherlands (Kumar et al.,
GenBank sequence MF033136.2), which followed the ‘rule of 2010b). These results suggest that the APMV-3 strains represent a
six’. Sequence analysis showed that the three isolates were geneti- single serotype with two subgroups and these two subgroups vary
cally similar. The putative cleavage site sequence of the F protein antigenically, genetically and biologically.
of strain Kazakhstan/5976 is E-Q-Q-A-RL. The virus did not
replicate with or without exogenous protease in MDBK and APMV-4
DF-1 cells. The ICPI value of the virus is 0.00, indicating that it is APMV-4/duck/Hong Kong/D3/75 was the first APMV-4
avirulent to chickens. Infection of one-day-old and four-week-old (APAvV-4) strain isolated in Hong Kong from a duck (Shortridge
chickens did not show any signs of disease. All tested chickens and Alexander, 1978). Since then APMV-4 strains have been iso-
were negative for virus shedding by RT-PCR, indicating absence lated from a wide range of wild birds (mostly ducks and geese)
of virus infection (Karamendin et al., 2017). The APMV-20 is from many countries, including Hong Kong, Belgium, Germany,
genetically more closely related to APMV-2, -8, and -15 with the Israel, Japan, Great Britain, Korea, New Zealand and the United
genome nt identities of 56.8, 56.6, and 55.8%, respectively. This States (Gough and Alexander, 1984; Shihmanter et al., 1997; Stan-
virus represents species AMAvV-20. islawek et al., 2002; Jeon et al., 2008; Goekjian et al., 2011; Abolnik
et al., 2012; Yin et al., 2017). The first complete genome sequence
of APMV-4 was independently published by two research groups
APMVs from genus Paraavulavirus (Jeon et al., 2008; Nayak et al., 2008). To date, a total of eight full-
length and many partial APMV-4 genome sequences have been
APMV-3 reported (Jeon et al., 2008; Nayak et al., 2008, 2013; Rosseel et al.,
APMV-3 (APAvV-3) was first isolated from turkeys (Meleagris 2011; Abolnik et al., 2012; Wang et al., 2013; Tseren-Ochir et al.,
gallopavo) with respiratory disease in Ontario, Canada, in 1967 2017). The sequence analysis indicated that all APMV-4 viruses
and then in Wisconsin, USA, in 1968 (Tumova et al., 1979) and share a high level of identity. The genomes of APMV-4 strains
in England (Macpherson et al., 1983). The prototype APMV-3 from Hong Kong (prototype), Korea, Belgium, South Africa and
strain Netherlands was isolated from parakeets in the Nether- China are each 15,054 nt long (Jeon et al., 2008; Nayak et al.,
lands (Alexander and Chettle, 1978). Most isolations of APMV-3 2008, 2013; Rosseel et al., 2011; Abolnik et al., 2012; Wang et al.,
viruses have been from psittacine and passerine birds held in 2013; Tseren-Ochir et al., 2017). But the genome length of the
quarantine (Alexander, 1986). The APMV strains Wisconsin isolate from Delaware, United States is 15,048 nt (Parthiban et
and Netherlands differ in their virulence for chickens. APMV-3 al., 2013). It contains a 6-nt-shorter IGS between the F and HN
strain Wisconsin is avirulent for chickens, whereas APMV-3 genes. The genome of APMV-4 contains a 55-nt leader region at
strain Netherlands is moderately virulent for chickens. APMV-3 the 3′ end. The 5′ trailer region is 17 nt, which is the shortest in the
strains Netherlands and Wisconsin replicate in different cell family Paramyxoviridae. The 12-nt terminal regions at both ends
lines in presence or absence of 10% allantoic fluid. However, of the genome are complementary. APMV-4 is genetically more
inclusion of 10% allantoic fluid enhances the growth of the virus. closely related to APMV-3 than any other serotypes, based on full
The general CPE observed in all cell types involved rounding of genome sequence comparison (Nayak et al., 2013).
cells and detachment of dead cells. Syncytia formation, which The F protein cleavage site sequences of APMV-4 is
is the hallmark of many paramyxoviruses, is absent or limited to (D-I-P-Q-RF), which contains a single basic aa at –1 position.
small syncytia. APMV-3 strain Netherlands produces plaques This sequence is conserved in all APMV-4 strains. But unlike avir-
under methyl cellulose overlay. Antigenic analysis by recipro- ulent APMV-1 strains, APMV-4 replicates in vitro without added
cal cross-HI and cross-neutralization analysis showed that both protease and does not cause syncytia formation. Genome analysis
strains belong to a single serotype but represent two antigenic suggests that APMV-4 has possibly evolved into two lineages,