An evolutionary insight into Newcastle disease viruses isolated
Received: 9 December 2014 / Accepted: 17 April 2015 / Published online: 27 May 2015
Ó Springer-Verlag Wien 2015
Abstract The disease caused by Newcastle disease virus
(NDV) is a severe threat to the poultry industry worldwide.
Recently, NDV has been isolated in the Antarctic region.
Detailed studies on the mode of evolution of NDV strains
isolated worldwide are relevant for our understanding of
the evolutionary history of NDV. For this reason, we have
performed Bayesian coalescent analysis of NDV strains
isolated in Antarctica to study evolutionary rates, popula-
tion dynamics, and patterns of evolution. Analysis of F
protein cleavage-site sequences of NDV isolates from
Antarctica suggested that these strains are lentogenic.
Strains isolated in Antarctica and genotype I reference
strain Ulster/67 diverged from ancestors that existed
around 1958. The time of the most recent common ancestor
(MRCA) was established to be around 1883 for all class II
viruses. A mean rate of evolution of 1.78 9 10
tutions per site per year (s/s/y) was obtained for the F gene
sequences of NDV strains examined in this study.
A Bayesian skyline plot indicated a decline in NDV
population size in the last 25 years. The results are dis-
cussed in terms of the possible role of Antarctica in
emerging or re-emerging viruses and the evolution of NDV
The disease caused by Newcastle disease virus (NDV) is one
the most important diseases of poultry, affecting the poultry
industry worldwide . NDV belongs to the genus Avulavirus
of the family Paramyxoviridae, and its genome is a non-seg-
mented, single-stranded, negative-sense RNA molecule of
approximately 15,186 nucleotides (nt) in length .
NDV isolates have been grouped by virulence pheno-
type, with lentogenic, mesogenic, and velogenic strains, in
order of increasing virulence . Lentogenic viruses
typically cause subclinical infections or mild respiratory
disease. Mesogens are of intermediate virulence, usually
resulting in moderate respiratory disease with occasional
nervous signs. Velogens are the most virulent viruses and
may cause extensive hemorrhagic lesions, particularly in
the gastrointestinal tract (viscerotropic), and/or a pre-
dominance of nervous signs (neurotropic) .
NDV infection is initiated by the action of two envelope
glycoproteins. One of these mediates attachment of the
virus to a host-cell receptor and is designated HN
(hemagglutinin-neuraminidase). The other glycoprotein,
designated as the fusion (F) protein, is responsible for virus
penetration into the host cell and syncytium formation .
The F protein plays a key role in viral virulence and is a
major target for the immune response . The NDV F
protein is a trimeric type I integral membrane protein that
is synthesized as an inactive precursor, F0 (66 kDa), which
is posttranslationally cleaved by host-cell proteases into
two disulﬁde-linked subunits, the N-terminal F2
(12.5 kDa) and the C-terminal F1 (55 kDa) [7, 8]. The
sequence of the F protein cleavage site is a major deter-
minant of NDV pathogenicity. The cleavage sites of viru-
lent NDV strains usually contain multiple basic residues,
whereas avirulent strains have fewer basic residues .
Electronic supplementary material The online version of this
article (doi:10.1007/s00705-015-2434-y) contains supplementary
material, which is available to authorized users.
& Juan Cristina
Laboratorio de Virologia Molecular, Centro de
Investigaciones Nucleares, Facultad de Ciencias, Universidad
de la Republica, Igua 4225, 11400 Montevideo, Uruguay
Arch Virol (2015) 160:1893–1900