Genome
analysis of Getah virus (GETV) isolated from and
contaminated
in a live swine vaccine: The commercial live vaccines might be a
potential route for GETV transmission
Running Head: Getah virus (GETV) isolated from a vaccine
Feng Zhou1, Aojie Wang1, Lu
Chen1, Xingang Wang1, Dandan
Cui1, Hongtao Chang1*, Chuanqing
Wang1*
College of animal science and
veterinary medicine, Henan Agricultural University, Agricultural Road
No. 63, Zhengzhou, Henan, China (450002)
*Address correspondence to: Chuanqing Wang, E-mail: wchuanq@163.com
Hongtao Chang, E-mail: ndcht@163.com
To the Editor,
Getah virus (GETV) belongs to the
genus Alphavirus within the family Togaviridae and is a
mosquito-transmitted arbovirus(Berge et al., 1975) that can infect many
vertebrates and arthropods(Doherty et al., 1966). The first GETV strain
was isolated from Culex in Malaysia in 1955(Go et al., 2014).
The prototype virus strain was
MM2021(Elisberg et al., 1963). Serological survey of GETV showed that
GETV antibodies have been identified in humans, pigs, cattle, horses,
goats, rabbits, kangaroos, chickens, foxes and some wild birds in many
countries within Europe, Asia and Oceania.
GETV can
cause reproduction disorders and
fetal death in pigs, as well as body rash, leg edema and fever in
horses. The potential risk to animal health posed by GETV must not be
overlooked(Li et al., 1992; Kurogi et al., 1975; Doherty et al., 1972;
Tajima et al., 2014; Yago et al., 1987; Fukunaga et al., 2000)
The first GETV strain in China was isolated from mosquitoes in Hainan
province in 1964. Since then, GETVs have been isolated from mosquitoes
in more than 10 provinces in China, including Hainan, Shanghai, Sichuan,
Yunnan, Hubei and Gansu(Yang et al., 1984; Li et al., 2017; Li et al.,
2017; Li et al., 1992).
Porcine
reproductive and respiratory syndrome virus (PRRSV) and GETV are
different but common viruses
associated
with reproduction disorders in sows, and both are capable of growing in
Marc-145 cells. PRRSV modified
live vaccine (MLV) is widely used in China. In October 2017, in the
titer test of a PRRSV MLV sample from a pig farm where abortion in a
pregnant sow occurred, we found that the
caused cytopathic effect (CPE) by
the supernatant of vaccine in Marc-145 cells was significantly different
from that of the previously vaccinated PRRSV strain. Similarly, unusual
CPE was also observed in other cell lines, including Vero, PK-15, BHK-21
and human hepatocellular carcinoma HepG-2
cells.
Therefore, exogenous virus was detected by reverse
transcription-polymerase chain reaction (RT-PCR) using specific primers,
demonstrating positivity for GETV.
Because the pig farm had also been vaccinated against classical swine
fever virus, Japanese encephalitis virus, porcine parvovirus and PRRSV.
We suspected that GETV might be a contaminant in these commercial
vaccines. As expected, a GETV
strain was isolated from the commercial PRRS MLV vaccine following
isolation, passage, purification by plaque assay and observation by
transmission electron microscopy. This virus was designated as GETV-V1.
In this study, we characterized the isolated GETV strain and the genome
data of this newly identified GETV strain.
Further RT-PCR
results showed that
the commercial PRRS MLV vaccine
was positive for GETV, including nine batches of vaccine (three batches
per year) from the same manufacturer between 2015 and 2017.
Immunofluorescence assay (Figure 1) showed that Marc-145 cells infected
with the GETV isolate reacted specifically with GETV-specific monoclonal
antibody (produced by our laboratory).
The
fairly uniform morphological appearance of GETV indicated that the
diameter of the virus was 60–80 nm and close to spherical in shape. The
fiber protein was clearly visible on the membrane (Figure 2). These data
demonstrated that GETV-V1 was isolated from a contaminated live swine
vaccine.