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.