First Isolation and Characterization of Ochrobactrum anthropi from Pig

One Gram-negative Bacillus was isolated from a brain sample of a pig with neurological symptoms.Pathological examination showed meningitis at necropsy. Ochrobactrum anthropi (O. anthropi) was successfully isolated from the brain sample and was confirmed by biochemical reaction results (API 20 NE) and gene sequencing. The strain was highly resistant to b-lactam antibiotics. Mice were experimentally infected with O. anthropi and showed typical meningitis. This is the first report on O. anthropi isolated from a pig, and indicates that O. anthropi may have a broader host spectrum of infection.

A Duplex Real-Time PCR Assay for the Simultaneous Detection of Porcine Circovirus 2 and Circovirus 3

Porcine circoviruses(PCV) include PCV1, PCV2, and the new-emerging PCV3. PCV2 is pathogenic to pigs, but the pathogenicity of PCV3 in pigs is debatable. Recently, there have been frequent reports of PCV2 and PCV3 co-infections in clinical samples. Thus, it would be practical to develop a duplex PCR method to detect PCV2 and PCV3 simultaneously. In this study, specific primers and probes were designed to target PCV2 cap and PCV3 rep genes. A duplex real-time PCR method was then developed to detect the two viruses. The assay was found to be highly specific, sensitive, and reproducible for PCV2/3 without cross-reactions with other swine pathogens. The sensitivity of this assay was 2.9 copies for the PCV2 plasmid and 22.5 copies for the PCV3 plasmid. The established assay was then used to detect PCV2/3 infection in 340 clinical samples collected in the first half of 2017. The results showed that the co-infection rate of PCV2/3 in the samples was 27.6%. Our study provides an important tool that can be used to perform urgently needed surveys for the two porcine circoviruses to evaluate their impact on the swine industry.

Molecular Epidemiology of Porcine Circovirus Type 3 Infection in Swine Herds in China

Dear Editor,Porcine circovirus type 3(PCV3)is a new-emerging circovirus belonging to the genus Circovirus in the family Circoviridae in which PCV type 1(PCV1)and PCV type 2(PCV2)were well documented(Palinski et al.2017).PCV1 is a cell culture-derived virus and is considered to be nonpathogenic for swine,whereas PCV2 is the primary etiological agent of porcine circovirus-associated

Research and development of a novel subunit vaccine for the currently circulating pseudorabies virus variant in China

Pseudorabies(PR)is a devastating viral disease which leads to fatal encephalitis and respiratory disorders in pigs.Commercial gE-deleted live pseudorabies virus(PRV)vaccine has been widely used to control this disease in China.However,the new-emerging variants of PRV compromises the protection provided by current vaccines and lead to the outbreak of PR in vaccinated pig herds.Several killed and live vaccine candidates based on current PRV variants have been reported to be effective to control the disease.A subunit vaccine based on gB protein,one major PRV glycoprotein which elicits strong humoral and cellular immune responses,however,was never evaluated for protection against the current circulating PRV variants.In this study,full-length PRV gB protein was successfully expressed in baculovirus/insect cells in the soluble format and was tested on 3-week-old piglets as a subunit vaccine.Compared with unvaccinated pigs,the gB-vaccinated pigs developed specific antibody-mediated responses and were protected from the virulent PRV HN1201 challenge.All vaccinated pigs survived without showing any PRV-specific respiratory and neurological signs,but all unvaccinated pigs died within 7 days after HN1201 challenge.Hence,this novel gB-based vaccine could be applied as an effective subunit vaccine to control PRV variant in China.

Phenotypic Characterization of Porcine IFNc-Producing Lymphocytes in Porcine Reproductive and Respiratory Syndrome Virus Vaccinated and Challenged Pigs

Porcine reproductive and respiratory syndrome(PRRS) continues to be one of the most important swine diseases worldwide. Interferon-γ(IFNγ)-mediated type Ⅰ cell-mediated immune response plays an important role in protection from,and clearance of, PRRS virus(PRRSV). Several lymphocyte subsets including T-helper, CTLs, Th/memory cells, and cd T lymphocytes were previously reported to produce IFNc during PRRSV infection. However, the proportion and phenotypic characterization of these IFNγ-secreting lymphocytes have not been explored. In this study, IFNc producted by different lymphocyte subsets was assessed by multi-color flow cytometry after vaccination with PRRSV modified live vaccine(PRRSV-MLV) and challenge with homogeneous or heterogeneous PRRSV. The results showed that T-helper cells were the major IFNγ-secreting cell population after PRRSV-MLV vaccination and PRRSV challenge. Additionally, the proportion of IFNγ producing Th/memory cells and γδ T cells increased after PRRSV challenge. This difference was accounted for an enhanced ability to produce IFNγ in Th/memory cells and an enlarged quantity of γδ T cells. The results presented here could contribute to our understanding of the roles of IFNγ in protective immunity against PRRSV infection and may be useful for assessment of cell-mediated immunity in vaccine tests.

Development of a fluorescent probe hydrolysis-insulated isothermal PCR for rapid and sensitive on-site detection of African swine fever virus

Dear Editor,African swine fever virus(ASFV),the sole member of the family Asfarviridae,is the causative agent of African swine fever(ASF),a viral disease that leads to high mortality in domestic pigs.Since firstly identified in Kenya in the 1920s,ASFV has been prevalent in Africa,Europe,and Russian Federation(Sanchez et al.,2019).Recently,ASFV was introduced to Asian countries including China,Mongolia,Vietnam,Cambodia,Laos and South Korea,which lead to huge economic losses to local pig industries(Li and Tian,2018;Gaudreault and Richt,2019).The first case of ASFV in China was reported in August 2018(Zhou et al.,2018).

SARS-CoV-2 Serological Survey of Cats in China before and after the Pandemic

Dear Editor,SARS-Co V-2 or COVID-19 has become pandemic and spread to more than 200 countries with over 24 million human infected cases(WHO 2020).The origin of SARSCo V-2 remains unknown,though bat,pangolin,and snake were reported to be the potential animal reservoirs(Ji et al).

Interspecies transmission and evolution of the emerging coronaviruses: perspectives from bat physiology and protein spatial structure

Emergent coronaviruses(CoVs)such as SARS-CoV and MERS-CoV have posed great threats to public health worldwide over the past two decades.Currently,the emergence of SARS-CoV-2 as a pandemic causes greater public health concern.CoV diversity is due to the large size and replication mechanisms of the genomes together with having bats as their optimum natural hosts.The ecological behavior and unique immune characteristics of bats are optimal for the homologous recombination of CoVs.The relationship of spatial structural characteristics of the spike protein,a protein that is critical for recognition by host receptors,in different CoVs may provide evidence in explaining the coevolution of CoVs and their hosts.This information may help to enhance our understanding of CoV evolution and thus provide part of the basis of preparations for any future outbreaks.

RR1 and RR2 gene deletion affects the immunogenicity of a live attenuated pseudorabies virus vaccine candidate in natural pig host

As virulence-determining genes, RR1 and RR2 encode the small subunit and large subunit of viral ribonucleotide reductase(RR) in pseudorabies virus which have been extensively studied in mice. However,their role in pigs has not been adequately investigated. In this study, we deleted RR1 and RR2 genes based on a TK/g E/g I triple gene-deleted pseudorabies virus and tested its efficacy in pigs as a vaccine candidate. The rescued virus showed similar growth properties and plaque size in vitro as its parent strain. In an animal study, the virus could elicit humoral immune responses shown by generation of g B-specific antibodies and virus neutralizing antibodies.However, vaccination could not provide protection against virulent pseudorabies virus challenge since vaccinated pigs showed clinical pseudorabies-specific syndromes. The deficiency in protection may due to the generation of late and low levels of gB antibodies and virus neutralizing antibodies.