Rapid differentiation of vaccine strain and Chinese field strains of transmissible gastroenteritis virus by restriction fragment length polymorphism of the N gene

Melatonin and other indoles show antiviral activities against swine coronaviruses in vitro at pharmacological concentrations

The current coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), highlights major gaps in our knowledge on the prevention control and cross-species transmission mechanisms of animal coronaviruses. Transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV), and porcine delta coronavirus (PDCoV) are three common swine coronaviruses and have similar clinical features. In the absence of effective treatments, they have led to significant economic losses in the swine industry worldwide. We reported that indoles exerted potent activity against swine coronaviruses, the molecules used included melatonin, indole, tryptamine, and L-tryptophan. Herein, we did further systematic studies with melatonin, a ubiquitous and versatile molecule, and found it inhibited TGEV, PEDV, and PDCoV infection in PK-15, Vero, or LLC-PK1 cells by reducing viral entry and replication, respectively. Collectively, we provide the molecular basis for the development of new treatments based on the ability of indoles to control TGEV, PEDV, and PDCoV infection and spread.

Immune response characterization of mice immunized with Lactobacillus plantarum expressing spike antigen of transmissible gastroenteritis virus

The highly infectious porcine transmissible gastroenteritis virus (TGEV), which belongs to the coronaviruses (CoVs), causes diarrhea and high mortality rates in piglets, resulting in severe economic losses in the pork industry worldwide. In this study, we used Lactobacillus plantarum (L. plantarum) to anchor the expression of TGEV antigen (S) to dendritic cells (DCs) via dendritic cell-targeting peptides (DCpep). The results show that S antigen could be detected on the surface of L. plantarum by different detection methods. Furthermore, flow cytometry and ELISA techniques were used to measure the cellular, mucosal, and humoral immune responses of the different orally gavaged mouse groups. The obtained results demonstrated the significant effect of the constructed L. plantarum expressing S-DCpep fusion proteins in inducing high expression levels of B7 molecules on DCs, as well as high levels of IgG, secretory IgA, and IFN-γ and IL-4 cytokines compared with the other groups. Accordingly, surface expression of DC-targeted antigens successfully induced cellular, mucosal, and humoral immunity in mice and could be used as a vaccine.

Sporadic re-emergence of enzootic porcine transmissible gastroenteritis in Hungary

Transmissible gastroenteritis (TGE) is a coronavirus-induced disease of pigs, characterised by diarrhoea and vomiting. The incidence of the disease had been decreasing since the late 1980s when deletion mutant variants (porcine respiratory coronavirus, PRCoV) of the virus emerged, repressing TGE gradually. Although disease manifestations are infrequent, the virus is still present in pig herds, causing sporadic outbreaks in a milder form. Identification and characterisation of the spike genes from TGEV and PRCoV, detected in such outbreaks, were performed in Hungary. Analysis of the amplified partial gene sequences showed that TGEV was present in herds with TGE clinical signs together with PRCoV. The sequences, apart from the deletions in PRCoV, were identical and at least two types of PRCoV spike proteins could be identified based on the length of the deleted sequence.

Detection and molecular diversity of spike gene of porcine epidemic diarrhea virus in China

Since late 2010, porcine epidemic diarrhea virus (PEDV) has rapidly disseminated all over the China and caused considerable morbidity and high mortality (up to 100%) in neonatal piglets. 79.66% (141 of 177) pig farms in 29 provinces (excluding Tibet and Hainan, China) and 72.27% (417 of 577) samples were positive for PEDV confirmed by reverse transcription-polymerase chain reaction (RT-PCR). The full-length S genes of representative field strains were sequenced. 33 field strains share 93.5%-99.9% homologies with each other at the nucleotide sequence level and 92.3%-99.8% homologies with each other at the amino acids sequence level. Most field strains have nucleotide deletion and insertion regions, and show lower homologies (93.5%-94.2%) with Chinese classical strain CH/S, however higher homologies (97.1%-99.3%) with recent strain CHGD-1. The phylogenetic analysis showed there are classical strains and variants prevailing in pig herd in China. PEDV has a high detection rate in pig herds in China. Sequence analysis indicated the S genes of recent field strains have heterogeneity and the variants are predominant.

Reverse transcription loop-mediated isothermal amplification for rapid detection of transmissible gastroenteritis virus

Transmissible gastroenteritis virus (TGEV) is the causative agent of porcine transmissible gastroenteritis, and sensitive detection methods are required for preventing the disease. In this article, reverse transcription-loop-mediated isothermal amplification (RT-LAMP) was developed to detect TGEV. Three pairs of primers targeting the nucleocapsid (N) gene of TGEV were synthesized and used in the RT-LAMP. The optimization, sensitivity, and specificity of the RT-LAMP were evaluated. Our results showed that the RT-LAMP amplified the N gene with high specificity, efficiency, and rapidity at isothermal condition. The optimal reaction condition was achieved at 60°C for 30 min. The RT-LAMP assay was more sensitive than gel-based RT-PCR and PCR. It had a higher sensitivity than enzyme-linked immunosorbent assay (ELISA) using the equal virus templates. In addition, the established RT-LAMP differentiated TGEV from porcine epidemic diarrhea virus, porcine rotavirus, porcine pseudorabies virus, porcine reproductive and respiratory syndrome virus, and avian infectious bronchitis virus. The approach is suitable for detecting TGEV for field diagnostics or in less-equipped laboratories due to its convenience and simplicity.