Molecular and Structural Evolution of Porcine Epidemic Diarrhea Virus.

To analyze the evolutionary characteristics of the highly contagious porcine epidemic diarrhea virus (PEDV) at the molecular and structural levels, we analyzed the complete genomes of 647 strains retrieved from the GenBank database. The results showed that the spike (S) gene exhibited larger dS (synonymous substitutions per synonymous site) values than other PEDV genes. In the selective pressure analysis, eight amino acid (aa) sites of the S protein showed strong signals of positive selection, and seven of them were located on the surface of the S protein (S1 domain), suggesting a high selection pressure of S protein. Topologically, the S gene is more representative of the evolutionary relationship at the genome-wide level than are other genes. Structurally, the evolutionary pattern is highly S1 domain-related. The haplotype networks of the S gene showed that the strains are obviously clustered geographically in the lineages corresponding to genotypes GI and GII. The alignment analysis on representative strains of the main haplotypes revealed three distinguishable nucleic acid sites among those strains, suggesting a putative evolutionary mechanism in PEDV. These findings provide several new fundamental insights into the evolution of PEDV and guidance for developing effective prevention countermeasures against PEDV.

A therapeutic chimeric IgG/IgA expressed by CHO cells for oral treatment of PED in piglets.

Immunoglobulin A (IgA) of sows is critically important for assessing piglets' protective capacity against porcine epidemic diarrhea virus (PEDV). Here, we report a therapeutic chimeric anti-PEDV IgG/IgA expressed by Chinese hamster ovary (CHO) cells for oral treatment of PED. The chimeric anti-PEDV IgG/IgA was produced by the CHO cell lines, in which the heavy chain was constructed by combining the VH, Cγ1 and hinge regions of PEDV IgG mAb 8A3, and the Cα2 and Cα3 domains of a Mus musculus immunoglobulin alpha chain. The chimeric anti-PEDV IgG/IgA could neutralize the strains of CV777 (G1), P014 (G2) and HN1303 (G2) in vitro effectively, showing broad-spectrum neutralization activity. The in vivo challenge experiments demonstrated that chimeric anti-PEDV IgG/IgA (9C4) produced in the CHO cell supernatant could alleviate clinical diarrhea symptoms of the PEDV infection in piglets. In general, our study showed that chimeric anti-PEDV IgG/IgA produced from CHO cell line supernatants effectively alleviates PEDV infection in piglets, which also gives the foundation for the construction of fully functional secretory IgA by the J chain introduction to maximize the antibody therapeutic effect.

Analysis of s gene and protein structure difference between porcine coronavirus and SARS-CoV-2

The pandemic of COVID-19 (Corona virus disease 2019) caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) poses a huge threat to human health worldwide since December 2019. In order to study the correlation betweenSARS-CoV-2 and porcine coronavirus, the phylogenetic analysis of spike (S) protein amino acid sequence of human coronavirusand porcine coronavirus, the similarity analysis of the spatial structure of S1 subunit receptor binding domain (RBD) of S proteinwere conducted by bioinformatics analysis, moreover, the double- antigen sandwich ELISA kit was utilized to detect the SARSCoV-2 antibody in common porcine coronavirus positive serum. The results of phylogenetic analysis showed a low identity of Sprotein amino acid sequence between SARS-CoV-2 and porcine coronavirus, indicating a long distance of genetic evolution, andthe S1 subunit RBD spatial structure showed huge differences, meanwhile, all of the porcine coronavirus positive serum samplestested were negative of SARS-CoV-2 antibody. Our data suggested the huge differences in gene and protein level between SARS-CoV-2 and porcine coronavirus, which indicating that SARS-CoV-2 shows a minimal risk of achieving cross-species transmission byinfecting pigs to threaten public health security. This research provides a basis for studying COVID-19 pathogen traceability andbiosafety analysis of cross-species transmission.

Replication, pathogenicity, and transmission of SARS-CoV-2 in minks.

Minks are raised in many countries and have transmitted severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to humans. However, the biologic properties of SARS-CoV-2 in minks are largely unknown. Here, we investigated and found that SARS-CoV-2 replicates efficiently in both the upper and lower respiratory tracts, and transmits efficiently in minks via respiratory droplets; pulmonary lesions caused by SARS-CoV-2 in minks are similar to those seen in humans with COVID-19. We further found that a spike protein-based subunit vaccine largely prevented SARS-CoV-2 replication and lung damage caused by SARS-CoV-2 infection in minks. Our study indicates that minks are a useful animal model for evaluating the efficacy of drugs or vaccines against COVID-19 and that vaccination is a potential strategy to prevent minks from transmitting SARS-CoV-2.

Serological survey of SARS-CoV-2 for experimental, domestic, companion and wild animals excludes intermediate hosts of 35 different species of animals.

The pandemic SARS-CoV-2 has been reported in 123 countries with more than 5,000 patients died from it. However, the original and intermediate hosts of the virus remain unknown. In this study, 1,914 serum samples from 35 animal species were used for detection of SARS-CoV-2-specific antibodies using double-antigen sandwich ELISA after validating its specificity and sensitivity. The results showed that no SARS-CoV-2-specific antibodies were detected in above samples which excluded the possibility of 35 animal species as intermediate host for SARS-CoV-2. More importantly, companion animals including pet dogs (including one dog the SARS-CoV-2 patient kept and two dogs which had close contact with it) and cats, street dogs and cats also showed serological negative to SARS-CoV-2, which relieved the public concerns for the pets as SARS-CoV-2 carriers.