Two variants of porcine reproductive and respiratory syndrome virus (PRRSV), PRRSV 1 and PRRSV 2, have caused abortion in pregnant sows and respiratory distress in nursery pigs worldwide. PRRSV 2 has been thoroughly researched in Taiwan since 1993; however, the first case of PRRSV 1 was not reported until late 2018. To decipher the genetic characteristics of PRRSV 1 in Taiwan, open reading frame 5 (ORF5) genes of PRRSV 1 strains collected from 11 individual pig farms in 2019–2020 were successfully sequenced. All Taiwanese ORF5 sequences were closely related to Spanish-like PRRSV strains, which are considered to share a common evolutionary origin with the strain used for the PRRSV 1 vaccine. Analyses of amino acid (aa) and non-synonymous substitutions showed that genetic variations resulted in numerously specific codon mutations scattered across the neutralizing epitopes within the ORF5 gene. The PRRSV 1 challenge experiment disclosed the pathogenetic capability of the NPUST2789 isolate in nursery pigs. These findings provide comprehensive knowledge of the molecular diversity of the PRRSV 1 variant in local Taiwanese fields and facilitate the development of suitable immunization programs against this disease.

Intramuscular (IM) immunization is generally considered incapable of generating a protective mucosal immune response. In the swine industry, attempts to develop a safe and protective vaccine for controlling porcine epidemic diarrhea (PED) via an IM route of administration have been unsuccessful. In the present study, porcine chemokine ligand proteins CCL25, 27, and 28 were constructed and stably expressed in the mammalian expression system. IM co-administration of inactivated PEDV (iPEDV) particles with different CC chemokines and Freund’s adjuvants resulted in recruiting CCR9+ and/or CCR10+ inflammatory cells to the injection site, thereby inducing superior systemic PEDV specific IgG, fecal IgA, and viral neutralizing antibodies in pigs. Moreover, pigs immunized with iPEDV in combination with CCL25 and CCL28 elicited substantial protection against a virulent PEDV challenge. We show that the porcine CC chemokines could be novel adjuvants for developing IM vaccines for modulating mucosal immune responses against mucosal transmissible pathogens in pigs.

Porcine reproductive and respiratory syndrome (PRRS), which is caused by a highly transmissible pathogen called porcine reproductive and respiratory syndrome virus (PRRSV), has caused severe problems, including reproductive disorders in sows and respiratory symptoms in nursery pigs worldwide, since the early 1990s. However, currently available PRRSV vaccines do not supply complete immunity to confront the viral infection. Elicitation of PRRSV-specific neutralizing antibodies (NAbs) during the preinfectious period has been deemed to be a feasible strategy to modulate this virus, especially in farms where nursery pigs are seized with PRRSVs. A total of 180 piglets in a farrow-to-finish farm that had a natural outbreak of PRRS were distributed into three groups based on the different PRRSV NAbs levels in their dams. In the present study, piglets that received superior maternal-transferred NAbs showed delayed and relatively slight viral loads in serum and, on the whole, higher survival rates against wild PRRSV infections. A positive correlation of maternal NAbs between sows and their piglets was identified; moreover, high NAbs titers in piglets can last for at least 4 weeks. These results provide updated information to develop an appropriate immune strategy for breeding and for future PRRSV control under field conditions.

The animal origin of SARS-CoV-2 remains elusive, lacking a plausible evolutionary narrative that may account for its emergence. Its spike protein resembles certain segments of BANAL-236 and RaTG13, two bat coronaviruses considered possible progenitors of SARS-CoV-2. Additionally, its spike contains a furin motif, a common feature of rodent coronaviruses. To explore the possible involvement of rodents in the emergence of SARS-CoV-2 spike, we examined the crystal structures of the spike receptor-binding domains (RBDs) of BANAL-236 and RaTG13 each complexed with mouse receptor ACE2. Both RBDs have residues at positions 493 and 498 that align well with two virus-binding hotspots on mouse ACE2. Our biochemical evidence supports that both BANAL-236 and RaTG13 spikes can use mouse ACE2 as their entry receptor. These findings point to a scenario in which these bat coronaviruses may have coinfected rodents, leading to a recombination of their spike genes and a subsequent acquisition of a furin motif in rodents, culminating in the emergence of SARS-CoV-2.

Porcine deltacoronavirus (PDCoV), a highly transmissible intestinal pathogen, causes mild to severe clinical symptoms, such as anorexia, vomiting and watery diarrhea, in piglets and/or sows. Since the first report of PDCoV infection in Hong Kong in 2012, the virus has readily disseminated to North America and several countries in Asia. However, to date, no unified phylogenetic classification system has been developed. To fill this gap, we classified historical PDCoV reference strains into two major genogroups (G-I and G-II) and three subgroups (G-II-a, G-II-b and G-II-c). In addition, no genetic research on the whole PDCoV genome or spike gene has been conducted on isolates from Taiwan so far. To delineate the genetic characteristics of Taiwanese PDCoV, we performed whole-genome sequencing to decode the viral sequence. The PDCoV/104-553/TW-2015 strain is closely related to the G-II-b group, which is mainly composed of PDCoV variants from China. Additionally, various mutations in the Taiwanese PDCoV (104-553/TW-2015) strain might be linked to the probability of recombination with other genogroups of PDCoVs or other porcine coronaviruses. These results represent a pioneering phylogenetic characterization of the whole genome of a PDCoV strain isolated in Taiwan in 2015 and will potentially facilitate the development of applicable preventive strategies against this problematic virus.

Porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae (MHP) are both important and common pathogens in the pig industry. Both pathogens are major contributors to the porcine respiratory disease complex and serve to potentiate other bacterial infections such as Actinobacillus pleuropneumonia. This study aims to evaluate the efficacy of a ready-to-use bivalent PCV2 and MHP vaccine in the field under naturally PCV2-infected farms against existing monovalent options. We evaluated PCV2 viremia, PCV2 antibodies, and lung lesion scores in slaughtered pigs in our study across four farms in Taiwan. Our results found that in two out of four farms, the piglets vaccinated with Porcilis^® PCV M Hyo had superior whole-life PCV2 viremia reduction compared to the existing vaccination program on farms. In the lung lesion scoring, the Porcilis^® PCV M Hyo group had significantly lower Actinobacillus pleuropneumonia-type lesions in pigs than in the competitor group in two out of three farms evaluated. In this field trial, Porcilis^® PCV M Hyo proved to be efficacious in protecting piglets against both PCV2 viremia and the impact of MHP secondary infection, in the context of a reduction in viremia and reduced APP-like lesions found at slaughter.