Strategy of Developing Oral Vaccine Candidates Against Co-infection of Porcine Diarrhea Viruses Based on a Lactobacillus Delivery System

Insights into recent advancements in human and animal rotavirus vaccines: Exploring new frontiers

Rotavirus infections cause severe gastroenteritis and dehydration in young children and animals worldwide, leading to high rates of morbidity and mortality, predominantly in low- and middle-income countries. In the past decade, substantial progress has been made in the development and implementation of rotavirus vaccines, which have been essential in alleviating the global burden of this disease, not only in human being but also in livestock species like calves and piglets, where these infections can cause significant economic losses. By synthesizing the latest research and real-world evidence, this review article is designated to provide deep insights into the current state of rotavirus vaccine technology and its global implementation as well as the application of rotavirus vaccines in veterinary settings and their importance in controlling zoonotic transmission and maintaining food security.

Screening optimal DC-targeting peptide to enhance the immune efficacy of recombinant Lactobacillus expressing RHDV VP60

Dendritic cells (DCs) present an ideal target for delivering immunogenic cargo due to their potent antigen-presenting capabilities. This targeting approach holds promise in vaccine development by enhancing the efficiency of antigen recognition and capture by DCs. To identify a high-affinity targeting peptide binding to rabbit DCs, rabbit monocyte-derived DCs (raMoDCs) were isolated and cultured, and a novel peptide, HS (HSLRHDYGYPGH), was identified using a phage-displayed peptide library. Alongside HS, two other DC-targeting peptides, KC1 and MY, previously validated in our laboratory, were employed to construct recombinant Lactgobacillus reuteri fusion-expressed rabbit hemorrhagic disease virus (RHDV) capsid protein VP60. These recombinant Lactobacillus strains were named HS-VP60/L. reuteri, KC1-VP60/L. reuteri, and MY-VP60/L. reuteri. The ability of these recombinant Lactobacillus to bind rabbit DCs was evaluated both in vivo and in vitro. Results demonstrated that the DC-targeting peptide KC1 significantly enhanced the capture efficiency of recombinant Lactobacillus by raMoDCs, promoted DC maturation, and increased cytokine secretion. Furthermore, oral administration of KC1-VP60/L. reuteri effectively induced SIgA and IgG production in rabbits, prolonged rabbit survival post-challenge, and reduced RHDV copies in organs. In summary, the DC-targeting peptide KC1 exhibited robust binding to raMoDCs, and recombinant Lactobacillus expressing KC1-VP60 protein antigens efficiently induced systemic and mucosal immune responses in rabbits, conferring protective efficacy against RHDV. This study offers valuable insights for the development of novel RHDV vaccines.

Bacillus subtilis Feed Supplementation Combined with Oral E. coli Immunization in Sows as a Tool to Reduce Neonatal Diarrhea in Piglets

To investigate the effects of B. subtilis on the specific immune response of lactating sows to E. coli and the diarrhea rate in suckling piglets, thirty large white sows with similar farrowing dates were randomly divided into two groups: a feedback feeding (i.e., feeding a homogenate of intestinal contents and tissues from E. coli-infected piglets to sows; FB) group and a feedback feeding with B. subtilis (FB + BS) group. Serum, colostrum, and intestinal tissues from sows and piglets were collected to assess the immune response and intestinal barrier function at weaning. T and B cells from Peyer's patches (PPs) and mesenteric lymph nodes (MLNs) in lactating mice (with treatments consistent with the sows') were isolated to explore the underlying mechanism. The results showed that, compared with the FB group, the reproductive performance of sows and the growth performance of their offspring were effectively improved in the FB + BS group. Moreover, the levels of IgG/IgA and those of IgG/IgA against E. coli in the serum and colostrum of sows in the FB+BS group were increased (p < 0.05). Meanwhile, the ratio of CD4+/CD8+, CD4+CXCR5+PD1+, and B220+IgA+ cells in MLNs and PPs, and the IgA levels in the mammary glands of mice, were also increased in the FB + BS group (p < 0.05). Notably, in suckling piglets in the FB + BS group, the diarrhea rate was decreased (p < 0.05), and the intestinal barrier function and intestinal flora composition at weaning were significantly improved. Overall, these results indicated that B. subtilis feed supplementation combined with feedback feeding in pregnant and lactating sows can reduce diarrhea in suckling piglets by enhancing the maternal immune response against E. coli and intestinal barrier function in their offspring, improving survival rates and pre-weaning growth.

Epitope screening and vaccine molecule design of PRRSV GP3 and GP5 protein based on immunoinformatics

Porcine reproductive and respiratory syndrome (PRRS) is a respiratory disease in pigs that causes severe economic losses. Currently, live PRRSV vaccines are commonly used but fail to prevent PRRS outbreaks and reinfection. Inactivated PRRSV vaccines have poor immunogenicity, making PRRSV a significant threat to swine health globally. Therefore, there is an urgent need to develop an effective PRRSV vaccine. This study used immunoinformatics to predict, screen, design and construct a candidate vaccine that fused B-cell epitopes, CTL- and HTL-dominant protective epitopes of PRRSV strain's GP3 and GP5 proteins. The study identified 12 B-cell epitopes, 6 CTL epitopes and 5 HTL epitopes of GP3 and GP5 proteins. The candidate vaccine was constructed with 50S ribosomal protein L7/L1 molecular adjuvant, which has antigenicity, solubility, stability, non-allergenicity and a high affinity for its target receptor, TLR-3. The C-ImmSim immunostimulation results showed significant increases in cellular and humoral responses (B cells and T cells) and production of TGF-β, IL-2, IL-10, IFN-γ and IL-12. The constructed vaccine was stable and immunogenic, and it can effectively induce strong T-cell and B-cell immune responses against PRRSV. Therefore, it is a promising candidate vaccine for controlling and preventing PRRSV outbreaks.

Development of a Genetically Engineered Bivalent Vaccine against Porcine Epidemic Diarrhea Virus and Porcine Rotavirus

Porcine epidemic diarrhea virus (PEDV) is an enteric coronavirus that causes acute diarrhea, vomiting, dehydration, and a high mortality rate in neonatal piglets. In recent years, PEDV has been associated with co-infections with other swine enteric viruses, including porcine rotavirus (PoRV), resulting in increased mortality among newborn piglets. In this paper, we developed a bivalent vaccine against PEDV and PoRV by constructing a recombinant PEDV encoding PoRV VP7 (rPEDV-PoRV-VP7). The recombinant virus was constructed by replacing the entire open reading frame 3 (ORF3) in the genome of an attenuated PEDV strain YN150 with the PoRV VP7 gene using reverse genetic systems. Similar plaque morphology and replication kinetics were observed in Vero cells with the recombinant PEDV compared to the wild-type PEDV. It is noteworthy that the VP7 protein could be expressed stably in rPEDV-PoRV-VP7-infected cells. To evaluate the immunogenicity and safety of rPEDV-PoRV-VP7, 10-day-old piglets were vaccinated with the recombinant virus. After inoculation, no piglet displayed clinical symptoms such as vomiting, diarrhea, or anorexia. The PoRV VP7- and PEDV spike-specific IgG in serum and IgA in saliva were detected in piglets after rPEDV-PoRV-VP7 vaccination. Moreover, both PoRV and PEDV neutralizing antibodies were produced simultaneously in the inoculated piglets. Collectively, we engineered a recombinant PEDV expressing PoRV VP7 that could be used as an effective bivalent vaccine against PEDV and PoRV.

Epidemic and Evolutionary Characteristics of Swine Enteric Viruses in South-Central China from 2018 to 2021

Swine enteric viruses are a major cause of piglet diarrhea, causing a devastating impact on the pork industry. To further understand the molecular epidemiology and evolutionary diversity of swine enteric viruses, we carried out a molecular epidemiological investigation of swine enteric viruses (PEDV, PDCoV, PoRVA, and TGEV) on 7107 samples collected from pig farms in south-central China. The results demonstrated that PEDV is the predominant pathogen causing piglet diarrhea, and its infection occurs mainly in relatively cold winter and spring in Hunan and Hubei provinces. The positive rate of PEDV showed an abnormal increase from 2020 to 2021, and that of PoRVA and PDCoV exhibited gradual increases from 2018 to 2021. PEDV-PoRVA and PEDV-PDCoV were the dominant co-infection modes. A genetic evolution analysis based on the PEDV S1 gene and ORF3 gene revealed that the PEDV GII-a is currently epidemic genotype, and the ORF3 gene of DY2020 belongs to a different clade relative to other GII-a strains isolated in this study. Overall, our results indicated that the variant PEDV GII-a is the main pathogen of piglet diarrhea with a trend of outbreak. G9 is the dominant PoRVA genotype and has the possibility of outbreak as well. It is therefore critical to strengthen the surveillance of PEDV and PoRVA, and to provide technical reserves for the prevention and control of piglet diarrhea.