Efficacy of a recombinant Lactobacillus plantarum Lp-pPG-Malt as an oral vaccine candidate against Aeromonas hydrophila infection in crucian carp.

Aeromonas hydrophila (A. hydrophila), a gram-negative bacterium, causes serious diseases with various clinical symptoms in farm raised fish. Thus, different ways to prevent and control A. hydrophila infection need to be explored, including a vaccine. In this study, we evaluated the protective efficacy of an oral vaccine prepared from the A. hydrophila TPS maltoporin (Malt) with Lactobacillus plantarum (L. plantarum) against A. hydrophila infection in crucian carp (Carassius auratus). For the in vivo experiment, the oral vaccine was administered to crucian carp by feeding them fish diets containing Lp-pPG-Malt, Lp-pPG and PBS for 28 days. The enzyme-linked immunosorbent assay (ELISA), leukocyte phagocytosis assay and real-time quantitative polymerase chain reaction (RT-qPCR) were performed to measure the protective efficacy of the Lp-pPG-Malt. ELISA and leukocyte phagocytosis assay confirmed that Lp-pPG-Malt significantly enhanced the IgM level and nonspecific immune response of crucian carp compared with the control groups (Lp-pPG and PBS). The RT-qPCR results showed that the Lp-pPG-Malt increased the relative expression of immune-related genes (IL-10, IL-1ß, TNF-α, IFN-γ) of crucian carp in various tissues (liver, spleen, head kidney and hind intestine). Moreover, Lp-pPG-Malt significantly increased the relative percent survival of fish after intraperitoneal injection with A. hydrophila (55%) compared with the Lp-pPG and PBS groups (0%). These findings suggest that Lp-pPG-Malt can serve as an oral vaccine candidate for A. hydrophila infection and that Malt can be used as an effective antigen in crucian carp farming.

Lc-pPG-612-OmpU-CTB: A promising oral vaccine for protecting Carassius auratus against Vibrio mimicus infection.

Vibrio mimicus (V. mimicus) is known to cause severe bacterial diseases with high mortality rates in fish, resulting in significant economic losses in the global aquaculture industry. Therefore, the objective of this study was to develop a safe and effective vaccine for protecting Carassius auratus (C. auratus) against V. mimicus infection. Recombinant Lactobacillus casei (L. casei) strains, Lc-pPG-612-OmpU and Lc-pPG-612-OmpU-CTB (surface-displayed), were constructed using a L. casei strain (ATCC 393) as an antigen delivery carrier and the cholera toxin B subunit (CTB) as an adjuvant. The two recombinant strains of L. casei were administered to C. auratus via oral immunization, and the protective efficacy of the oral vaccines was assessed. The results demonstrated that oral immunization with the two strains significantly increased the levels of nonspecific immune indicators in C. auratus, including alkaline phosphatase (AKP), lysozyme (LYS), acid phosphatase (ACP), complement 3 (C3), complement 4 (C4), lectin, and superoxide dismutase (SOD). Moreover, the experiment groups exhibited significant increases in specific immunoglobulin M (IgM) antibodies against OmpU, as well as the transcription of immune-related genes (ie., IL-1ß, TNF-α, IL-10, and TGF-ß), when compared to the control groups. Following infection of C. auratus with V. mimicus, the mortality rate of the recombinant L. casei-treated fish was observed to be lower compared to the control group. This finding suggests that recombinant L. casei demonstrates effective protection against V. mimicus infection in C. auratus. Furthermore, the addition of the immune adjuvant CTB was found to induce a more robust adaptive and innate immune response in C. auratus, resulting in reduced mortality after infection with V. mimicus.

Oral vaccination with recombinant Lactobacillus casei with surface displayed OmpK fused to CTB as an adjuvant against Vibrio mimicus infection in Carassius auratus.

Vibrio mimicus (V. mimicus) is a pathogenic bacterium that causes diseases in humans and various aquatic animals. A particularly efficient way to provide protection against V. mimicus is through vaccination. However, there are few commercial vaccines against V. mimics, especially oral vaccines. In our study, two surface-display recombinant Lactobacillus casei (L. casei) Lc-pPG-OmpK and Lc-pPG-OmpK-CTB were constructed using L. casei ATCC393 as an antigen delivery vector, outer membrane protein K (OmpK) of V. mimicus as an antigen, and cholera toxin B subunit (CTB) as a molecular adjuvant; furthermore, the immunological effects of recombinant L.casei in Carassius auratus (C. auratus) were assessed. The results indicated that oral recombinant L.casei Lc-pPG-OmpK and Lc-pPG-OmpK-CTB stimulated higher levels of serum-specific immunoglobulin M (IgM) and increased the activity of acid phosphatase (ACP), alkaline phosphatase (AKP), superoxide dismutase (SOD), lysozyme (LYS), lectin, C3, and C4 in C. auratus, compared with control groups (Lc-pPG group and PBS group). Furthermore, the expression of interleukin-1ß (IL-1ß), interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α), and transforming growth factor-ß (TGF-ß) in the liver, spleen, head kidney, hind intestine and gills of C. auratus was significantly increased, compared with that in the controls. These results demonstrated that the two recombinant L. casei strains could effectively trigger humoral and cellular immunity in C. auratus. In addition, two recombinant L.casei strains were able to survive and colonize the intestine of C. auratus. Importantly, after being challenged with V. mimicus, C. auratus fed Lc-pPG-OmpK and Lc-pPG-OmpK-CTB exhibited greater survival rates than the controls (52.08% and 58.33%, respectively). The data showed that recombinant L. casei could elicit a protective immunological response in C. auratus. The effect of the Lc-pPG-OmpK-CTB group was better than that of the Lc-pPG-OmpK group, and Lc-pPG-OmpK-CTB was found to be an effective candidate for oral vaccination.

Dietary supplementation with Weissella cibaria C-10 and Bacillus amyloliquefaciens T-5 enhance immunity against Aeromonas veronii infection in crucian carp (Carassiu auratus).

With the aim to discover novel lactic acid bacteria and Bacillus strains from fish as potential probiotics to replace antibiotics in aquaculture, the present study was conducted to isolate lactic acid bacteria and Bacillus from intestinal tract of healthy crucian carp (Carassiu auratus) and largemouth bass (Micropterus salmoides) and evaluate their resistance against Aeromonas veronii. Based on the evaluation of antibacterial activity and tolerance test, one strain of lactic acid bacteria (Weissella cibaria C-10) and one strain of Bacillus (Bacillus amyloliquefaciens T-5) with strong environmental stability were screened out. The safety evaluation showed that these two strains were non-toxic to crucian carp and were sensitive to most antibiotics. In vivo study, the crucian carps were fed a basal diet supplemented with W. cibaria C-10 (C-10), B. amyloliquefaciens T-5 (T-5) and W. cibaria C-10 + B. amyloliquefaciens T-5 (C-10+T-5), respectively, for 5 weeks. Then, various immune parameters were measured at 35 days of post-feeding. Results showed both probiotics could improve the activities of related immune enzymes, immune factors and non-specific immune antibodies in blood and organs (gill, gut, kidney, liver, and spleen) of crucian carp in varying degrees. Moreover, after 7 days of challenge experiment, the survival rates after challenged with A. veronii of W. cibaria C-10 (C-10), B. amyloliquefaciens T-5 (T-5) and W. cibaria C-10 + B. amyloliquefaciens T-5 (C-10+T-5) supplemented groups to the crucian carps were 20%, 33% and 22%, respectively. Overall, W. cibaria C-10 and B. amyloliquefaciens T-5 could be considered to be developed into microecological preparations for the alternatives of antibiotics in aquaculture.

Comparative genomics analysis of strains from diverse sources reveals the evolutionary relationship of Aeromonas veronii.

Aeromonas veronii (A. veronii, AV) strains are emerging zoonotic and aquatic pathogens, yet we know very little about their genomics. This study aims to utilize comparative genomics to investigate the intraspecific genetic diversity, differences in virulence factors and evolutionary mechanisms of A. veronii strains from diverse sources and to fundamentally demonstrate their pathogenic mechanisms. We conducted comparative genomics analysis of 39 A. veronii strains from different sources and found that 1993 core genes are shared by these strains and that these shared core genes may be necessary to maintain the basic characteristics of A. veronii. Additionally, phylogenetic relationship analysis based on these shared genes revealed that a distant relationship between the AMC34 strain and the other 38 strains but that, the genetic relationship among the 38 strains is relatively close, indicating that AMC34 may not belong to A. veronii. Furthermore, analysis of shared core genes and average nucleotide identity (ANI) values showed no obvious correlation with the location of A. veronii isolation and genetic relationship. Our research indicates the evolutionary mechanism of A. veronii from different sources and provides new insights for a deeper understanding of its pathogenic mechanism.

Bacillus subtilis BSH has a protective effect on Salmonella infection by regulating the intestinal flora structure in chickens.

Salmonellosis is a worldwide zoonotic disease that poses a serious threat to the reproduction of livestock and poultry and the health of young animals. Probiotics including Bacillus species, have received increasing attention as a substitute for antibiotics. In this study, chicks infected with Salmonella were fed feed supplemented with the BSH to observe the pathological changes in the liver, detect the number of viable bacteria in the liver and spleen, and record the death of the chicks. The results showed that BSH could reduce the pathological changes in the liver and the invasion of Salmonella into the liver and spleen of chicks. In addition, the survival rate of chicks in the BSH experimental group was 60%, while that in the infected control group was 26%, indicating that BSH had a protective effect on chicks infected with Salmonella. Finally, the fecal microflora of 9-day-old chicks was analyzed by 16S rRNA high-throughput sequencing. The results showed that Salmonella infection could cause intestinal flora changes, while BSH could alleviate this change. In addition, BSH also promoted the proliferation of Lactobacillus salivarius in the cecum of chick. This study emphasized that BSH has anti- Salmonella infection effects in chickens and can be used as a candidate microecological preparation strain.

Construction and immune efficacy of recombinant Lactobacillus casei strains expressing Malt from Aeromonas veronii.

Aeromonas veronii is an important zoonotic pathogen that causes significant economic losses in the aquaculture industry. The use of probiotics in aquaculture is a practical alternative to antibiotics to promote animal health and aid in disease prevention. In the present study, we aimed to construct a recombinant Lactobacillus casei(surface-displayed or secretory) strain containing Malt from A. veronii TH0426 and assess its potential as an oral vaccine. A 1314-bp Malt gene fragment was successfully amplified and cloned into a prokaryotic protein expression system. Protein expression in resulting recombinant strains Lc-MCS-Malt (surface-displayed) and Lc-pPG-Malt (secretory) was then verified by Western blotting and indirect immunofluorescence. A single band was observed on the Western blots, with the molecular weight of the corresponding protein shown to be 48 kDa. Furthermore, a fluorescent signal for Lc-MCS-Malt was observed by fluorescence microscopy. At 0, 7, 16, 25, and 34 days post-immunization, tissue and blood samples were collected from common carp orally administered with the recombinant L. casei strains for immune-related index analyses. Treatment of common carp with the recombinant vaccine candidate stimulated high serum or skin mucus specific antibody titers and induced a higher lysozyme, ACP, SOD activity, while fish fed with Lc-pPG or PBS had no detectable immobilizing immune responses. Expression of IL-10, IL-1ß, TNF-α, and IFN-γ genes in the group immunized with recombinant L. casei were significantly (P < 0.05) up regulated as compared with control groups, indicating that inflammatory response and cell immune response were triggered. Results also showed that recombinant L. casei could stimulate the mucosa through colonization of the intestine, resulting in increased transcription of IL-10, IL-1ß, TNF-α, and IFN-γ. Immunity and colonization assays also showed that after 34 days of fasting, recombinant L. casei were still present in the intestines of the immunized fish. Common carp that received Lc-MCS-Malt(53.3%) and Lc-pPG-Malt (46.7%) exhibited higher survival rates than the controls after challenge with the pathogen A. veronii. Our findings suggested that recombinant L. casei can adequately protect fish and improve immunity, providing a theoretical basis for the future development of an oral Lactobacillus vaccine for use in aquaculture.

An effective live attenuated vaccine against Aeromonas veronii infection in the loach (Misgurnus anguillicaudatus).

Aeromonas veronii is a major pathogenic bacterium in humans and animals. When it causes outbreaks, there are enormous economic losses to the aquaculture industry. An effective live attenuated vaccine strain, ΔhisJ, was obtained in our previous studies by gene knockout in Aeromonas veronii TH0426 using the suicide vector pRE112. Here, we evaluated whether the live attenuated vaccine ΔhisJ was suitable for prevention of Aeromonas veronii infection by injection and immersion in loaches. Compared with that of the TH0426 wild-type strain, the virulence of the live vaccine was significantly weakened. Vaccine safety assessment results also indicated that 1 × 107 CFU/mL live vaccine was safe and did not induce clinical symptoms or obvious pathological changes. Additionally, after challenging loaches with Aeromonas veronii TH0426, the relative percent survival of the IN3 injection group was 65.66%, and that of the IM group was 50.78%. Our data show that the live attenuated vaccine ΔhisJ can improve the immune protection rate of loaches. Furthermore, increased enzyme activity parameters (SOD, LZM, ACP, and AKP) in the skin mucus, increased enzyme activity parameters (SOD, LZM, ACP, AKP, and GPx) in the serum, increased specific IgM antibodies and cytokine IL-1ß contents in the serum, and increased cytokine (IL-15, pIgR, IL-1ß, and TNF-α) expression in the liver and spleen were observed. These data are the first to indicate that the live attenuated vaccine ΔhisJ is suitable for the development of a safe and effective vaccine against Aeromonas veronii infection in loach aquaculture.

Immunological evaluation of invasive Lactobacillus plantarum co-expressing EtMIC2 and chicken interleukin-18 against Eimeria tenella.

Chicken coccidiosis is a protozoan parasitic disease that leads to considerable economic losses in the poultry industry. In this study, we used invasive Lactobacillus plantarum (L.P) expressing the FnBPA protein as a novel bacterial carrier for DNA delivery into epithelial cells to develop a live oral DNA vaccine. A fusion DNA vaccine co-expressing EtMIC2 and chicken IL-18 (chIL-18) was constructed and then delivered to the host by invasive L.P. Its efficacy against Eimeria tenella challenge was evaluated in chickens by examining the relative weight gain rate; caecal lesion score; OPG; anti-coccidial index (ACI); levels of EtMIC2 antibody, FnBPA, IL-4, IL-18, IFN-γ and SIgA; and proliferation ability and percentages of CD4+ and CD8+ splenocytes. The experimental results showed that chickens immunized with invasive L.P carrying the eukaryotic expression vector pValac-EtMIC2 (pValac-EtMIC2/pSIP409-FnBPA) had markedly improved immune protection against challenge compared with that of chickens immunized with non-invasive L.P (pValac-EtMIC2/pSIP409). However, invasive L.P co-expressing EtMIC2 with the chIL-18 vector exhibited the highest protection efficiency against E. tenella. These results indicate that invasive Lactobacillus-expressing FnBPA improved humoural and cellular immunity and enhanced resistance to E. tenella. The DNA vaccine delivered by invasive Lactobacillus provides a new concept and method for the prevention of E. tenella.

Great effect of porin(aha) in bacterial adhesion and virulence regulation in Aeromonas veronii.

Aeromonas veronii is a serious pathogen which can infect mammals and aquatic organisms and causes irreparable damage to fish aquaculture. It has been demonstrated that adhesion to host surface and cells is the initial step in bacterial pathogenesis. Previous study found that bacterial weaken motility probably caused by the absence of flagellar related genes. In this study, we generated the aha deletion and complementary strains and found that two strains can be stably inherited for more than 50 generations. No significant change was found in the growth of mutant △aha. But the ability of biofilm formation, the adhesion and invasion to EPC cells significantly decreased for 3.7-fold and 2.3-fold respectively. Due to aha gene deletion, the stability of A. veronii flagellar was severely declined and the mutant △aha with no mobility. Compared with the wild-type TH0426, the pathogenicity of A. veroniiaha-deleted strain to zebrafish and mice reduced significantly and virulence attenuated severely. Cytotoxicity experiment also proved that mutant △aha showed much weaker virulence at the same time infection. The consequences declared that the stability of flagellar decreased severely with porin missing and lost the motility. Porin regulated by aha gene is essential for the adhesion and virulence of A. veronii. Thence, the mutant △aha of A. veronii provides an important tool for further concentration on the pathogenic mechanism of A. veronii.

Oral immunization with recombinant Lactobacillus casei expressing flaB confers protection against Aeromonas veronii challenge in common carp, Cyprinus carpio.

Aeromonas veronii is an important type of gram-negative pathogen of human-livestock-aquatic animal and causes great economic losses in the aquaculture industry. Vaccination is an effective method of defence against A. veronii. There are many factors that restrict the use of vaccination, and the development of new oral vaccines is urgently needed. The selection of suitable antigens is of great significance for the development of aquaculture vaccines. Bacterial flagellin can specifically bind to TLR5 and induce the release of cytokines from the organism, which could be used in the development of vaccines. In this study, we constructed two recombinant Lactobacillus casei (L. casei) (surface-displayed or secretory) expressing the flaB of A. veronii and evaluated the effect of immune responses in common carp. The flaB gene (900 bp) of A. veronii was subcloned into the L. casei expression plasmids pPG-1 (surface-displayed) and pPG-2 (secretory). Western blot and immunofluorescence assays confirmed the expression of the recombinant flaB protein. Common carp immunized with Lc-pPG-1-flaB and Lc-pPG-2-flaB via oral administration route exhibited induction of antibody expression and innate immune responses. The results indicated that Lc-pPG-1-flaB and Lc-pPG-2-flaB can induce high levels of IgM, ACP, AKP, LZM and SOD activity in organisms, and Lc-pPG-1-flaB can induce even higher levels. The recombinant L. casei may effectively induce humoral immunity and increase the serum immunological index. Furthermore, leukocytes phagocytosis percentage and index of the recombinant L. casei were enhanced. The results of qRT-PCR showed that recombinant L. casei can significantly increase the expression of IL-10, IL-ß, IFN-γ and TNF-α in the tissues of immunized common carp, compared with control groups. Viable recombinant L. casei strains, which were delivered directly survived throughout the intestinal tract. Common carp that received Lc-pPG-1-flaB (66.7%) and Lc-pPG-2-flaB (53.3%) exhibited higher survival rates than the controls after challenge with the pathogen A. veronii. Our work indicated that Lc-pPG-1-flaB and Lc-pPG-2-flaB had beneficial effects on immune response and enhanced the disease resistance of common carp against A. veronii infection. The combination of flaB delivery and the Lactic acid bacteria (LAB) approach may be a promising method for the development of oral vaccines for treating A. veronii. In future research, we will focus on the colonization ability of LAB in the intestines and on the impact of these bacteria on intestinal flora.

Oral Administration of Lactobacillus Casei Expressing Flagellin A Protein Confers Effective Protection against Aeromonas Veronii in Common Carp, Cyprinus Carpio.

Aeromonas veronii is a pathogen capable of infecting humans, livestock and aquatic animals, resulting in serious economic losses. In this study, two recombinant Lactobacillus casei expressing flagellin A (FlaA) of A. veronii, Lc-pPG-1-FlaA (surface-displayed) and Lc-pPG-2-FlaA (secretory) were constructed. The immune responses in fish administered with recombinant L. casei were evaluated. The two recombinant L. casei were orally administered to common carp, which stimulated high serum IgM and induced higher ACP, AKP, SOD and LYZ activity. Using qRT-PCR, the expression of IL-10, IL-8, IL-1ß, TNF-α and IFN-γ in the tissue of fish immunized with recombinant L. casei was significantly (p < 0.05) upregulated, which indicated that recombinant L. casei could activate the innate immune system to trigger the cell immune response and inflammatory response. Furthermore, recombinant L. casei was able to survive the intestinal environment and colonize in intestine mucosal. The study showed that after being challenged by A. veronii, fish administered with Lc-pPG-1-FlaA (70%) and Lc-pPG-2-FlaA (50%) had higher survival rates compared to Lc-pPG and PBS, indicating that recombinant L. casei might prevent A. veronii infection by activating the immune system to trigger immune responses. We demonstrated that flagellin as an antigen of vaccine, is acceptable for preventing A. veronii infection in fish. The recombinant L. casei expressing FlaA may be a novel mucosal vaccine for treating and controlling A. veronii.

Oral immunization with recombinant Lactobacillus casei expressing OmpAI confers protection against Aeromonas veronii challenge in common carp, Cyprinus carpio.

Aeromonas veronii is a gram-negative pathogen capable of infecting both fish and mammals, including humans, and natural infection in fish results in irreparable damage to the aquaculture industry. Lactic acid bacteria (LAB) have a number of properties that make them attractive candidates as delivery vehicles for presentation to the mucosa sites of compounds with pharmaceutical interest, in particular vaccines. In this study, we generated two recombinant Lactobacillus casei (surface-displayed or secretory) expressing the OmpAI of A.veronii and evaluated the effect on immune responses in fish model. A 1022 bp gene fragment of the 42 kDa OmpAI antigen of A.veronii was cloned into pPG-1 (surface-displayed) and pPG-2 (secretory) and electrotransformed into Lactobacillus casei CC16. The recombinant plasmid in L.casei could be stably inherited over 50 generations, and production of OmpAI protein had slight limited effects on cells growth. Treatment of common carp with the recombinant vaccine candidate stimulated high serum or skin mucus specific antibody titers and induced a higher lysozyme, ACP, SOD activity, while fish fed with Lc-pPG or PBS had no detectable immobilizing immune responses. Expression of IL-10, IL-ß, IFN-γ, TNF-α genes in the group immunized with recombinant L.casei were significantly (P < 0.05) up regulated as compared with control groups, indicating that inflammatory response and cell immune response were triggered. Further, viable recombinant L.casei strains were directly delivered and survive throughout the intestinal tract, the recombinant OmpAI was also detected in intestine mucosal. The results showed that common carp received Lc-pPG1-OmpAI (66.7%) and Lc-pPG2-OmpAI (50.0%) had higher survival rates compared with the controls after challenge with A.veronii, indicating that Lc-pPG1-OmpAI and Lc-pPG2-OmpAI had beneficial effects on immune response and enhanced disease resistance of common carp against A.veronii infection. Our study here demonstrates, for the first time, the ability of recombinant L.casei as oral vaccine against A.veronii infection in carps. The combination of OmpAI delivery and LAB approach may be a promising mucosal therapeutic agent for treating and controlling A.veronii.

Immunogenicity of extracellular products from an inactivated vaccine against Aeromonas veronii TH0426 in koi, Cyprinus carpio.

Aeromonas veronii is a type of human-livestock-aquatic animal pathogen; it is widely found in nature and causes many deaths among aquatic animals. Extracellular products (ECPs) are secreted by the pathogen during growth and reproduction. These products are considered effective protective antigens that can induce the host to produce an immune response. In this study, the ECPs of A.veronii TH0426 were prepared by ultrafiltration, and then the pathogenicity and enzymatic activity of the ECPs were determined. All the groups were injected intraperitoneally, as follows: group one: ECP protein with an equal volume of Freund's adjuvant; group two: ECPs and formalin-killed cells (FKC) of A.veronii combined with an equal volume of Freund's adjuvant (FKC + ECPs); group three: formalin-killed cells (FKC) of A.veronii combined with an equal volume of Freund's adjuvant (FKC); and, group four: sterile PBS as the control group. The expression levels of IgM, IL-1ß, and TNF-α and the lysozyme activity in blood were examined at 7, 14, and 21 days after the immunizations. The results show that the ECPs can produce protease, lipase, amylase and hemolyase, and there was no lecithinase, urease, or gelatinase activity. The results indicate that the ECPs were clearly pathogenic to koi fish, and the LD50 dose was 391.6 µg/fish. Throughout this study, the RPS of the three experimental groups were 75%, 50%, and 70%. This study indicates that the ECPs of A.veronii can effectively enhance the ability of kio fish to resist bacterial invasion.

Lactobacillus plantarum displaying conserved M2e and HA2 fusion antigens induces protection against influenza virus challenge.

Avian influenza virus (AIV) can infect poultry, mammals, and other hosts and causes enormous economic losses to the global poultry industry. In this study, to develop a novel and potent oral vaccine based on Lactobacillus plantarum (L. plantarum) for controlling the spread of AIV in the poultry industry, we constructed a recombinant L. plantarum strain displaying the 3M2e-HA2 protein of the influenza virus and determined the effect of N/pgsA'-3M2e-HA2 against AIV in chicks. We first confirmed that the 3M2e-HA2 fusion protein was expressed on the surface of L. plantarum via flow cytometry and immunofluorescence experiments. Our experimental results demonstrated that chicks immunized with N/pgsA'-3M2e-HA2 could induce specific humoral, mucosal, and T cell-mediated immune responses, eliciting the host body to protect itself against AIV. Additionally, compared to oral administration, the intranasal immunization of chicks with N/pgsA'-3M2e-HA2 provided a stronger immune response, resulting in a potent protective effect that hindered the loss of body weight, decreasing pulmonary virus titers and reducing lung and throat pathological damages. Thus, our results indicate that our novel approach is an effective method of vaccine design to promote mucosal immunity.

Immune responses induced by recombinant Lactobacillus plantarum expressing the spike protein derived from transmissible gastroenteritis virus in piglets.

Transmissible gastroenteritis coronavirus (TGEV) is one of the most severe threats to the swine industry. In this study, we constructed a suite of recombinant Lactobacillus plantarum with surface displaying the spike (S) protein coming from TGEV and fused with DC cells targeting peptides (DCpep) to develop an effective, safe, and convenient vaccine against transmissible gastroenteritis. Our research results found that the recombinant Lactobacillus plantarum (NC8-pSIP409-pgsA-S-DCpep) group expressing S fused with DCpep could not only significantly increase the percentages of MHC-II+CD80+ B cells and CD3+CD4+ T cells but also the number of IgA+ B cells and CD3+CD4+ T cells of ileum lamina propria, which elevated the specific secretory immunoglobulin A (SIgA) titers in feces and IgG titers in serum. Taken together, these results suggest that NC8-pSIP409-pgsA-S-DCpep expressing the S of TGEV fused with DCpep could effectively induce immune responses and provide a feasible original strategy and approach for the design of TGEV vaccines.

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.

Hepatitis E virus seroprevalence among farmers, veterinarians and control subjects in Jilin province, Shandong province and Inner Mongolia Autonomous Region, China.

China is commonly considered to be a HEV-endemic region but limited epidemiological data for HEV among farmers and veterinarians are available. Thus, a case-control study was carried out to detect the seroprevalence and assess potential risk factors associated with the acquisition of HEV infection by farmers and veterinarians in China from July 2013 to May 2015. Three hundred veterinarians and 600 farmers recruited from Jilin province, Shandong province, and Inner Mongolia Autonomous Region and 600 control subjects matched by gender, age, and residence were detected for the presence of anti-HEV IgG and IgM antibodies using enzyme immunoassays. The seroprevalences of HEV infection in farmers, veterinarians, and control subjects were 34.8%, 26.7%, and 20.2%, respectively. Farmers (P < 0.001) and veterinarians (P = 0.027) have significantly higher seroprevalence than control subjects. The highest seroprevalence of HEV infection was detected in swine farmers (49.1%) and the lowest seroprevalence was found in cattle farmers (26.5%). In veterinarians, farm animal veterinarians have a higher seroprevalence than pet veterinarians, but the difference was not significant (P > 0.05). Residence area, contact with swine and exposure with soil were significantly associated with HEV infection in the study farmers; contact with swine and source of drinking water were significantly associated with HEV infection in the study veterinarians. These results implied the high prevalence of HEV and the considerable potential for the dissemination of HEV infection in farmers and veterinarians in China. J. Med. Virol. 89:872-877, 2017. © 2016 Wiley Periodicals, Inc.

Evaluation of an anti-parasitic compound extracted from Streptomyces sp. HL-2-14 against fish parasite Ichthyophthirius multifiliis.

The present study was conducted to evaluate the anti-parasitic activity of a pure compound from Streptomyces sp. HL-2-14 against fish parasite Ichthyophthirius multifiliis, and elucidate its chemical structure. By electron ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance spectrum (1H NMR and 13C NMR), the compound was identified as amphotericin B (AmB). The in vitro trials revealed that AmB can effectively kill the theronts and tomonts of I. multifiliis with the median lethal concentration (LC50) of 0·8 mg L-1 at 30 min for the theronts and 4·3 mg L-1 at 2 h for the tomonts, respectively. AmB at 5 mg L-1 significantly reduced I. multifiliis infectivity prevalence and intensity on grass carp (Ctenopharyngodon idella), and consequently decreased fish mortality, from 100% in control group to 30% in treated group. The 72 h acute toxicity (LC50) of AmB on grass carp was 20·6 mg L-1, but fish mortality was occurred when exposure to 13·0 mg L-1. These results indicated that AmB was effective in the therapy of I. multifiliis infection, but the safety concentration margin is relatively narrow. Further efforts aiming to decrease the toxicity and improve the therapeutic profile remain to be needed.