Regulating effects of porcine interleukin-6 gene and CpG motifs on immune responses to porcine trivalent vaccines in mice

Evaluation of immunogenicity and protection mediated by Lawsonia intracellularis subunit vaccines

Lawsonia intracellularis is an economically important bacterium that causes ileitis in pigs. Current vaccines for L. intracellularis do not allow for differentiation between infected and vaccinated animals (DIVA), which is beneficial for disease tracking and surveillance. Previously, we identified five putative surface L. intracellularis proteins that were targeted by antibodies from pigs infected with L. intracellularis which could serve as antigens in a subunit vaccine. We conducted two trials to determine whether these antigens were immunogenic and provided protection against infectious challenge and whether truncated glycoprotein D could be used as a DIVA antigen. For Trial 1, 5 week-old piglets were administered intramuscular monovalent vaccines comprised of a recombinant (r) flagella subunit protein (rFliC,) and DIVA antigen (truncated glycoprotein D (TgD), a herpes virus antigen) both formulated with a combination adjuvant consisting of polyinosinic:polycytidylic acid(poly I:C), host defense peptide 1002 and polyphosphazene, referred to as Triple Adjuvant (TriAdj). Relative to control animals, animals vaccinated with rFliC and rTgD had significantly elevated antigen-specific humoral immunity in sera suggesting that rFliC and TgD are immunogenic. Control animals had negligible anti-TgD titres suggesting that TgD may be a suitable DIVA antigen for pigs. For Trial 2, piglets were immunized with a trivalent vaccine (FOG vaccine consisting of rFLiC, rOppA protein (a ABC Type dipeptide transport system) and rGroEL (a stress response protein)) and a divalent vaccine (CM vaccine consisting of rClpP (an ATP-dependent Clp protease proteolytic subunit) and rMetK (a S-adenosyl methionine synthase)) formulated with Emulsigen®. Relative to the control pigs, pigs immunized with the FOG vaccine produced robust and significantly higher serum IgG antibodies against rFliC and rGroEL, and significantly higher anti-FliC and anti-GroEL IgA antibodies in jejunal (GroEL only) and ileal intestinal mucosa. Pigs immunized with CM vaccine produced significantly higher serum antibodies against rClpP and rMetK and significantly higher anti-rClpP IgA antibodies in the ileum relative to the control pigs. Quantitative polymerase chain reaction (qPCR) analysis showed that 18 days after challenge with infectious L. intracellularis, challenged/control pigs and pigs that received the CM vaccine, but not the pigs vaccinated with the FOG vaccine, shed significantly more bacteria in feces than the unchallenged controls pigs. These data suggest that the FOG vaccinated pigs showed limited protection. While promising, more work is needed to enhance the efficiency of the intramuscular vaccine to show significant disease protection.

An IL-6 gene in humphead snapper (Lutjanus sanguineus): Identification, expression analysis and its adjuvant effects on Vibrio harveyi OmpW DNA vaccine

Interleukin 6 (IL-6) is a pleiotropic cytokine that plays important role in mediating the innate and adaptive immune responses against pathogen infection. In this study, an IL-6 homolog (Ls-IL6) was identified and characterized from humphead snapper, Lutjanus sanguineus. The full-length cDNA of Ls-IL6 was 1066 bp, containing an open reading frame (ORF) of 639 bp encoding 212 amino acids, 5' untranslated region(UTR) of 63 bp and 3' UTR of 605 bp. The predicted Ls-IL6 protein had typical motif of IL-6 family and shared high identities to teleost IL-6s. Ls-IL6 extensively expressed in various tissues, and the highest expression of Ls-IL6 was detected in head kidney, spleen and thymus. In vivo, the transcript levels of Ls-IL6 were significantly up-regulated in response to Vibrio harveyi infection. Moreover, the DNA plasmid containing the OmpW of V. harveyi together with the gene encoding Ls-IL6 were successfully constructed and administered to fish, the protective efficacy of Ls-IL6 was investigated. Compared with the pcDNA-OmpW group, the level of specific antibodies against V. harveyi increased in pcDNA-IL6-OmpW injected group. After V. harveyi infection, the pcDNA-IL6-OmpW vaccinated fish showed higher relative percent survival (76%) than the relative survival of fish immunized with pcDNA-OmpW (60%). These results indicated that Ls-IL6 was involved in immune response against V. harveyi infection and could be applied as a promising adjuvant for DNA vaccines against V. harveyi.

Bioinformatics Analysis of SNPs in IL-6 Gene Promoter of Jinghai Yellow Chickens

The proinflammatory cytokine, interleukin-6 (IL-6), plays a critical role in many chronic inflammatory diseases, particularly inflammatory bowel disease. To investigate the regulation of IL-6 gene expression at the molecular level, genomic DNA sequencing of Jinghai yellow chickens (Gallus gallus) was performed to detect single-nucleotide polymorphisms (SNPs) in the region -2200 base pairs (bp) upstream to 500 bp downstream of IL-6. Transcription factor binding sites and CpG islands in the IL-6 promoter region were predicted using bioinformatics software. Twenty-eight SNP sites were identified in IL-6. Four of these 28 SNPs, three [-357 (G > A), -447 (C > G), and -663 (A > G)] in the 5' regulatory region and one in the 3' non-coding region [3177 (C > T)] are not labelled in GenBank. Bioinformatics analysis revealed 11 SNPs within the promoter region that altered putative transcription factor binding sites. Furthermore, the C-939G mutation in the promoter region may change the number of CpG islands, and SNPs in the 5' regulatory region may influence IL-6 gene expression by altering transcription factor binding or CpG methylation status. Genetic diversity analysis revealed that the newly discovered A-663G site significantly deviated from Hardy-Weinberg equilibrium. These results provide a basis for further exploration of the promoter function of the IL-6 gene and the relationships of these SNPs to intestinal inflammation resistance in chickens.

The Immune Adjuvant Effects of Flounder (Paralichthys olivaceus) Interleukin-6 on E. tarda Subunit Vaccine OmpV

Interleukin-6 (IL-6) as a pleiotropic cytokine was widely used as an effective adjuvant for vaccines in mammals. In this study, the immune adjuvant effects of two forms of flounder (Paralichthys olivaceus) IL-6, including recombinant IL-6 (rIL-6) and pcDNA3.1-IL-6 (pcIL-6), were evaluated and comparatively analyzed on E. tarda subunit vaccine recombinant outer membrane protein V (rOmpV). The results showed that the relative percent survivals of flounder vaccinated with rOmpV plus rIL-6 or pcIL-6 were significantly higher than that in the two control groups, rOmpV plus recombinant 6× histidine-tag (rHis) or empty expression vector pcDNA3.1 (pcN3). The levels of specific serum antibodies and surface membrane immunoglobulin-positive (sIg+) lymphocytes in peripheral blood, spleen, and head kidney in the two adjuvant groups were also much higher than that in the two control groups. Compared with the two control groups, higher upregulated expressions of major histocompatibility complex class Iα (MHCIα), cluster of differentiation 8α (CD8α), MHCIIα, CD4-1, interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) were detected in flounder vaccinated with rOmpV plus rIL-6 or pcIL-6 after challenge. In addition, the rOmpV plus rIL-6 could induce significant higher levels of specific serum antibodies, sIg+ lymphocytes and four genes expressions than rOmpV plus pcIL-6. These results demonstrated that both rIL-6 and pcIL-6 used as adjuvants could enhance the immune response and evoke immune protections against E. tarda infection, which has a significant value in controlling diseases using vaccines in flounder.

Immune response to dna vaccine expressing transferrin binding protein a gene of Pasteurella multocida

Haemorrhagic Septicaemia (HS), an acute and fatal disease of cattle and buffalo is primarily caused by serotype B:2 or E:2 of Pasteurella multocida. The transferrin binding protein A (TbpA) has been found to act as immunogen and potent vaccine candidate in various Gram negative bacteria including P. multocida. The present study was carried out to evaluate the potential of this antigen as a DNA vaccine against HS in mice model. The tbpA gene of P. multocida serotype B:2 was cloned in a mammalian expression vector alone and along with murine IL2 gene as immunological adjuvant to produce monocistronic and bicistronic DNA vaccine constructs, respectively. The immune response to DNA vaccines was evaluated based on serum antibody titres and lymphocyte proliferation assay. A significant increase in humoral and cell mediated immune responses was observed in mice vaccinated with DNA vaccines as compared to non immunized group. Additionally, the bicistronic DNA vaccine provided superior immune response and protection level following challenge as compared to monocistronic construct. The study revealed that DNA vaccine presents a promising approach for the prevention of HS.

Improvement of the immunity of pig to Hog cholera vaccine by recombinant plasmid with porcine interleukin-6 gene and CpG motifs

In order to observe the dosage-effect of recombinant pig interleukin-6 gene and CpG motifs on the immune responses of swine to vaccine, a novel recombinant eukaryotic VPIL6C plasmid was packed with chitosan nanoparticles (CNP) prepared by ionic cross linkage, which contains pig interleukin-6 gene and immunostimulatory sequence consisted of 11 CpG motifs. CNP-VRIL6C was then utilized to inoculate 30-day-old piglets intramuscularly at the dosage of 0.5, 1.0 and 1.5mg/per capita, respectively. Meanwhile, the piglets were injected with attenuated classical Hog cholera vaccine and designated as A1, A2 and A3 group. The blood was weekly collected from the piglets after vaccination to detect the changes of immunoglobulins, specific antibody, interleukins, IFN-γ and immune cells. The results were found that compared to those of the control piglets injected with VR1020-CNP, the content of IgG, IgA and IgM, specific antibodies, IL-2, IL-6 and IFN-γ significantly increased in the sera from the treated three groups from 14 to 70 days after vaccination (P<0.05); the number of T(H), T(C) and CD3(+) positive T cells raised obviously in the blood of VPIL6C treated piglets (P<0.05). Also the above immune indexes of A1 group were significantly lower to different extent in comparison with those of A2 and A3 group from 14 to 56 days post inoculation (P>0.05). Moreover, the lymphocytes also remarkably elevated in the treated groups (P<0.05). These indicate that VPIL6C entrapped with CNP is a novel effective adjuvant to boost the humoral and cellular immunity of pig to Hog cholera, implying it's potentiality to enhance the resistance of pig against infectious diseases.

All three classes of CpG ODNs up-regulate IP-10 gene in pigs

The analysis of CpG ODN induced innate immune responses in different animal species has shown substantial similarities and differences in levels and types of induced cytokines profile. The objectives of these studies were to identify innate immune biomarkers activated by three classes of CpG ODNs in pigs. For this purpose, we investigated the kinetics of innate immune responses in immune cells from pigs following in vitro and in vivo stimulation with CpG ODNs. The mRNA expression of cytokine and chemokine genes were assayed by SYBR green based quantitative real time PCR. A-class CpG ODN induced significant but transient levels of IFN-gamma, IL-12 (P40), IL-6, IL-4 and TNF-alpha mRNA, C-class CpG ODN induced significant level of IFN-gamma, IFN-alpha and IL-12 mRNA and the lowest level of IL-4 (Th-2 type) mRNA. A very low level of some cytokines stimulation was observed by GC ODNs. It is noteworthy, that IL-12 (P35) mRNA was significantly stimulated by B-class GpC ODN 7909. Interestingly, all classes of CpG ODNs induced significant level of IP-10 at 12h post stimulation. These in vitro and in vivo observations suggest that interferon-gamma inducible protein 10 (IP-10) may be a reliable biomarker for immune activity induced by CpG ODNs in pigs.

Adjuvants for porcine reproductive and respiratory syndrome virus vaccines

This review deals with present and past efforts in utilization of vaccine adjuvants for porcine reproductive and respiratory syndrome virus (PRRSV) vaccines. PRRSV vaccines elicit delayed and weak cell-mediated immune (CMI) and antibody responses after vaccination. Several kinds of vaccine adjuvants have been utilized to accelerate and magnify immune responses to PRRSV vaccines. These adjuvants include cytokines, chemical reagents, and bacterial products. Of 11 vaccine adjuvants tested, five (i.e. interleukin-2 (IL-2), IL-12, interferon alpha (IFNalpha), polyinosinic and polycytidylic acid, and cytidine-phosphate-guanosine oligodeoxynucleotides (CpG ODN)) significantly enhance CMI response to PRRSV vaccines. The response is characterized by proliferation, cytotoxicity, and IFNgamma secretion of peripheral blood mononuclear cells or T cells in response to recall PRRSV antigens in vitro. Two (i.e. CpG ODN and cholera toxin) significantly enhance PRRSV-specific antibody response after vaccination. Two (i.e. IL-2 and CpG ODN) significantly enhance protective efficacy of PRRSV vaccines in challenge models. Improvement of immune responses to PRRSV vaccines should focus in future studies on assessing more vaccine adjuvants for their efficiency in enhancing both CMI and antibody responses and on identifying PRRSV components and strategies that down-modulate pig immune responses in order to devise vaccine adjuvants that can regulate such strategies of the virus.

Enhancement of immunity and resistance in mice by pig IL-6 gene and CpG motifs encapsulated in chitosan nanoparticle

This study was conducted to explore the synergetic effect of a novel plasmid containing a porcine IL-6 gene and CpG motifs on immunity of mice in order to develop an effective adjuvant to boost resistance against infection. The synthetic oligodeoxynucleotide containing 11 CpG motifs was inserted into the reconstructed VR1020 plasmid containing the pig IL-6 gene (VRPIL6), designated VRIL6C, and then encapsulated in chitosan nanoparticles (CNP) prepared by ionic cross linkage, designated VRIL6C-CNP. The 3-week old mice were injected, respectively, with VRIL6C-CNP, VRIL6-CNP, CpG-CNP and VR1020-CNP to detect the changes of immunity. At 28 days post inoculation, the mice were challenged with virulent hemolytic serotype 2 Streptococcus to test their resistance against infection. The results showed that there was a significant increase in immunoglobulins and interleukins in mice receiving VRIL6C-CNP compared with the control groups, as well as an increase in the lymphocytes and monocytes in the inoculated mice, so that the immunity was remarkably improved in the VRIL6C-CNP group. The challenge provoked stronger immunity and protection against infection in the VRIL6C-CNP group than in the control mice that manifested severe symptoms and lesions. This suggests that VRIL6C-CNP could remarkably enhance the nonspecific immunity of mice, and facilitate the development of an effective immunopotentiator to promote the resistance of the animals against infection.

Promotion of immunity of mice to Pasteurella multocida and hog cholera vaccine by pig interleukin-6 gene and CpG motifs

A novel oligodeoxynuleotides containing 11 CpG motifs was synthesized and inserted into the VR1020 plasmid containing pig interleukin-6 (IL-6) gene (VPIL6) to construct recombinant plasmid, VPIL6C. The chitosan nanoparticles (CNP) were prepared by ionic cross linkage to entrap the VPIL6C (VPIL6C-CNP), VPIL6 (VPIL6-CNP) and CpG (CpG-CNP). 42-Day old female mice were divided into four groups and intramuscularly injected respectively with 6 pmol VPIL6C-CNP, VPIL6-CNP, CpG-CNP and VR1020-CNP along with the bivalent vaccines against the Pasteurellosis and hog cholera. The blood was weekly collected from mice after vaccination to detect the changes of immunoglobulins, specific antibodies, IL-2, IL-4, IL-6 and immune cells. 28 days after vaccination, the mice were orally challenged with virulent Pasteurella multocida. The results showed that in comparison with those of the control VR1020 group, the content of immunoglobulins, specific antibodies and interleukins significantly increased in the sera from the treated two groups (P<0.05). Meanwhile, the number of lymphocytes and monocytes also remarkably elevated in the treated groups (P<0.05). The immune responses of VPIL6C mice were notably stronger than those of VPIL6 and CpG group. The challenge results proved that the overall immunity was further promoted in the treated mice which resisted the challenge infection; while the control mice manifested evident symptoms and lesions, and died of infection. These suggested that VPIL6C-CNP could better promote the immunity and resistance of mice against Pasteurellosis than VPIL6-CNP and CpG-CNP, and facilitate the development of effective adjuvant to enhance the immunity of animal against infection.

Enhancement of immunity to an Escherichia coli vaccine in mice orally inoculated with a fusion gene encoding porcine interleukin 4 and 6

Experiments were conducted to investigate the effect of a fusion gene of porcine IL-4 and IL-6 (PIL4/IL6) packaged with chitosan nanoparticles (CNPs) in terms of the development of a novel effective adjuvant. The IL4/PIL6 fusion gene was constructed and inserted into a eukaryotic expression vector. The plasmid was bound to CNP and then utilized to orally inoculate 21-day-old female Kunming mice that simultaneously received intramuscular injection of inactivated Escherichia coli vaccine. At 35 days post-vaccination, the mice were challenged by oral feeding with virulent O139: K88 strain EPEC E. coli bacteria. Compared with those of control mice, the content of immunoglobulins and specific antibodies to E. coli increased significantly in the sera of mice immunized with VPIL4/IL6-CNP (P<0.05). Furthermore, the levels of IL-2, IL-4 and IL-6 increased remarkably in the sera of immunized mice (P<0.05). After challenge, these immunological markers were elevated to different degrees in the mice immunized with the fusion gene construct (IL4/VPIL6-CNP) or individual plasmids (VPIL4+VPIL6-CNP). The immunized mice all survived the challenge and did not show any symptoms or lesion, whereas the VR1020-CNP control mice manifested obvious clinical symptoms and hemorrhagic lesions in the digestive tracts. These results demonstrated that VPIL4/IL6 entrapped with CNP is a novel promising adjuvant to promote specific immunity and resistance of animals against infectious pathogen.

CpG-ODN enhances mammary gland defense during mastitis induced by Escherichia coli infection in goats

Seven healthy native goats in early lactation, weighing 30-40 kg, were used in this study. The right mammary gland of the seven does were infused with CpG-ODN at a dosage of 100 microg kg(-1) body weight on the day 5 postpartum (PP). The left glands were used as controls and infused with sterile phosphate-buffered saline (PBS). On day 8 PP, the same dosage of CpG-ODN or PBS was again infused. On day 9 PP, the mammary glands (both right and left) of the seven does were infused with 6 x 10(6) colony-forming units (CFU) Escherichia coli and, at 0, 8, 16, 24, 48 and 72 h postinfection (PI), milk samples were collected from all glands. Goats were euthanized at 72 h PI and the mammary tissue harvested. Infusion with 6 x 10(6)CFU ml(-1)E. coli induced acute mastitis. Histopathological evaluations showed that polymorphonuclear neutrophils (PMNs) were still present in alveoli at 72 h PI, but PMNs in the CpG-ODN-treated glands has disappeared. Bacteria counts in milk peaked at 16 h PI and CpG-ODN induced a significant decrease in viable bacteria from 16 h PI until the end of the experiment. This study showed that CpG-ODN promoted the expression of its specific receptor (TLR-9 mRNA) in mammary tissue, stimulated IL-6 production, reduced bacteria counts in milk, attenuated the impact of inflammation mediators on cells and significantly shortened the inflammation course. These results suggest that the CpG-ODN improved mammary gland defense and, thereby, had a beneficial effects against mastitis caused by E. coli infection in goats.

Effect of transgenic expression of porcine interleukin-6 gene and CpG sequences on immune responses of newborn piglets inoculated with Pseudorabies attenuated vaccine

Porcine interleukin-6 gene and CpG sequences were used as immunoadjuvants to enhance the immune responses of newborn piglets to Pseudorabies attenuated vaccine (PAV). The titer of specific antibodies to PAV, the proliferation of lymphocytes and induced IL-2 activities were all examined to identify the immune response of the piglets. The results showed that the immune responses with CpG ODN and porcine interleukin-6 gene were significantly stronger than routine immunities. The data suggests that porcine IL-6 and CpG motifs could be employed as effective immunoadjuvants to raise the humoral and cellular responses of newborn piglets to Pseudorabies attenuated vaccine.

Deciphering the involvement of innate immune factors in the development of the host response to PRRSV vaccination

The natural response of pigs to porcine reproductive and respiratory syndrome virus (PRRSV) infections and vaccinations needs to be altered so that better protection is afforded against both homologous and heterologous challenges by this pathogen. To address this problem, real-time gene expression assays were coupled with cytokine Elispot and protein analyses to assess the nature of the anti-PRRSV response of pigs immunized with modified live virus (MLV) vaccine. Although T helper 1 (Th1) immunity was elicited in all vaccinated animals, as evidenced by the genesis of PRRSV-specific interferon-gamma secreting cells (IFNG SC), the overall extent of the memory response was variable and generally weak. Peripheral blood mononuclear cells (PBMC) isolated from these pigs responded to PRRSV exposure with a limited increase in their expression of the Th1 immune markers, IFNG, tumor necrosis factor-alpha and interleukin-15 (IL15), and a reduction in the quantity of mRNAs encoding the innate and inflammatory proteins, IL1B, IL8 and IFNA. Efforts to enhance Th1 immunity, by utilizing an expression plasmid encoding porcine IFNA (pINA) as an adjuvant, resulted in a temporary increase in the frequency of PRRSV-specific IFNG SC but only minor changes overall in the expression of Th1 associated cytokine or innate immune marker mRNA by virus-stimulated PBMC. Administration of pINA, however, did correlate with decreased IL1B secretion by cultured, unstimulated PBMC but had no effect on their ability to release IFNG. Thus, while exogenous addition of IFNA during PRRSV vaccination has an impact on the development of a Th1 immune response, other alterations will be required for substantial boosting of virus-specific protection.