Bursin-like peptide (BLP) enhances H9N2 influenza vaccine induced humoral and cell mediated immune responses

Cistanche deserticola polysaccharide- functionalized dendritic fibrous nano-silica -based adjuvant for H9N2 oral vaccine enhance systemic and mucosal immunity in chickens

Avian influenza virus subtype H9N2 has the ability to infect birds and humans, further causing significant losses to the poultry industry and even posing a great threat to human health. Oral vaccine received particular interest for preventing majority infection due to its ability to elicit both mucosal and systemic immune responses, but their development is limited by the bad gastrointestinal (GI) environment, compact epithelium and mucus barrier, and the lack of effective mucosal adjuvants. Herein, we developed the dendritic fibrous nano-silica (DFNS) grafted with Cistanche deserticola polysaccharide (CDP) nanoparticles (CDP-DFNS) as an adjuvant for H9N2 vaccine. Encouragingly, CDP-DFNS facilitated the proliferation of T and B cells, and further induced the activation of T lymphocytes in vitro. Moreover, CDP-DFNS/H9N2 significantly promoted the antigen-specific antibodies levels in serum and intestinal mucosal of chickens, indicating the good ability to elicit both systemic and mucosal immunity. Additional, CDP-DFNS facilitate the activation of CD4 + and CD8 + T cells both in spleen and intestinal mucosal, and the indexes of immune organs. This study suggested that CDP-DFNS may be a new avenue for development of oral vaccine against pathogens that are transmitted via mucosal route.

The Functional Mechanism of BP9 in Promoting B Cell Differentiation and Inducing Antigen Presentation

The Bursa of Fabricius, an avian unique humoral immune organ, is instrumental to B cell development. Bursal-derived peptide BP9 fosters B-cell development and formation. Yet, the exact mechanism wherein BP9 impacts B cell differentiation and antigenic presentation remains undefined. In this paper, B cell activation and differentiation in the spleen cells from mice immunized with the AIV vaccine and BP9 were detected following flow cytometry (FCM) analysis. Furthermore, the molecular mechanism of BP9 in B cell differentiation in vivo was investigated with RNA sequencing technology. To verify the potential functional mechanism of BP9 in the antigenic presentation process, the transcriptome molecular basis of chicken macrophages stimulated by BP9 was measured via high-throughput sequencing technology. The results proved that when given in experimental dosages, BP9 notably accelerated total B cells, and enhanced B-cell differentiation and plasma cell production. The gene expression profiles of B cells from mice immunized with 0.01 mg/mL BP9 and AIV vaccine disclosed that 0.01 mg/mL BP9 initiated the enrichment of several biological functions and significantly stimulated key B-cell pathways in immunized mice. Crucially, a total of 4093 differentially expressed genes were identified in B cells with BP9 stimulation, including 943 upregulated genes and 3150 downregulated genes. Additionally, BP9 induced various cytokine productions in the chicken macrophage HD11 cells and activated 9 upregulated and 20 downregulated differential miRNAs, which were involved in various signal and biological processes. Furthermore, BP9 stimulated the activation of multiple transcription factors in HD11 cells, which was related to antigen presentation processes. In summary, these results suggested that BP9 might promote B cell differentiation and induce antigen presentation, which might provide the valuable insights into the mechanism of B cell differentiation upon bursal-derived immunomodulating peptide stimulation and provide a solid experimental groundwork for enhancing vaccine-induced immunity.

Status and Challenges for Vaccination against Avian H9N2 Influenza Virus in China

In China, H9N2 avian influenza virus (AIV) has become widely prevalent in poultry, causing huge economic losses after secondary infection with other pathogens. Importantly, H9N2 AIV continuously infects humans, and its six internal genes frequently reassort with other influenza viruses to generate novel influenza viruses that infect humans, threatening public health. Inactivated whole-virus vaccines have been used to control H9N2 AIV in China for more than 20 years, and they can alleviate clinical symptoms after immunization, greatly reducing economic losses. However, H9N2 AIVs can still be isolated from immunized chickens and have recently become the main epidemic subtype. A more effective vaccine prevention strategy might be able to address the current situation. Herein, we analyze the current status and vaccination strategy against H9N2 AIV and summarize the progress in vaccine development to provide insight for better H9N2 prevention and control.

Development of PDA Nanoparticles for H9N2 Avian Influenza BPP-V/BP-IV Epitope Peptide Vaccines: Immunogenicity and Delivery Efficiency Improvement

The protection of current influenza vaccines is limited due to the viral antigenic shifts and antigenic drifts. The universal influenza vaccine is a new hotspot in vaccine research that aims to overcome these problems. Polydopamine (PDA), a versatile biomaterial, has the advantages of an excellent biocompatibility, controllable particle size, and distinctive drug loading approach in drug delivery systems. To enhance the immunogenicities and delivery efficiencies of H9N2 avian influenza virus (AIV) epitope peptide vaccines, PDA nanoparticles conjugated with the BPP-V and BP-IV epitope peptides were used to prepare the nano BPP-V and BP-IV epitope peptide vaccines, respectively. The characteristics of the newly developed epitope peptide vaccines were then evaluated, revealing particle sizes ranging from approximately 240 to 290 nm (PDI<0.3), indicating that the synthesized nanoparticles were stable. Simultaneously, the immunoprotective effects of nano BPP-V and BP-IV epitope peptide vaccines were assessed. The nano BPP-V and BP-IV epitope vaccines, especially nano BP-IV epitope vaccine, quickly induced anti-hemagglutinin (HA) antibody production and a sustained immune response, significantly promoted humoral and cellular immune responses, reduced viral lung damage and provided effective protection against AIV viral infection. Together, these results reveal that PDA, as a delivery carrier, can improve the immunogenicities and delivery efficiencies of H9N2 AIV nano epitope vaccines, thereby providing a theoretical basis for the design and development of PDA as a carrier of new universal influenza vaccines.

Bursal peptide BP-IV as a novel immunoadjuvant enhances the protective efficacy of an epitope peptide vaccine containing T and B cell epitopes of the H9N2 avian influenza virus

Short peptide antigens covering conserved T or B cell epitopes have been investigated in influenza vaccines. Bursal pentapeptide V (BPP-V) and bursal peptide IV (BP-IV) are small molecular peptides that were isolated and identified from the bursa of Fabricius (BF) and induce a strong immune response at both the humoural and cellular levels. To explore the molecular adjuvant potential of BPP-V and BP-IV with an epitope vaccine, an epitope peptide (HA_284-298, GNCVVQCQTERGGLN) rich in T and B cell epitopes for the H9N2 avian influenza virus (AIV) haemagglutinin (HA) protein was selected. BPP-V and BP-IV were coupled with the epitope peptide sequence to form BPP-V and BP-IV-epitope vaccines, respectively. The immunoefficacy of BPP-V and BP-IV-epitope peptide vaccines was evaluated. The results showed that the epitope peptide had weak immunogenicity. The BPP-V-epitope peptide vaccine promoted only the secretion of anti-HA IgG and IgG1 antibodies. The BP-IV-epitope peptide vaccine not only promoted the production of anti-HA IgG and IgG1 antibodies but also significantly induced the production of the IgG2a antibody. The BP-IV-epitope peptide vaccine significantly promoted the production of interleukin (IL-4) and interferon-γ (IFN-γ) (the BPP-V epitope peptide vaccine promoted only the production of IL-4), enhanced the cytotoxic T lymphocyte (CTL) response, and increased the proportion of CD3⁺ T lymphocytes. Moreover, the BP-IV-epitope peptide vaccine promoted a cell-mediated immune response similar to that of the AIV vaccine group. Furthermore, BPP-V and BP-IV-epitope peptide vaccines could also accelerate the clearance of pulmonary virus and reduce pathological damage after the challenge with H9N2 AIV. This study demonstrates the potential of BP-IV as an effective adjuvant for the epitope peptide vaccine for the H9N2 AIV.

Polyethylenimine-coated PLGA nanoparticles-encapsulated Angelica sinensis polysaccharide as an adjuvant for H9N2 vaccine to improve immune responses in chickens compared to Alum and oil-based adjuvants

Inactivated H9N2 influenza vaccines required adjuvants to induce strong immune responses to protect poultry from the infections of H9N2 influenza viruses. Recently, positively charged nanoparticles-based adjuvant delivery systems have been extensively investigated as the novel vaccine adjuvant due to the protection antigens and drugs from degradation, promoting antigens and drugs uptake by antigen presenting cells (APCs), and inducing strong humoral and cellular immune responses. In this study, the immunostimulant Angelica sinensis polysaccharide (ASP) was encapsulated into Poly (lactic-co-glycolic acid) PLGA nanoparticles, and the Polyethylenimine (PEI) was coated on the nanoparticles to develop a novel adjuvant (ASP-PLGA-PEI). To further investigate the adjuvant activities of ASP-PLGA-PEI nanoparticles for H9N2 vaccines in chickens and compare the adjuvant activities of nanoparticles adjuvant and conventional adjuvants (Alum and oil-based adjuvant), the H9N2 antigen was incubated with three different adjuvants and then immunized with chickens to evaluate the ability of inducing humoral and cellular immune responses. The results revealed that compared to Alum adjuvant, ASP-PLGA-PEI nanoparticles adjuvant stimulated higher antibody responses, promoted the activation of CD4⁺ T cells and CD8⁺ T cells, increased the expression of Th1 cytokines IFN-γ. Compared to oil-based adjuvant (ISA-206), ASP-PLGA-PEI nanoparticles adjuvant induced comparable antibody immune responses at later period after immunization, improved the activation of CD4⁺ T cells and CD8⁺ T cells. Therefore, compared to Alum and oil-based adjuvant, the ASP-PLGA-PEI nanoparticles serve as an efficient adjuvant for H9N2 vaccine and have the potential to induce vigorous humoral and cellular immune responses in chickens.

A novel Bursin-like peptide as a potential virus inhibitor and immunity regulator in SPF chickens infected with recombinant ALV

BACKGROUND

Avian leukosis viruses (ALVs) are important contagious suppressive factors of chicken immunity and growth performance, resulted in enormous economic loss. Although virus eradication programs are applied in breeder flocks, ALVs are still widespread globally. Therefore, other valuable adjunct to reduce the negative effect of ALVs should be considered. Bursin-like peptide (BLP) showed remarkable immunomodulatory effects, whereas their influence on ALV-infected avian groups has not been reported. Here, a designed hybrid BLP was expressed in E. coli. The purified BLP was injected subcutaneously weekly in SPF chickens congenitally infected with a natural ALV strain. Then the influences of this BLP on the growth performance, immune response and virus titer of ALV-infected chickens were determined.

RESULTS

This BLP injection significantly improved the body weights of ALV-infected birds (P < 0.05). BLP injection significantly enhanced organ index in the BF in ALV-infected birds (P < 0.05). The weekly injection of BLP significantly lengthened the maintenance time of antibodies against Newcastle disease virus (NDV) attenuated vaccine of ALV-infected birds (P < 0.05) and boosted the antibody titer against avian influenza virus (AIV) H₅ inactive vaccine of mock chicken (P < 0.05). BLP injection in mock chickens enhanced the levels of serum cytokines (IL-2, IL-4 and interferon-γ) (P < 0.05). Surprisingly, the novel BLP significantly inhibited expression of the ALV gp85 gene in the thymus (P < 0.05), kidney (P < 0.05) and bursa of Fabricius (BF) (P < 0.01) of ALV-infected chickens. Both viral RNA copy number and protein level decreased significantly with BLP (50 μg/mL) inoculation before ALV infection in DF1 cells (P < 0.05).

CONCLUSIONS

This is the first report investigating the influence of BLP on the growth and immunity performance of chickens infected by ALV. It also is the first report about the antiviral effect of BLP in vivo and in vitro. This BLP expressed in E. coli showed potential as a vaccine adjuvant, growth regulator and antiretroviral drug in chickens to decrease the negative effects of ALV infection.

Antibody kinetics and immune profile analysis of a Streptococcus equi DNA vaccine expressing the FljB and SeM fusion protein in murine and equine models

Strangles is a highly prevalent, extremely contagious, and occasionally lethal infectious disease affecting horses worldwide. Prophylactic antibiotics are ineffective in prevention of disease but are recommended for exposed horses at the first sign of fever and any horse obviously ill from strangles or with complications and there is an urgent need of a cost-effective, safe, efficacious vaccine. In the present study, we sought to develop effective vaccines by fusing the Streptococcus equi subspecies equi (S. equi) antigen SeM with the flagellin of Salmonella abortus equi FljB. We also explored the immunogenicity and efficacy of this candidate vaccine in mice and horses by intramuscular injection. Mice and horses immunized with FljB-SeM DNA vaccine showed high levels of specific antibody and increased production of IFN-γ and IL-4. This confirmed that both Th1 and Th2 type responses were induced. The mice survival rate was significantly higher after immunization with FljB-SeM than with SeM alone. The FljB-SeM DNA could strengthen both the Th1 and Th2 immune responses compared to SeM and could provide better protection against S. equi. This technique could help develop a candidate vaccine for S. equi infection.

TLR-5 agonist Salmonella abortus equi flagellin FliC enhances FliC-gD-based DNA vaccination against equine herpesvirus 1 infection

Equine herpesvirus 1 (EHV-1) induces serious respiratory infections, viral abortion, neurological signs, and neonatal mortality in horses. Despite the use of vaccines, EHV-1 infection also causes a high annual economic burden to the equine industry. The poor immunogenicity of and protection conferred by EHV-1 vaccines are the major factors responsible for the spread of EHV-1 infection. The present study examined the immunogenicity of a novel DNA vaccine co-expressing FliC, a flagellin protein, in Salmonella abortus equi and the gD protein of EHV-1. Mice and horses were immunized intramuscularly with the vaccine, and mice were challenged with EHV-1. Immunofluorescence and western blotting revealed that FliC and gD can be efficiently expressed in cells. This novel vaccine significantly increased gD-specific antibody and interferon gamma (IFN-γ) levels in immunized mice and horses. Compared with controls, the viral load and morbidity were markedly reduced in FliC-gD-immunized mice after they were challenged with EHV-1. Furthermore, the immunogenicity of FliC-gD in a natural host was tested. Our results indicate that vaccinated mice and horses exhibit increased humoral and improved cellular immune responses.

Comparison of immunoadjuvant activities of four bursal peptides combined with H9N2 avian influenza virus vaccine

The bursa of Fabricius (BF) is a central humoral immune organ unique to birds. Four bursal peptides (BP-I, BP-II, BP-III, and BP-IV) have been isolated and identified from the BF. In this study, the immunoadjuvant activities of BPs I to IV were examined in mice immunized with H9N2 avian influenza virus (AIV) vaccine. The results suggested that BP-I effectively enhanced cell-mediated immune responses, increased the secretion of Th1 (interferon gamma)- and Th2 (interleukin-4)-type cytokines, and induced an improved cytotoxic T-lymphocyte (CTL) response to the H9N2 virus. BP-II mainly elevated specific antibody production, especially neutralizing antibodies, and increased Th1- and Th2-type cytokine secretion. BP-III had no significant effect on antibody production or cell-mediated immune responses compared to those in the control group. A strong immune response at both the humoral and cellular levels was induced by BP-IV. Furthermore, a virus challenge experiment followed by H&E staining revealed that BP-I and BP-II promoted removal of the virus and conferred protection in mouse lungs. BP-IV significantly reduced viral titers and histopathological changes and contributed to protection against H9N2 AIV challenge in mouse lungs. This study further elucidated the immunoadjuvant activities of BPs I to IV, providing a novel insight into immunoadjuvants for use in vaccine design.

Vaccinating for natural killer cell effector functions

Vaccination has proved to be highly effective in reducing global mortality and eliminating infectious diseases. Building on this success will depend on the development of new and improved vaccines, new methods to determine efficacy and optimum dosing and new or refined adjuvant systems. NK cells are innate lymphoid cells that respond rapidly during primary infection but also have adaptive characteristics enabling them to integrate innate and acquired immune responses. NK cells are activated after vaccination against pathogens including influenza, yellow fever and tuberculosis, and their subsequent maturation, proliferation and effector function is dependent on myeloid accessory cell-derived cytokines such as IL-12, IL-18 and type I interferons. Activation of antigen-presenting cells by live attenuated or whole inactivated vaccines, or by the use of adjuvants, leads to enhanced and sustained NK cell activity, which in turn contributes to T cell recruitment and memory cell formation. This review explores the role of cytokine-activated NK cells as vaccine-induced effector cells and in recall responses and their potential contribution to vaccine and adjuvant development.

Immunopotentiation of Different Adjuvants on Humoral and Cellular Immune Responses Induced by HA1-2 Subunit Vaccines of H7N9 Influenza in Mice

In spring 2013, human infections with a novel avian influenza A (H7N9) virus were reported in China. The number of cases has increased with over 200 mortalities reported to date. However, there is currently no vaccine available for the H7 subtype of influenza A virus. Virus-specific cellular immune responses play a critical role in virus clearance during influenza infection. In this study, we undertook a side-by-side evaluation of two different adjuvants, Salmonella typhimurium flagellin (fliC) and polyethyleneimine (PEI), through intraperitoneal administration to assess their effects on the immunogenicity of the recombinant HA1-2 subunit vaccine of H7N9 influenza. The fusion protein HA1-2-fliC and HA1-2 combined with PEI could induce significantly higher HA1-2-specific IgG and hemagglutination inhibition titers than HA1-2 alone at 12 days post-boost, with superior HA1-2 specific IgG titers in the HA1-2-fliC group compared with the PEI adjuvanted group. The PEI adjuvanted vaccine induced higher IgG1/IgG2a ratio and significantly increased numbers of IFN-γ- and IL-4-producing cells than HA1-2 alone, suggesting a mixed Th1/Th2-type cellular immune response with a Th2 bias. Meanwhile, the HA1-2-fliC induced higher IgG2a and IgG1 levels, which is indicative of a mixed Th1/Th2-type profile. Consistent with this, significant levels, and equal numbers, of IFN-γ- and IL-4-producing cells were detected after HA1-2-fliC vaccination. Moreover, the marked increase in CD69 expression and the proliferative index with the HA1-2-fliC and PEI adjuvanted vaccines indicated that both adjuvanted vaccine candidates effectively induced antigen-specific cellular immune responses. Taken together, our findings indicate that the two adjuvanted vaccine candidates elicit effective and HA1-2-specific humoral and cellular immune responses, offering significant promise for the development of a successful recombinant HA1-2 subunit vaccine for H7N9 influenza.