Liposomes containing recombinant gp85 protein vaccine against ALV-J in chickens

Gp85 protein encapsulated by alginate-chitosan composite microspheres induced strong immunogenicity against avian leukosis virus in chicken

Introduction

Avian leukosis, a viral disease affecting birds such as chickens, presents significant challenges in poultry farming due to tumor formation, decreased egg production, and increased mortality. Despite the absence of a commercial vaccine, avian leukosis virus (ALV) infections have been extensively documented, resulting in substantial economic losses in the poultry industry. This study aimed to develop alginate-chitosan composite microspheres loaded with ALV-J Gp85 protein (referred to as aCHP-gp85) as a potential vaccine candidate.

Methods

Sodium alginate and chitosan were utilized as encapsulating materials, with the ALV-J Gp85 protein serving as the active ingredient. The study involved 45 specific pathogen-free (SPF) chickens to evaluate the immunological effectiveness of aCHP-gp85 compared to a traditional Freund adjuvant-gp85 vaccine (Freund-gp85). Two rounds of vaccination were administered, and antibody levels, mRNA expression of immune markers, splenic lymphocyte proliferation, and immune response were assessed. An animal challenge experiment was conducted to evaluate the vaccine's efficacy in reducing ALV-J virus presence and improving clinical conditions.

Results

The results demonstrated that aCHP-gp85 induced a significant and sustained increase in antibody levels compared to Freund-gp85, with the elevated response lasting for 84 days. Furthermore, aCHP-gp85 significantly upregulated mRNA expression levels of key immune markers, notably TNF-α and IFN-γ. The application of ALV-J Gp85 protein within the aCHP-gp85 group led to a significant increase in splenic lymphocyte proliferation and immune response. In the animal challenge experiment, aCHP-gp85 effectively reduced ALV-J virus presence and improved clinical conditions compared to other groups, with no significant pathological changes observed.

Discussion

The findings suggest that aCHP-gp85 elicits a strong and prolonged immune response compared to Freund-gp85, indicating its potential as an innovative ALV-J vaccine candidate. These results provide valuable insights for addressing avian leukosis in the poultry industry, both academically and practically.

A Multiplex Quantitative Polymerase Chain Reaction for the Rapid Differential Detection of Subgroups A, B, J, and K Avian Leukosis Viruses

Avian leukosis (AL), caused by avian leukosis virus (ALV), is a contagious tumor disease that results in significant economic losses for the poultry industry. Currently, ALV-A, B, J, and K subgroups are the most common in commercial poultry and cause possible coinfections. Therefore, close monitoring is necessary to avoid greater economic losses. In this study, a novel multiplex quantitative polymerase chain reaction (qPCR) assay was developed to detect ALV-A, ALV-B, ALV-J, and ALV-K with limits of detection of 40, 11, 13.7, and 96 copies/µL, respectively, and no cross-reactivity with other ALV subtypes and avian pathogens. We detected 852 cell cultures inoculated with clinical samples using this method, showing good consistency with conventional PCR and ELISA. The most prevalent ALV strain in Hubei Province, China, was still ALV-J (11.74%). Although single infections with ALV-A, ALV-B, and ALV-K were not found, coinfections with different subgroup strains were identified: 0.7% for ALV-A/J, 0.35% for ALV-B/J, 0.25% for ALV-J/K, and 0.12% for ALV-A/B/K and ALV-A/B/J. Therefore, our novel multiplex qPCR may be a useful tool for molecular epidemiology, clinical detection of ALV, and ALV eradication programs.

Residues 140-142, 199-200, 222-223, and 262 in the Surface Glycoprotein of Subgroup A Avian Leukosis Virus Are the Key Sites Determining Tva Receptor Binding Affinity and Infectivity

Subgroup A avian leukosis virus (ALV-A) invades cells through gp85-encoded surface glycoprotein (SU) via specifically recognizing the cellular receptor Tva. To identify the key residues of ALV-A SU that determine the Tva binding affinity and infectivity in DF-1 cells, a strategy of substituting corresponding residues of SU between ALV-A RSA and ALV-E ev-1 (using Tvb as the receptor) was adopted. A series of chimeric soluble gp85 proteins were expressed for co-immunoprecipitation (co-IP) analysis and blocking analysis of viral entry, and various recombinant viruses based on replication-competent avian retrovirus vectors containing Bryan polymerase (RCASBP) were constructed for transfection into DF-1 cells and measurement of the percentage of GFP-positive cells. The results revealed that the substitution of residues V138, W140, Y141, L142, S145, and L154 of host range region 1 (hr1), residues V199, G200, Q202, R222, and R223 of host range region 2 (hr2), and residue G262 of variable region 3 (vr3) reduced the viral infectivity and Tva binding affinity, which was similar to the effects of the −139S, −151N, −155PWVNPF, −201NFD, Δ214–215, and −266S mutations. Our study indicated that hr1 and hr2 contain the principal receptor interaction determinants, with new identified-vr3 also playing a key role in the receptor binding affinity of ALV-A.

Screening of immune biomarkers in different breeds of chickens infected with J subgroup of avian leukemia virus by proteomic

Avian leucosis (AL) is a disease characterized by tumors and is caused by the avian leukosis virus (ALV). Because of the high variability of viruses and complex pathogenic mechanisms, screening and breeding J subgroup of ALV (ALV-J) resistant avian breeds is one of the strategies for prevention and treatment of AL, thus screening of significant immune markers is needed to promote the development of disease-resistant breeds. In this study, data-independent acquisition (DIA) technology was used to detect the DEPs of three breeds of chicken according to different comparison to investigate the potential markers. Results showed special DEPs for spleen development of each breed were detected, such as PCNT, DDB2, and ZNF62. These DEPs were involved in intestinal immune network used in production of IgA signaling pathways and related to immune response which can be used as potential markers for spleen development in different breeds. The DEPs such as RAB44 and TPN involved in viral myocarditis, transcriptional misregulation in cancer, and tuberculosis can be used as potential markers of spleen immune response after ALV-J infection in chickens. Pair-wise analysis was performed for the three breeds after the infection of ALV-J. The proteins such as RFX1, TAF10, and VH1 were differently expressed between three breeds. These DEPs involved in antigen processing and expression, acute myelogenous leukemia, and viral carcinogenesis can be used as potential immune markers after ALV-J infection of different genetic backgrounds. The screening of potential markers at protein level provides a strong theoretical research basis for disease resistance breeding in poultry.

Systematic Identification of Host Immune Key Factors Influencing Viral Infection in PBL of ALV-J Infected SPF Chicken

Although research related to avian leukosis virus subgroup J (ALV-J) has lasted for more than a century, the systematic identification of host immune key factors against ALV-J infection has not been reported. In this study, we establish an infection model in which four-week-old SPF chickens are infected with ALV-J strain CHN06, after which the host immune response is detected. We found that the expression of two antiviral interferon-stimulated genes (ISGs) (Mx1 and IFIT5) were increased in ALV-J infected peripheral blood lymphocytes (PBL). A significant CD8⁺ T cell response induced by ALV-J appeared as early as seven days post-infection (DPI), and humoral immunity starting from 21 DPI differed greatly in the time scale of induction level. Meanwhile, the ALV-J viremia was significantly decreased before antibody production at 14 DPI, and eliminated at 21 DPI under a very low antibody level. The up-regulated CD8⁺ T cell in the thymus (14DPI) and PBL (7 DPI and 21 DPI) was detected, indicating that the thymus may provide the output of CD8⁺ T cell to PBL, which was related to virus clearance. Besides, up-regulated chemokine CXCLi1 at 7 DPI in PBL was observed, which may be related to the migration of the CD8⁺ T cell from the thymus to PBL. More importantly, the CD8 ^high+ T cell response of the CD8αβ phenotype may produce granzyme K, NK lysin, or IFN-γ for clearing viruses. These findings provide novel insights and direction for developing effective ALV-J vaccines.

Novel carbon quantum dots can serve as an excellent adjuvant for the gp85 protein vaccine against avian leukosis virus subgroup J in chickens

To evaluate whether carbon quantum dots (CQDs) can serve as an excellent adjuvant for the gp85 protein vaccine, this study produced recombinant gp85 protein against the avian leukosis virus subgroup J (ALV-J) in chickens. Functionalized CQDs were prepared and then linked to the recombinant gp85 protein. A total of 36 chickens were divided into 3 groups, namely, 2 experimental groups and 1 control group. Chickens from the experimental groups were inoculated twice intramuscularly with purified recombinant gp85 protein with CQDs as adjuvant or Freund's adjuvant emulsion at 14 and 21 D, whereas those from the control group were inoculated with an equivalent volume of PBS. At 35 D, the chickens were challenged with a 102.4 50% tissue culture infective dose of ALV-J. Blood samples were collected from each chicken at weekly intervals for serum antibody and viremia analyses. Results indicated that immunization with gp85-CQDs or gp85-Freund's adjuvant induced the inoculated chickens to produce positive serum antibodies (sample-to-positive ratio >0.6) at the 3rd week and persisted over 9 wk. Antibody levels in the gp85-CQDs group were higher than those in the gp85-Freund's adjuvant group. Differences were significant at 21 D (P < 0.05) and extremely significant from 28 D to 70 D (P < 0.01). Additionally, results of viremia showed higher protection in the gp85-CQDs group than in the Freund's adjuvant group. These findings highlighted the potential of CQDs as excellent candidate nanovehicles for vaccine delivery.

Oral Immunization of Chickens With Recombinant Lactobacillus plantarum Vaccine Against Early ALV-J Infection

In this study, a novel oral vaccine of recombinant Lactobacillus plantarum (L. plantarum) containing the gp85 protein was explored, and the effects of this vaccine on the prevention of subgroup J Avian Leukosis Virus (ALV-J) infection were assessed. In the current study, the gp85 protein of ALV-J was expressed on the surface of L. plantarum with the surface-display motif, pgsA, by constructing a shuttle vector pMG36e:pgsA:gp85. Surface localization of the fusion protein was verified by western blotting and flow cytometry. Subsequently, Specific Pathogen Free Hy-Line Brown layer chickens were orally vaccinated with the recombinant L. plantarum and presented with high levels of serum immunoglobulin G (IgG) and secretory immunoglobulin A (sIgA) titers in bile and duodenal-mucosal fluid. After challenged with ALV-J of a 3 × 103 50% tissue culture infective dose (TCID50), serum samples of the chickens were collected and viremia was analyzed. Results showed that, compared to the L. plantarum and PBS control group, the recombinant L. plantarum group showed a significant rise in antibody levels after inoculation, and provide improved protection against ALV-J according to viremia detection. These results indicate that oral immunization with the recombinant L. plantarum provided an effective means for eliciting protective immune response against early ALV-J infection.

Preparation of the Secretory Recombinant ALV-J gp85 Protein Using Pichia pastoris and Its Immunoprotection as Vaccine Antigen Combining with CpG-ODN Adjuvant

This study focuses on preparing the secretory recombinant J subgroup of avian leukosis virus (ALV-J) gp85 protein using Pichia pastoris and evaluating its immunoprotection as vaccine antigen combining with CpG-ODN adjuvant. The secretory recombinant plasmid pPIC9-gp85 containing ALV-J gp85 gene was designed and was transfected into the genome of P. pastoris (GS115) cells. The recombinant plasmid was expressed under the induction of methanol. The expressed products in the medium of the cells were purified and identified with endoglycosidase digestion assay and western blot mediated with monoclonal antibody (MAb) JE9. The purified product combining with CpG-ODN adjuvant was inoculated intramuscularly into 7-day-old chickens and three booster inoculations were performed on 21 days post first inoculation (dpfi), 42, and 56 dpfi. The antibody responses and cellular immune responses were detected, and the protective effects were analyzed after challenge with ALV-J. The results showed that the secretory pPIC9-gp85 plasmid was successfully constructed and could be stably expressed in GS115 cells. The expressed products were N-acetylglucosylated and could specifically combine with MAb (JE9). The secreted gp85 protein combining with CpG-ODN adjuvant could induce higher antibody response and spleen lymphocyte proliferation response and IFN-γ-inducing response, and could protect all the inoculated chickens against the viremia and the immunosuppressive lesions caused by ALV-J challenge. The results of neutralizing test in vitro suggested that the antisera with some ALV-J antibody titers could neutralize ALV-J strain and inhibit the growth of virus in vitro. The result of IFA showed that IgG antibody in the antisera could specifically combine with ALV-J strain in cells. It can be concluded that the secretory recombinant gp85 protein, as a new acetylglucosylated gp85 protein, was successfully prepared and combining with CpG-ODN adjuvant could protect the inoculated chickens against ALV-J infection. This study first reported the methods on preparing the secretory recombinant ALV-J gp85 protein using P. pastoris and evaluated its immunoprotection.

gp85 protein vaccine adjuvanted with silica nanoparticles against ALV-J in chickens

This study focused on the effect of silica nanoparticles as adjuvant for vaccine applications comprised of gp85, a dominating structural protein of J Subgroup Avian Leukosis Virus (ALV-J), and which was evaluated by comparing with the responsiveness induced by that emulsified in Freund adjuvant. Thirty-six chickens were inoculated twice with gp85 adjuvanted with the silica nanoparticles or Freund's adjuvant at the 2nd and 3rd week old. Two weeks later, the inoculated chickens were challenged with a 102.2 50% tissue culture infective dose (TCID50) of ALV-J. The blood samples were collected weekly to detect the serum antibodies and viremia. Results showed that positive serum antibodies (S/P value>0.6) against gp85 emerged at the third week in the inoculated chickens, while the antibodies level persisted longer in silica nanoparticles adjuvanted-group to Freund's adjuvanted-group. Furthermore, viremia in silica nanoparticles adjuvanted-group was recovered more quickly compared with Freund's adjuvanted-group. Hence our study revealed that silica nanoparticles can effectively improve the protection of gp85 vaccine against ALV-J and present a better performance than Freund's adjuvant.

Immunity to Avian Leukosis Virus: Where Are We Now and What Should We Do?

Avian leukosis virus (ALV) is an avian oncogenic retrovirus causing enormous economic losses in the global poultry industry. Although ALV-related research has lasted for more than a century, there are no vaccines to protect chickens from ALV infection. The interaction between chickens and ALV remains not fully understood especially with regard to the host immunity. The current review provides an overview of our current knowledge of innate and adaptive immunity induced by ALV infection. More importantly, we have pointed out the unknown area involved in ALV-related studies, which is worthy of our serious exploring in future.

Recombinant Marek's Disease Virus as a Vector-Based Vaccine against Avian Leukosis Virus Subgroup J in Chicken

Avian leukosis virus subgroup J (ALV-J) is an immunosuppressive virus that causes considerable economic losses to the chicken industry in China. However, there is currently no effective vaccine to prevent ALV-J infection. In order to reduce the losses caused by ALV-J, we constructed two effective ALV-J vaccines by inserting the ALV-J (strain JL093-1) env or gag+env genes into the US2 gene of the Marek’s disease herpesviruses (MDV) by transfection of overlapping fosmid DNAs, creating two recombinant MDVs, rMDV/ALV-gag+env and rMDV/ALV-env. Analysis of cultured chicken embryo fibroblasts infected with the rMDVs revealed that Env and Gag were successfully expressed and that there was no difference in growth kinetics in cells infected with rMDVs compared with that of cells infected with the parent MDV. Chickens vaccinated with either rMDV revealed that positive serum antibodies were induced. Both rMDVs also effectively reduced the rate of positive viremia in chicken flocks challenged with ALV-J. The protective effect provided by rMDV/ALV-env inoculation was slightly stronger than that provided by rMDV/ALV-gag+env. This represents the first study where a potential rMDV vaccine, expressing ALV-J antigenic genes, has been shown to be effective in the prevention of ALV-J. Our study also opens new avenues for the control of MDV and ALV-J co-infection.

Liposomes containing recombinant E protein vaccine against duck Tembusu virus in ducks

To obtain an effective vaccine candidate against duck Tembusu viral (DTMUV) disease which causes egg-drop and great economical loss in the Chinese duck industry, liposome vaccines containing recombinant E protein were prepared and assessed in this study. The recombinant plasmid (PET28a-E) was constructed and transformed into BL21 (DE3) cells to produce E proteins. The recombinant E proteins were purified and entrapped by liposomes through reverse-phase evaporation. Eighty-four cherry valley ducks were randomly divided into seven groups and inoculated intramuscularly at one- or seven-day-old with liposomes-E protein or Freund's adjuvant-E protein vaccine. Blood samples were collected from the first week to the tenth week for serum antibody, plasma for viremia, as well as oropharyngeal and cloacal swabs for virus shedding analyses after being challenged with a 10(2.4) 50% tissue culture infective dose (TCID50) of duck Tembusu virus. Results showed that serum antibody level of the liposomes vaccine was higher than the Freund's adjuvant vaccine, and inoculating twice was superior to once; furthermore, the viremia and virus shedding tests also proved that the liposomes vaccine can provide complete protection against DTMUV challenge. These results demonstrated that the liposomes-E protein vaccine could be used as a potential candidate vaccine to prevent DTMUV infection in ducks.

Exogenous avian leukosis virus-induced activation of the ERK/AP1 pathway is required for virus replication and correlates with virus-induced tumorigenesis

A proteomics approach was used to reveal the up-regulated proteins involved in the targeted mitogen-activated protein kinase (MAPK) signal transduction pathway in DF-1 cells after ALV subgroup J (ALV-J) infection. Next, we found that ALV-J CHN06 strain infection of DF-1 cells correlated with extracellular signal-regulated kinase 2 (ERK2) activation, which was mainly induced within 15 min, a very early stage of infection, and at a late infection stage, from 108 h to 132 h post-infection. Infection with other ALV subgroup (A/B) strains also triggered ERK/MAPK activation. Moreover, when activating ERK2, ALV subgroups A, B and J simultaneously induced the phosphorylation of c-Jun, an AP1 family member and p38 activation but had no obvious effect on JNK activation at either 15 min or 120 h. Interestingly, only PD98059 inhibited the ALV-induced c-Jun phosphorylation while SP600125 or SB203580 had no influence on c-Jun activation. Furthermore, the viral gp85 and gag proteins were found to contribute to ERK2/AP1 activation. Additionally, the specific ERK inhibitor, PD980509, significantly suppressed ALV replication, as evidenced by extremely low levels of ALV promoter activity and ALV-J protein expression. In vivo analysis of ERK2 activation in tumor cells derived from ALV-J-infected chicken demonstrated a strong correlation between ERK/MAPK activation and virus-associated tumorigenesis.

Evaluation of a multi-epitope subunit vaccine against avian leukosis virus subgroup J in chickens

The intricate sequence and antigenic variability of avian leukosis virus subgroup J (ALV-J) have led to unprecedented difficulties in the development of vaccines. Much experimental evidence demonstrates that ALV-J mutants have caused immune evasion and pose a challenge for traditional efforts to develop effective vaccines. To investigate the potential of a multi-epitope vaccination strategy to prevent chickens against ALV-J infections, a recombinant chimeric multi-epitope protein X (rCMEPX) containing both immunodominant B and T epitope concentrated domains selected from the major structural protein of ALV-J using bioinformatics approach was expressed in Escherichia coli Rosetta (DE3). Its immunogenicity and protective efficacy was studied in chickens. The results showed that rCMEPX could elicit neutralizing antibodies and cellular responses, and antibodies induced by rCMEPX could specifically recognize host cell naturally expressed ALV-J proteins, which indicated that the rCMEPX is a good immunogen. Challenge experiments showed 80% chickens that received rCMEPX were well protected against ALV-J challenge. This is the first report of a chimeric multi-epitope protein as a potential immunogen against ALV-J.

Antibody responses induced by recombinant ALV-A gp85 protein vaccine combining with CpG-ODN adjuvant in breeder hens and the protection for their offspring against early infection

To observe the antibody responses induced by recombinant A subgroup avian leukosis virus (ALV-A) gp85 protein vaccine plus CpG-ODN adjuvant and the protection of maternal antibodies (MAbs) for the hatched chickens against early infection, the gp85 gene was amplified from the proviral cDNA of ALV-A-SDAU09C1 strain using PCR and the recombinant plasmid containing target gene was constructed and expressed in EscherichiaColi. The expressed product was confirmed using SDS-PAGE and western blot that it is about 46KD of recombinant protein. The purified recombinant proteins combining with CpG-ODN adjuvant or Freund's adjuvant were inoculated into the breeder hens, the ALV-A antibodies in serum and in egg-yolk were detected; the fertilized eggs from the vaccinated hens with different titers of egg-yolk antibody were hatched and then challenged with 10(4.2)/0.1mL TCID50 of ALV-A-SDAU09C1 strain, all the hatched chickens were weekly detected for the viremias and the cloacal swab P27 antigen and pathological lesions; the neutralizing test of antisera in vitro was conducted. The results showed that the recombinant gp85 proteins combining with CpG-ODN adjuvant could induce the breeder hens to produce better antibody responses than gp85 protein with Freund's adjuvant or without adjuvant; the MAbs with higher titers induced by CpG-ODN+gp85 proteins could obviously decrease the ratios of viremias (13% vs 33%), cloacal detoxification (20% vs 67%) and death (0% vs 22%) caused by ALV-A infection than those by gp85 protein without adjuvant. The results of the neutralizing test indicated that the antisera from the hatched chickens could neutralize the ALV-A-SDAU09C1 strain in vitro, but which depends on the antibody titers. The results of IFA confirmed that the serum antibody could combine with the ALV in DF1 cells. It can be concluded that the prepared ALV-A gp85 subunit vaccine combining with CpG-ODN adjuvant could induce the breeder hens to produce better neutralizing antibody responses and protect 80% of their offspring chickens against early infection.