Baculovirus virions displaying infectious bursal disease virus VP2 protein protect chickens against infectious bursal disease virus infection

Vaccines against Major Poultry Viral Diseases: Strategies to Improve the Breadth and Protective Efficacy

The poultry industry is the largest source of meat and eggs for human consumption worldwide. However, viral outbreaks in farmed stock are a common occurrence and a major source of concern for the industry. Mortality and morbidity resulting from an outbreak can cause significant economic losses with subsequent detrimental impacts on the global food supply chain. Mass vaccination is one of the main strategies for controlling and preventing viral infection in poultry. The development of broadly protective vaccines against avian viral diseases will alleviate selection pressure on field virus strains and simplify vaccination regimens for commercial farms with overall savings in husbandry costs. With the increasing number of emerging and re-emerging viral infectious diseases in the poultry industry, there is an urgent need to understand the strategies for broadening the protective efficacy of the vaccines against distinct viral strains. The current review provides an overview of viral vaccines and vaccination regimens available for common avian viral infections, and strategies for developing safer and more efficacious viral vaccines for poultry.

Soluble overexpression and purification of infectious bursal disease virus capsid protein VP2 in Escherichia coli and its nanometer structure observation

As part of the development of an infectious bursal disease virus (IBDV) subunit vaccine, this study was designed to improve the expression of highly soluble VP2-LS3 (Haemophilus parasuis lumazine synthase 3, LS3) protein by using different tagged vectors in E. coli. IBDV VP2-LS3 gene was designed and synthesized. Fusion tags, GST, NusA, MBP, Ppi, γ-crystallin, ArsC, and Grifin were joined to the N-terminus of VP2-LS3 protein. Seven expression plasmids were constructed, and each plasmid was transformed into E. coli BL21 (DE3) competent cells. After induction by IPTG, the solubility and expression levels of the various VP2-LS3 proteins were analyzed by SDS-PAGE and Western Blot analysis. The fusion tag that significantly promoted soluble expression of the VP2-LS3 protein was selected. Recombinant proteins were purified using Ni-NTA affinity chromatography, then cleaved by using TEV protease and detected by using transmission electron microscopy. Gel electrophoresis and sequencing analysis showed that all seven recombinant vectors were successfully constructed. GST, NusA, MBP, Ppi, γ-crystallin, ArsC, and Grifin enhanced the expression and solubility of VP2 protein; however, MBP was more effective for the high-purity production of VP2-LS3. Western Blot analysis confirmed successful generation of VP2-LS3 fusion protein in E. coli. The result of transmission electron microscopy showed that VP2-LS3 formed nano-sized particles with homogeneous shape and relatively uniform size. This study established a method to generate VP2-LS3 recombinant protein, which may lay a foundation for the development and subsequent study of IBDV subunit vaccines.

Molecular Characterization of Infectious Bursal Disease Virus Isolated from Naturally Infected Broiler Chickens in Erbil, Iraq

The infectious bursal disease (IBD) is a highly contagious and immunosuppressive disease of broiler chickens and the development of a new genetic variant of the virus is responsible for major economic losses in the poultry industry. For this purpose, it was essential to isolate the molecular characterization of the virus from vaccinated broiler in Erbil, Iraq. Clinically, the infectious bursal disease is characterized by high mortality (10-15%) with hemorrhagic lesions on the breast and thigh muscles, hemorrhagic and edematous bursa of diseased chickens. In this study, the Bursa of Fabricus (BF) samples were collected between June 2018 and January 2019. Histopathological changes of the bursal sections showed existence of the cystic vacuolation of the lymphoid follicles with leukocytes infiltration as pathognomic features for IBD virus infection; and homogenates samples inoculated in chorioallantoic-membrane showed mortality in the second passage with varying degrees of hemorrhages. Agar gel precipitation test (AGPT) was positive with specific antisera. Reverse transcription polymerase chain reaction (RT-PCR) and nucleotide sequence analysis of five fragments in the hypervariable region of VP2 gene revealed transition and transversion changes. Among the five recent IBD virus isolates, the rate of identity was approximately 99% as compared with the very virulent IBD virus from Iran (ID: DQ785171.1). Phylogenetic analysis revealed that the five isolates were closely related to the Asian group with a different percentage ranged from 98-99% while it was 97% in the European group. The local isolate of the virus was registered in the Genebank under the accession number MN48052.1. In conclusion, the isolated IBDVs belong to a very virulent group. In addition, this study demonstrates the spread of this virulent virus to poultry industries in Erbil, Iraq. Further widespread surveys could help in delivering more information on the virus variability and might assist in designing novel vaccines for this pathogen.

Recombinant Lactococcus Expressing a Novel Variant of Infectious Bursal Disease Virus VP2 Protein Can Induce Unique Specific Neutralizing Antibodies in Chickens and Provide Complete Protection

Recent reports of infectious bursal disease virus (IBDV) infections in China, Japan, and North America have indicated the presence of variant, and the current conventional IBDV vaccine cannot completely protect against variant IBDV. In this study, we constructed recombinant Lactococcus lactis (r-L. lactis) expressing a novel variant of IBDV VP2 (avVP2) protein along with the Salmonella resistance to complement killing (RCK) protein, and Western blotting analysis confirmed that r-L. lactis successfully expressed avVP2-RCK fusion protein. We immunized chickens with this vaccine and subsequently challenged them with the very virulent IBDV (vvIBDV) and a novel variant wild IBDV (avIBDV) to evaluate the immune effect of the vaccine. The results show that the r-L. lactis-avVP2-RCK-immunized group exhibited a 100% protection rate when challenged with avIBDV and 100% survival rate to vvIBDV. Furthermore, this immunization resulted in the production of unique neutralizing antibodies that cannot be detected by conventional ELISA. These results indicate that r-L. lactis-avVP2-RCK is a promising candidate vaccine against IBDV infections, which can produce unique neutralizing antibodies that cannot be produced by other vaccines and protect against IBDV infection, especially against the variant strain.

HSC70 is required for infectious bursal disease virus (IBDV) infection in DF-1 cells

Background

Infectious bursal disease (IBD) is a highly contagious infectious disease that causes severe immunosuppression and damage to the bursa of Fabricius in chickens. Several proteins involved in IBD virus (IBDV) infection, such as surface immunoglobulin M, integrin, annexin A2 and chicken heat shock protein 90, have been identified. However, the main protein that plays key roles in virus infection has not yet been confirmed.

Methods

DF-1 cell line was transfected with the pcDNA-VP2 plasmid and analyzed by immunofluorescence assay. The proteins reacted with VP2 of IBDV in DF-1 cells were pulldown with the monoclonal antibody and identified by mass spectrometry. Heat shock cognate protein 70 (HSC70), one of these proteins, was selected to be investigated in the function in IBDV infection by specific antibody and its inhibitor.

Results

The DF-1 cell line was transfected with the pcDNA-VP2 plasmid, and expression of IBDV VP2 in DF-1 cells was confirmed by immunofluorescence assays. Heat shock cognate protein 70 (HSC70) was one of the proteins identified by coimmunoprecipitation using a monoclonal antibody (2H11) against VP2 and mass spectrometry analysis. IBDV infection in DF-1 cells was strongly inhibited by both an anti-HSC70 antibody and a HSC70 inhibitor (VER155008).

Conclusion

These results suggest that HSC70 may be an essential factor for IBDV infection.

Molecular characterisation of infectious bursal disease virus (IBDV) isolated from commercial broiler chickens in Nile Delta

Infectious bursal disease virus (IBDV) is a highly infectious disease affecting young chickens that alters predominantly the immune system. Emergence of new variants causes severe economic losses not only in Egypt but also all over the world. For this purpose assessment of infectious bursal disease virus (IBDV) genotypes in 20 commercial broiler flocks aged 20–35 days raised in 5 provinces in the Nile Delta, Egypt (Gharbia, Dakahlya, Kafr El sheikh, Zagazig and Domietta) was carried out. All flocks were vaccinated against IBD virus. RT-PCR revealed successful amplification of 620 bp of VP2 in 17 out of 20 samples (85%). VP2 gene nucleotide sequence analysis of six IBDV isolates (F342-1, F342-2, F342-4, F342-5 and F342-7) revealed 99.1 % similarity to the Giza 2000, Giza 2008 vv, SV-G1, SV-G2, SV-G4 and SV-G5 which were very virulent IBDV strains while the isolate F342-3 was close to D78 classical vaccinal strain and Kal 2001 classical IBDV strain variant.

Baculovirus Surface Display of Immunogenic Proteins for Vaccine Development

Vaccination is an efficient way to prevent the occurrence of many infectious diseases in humans. To date, several viral vectors have been utilized for the generation of vaccines. Among them, baculovirus-categorized as a nonhuman viral vector-has been used in wider applications. Its versatile features, like large cloning capacity, nonreplicative nature in mammalian cells, and broad tissue tropism, hold it at an excellent position among vaccine vectors. In addition to ease and safety during swift production, recent key improvements to existing baculovirus vectors (such as inclusion of hybrid promoters, immunostimulatory elements, etc.) have led to significant improvements in immunogenicity and efficacy of surface-displayed antigens. Furthermore, some promising preclinical results have been reported that mirror the scope and practicality of baculovirus as a vaccine vector for human applications in the near future. Herein, this review provides an overview of the induced immune responses by baculovirus surface-displayed vaccines against influenza and other infectious diseases in animal models, and highlights the strategies applied to enhance the protective immune responses against the displayed antigens.

Recombinant Lactococcus lactis co-expressing OmpH of an M cell-targeting ligand and IBDV-VP2 protein provide immunological protection in chickens

Infectious bursal disease virus (IBDV) is a highly contagious disease that results in enormous economic losses in the global poultry sector. Lactic acid bacteria are an appealing vehicle for the safe and effective delivery of heterologous protein antigens. Oral administration of the commensal bacterium Lactococcus lactis expressing recombinant fusion proteins has been used to elicit mucosal and systemic immune responses. In this study, a Lactococcus lactis NZ3900 strain co-expressing the outer membrane protein (Omp) H of the microfold (M) cell-targeting ligand and the viral capsid protein (VP)2 antigen of IBDV was genetically engineered, and its immunopotentiating capacity as an oral and injected vaccine in chickens was evaluated. Western blotting analysis demonstrated that VP2-OmpH was expressed in the cytoplasm of cells and had high immunoreactivity. An in vivo study showed that in the absence of any adjuvant, the recombinant L. lactis VP2-OmpH strain stimulated the immune response and protected against very virulent IBDV challenge in 100% and 80% of chickens immunized by injection and oral administration, respectively. Moreover, the antiviral neutralizing antibody titers induced by injection administration were higher than those induced by oral administration. Mucosal secretory IgA titers induced by oral administration were higher than those induced by injection administration. These results suggested that the recombinant L. lactis VP2-OmpH strain is a promising candidate vaccine to prevent IBDV infection.

Viral proteins expressed in the protozoan parasite Eimeria tenella are detected by the chicken immune system

Background

Eimeria species are parasitic protozoa that cause coccidiosis, an intestinal disease commonly characterised by malabsorption, diarrhoea and haemorrhage that is particularly important in chickens. Vaccination against chicken coccidiosis is effective using wild-type or attenuated live parasite lines. The development of protocols to express foreign proteins in Eimeria species has opened up the possibility of using Eimeria live vaccines to deliver heterologous antigens and function as multivalent vaccine vectors that could protect chickens against a range of pathogens.

Results

In this study, genetic complementation was used to express immunoprotective virus antigens in Eimeria tenella. Infectious bursal disease virus (IBDV) causes Gumboro, an immunosuppressive disease that affects productivity and can interfere with the efficacy of poultry vaccination programmes. Infectious laryngotracheitis virus (ILTV) causes a highly transmissible respiratory disease for which strong cellular immunity and antibody responses are required for effective vaccination. Genes encoding the VP2 protein from a very virulent strain of IBDV (vvVP2) and glycoprotein I from ILTV (gI) were cloned downstream of 5’Et-Actin or 5’Et-TIF promoter regions in plasmids that also contained a mCitrine fluorescent reporter cassette under control of the 5’Et-MIC1 promoter. The plasmids were introduced by nucleofection into E. tenella sporozoites, which were then used to infect chickens. Progeny oocysts were sorted by FACS and passaged several times in vivo until the proportion of fluorescent parasites in each transgenic population reached ~20 % and the number of transgene copies per parasite genome decreased to < 10. All populations were found to transcribe and express the transgene and induced the generation of low titre, transgene-specific antibodies when used to immunise chickens.

Conclusions

E. tenella can express antigens of other poultry pathogens that are successfully recognised by the chicken immune system. Nonetheless, further work has to be done in order to improve the levels of expression for its future use as a multivalent vaccine vector.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1756-2) contains supplementary material, which is available to authorized users.

An optimized, highly efficient, self-assembled, subvirus-like particle of infectious bursal disease virus (IBDV)

Infectious bursal disease virus (IBDV) causes immunosuppression in young chickens, leading to increased susceptibility to other diseases and a reduction in the immune response to other vaccines. Thus, IBDV results in great economic losses to the poultry industry. The most effective method of prevention is vaccination. However, medium-virulence vaccines can cause bursal pathological damage and immunosuppression. Here, we describe a safer, self-assembled, subvirus-like particle (sVP) vaccine without a complex purification process. The IBD-VP2 gene was cloned into Pichia pastoris, and the expressed protein self-assembled into T=1 sVPs (∼23nm). Immunization experiments showed that the sVP vaccine elicited high IBDV-neutralizing antibodies in each group, and all birds survived challenge with very virulent IBDV (vvIBDV). Additionally, IBDV RNA was not detected, and sterile immunity was achieved. In conclusion, the IBD-sVP is a suitable candidate for a recombinant subunit vaccine against IBDV.

Isolation of novel variants of infectious bursal disease virus from different outbreaks in Northeast India

Infectious bursal disease virus (IBDV) is a highly infectious disease of young chicken that predominantly affects the immune system. In the present study, we are reporting first comprehensive study of IBDV outbreaks from the Northeastern part of India. Northeast India shares a porous border with four different countries; and as a rule any outbreak in the neighboring countries substantially affects the poultry population in the adjoining states. Nucleotide sequence analysis of the VP2 gene of the IBDV isolates from the Northeastern part of India suggested the extreme virulent nature of the virus. The virulent marker amino acids (A222, I242, Q253, I256 and S299) in the hypervariable region of the Northeastern isolates were found identical with the reported very virulent strains of IBDV. A unique insertion of I/L294V was recorded in all the isolates of the Northeastern India. The study will be useful in understanding the circulating pathotypes of IBDV in India.

Efficient self-assembly and protective efficacy of infectious bursal disease virus-like particles by a recombinant baculovirus co-expressing precursor polyprotein and VP4

Background

Virus-like particle (VLP) technology is considered one of the most promising approaches in animal vaccines, due to the intrinsic immunogenic properties as well as high safety profile of VLPs. In this study, we developed a VLP vaccine against infectious bursal disease virus (IBDV), which causes morbidity and mortality in chickens, by expressing a baculovirus in insect cells.

Methods

To improve the self-proteolytic processing of precursor polyprotein (PP), we constructed a recombinant baculovirus transfer vector that co-expresses PP and the VP4 protease gene of IBDV.

Results

Expression and VLP assembly of recombinant proteins and antigenicity of the VLP were examined by Western blotting, ELISA, and transmission electron microscopy. In animal experiments, vaccination with the recombinant VLP induced strong and uniform humoral immunity and provided complete protection against challenge with very virulent (vv) IBDV in SPF chickens (n = 12). As determined by the bursa of Fabricius (BF)/body weight (B/BW) ratio, the protection against post-challenge bursal atrophy was significantly higher (P < 0.001) in VLP-vaccinated birds than in non-vaccinated controls.

Conclusions

Since the protective efficacy of the VLP vaccine was comparable to that of a commercially available inactivated vaccine, the recombinant VLP merits further investigation as an alternative means of protection against vvIBD.

Construction of Recombinant Baculoviruses Expressing Infectious Bursal Disease Virus Main Protective Antigen and Their Immune Effects on Chickens

In order to overcome the limitations of conventional vaccines for infectious bursal disease virus (IBDV), we constructed recombinant dual expression system baculoviruses with VP2 and VP2/4/3, the main protective antigens of IBDV. We compared the immune effects of the baculoviruses in avian cells and detected their control effects on chickens with infectious bursal disease. We used Western blot analysis to measure VP2 protein and VP2/4/3 polyprotein expression in avian cells infected using the Bac-to-Bac baculovirus expression system. The recombinant baculoviruses were used to vaccinate specific pathogen-free chickens, which produced specific protective antibodies and strong cellular immune responses. The results of the virus challenge experiment revealed that the protective efficiency of VP2 and VP2/4/3 virus vaccines were 95.8% and 100%, respectively, both of which were higher than the vaccine group (87.5%), and significantly higher than the control group (50%). The results demonstrated that the immune effect of BV-S-ITRs-VP2/4/3 was superior to that of BV-S-ITRs-VP2. Compared with traditional attenuated vaccine and genetically engineered live vector vaccine, the dual expression viral vector vaccine has good bio-safety. The results of this study provide a foundation for the further development of poultry vaccines, in addition to providing a useful reference for developing non-replicating live vaccines against other viral diseases.

gga-miR-9* inhibits IFN production in antiviral innate immunity by targeting interferon regulatory factor 2 to promote IBDV replication

MicroRNAs (miRNAs) are small non-coding RNAs that contribute to the repertoire of host-pathogen interactions during viral infections. In the current study, miRNA analysis showed that a panel of microRNAs, including gga-miR-9*, were markedly upregulated in specific-pathogen-free (SPF) chickens upon infection with infectious bursal disease virus (IBDV); however, the biological function of gga-miR-9* during viral infection remains unknown. Using a TCID50 assay, it was found that ectopic expression of gga-miR-9* significantly promoted IBDV replication. In turn, gga-miR-9* negatively regulated IBDV-triggered type I IFN production, thus promoting IBDV replication in DF-1 cells. Bioinformatics analysis indicates that the 3' untranslated region (UTR) of interferon regulatory factor 2 (IRF2) has two putative binding sites for gga-miR-9*. Targeting of IRF2 3'UTR by gga-miR-9* was determined by luciferase assay. Functional overexpression of gga-miR-9*, using gga-miR-9* mimics, inhibited IRF2 mRNA and protein expression. Transfection of the gga-miR-9* inhibitor abolished the suppression of IRF2 protein expression. Furthermore, IRF2 knockdown mediated the enhancing effect of gga-miR-9* on the type I IFN-mediated antiviral response. These findings indicate that inducible gga-miR-9* feedback negatively regulates the host antiviral innate immune response by suppressing type I IFN production via targeting IRF2.

Genetic characterization of infectious bursal disease viruses associated with gumboro outbreaks in commercial broilers from asyut province, egypt

Ten infectious bursal disease virus (IBDV) field strains were isolated from 15 broiler flocks located in various parts of Asyut, Egypt. Seven strains were subjected to comparative sequencing and phylogenetic analyses to help provide optimal control program for protection against IBDV infection. Sequence analysis of a 530 bp hypervariable region in the VP2 gene revealed that the rate of identity and homology was around 95.6~99.1%. Sequence characterization revealed the 7 strains identified as vvIBDV with the four amino acids residues typical of vvIBDV (242I, 256I, 294I, 299S). The BURSA-VAC vaccine was the nearest vaccine in sequence similarity to the local examined IBDV strains followed by CEVACIBDL then Bursine plus and Nobilis Gumboro indicating its probable success in the face of incoming outbreaks when using these vaccines. Phylogenetic analysis revealed that the presence of three clusters for the examined strains and are grouped with reference very virulent IBDVs of European and Asian origin (Japanese and Hong Kong) strains suggesting the different ancestors of our isolates. The antigenic index showed a number of changes on the major and minor hydrophilic antigenic peaks of the virus surface structures indicating a new genetic evolution of the surface structure epitopes that may lead to vaccination failure and reemergence of the disease.

Cross-protective efficacy of bivalent recombinant baculoviral vaccine against heterologous influenza H5N1 challenge

The present study demonstrates the cross-protective efficacy of baculovirus displayed HAs of A/Indonesia/669/06 and A/Anhui/01/05 against heterologous H5N1 challenges in a mouse model. Mice orally or subcutaneously immunized with live bivalent-BacHA vaccine significantly induced higher HA-specific humoral and cellular immune responses when compared with inactivated bivalent-BacHA. In addition, oral administration of live bivalent-BacHA vaccine was able to induce significant level of antigen-specific mucosal IgA levels. Microneutralization assay indicated that live bivalent-BacHA vaccine was able to induce strong cross-clade neutralization titer against distinct H5N1 clades (1, 2.1.3, 2.2.1.1, 2.3.2, 2.3.4, 4, 7 and 9). The production of both interferon-gamma (IFN-γ) and interleukin-4 (IL-4) by splenocytes from vaccinated mice indicated that mice vaccinated orally or subcutaneously with live bivalent-BacHA stimulated both IFN-γ secreting Th1 cells and IL-4 secreting Th2 cells, whereas mice immunized subcutaneously with inactive adjuvanted bivalent-BacHA stimulated only IL-4 secreting Th2 cells. Cross-protective immunity study also showed that mice immunized either orally or subcutaneously with live bivalent-BacHA were completely protected against 5MLD50 of clade 1 and clade 2.2.1.1 H5N1 viral infections. The protective immune response elicited by bivalent-BacHA vaccine against H5N1 variants demonstrates the possibility of protection against a broad range of H5N1 strains.

Molecular characterization and phylogenetic analysis of infectious bursal disease viruses isolated from chicken in South China in 2011

Infectious bursal disease virus (IBDV) is a double-stranded RNA virus that causes immunosuppressive disease in young chickens. Thousands of cases of IBDV infection are reported each year in South China, and these infections can result in considerable economic losses to the poultry industry. To monitor variations of the virus during the outbreaks, 30 IBDVs were identified from vaccinated chicken flocks from nine provinces in South China in 2011. VP2 fragments from different virus strains were sequenced and analyzed by comparison with the published sequences of IBDV strains from China and around the world. Phylogenetic analysis of hypervariable regions of the VP2 (vVP2) gene showed that 29 of the isolates were very virulent (vv) IBDVs, and were closely related to vvIBDV strains from Europe and Asia. Alignment analysis of the deduced amino acid (aa) sequences of vVP2 showed the 29 vv isolates had high uniformity, indicated low variability and slow evolution of the virus. The non-vvIBDV isolate JX2-11 was associated with higher than expected mortality, and had high deduced aa sequence similarity (99.2 %) with the attenuated vaccine strain B87 (BJ). The present study has demonstrated the continued circulation of IBDV strains in South China, and emphasizes the importance of reinforcing IBDV surveillance.

Protective vaccination against infectious bursal disease virus with whole recombinant Kluyveromyces lactis yeast expressing the viral VP2 subunit

Here we report on vaccination approaches against infectious bursal disease (IBD) of poultry that were performed with complete yeast of the species Kluyveromyces lactis (K. lactis). Employing a genetic system that enables the rapid production of stably transfected recombinant K. lactis, we generated yeast strains that expressed defined quantities of the virus capsid forming protein VP2 of infectious bursal disease virus (IBDV). Both, subcutaneous as well as oral vaccination regiments with the heat-inactivated but otherwise untreated yeast induced IBDV-neutralizing antibodies in mice and chickens. A full protection against a subsequent IBDV infection was achieved by subcutaneous inoculation of only milligram amounts of yeast per chicken. Oral vaccination also generated protection: while mortality was observed in control animals after virus challenge, none of the vaccinees died and ca. one-tenth were protected as indicated by the absence of lesions in the bursa of Fabricius. Recombinant K. lactis was thus indicated as a potent tool for the induction of a protective immune response by different applications. Subcutaneously applied K. lactis that expresses the IBDV VP2 was shown to function as an efficacious anti-IBD subunit vaccine.

Baculovirus as a vaccine vector

Baculovirus is extensively utilized as an excellent tool for production of recombinant protein in insect cells. Baculovirus infects insects in nature and is non-pathogenic to humans. In addition to insect cells, baculovirus is capable of transducing a broad range of animal cells. Due to its biosafety, large cloning capacity, low cytotoxicity, and non-replication nature in the transduced cells as well as the ease of manipulation and production, baculovirus has been utilized as RNA interference mediators, gene delivery vectors, and vaccine vectors for a wide variety of applications. This article focuses on the utilization of baculoviruses as vaccine vectors to prepare antigen or subunit vaccines.

Baculovirus as a PRRSV and PCV2 bivalent vaccine vector: baculovirus virions displaying simultaneously GP5 glycoprotein of PRRSV and capsid protein of PCV2

The GP5 glycoprotein of PRRSV is the main target for inducing neutralizing antibodies and protective immunity in the natural host. The capsid (Cap) protein is the major immunogenic protein and associated with the production of PCV2-specific neutralizing antibodies. In the present study, one genetic recombinant baculovirus BacSC-Dual-GP5-Cap was constructed. This virus displays simultaneously histidine-tagged GP5 and Cap proteins with the baculovirus glycoprotein gp64 TM and CTD on the virion surface as well as the surface of the virus-infected cells. After infection, the GP5 and Cap proteins were expressed and anchored simultaneously on the plasma membrane of Sf-9 cells, as revealed by Western blot and confocal microscopy. This report demonstrated first that both GP5 and Cap proteins were displayed successfully on the viral surface, revealed by immunogold electron microscopy. Vaccination of swine with recombinant baculovirus BacSC-Dual-GP5-Cap elicited significantly higher GP5 and Cap ELISA antibody titers in swine than the control groups. Virus neutralization test also showed that serum from the BacSC-Dual-GP5-Cap treated swine had significant levels of virus neutralization titers. Lymphocyte proliferation responses could be induced in swine immunized with BacSC-Dual-GP5-Cap than the control groups. These findings demonstrate that the BacSC-Dual-GP5-Cap bivalent subunit vaccine can be a potential vaccine against PRRSV and PCV2 infections.