A simple selection system for construction of recombinant gD-negative pseudorabies virus as a vaccine vector

Assessment of immunization regimens of duck Riemerella anatipestifer vaccines

AIMS

Riemerella anatipestifer infections of goslings and ducklings can result in high mortality. Since there are at least 21 serotypes of R. anatipestifer, cross-protection is an important goal for vaccine development.

METHODS AND RESULTS

In this study, we evaluated the immunostimulatory effect of different immunization regimens - the traditional inactivated vaccine vs prime-boost regimens using DNA and protein subunit vaccines (DNA+subunit, subunit+subunit, subunit+inactivated and DNA+DNA). Results showed that, when compared to the inactivated vaccine, prime-boost regimens induced higher and up to 16-week longer lasting levels of antibody responses, significantly elevated the percentage of the cytotoxic CD8⁺ T cell and higher expression levels of IFN-γ, IL-6 and IL-12 mRNAs. Furthermore, as an indication of cross-protection, sera from prime-boost regimens were able to recognize lysates of R. anatipestifer serotypes 1, 2 and 6.

CONCLUSIONS

Prime-boost regimens especially DNA-prime and protein-boost, induce strong long-term immune response and may prove protective for breeder ducks requiring long-term protection.

SIGNIFICANCE AND IMPACT OF THE STUDY

It is worth mentioning that the subunit+inactivated regimen group also elicited strong immune response. The cost of this regimen may only be half of the other prime-boost regimens, making this subunit + inactivated combination an attractive option.

A DNA priming and protein boosting immunization scheme to augment immune responses against parvovirus in ducks

AIMS

To evaluate the effect of a DNA priming and protein boosting immunization scheme in ducks.

METHODS AND RESULTS

Pekin ducks were immunized with pTCY/VP2 DNA vaccine; on day 14 (D14) after primary immunization, the ducks were boosted with either the same vaccine (DNA + DNA) or the rVP2 vaccine (DNA + rVP2). CpG oligodeoxynucleotides containing three copies of GACGTT motifs were used as the adjuvant in the vaccines. Compared with unimmunized controls, both immunization schemes significantly increased the titre of antigen-specific antibodies, lymphocyte proliferation index, percentage of CD4⁺ and CD8⁺ cells in peripheral blood mononuclear cells (PBMCs) and mRNA expression of interferon (IFN)-α, IFN-γ, interleukin (IL)-6 and IL-12 in antigen-stimulated PBMCs. Furthermore, compared with the DNA + DNA homologous scheme, the DNA + rVP2 heterologous scheme significantly increased lymphocyte proliferation, percentage of CD4⁺ and CD8⁺ cells in PBMCs and upregulation of mRNA expression of cytokines 2 weeks after the boost (D28).

CONCLUSIONS

The DNA + rVP2 immunization scheme enhanced immune responses, mainly Th1 type, against parvovirus in ducks.

SIGNIFICANCE AND IMPACT OF THE STUDY

The DNA priming and protein boosting heterologous immunization strategy can be applied to develop vaccines against viral infections in ducks. It can potentially be used in breeding ducks because of long-term immunity may confer protection for ducklings.

A Thymidine Kinase recombinant protein-based ELISA for detecting antibodies to Duck Plague Virus

BACKGROUND

Duck plague virus (DPV) is the causative agent of Duck Plague (DP) that causes significant morbidity and mortality throughout duck-producing areas of the world. The diagnosis of DP currently relies on the use of live or inactivated whole DPV virion as antigens in ELISA, but it is too laborious and expensive for routine application, and it is still difficult to get purified DPV virion with current technology.

RESULTS

In this study, we describe the expression and purification of a recombinant Thymidine Kinase (TK) protein which makes antigen in an in-house developed, optimized and standardized ELISA. The specificity of the optimized TK-ELISA was evaluated by antisera against Duck Plague Virus (DPV), Duck Hepatitis B Virus (DHBV), Duck Hepatitis Virus (DHV), Riemerella Anatipestifer(R. A), Escherichia coli (E. coli) and Salmonella anatum (S. anatum). Only antisera against DPV yielded a specific and strong signal. In order to determine the sensitivity of the TK-ELISA, a panel of diluted sera was tested, and the minimum detection limit of 1:2560 (OD450 nm = 0.401) was obtained according to the endpoint cut-off (0.2438). The repeatability and reproducibility under the experimental conditions demonstrates a low variability (P > 0.05). The suspected sera samples (n = 30) were determined by TK-ELISA and the positive rate is 90% (27/30), and the TK-ELISA showed 83.33% (22+3/30) coincidence rate with the Serum Neutralization Test (SNT) and 90% (24+3/30) coincidence rate with the whole DPV virion based-ELISA (DPV-ELISA). When defining the dynamics of antibody response to attenuated live DPV vaccine, the maximum antibodies is reached after 4 weeks.

CONCLUSIONS

The results suggest that the TK-ELISA provides high specificity, sensitivity, repeatability and reproducibility for detection of anti-DPV antibodies in duck sera, and has the potential to be much simpler than DPV-ELISA and SNT for the sera epidemiological investigation.

Targeting the porcine immune system--particulate vaccines in the 21st century

During the last decade, the propagation of immunological knowledge describing the critical role of dendritic cells (DC) in the induction of efficacious immune responses has promoted research and development of vaccines systematically targeting DC. Based on the promise for the rational design of vaccine platforms, the current review will provide an update on particle-based vaccines of both viral and synthetic origin, giving examples of recombinant virus carriers such as adenoviruses and biodegradable particulate carriers. The viral carriers carry pathogen-associated molecular patterns (PAMP), used by the original virus for targeting DC, and are particularly efficient and versatile gene delivery vectors. Efforts in the field of synthetic vaccine carriers are focussing on decorating the particle surface with ligands for DC receptors such as heparan sulphate glycosaminoglycan structures, integrins, Siglecs, galectins, C-type lectins and toll-like receptors. The emphasis of this review will be placed on targeting the porcine immune system, but reference will be made to advances with murine and human vaccine delivery systems where information on DC targeting is available.

Tumor-selective replication of an oncolytic adenovirus carrying oct-3/4 response elements in murine metastatic bladder cancer models

PURPOSE

Oncolytic adenoviruses are attractive therapeutics for cancer because they selectively replicate in tumors. However, targeting tumor metastasis remains a major challenge for current virotherapy for cancer. Oct-3/4 is specifically expressed in embryonic stem cells and tumor cells. Oct-3/4 highly expressed in cancer cells may be a potential target for cancer therapy. We developed an E1B-55 kDa-deleted adenovirus, designated Ad.9OC, driven by nine copies of Oct-3/4 response element for treating Oct-3/4-expressing metastatic bladder cancer.

EXPERIMENTAL DESIGN

We examined the expression of Oct-3/4 in human bladder tumor tissues and bladder cancer cell lines. We also evaluated the cytolytic and antitumor effects of Ad.9OC on bladder cancer cells in vitro and in vivo.

RESULTS

Oct-3/4 expression was detected in bladder cancer cell lines, as well as in human bladder tumor tissues. Notably, Oct-3/4 expression was higher in metastatic compared with nonmetastatic bladder cancer cells. Ad.9OC induced higher cytolytic activity in metastatic bladder cancer cells than in their nonmetastatic counterparts, whereas it did not cause cytotoxicity in normal cells. Pharmacologic and short hairpin RNA-mediated Oct-3/4 inhibition rendered bladder cancer cells more resistant to Ad.9OC-induced cytolysis. Replication of Ad.9OC was detected in murine bladder cancer cells and bladder tumor tissues. We also showed the effectiveness of Ad.9OC for treating bladder cancer in subcutaneous, as well as metastatic, bladder tumor models.

CONCLUSIONS

Ad.9OC may have therapeutic potential for treating Oct-3/4-expressing tumors. Especially, metastatic bladder tumors are good target for Ad.9OC treatment. Because Oct-3/4 is expressed in a broad spectrum of cancers, Ad.9OC may be broadly applicable.

Development of a Conditionally Replicating Pseudorabies Virus for HER-2/neu-overexpressing Bladder Cancer Therapy

Overexpression of the HER-2/neu oncogene, a frequent molecular event in a variety of cancers including bladder cancer, is associated with tumor progression and poor prognosis. Therapeutic strategies to targeting HER-2/neu-overexpressing cancer cells have shown promise. Pseudorabies virus (PrV), a herpesvirus of swine, may be exploited as an oncolytic agent for human cancer. Herein, we generated a conditionally replicating glycoprotein E-defective PrV mutant carrying glycoprotein D and herpes simplex virus type 1 thymidine kinase genes, which are essential for viral entry and replication, under the transcriptional control of the HER-2/neu promoter. The recombinant PrV, designated YP2, selectively replicated in and lysed HER-2/neu-overexpressing human bladder, mouse bladder, and hamster oral cancer cells in vitro. Notably, YP2 retarded MBT-2 bladder tumor growth in mice by more than 50% and more than half of the mice survived for over 50 days, whereas all the control mice survived less than 30 days. Taken together, our results suggest that YP2 may have therapeutic potential for the treatment of invasive bladder cancer. Furthermore, because HER-2/neu is overexpressed in a broad spectrum of cancers, this conditionally replicating PrV may be broadly applicable.

Mitochondrial ribosomal protein S36 delays cell cycle progression in association with p53 modification and p21WAF1/CIP1 expression

Ribosomal biogenesis is correlated with cell cycle, cell proliferation, cell growth and tumorigenesis. Some oncogenes and tumor suppressors are involved in regulating the formation of mature ribosome and affecting the ribosomal biogenesis. In previous studies, the mitochondrial ribosomal protein L41 was reported to be involved in cell proliferation regulating through p21(WAF1/CIP1) and p53 pathway. In this report, we have identified a mitochondrial ribosomal protein S36 (mMRPS36), which is localized in the mitochondria, and demonstrated that overexpression of mMRPS36 in cells retards the cell proliferation and delays cell cycle progression. In addition, the mMRPS36 overexpression induces p21(WAF1/CIP1) expression, and regulates the expression and phosphorylation of p53. Our result also indicate that overexpression of mMRPS36 affects the mitochondrial function. These results suggest that mMRPS36 plays an important role in mitochondrial ribosomal biogenesis, which may cause nucleolar stress, thereby leading to cell cycle delay.

Novel strategy for generation and titration of recombinant adeno-associated virus vectors

Recombinant adeno-associated virus (rAAV) vectors have many advantages for gene therapeutic applications compared with other vector systems. Several methods that use plasmids or helper viruses have been reported for the generation of rAAV vectors. Unfortunately, the preparation of large-scale rAAV stocks is labor-intensive. Moreover, the biological titration of rAAV is still difficult, which may limit its preclinical and clinical applications. For this study, we developed a novel strategy to generate and biologically titrate rAAV vectors. A recombinant pseudorabies virus (PrV) with defects in its gD, gE, and thymidine kinase genes was engineered to express the AAV rep and cap genes, yielding PS virus, which served as a packaging and helper virus for the generation of rAAV vectors. PS virus was useful not only for generating high-titer rAAV vectors by cotransfection with an rAAV vector plasmid, but also for amplifying rAAV stocks. Notably, the biological titration of rAAV vectors was also feasible when cells were coinfected with rAAV and PS virus. Based on this strategy, we produced an rAAV that expresses prothymosin alpha (ProT). Expression of the ProT protein in vitro and in vivo mediated by rAAV/ProT gene transfer was detected by immunohistochemistry and a bioassay. Taken together, our results demonstrate that the PrV vector-based system is useful for generating rAAV vectors carrying various transgenes.