High Levels Of Protective Immunity Research Articles

Display of Heterologous Proteins in Bacillus Subtilis Biofilms for Enteric Immunization.

One of the foremost goals in vaccine development is the design of effective, heat-stable vaccines that simplify the distribution and delivery while conferring high levels of protective immunity. Here, we describe a method for developing a live, oral vaccine that relies on the biofilm-forming properties of the spore-former bacterium Bacillus subtilis. The amyloid protein TasA is an abundant component of the extracellular matrix of the biofilms formed by B. subtilis that can be genetically fused to an antigen of interest. Spores of the recombinant strain are then prepared and applied via the oral route in an animal model. Due to the intrinsic resistance of the spores, they can bypass the stomach barrier, germinate, and subsequently colonize the gut, where they develop into biofilms, expressing the antigen of interest. We describe here the steps necessary to produce spores, immunization, and downstream analysis of the vaccine efficacy.

Development of a recombinant H9N2 influenza vaccine candidate against the Y280 lineage field virus and its protective efficacy

Since June 2020, a new H9N2 virus of the Y280 lineage has been epidemic in Korea. Initially, a Korean commercial vaccine against the Y280 and Y439 lineages of H9N2 was evaluated for use in SPF chickens. A single vaccination did not protect chickens against virus of the Y280 lineage, with no significant reduction in virus shedding and a 37.5% inhibition in virus recovery rate in cecal tonsil. rgHS314 was selected as a vaccine candidate, showing immunogenicity in SPF chickens, and was highly productive in eggs. Moreover, rgHS314 protected with high levels of protective immunity and significantly reduced virus shedding, with 100% and 83.3% inhibition of virus recovery in the cecal tonsil against homologous and heterologous challenge viruses, respectively. Taken together, these data suggest that a single vaccination with this recombinant vaccine candidate could elicit cross-reactive immune responses capable of protecting chickens against H9N2 viruses of the Y439 and Y280 lineages.

Hybrid immunity: the immune response of COVID-19 survivors to vaccination

Hybrid immunity can become a turning-point opportunity to defeat the infection in context with the current pandemic scenario. Adopting policies aligned with the data mentioned above may be particularly beneficial for regions like Latin America. While this region shares only ~5% of the world population, it accumulates +16% of the ~200 million COVID-19 total cases, so far reported1. Acknowledging the reduced diagnostic capabilities of these countries, this entire area is probably one of the most affected globally, leading to one of the more numerous populations of convalescent people. From both an economic and pharmacological perspective, applying a one-dose regime of pertinent vaccines to convalescent individuals is sustainable5. As COVID-19 survivors may need just one vaccination to achieve high levels of protective immunity, massive antibody screening for SARS-CoV-2 spike antibodies could help prioritize and free up doses, optimize vaccine supply efficiency, and surpass problems linked to the current vaccine manufacturing bottleneck

Study on the immunity protection of 14-3-3–MPLA–liposome vaccine against cystic echinococcosis in mice

The study aims to investigate the protective immunity against Echinococcus granulosus in mice immunized with14-3-3–MPLA–liposome vaccine. ICR (Institute of Cancer Research) mice were subcutaneously immunized three times with 14-3-3–MPLA–liposome vaccine, followed by the challenge with Echinococcus granulosus protoscoleces intraperitoneally and then sacrificed after six months of post-challenge. The levels of IL-4, and IFN-γ were measured by ELISA. The rate of reduced hydatid cyst and the levels of IgE, IgG and IgG subclasses in sera were examined. The result showed that mice vaccinated with14-3-3–MPLA–liposome vaccine and challenged with protoscoleces revealed significant protective immunity of 95.07%. ELISA analysis indicated that the immunized mice generated specific high levels of IgG and the prevailing isotypes of IgG were IgG1 and IgG2a. The level of IFN-γ increased significantly in the vaccinated mice whereas there was no significant difference in IL-4 levels between vaccinated and control mice. It is concluded that the14-3-3–MPLA–liposome vaccine could induce a high level of protective immunity to prevent cystic echinococcosis. The MPLA and liposome are promising vaccine adjuvant and delivery system.

Pre-clinical evaluation of a P. berghei-based whole-sporozoite malaria vaccine candidate

Whole-sporozoite vaccination/immunization induces high levels of protective immunity in both rodent models of malaria and in humans. Recently, we generated a transgenic line of the rodent malaria parasite P. berghei (Pb) that expresses the P. falciparum (Pf) circumsporozoite protein (PfCS), and showed that this parasite line (PbVac) was capable of (1) infecting and developing in human hepatocytes but not in human erythrocytes, and (2) inducing neutralizing antibodies against the human Pf parasite. Here, we analyzed PbVac in detail and developed tools necessary for its use in clinical studies. A microbiological contaminant-free Master Cell Bank of PbVac parasites was generated through a process of cyclic propagation and clonal expansion in mice and mosquitoes and was genetically characterized. A highly sensitive qRT-PCR-based method was established that enables PbVac parasite detection and quantification at low parasite densities in vivo. This method was employed in a biodistribution study in a rabbit model, revealing that the parasite is only present at the site of administration and in the liver up to 48 h post infection and is no longer detectable at any site 10 days after administration. An extensive toxicology investigation carried out in rabbits further showed the absence of PbVac-related toxicity. In vivo drug sensitivity assays employing rodent models of infection showed that both the liver and the blood stage forms of PbVac were completely eliminated by Malarone® treatment. Collectively, our pre-clinical safety assessment demonstrates that PbVac possesses all characteristics necessary to advance into clinical evaluation.

SjCRT, a recombinant Schistosoma japonicum calreticulin, induces maturation of dendritic cells and a Th1-polarized immune response in mice

BackgroundIt is well known that immunization of radiation-attenuated (RA) schistosoma cercariae or schistosomula can induce high levels of protective immunity against schistosoma cercariae reinfection in many animals. Many studies have shown that the Th1 cellular immune response is crucial for the protective effect elicited by RA schistosomula. However, the molecular mechanism of this strong protective immunity remains unclear.MethodsThe expression profiles of Schistosoma japonicum calreticulin (SjCRT) in RA and normal schistosoma-derived cells were investigated by flow cytometry. The effect of recombinant SjCRT (rSjCRT) on mouse dendritic cells (DCs) was determined by FACS, ELISA and RT-PCR analysis. We also analyzed the effects of SjCRT on the activation of spleen cells from mice immunized with rSjCRT by detecting lymphocyte proliferation and the cytokine profiles of splenocytes.ResultsWe found that the expression level of SjCRT in the cells from RA larvae was significantly higher than that in cells from normal schistosomula at early stages of development (day 4). The results of effect of rSjCRT on mouse DCs showed that rSjCRT could induce phenotypic and functional maturation of DCs, and SjCRT bound to the surface of DCs through the CD91 receptor and could be engulfed by DCs. The results of activation of splenocytes from mice immunized with rSjCRT also demonstrate that rSjCRT can effectively stimulate the proliferative response of splenic lymphocytes, elicit splenocytes from immunized mice to secrete high levels of IFN-γ, TNF-α and IL-4, and activate CD4+ T cells to produce high levels of IFN-γ.ConclusionSjCRT is one of the immunostimulatory molecules released from RA schistosomula cells, might play a crucial role in conferring a Th1-polarized immune response induced by RA cercariae/schistosomula in mice, and is a candidate molecule responsible for the high levels of protective immunity induced by RA schistosomula.

Protection of White Leghorn chickens by U.S. emergency H5 vaccination against clade 2.3.4.4 H5N2 high pathogenicity avian influenza virus.

During December 2014-June 2015, the U.S. experienced a high pathogenicity avian influenza (HPAI) outbreak caused by clade 2.3.4.4 H5Nx Goose/Guangdong lineage viruses with devastating consequences for the poultry industry. Three vaccines, developed based on updating existing registered vaccines or currently licensed technologies, were evaluated for possible use: an inactivated reverse genetics H5N1 vaccine (rgH5N1) and an RNA particle vaccine (RP-H5), both containing the hemagglutinin gene of clade 2.3.4.4 strain, and a recombinant herpesvirus turkey vectored vaccine (rHVT-H5) containing the hemagglutinin gene of clade 2.2 strain. The efficacy of the three vaccines, alone or in combination, was assessed in White Leghorn chickens against clade 2.3.4.4 H5N2 HPAI virus challenge. In Study 1, single (rHVT-H5) and prime-boost (rHVT-H5+rgH5N1 or rHVT-H5+RP-H5) vaccination strategies protected chickens with high levels of protective immunity and significantly reduced virus shedding. In Study 2, single vaccination with either rgH5N1 or RP-H5 vaccines provided clinical protection in adult chickens and significantly reduced virus shedding. In Study 3, double rgH5N1 vaccination protected adult chickens from clinical signs and mortality when challenged 20weeks post-boost, with high levels of long-lasting protective immunity and significantly reduced virus shedding. These studies support the use of genetically related vaccines, possibly in combination with a broad protective priming vaccine, for emergency vaccination programs against clade 2.3.4.4 H5Nx HPAI virus in young and adult layer chickens.

Induction of protective immunity against experimental Eimeria tenella infection using serum exosomes

Avian coccidiosis is caused by Eimeria, a unicellular, apicomplexan protist which primarily infects intestinal epithelia resulting in nutrient malabsorption and reduced growth of commercial poultry. Vaccination of chickens with exosomes isolated from antigen presenting cells containing parasite antigens (Ags) represents a promising alternative strategy to control avian coccidiosis, but is restricted in its commercial application due to limitations on production scale-up for mass immunization programs. Here, we report the biochemical and physiologic characteristics of exosomes derived from serum of Eimeria tenella-infected chickens and their feasibility for inducing protective immunity to experimental coccidiosis. Exosomes isolated from the serum of E. tenella-infected chickens contained a subset of protein Ags found in the intact parasite. Serum-derived exosomes containing these E. tenella Ags localized to the intestine and spleen following intramuscular injection into naïve chickens. In vitro ELISPOT assays revealed increased numbers of IL-2-, IL-4-, IL-6-, and IFN-γ-secreting cells in the intestine and spleen of exosome-administered chickens, compared with vehicle controls. Pre-immunization of chickens with serum exosomes from E. tenella-infected chickens increased both body weight gain and feed conversion efficiency, and reduced both fecal parasite shedding and gut lesion scores following parasite infection, compared with vehicle controls. Finally, immunization with CD80+ serum exosomes stimulated greater numbers of cytokine-producing cells, and higher levels of protective immunity to E. tenella infection, compared with CD80− exosomes. These results suggest the possibility of producing an effective, parasite-free vaccine against avian coccidiosis under field conditions using serum-derived CD80+ exosomes containing parasite Ags.

Brucella melitensis 16MΔTcfSR as a potential live vaccine allows for the differentiation between natural and vaccinated infection.

Brucellosis is a zoonotic disease that poses a serious threat to public health and safety. Although the live attenuated vaccines targeting brucellosis, such as M5-90, are effective, there are a number of drawbacks to their use. For example, the vaccines are unable to differentiate between the natural and vaccinated forms of the infection, and these vaccines have also been shown to cause abortion in pregnant animals. Therefore, a safer and more potent vaccine is required. In the present study, a B. melitensis 16M TcfSR promoter mutant (16MΔTcfSR) was constructed in an attempt to overcome these drawbacks. A TcfSR mutant was derived from B. melitensis 16M and tested for virulence and protection efficiency. Levels of immuoglobulin G (IgG), and cytokine production were determined. In addition, TcfS was assessed as a diagnostic marker for brucellosis. The survival capacity of the 16MΔTcfSR mutant was shown to be attenuated in the RAW 264.7 murine macrophage cell line and BALB/c mice, and the vaccination was shown to induce a high level of protective immunity in BALB/c mice. In addition, the 16MΔTcfSR vaccination elicited an anti-Brucella-specific IgG response and induced the secretion of interferon-γ. Thus, the TcfS antigen allowed for the serological differentiation between the natural and vaccinated infection in animals. In conclusion, the results demonstrated that the 16MΔTcfSR mutant was attenuated in murine macrophage cells and BALB/c mice; therefore, 16MΔTcfSR is a potential candidate for a live attenuated vaccine against B. melitensis infection.

SjHSP70, a recombinant Schistosoma japonicum heat shock protein 70, is immunostimulatory and induces protective immunity against cercarial challenge in mice.

High levels of protective immunity can be induced in different animals immunized with radiation-attenuated (RA) Schistosoma cercariae or schistosomula. However, the schistosome-derived molecules responsible for the strong protective effect elicited by RA schistosome larvae have not been identified or characterized. The 70-kDa heat shock proteins of schistosomes are considered major immunogens, and may play an important role in stimulating high levels of innate and adaptive immune responses in an RA schistosome vaccine model. Here, we demonstrate the immunobiological functions of Schistosoma japonicum heat shock protein 70 (SjHSP70) by investigating its expression profile in RA-schistosomula-derived cells, evaluating the protection induced by recombinant SjHSP70 (rSjHSP70) against cercarial challenge, and assaying the humoral and cellular immune responses to rSjHSP70 in BALB/c and C57BL/6 mice. The expression of SjHSP70 on the surfaces of cells from RA or normal schistosomula was determined with flow cytometry. Its expression was significantly higher on early RA schistosomula cells than on the cells from normal parasites. The protection afforded both BALB/c and C57BL/6 mice vaccinated with rSjHSP70 alone, rSj22.6 (a membrane-anchoring protein of S. japonicum) alone, or a combination of rSj22.6 and rSjHSP70 without adjuvant was evaluated. rSjHSP70 alone induced the highest protective effect against S. japonicum cercarial challenge, followed by the rSj22.6 plus rSjHSP70 combination and then rSj22.6 alone, in both mouse strains. Like ISA206 adjuvant, rSjHSP70 enhanced the protective efficacy induced by rSj22.6 in the C57BL/6 mouse strain. Antigen-specific IgG1 and IgG2a responses were detected with enzyme-linked immunosorbent assays in mice immunized with rSjHSP70 alone, rSj22.6 alone, or the rSj22.6 plus rSjHSP70 combination. Immunization with rSjHSP70 or the rSj22.6 plus rSjHSP70 combination induced mixed Th1/Th2-type antibody responses in BALB/c mice and a Th2-type antibody response in C57BL/6 mice. The profiles of cytokine production by splenic lymphocytes in both strains of mice immunized with the antigens described above were detected in vitro using a Cytometric Bead Array. The profiles of the proinflammatory cytokines interferon γ, tumor necrosis factor α, interleukin 6 (IL-6), and IL-17A and the regulatory cytokine IL-10 induced by the rSj22.6 plus rSjHSP70 combination were similar to those induced by rSj22.6 emulsified with the ISA206 adjuvant control. Like the ISA206 adjuvant, rSjHSP70 protein enhanced the proinflammatory and Th2-type or regulatory cytokine production induced by the rSj22.6 antigen. These results indicate that SjHSP70 is exposed on the surfaces of cells from RA schistosomula, and that rSjHSP70 protein is a promising protective antigen with a potential adjuvant function. Thus, SjHSP70 protein might play a key role in the protective immunity elicited by the RA schistosome vaccine.

Improvement of a DNA vaccine against BoHV-1 using chemical and molecular adjuvants

Improvement of a DNA vaccine against BoHV-1 using chemical and molecular adjuvants

Protection of Nile tilapia ( Oreochromis niloticus L.) against Streptococcus agalactiae following immunization with recombinant FbsA and α-enolase

Abstract Streptococcus agalactiae , a Gram-positive bacterium, can infect a variety of fish species reared in marine and freshwater aquaculture facilities, which can result in serious economic losses. We identified, expressed, and purified, two putative cell surface proteins – fibrinogen-binding proteins A (FbsA) and α-enolase – from S. agalactiae THN strain, and determined their roles as subunit vaccines to protect tilapia against S. agalactiae infections. We also investigated the effects of both proteins on the respiratory burst activity of blood leukocytes and on serum lysozyme activity. Specific antibody titers were carried out on a weekly basis. Results indicated that both putative proteins shared similar structure characteristics with those from other bacterium species. Using the Escherichia coli BL21 system, we expressed and purified recombinant FbsA (rFbsA) and α-enolase (rEnolase). Following immunization of tilapia we found that both recombinant proteins can confer protection against S. agalactiae , with the relative percentage survival (RPS) of 40.63 ± 17.21% and 62.50 ± 18.75%, respectively. Inactivated S. agalactiae and adjuvant control groups produced RPS of 93.75 ± 5.41% and 16.67 ± 17.21%, respectively. The respiratory burst activity and lysozyme activity were significantly enhanced in groups rFbsA and rEnolase when compared with that of the PBS control. The serum-specific antibody titer against rFbsA or rEnolase was also increased and we found that rFbsA induced a higher antibody titer, post immunization. These results indicated that, although both FbsA and α-enolase can regulate the host's innate immune responses and specific antibody responses, α-enolase can also function as a candidate vaccine antigen, and can provide a high level of protective immunity against S. agalactiae . We also noted that different proteins were associated with different levels of protection.

Echinococcus Granulosus 14-3-3 Protein: A Potential Vaccine Candidate Against Challenge with Echinococcus Granulosus in Mice

ObjectiveTo investigate the protective immunity against Echinococcus granulosus in mice immunized with rEg14-3-3. MethodsICR mice were subcutaneously immunized three times with rEg14-3-3, followed by the challenge with Echinococcus granulosus protoscoleces intraperitoneally and then sacrificed after six months of post-challenge to detect the proliferation of splenocytes by MTT assay, and to measure the secretion of IL-2, IL-4, IL-10, and IFN-γ by ELISA. The rate of reduced hydatid cyst and the levels of IgE, IgG and IgG subclasses in sera were examined. ResultsMice vaccinated with rEg14-3-3 and challenged with protoscoleces revealed significant protective immunity of 84.47%. ELISA analysis indicated that the immunized mice generated specific high levels of IgG and the prevailing isotypes of IgG were IgG1 and IgG2a. Splenocytes from mice immunized with rEg14-3-3 showed a significant proliferation response. The secretion of IFN-γ and IL-2 increased significantly in the vaccinated mice whereas there was no significant difference in IL-4 and IL-10 levels between vaccinated and control mice. ConclusionThe results indicate that the rEg14-3-3 vaccine could induce a high level of protective immunity as a promising vaccine candidate to prevent cystic echinococcosis.

The immunogenicity and safety of DTaP interchangeable immunization among Korean children

Since the production of various vaccine formulations by different pharmaceutical companies and interruptions in vaccine supply cannot be fully regulated, problems caused by DTaP interchangeability may occur. However, the interchangeability data on the first primary series of DTaP vaccination have not been well described. In this study we investigated immunogenicity and overall safety of diphtheria, tetanus, pertussis in children who had adventitiously received an interchangeable DTaP vaccination. A total 97 of participants were enrolled (mean age, 11 months). High immunogenicity (1.8±0.4IU/mL, 100%) was noted against diphtheria toxoid, and similar high immunogenicity (3.2±2.1IU/mL, 100%) was noted against tetanus toxoid. Immunogenicity against pertussis antigen was significantly greater in the interchangeable vaccinated group compared to the control group, and 57% of the interchangeable vaccinated subjects achieved high levels of protective immunity (45.2±21.5EU/mL). No serious adverse effects were noted, and most adverse effects resolved without treatment. The immunogenicity against each antigen was high in patients who were interchangeably vaccinated for DTaP. Our results provide clinical evidence affirming the non-inferiority of interchangeable vaccination when it cannot be avoided such as in limited vaccine supply situations or different prices.

Immunization with the recombinant antigen Ss-IR induces protective immunity to infection with Strongyloides stercoralis in mice

Human intestinal infections with the nematode Strongyloides stercoralis remain a significant problem worldwide and a vaccine would be a useful addition to the tools available to prevent and control this infection. The goal of this study was to test single antigens for their efficacy in a vaccine against S. stercoralis larvae in mice. Alum was used as the adjuvant in these studies and antigens selected for analysis were either recognized by protective human IgG (Ss-TMY-1, Ss-EAT-6, and Ss-LEC-5) or were known to be highly immunogenic in humans (Ss-NIE-1 and Ss-IR). Only mice immunized with the Ss-IR antigen demonstrated a significant decrease of approximately 80% in the survival of larval parasites in the challenge infection. Antibodies, recovered from mice with protective immunity to S. stercoralis after immunization with Ss-IR, were used to locate the antigen in the larvae. Confocal microscopy revealed that IgG from mice immunized with Ss-IR bound to the surface of the parasites and observations by electron microscopy indicated that IgG bound to granules in the glandular esophagus. Serum collected from mice immunized with Ss-IR passively transferred immunity to naïve mice. These studies demonstrate that Ss-IR, in combination with alum, induces high levels of protective immunity through an antibody dependent mechanism and may therefore be suitable for further development as a vaccine against human strongyloidiasis.

Multiple vaccinations with UV- attenuated cercariae in pig enhance protective immunity against Schistosoma japonicum infection as compared to single vaccination

BackgroundSchistosomiasis japonica is a major public health problem in the endemic areas of China, the Philippines, and Indonesia. To date, a vaccine has not been developed against this disease but immunization with UV-attenuated cercariae can induce a high level of protective immunity in Landrace/Yorkshire/Duroc crossbred pigs. To compare the efficacy of a single vaccination and multiple vaccinations with UV-attenuated Schistosoma japonicum cercariae, two groups of pigs received either one or three exposures to 10,000 cercariae attenuated with 400 μw UV.ResultsPigs with a single immunization had a 59.33% reduction in adult worm burden, a 89.87% reduction in hepatic eggs and a 86.27% reduction in fecal eggs at eight weeks post-challenge (P < 0.01). After three immunizations, protection increased to 77.62%, 88.8% and 99.78% reduction in adult worms, hepatic eggs and fecal eggs, respectively (P < 0.01). Humoral and cellular immunological parameters measured indicated that schistosome-specific IgG1 and IgG2 levels in the vaccinated groups were higher than in the infection-control group. Triple vaccinations resulted in higher levels of antibodies, especially IgG2, compared with a single vaccination and IFN-γ levels increased with repeated immunization with UV-irradiated cercariae.ConclusionThe high levels of protection against S. japonicum infection can be achieved with a UV-attenuated vaccine in pigs, and that three vaccinations were possibly more effective than a single vaccination. Moreover, triple vaccinations evoked a more vigorous IFN-γ response and a stronger antibody-mediated response, especially an increase in the levels of IgG2 antibodies.

Searching of optimal vaccination schedules

Genetic algorithms (GAs) are a particular class of evolutionary algorithms that use techniques inspired by evolutionary biology. These are widely used in different areas of bioinformatics. In immunoinformatics, a common optimization problem is the search of optimal vaccination schedules. The problem of defining optimal schedules is particularly acute in cancer immunopreventive approaches, which requires a sequence of vaccine administrations to keep a high level of protective immunity. This paper presents a formalization of the optimization problem and show how a GA search on a model-based approach can be used to deal with the problem.

Withdrawn: Immunization with pseudotype baculovirus expressing envelope protein of Japanese encephalitis virus elicits protective immunity in mice

Japanese encephalitis (JE) is a serious infection disease throughout southern and eastern Asia. The design and development of safer and more efficacious vaccines against Japanese encephalitis virus (JEV) is a matter of high priority. Recently, baculovirus pseudotyped with vesicular stomatitis virus glycoprotein was described as an attractive gene-delivery vehicle in mammalian cells and a potential vector for vaccine development. In the present study, we constructed recombinant pseudotype baculovirus encoding the Japanese encephalitis virus (JEV) envelope (E) protein and demonstrated that it could elicit high protective immunity in mice. Recombinant pseudotype baculovirus (BV-G-E) was generated by inserting JEV E gene fragment into pFastBac-VSV/G vector. BALB/c mice were immunized with BV-G-E and challenged with JEV wild-type strain. The neutralization antibody, interferon (IFN)-gamma expression and release, and survival rate were analysed and compared with the group of immunized with inactivated vaccine and DNA vaccine (pc-E) encoding the same gene of JEV. We demonstrated that intramuscular injections of BV-G-E at various doses into mice produced higher levels of JEV-specific neutralizing antibodies, IFN-gamma and better protective efficacy against a lethal challenge with JEV than that of pc-E. Furthermore, BV-G-E could elicit a higher level cellular immunity response and provide equal protective efficacy against JEV challenge compared to inactivated vaccine. Our data demonstrate that BV-G-E elicited higher levels of protective immunity than DNA vaccine and that pseudotype baculovirus-mediated gene delivery can be utilized as an alternative strategy to develop new generations of vaccines against JEV infection.

Immunization with pseudotype baculovirus expressing envelope protein of Japanese encephalitis virus elicits protective immunity in mice

Japanese encephalitis (JE) is a serious infection and disease in southern and eastern Asia. The design and development of safer and more efficacious vaccines against Japanese encephalitis virus (JEV) is a high-priority target in the world. Recently, baculovirus pseudotyped with vesicular stomatitis virus glycoprotein (VSVG) was described as an attractive gene delivery vehicle in mammalian cells and a potential vector for vaccine development. In the present study, we constructed a recombinant pseudotype baculovirus encoding the JEV envelope (E) protein and demonstrated that it could elicit high protective immunity in mice. Recombinant pseudotype baculovirus (BV-G-E) was generated by inserting JEV E gene fragment into pFastBac-VSV/G vector. BALB/c mice were immunized with BV-G-E and challenged with JEV wild-type strain. The neutralization antibody, interferon (IFN)-gamma expression and release, and survival rate were analysed and compared with the group of immunized with inactivated vaccine and DNA vaccine (pc-E) encoding the same gene of JEV. We demonstrated that intramuscular injections of BV-G-E at various doses into mice produced higher levels of JEV-specific neutralizing antibodies, IFN-gamma and better protective efficacy against a lethal challenge with JEV than that of pc-E. Furthermore, BV-G-E could elicit a higher level of cellular immunity response and provide equal protective efficacy against JEV challenge compared to inactivated vaccine. Our data demonstrate that BV-G-E elicited higher levels of protective immunity compared to DNA vaccine and that pseudotype baculovirus-mediated gene delivery can be utilized as an alternative strategy to develop new generations of vaccines against JEV infection.

Evaluation of recombinant proteins of Neospora caninum as vaccine candidates (in a mouse model)

Abortion, resulting from infections by the parasite Neospora caninum, is a major cause of economic loss to both the dairy and beef industries of cattle-producing countries of the world. Vaccination as a means of preventing abortion and/or infection represents a viable control strategy; indeed a commercial vaccine is available in some countries, albeit of unknown efficacy. The commercial vaccine is based on inactivated tachyzoites of N. caninum but other approaches based on lysates and recombinant antigens of N. caninum may also be feasible. In this study we have used an immunisation/challenge model of transplacental transmission, based on the Qs mouse with an Nc-Liverpool challenge, to investigate the vaccine potential of a number of formulations based on four recombinant proteins of N. caninum (GRA1, GRA2, MIC10, and p24B). All formulations studied were immunogenic in the mouse when assessed by ELISA using sonicated tachyzoite antigen as the target antigen. In one experiment, a mixture of MIC10 and p24B produced partial protection against transplacental transmission of N. caninum in this mouse model; in contrast a live infection of tachyzoites of NC-Nowra given before pregnancy always induces very high levels of protective immunity. The field of vaccines against Neospora-associated abortion in cattle is discussed.