Development and immunogenicity of a recombinant pseudorabies virus expressing Sj26GST and SjFABP from Schistosoma japonicum

Immunization with the glutathione S-transferase Sj26GST with Chi-CpG NP against Schistosoma japonicum in mice

Schistosomiasis caused by Schistosoma japonicum (S. japonicum) is a major public health problem in the Philippines, China and Indonesia. In this study, the immunopotentiator CpG-ODN was encapsulated within chitosan nanoparticles (Chi NPs) to create a combination adjuvant (Chi-CpG NP). This approach was employed to enhance the immunogenicity of 26 kDa glutathione S-transferase (Sj26GST) from S. japonicum through intranasal immunization. The results demonstrated higher levels of specific anti-Sj26GST antibodies and Sj26GST-specific splenocyte proliferation compared to mice that were immunized with Sj26GST + Chi-CpG NP. Cytokine analysis of splenocytes revealed that the Sj26GST + Chi-CpG NP induced a slight Th1-biased immune response, with increased production of IFN-γ by CD4+ T-cells in the spleen. Subsequently, mice were intradermally inoculated with 1 × 107 organisms in the Coeliac cavity. The bacterial organ burden detected in the liver of immunized mice suggested that Sj26GST + Chi-CpG NP enhances protective immunity to inhibit S. japonicum colonization. Therefore, Sj26GST + Chi-CpG NP vaccination enhances Sj26GST-specific immunogenicity and provides protection against S. japonicum.

Functional characterization of differentially expressed proteins coming from unisexual and bisexual infected Schistosoma japonicum female worms

Schistosomiasis is an important zoonotic disease affecting up to 40 kinds of animals and is responsible for ∼250 million human cases per year. Due to the extensive use of praziquantel for the treatment of parasitic diseases, drug resistance has been reported. Consequently, novel drugs and effective vaccines are urgently needed for sustained control of schistosomiasis. Targeting reproductive development of Schistosoma japonicum could contribute to the control of schistosomiasis. In this study, five highly expressed proteins (S. japonicum large subunit ribosomal protein L7e, S. japonicum glutathione S-transferase class-mu 26 kDa isozyme, S. japonicum UDP-galactose-4-epimerase and two hypothetical proteins SjCAX70849 and SjCAX72486) in 18, 21, 23, and 25-day mature female worms compared to single-sex infected female worms were selected based on our previous proteomic analysis. Quantitative real-time polymerase chain reaction analysis and long-term interference with small interfering RNA were performed to identify the biological functions of these five proteins. The transcriptional profiles suggested that all five proteins participated in the maturation of S. japonicum. RNA interference against these proteins resulted in morphological changes to S. japonicum. The results of an immunoprotection assay revealed that immunization of mice with recombinant SjUL-30 and SjCAX72486 upregulated production of immunoglobulin G-specific antibodies. Collectively, the results demonstrated that these five differentially expressed proteins were vital to reproduction of S. japonicum and, thus, are potential candidate antigens for immune protection against schistosomiasis.

Comparative proteomic profiles of Schistosoma japonicum male worms derived from single-sex and bisexual infections

Schistosomiasis, which is caused by parasitic schistosomes, remains the second most prevalent parasitic disease of mammals worldwide. To successfully maintain fecundity, schistosomes have evolved a lifecycle that involves the cooperation of morphologically distinct male and female forms. Eggs produced by worm pairs are vital to the lifecycle of the parasite and are responsible for pathogenesis. Understanding the reproductive mechanism of schistosomes will help to control infection. In this study, the proteomic profiles of single-sex infected male (SM) worms and bisexual infected mated male (MM) worms of Schistosoma japonicum at 18, 21, 23, and 25 days p.i. were identified through data-independent acquisition. In total, 674 differentially expressed proteins (DEPs) were identified for the SM and MM worms at all four timepoints. Bioinformatic analysis demonstrated that most of the DEPs were involved in biosynthetic processes including locomotion, cell growth and death, cell motility, and metabolic processes such as protein metabolism and glucose metabolism. Schistosoma japonicum glycosyltransferase (SjGT) and S. japonicum nicastrin protein (SjNCSTN) were selected for quantitative real‑time PCR analysis and long-term interference with small interfering RNA (siRNA) to further explore the functions of the DEPs. Sjgt mRNA expression was mainly enriched in male worms, while Sjncstn was enriched in both sexes. siRNA against SjGT and SjNCSTN resulted in minor morphological changes in the testes of male worms and significant decreased vitality and fertility. The present study provides comprehensive proteomic profiles of S. japonicum SM and MM worms at 18, 21, 23, and 25 days p.i. and offers insights into the mechanisms underlying the growth and maturation of schistosomes.

Design of live-attenuated animal vaccines based on pseudorabies virus platform

Pseudorabies virus (PRV) is a double-stranded DNA virus with a genome approximating 150 kb in size. PRV contains many non-essential genes that can be replaced with genes encoding heterogenous antigens without affecting viral propagation. With the ability to induce cellular, humoral and mucosal immune responses in the host, PRV is considered to be an ideal and potential live vector for generation of animal vaccines. In this review, we summarize the advances in attenuated recombinant PRVs and design of PRV-based live vaccines as well as the challenge of vaccine application.

Promising Technologies in the Field of Helminth Vaccines

Helminths contribute a larger global burden of disease than both malaria and tuberculosis. These eukaryotes have caused human infections since before our earliest recorded history (i.e.: earlier than 1200 B.C. for Schistosoma spp.). Despite the prevalence and importance of these infections, helminths are considered a neglected tropical disease for which there are no vaccines approved for human use. Similar to other parasites, helminths are complex organisms which employ a plethora of features such as: complex life cycles, chronic infections, and antigenic mimicry to name a few, making them difficult to target by conventional vaccine strategies. With novel vaccine strategies such as viral vectors and genetic elements, numerous constructs are being defined for a wide range of helminth parasites; however, it has yet to be discussed which of these approaches may be the most effective. With human trials being conducted, and a pipeline of potential anti-helminthic antigens, greater understanding of helminth vaccine-induced immunity is necessary for the development of potent vaccine platforms and their optimal design. This review outlines the conventional and the most promising approaches in clinical and preclinical helminth vaccinology.

Process Development of Sj-p80: A Low-Cost Transmission-Blocking Veterinary Vaccine for Asiatic Schistosomiasis

Asiatic schistosomiasis caused by Schistosoma japonicum is a neglected tropical disease resulting in significant morbidity to both humans and animals - particularly bovines - in endemic areas. Infection with this parasite leads to less healthy herds, causing problems in communities which rely on bovines for farming, milk and meat production. Additionally, excretion of parasite eggs in feces perpetuates the life cycle and can lead to human infection. We endeavored to develop a minimally purified, inexpensive, and effective vaccine based on the 80 kDa large subunit of the calcium activated neutral protease (calpain) from S. japonicum (Sj-p80). Here we describe the production of veterinary vaccine-grade Sj-p80 at four levels of purity and demonstrate in a pilot study that minimally purified antigen provides protection against infection in mice when paired with a low-cost veterinary adjuvant, Montanide™ ISA61 VG. Preliminary data demonstrate that the vaccine is immunogenic with robust antibody titers following immunization, and vaccination resulted in a reduction of parasite eggs being deposited in the liver (23.4-51.4%) and intestines (1.9-55.1%) depending on antigen purity as well as reducing the ability of these eggs to hatch into miracidia by up to 31.6%. We therefore present Sj-p80 as a candidate vaccine antigen for Asiatic schistosomiasis which is now primed for continued development and testing in bovines in endemic areas. A successful bovine vaccine could play a major role in reducing pathogen transmission to humans by interrupting the parasitic life cycle and improving quality of life for people living in endemic countries.

Characterization of a recombinant pseudorabies virus expressing porcine parvovirus VP2 protein and porcine IL-6

Background

Porcine parvovirus (PPV) and pseudorabies virus (PRV) are the important etiological agents of swine infectious diseases, resulting in huge economic losses to the Chinese swine industry. Interleukin-6 (IL-6) has the roles to support host immune response to infections as a pleiotropic cytokine. It is essential to construct a live attenuated vaccine-based recombinant PRV that expresses PPV VP2 protein and porcine IL-6 for prevention and control of PRV and PPV.

Methods

The recombinant plasmid, pGVP2-IL6, was constructed by porcine IL-6 gene substituting for EGFP gene of the PRV transfer plasmid pGVP2-EGFP containing VP2 gene of PPV. Plasmid pGVP2-IL6 was transfected into swine testicle cells pre-infected with the virus rPRV-VP2-EGFP strain through homologous recombination and plaque purification to generate a recombinant virus rPRV-VP2-IL6. The recombinant PRV was further identified by PCR and DNA sequencing, and the expression of the VP2 protein and porcine IL-6 was analyzed by reverse transcription-PCR (RT-PCR) and Western blot. The virus titer was calculated according to Reed and Muench method. The immunogenicity of the recombinant virus was preliminarily evaluated in mice by intramuscular administration twice with the rPRV-VP2-IL6 at 4-week intervals.

Results

A recombinant virus rPRV-VP2-IL6 was successfully constructed and confirmed in this study. The properties of rPRV-VP2-IL6 were similar to the parental virus HB98 in terms of growth curve, morphogenesis and virus plaque sizes, and rPRV-VP2-IL6 was proliferated in different cell types. It induced specific antibodies against PPV as well as a strong increase of PPV-specific lymphocyte proliferation responses in mice immunized with rPRV-VP2-IL6, and provided partial protection against the virulent PPV challenge. rPRV-VP2-IL6 also induced a high level of neutralizing antibodies against PRV, and significantly reduced the mortality rate of (1 of 10) following virulent PRV challenge compared with the control (10 of 10).

Conclusions

The recombinant rPRV-VP2-IL6 might be a potential candidate vaccine against PRV and PPV infections in pigs.

Utilization of herpesviridae as recombinant viral vectors in vaccine development against animal pathogens

Throughout the past few decades, numerous viral species have been generated as vaccine vectors. Every viral vector has its own distinct characteristics. For example, the family herpesviridae encompasses several viruses that have medical and veterinary importance. Attenuated herpesviruses are developed as vectors to convey heterologous immunogens targeting several serious and crucial pathogens. Some of these vectors have already been licensed for use in the veterinary field. One of their prominent features is their capability to accommodate large amount of foreign DNA, and to stimulate both cell-mediated and humoral immune responses. A better understanding of vector-host interaction builds up a robust foundation for the future development of herpesviruses-based vectors. At the time, many molecular tools are applied to enable the generation of herpesvirus-based recombinant vaccine vectors such as BAC technology, homologous and two-step en passant mutagenesis, codon optimization, and the CRISPR/Cas9 system. This review article highlights the most important techniques applied in constructing recombinant herpesviruses vectors, advantages and disadvantages of each recombinant herpesvirus vector, and the most recent research regarding their use to control major animal diseases.

Schistosomiasis vaccines: where do we stand?

Schistosomiasis, caused mainly by S. mansoni, S. haematobium and S. japonicum, continues to be a serious tropical disease and public health problem resulting in an unacceptably high level of morbidity in countries where it is endemic. Praziquantel, the only drug currently available for treatment, is unable to kill developing schistosomes, it does not prevent re-infection and its continued extensive use may result in the future emergence of drug-resistant parasites. This scenario provides impetus for the development and deployment of anti-schistosome vaccines to be used as part of an integrated approach for the prevention, control and eventual elimination of schistosomiasis. This review considers the present status of candidate vaccines for schistosomiasis, and provides some insight on future vaccine discovery and design.

Evaluation of protective immune response in mice by vaccination the recombinant adenovirus for expressing Schistosoma japonicum inhibitor apoptosis protein

Schistosomiasis is a worldwide parasitic disease, and while it can be successfully treated with chemotherapy, this does not prevent reinfection with the parasite. Adenovirus vectors have been widely used for vaccine delivery, and a vaccination approach has the potential to prevent infection with Schistosoma. Here, we developed a recombinant adenoviral vector that expresses Schistosoma japonicum inhibitor apoptosis protein (Ad-SjIAP) and assessed its immunoprotective functions against schistosomiasis in mice. Murine immune responses following vaccination were investigated using enzyme-linked immunosorbent assays (ELISA), lymphocyte proliferation, and cytokine assays. The protective immunity in mice was evaluated by challenging with S. japonicum cercariae. Our results indicated that immunization with the Ad-SjIAP in mice induced a strong serum IgG response against IAP including IgG1, IgG2a, and IgG2b. In addition, lymphocyte proliferation experiments showed that mice treated with Ad-SjIAP significantly increased the lymphocyte response upon stimulation with recombinant Schistosoma japonicum inhibitor apoptosis protein (rSjIAP). Moreover, cytokine assays indicated that vaccination of Ad-SjIAP significantly increased the production of interferon (IFN)-γ and IL-2 as compared to the corresponding control group. Furthermore, following the challenge with S. japonicum cercariae, the vaccine conferred moderate protection, with an average rate of 37.95% for worm reduction and 31.7% for egg reduction. Taken together, our preliminarily results suggested that schistosoma IAP may be a potential vaccine against S. japonicum and that adenoviral vectors may serve as an alternative delivery vehicle for schistosome vaccine development.

An overview of live attenuated recombinant pseudorabies viruses for use as novel vaccines

Pseudorabies virus (PRV) is a double-stranded, DNA-based swine virus with a genome approximating 150 kb in size. PRV has many nonessential genes which can be replaced with genes encoding heterologous antigens but without deleterious effects on virus propagation. Recombinant PRVs expressing both native and foreign antigens are able to stimulate immune responses. In this paper, we review the current status of live attenuated recombinant PRVs and live PRV-based vector vaccines with potential for controlling viral infections in animals.

Protective effects of membrane-anchored and secreted DNA vaccines encoding fatty acid-binding protein and glutathione S-transferase against Schistosoma japonicum

In order to explore the high performance bivalent DNA-based vaccine against schistosomes, SjFABP and Sj26GST were selected and used to construct a vaccine. Two strategies were used to construct the bivalent DNA vaccine. In the first strategy, a plasmid encoding antigen in the secreted form was used, while in the other, a plasmid encoding a truncated form of SjFABP and Sj26GST targeted to the cell surface was used. Various parameters, including antibody and cytokine response, proliferation, histopathological examination, and characterization of T cell subsets were used to evaluate the type of immune response and the level of protection against challenge infection. Injection with secreted pIRES-sjFABP-sj26GST significantly increased the levels of antibody, splenocyte proliferation, and production of IFN-γ, compared with membrane-anchored groups. Analysis of splenic T cell subsets showed that the secreted vaccine significantly increased the percentage of CD3⁺CD4⁺ and CD3⁺CD8⁺ T cells. Liver immunopathology (size of liver granulomas) was significantly reduced in the secreted group compared with the membrane-anchored groups. Moreover, challenge experiments showed that the worm and egg burdens were significantly reduced in animals immunized with recombinant vaccines. Most importantly, secreted Sj26GST-SjFABP markedly enhanced protection, by reducing worm and egg burdens by 31.8% and 24.78%, respectively, while the membrane-anchored group decreased worm and egg burdens by 24.80% and 18.80%, respectively. Taken together, these findings suggest that the secretory vaccine is more promising than the membrane-anchored vaccine, and provides support for the development and application of this vaccine.

Immunization of pigs with an attenuated pseudorabies virus recombinant expressing the haemagglutinin of pandemic swine origin H1N1 influenza A virus

Pigs can be severely harmed by influenza, and represent important reservoir hosts, in which new human pathogens such as the recent pandemic swine-origin H1N1 influenza A virus can arise by mutation and reassortment of genome segments. To obtain novel, safe influenza vaccines for pigs, and to investigate the antigen-specific immune response, we modified an established live-virus vaccine against Aujeszky's disease of swine, pseudorabies virus (PrV) strain Bartha (PrV-Ba), to serve as vector for the expression of haemagglutinin (HA) of swine-origin H1N1 virus. To facilitate transgene insertion, the genome of PrV-Ba was cloned as a bacterial artificial chromosome. HA expression occurred under control of the human or murine cytomegalovirus immediate early promoters (P-HCMV, P-MCMV), but could be substantially enhanced by synthetic introns and adaptation of the codon usage to that of PrV. However, despite abundant expression, the heterologous glycoprotein was not detectably incorporated into mature PrV particles. Replication of HA-expressing PrV in cell culture was only slightly affected compared to that of the parental virus strain. A single immunization of pigs with the PrV vector expressing the codon-optimized HA gene under control of P-MCMV induced high levels of HA-specific antibodies. The vaccinated animals were protected from clinical signs after challenge with a related swine-origin H1N1 influenza A virus, and challenge virus shedding was significantly reduced.

Magnetic affinity enzyme-linked immunoassay based on recombinant 26 kDa glutathione-S-transferase for serological diagnosis of schistosomiasis japonica

Schistosomiasis remains a serious worldwide public health problem. Improving the diagnostic assay for surveillance and monitoring will contribute to hastening the possible elimination of the disease in endemic regions. Therefore, this study aims to develop magnetic affinity enzyme-linked immunoassay (MEIA) for serological diagnosis of schistosomiasis based on recombinant 26kDa glutathione-S-transferase of Schistosoma japonicum (rSj26GST). BALB/c mice infected with S. japonicum cercariae (40 per mouse) were used. After infecting for 6 weeks, the antibody was detected by MEIA. All of the infected mouse sera were effectively determined by MEIA. Compared with the enzyme-linked immunosorbent assay (ELISA), MEIA has a higher ratio of the mean positive value to the mean negative value (P/N) at the same dilution ratio (3.92 versus 2.66). MEIA was further applied for diagnosis of human schistosomiasis. Sera from 28 schistosomiasis-confirmed patients with low-intensity infection, 15 treated patients, and 20 non-endemic negative controls, were used to assess the assay. The results showed that MEIA and ELISA had similarity in positive detection rates. However, the higher P/N of MEIA was observed at the same dilution ratio. MEIA had high negative rate in detection of specific IgG in the treated patients. Moreover, there was no cross reaction with the sera of paragonimiasis patients. These results suggested that MEIA based on rSj26GST is a simple, rapid, convenient assay for the diagnosis of schistosomiasis.

Molecular characterization, functional expression, tissue localization and protective potential of a Taenia solium fatty acid-binding protein

The fatty acid-binding proteins (FABPs) comprise a family of proteins that are widely expressed in animal cells and perform a variety of vital functions. Here, we report the identification, characterization, recombinant expression, tissue localization and protective potential of a Taenia solium FABP (TsFABP1). The TsFABP1 primary structure showed all the conserved residues characteristic of the subfamily iv of the intracellular Lipid-Binding Proteins (iLBPs), including those involved in the binding stabilization of the fatty acid molecule. Through a competitive binding assay we found that TsFABP1 is able to bind at least six different fatty acids with preference toward palmitic and stearic acid, suggesting that TsFABP1 is a member of the iLBP subfamily iv. Immunolocalization assays carried out on larval and adult tissues of four species of taeniids using anti-TsFABP1 hyperimmune sera produced in mice and rabbit, showed intense labeling in the tegument of the spiral canal and in subtegumental cytons of the larvae. These findings suggest that the spiral canal might be a major place for FA uptake in the developing scolex. In contrast, only subtegumental cytons in the adult worms stained positive. We propose that TsFABP1 is involved in the mechanism to mobilize fatty acids between compartments in the extensive syncytial tissue of taeniids. Protection assays carried out in a murine model of cysticercosis showed that subcutaneous immunization with TsFABP1 resulted in about 45% reduction of parasite load against an intraperitoneal challenge with Taenia crassiceps cysts. This reduction in parasite load correlated with the level of cellular and humoral immune responses against TsFABP1, as determined in spleen lymphocyte proliferation and ELISA testing.