A DNA vaccine co-expressing Trichinella spiralis MIF and MCD-1 with murine ubiquitin induces partial protective immunity in mice

A secreted MIF homologue from Trichinella spiralis binds to and interacts with host monocytes

Trichinella spiralis is a very successful parasite capable of surviving in many mammal hosts and residing in muscle tissues for long periods, indicating that it must have some effective strategies to escape from or guard against the host immune attack. The functions of MIF have been studied in other parasites and demonstrated to function as a virulence factor aiding in their survival by modulating the host immune response. However, the functions of Trichinella spiralis MIF (TsMIF) have not been addressed. Here, we successfully obtained the purified recombinant TsMIF and anti-TsMIF serum. Our results showed that TsMIF was expressed in all the Trichinella spiralis developmental stages, especially highly expressed in the muscle larvae (ML) and mainly located in stichocytes, midgut, cuticle, muscle cells of ML and around intrauterine embryos of female adults. We also observed TsMIF could be secreted from ML and bind to host monocytes. Next, our data demonstrated that TsMIF not only stimulated the phosphorylation of ERK1/2 and cell proliferation by binding to the host cell surface receptor CD74, but also interacted with a host intracellular protein, Jab1, which is a coactivator of AP-1 transcription. We concluded the secreted TsMIF plays an important role in the interaction between Trichinella spiralis and its host and could be a potential drug or vaccine target molecule against Trichinella spiralis infection.

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.

Advances in vaccine development for human trichuriasis

Trichuriasis known as whipworm infection caused by Trichuris trichiura, is a highly prevalent soil-transmitted helminthiasis in low- and middle-income countries located in tropical and subtropical areas and affecting approximately 360 million people. Children typically harbour the largest burden of T. trichiura and they are usually co-infected with other soil-transmitted helminth (STH), including Ascaris lumbricoides and hookworm. The consequences of trichuriasis, such as malnutrition and physical and cognitive growth restriction, lead to a massive health burden in endemic regions. Despite the implementation of mass drug administration of anthelminthic treatment to school-age children, T. trichiura infection remains challenging to control due to the low efficacy of current drugs as well as high rates of post-treatment re-infection. Thus, the development of a vaccine that would induce protective immunity and reduce infection rate or community faecal egg output is essential. Hurdles for human whipworm vaccine development include the lack of suitable vaccine antigen targets and animal models for human T. trichiura infection. Instead, rodent whipworm T. muris infected mouse models serve as a major surrogate for testing immunogenicity and efficacy of vaccine candidates. In this review, we summarize recent advances in animal models for T. trichiura antigen discovery and testing of vaccine candidates, while providing an overall view of the current status of T. trichiura vaccine development.

Vaccination with novel low-molecular weight proteins secreted from Trichinella spiralis inhibits establishment of infection

Trichinella spiralis muscle stage larvae (mL1) produce excretory-secreted products (ESPs), a complex mixture of protein, which are believed to be important for establishing or maintaining an infection niche within skeletal muscle and the intestine. Studies of both whole ESPs and individual cloned proteins have shown that some ESPs are potent immunogens capable of eliciting protective immune responses. Here we describe two novel proteins, Secreted from Muscle stage Larvae SML-4 and SML-5 which are 15 kDa and 12 kDa respectively. The genes encoding these proteins are highly conserved within the Trichinellids, are constituents of mL1 ESP and localized in the parasite stichosome. While SML-5 is only expressed in mL1 and early stages of adult nematode development, SML-4 is a tyvosylated glycoprotein also produced by adult nematodes, indicating it may have a function in the enteral phase of the infection. Vaccination with these proteins resulted in an impaired establishment of adult stages and consequently a reduction in the burden of mL1 in BALB/c mice. This suggests that both proteins may be important for establishment of parasite infection of the intestine and are prophylactic vaccine candidates.

Role of Host and Parasite MIF Cytokines during Leishmania Infection

Macrophage migration inhibitory factor (MIF) is an immunoregulatory cytokine that has been extensively characterized in human disease and in mouse models. Its pro-inflammatory functions in mammals includes the retention of tissue macrophages and a unique ability to counteract the immunosuppressive activity of glucocorticoids. MIF also acts as a survival factor by preventing activation-induced apoptosis and by promoting sustained expression of inflammatory factors such as TNF-α and nitric oxide. The pro-inflammatory activity of MIF has been shown to be protective against Leishmania major infection in mouse models of cutaneous disease, however the precise role of this cytokine in human infections is less clear. Moreover, various species of Leishmania produce their own MIF orthologs, and there is evidence that these may drive an inflammatory environment that is detrimental to the host response. Herein the immune response to Leishmania in mouse models and humans will be reviewed, and the properties and activities of mammalian and Leishmania MIF will be integrated into the current understandings in this field. Furthermore, the prospect of targeting Leishmania MIF for therapeutic purposes will be discussed.

Molecular cloning of enolase from Trichinella spiralis and the protective immunity in mice

Trichinella spiralis, the main pathogen of trichinosis, infects a wide range of mammalian hosts and is one of the most widespread parasites worldwide. For parasites, glycolysis is the most important way to generate energy. Previous studies showed that some enzymes involved in the glycolytic pathway play roles in regulation the host immunity. In this paper, enolase from T. spiralis was cloned and the protective potentials were studied. One hundred and sixty ICR mice were divided into four groups and vaccinated with recombinant enolase (pET-ENO), eukaryotic recombinant plasmid encoding enolase (pVAX1-ENO) and negative controls (pVAXl and PBS), respectively. Two weeks after the second immunization, each mouse was challenged orally with 200 muscle larvae (MLs) of T. spiralis. Results showed that mice vaccinated with pET-ENO and pVAX1-ENO induced specific antibodies of IgG, IgA, IgM, but no IgE. Subclasses of IgG antibodies showed that mice immunized with recombinant protein and recombinant plasmids induced a Th1/Th2 immune response. Concentrations of serum cytokines were detected and showed significant increase of IFN-γ, IL-4 and TGFβ1, while IL-17 in each group was not significantly different. Flow cytometric analysis showed significant increase of CD4+ and CD8+ T lymphocytes in the groups immunized with recombinant protein and recombinant plasmids. Challenge infection demonstrated that immunized groups had a reduced number of worm burdens. The reductions of larvae per gram muscle (LPG) in pET-ENO and pVAX1-ENO group were 17.7% and 15.8% when compared with PBS control.

Reducing zoonotic and internal parasite burdens in pigs using a pig confinement system

Aim

This study was designed to validate the effectiveness of the pig confinement system (PCS) in reducing the prevalence of zoonotic and internal parasite burdens in pigs.

Materials and Methods

Ten PCS households were selected together with 10 households practising traditional scavenging systems. Five pigs were monitored per household every 3 months for 15 months and blood and feces collected. Pigs received a single dose of oxfendazole at 30 mg/kg at baseline. Qualitative fecal examinations for intestinal parasite stages were performed, and serum was tested for antibodies to cysticercus of Taenia solium, Trichinella spp., and Toxoplasma gondii.

Results

Based on fecal examination, the prevalence of pigs positive for parasite eggs was reduced in PCS pigs over consecutive samplings (Ascaris suum [14.3% to 0%], Trichuris suis [46.9% to 8.3%], Strongyle-type eggs [81.6% to 8.3%], Physocephalus spp. [6.1% to 0%], and Metastrongylus apri [20.8% to 0%]) compared with increases in the number of pigs positive for parasite eggs in non-PCS pigs (T. suis [20-61.5%], Strongyle-type [60.4-80.8%], Physocephalus spp. [8.3-15.4%], and M. apri [20.8-34.6%]) and little change in pigs positive for A. suum (18.8-19.2%). While the prevalence of pigs with antibodies against to cysticerci of T. solium reduced in PCS pigs from 18% to 14%, the prevalence in non-PCS pigs increased from 42% to 52%. Antibodies to Trichinella were not detected, but the prevalence of T. gondii antibodies increased from 6% to 10% in PCS pigs and from 7% to 24% in non-PCS pigs.

Conclusion

These data demonstrate the potential of a PCS to reduce the prevalence of pigs infected with zoonotic and internal parasites and thus the risk to human and pig health.

Leishmania-encoded orthologs of macrophage migration inhibitory factor regulate host immunity to promote parasite persistence

Leishmania major encodes 2 orthologs of the cytokine macrophage migration inhibitory factor (MIF), whose functions in parasite growth or in the host-parasite interaction are unknown. To determine the importance of Leishmania-encoded MIF, both LmMIF genes were removed to produce an mif(-/-) strain of L. major This mutant strain replicated normally in vitro but had a 2-fold increased susceptibility to clearance by macrophages. Mice infected with mif(-/-) L. major, when compared to the wild-type strain, also showed a 3-fold reduction in parasite burden. Microarray and functional analyses revealed a reduced ability of mif(-/-) L. major to activate antigen-presenting cells, resulting in a 2-fold reduction in T-cell priming. In addition, there was a reduction in inflammation and effector CD4 T-cell formation in mif(-/-) L. major-infected mice when compared to mice infected with wild-type L. major Notably, effector CD4 T cells that developed during infection with mif(-/-) L. major demonstrated statistically significant differences in markers of functional exhaustion, including increased expression of IFN-γ and IL-7R, reduced expression of programmed death-1, and decreased apoptosis. These data support a role for LmMIF in promoting parasite persistence by manipulating the host response to increase the exhaustion and depletion of protective CD4 T cells.-Holowka, T., Castilho, T. M., Baeza Garcia, A., Sun, T., McMahon-Pratt, D., Bucala, R. Leishmania-encoded orthologs of macrophage migration inhibitory factor regulate host immunity to promote parasite persistence.

Induction of protection in murine experimental models againstTrichinella spiralis: an up-to-date review

The parasitic nematodeTrichinella spiralis, an aetiological agent of the disease known as trichinellosis, infects wild and domestic animals through contaminated pig meat, which is the major source forTrichinellatransmission. Prevention of this disease by interrupting parasite transmission includes vaccine development for livestock; however, major challenges to this strategy are the complexity of theT. spiralislife cycle, diversity of stage-specific antigens, immune-evasion strategies and the modulatory effect of host responses. Different approaches have been taken to induce protective immune responses byT. spiralisimmunogens. These include the use of whole extracts or excretory–secretory antigens, as well as recombinant proteins or synthesized epitopes, using murine experimental models for trichinellosis. Here these schemes are reviewed and discussed, and new proposals envisioned to block the zoonotic transmission of this parasite.

Intranasal immunization with DNA vaccine coexpressing Der p 1 and ubiquitin in an allergic rhinitis mouse model

BACKGROUND

The worldwide prevalence of allergic rhinitis (AR) is increasing, whereas treatments for AR remain limited in effect. Therefore, a new type of effective drug is eagerly in demand.

OBJECTIVE

To create a hypoallergenic vaccine by forced ubiquitination.

METHODS

In the present study, we constructed a DNA vaccine coexpressing Der p 1 allergen and murine ubiquitin, which used chitosan as a carrier. Through the vitro and vivo experiments, we evaluated its protective efficacy against AR.

RESULTS

The results indicated that the DNA vaccine pVAX1-Ub-Derp1/CS had been successfully constructed. This nanoparticle could not only transfect 293T cells in vitro but also transform cells in vivo. The inflammation of nasal mucosa in an AR murine model via immunization with pVAX1-Ub-Derp1/CS was less severe than those without treatments. Furthermore, it found that mice immunized with pVAX1-Ub-Derp1/CS generated a high level of specific IgG but a low level of specific IgE (P < .01). The significantly increased levels of interferon-γ and the significantly decreased levels of interleukins 4, 10, and 17 indicated that a TH1-type response was elicited by immunization with pVAX1-Ub-Derp1/CS (P < .01). This effect was especially stronger through intranasal immunization.

CONCLUSION

Nasal mucosal immunization and ubiquitination are efficacious strategies to enhance the efficiency and safety of DNA vaccine. The nanoparticle pVAX1-Ub-Derp1/CS is expected to be a new kind of effective vaccine for AR.

Advancing a multivalent 'Pan-anthelmintic' vaccine against soil-transmitted nematode infections

Ascaris lumbricoides

The Sabin Vaccine Institute Product Development Partnership is developing a Pan-anthelmintic vaccine that simultaneously targets the major soil-transmitted nematode infections, in other words, ascariasis, trichuriasis and hookworm infection. The approach builds off the current bivalent Human Hookworm Vaccine now in clinical development and would ultimately add both a larval Ascaris lumbricoides antigen and an adult-stage Trichuris trichiura antigen from the parasite stichosome. Each selected antigen would partially reproduce the protective immunity afforded by UV-attenuated Ascaris eggs and Trichuris stichosome extracts, respectively. Final antigen selection will apply a ranking system that includes the evaluation of expression yields and solubility, feasibility of process development and the absence of circulating antigen-specific IgE among populations living in helminth-endemic regions. Here we describe a five year roadmap for the antigen discovery, feasibility and antigen selection, which will ultimately lead to the scale-up expression, process development, manufacture, good laboratory practices toxicology and preclinical evaluation, ultimately leading to Phase 1 clinical testing.