Gene-deleted live-attenuated Trypanosoma cruzi parasites as vaccines to protect against Chagas disease

Exploring the performance of Escherichia coli outer membrane vesicles as a tool for vaccine development against Chagas disease

BACKGROUND

Vaccine development is a laborious craftwork in which at least two main components must be defined: a highly immunogenic antigen and a suitable delivery method. Hence, the interplay of these elements could elicit the required immune response to cope with the targeted pathogen with a long-lasting protective capacity.

OBJECTIVES

Here we evaluate the properties of Escherichia coli spherical proteoliposomes - known as outer membrane vesicles (OMVs) - as particles with natural adjuvant capacities and as antigen-carrier structures to assemble an innovative prophylactic vaccine for Chagas disease.

METHODS

To achieve this, genetic manipulation was carried out on E. coli using an engineered plasmid containing the Tc24 Trypanosoma cruzi antigen. The goal was to induce the release of OMVs displaying the parasite protein on their surface.

FINDINGS

As a proof of principle, we observed that native OMVs - as well as those carrying the T. cruzi antigen - were able to trigger a slight, but functional humoral response at low immunization doses. Of note, compared to the non-immunized group, native OMVs-vaccinated animals survived the lethal challenge and showed minor parasitemia values, suggesting a possible involvement of innate trained immunity mechanism.

MAIN CONCLUSION

These results open the range for further research on the design of new carrier strategies focused on innate immunity activation as an additional immunization target and venture to seek for alternative forms in which OMVs could be used for optimizing vaccine development.

Immunization with a Trypanosoma cruzi cyclophilin-19 deletion mutant protects against acute Chagas disease in mice

Human infection with the protozoan parasite Trypanosoma cruzi causes Chagas disease for which there are no prophylactic vaccines. Cyclophilin 19 is a secreted cis-trans peptidyl isomerase expressed in all life stages of Trypanosoma cruzi. This protein in the insect stage leads to the inactivation of insect anti-parasitic peptides and parasite transformation whereas in the intracellular amastigotes it participates in generating ROS promoting the growth of parasites. We have generated a parasite mutant with depleted expression of Cyp19 by removal of 2 of 3 genes encoding this protein using double allelic homologous recombination. The mutant parasite line failed to replicate when inoculated into host cells in vitro or in mice indicating that Cyp19 is critical for infectivity. The mutant parasite line also fails to replicate in or cause clinical disease in immuno-deficient mice further validating their lack of virulence. Repeated inoculation of mutant parasites into immuno-competent mice elicits parasite-specific trypanolytic antibodies and a Th-1 biased immune response and challenge of mutant immunized mice with virulent wild-type parasites is 100% effective at preventing death from acute disease. These results suggest that parasite Cyp19 may be candidate for small molecule drug targeting and that the mutant parasite line may warrant further immunization studies for prevention of Chagas disease.

Leishmaniasis and Chagas disease: Is there hope in nanotechnology to fight neglected tropical diseases?

Nanotechnology is revolutionizing many sectors of science, from food preservation to healthcare to energy applications. Since 1995, when the first nanomedicines started being commercialized, drug developers have relied on nanotechnology to improve the pharmacokinetic properties of bioactive molecules. The development of advanced nanomaterials has greatly enhanced drug discovery through improved pharmacotherapeutic effects and reduction of toxicity and side effects. Therefore, highly toxic treatments such as cancer chemotherapy, have benefited from nanotechnology. Considering the toxicity of the few therapeutic options to treat neglected tropical diseases, such as leishmaniasis and Chagas disease, nanotechnology has also been explored as a potential innovation to treat these diseases. However, despite the significant research progress over the years, the benefits of nanotechnology for both diseases are still limited to preliminary animal studies, raising the question about the clinical utility of nanomedicines in this field. From this perspective, this review aims to discuss recent nanotechnological developments, the advantages of nanoformulations over current leishmanicidal and trypanocidal drugs, limitations of nano-based drugs, and research gaps that still must be filled to make these novel drug delivery systems a reality for leishmaniasis and Chagas disease treatment.

Vaccine Design against Chagas Disease Focused on the Use of Nucleic Acids

Chagas disease is caused by the protozoan Trypanosoma cruzi and is endemic to Central and South America. However, it has spread around the world and affects several million people. Treatment with currently available drugs cause several side effects and require long treatment times to eliminate the parasite, however, this does not improve the chronic effects of the disease such as cardiomyopathy. A therapeutic vaccine for Chagas disease may be able to prevent the disease and improve the chronic effects such as cardiomyopathy. This vaccine would be beneficial for both infected people and those which are at risk in endemic and non-endemic areas. In this article, we will review the surface antigens of T. cruzi, in order to choose those that are most antigenic and least variable, to design effective vaccines against the etiological agent of Chagas disease. Also, we discuss aspects of the design of nucleic acid-based vaccines, which have been developed and proven to be effective against the SARS-CoV-2 virus. The role of co-adjuvants and delivery carriers is also discussed. We present an example of a chimeric trivalent vaccine, based on experimental work, which can be used to design a vaccine against Chagas disease.

Nano-Medicines a Hope for Chagas Disease!

Chagas disease, is a vector-mediated tropical disease whose causative agent is a parasitic protozoan named Trypanosoma cruzi. It is a very severe health issue in South America and Mexico infecting millions of people every year. Protozoan T. cruzi gets transmitted to human through Triatominae, a subfamily of the Reduviidae, and do not have any effective treatment or preventative available. The lack of economic gains from this tropical parasitic infection, has always been the reason behind its negligence by researchers and drug manufacturers for many decades. Hence there is an enormous requirement for more efficient and novel strategies to reduce the fatality associated with these diseases. Even, available diagnosis protocols are outdated and inefficient and there is an urgent need for rapid high throughput diagnostics as well as management protocol. The current advancement of nanotechnology in the field of healthcare has generated hope for better management of many tropical diseases including Chagas disease. Nanoparticulate systems for drug delivery like poloxamer coated nanosuspension of benzimidazole have shown promising results in reducing toxicity, elevating efficacy and bioavailability of the active compound against the pathogen, by prolonging release, thereby increasing the therapeutic index. Moreover, nanoparticle-based drug delivery has shown promising results in inducing the host’s immune response against the pathogen with very few side effects. Besides, advances in diagnostic assays, such as nanosensors, aided in the accurate detection of the parasite. In this review, we provide an insight into the life cycle stages of the pathogen in both vertebrate host and the insect vector, along with an overview of the current therapy for Chagas disease and its limitations; nano carrier-based delivery systems for antichagasic agents, we also address the advancement of nano vaccines and nano-diagnostic techniques, for treatment of Chagas disease, majorly focusing on the novel perspectives in combating the disease.

Plant-made vaccines against parasites: bioinspired perspectives to fight against Chagas disease

Introduction: Three decades of evidence have demonstrated that plants are an affordable platform for biopharmaceutical production and delivery. For instance, several plant-made recombinant proteins have been approved for commercialization under good manufacturing practice (GMP). Thus far, plant-based vaccine prototypes have been evaluated at pre- and clinical levels. Particularly, plant-made vaccines against parasitic diseases, such as malaria, cysticercosis, and toxoplasmosis have been successfully produced and orally delivered with promising outcomes in terms of immunogenicity and protection. The experience on several approaches and technical strategies over 30 years accounts for their potential low-cost, high scalability, and easy administration.Areas covered: This platform is an open technology to fight against Chagas disease, one of the most important neglected tropical diseases worldwide.Expert opinion: This review provides a perspective for the potential use of plants as a production platform and delivery system of Trypanosoma cruzi recombinant antigens, analyzing the advantages and limitations with respect to plant-made vaccines produced for other parasitic diseases. Plant-made vaccines are envisioned to fight against Chagas disease and other neglected tropical diseases in those countries suffering endemic prevalence.

Mucosal Heterologous Prime/Boost Vaccination Induces Polyfunctional Systemic Immunity, Improving Protection Against Trypanosoma cruzi

There are several unmet needs in modern immunology. Among them, vaccines against parasitic diseases and chronic infections lead. Trypanosoma cruzi, the causative agent of Chagas disease, is an excellent example of a silent parasitic invasion that affects millions of people worldwide due to its progression into the symptomatic chronic phase of infection. In search for novel vaccine candidates, we have previously introduced Traspain, an engineered trivalent immunogen that was designed to address some of the known mechanisms of T. cruzi immune evasion. Here, we analyzed its performance in different DNA prime/protein boost protocols and characterized the systemic immune response associated with diverse levels of protection. Formulations that include a STING agonist, like c-di-AMP in the boost doses, were able to prime a Th1/Th17 immune response. Moreover, comparison between them showed that vaccines that were able to prime polyfunctional cell-mediated immunity at the CD4 and CD8 compartment enhanced protection levels in the murine model. These findings contribute to a better knowledge of the desired vaccine-elicited immunity against T. cruzi and promote the definition of a vaccine correlate of protection against the infection.

Chagas disease vaccine design: the search for an efficient Trypanosoma cruzi immune-mediated control

Chagas disease is currently endemic to 21 Latin-American countries and has also become a global concern because of globalization and mass migration of chronically infected individuals. Prophylactic and therapeutic vaccination might contribute to control the infection and the pathology, as complement of other strategies such as vector control and chemotherapy. Ideal prophylactic vaccine would produce sterilizing immunity; however, a reduction of the parasite burden would prevent progression from Trypanosoma cruzi infection to Chagas disease. A therapeutic vaccine for Chagas disease may improve or even replace the treatment with current drugs which have several side effects and require long term treatment that frequently leads to therapeutic withdrawal. Here, we will review some aspects about sub-unit vaccines, the rationale behind the selection of the immunogen, the role of adjuvants, the advantages and limitations of DNA-based vaccines and the idea of therapeutic vaccines. One of the main limitations to advance vaccine development against Chagas disease is the high number of variables that must be considered and the lack of uniform criteria among research laboratories. To make possible comparisons, much of this review will be focused on experiments that kept many variables constant including antigen mass/doses, type of eukaryotic plasmid, DNA-delivery system, mice strain and sex, lethal and sublethal model of infection, and similar immunogenicity and efficacy assessments.

Immunity and vaccine development efforts against Trypanosoma cruzi

Trypanosoma cruzi (T. cruzi) is the causative agent for Chagas disease (CD). There is a critical lack of methods for prevention of infection or treatment of acute infection and chronic disease. Studies in experimental models have suggested that the protective immunity against T. cruzi infection requires the elicitation of Th1 cytokines, lytic antibodies and the concerted activities of macrophages, T helper cells, and cytotoxic T lymphocytes (CTLs). In this review, we summarize the research efforts in vaccine development to date and the challenges faced in achieving an efficient prophylactic or therapeutic vaccine against human CD.

Advances in nanocarriers as drug delivery systems in Chagas disease

Chagas disease is one of the most important public health problems in Latin America due to its high mortality and morbidity levels. There is no effective treatment for this disease since drugs are usually toxic with low bioavailability. Serious efforts to achieve disease control and eventual eradication have been unsuccessful to date, emphasizing the need for rapid diagnosis, drug development, and a reliable vaccine. Novel systems for drug and vaccine administration based on nanocarriers represent a promising avenue for Chagas disease treatment. Nanoparticulate systems can reduce toxicity, and increase the efficacy and bioavailability of active compounds by prolonging release, and therefore improve the therapeutic index. Moreover, nanoparticles are able to interact with the host's immune system, modulating the immune response to favour the elimination of pathogenic microorganisms. In addition, new advances in diagnostic assays, such as nanobiosensors, are beneficial in that they enable precise identification of the pathogen. In this review, we provide an overview of the strategies and nanocarrier-based delivery systems for antichagasic agents, such as liposomes, micelles, nanoemulsions, polymeric and non-polymeric nanoparticles. We address recent progress, with a particular focus on the advances of nanovaccines and nanodiagnostics, exploring new perspectives on Chagas disease treatment.

TcG2/TcG4 DNA Vaccine Induces Th1 Immunity Against Acute Trypanosoma cruzi Infection: Adjuvant and Antigenic Effects of Heterologous T. rangeli Booster Immunization

Background: Chagas cardiomyopathy is caused by Trypanosoma cruzi (Tc). Two antigenic candidates, TcG2 and TcG4, are recognized by antibodies in naturally infected dogs and humans; and these vaccine candidates provided protection from Tc infection in mice and dogs. Trypanosoma rangeli (Tr) is non-pathogenic to mammals and shown to elicit cross-reactive anti-Tc antibodies. In this study, we investigated if fixed Tr (fTr) can further enhance the efficacy of the TcG2/TcG4 DNA vaccine.

Methods and Results: C57BL/6 mice were immunized with TcG2/TcG4 DNA vaccine and fTr (delivered as an adjuvant or in prime-boost approach), and challenged with Tc. Serology studies showed that fTr (±quil-A) elicited Tc- and Tr-reactive IgGs that otherwise were not stimulated by TcG2/TcG4 vaccine only, and quil-A had suppressive effects on fTr-induced IgGs. After challenge infection, TcG2/TcG4-vaccinated mice exhibited potent expansion of antigen- and Tc-specific IgGs that were not boosted by fTr±quil-A. Flow cytometry analysis showed that TcG2/TcG4-induced dendritic cells (DC) and macrophages (Mφ) responded to challenge infection by expression of markers of antigen uptake, processing, and presentation, and production of pro-inflammatory cytokines. TcG2/TcG4-induced CD4⁺T cells acquired Th1 phenotype and expressed markers that orchestrate adaptive immunity. A fraction of vaccine-induced CD4⁺T cells exhibited iTreg phenotype responsible for aversion of self-injurious immune responses. Further, TcG2/TcG4-vaccinated mice exhibited potent expansion of poly-functional CD8⁺T cells with TNF-α/IFN-γ production and cytolytic phenotype post-infection. Subsequently, tissue parasites and pathology were hardly detectable in TcG2/TcG4-vaccinated/infected mice. Inclusion of fTr±quil-A had no clear additive effects in improving the Tc-specific adaptive immunity and parasite control than was noted in mice vaccinated with TcG2/TcG4 alone. Non-vaccinated mice lacked sufficient activation of Th1 CD4⁺/CD8⁺T cells, and exhibited >10-fold higher levels of tissue parasite burden than was noted in vaccinated/infected mice.

Conclusion:TcG2/TcG4 vaccine elicits highly effective immunity, and inclusion of fTr is not required to improve the efficacy of DNA vaccine against acute Tc infection in mice.

Evaluation of pathogen P21 protein as a potential modulator of the protective immunity induced by Trypanosoma cruzi attenuated parasites

BACKGROUND

TcP21 is a ubiquitous secreted protein of Trypanosoma cruzi and its recombinant form (rP21) promotes parasite cell invasion and acts as a phagocytosis inducer by activating actin polymerisation in the host cell.

OBJECTIVE

Our goal was to evaluate if the additional supplementation of rP21 during a prime/boost/challenge scheme with T. cruzi TCC attenuated parasites could modify the well-known protective behavior conferred by these parasites.

METHODS

The humoral immune response was evaluated through the assessment of total anti-T. cruzi antibodies as well as IgG subtypes. IFN-γ, TNF-α and IL-10 were measured in supernatants of splenic cells stimulated with total parasite homogenate or rP21.

FINDINGS

Our results demonstrated that, when comparing TCC+rP21 vs. TCC vaccinated animals, the levels of IFN-γ were significantly higher in the former group, while the levels of IL-10 and TNF-α were significantly lower. Further, the measurement of parasite load after lethal challenge showed an exacerbated infection and parasite load in heart and skeletal muscle after pre-treatment with rP21, suggesting the important role of this protein during parasite natural invasion process.

MAIN CONCLUSION

Our results demonstrated that rP21 may have adjuvant capacity able to modify the cytokine immune profile elicited by attenuated parasites.

Clair RM, Vincent JJ, Monroy MC, Stevens L. Chagas disease vector blood meal sources identified by protein mass spectrometry

Chagas disease is a complex vector borne parasitic disease involving blood feeding Triatominae (Hemiptera: Reduviidae) insects, also known as kissing bugs, and the vertebrates they feed on. This disease has tremendous impacts on millions of people and is a global health problem. The etiological agent of Chagas disease, Trypanosoma cruzi (Kinetoplastea: Trypanosomatida: Trypanosomatidae), is deposited on the mammalian host in the insect’s feces during a blood meal, and enters the host’s blood stream through mucous membranes or a break in the skin. Identifying the blood meal sources of triatomine vectors is critical in understanding Chagas disease transmission dynamics, can lead to identification of other vertebrates important in the transmission cycle, and aids management decisions. The latter is particularly important as there is little in the way of effective therapeutics for Chagas disease. Several techniques, mostly DNA-based, are available for blood meal identification. However, further methods are needed, particularly when sample conditions lead to low-quality DNA or to assess the risk of human cross-contamination. We demonstrate a proteomics-based approach, using liquid chromatography tandem mass spectrometry (LC-MS/MS) to identify host-specific hemoglobin peptides for blood meal identification in mouse blood control samples and apply LC-MS/MS for the first time to Triatoma dimidiata insect vectors, tracing blood sources to species. In contrast to most proteins, hemoglobin, stabilized by iron, is incredibly stable even being preserved through geologic time. We compared blood stored with and without an anticoagulant and examined field-collected insect specimens stored in suboptimal conditions such as at room temperature for long periods of time. To our knowledge, this is the first study using LC-MS/MS on field-collected arthropod disease vectors to identify blood meal composition, and where blood meal identification was confirmed with more traditional DNA-based methods. We also demonstrate the potential of synthetic peptide standards to estimate relative amounts of hemoglobin acquired when insects feed on multiple blood sources. These LC-MS/MS methods can contribute to developing Ecohealth control strategies for Chagas disease transmission and can be applied to other arthropod disease vectors.

Effects of IFN-γ coding plasmid supplementation in the immune response and protection elicited by Trypanosoma cruzi attenuated parasites

BACKGROUND

Previous studies showed that a naturally attenuated strain from Trypanosoma cruzi triggers an immune response mainly related to a Th2-type profile. Albeit this, a strong protection against virulent challenge was obtained after priming mice with this attenuated strain. However, this protection is not enough to completely clear parasites from the host. In T. cruzi infection, early Interferon-gamma (IFN-γ) is critical to lead type 1 responses able to control intracellular parasites. Therefore we evaluated whether the co-administration of a plasmid encoding murine IFN-γ could modify the immune response induced by infection with attenuated parasites and improve protection against further infections.

METHODS

C57BL/6J mice were infected intraperitoneally with three doses of live attenuated parasites in combination with plasmid pVXVR-mIFN-γ. Before each infection dose, sera samples were collected for parasite specific antibodies determination and cytokine quantification. To evaluate the recall response to T. cruzi, mice were challenged with virulent parasites 30 days after the last dose and parasite load in peripheral blood and heart was evaluated.

RESULTS

As determined by ELISA, significantly increase in T. cruzi specific antibodies response was detected in the group in which pVXVR-mIFN-γ was incorporated, with a higher predominance of IgG2a subtype in comparison to the group of mice only inoculated with attenuated parasites. At our limit of detection, serum levels of IFN-γ were not detected, however a slight decrease in IL-10 concentrations was observed in groups in which pVXVR-mIFN-γ was supplemented. To analyze if the administration of pVXVR-mIFN-γ has any beneficial effect in protection against subsequent infections, all experimental groups were submitted to a lethal challenge with virulent bloodstream trypomastigotes. Similar levels of challenge parasites were detected in peripheral blood and heart of mice primed with attenuated parasites alone or combined with plasmid DNA. Expansion of IgG antibodies was not significant in TCC+ pVXVR-mIFN-γ; however, the overall tendency to sustain a Th2 profile was maintained.

CONCLUSIONS

Overall, these results suggest that administration of plasmid pVXVR-mIFN-γ could have beneficial effects on host specific antibody production in response to T. cruzi attenuated infection; however, this outcome is not reflected in an improved protection against further virulent infections.

Immunomics: a 21st century approach to vaccine development for complex pathogens

Immunomics is a relatively new field of research which integrates the disciplines of immunology, genomics, proteomics, transcriptomics and bioinformatics to characterize the host-pathogen interface. Herein, we discuss how rapid advances in molecular immunology, sophisticated tools and molecular databases are facilitating in-depth exploration of the immunome. In our opinion, an immunomics-based approach presides over traditional antigen and vaccine discovery methods that have proved ineffective for highly complex pathogens such as the causative agents of malaria, tuberculosis and schistosomiasis that have evolved genetic and immunological host-parasite adaptations over time. By using an integrative multidisciplinary approach, immunomics offers enormous potential to advance 21st century antigen discovery and rational vaccine design against complex pathogens such as the Plasmodium parasite.

Antibiotic-free selection in biotherapeutics: now and forever

The continuously improving sophistication of molecular engineering techniques gives access to novel classes of bio-therapeutics and new challenges for their production in full respect of the strengthening regulations. Among these biologic agents are DNA based vaccines or gene therapy products and to a lesser extent genetically engineered live vaccines or delivery vehicles. The use of antibiotic-based selection, frequently associated with genetic manipulation of microorganism is currently undergoing a profound metamorphosis with the implementation and diversification of alternative selection means. This short review will present examples of alternatives to antibiotic selection and their context of application to highlight their ineluctable invasion of the bio-therapeutic world.