Recombinant vaccines against T. gondii: comparison between homologous and heterologous vaccination protocols using two viral vectors expressing SAG1

Protective humoral immunity induced by virus-like particles expressing Toxoplasma gondii CST1 or MIC8

Protective efficacy assessment of toxoplasmosis vaccines, at least at the preclinical level, frequently involves lethal dose challenge infection. Nonetheless, their efficacies remain largely unexplored against low infection doses which better reflects how humans become infected in the real world. In this study, we compared the immunity elicited in mice that were heterologously immunized with recombinant baculovirus and virus-like particles expressing either the cyst wall protein (CST1) or microneme protein 8 (MIC8) of Toxoplasma gondii (T. gondii). We also investigated how these vaccines fared against both light and heavy infection intensities of T. gondii ME49. Interestingly, under light infection intensity, vaccines expressing CST1 induced significantly higher mucosal antibody responses than MIC8. Germinal center B (GC B) cell responses were elicited to a greater extent following immunization with either antigen, regardless of the infection dose. Similarly, both antigens suppressed IFN-γ production in the brains upon heavy infection. The overall vaccine-induced protection was also similar for the two vaccine antigens under heavy infection. However, in lightly infected mice, CST1 conferred improved GC B cell induction and further inhibited IFN-γ and cyst burden than those elicited by MIC8, thereby contributing to better protection. These findings indicated that light infection could be used to identify optimal vaccine candidates, thus highlighting the impact of infection intensity in vaccine efficacy evaluations.

Heterologous immunization targeting the CST1 antigen confers better protection than ROP18 in mice

Aim: To evaluate the protective efficacy induced by heterologous immunization with recombinant baculoviruses or virus-like particles targeting the CST1 and ROP18 antigens of Toxoplasma gondii.Materials & methods: Recombinant baculovirus and virus-like particle vaccines expressing T. gondii CST1 or ROP18 antigens were developed to evaluate protective immunity in mice upon challenge infection with 450 Toxoplasma gondii (ME49).Results: Immunization with CST1 or ROP18 vaccines induced similar levels of T. gondii-specific IgG and IgA responses. Compared with ROP 18, CST1 vaccine showed better antibody-secreting cell response, germinal center B cell activation, and significantly reduced brain cyst burden and body weight loss.Conclusion: Our findings suggest that CST1 heterologous immunization elicited better protection than ROP18, providing important insight into improving the toxoplasmosis vaccine design strategy.

A Novel Vaccine Strategy to Prevent Cytauxzoonosis in Domestic Cats

Cytauxzoonosis is caused by Cytauxzoon felis (C. felis), a tick-borne parasite that causes severe disease in domestic cats in the United States. Currently, there is no vaccine to prevent this fatal disease, as traditional vaccine development strategies have been limited by the inability to culture this parasite in vitro. Here, we used a replication-defective human adenoviral vector (AdHu5) to deliver C. felis-specific immunogenic antigens and induce a cell-mediated and humoral immune response in cats. Cats (n = 6 per group) received either the vaccine or placebo in two doses, 4 weeks apart, followed by experimental challenge with C. felis at 5 weeks post-second dose. While the vaccine induced significant cell-mediated and humoral immune responses in immunized cats, it did not ultimately prevent infection with C. felis. However, immunization significantly delayed the onset of clinical signs and reduced febrility during C. felis infection. This AdHu5 vaccine platform shows promising results as a vaccination strategy against cytauxzoonosis.

Recent Advances in the Development of Adenovirus-Vectored Vaccines for Parasitic Infections

Vaccines against parasites have lagged centuries behind those against viral and bacterial infections, despite the devastating morbidity and widespread effects of parasitic diseases across the globe. One of the greatest hurdles to parasite vaccine development has been the lack of vaccine strategies able to elicit the complex and multifaceted immune responses needed to abrogate parasitic persistence. Viral vectors, especially adenovirus (AdV) vectors, have emerged as a potential solution for complex disease targets, including HIV, tuberculosis, and parasitic diseases, to name a few. AdVs are highly immunogenic and are uniquely able to drive CD8+ T cell responses, which are known to be correlates of immunity in infections with most protozoan and some helminthic parasites. This review presents recent developments in AdV-vectored vaccines targeting five major human parasitic diseases: malaria, Chagas disease, schistosomiasis, leishmaniasis, and toxoplasmosis. Many AdV-vectored vaccines have been developed for these diseases, utilizing a wide variety of vectors, antigens, and modes of delivery. AdV-vectored vaccines are a promising approach for the historically challenging target of human parasitic diseases.

Protection Induced by Vaccination with Recombinant Baculovirus and Virus-like Particles Expressing Toxoplasma gondii Rhoptry Protein 18

Heterologous immunization is garnering attention as a promising strategy to improve vaccine efficacy. Vaccines based on recombinant baculovirus (rBV) and virus-like particle (VLP) are safe for use, but heterologous immunization studies incorporating these two vaccine platforms remain unreported to date. Oral immunization is the simplest, most convenient, and safest means for mass immunization. In the present study, mice were immunized with the Toxoplasma gondii rhoptry protein 18 (ROP18)-expressing rBVs (rBVs-ROP18) and VLPs (VLPs-ROP18) via oral, intranasal, and intramuscular (IM) routes to evaluate the protection elicited against the intracellular parasite T. gondii ME49 strain. Overall, boost immunization with VLPs-ROP18 induced a significant increase in T. gondii-specific antibody response in all three immunization routes. Parasite-specific mucosal and cerebral antibody responses were observed from all immunization groups, but the highest mucosal IgA response was detected from the intestines of orally immunized mice. Antibody-secreting cell (ASC), CD8⁺ T cell, and germinal center B cell responses were strikingly similar across all three immunization groups. Oral immunization significantly reduced pro-inflammatory cytokine IL-6 in the brains as well as that by IN and IM. Importantly, all of the immunized mice survived against lethal challenge infections where body weight loss was negligible from all three immunizations. These results demonstrated that protection induced against T. gondii by oral rBV-VLP immunization regimen is just as effective as IN or IM immunizations.

Orally Administrated Recombinant Vaccinia Virus Displaying ROP4 Induces Protection against Toxoplasma gondii Challenge Infection

Recombinant vaccinia viruses (rVVs) are attenuated viruses and are widely utilized as vectored vaccine platforms against numerous diseases. However, the protective efficacy of these rVV vaccines against Toxoplasma gondii and the resulting mucosal immunity has not been thoroughly assessed. Here, rVVs expressing the rhoptry protein 4 (ROP4) of T. gondii were generated. To evaluate the protection induced by the vaccines, mice were orally immunized with the ROP4-rVVs and subsequently challenge-infected with a lethal dose of T. gondii ME49 strain. Immunization with the rVVs induced higher levels of parasite-specific IgG and IgA antibody responses in sera compared to unimmunized control (NC). Upon challenge infection, significantly higher levels of IgG or IgA antibody responses in the brain, intestines, and vaginal samples were found in the immunized mice compared to NC. The ROP4-rVV vaccination elicited potent IgG and IgA secreting cell (ASC) responses, while substantially enhancing germinal center B cell, as well as CD4⁺ and CD8⁺ T cell responses from lymphoid organs. The production of pro-inflammatory cytokines IFN-γ and IL-6 in the brains was markedly diminished following immunization. The immunized mice also experienced reduced bodyweight loss and possessed fewer brain cysts than the control group. These results suggest that oral delivery of ROP4 displaying rVVs induced mucosal and systemic immunities that contributed to protection against lethal T. gondii challenge infection.

Protective efficacy by a novel multi-epitope vaccine, including MIC3, ROP8, and SAG1, against acute Toxoplasma gondii infection in BALB/c mice

Toxoplasma gondii is an intracellular apicomplexan parasite, which can cause a serious infectious disease in pregnant women and immunocompromised individuals. Therefore, the development of a polyvalent vaccine consisting of all stages of the parasite life cycle using the epitopes from tachyzoites, bradyzoites, and sporozoites is likely to be required for complete protective immunity. In this study, we designed protein vaccine candidate based on the prediction of specific epitopes (i.e., B cell and T cell) from three Toxoplasma gondii antigens. The MRS protein (MIC3: 30-180, ROP8: 85-185, and SAG1: 85-235) was expressed in Escherichia coli, and purification was performed using a HisTrap HP column and then we evaluated immunogenicity and protective property in BALB/c mice. Seventy-two mice were randomly divided into six groups, including three vaccinations (i.e., MRS, MRS-Freund, and MRS-Calcium Phosphate Nanoparticles (MRS-CaPNs)) and three control (i.e., Phosphate-buffered saline, Freund, and CaPNs) groups. All groups were immunized three times via subcutaneous injection within three-week intervals. In the vaccination groups, the BALB/c mice were injected with 20 μg of MRS protein for the first time and 10 μg of MRS for the next two times. Antibodies, cytokines, and splenocytes proliferation in the immunized mice were assayed using the enzyme-linked immunosorbent assay. Protective efficacy was analyzed by challenging the immunized mice with T. gondii of RH strain. Antibody, cytokine, and lymphocyte proliferation assays showed that the mice immunized with MRS induced stronger humoral and T helper type 1 cell-mediated immune responses, compared to the control mice. However, co-immunization with adjuvants (i.e., Freund and CaNPs) resulted in impaired immune responses. Effective protection against the parasite achieved an increase in survival time in the immunized mice, especially in the MRS-CaNPs group. The obtained results of the present study demonstrated that multi-epitope protein vaccination, MRS, is a potential strategy against toxoplasmosis infection. In addition, the vaccine co-delivered with CaPNs could provide an important key for vaccine candidate to control T. gondii infection.

Toxoplasma gondii surface antigen 1 (SAG1) as a potential candidate to develop vaccine against toxoplasmosis: A systematic review

Toxoplasma gondii is an intracellular parasite that infects a broad range of animal species and humans. As the main surface antigen of the tachyzoite, SAG1 is involved in the process of recognition, adhesion and invasion of host cells. The aim of the current systematic review study is to clarify the latest status of studies in the literature regarding SAG1-associated recombinant proteins or SAG1-associated recombinant DNAs as potential vaccines against toxoplasmosis. Data were systematically collected from six databases including PubMed, Science Direct, Web of Science, Google Scholar, EBSCO and Scopus, up to 1st of January 2019. A total of 87 articles were eligible for inclusion criteria in the current systematic review. The most common antigens used for experimental cocktail vaccines together with SAG1 were ROP2 and SAG2. In addition, the most parasite strains used were RH and ME49. Freund's adjuvant and cholera toxin have been predominantly utilized. Furthermore, regarding the animal models, route and dose of vaccination, challenge methods, measurement of immune responses and cyst burden have been discussed in the text. Most of these experimental vaccines induce immune responses and have a high degree of protection against parasite infections, increase survival rates and duration and reduce cyst burdens. The data demonstrated that SAG1 antigen has a high potential for use as a vaccine and provided a promising approach for protecting humans and animals against toxoplasmosis.

Evaluation of Immunogenic Effect of Toxoplasma gondii Recombinant SAG-1 Antigen with Propranolol as Adjuvant in BALB/c Mice

Purpose: Propranolol as a novel adjuvant, was used to evaluate the immunogenic effect of three doses of recombinant SAG-1 (rSAG-1) antigen of Toxoplasma gondii in BALB/c mice for finding the optimal dose, and was compared with efficacy of tachyzoite lysate antigen (TLA).

Methods: Eight different groups of 15 BALB/c mice received different volumes of the immunogenic material (three doses of r SAG-1 and one dose of TLA antigens), with or without propranolol adjuvant, subcutaneously. The control group mice received only PBS. Three weeks after the last immunization, the serum levels of IgG2a, IgG1 and IgG total antibodies against TLA, splenic interleukin-5 (IL-5) and Interferon-gamma (IFN-γ) (produced against TLA) and the splenic lymphocyte proliferation after adding TLA were measured to evaluate humoral and cellular immune responses. Challenge test was performed by subcutaneously injection of 1000 alive and active tachyzoites in to five mice per each group and survival days for each group of mice were recorded.

Results: The mice group that received propranolol adjuvant and 20 µg of r SAG-1 antigen per dose of injection showed significantly more IFN-γ production, more proliferation of splenic lymphocytes and higher anti-TLA-specific IgG2a production (three main indexes for cell mediated immunity) in comparison with other groups. Moreover, in the challenge test, this group of mice had a significantly increased survival time, indicating the positive effect of propranolol in the more stimulating of cellular immunity that is necessary for toxoplasmosis prevention or suppress.

Conclusion: Our results showed that T. gondii rSAG-1 antigen in combination with propranolol as adjuvant (which can induce Th1 related responses) are good candidates for further study to a vaccine design.

C57BL/6 mice immunized with synthetic peptides from Toxoplasma gondii surface and microneme immunodominant antigens are able to decrease parasite burden in the brain tissues

Toxoplasmosis is a disease caused by Toxoplasma gondii, an intracellular protozoan able to infect a wide range of hosts. The infection is particularly severe in immunocompromised patients or during pregnancy, circumstances in which the parasite could find a more favorable microenvironment to replicate and invade host tissues. The current treatment consists in toxic drugs for the patients, being not appropriate for the fetuses and immunodeficient patients. So far, there is a lack of available vaccine to prevent the disease. The present study aimed to evaluate the immune response induced by peptides derived from parasite immunodominant proteins from key components, as surface, rhoptry, microneme and dense granule antigens. A panel of eleven peptides was selected considering the highest scores for B cell epitope prediction by in silico analyses. The peptides were divided in groups, according to the parasite organelle locations, and used to immunize C57BL/6 mice. The animals were submitted to three doses of immunization and infected by 10 cysts of T. gondii ME49 strain. Blood samples were collected and used to measure the production of antibodies and cytokines, while the brains were collected to determine the parasite burden by quantitative polymerase chain reaction (qPCR). It was found that synthetic peptides from all targets were able to induce IgG synthesis in immunized mice, as well as to modulate the Th1/Th2 cytokine production, particularly the MIC and SRS groups, which presented the IFN-γ/IL-10 and TNF-α/IL-10 ratios 30 and 10 times higher, respectively, when compared with non-immunized group. Interestingly, the animals from MIC and SRS groups had significantly lower levels of T. gondii DNA in their brains. In summary, it can be concluded that peptides mainly from SRS and MIC parasite components constitute relevant targets to design vaccine candidates against parasite burden observed during chronic toxoplasmosis.

Vaccination challenges and strategies against long-lived Toxoplasma gondii

Since the discovery of Toxoplasma gondii in 1908, it is estimated that one-third of the global population has been exposed to this ubiquitous intracellular protozoan. The complex life cycle of T. gondii has enabled itself to overcome stress and transmit easily within a broad host range thus achieving a high seroprevalence worldwide. To date, toxoplasmosis remains one of the most prevalent HIV-associated opportunistic central nervous system infections. This review presents a comprehensive overview of different vaccination approaches ranging from traditional inactivated whole-T. gondii vaccines to the popular DNA vaccines. Extensive discussions are made to highlight the challenges in constructing these vaccines, selecting adjuvants as well as delivery methods, immunisation approaches and developing study models. Herein we also deliberate over the latest and promising enhancement strategies that can address the limitations in developing an effective T. gondii prophylactic vaccine.

Epitope-based vaccine as a universal vaccination strategy against Toxoplasma gondii infection: A mini-review

Despite the significant progress in the recent efforts toward developing an effective vaccine against toxoplasmosis, the search for new protective vaccination strategy still remains a challenge and elusive goal because it becomes the appropriate way to prevent the disease. Various experimental approaches in the past few years showed that developing a potential vaccine against the disease can be achievable. The combination of multi-epitopes expressing different stages of the parasite life cycle has become an optimal strategy for acquiring a potent, safe, and effective vaccine. Epitope-based vaccines have gained attention as alternative vaccine candidates due to their ability of inducing protective immune responses. This mini-review highlights the current status and the prospects of Toxoplasma gondii vaccine development along with the application of epitope-based vaccine in the future parasite immunization as a novel under development and evaluation strategy.

Evaluation of Protective Immune Response Induced by a DNA Vaccine Encoding GRA8 against Acute Toxoplasmosis in a Murine Model

Toxoplasma gondii is an apicomplexan zoonotic protozoan parasite that infects most species of warm-blooded animals, including humans. The heavy incidence and severe or lethal damage caused by T. gondii infection clearly indicate a need for the development of an effective vaccine. T. gondii GRA8 is a member of the dense granules protein family and is used as a marker of acute infection. In the present study, we evaluated the protective immunity induced by DNA vaccination based on a recombinant eukaryotic plasmid, pDsRed2-GRA8, against acute toxoplasmosis in mice. BALB/c mice were intramuscularly immunized with the pDsRed2-GRA8 plasmid and then challenged by infection with the highly virulent GFP-RH strain of T. gondii. The specific immune responses and protective efficacy against T. gondii of this vaccine were analyzed by measuring cytokine and serum antibody titers, splenocyte proliferation assays, and the survival times of mice after challenge. Our results showed that mice immunized with pDsRed2-GRA8 demonstrated specific humoral and cellular responses, induced higher IgG antibody titers with predominant IgG2a production; increased levels of IL-10, IL-12 (p70), IFN-γ, TNF-α, and splenocyte proliferation; and prolonged survival times compared to those of control mice. The present study showed that DNA immunization with pDsRed2-GRA8 induced humoral and cellular immune responses, and all immunized mice showed greater Th1-type immune responses and longer survival times than those of control mice. These results indicated that T. gondii GRA8 DNA immunization induces a partial protective effect against acute toxoplasmosis.

Immunogenicity of Multiepitope Vaccine Candidate against Toxoplasma gondii Infection in BALB/c Mice

BACKGROUND

Toxoplasma gondii is a widely prevalent intracellular protozoan parasite which causes serious clinical and veterinary problems. Development of an effective vaccine for controlling toxoplasmosis is an extremely important aim. In the present study, the protective efficacy of recombinant multiepitope antigen (USM.TOXO1) expressing nine potential epitopes identified from SAG1, GRA2, and GRA7 of Toxoplasma gondii was evaluated in BALB/c mice.

METHODS

Mice were immunized subcutaneously with three doses of USM.TOXO1 antigen (10 μg/ml). Following the immunization, the IgG antibody, IgG subclass, IFN-γ and IL-4 production were evaluated using ELISA, the study was conducted at Animal Research and Service Center (ARASC), USM Health Campus in 2016.

RESULTS

Mice immunized with USM.TOXO1 significantly induced a mixed Th1/Th2 response polarized toward the IgG1 antibody isotype. While the cytokine analysis revealed a significant release of IFN-γ cytokines.

CONCLUSION

USM.TOXO1 is a potential vaccine candidate that elicits strong immunity in BALB/c mice. The proven immunogenicity of the generated antigen can serve as a premise for further use of epitope-based vaccine in the immunoprevention of human and animal toxoplasmosis.

Protective immune response in mice induced by a suicidal DNA vaccine encoding NTPase-II gene of Toxoplasma gondii

DNA-based alphaviral RNA replicon vectors, also called suicidal DNA vectors, have been employed to alleviate biosafety concerns attribution to its ability to induce apoptotic cell death of the transfected cells. Toxoplasma gondii nucleoside triphosphate hydrolase-II (TgNTPase-II), which facilitates the parasite to salvage purines from the host cell for survival and replication, have been demonstrated to be a potential vaccine candidate for toxoplasmosis. Herein, we evaluated the immunogenic potential of a suicidal DNA vaccine encoding TgNTPase-II gene, pDREP-TgNTPase-II, delivered intramuscularly in combination with electroporation. Immunization of mice with pDREP-TgNTPase-II elicited specific humoral responses, with high IgG antibody titers and a mixed IgG1/IgG2a response. The cellular immune response was associated with high level production of IFN-γ, IL-2, IL-10 cytokines and low level IL-4 production as well as the increase of the percentage of CD8+ T cells, indicating that a Th1 predominant response was elicited. Furthermore, mice vaccinated with this suicidal DNA vaccine displayed partial protection against acute infection with the virulent RH strain as well as chronic infection with PRU cyst, which shows 77.7% and 71.4% reduction in brain cyst burden in comparison to PBS and pDREP-eGFP control group, respectively. Based on the cellular and antibody responses, the suicidal DNA vaccine elicited a Th1-predominant immune response against T. gondii challenge.

Adenovirus Specific Pre-Immunity Induced by Natural Route of Infection Does Not Impair Transduction by Adenoviral Vaccine Vectors in Mice

Recombinant human adenovirus serotype 5 (HAd5V) vectors are gold standards of T-cell immunogenicity as they efficiently induce also humoral responses to exogenous antigens, in particular when used in prime-boost protocols. Some investigators have shown that pre-existing immunity to adenoviruses interferes with transduction by adenoviral vectors, but the actual extent of this interference is not known since it has been mostly studied in mice using unnatural routes of infection and virus doses. Here we studied the effects of HAd5V-specific immune responses induced by intranasal infection on the transduction efficiency of recombinant adenovirus vectors. Of interest, when HAd5V immunity was induced in mice by the natural respiratory route, the pre-existing immunity against HAd5V did not significantly interfere with the B and T-cell immune responses against the transgene products induced after a prime/boost inoculation protocol with a recombinant HAd5V-vector, as measured by ELISA and in vivo cytotoxic T-cell assays, respectively. We also correlated the levels of HAd5V-specific neutralizing antibodies (Ad5NAbs) induced in mice with the levels of Ad5NAb titers found in humans. The data indicate that approximately 60% of the human serum samples tested displayed Ad5NAb levels that could be overcome with a prime-boost vaccination protocol. These results suggest that recombinant HAd5V vectors are potentially useful for prime-boost vaccination strategies, at least when pre-existing immunity against HAd5V is at low or medium levels.

Recent advances in developing vaccines against Toxoplasma gondii: an update

Toxoplasma gondii, a significant public health risk, is able to infect almost all warm-blooded animals including humans, and it results in economic losses in production animals. In the last three years, a large number of vaccination experiments have been performed to control T. gondii infection, with the target of limiting the acute infection and reducing or eliminating tissue cysts in the intermediate hosts. In this paper, we summarize the latest results of the veterinary vaccines against T. gondii infection since 2013. Immunization with live-attenuated whole organisms of non-reverting mutants has been shown to induce remarkably potent immune responses associated with control of acute and chronic toxoplasmosis. The non-cyst-forming mutants are promising new tools for the development of veterinary vaccines against T. gondii infection.

Homologous prime-boost strategy with TgPI-1 improves the immune response and protects highly susceptible mice against chronic Toxoplasma gondii infection

Subunit-based vaccines are safer than live or attenuated pathogen vaccines, although they are generally weak immunogens. Thus, proper combination of immunization strategies and adjuvants are needed to increase their efficacy. We have previously protected C3H/HeN mice from Toxoplasma gondii infection by immunization with the serine protease inhibitor-1 (TgPI-1) in combination with alum. In this work, we explore an original vaccination protocol that combines administration of recombinant TgPI-1 by intradermal and intranasal routes in order to enhance protection in the highly susceptible C57BL/6 strain. Mice primed intradermally with rTgPI-1 plus alum and boosted intranasally with rTgPI-1 plus CpG-ODN elicited a strong specific Th1/Th2 humoral response, along with a mucosal immune response characterized by specific-IgA in intestinal lavages. A positive cellular response of mesentheric lymph node cells and Th1/Th2 cytokine secretion in the ileon were also detected. When immunized mice were challenged with the cystogenic Me49 T. gondii strain, they displayed up to 62% reduction in brain parasite burden. Moreover, adoptive transfer of mesenteric lymph node cells from vaccinated to naïve mice induced significant protection against infection. These results demonstrate that this strategy that combines the administration of TgPI-1 by two different routes, intradermal priming and intranasal boost, improves protective immunity against T. gondii chronic infection in highly susceptible mice.

A rational approach to select immunogenic peptides that induce IFN-γ response against Toxoplasma gondii in human leukocytes

The ideal vaccine to prevent toxoplasmosis in humans would comprise antigens that elicit a protective T cell type 1 response with high IFN-γ production. Here, we report the use of a bioinformatics pipeline to discover peptides based on biochemical characteristics that predict strong IFN-γ response by human leukocytes. We selected peptide sequences that previously were reported to induce IFN-γ to identify the biophysical characteristics that will predict HLA-A*02 high-affinity epitopes. We found that the protein motif pattern FL...L..[VL] was common in previously reported highly immunogenic sequences. We have selected new peptides with a length of 9 residues with affinities from 2 to 21 nM with peptide signal and transmembrane domains and predicted to be cleaved at the proteasome to perform ELISPOT assays with human leukocytes. Within 9 peptides with the highest scores for IFN-γ production, four peptides elicited IFN-γ levels in a range from 252 to 1763 SFC/1e6. Our pipeline uncovered Toxoplasma proteins with peptides that are processed by MHC class 1 in humans. Our results suggest that our rational strategy for the selection of immunogenic epitopes could be used to select peptides as candidates for inclusion in epitope-based vaccines.

Recent advances in Toxoplasma gondii immunotherapeutics

Toxoplasmosis is an opportunistic infection caused by the protozoan parasite Toxoplasma gondii. T. gondii is widespread globally and causes severe diseases in individuals with impaired immune defences as well as congenitally infected infants. The high prevalence rate in some parts of the world such as South America and Africa, coupled with the current drug treatments that trigger hypersensitivity reactions, makes the development of immunotherapeutics intervention a highly important research priority. Immunotherapeutics strategies could either be a vaccine which would confer a pre-emptive immunity to infection, or passive immunization in cases of disease recrudescence or recurrent clinical diseases. As the severity of clinical manifestations is often greater in developing nations, the development of well-tolerated and safe immunotherapeutics becomes not only a scientific pursuit, but a humanitarian enterprise. In the last few years, much progress has been made in vaccine research with new antigens, novel adjuvants, and innovative vaccine delivery such as nanoparticles and antigen encapsulations. A literature search over the past 5 years showed that most experimental studies were focused on DNA vaccination at 52%, followed by protein vaccination which formed 36% of the studies, live attenuated vaccinations at 9%, and heterologous vaccination at 3%; while there were few on passive immunization. Recent progress in studies on vaccination, passive immunization, as well as insights gained from these immunotherapeutics is highlighted in this review.

A Positive Association between T. gondii Seropositivity and Obesity

Obesity is a global public health problem that is linked with morbidity, mortality, and functional limitations and has limited options for sustained interventions. Novel targets for prevention and intervention require further research into the pathogenesis of obesity. Consistently, elevated markers of inflammation have been reported in association with obesity, but their causes and consequences are not well understood. An emerging field of research has investigated the association of infections and environmental pathogens with obesity, potential causes of low grade inflammation that may mediate obesity risk. In this study, we estimate the possible association between Toxoplasma gondii (T. gondii) infection and obesity in a sample of 999 psychiatrically healthy adults. Individuals with psychiatric conditions, including personality disorders, were excluded because of the association between positive serology to T. gondii and various forms of serious mental illness that have a strong association with obesity. In our sample, individuals with positive T. gondii serology had twice the odds of being obese compared to seronegative individuals (p = 0.01). Further, individuals who were obese had significant higher T. gondii IgG titers compared to individuals who were non-obese. Latent T. gondii infection is very common worldwide, so potential public health interventions related to this parasite can have a high impact on associated health concerns.