Journal List > Clin Exp Vaccine Res > v.7(2) > 1099680

Foroutan, Zaki, and Ghaffarifar: Recent progress in microneme-based vaccines development against Toxoplasma gondii

Abstract

Toxoplasmosis is a cosmopolitan zoonotic disease, which infect several warm-blooded mammals. More than one-third of the human population are seropositive worldwide. Due to the high seroprevalence of Toxoplasma gondii infection worldwide, the resulting clinical, mental, and economical complications, as well as incapability of current drugs in the elimination of parasites within tissue cysts, the development of a vaccine against T. gondii would be critical. In the past decades, valuable advances have been achieved in order to identification of vaccine candidates against T. gondii infection. Microneme proteins (MICs) secreted by the micronemes play a critical role in the initial stages of host cell invasion by parasites. In this review, we have summarized the recent progress for MIC-based vaccines development, such as DNA vaccines, recombinant protein vaccines, vaccines based on live-attenuated vectors, and prime-boost strategy in different mouse models. In conclusion, the use of live-attenuated vectors as vehicles to deliver and express the target gene and prime-boost regimens showed excellent outcomes in the development of vaccines against toxoplasmosis, which need more attention in the future studies.

Introduction

Toxoplasmosis is a cosmopolitan zoonotic disease, caused by an intracellular protozoan belonging to the Apicomplexa phylum that has a worldwide distribution [123]. Over one third of the human population are chronically infected worldwide [456]. Cats are the only definitive hosts, and several warm-blooded mammals, including humans, rodents, birds, etc. serve as intermediate hosts [3789]. Additionally, Toxoplasma gondii was reported in snakes. Nasiri et al. (2016) [10] in Iran showed that 80.88% (55/68) of the examined snakes were positive by GRA6 gene and sequencing revealed over 98% similarity with T. gondii available sequences in GenBank [10].
A wide range of risk factors are involved in the prevalence of toxoplasmosis, so that they can affect the global/regional epidemiological figure of infection including: close contact with cats or keeping them indoors as pet animals, occupation, place of residence, education level, age, eating raw meat, gender, exposure to soil, the host immune response, etc. [45111213]. In humans, toxoplasmosis is often asymptomatic in immunocompetent persons, although in immunocompromised subjects such as patients with malignancies, human immunodeficiency virus-positive individuals, and organ transplant recipients may be cause severe and progressive complications with poor prognosis or even may result in death if not treated [5131415]. Besides, seronegative pregnant women are other risk groups for T. gondii infection [1617]. Upon maternal infection, fetus is probably to be exposed with transplacental transmission. Toxoplasmosis may cause miscarriage in those pregnant mothers that acquired the infection during their pregnancy [1819]. In general tachyzoites as an infectious form of parasite T. gondii are able to actively invade all nucleated cells of the intermediate host and their replication is ultimately curtailed by protective immune response [20].
The present common primary control measures for men and animals toxoplasmosis depends on chemotherapy. There are very few effective control strategies to limit infection and disease in humans and numerous warm-blooded animals throughout the globe and unfortunately the methods of therapy still could not fulfil entirely the treatment goals [21]. At the moment, the drugs for treatment of toxoplasmosis is a combination of pyrimethamine and sulfadiazine that has several side effects. Furthermore, these drugs are expensive and inadequate, which may result in toxic hypersensitivity reactions and are teratogenic on the fetus as well as they cannot eliminate bradyzoites into tissue cysts [21]. Considering the high prevalence of toxoplasmosis in the world, the resulting clinical, mental, and economical complications, as well as the current common drugs have no effect on the encysted parasites [2212223]; therefore, the development of a vaccine against T. gondii parasite can be important and necessary for preventing infection [2425262728].
In recent decades, numerous advancement has been made in order to identification of vaccine candidates against both chronic and acute toxoplasmosis that could promote an effective immune response. Hence, most of the work in the development of T. gondii vaccines have focused on dense granule antigens (GRA), microneme antigens (MIC), rhoptry antigens, surface antigens (SAG), and some other antigens. In this regard, a wide variety of vaccines such as DNA vaccines, recombinant protein vaccines, etc. have been investigated in many countries [24252627293031323334353637]. Despite of the constant efforts of scientists, there is no commercial vaccine for use in human and animals.

Microneme Proteins (MICs)

During recent decades, the increasing number of articles have focused on the evaluation of the immunogenicity of several functional proteins that involve in motility, adhesion to host cells, migration, invasion, and establishment of the parasitophorous vacuole [3839]. Among these, MICs secreted by the micronemes play a critical role in the initial stages of host cell invasion by parasites that are located at the apical end of the zoite and surrounded by a typical unit membrane [3840]. MICs are produced at the rough endoplasmic reticulum, then are transferred to micronemes by the Golgi apparatus in order to participate in cell attachment. In the other hands, these proteins are released by micronemes after contact between parasites and host cells. Noteworthy, intracellular calcium ion levels are essential for secretion and function of T. gondii MICs in parasites [273841].
The MICs are recognized by specific receptors on the cell membrane of hosts. Various methods (such as the proteomic and genomic approaches) have been used to detect the contents of the micronems in apicomplexan parasites. The electronic-microscope was shown micronemes are composed of electron-dense matrix due to the high protein content with secretory organelles that are important for gliding [3842]. Overall, depending on the species of parasite and the developmental stages, the MIC family includes at least 19 types in mammals (MIC1-12, M2AP, AMA1, ROM1, PLP1, SUB1, TLN4, and SPATR), of which 10 types have been identified with adhesive motifs such as epidermal grow factor (EGF) and chitin binding-like. Noteworthy, these products are essential for adhesion to host cells by parasites [4344]. However, MICs became famous as effective vaccine candidates against T. gondii, due to their basic roles in the early stage of the invasion of host cells by parasites. In this field, many kinds of MICs such as MIC2, MIC3, MIC4, MIC8, MIC11, and MIC13 have been evaluated [40454647484950].
It has been recognized that MIC11 as a soluble protein containing a α-chain and a β-chain tethered by a disulfide bond that take part the early stage of cell invasion. These data suggested that MIC11 protein is able to provoke the humoral and Th1-type immune responses, significant enhancement of interferon-γ (IFN-γ), interleukin (IL)-12, and IL-2 production along with higher survival time, compared to control groups [50], suggesting it could be a potential vaccine candidate. MIC8 is a promising vaccine candidate against acute and chronic toxoplasmosis infection that is expressed in tachyzoite stage of the life cycle and acts as an escorter for soluble adhesions to the cells. Notably, this protein plays a crucial role during the invasion of the parasite into the host cell as well as involved in the intracellular proliferation of parasite. Also, it is introduced as a potent stimulator for specific immune responses [4851]. An excellent article indicated favorable and promising results for MIC8 including increased humoral and cellular immune responses with the predominance of IgG2a over IgG1 (T helper 1 [Th1]-polarized responses), enhanced number of CD4+ and CD8+ T cells (p<0.05), high production of IFN-γ, prolonged survival time, and significant reduction in percentage of brain cyst load [51]. The specific features and main functions of some MICs have been listed in Table 1.

DNA Vaccines

During two recent decades, continuous efforts of researchers have made precious achievements in the development of DNA vaccines against acute and chronic toxoplasmosis [2429]. DNA vaccine as a robust strategy has been developed instead of traditional approaches, because of the following reasons: long-term persistence of immunogenicity, relative stability, absence of any type of microorganism, high safety, cost benefits, ease of handling, etc. [277273].
DNA vaccines in general have shown to be effective for inducing both humoral and cell mediated immune response and also stimulates dendritic cells (DCs) to be matured and makes them strong stimulators of T-cell immunity [242772]. Interestingly, activation of B-cells prevent from the attachment of T. gondii to its host cell receptors depend on the production of specific antibodies that can eliminate the parasite with the help of macrophages (MQs) [74]. As both humoral and cellular immunity responses stimulate during toxoplasmosis infection, Th1 immune response has a critical role to limit the parasite replication and produce cytokines such as IL-2 and IL-12. Also, IL-12 is produced by innate immune cells such as DCs, MQs, neutrophils, and monocytes, which plays an important role in host resistance [24757677]. The natural killer (NK) cells and T-CD8+ and T-CD4+ seem to be an important source of IFN-γ in the early and chronic phases of infection. This cytokine as the adaptive cellular immunity has a key role in the controlling and restriction of the parasite as well as inhibit the reactivation of bradyzoites inside the dormant tissue cysts [7677]. In addition, Th2 cells produce IL-4, IL-5, and IL-10, which contribute to the regulation of cell-mediated immunity response reduction [78].
With a unique design strategy of DNA vaccine, it can induce cytotoxic T lymphocytes and helper immune responses with the cooperation of major histocompatibility complex pathways. Moreover, the immunity against T. gondii can be stimulated, so that several antigens can be detected from different epitopes at the same time [7273]. DNA vaccines can be injected through different routes such as, intramuscular, subcutaneous, mucosal, or transdermal [2773]. After the injection, the naked DNA plasmid enter to the cell cytoplasm in order to express encoded proteins within the host cells. As a result, induces a strong immune response [72].
Recent studies showed that the use of genetic and non-genetic adjuvants have become popular in order to provide sufficient immunity [24272979]. It should be mentioned that adjuvants have an important role to improve the efficacy of a vaccine by enhance either the magnitude or time of DNA expression and recruiting the immune cells to the site of injection. Also, they are used in order to help the uptake of DNA into host cells as well as increase taken up by professional antigen-presenting cells [2772]. Several publications have demonstrated that cytokines such as (IFN-γ, IL-12, IL-15, IL-21, etc.), chemokines, and costimulatory molecules (B7-1, B7-2, etc.) as adjuvant, could boost the effectiveness of DNA vaccines [2433465171798081]. For instance, IL-21 synergizes with IL-15 to enhance the generation of CD8+ memory T cells and NK cell activity. Thus, these cytokines can suggest as a candidate adjuvant against toxoplasmosis [51]. For this purpose, Li et al. (2014) [51] designed an investigation to evaluate the immunogenicity of pVAX-MIC8 plus pVAX/IL-21/IL-15. The findings showed co-administration of MIC8 plus mIL-15 and m-IL-21 cytokines enhanced survival time and improved protective immunity of DNA vaccine [51]. Noteworthy, as a member of germ line-encoded receptor, toll-like receptors (TLRs) have a special ability in the innate and adaptive immune responses to pathogens. Hence, they are the target of new vaccine adjuvants in order to improve the immunogenicity of DNA vaccines [82]. For instance, oligodeoxynucleotides contained CG motifs (CpG ODN) as the TLR-9 ligand and a molecular adjuvant to be effective to enhance the immunogenicity of DNA vaccines [7283].
Recently, several papers have examined the various MICs based on DNA vaccination approach, including MIC2, MIC3, MIC4, MIC6, MIC8, MIC11, MIC13, PLP1, M2AP, AMA1, and SPATR in different mouse models [3245464748495051545558596871848586878889]. Yuan et al. (2013) [49] evaluated the immunoefficacy of TgMIC13. The Kunming mice immunized with pVAX-TgMIC13 showed higher levels of IgG antibodies (p<0.05), T-cells proliferative response, high secretion of IFN-γ, IL-2, IL-4, and IL-10 (p<0.05), increased survival time (p<0.05), and significant reduction in the percentage of brain cysts load (p<0.05), compared with those mice that received phosphate-buffered saline. These data suggest that T. gondii MIC13 is a reasonable vaccine candidate against acute and chronic T. gondii infection [49]. MIC3 as a secreted protein plays an essential role in the attachment and invasion of host cells, which expressed at all stages of the life cycle of T. gondii (tachyzoite, bradyzoite, and sporozoite) and discharged from small secretory vesicles [84]. It has been shown that CBA/J mice vaccinated with a plasmid encoding of MIC3 (pMIC3i) produced a significant cellular immune response with the increased secretion of IFN-γ and IL-2 cytokines. The findings showed the response was increased by the pMIC3i plus the plasmid encoding granulocyte-macrophage colony-stimulating factor (pGM-CSF). Also, the immunized mice showed a dramatic reduction of brain cyst load against an oral challenge with T. gondii 76K cysts, compared with control mice [46]. It has been reported that CD4+ and CD8+ T lymphocytes have a key role in MIC3 DNA vaccine to induce protection. Furthermore, plasmids encoding the EGF-like domains and the Lectin-like domain of MIC3 are involved in the protection [90]. More examples of immunization experiments with DNA vaccines against T. gondii in different mouse models are listed in Supplementary Tables 1 and 2.
Recently, it has been well established that using a combination of multiple antigens to be more effective compared with single antigens, as well as improve the protective immunity against toxoplasmosis either survival duration time and/or brain cyst load [325458]. For instance, Beghetto et al. (2005) [89] evaluated five distinct protein fragments MIC2, MIC4, M2AP, and AMA1 gene products that are recognized by antibodies and T cells from infected individuals. The highest protection with DNA vaccination against T. gondii infection was obtained by immunization of BALB/c mice with plasmid mixture and the brain cyst burden in mice vaccinated with the various proteins was significantly reduced than those in control groups. The authors concluded that microneme gene fragments with the antigenic regions of cyst-specific genes could be useful in vaccination against toxoplasmosis [89]. In another study, Fang et al. [85] examined MIC3 and SAG1 proteins alone or combined together. The BALB/c mice were intraperitoneally immunized with 1×103 tachyzoites of RH strain. The results revealed that single-gene immunization increased humoral immune responses, increased secretion of IFN-γ, and prolonged the survival time, compared with the control groups (p<0.05). On the other hand, those mice that vaccinated with the multi-antigenic DNA vaccine (MIC3/SAG1), boosted the protective immunity in terms of cytokine production and survival time, compared with single gene immunized groups (p<0.05). These observations led to the suggestion that MIC3 with SAG1 together capable to induce long term and significant protection against toxoplasmosis, and also cocktail-vaccine immunization could be employed as an alternative way to providing effective protection against T. gondii infection [85].

Recombinant Protein Vaccines

Over the past decades, considerable progress has been achieved to recognize the molecular biology of the various aspects of T. gondii that resulted to design of different vaccine experiments against toxoplasmosis, based on the subcellular components of the parasite [273843919293]. The family of micronemes are attractive vaccine candidates that are responsible for the host-cell invasion [4353]. One of the alternative ways for the development of vaccine candidates against toxoplasmosis is recombinant subunit vaccines that have high potency to trigger systemic humoral and cell mediated responses as well as they are very important for large-scale production [4094].
MICs promote Th1 response, which is critical in mediating the resistance to T. gondii. In order to evaluate the protective efficacy of recombinant form of MICs, Pinzan et al. (2015) [40] designed a comprehensive study on different recombinant microneme proteins (TgMIC1, TgMIC4, and TgMIC6) and combinations of these proteins (TgMIC1-4 and TgMIC1-4-6). They vaccinated the C57BL/6 (H-2b) mice subcutaneously with TgMIC1 (10 µg), TgMIC4 (10 µg), TgMIC6 (10 µg), TgMIC1-4 (5 µg of each protein), TgMIC1-4-6 (3.3 µg of each protein), or Lac+ (10 µg) emulsified in Freund's complete adjuvant. One month after the last immunization procedure, the mice were orally infected with 40 and 80 cysts of the ME49 strain for chronic and acute toxoplasmosis, respectively. The results indicated that these recombinant protein vaccines significantly enhanced IgG titers, mixed Th1/Th2 responses with the predominance of IgG2b over IgG1, high production of IFN-γ and IL-10 cytokines with strong lymphocyte proliferative responses, as well as the increased survival rate (p<0.05), compared with control groups. Besides, immunization with TgMIC1-4 and TgMIC1-4-6 vaccines boosted the protective efficiency, so that 70% and 80% of immunized mice survived 30-day post challenge, respectively. The brain cyst load in mice vaccinated with the different proteins was reduced than non-vaccinated groups ranging from 27.2%–67.8%. It is well known that multicomponent vaccine has better effects than single antigens. The authors declared that the use of this vaccine offers a promising strategy for conferring protection against toxoplasmosis [40]. More details can be found in Supplementary Tables 3 and 4.

Vaccines Based on Live-Attenuated Vectors

Live-attenuated vectors such as bacteria or viruses are another strategy for enhancing the antigen presentation to the immune system of the host. They can greatly mimic the intracellular niche of T. gondii as well as provokes a strong humoral and cell mediated immune response, due to their intrinsic adjuvant properties [8595]. Also, these vaccines can be delivered by several routes, including intramuscular, intraoral, intranasal, subcutaneous, and intravenous in order to induce effective protection [96].
Recently, recombinant viral vectors have shown great potential and play a critical role to induce humoral and cellular immune responses. Hence, they could be a suitable vector for the development of new vaccines [859596979899]. For instance, it is well known that pseudorabies virus (PRV) has a high capability and remarkable effectiveness to enhance vaccine potency. The study showed that a new recombinant modified PRV expressing TgSAG1 (rPRV-SAG1) and TgMIC3 (rPRV-MIC3) cocktail induced a strong IgG antibody response and significant levels of IFN-γ, IL-2, and IL-10 production as well as increased the survival rate (66.7% survival 28 days, p<0.05) post challenge with 100 tachyzoites of RH strain in BALB/c mice. The authors remarked that expression of protective antigens of T. gondii in PRV is a novel approach towards the development of a vaccine against toxoplasmosis [97].
Virus like particle (VLP) vaccines are genetically engineered complexes of multiple copies of protein antigens in a particulate virus like structure that lacks viral genetic material and therefore cannot replicate [100]. These vaccine types have several advantages as follows [101]:
  • -Well-defined geometry and remarkable uniformity with repetitive and ordered surface structures

  • -Particulate and multivalent nature

  • -Preservation of native antigenic conformation

  • -Safety, as they are absolutely non-infectious and nonreplicating candidates

  • -Higher stability than soluble antigens in extreme environmental conditions

  • -Applicability as vectors for the presentation of foreign antigens

VLP vaccines can stimulate powerful humoral and cellular immune responses, representing one of the most appealing approaches for a vaccine platform by mimicking the main structural and functional characteristics of viruses [101102]. Moreover, they can be produced in insect cell expression systems, where foreign antigens can be displayed [102]. It has been reported that VLPs are being useful and safe as vaccine candidates that could provide stronger and longer-lasting protection against toxoplasmosis [98]. In this case, Lee et al. (2017) [98] reported a novel recombinant VLPs carrying MIC8 and then evaluated the immune response and survival status in BALB/c mice. Interestingly, MIC8 in VLPs able to elicit significantly both humoral and cell mediated responses. After immunization, the levels of IgG antibody in sera and IgA antibody in feces elevated by MIC8 VLP vaccine, compared than controls. The enhanced survival duration (intranasal group 100% protection and intramuscular group 60% protection 16 days after challenging with 1×105 tachyzoites of RH strain) was observed, compared with control mice that died within 12 days. Moreover, the numbers of germinal center B cell (B220+, GL7+) and T cell (CD4+, CD8+) populations increased more obviously, in the group immunized with MIC8 VLP than in the control group. These results provide an effective approach for developing vaccines based on VLPs for protection against the highly virulent RH strain of T. gondii [98]. Supplementary Table 5 listed the examples of immunization with live-attenuated vectors expressing T. gondii antigens in mouse models.

Prime-Boost Strategies

Over the past few years, prime-boost strategy has been evaluated for vaccine development, such as DNA prime/viral vector boost, DNA prime/protein boost, and protein prime/DNA boost that are able to induce both humoral and cell-mediated immune responses against many different pathogens especially intracellular pathogens [597299103104]. Hence, this strategy can be useful to promote the effectiveness of vaccine experiments.
Homologous prime-boost approach involves the similar formulation employed in both the prime and boost regimens, while heterologous prime-boost strategies contains different formulations used in more than one immunization [72105]. The interval between prime and boost is very substantial for vaccine response and high efficacy. Moreover, the arrangement of vaccination schedule undoubtedly could influence the outcome of prime-boost strategies [72106]. Noteworthy, heterologous prime-boost is more likely to be immunogenic against an antigen than the homologous prime-boost [105107]. The advantage of heterologous prime-boost immunization is the induction of a strong cellular immune response and is associated with a higher and more specific antibody response against the vaccine target compared to homologous immunization. It has been reported that in comparison with homologous prime-boost approach with the same DNA vaccine, boosting a primary response with a heterologous vector leads to 4- to 10-fold higher T-cell responses [105]. A DNA or a viral vector, especially adenovirus for priming and a protein-based vaccine as a booster, have been used in heterologous prime-boost strategy [107]. Several different vaccine strategies have been shown to elicit different types of immune response. For example, DNA vaccines or recombinant live vector-based vaccines are able to elicit an efficient cellular immunity, but subunit vaccines commonly trigger a predominant humoral immunity [99105]. Subunit vaccines are based on peptides, proteins or polysaccharides containing protective antigens. However, the recombinant subunit vaccines are poorly immunogenic and usually require some additional components to enhance the potency of protective immunity. Accordingly, the use of some adjuvants and also repeated boost immunizations are suggested to elevate the efficiency of subunit vaccines [105108]. The underlying mechanisms of the effectiveness of prime-boost regimens still remain poorly understood. It is hypothesized that the lower antigen expression from DNA vaccines may preferentially prime Th cell responses with the humoral response being subsequently boosted by the protein or viral vector boost [72]. The examples of heterologous prime-boost vaccination against T. gondii in mouse models have been inserted in Supplementary Table 6.

Conclusion

During the twenty years ago, the different vaccine types with various strategies have been evaluated throughout the globe. Despite of the continuous efforts of scientists, there is no available licensed vaccine for use in human and animals. Thus, the development of an efficient vaccine urgently required to prevent and limit the infection. The use of DNA vaccines encoding MIC2, MIC3, MIC11, M2AP, and AMA1 alone or as mixture increase the survival time/rate in immunized mice (see Supplementary Tables 1 and 2). Furthermore, the use of recombinant protein vaccines showed an elevated survival rate (up to 80% protection). Nevertheless, these investigations failed to report complete protection. The use of live-attenuated vectors as vehicles to deliver and express the target gene and prime-boost regimens are excellent strategies for vaccine development, which need more attention in the future studies. Reportedly, it has been verified that the use of genetic and non-genetic adjuvants is very effective, because of their potential ability in boosting specific and long-lasting protective immunity. Collectively, the obtained findings are widely diverse, but valuable advacements have been achieved, so that they gave promising perspectives for the future investigations. However, several limitations may affect the outcome of the experimental studies such as: unsuitable immunization protocol, inadequate evaluation criterion, the strain of parasite, evaluation criterion, the vaccine construct, dosage of inoculum, the delivery route, the different mouse models, etc. The future experiments must address the all these aspects to minimize the faults. In the other hands, optimize immunization protocol and use of various types of delivery systems, traditional and/or molecular adjuvants undoubtedly would affect the outcomes.

References

1. Dubey JP. The history of Toxoplasma gondii: the first 100 years. J Eukaryot Microbiol. 2008; 55:467–475. PMID: 19120791.
2. Foroutan M, Dalvand S, Daryani A, et al. Rolling up the pieces of a puzzle: a systematic review and meta-analysis of the prevalence of toxoplasmosis in Iran. Alexandria J Med. 2017; 6. 23. [Epub]. DOI: 10.1016/j.ajme.2017.06.003.
crossref
3. Rostami A, Riahi SM, Fakhri Y, et al. The global seroprevalence of Toxoplasma gondii among wild boars: a systematic review and meta-analysis. Vet Parasitol. 2017; 244:12–20. PMID: 28917302.
crossref
4. Foroutan-Rad M, Majidiani H, Dalvand S, et al. Toxoplasmosis in blood sonors: a systematic review and meta-analysis. Transfus Med Rev. 2016; 30:116–122. PMID: 27145927.
5. Wang ZD, Liu HH, Ma ZX, et al. Toxoplasma gondii infection in immunocompromised patients: a systematic review and meta-analysis. Front Microbiol. 2017; 8:389. PMID: 28337191.
crossref
6. Pappas G, Roussos N, Falagas ME. Toxoplasmosis snapshots: global status of Toxoplasma gondii seroprevalence and implications for pregnancy and congenital toxoplasmosis. Int J Parasitol. 2009; 39:1385–1394. PMID: 19433092.
crossref
7. Khademvatan S, Foroutan M, Hazrati-Tappeh K, et al. Toxoplasmosis in rodents: a systematic review and meta-analysis in Iran. J Infect Public Health. 2017; 10:487–493. PMID: 28237696.
crossref
8. Foroutan M, Majidiani H. Toxoplasma gondii: are there any implications for routine blood screening? Int J Infect. 2018; 5:e62886.
crossref
9. Khademvatan S, Saki J, Yousefi E, Abdizadeh R. Detection and genotyping of Toxoplasma gondii strains isolated from birds in the southwest of Iran. Br Poult Sci. 2013; 54:76–80. PMID: 23444856.
10. Nasiri V, Teymurzadeh S, Karimi G, Nasiri M. Molecular detection of Toxoplasma gondii in snakes. Exp Parasitol. 2016; 169:102–106. PMID: 27522027.
crossref
11. Wei HX, He C, Yang PL, Lindsay DS, Peng HJ. Relationship between cat contact and infection by Toxoplasma gondii in humans: a meta-analysis. Comp Parasitol. 2016; 83:11–19.
crossref
12. Belluco S, Mancin M, Conficoni D, Simonato G, Pietrobelli M, Ricci A. Investigating the determinants of Toxoplasma gondii prevalence in meat: a systematic review and meta-regression. PLoS One. 2016; 11:e0153856. PMID: 27082633.
crossref
13. Majidiani H, Dalvand S, Daryani A, Galvan-Ramirez ML, Foroutan-Rad M. Is chronic toxoplasmosis a risk factor for diabetes mellitus? A systematic review and meta-analysis of case-control studies. Braz J Infect Dis. 2016; 20:605–609. PMID: 27768900.
crossref
14. Foroutan M, Rostami A, Majidiani H, et al. A systematic review and meta-analysis of the prevalence of toxoplasmosis in hemodialysis patients in Iran. Epidemiol Health. 2018; 40:e2018016. PMID: 29748456.
crossref
15. Yousefi E, Foroutan M, Salehi R, Khademvatan S. Detection of acute and chronic toxoplasmosis amongst multi-transfused thalassemia patients in southwest of Iran. J Acute Dis. 2017; 6:120–125.
crossref
16. Foroutan-Rad M, Khademvatan S, Majidiani H, Aryamand S, Rahim F, Malehi AS. Seroprevalence of Toxoplasma gondii in the Iranian pregnant women: a systematic review and meta-analysis. Acta Trop. 2016; 158:160–169. PMID: 26952970.
17. Saki J, Shafieenia S, Foroutan-Rad M. Seroprevalence of toxoplasmosis in diabetic pregnant women in southwestern of Iran. J Parasit Dis. 2016; 40:1586–1589. PMID: 27876989.
crossref
18. Fallahi S, Rostami A, Nourollahpour Shiadeh M, Behniafar H, Paktinat S. An updated literature review on maternal-fetal and reproductive disorders of Toxoplasma gondii infection. J Gynecol Obstet Hum Reprod. 2018; 47:133–140. PMID: 29229361.
crossref
19. Torgerson PR, Mastroiacovo P. The global burden of congenital toxoplasmosis: a systematic review. Bull World Health Organ. 2013; 91:501–508. PMID: 23825877.
crossref
20. Sullivan WJ Jr, Jeffers V. Mechanisms of Toxoplasma gondii persistence and latency. FEMS Microbiol Rev. 2012; 36:717–733. PMID: 22091606.
21. Antczak M, Dzitko K, Dlugonska H. Human toxoplasmosis-searching for novel chemotherapeutics. Biomed Pharmacother. 2016; 82:677–684. PMID: 27470411.
crossref
22. Weiss LM, Dubey JP. Toxoplasmosis: a history of clinical observations. Int J Parasitol. 2009; 39:895–901. PMID: 19217908.
crossref
23. Rostami A, Karanis P, Fallahi S. Advances in serological, imaging techniques and molecular diagnosis of Toxoplasma gondii infection. Infection. 2018; 46:303–315. PMID: 29330674.
crossref
24. Zhang NZ, Wang M, Xu Y, Petersen E, Zhu XQ. Recent advances in developing vaccines against Toxoplasma gondii: an update. Expert Rev Vaccines. 2015; 14:1609–1621. PMID: 26467840.
25. Lim SS, Othman RY. Recent advances in Toxoplasma gondii immunotherapeutics. Korean J Parasitol. 2014; 52:581–593. PMID: 25548409.
crossref
26. Hiszczynska-Sawicka E, Gatkowska JM, Grzybowski MM, Dlugonska H. Veterinary vaccines against toxoplasmosis. Parasitology. 2014; 141:1365–1378. PMID: 24805159.
crossref
27. Foroutan M, Ghaffarifar F. Calcium-dependent protein kinases are potential targets for Toxoplasma gondii vaccine. Clin Exp Vaccine Res. 2018; 7:24–36. PMID: 29399577.
28. Foroutan M, Ghaffarifar F, Sharifi Z, Dalimi A, Pirestani M. Bioinformatics analysis of ROP8 protein to improve vaccine design against Toxoplasma gondii. Infect Genet Evol. 2018; 62:193–204. PMID: 29705360.
crossref
29. Kur J, Holec-Gasior L, Hiszczynska-Sawicka E. Current status of toxoplasmosis vaccine development. Expert Rev Vaccines. 2009; 8:791–808. PMID: 19485758.
crossref
30. Vazini H, Ghafarifar F, Sharifi Z, Dalimi A. Evaluation of immune responses induced by GRA7 and ROP2 genes by DNA vaccine cocktails against acute toxoplasmosis in BALB/c mice. Avicenna J Med Biotechnol. 2018; 10:2–8. PMID: 29296260.
31. Naserifar R, Ghaffarifar F, Dalimi A, Sharifi Z, Solhjoo K, Hosseinian Khosroshahi K. Evaluation of immunogenicity of cocktail DNA vaccine containing plasmids encoding complete GRA5, SAG1, and ROP2 antigens of Toxoplasma gondii in BALB/C mice. Iran J Parasitol. 2015; 10:590–598. PMID: 26811726.
32. Ghaffarifar F, Naserifar R, Jafari Madrak M. Eukaryotic plasmids with Toxoplasma gondii dense granule antigen (GRA5) and microneme 3 (MIC3) genes as a cocktail DNA vaccine and evaluation of immune responses in BALB/C mice. J Clin Med Genomics. 2014; 3:121.
crossref
33. Khosroshahi KH, Ghaffarifar F, Sharifi Z, et al. Comparing the effect of IL-12 genetic adjuvant and alum non-genetic adjuvant on the efficiency of the cocktail DNA vaccine containing plasmids encoding SAG-1 and ROP-2 of Toxoplasma gondii. Parasitol Res. 2012; 111:403–411. PMID: 22350714.
crossref
34. Eslamirad Z, Dalimi A, Ghaffarifar F, Sharifi Z, Hosseini AZ. Induction of protective immunity against toxoplasmosis in mice by immunization with a plasmid encoding Toxoplama gondii ROP1 gene. Afr J Biotechnol. 2012; 11:8735–8741.
crossref
35. Hoseinian Khosroshahi K, Ghaffarifar F, D'Souza S, Sharifi Z, Dalimi A. Evaluation of the immune response induced by DNA vaccine cocktail expressing complete SAG1 and ROP2 genes against toxoplasmosis. Vaccine. 2011; 29:778–783. PMID: 21095254.
crossref
36. Solhjoo K, Ghaffari Far F, Dalimi-Asl A, Sharifi Z. Enhancement of antibody immune response to a Toxoplasma gondii SAGl-encoded DNA vaccine by formulation with aluminum phosphate. J Med Sci. 2007; 7:361–367.
37. Chen J, Li ZY, Petersen E, Huang SY, Zhou DH, Zhu XQ. DNA vaccination with genes encoding Toxoplasma gondii antigens ROP5 and GRA15 induces protective immunity against toxoplasmosis in Kunming mice. Expert Rev Vaccines. 2015; 14:617–624. PMID: 25749394.
38. Liu Q, Li FC, Zhou CX, Zhu XQ. Research advances in interactions related to Toxoplasma gondii microneme proteins. Exp Parasitol. 2017; 176:89–98. PMID: 28286325.
crossref
39. Liu WG, Xu XP, Chen J, Xu QM, Luo SL, Zhu XQ. MIC16 gene represents a potential novel genetic marker for population genetic studies of Toxoplasma gondii. BMC Microbiol. 2016; 16:101. PMID: 27277196.
crossref
40. Pinzan CF, Sardinha-Silva A, Almeida F, et al. Vaccination with recombinant microneme proteins confers protection against experimental toxoplasmosis in mice. PLoS One. 2015; 10:e0143087. PMID: 26575028.
crossref
41. Kim K. Role of proteases in host cell invasion by Toxoplasma gondii and other Apicomplexa. Acta Trop. 2004; 91:69–81. PMID: 15158690.
crossref
42. Carruthers VB, Tomley FM. Microneme proteins in apicomplexans. Subcell Biochem. 2008; 47:33–45. PMID: 18512339.
crossref
43. Wang Y, Yin H. Research advances in microneme protein 3 of Toxoplasma gondii. Parasit Vectors. 2015; 8:384. PMID: 26194005.
crossref
44. Dowse T, Soldati D. Host cell invasion by the apicomplexans: the significance of microneme protein proteolysis. Curr Opin Microbiol. 2004; 7:388–396. PMID: 15358257.
crossref
45. Dautu G, Munyaka B, Carmen G, et al. Toxoplasma gondii: DNA vaccination with genes encoding antigens MIC2, M2AP, AMA1 and BAG1 and evaluation of their immunogenic potential. Exp Parasitol. 2007; 116:273–282. PMID: 17379212.
crossref
46. Ismael AB, Sekkai D, Collin C, Bout D, Mevelec MN. The MIC3 gene of Toxoplasma gondii is a novel potent vaccine candidate against toxoplasmosis. Infect Immun. 2003; 71:6222–6228. PMID: 14573640.
47. Wang H, He S, Yao Y, et al. Toxoplasma gondii: protective effect of an intranasal SAG1 and MIC4 DNA vaccine in mice. Exp Parasitol. 2009; 122:226–232. PMID: 19366622.
crossref
48. Liu MM, Yuan ZG, Peng GH, et al. Toxoplasma gondii microneme protein 8 (MIC8) is a potential vaccine candidate against toxoplasmosis. Parasitol Res. 2010; 106:1079–1084. PMID: 20177910.
crossref
49. Yuan ZG, Ren D, Zhou DH, et al. Evaluation of protective effect of pVAX-TgMIC13 plasmid against acute and chronic Toxoplasma gondii infection in a murine model. Vaccine. 2013; 31:3135–3139. PMID: 23707448.
crossref
50. Tao Q, Fang R, Zhang W, et al. Protective immunity induced by a DNA vaccine-encoding Toxoplasma gondii microneme protein 11 against acute toxoplasmosis in BALB/c mice. Parasitol Res. 2013; 112:2871–2877. PMID: 23749087.
crossref
51. Li ZY, Chen J, Petersen E, et al. Synergy of mIL-21 and mIL-15 in enhancing DNA vaccine efficacy against acute and chronic Toxoplasma gondii infection in mice. Vaccine. 2014; 32:3058–3065. PMID: 24690150.
crossref
52. Lourenco EV, Pereira SR, Faca VM, et al. Toxoplasma gondii micronemal protein MIC1 is a lactose-binding lectin. Glycobiology. 2001; 11:541–547. PMID: 11447133.
crossref
53. Brossier F, David Sibley L. Toxoplasma gondii: microneme protein MIC2. Int J Biochem Cell Biol. 2005; 37:2266–2272. PMID: 16084754.
crossref
54. Qu D, Han J, Du A. Evaluation of protective effect of multiantigenic DNA vaccine encoding MIC3 and ROP18 antigen segments of Toxoplasma gondii in mice. Parasitol Res. 2013; 112:2593–2599. PMID: 23591483.
crossref
55. Fang R, Nie H, Wang Z, et al. Protective immune response in BALB/c mice induced by a suicidal DNA vaccine of the MIC3 gene of Toxoplasma gondii. Vet Parasitol. 2009; 164:134–140. PMID: 19592172.
crossref
56. Garcia-Reguet N, Lebrun M, Fourmaux MN, et al. The microneme protein MIC3 of Toxoplasma gondii is a secretory adhesin that binds to both the surface of the host cells and the surface of the parasite. Cell Microbiol. 2000; 2:353–364. PMID: 11207591.
crossref
57. Shen B, Sibley LD. The moving junction, a key portal to host cell invasion by apicomplexan parasites. Curr Opin Microbiol. 2012; 15:449–455. PMID: 22445360.
crossref
58. Gong P, Cao L, Guo Y, et al. Toxoplasma gondii: Protective immunity induced by a DNA vaccine expressing GRA1 and MIC3 against toxoplasmosis in BALB/c mice. Exp Parasitol. 2016; 166:131–136. PMID: 27059254.
crossref
59. Yang D, Liu J, Hao P, et al. MIC3, a novel cross-protective antigen expressed in Toxoplasma gondii and Neospora caninum. Parasitol Res. 2015; 114:3791–3799. PMID: 26141436.
crossref
60. Zheng B, He A, Gan M, Li Z, He H, Zhan X. MIC6 associates with aldolase in host cell invasion by Toxoplasma gondii. Parasitol Res. 2009; 105:441–445. PMID: 19308454.
crossref
61. Kessler H, Herm-Gotz A, Hegge S, et al. Microneme protein 8: a new essential invasion factor in Toxoplasma gondii. J Cell Sci. 2008; 121(Pt 7):947–956. PMID: 18319299.
62. Meissner M, Reiss M, Viebig N, et al. A family of transmembrane microneme proteins of Toxoplasma gondii contain EGF-like domains and function as escorters. J Cell Sci. 2002; 115:563–574. PMID: 11861763.
63. Harper JM, Zhou XW, Pszenny V, Kafsack BF, Carruthers VB. The novel coccidian micronemal protein MIC11 undergoes proteolytic maturation by sequential cleavage to remove an internal propeptide. Int J Parasitol. 2004; 34:1047–1058. PMID: 15313131.
crossref
64. Friedrich N, Santos JM, Liu Y, et al. Members of a novel protein family containing microneme adhesive repeat domains act as sialic acid-binding lectins during host cell invasion by apicomplexan parasites. J Biol Chem. 2010; 285:2064–2076. PMID: 19901027.
crossref
65. Hehl AB, Lekutis C, Grigg ME, et al. Toxoplasma gondii homologue of plasmodium apical membrane antigen 1 is involved in invasion of host cells. Infect Immun. 2000; 68:7078–7086. PMID: 11083833.
66. Santos JM, Ferguson DJ, Blackman MJ, Soldati-Favre D. Intramembrane cleavage of AMA1 triggers Toxoplasma to switch from an invasive to a replicative mode. Science. 2011; 331:473–477. PMID: 21205639.
67. Kawase O, Nishikawa Y, Bannai H, Igarashi M, Matsuo T, Xuan X. Characterization of a novel thrombospondin-related protein in Toxoplasma gondii. Parasitol Int. 2010; 59:211–216. PMID: 20144733.
crossref
68. Zheng B, Ding J, Chen X, et al. Immuno-efficacy of a T. gondii secreted protein with an altered thrombospondin repeat (TgSPATR) as a novel DNA vaccine candidate against acute toxoplasmosis in BALB/c mice. Front Microbiol. 2017; 8:216. PMID: 28261175.
crossref
69. Huynh MH, Boulanger MJ, Carruthers VB. A conserved apicomplexan microneme protein contributes to Toxoplasma gondii invasion and virulence. Infect Immun. 2014; 82:4358–4368. PMID: 25092910.
crossref
70. Kafsack BF, Pena JD, Coppens I, Ravindran S, Boothroyd JC, Carruthers VB. Rapid membrane disruption by a perforin-like protein facilitates parasite exit from host cells. Science. 2009; 323:530–533. PMID: 19095897.
crossref
71. Yan HK, Yuan ZG, Petersen E, et al. Toxoplasma gondii: protective immunity against experimental toxoplasmosis induced by a DNA vaccine encoding the perforin-like protein 1. Exp Parasitol. 2011; 128:38–43. PMID: 21310148.
crossref
72. Li L, Petrovsky N. Molecular mechanisms for enhanced DNA vaccine immunogenicity. Expert Rev Vaccines. 2016; 15:313–329. PMID: 26707950.
crossref
73. Doria-Rose NA, Haigwood NL. DNA vaccine strategies: candidates for immune modulation and immunization regimens. Methods. 2003; 31:207–216. PMID: 14511953.
crossref
74. Sayles PC, Gibson GW, Johnson LL. B cells are essential for vaccination-induced resistance to virulent Toxoplasma gondii. Infect Immun. 2000; 68:1026–1033. PMID: 10678903.
75. Denkers EY, Butcher BA, Del Rio L, Bennouna S. Neutrophils, dendritic cells and Toxoplasma. Int J Parasitol. 2004; 34:411–421. PMID: 15003500.
crossref
76. Denkers EY, Gazzinelli RT. Regulation and function of T-cell-mediated immunity during Toxoplasma gondii infection. Clin Microbiol Rev. 1998; 11:569–588. PMID: 9767056.
77. Suzuki Y, Orellana MA, Schreiber RD, Remington JS. Interferon-gamma: the major mediator of resistance against Toxoplasma gondii. Science. 1988; 240:516–518. PMID: 3128869.
78. Mosmann TR, Moore KW. The role of IL-10 in crossregulation of TH1 and TH2 responses. Immunol Today. 1991; 12:A49–A53. PMID: 1648926.
crossref
79. Ghaffarifar F. Strategies of DNA vaccines against toxoplasmosis. Rev Med Microbiol. 2015; 26:88–90.
crossref
80. Xue M, He S, Zhang J, Cui Y, Yao Y, Wang H. Comparison of cholera toxin A2/B and murine interleukin-12 as adjuvants of Toxoplasma multi-antigenic SAG1-ROP2 DNA vaccine. Exp Parasitol. 2008; 119:352–357. PMID: 18442818.
crossref
81. Liu Q, Wang F, Wang G, et al. Toxoplasma gondii: immune response and protective efficacy induced by ROP16/GRA7 multicomponent DNA vaccine with a genetic adjuvant B7-2. Hum Vaccin Immunother. 2014; 10:184–191. PMID: 24096573.
82. Turin L, Riva F. Toll-like receptor family in domestic animal species. Crit Rev Immunol. 2008; 28:513–538. PMID: 19265507.
crossref
83. Greenland JR, Letvin NL. Chemical adjuvants for plasmid DNA vaccines. Vaccine. 2007; 25:3731–3741. PMID: 17350735.
crossref
84. Xiang W, Qiong Z, Li-peng L, Kui T, Jian-wu G, Heng-ping S. The location of invasion-related protein MIC3 of Toxoplasma gondii and protective effect of its DNA vaccine in mice. Vet Parasitol. 2009; 166:1–7. PMID: 19800170.
crossref
85. Fang R, Feng H, Hu M, et al. Evaluation of immune responses induced by SAG1 and MIC3 vaccine cocktails against Toxoplasma gondii. Vet Parasitol. 2012; 187:140–146. PMID: 22336771.
crossref
86. Peng GH, Yuan ZG, Zhou DH, et al. Sequence variation in Toxoplasma gondii MIC4 gene and protective effect of an MIC4 DNA vaccine in a murine model against toxoplasmosis. J Anim Vet Adv. 2010; 9:1463–1468.
crossref
87. Peng GH, Yuan ZG, Zhou DH, et al. Toxoplasma gondii microneme protein 6 (MIC6) is a potential vaccine candidate against toxoplasmosis in mice. Vaccine. 2009; 27:6570–6574. PMID: 19720368.
crossref
88. Yan HK, Yuan ZG, Song HQ, et al. Vaccination with a DNA vaccine coding for perforin-like protein 1 and MIC6 induces significant protective immunity against Toxoplasma gondii. Clin Vaccine Immunol. 2012; 19:684–689. PMID: 22379063.
crossref
89. Beghetto E, Nielsen HV, Del Porto P, et al. A combination of antigenic regions of Toxoplasma gondii microneme proteins induces protective immunity against oral infection with parasite cysts. J Infect Dis. 2005; 191:637–645. PMID: 15655789.
90. Ismael AB, Hedhli D, Cerede O, Lebrun M, Dimier-Poisson I, Mevelec MN. Further analysis of protection induced by the MIC3 DNA vaccine against T. gondii: CD4 and CD8 T cells are the major effectors of the MIC3 DNA vaccine-induced protection, both Lectin-like and EGF-like domains of MIC3 conferred protection. Vaccine. 2009; 27:2959–2966. PMID: 19428907.
crossref
91. Peixoto L, Chen F, Harb OS, et al. Integrative genomic approaches highlight a family of parasite-specific kinases that regulate host responses. Cell Host Microbe. 2010; 8:208–218. PMID: 20709297.
crossref
92. Boothroyd JC, Dubremetz JF. Kiss and spit: the dual roles of Toxoplasma rhoptries. Nat Rev Microbiol. 2008; 6:79–88. PMID: 18059289.
crossref
93. Bradley PJ, Ward C, Cheng SJ, et al. Proteomic analysis of rhoptry organelles reveals many novel constituents for host-parasite interactions in Toxoplasma gondii. J Biol Chem. 2005; 280:34245–34258. PMID: 16002398.
crossref
94. Lourenco EV, Bernardes ES, Silva NM, Mineo JR, Panunto-Castelo A, Roque-Barreira MC. Immunization with MIC1 and MIC4 induces protective immunity against Toxoplasma gondii. Microbes Infect. 2006; 8:1244–1251. PMID: 16616574.
95. Qu D, Yu H, Wang S, Cai W, Du A. Induction of protective immunity by multiantigenic DNA vaccine delivered in attenuated Salmonella typhimurium against Toxoplasma gondii infection in mice. Vet Parasitol. 2009; 166:220–227. PMID: 19740610.
crossref
96. Wang T, Yin H, Li Y, Zhao L, Sun X, Cong H. Vaccination with recombinant adenovirus expressing multi-stage antigens of Toxoplasma gondii by the mucosal route induces higher systemic cellular and local mucosal immune responses than with other vaccination routes. Parasite. 2017; 24:12. PMID: 28367800.
97. Nie H, Fang R, Xiong BQ, et al. Immunogenicity and protective efficacy of two recombinant pseudorabies viruses expressing Toxoplasma gondii SAG1 and MIC3 proteins. Vet Parasitol. 2011; 181:215–221. PMID: 21632181.
crossref
98. Lee SH, Kim AR, Lee DH, Rubino I, Choi HJ, Quan FS. Protection induced by virus-like particles containing Toxoplasma gondii microneme protein 8 against highly virulent RH strain of Toxoplasma gondii infection. PLoS One. 2017; 12:e0175644. PMID: 28406951.
crossref
99. Yin H, Zhao L, Wang T, Zhou H, He S, Cong H. A Toxoplasma gondii vaccine encoding multistage antigens in conjunction with ubiquitin confers protective immunity to BALB/c mice against parasite infection. Parasit Vectors. 2015; 8:498. PMID: 26420606.
crossref
100. Quan FS, Kim Y, Lee S, et al. Viruslike particle vaccine induces protection against respiratory syncytial virus infection in mice. J Infect Dis. 2011; 204:987–995. PMID: 21881112.
crossref
101. Crisci E, Barcena J, Montoya M. Virus-like particles: the new frontier of vaccines for animal viral infections. Vet Immunol Immunopathol. 2012; 148:211–225. PMID: 22705417.
crossref
102. Lee DH, Lee SH, Kim AR, Quan FS. Virus-like nanoparticle vaccine confers protection against Toxoplasma gondii. PLoS One. 2016; 11:e0161231. PMID: 27548677.
crossref
103. Abdian N, Gholami E, Zahedifard F, Safaee N, Rafati S. Evaluation of DNA/DNA and prime-boost vaccination using LPG3 against Leishmania major infection in susceptible BALB/c mice and its antigenic properties in human leishmaniasis. Exp Parasitol. 2011; 127:627–636. PMID: 21187087.
crossref
104. Yu L, Yamagishi J, Zhang S, et al. Protective effect of a prime-boost strategy with plasmid DNA followed by recombinant adenovirus expressing TgAMA1 as vaccines against Toxoplasma gondii infection in mice. Parasitol Int. 2012; 61:481–486. PMID: 22537971.
crossref
105. Kardani K, Bolhassani A, Shahbazi S. Prime-boost vaccine strategy against viral infections: mechanisms and benefits. Vaccine. 2016; 34:413–423. PMID: 26691569.
crossref
106. Ledgerwood JE, Zephir K, Hu Z, et al. Prime-boost interval matters: a randomized phase 1 study to identify the minimum interval necessary to observe the H5 DNA influenza vaccine priming effect. J Infect Dis. 2013; 208:418–422. PMID: 23633407.
crossref
107. Lu S. Heterologous prime-boost vaccination. Curr Opin Immunol. 2009; 21:346–351. PMID: 19500964.
crossref
108. Hansson M, Nygren PA, Stahl S. Design and production of recombinant subunit vaccines. Biotechnol Appl Biochem. 2000; 32(Pt 2):95–107. PMID: 11001870.
crossref

Supplementary Material

Supplementary materials are available at Clinical and Experimental Vaccine Research website (http://www.ecevr.org).

Supplementary Table 1

Baseline characteristics of included studies based on immunization experiments with Toxoplasma gondii DNA-encoding MICs in mouse models (single antigens)
cevr-7-93-s001.pdf

Supplementary Table 2

Baseline characteristics of included studies based on immunization experiments with Toxoplasma gondii DNA-encoding MICs in mouse models (mixed antigens)
cevr-7-93-s002.pdf

Supplementary Table 3

Baseline characteristics of included studies based on immunization experiments with protein vaccines against Toxoplasma gondii in mouse models (single antigens)
cevr-7-93-s003.pdf

Supplementary Table 4

Baseline characteristics of included studies based on immunization experiments with protein vaccines against Toxoplasma gondii in mouse models (mixed antigens)
cevr-7-93-s004.pdf

Supplementary Table 5

Examples of immunization with live-attenuated vectors expressing Toxoplasma gondii MICs in mouse models
cevr-7-93-s005.pdf

Supplementary Table 6

Examples of heterologous prime-boost immunization against Toxoplasma gondii in mouse models
cevr-7-93-s006.pdf
Table 1

The main features and functions of some MICs

cevr-7-93-i001
Antigen Features or major effect on host Reference
MIC1 MIC1 contains a tandemly duplicated domain that is distantly related to the thrombospondin 1-like domain of thrombospondin-related anonymous protein and that specificall binds lactose. [52]
MIC2 MIC2 is essential for parasite viability. [53]
MIC2 plays roles in gliding motility of Toxoplasma gondii, transmigration of biological barriers, and attachment to the surface of host cell.
MIC3 MIC3 is a 90-kDa dimeric soluble protein containing a chitin binding-like domain (CBL), three tandemly repeated epidermal growth factor-like domains (EGF2, EGF3, and EGF4), and two less-conserved EGF domains that overlap with the others (EGF1 and EGF5). [4346545556575859]
MIC3 is an important protein intakes during the invasion of the host cell.
MIC3 is a secreted protein that is expressed in all stages of the T. gondii life cycle.
MIC3 plays an important role in the recognition, adhesion and invasion of host cells by T. gondii.
MIC3 plays important role in the invasion process and take part in forming moving junction of T. gondii.
MIC4 MIC4 localizes in the micronemes of all the invasive forms of T. gondii, tachyzoites, bradyzoites, sporozoites, and merozoites. [47]
MIC6 T he C domain of MIC6 interacts with aldolase, which binds to parasite F-actin, bridging between cell surface adhesion and the parasite actin–myosin motor. [60]
MIC8 MIC8 is expressed in the tachyzoite stage and functions as escorters, targeting soluble adhesins to the micronemes. [486162]
MIC8 is essential for the parasite to invade the host cell.
When MIC8 is not present, a block in invasion is caused by the incapability of the parasite to form a moving junction with the host cell.
MIC11 MIC11 is a soluble microneme protein which is presumably considered facilitating the early stage of cell invasion. [5063]
It is thought to have a role in organizing other MICs for the deployment of adhesive complexes to the apical surface to facilitate host cell invasion.
MIC13 MIC13 plays an important role in attachment and penetration of the host cell by T. gondii. [4964]
MIC13 play an important role in T. gondii propagation, because it has three microneme adhesive repeat domains, which acts as an important determinant in host cell recognition by binding sialylated glycoconjugates on the gut epithelium.
AMA1 AMA1 plays an important role in attachment and invasion of host cells, and thus promoting the parasite replication. [6566]
Anti-TgAMA1 antibodies have been shown to block the host cell-invasion by T. gondii in an in vitro assay of the parasite growth.
SPATR It is a new member in microneme protein family, Ca2+-dependently secreted during early stage of invasion and existed on the outer surface of parasites. [676869]
TgSPATR is contributed to T. gondii invasion and virulence.
Δspatr parasites were -50% reduced in invasion compared to parental strains.
PLP1 TgPLP1 is believed to be involved in the acute virulence of T. gondii in mice. [7071]
TgPLP1-deficient parasites failed to exit normally after intracellular growth, resulting in entrapment within host cells.

MIC, microneme antigens or microneme proteins; AMA1, apical membrane antigen 1; SPATR, secreted protein with an altered thrombospondin repeat; PLP1, perforin-like protein 1.

TOOLS
Similar articles