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Review
. 2023 Mar 25;11(4):733.
doi: 10.3390/vaccines11040733.

Nanoparticles as a Delivery System of Antigens for the Development of an Effective Vaccine against Toxoplasma gondii

Carina Brito  1 , Camila Lourenço  1 , Joana Magalhães  2 , Salette Reis  2 , Margarida Borges  1   3
Affiliations
Review

Nanoparticles as a Delivery System of Antigens for the Development of an Effective Vaccine against Toxoplasma gondii

Carina Brito et al. Vaccines (Basel). .

Abstract

Nanoparticles include particles ranging in size from nanometers to micrometers, whose physicochemical characteristics are optimized to make them appropriate delivery vehicles for drugs or immunogens important in the fight and/or prevention of infectious diseases. There has been a rise in the use of nanoparticles in preventive vaccine formulations as immunostimulatory adjuvants, and as vehicles for immunogen delivery to target immune cells. Toxoplasma is important worldwide, and may cause human toxoplasmosis. In immunocompetent hosts, infection is usually asymptomatic, but in immunocompromised patients it can cause serious neurological and ocular consequences, such as encephalitis and retinochoroiditis. Primary infection during pregnancy may cause abortion or congenital toxoplasmosis. Currently, there is no effective human vaccine against this disease. Evidence has emerged from several experimental studies testing nanovaccines showing them to be promising tools in the prevention of experimental toxoplasmosis. For the present study, a literature review was carried out on articles published over the last 10 years through the PubMed database, pertaining to in vivo experimental models of T. gondii infection where nanovaccines were tested and protection and immune responses evaluated. This review aims to highlight the way forward in the search for an effective vaccine for toxoplasmosis.

Keywords: Toxoplasma gondii; adjuvant; immune system; nanoparticles; toxoplasmosis.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Life cycle of Toxoplasma gondii. 1—Consumption of meat containing cysts by the definitive host (Felidae), followed by the release of bradyzoites, and infection of intestinal epithelial cells; 2—After intense multiplication, gametes are formed; 3—After fertilization, unsporulated oocysts are released in the feces of the definitive host; 4—Intermediate hosts are infected by diverse means, such as by the ingestion of sporulated oocysts (a) and consequently the sporozoites infect the intestinal cells; 5—Conversion of sporozoites into tachyzoites, the rapidly multiplying form; and 6—Host immune responses contribute to the conversion of tachyzoites into bradyzoites, constituting cysts, a slowly replicating form. There are several pathways of intermediate host transmission: (a) ingestion of oocysts present in water, vegetables, or fruits; (b) ingestion of tissue cysts present in undercooked meat; (c) infection with tachyzoites by blood transfusion; (d) infection with cysts through tissue transplantation; and by (e) vertical transmission.
Figure 2
Figure 2
T. gondii immune response. Neutrophils and macrophages phagocytize and kill the parasite by releasing antimicrobial compounds and by producing ROI and NO. Macrophages produce IL-12 activating NK cells and T cells to produce INF-γ. DCs phagocyte the parasite and migrate to lymphoid organs where they present their antigens via MHC I or II to CD8+ cytotoxic T lymphocytes or CD4+ helper T cells, respectively. CD8+ CTL will kill the infected cells by apoptosis, and CD4+ T cells undergo activation and maturation towards a strong Th1 or Th17 response, through the production of IL-17, IL-21, or IL-22. NK, CD8+ T cells and Th1 cells produce IFN-γ, controlling infection. Th2 cells secrete cytokines that stimulate B lymphocytes and consequently the production of antibodies, allowing tachyzoite phagocytosis.
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Grants and funding

Financial support from Fundação para a Ciência e Tecnologia (FCT)/MCTES through national funds to Applied Molecular Biosciences Unit (UCIBIO), UIDP/04378/2020 and the project LA/P/0140/2020 of Associate Laboratory Institute for Health and Bioeconomy (i4HB) and the PhD grant (2021.06472.BD) from FCT for Carina Brito.

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