Immunogenicity and Protective Effect of a Virus-Like Particle Containing the SAG1 Antigen of Toxoplasma gondii as a Potential Vaccine Candidate for Toxoplasmosis

Sow reproductive disorders: a key issue affecting the pig industry

Pig farming is essential to global agricultural economies and food security. However, reproductive disorders in sows significantly impact the economic viability and sustainability of the pig industry. These disorders often result from complex interactions between pathogenic and non-pathogenic factors. Preventing abortions is typically more cost-effective than managing and treating them, particularly in intensive pig farming system. This highlights the importance of comprehensively understanding the underlying causes of abortion in sows. This review explores the factors contributing to sow reproductive disorders, including both non-infectious factors (environmental conditions and management practices) and infectious factors (viruses, bacteria, and parasites). We also outline preventive and control strategies, alongside integrated management approaches, by analyzing the underlying causes and pathogenic mechanisms of pregnancy disorders. Overall, implementing the "One Health" concept in large-scale farming provides an effective strategy to reduce the incidence of sow abortion rate, ensure stable livestock production, and maintain a reliable global pork supply.

Cellular Senescence Contributes to Colonic Barrier Integrity Impairment Induced by Toxoplasma gondii Infection

Toxoplasma gondii (T. gondii) induces gut barrier integrity impairment, which is crucial to the establishment of long-term infection in hosts. Cellular senescence is an imperative event that drives disease progression. Several studies have indicated that T. gondii induces oxidative stress and cell cycle blockade in the tissues of hosts, suggesting cellular senescence induced by the parasite. Here, we explored whether cell senescence is involved in T. gondii-mediated colonic barrier integrity damage in mice. C57BL/6J mice were infected with 10 cysts of T. gondii. Senolytic therapy (dasatinib and quercetin, DQ, a combination therapy for reducing senescent cells) was given by oral gavage 4 weeks post-infection. Alcian blue staining, immunofluorescence, western blot, quantitative PCR (qPCR), and enzyme-linked immunosorbent assay (ELISA) were employed to evaluate the thickness of the colonic mucus layer, the expression profiles of genes and proteins related to tight junction function and cellular senescence in the colonic tissues, and the levels of serum lipopolysaccharides (LPS), respectively. T. gondii-infected mice exhibited deteriorated secreted mucus, shortened length, decreased expression of zonula occludens-1 (ZO-1) and occludin in the colon, accompanied by elevated levels of serum LPS. Moreover, the infection upregulated cell senescence-related markers (p16INK4A, p21CIP1) while inhibiting Lamin B1 expression. In addition, the expression levels of senescence-associated secretory phenotypes (SASPs), including IL-1β, TNF-α, IL-6, MMP9 and CXCL10, were upregulated post-infection. Notably, reducing cell senescence with DQ administration, significantly ameliorated the colonic pathological alterations induced by T. gondii infection. This study uncovers for the first time that cellular senescence contributes to the colonic barrier integrity damage induced by chronic T. gondii infection. Importantly, we provide evidence that senolytic therapy exerts a therapeutic effect on the intestinal pathological lesions.

Protective efficacy of Toxoplasma gondii bivalent MAG1 and SAG1 DNA vaccine against acute toxoplasmosis in BALB/c mice

Toxoplasma gondii can infect a wide range of warm-blooded animals, causing a global toxoplasmosis zoonotic epidemic. Surface antigen 1 (SAG1) protein is expressed at the proliferative tachyzoite stage, whereas matrix antigen 1 (MAG1) is expressed at the bradyzoite and tachyzoite stages. These two proteins were found to perform protective roles in previous studies; however, their synergetic protective efficacy as a DNA vaccine against toxoplasmosis has not been clarified. In this study, we constructed recombinant pcDNA3.1( +)-TgMAG1 (pMAG1), pcDNA3.1( +)-TgSAG1 (pSAG1), and pcDNA3.1( +)-TgMAG1-TgSAG1 (pMAG1-SAG1) plasmids and administered them intramuscularly to immunize mice. The levels of anti-T. gondii IgG in serum and cytokines, such as Interleukin (IL)-4, IL-10, and Interferon (IFN)-γ, in splenocytes were measured using ELISA and the respective culture supernatants. Lethal doses of T. gondii (type I) RH strain tachyzoites were administered to immunized mice, and mortality was assessed. Conversely, mice infected with low doses of tachyzoites were monitored to determine their survival rates, and parasite burden analyses of the brains and livers were conducted. The bivalent TgMAG1 and TgSAG1 DNA vaccines exhibited excellent protective immunity against toxoplasmosis in mice, with higher serum IgG and splenocyte IFN-γ release levels, longer survival days, and reduced parasite burden in the brain and liver tissues (p < 0.05). These findings provide a new perspective for the development of T. gondii vaccines.

Toxoplasma gondii vaccine candidates: a concise review

Toxoplasma gondii is an obligate intracellular parasite that causes toxoplasmosis. It has been shown that the severity of symptoms depends on the functioning of the host immune system. Although T. gondii infection typically does not lead to severe disease in healthy people and after infection, it induces a stable immunity, but it can contribute to severe and even lethal Toxoplasmosis in immunocompromised individuals (AIDS, bone marrow transplant and neoplasia). The antigens that have been proposed to be used in vaccine candidate in various studies include surface antigens and secretory excretions that have been synthesized and evaluated in different studies. In some studies, secretory antigens play an important role in stimulating the host immune response. Various antigens such as SAG, GRA, ROP, ROM, and MAG have been from different strains of T. gondii have been synthesized and their protective effects have been evaluated in animal models in different vaccine platforms including recombinant antigens, nanoparticles, and DNA vaccine. Four bibliographic databases including Science Direct, PubMed Central (PMC), Scopus, and Google Scholar were searched for articles published up to 2020.The current review article focuses on recent studies on the use and usefulness of recombinant antigens, nanoparticles, and DNA vaccines.

Modulation of autophagy as a therapeutic strategy for Toxoplasma gondii infection

Toxoplasma gondii infection is a severe health threat that endangers billions of people worldwide. T. gondii utilizes the host cell membrane to form a parasitophorous vacuole (PV), thereby fully isolating itself from the host cell cytoplasm and making intracellular clearance difficult. PV can be targeted and destroyed by autophagy. Autophagic targeting results in T. gondii killing via the fusion of autophagosomes and lysosomes. However, T. gondii has developed many strategies to suppress autophagic targeting. Accordingly, the interplay between host cell autophagy and T. gondii is an emerging area with important practical implications. By promoting the canonical autophagy pathway or attenuating the suppression of autophagic targeting, autophagy can be effectively utilized in the development of novel therapeutic strategies against T gondii. Here, we have illustrated the complex interplay between host cell mediated autophagy and T. gondii. Different strategies to promote autophagy in order to target the parasite have been elucidated. Besides, we have analyzed some potential new drug molecules from the DrugBank database using bioinformatics tools, which can modulate autophagy. Various challenges and opportunities focusing autophagy mediated T. gondii clearance have been discussed, which will provide new insights for the development of novel drugs against the parasite.

Virus-Like Particles: Revolutionary Platforms for Developing Vaccines Against Emerging Infectious Diseases

Virus-like particles (VLPs) are nanostructures that possess diverse applications in therapeutics, immunization, and diagnostics. With the recent advancements in biomedical engineering technologies, commercially available VLP-based vaccines are being extensively used to combat infectious diseases, whereas many more are in different stages of development in clinical studies. Because of their desired characteristics in terms of efficacy, safety, and diversity, VLP-based approaches might become more recurrent in the years to come. However, some production and fabrication challenges must be addressed before VLP-based approaches can be widely used in therapeutics. This review offers insight into the recent VLP-based vaccines development, with an emphasis on their characteristics, expression systems, and potential applicability as ideal candidates to combat emerging virulent pathogens. Finally, the potential of VLP-based vaccine as viable and efficient immunizing agents to induce immunity against virulent infectious agents, including, SARS-CoV-2 and protein nanoparticle-based vaccines has been elaborated. Thus, VLP vaccines may serve as an effective alternative to conventional vaccine strategies in combating emerging infectious diseases.

VLP-Based Vaccines as a Suitable Technology to Target Trypanosomatid Diseases

Research on vaccines against trypanosomatids, a family of protozoa that cause neglected tropical diseases, such as Chagas disease, leishmaniasis, and sleeping sickness, is a current need. Today, according to modern vaccinology, virus-like particle (VLP) technology is involved in many vaccines, including those undergoing studies related to COVID-19. The potential use of VLPs as vaccine adjuvants opens an opportunity for the use of protozoan antigens for the development of vaccines against diseases caused by Trypanosoma cruzi, Leishmania spp., and Trypanosoma brucei. In this context, it is important to consider the evasion mechanisms of these protozoa in the host and the antigens involved in the mechanisms of the parasite–host interaction. Thus, the immunostimulatory properties of VLPs can be part of an important strategy for the development and evaluation of new vaccines. This work aims to highlight the potential of VLPs as vaccine adjuvants for the development of immunity in complex diseases, specifically in the context of tropical diseases caused by trypanosomatids.