Lectins from Synadenium carinatum (ScLL) and Artocarpus heterophyllus (ArtinM) Are Able to Induce Beneficial Immunomodulatory Effects in a Murine Model for Treatment of Toxoplasma gondii Infection

The Search for Drugs Derived from Natural Products for Toxoplasma gondii Infection Treatment in the Last 20 Years - A Systematic Review

INTRODUCTION

Toxoplasmosis is a worldwide distributed zoonosis caused by Toxoplasma gondii (T. gondii), an obligate intracellular protozoan. The infection in immunocompetent hosts usually progresses with mild or no symptoms. However, in immunocompromised individuals, this disease can cause severe or fatal symptoms.

METHOD

Sulfadiazine and pyrimethamine are two drugs used as standard therapies for human toxoplasmosis. Although they do not cause chronic infection, they may cause hematological toxicity, hypersensitivity, intolerance, teratogenic effects, gastrointestinal disorders, and bone marrow suppression.

RESULTS

The limited effect, significant toxicity, and emerging resistance to current drugs available to treat T. gondii infections require investigating other effective, nontoxic, and well-tolerated alternatives. Medicinal plants are, traditionally, the most promising sources used to treat infectious diseases Conclusion: This review provides data on new therapeutic and prophylactic methods for T. gondii infection based on the use of extracts and/or compounds derived from natural products, which have been reported to be useful as alternative treatment options in the last 20 years.

Mannose-Binding Lectins as Potent Antivirals against SARS-CoV-2

The SARS-CoV-2 entry into host cells is mainly mediated by the interactions between the viral spike protein (S) and the ACE-2 cell receptor, which are highly glycosylated. Therefore, carbohydrate binding agents may represent potential candidates to abrogate virus infection. Here, we evaluated the in vitro anti-SARS-CoV-2 activity of two mannose-binding lectins isolated from the Brazilian plants Canavalia brasiliensis and Dioclea violacea (ConBR and DVL). These lectins inhibited SARS-CoV-2 Wuhan-Hu-1 strain and variants Gamma and Omicron infections, with selectivity indexes (SI) of 7, 1.7, and 6.5, respectively for ConBR; and 25, 16.8, and 22.3, for DVL. ConBR and DVL inhibited over 95% of the early stages of the viral infection, with strong virucidal effect, and also protected cells from infection and presented post-entry inhibition. The presence of mannose resulted in the complete lack of anti-SARS-CoV-2 activity by ConBR and DVL, recovering virus titers. ATR-FTIR, molecular docking, and dynamic simulation between SARS-CoV-2 S and either lectins indicated molecular interactions with predicted binding energies of -85.4 and -72.0 Kcal/Mol, respectively. Our findings show that ConBR and DVL lectins possess strong activities against SARS-CoV-2, potentially by interacting with glycans and blocking virus entry into cells, representing potential candidates for the development of novel antiviral drugs.

Ovicidal and toxicological effect of hydroalcoholic extracts of Euphorbia milli var splendens, Synadenium carinatum Boiss and Tagetes minuta L. against Ancylostoma spp.: In vitro study

Nematodes of the Ancylostomidae family consist of important parasitic species. The control of such parasitosis represents an important challenge, given the constant high rate of reinfection of some hosts, among which the domestic dog, as well as the high environmental contamination. Another factor that can have a negative influence is the toxicity of the chemicals used for environmental decontamination, highlighting the need to design research to identify new control strategies for this parasitosis, among which the use of plant extracts. Thus, the objective of this research was to evaluate the toxicity and ovicidal activity of hydroalcoholic extracts obtained by percolation of three plants: Tagetes minuta L., Euphorbia milli var splendens (Bojer ex Hook.) Ursch & Leandri and Synadenium carinatum Boiss, against Ancylostoma spp. In addition, these extracts were tested at different concentrations for toxicity against Artemia salina L. and Allium cepa L. It was observed that the hydroalcoholic extract of all plant species evaluated induced moderate ovicide activity at all the tested concentration, with emphasis on E. milii, which was the only plant species that presented significantly low toxicity in the concentration of 12.5 µL/mL when compared to the other species evaluated.

Control of human toxoplasmosis

Toxoplasmosis is caused by Toxoplasma gondii, an apicomplexan parasite that is able to infect any nucleated cell in any warm-blooded animal. Toxoplasma gondii infects around 2 billion people and, whilst only a small percentage of infected people will suffer serious disease, the prevalence of the parasite makes it one of the most damaging zoonotic diseases in the world. Toxoplasmosis is a disease with multiple manifestations: it can cause a fatal encephalitis in immunosuppressed people; if first contracted during pregnancy, it can cause miscarriage or congenital defects in the neonate; and it can cause serious ocular disease, even in immunocompetent people. The disease has a complex epidemiology, being transmitted by ingestion of oocysts that are shed in the faeces of definitive feline hosts and contaminate water, soil and crops, or by consumption of intracellular cysts in undercooked meat from intermediate hosts. In this review we examine current and future approaches to control toxoplasmosis, which encompass a variety of measures that target different components of the life cycle of T. gondii. These include: education programs about the parasite and avoidance of contact with infectious stages; biosecurity and sanitation to ensure food and water safety; chemo- and immunotherapeutics to control active infections and disease; prophylactic options to prevent acquisition of infection by livestock and cyst formation in meat; and vaccines to prevent shedding of oocysts by definitive feline hosts.

The lectin ArtinM activates RBL-2H3 mast cells without inducing degranulation

Mast cells are connective tissue resident cells with morphological and functional characteristics that contribute to their role in allergic and inflammatory processes, host defense and maintenance of tissue homeostasis. Mast cell activation results in the release of pro-inflammatory mediators which are largely responsible for the physiological functions of mast cells. The lectin ArtinM, extracted from Artocarpus heterophyllus (jackfruit), binds to D-manose, thus inducing degranulation of mast cells. ArtinM has several immunomodulatory properties including acceleration of wound healing, and induction of cytokine release. The aim of the present study was to investigate the role of ArtinM in the activation and proliferation of mast cells. The rat mast cell line RBL-2H3 was used throughout this study. At a low concentration (0.25μg/mL), ArtinM induced mast cell activation and the release of IL-6 without stimulating the release of pre-formed or newly formed mediators. Additionally, when the cells were activated by ArtinM protein tyrosine phosphorylation was stimulated. The low concentration of ArtinM also activated the transcription factor NFkB, but not NFAT. ArtinM also affected the cell cycle and stimulated cell proliferation. Therefore, ArtinM may have therapeutic applications by modulating immune responses due to its ability to activate mast cells and promote the release of newly synthesized mediators. Additionally, ArtinM could have beneficial effects at low concentrations without degranulating mast cells and inducing allergic reactions.

Acetonic Fraction of Bidens pilosa Enriched for Maturase K Is Able to Control Cerebral Parasite Burden in Mice Experimentally Infected With Toxoplasma gondii

Toxoplasma gondii infection can cause abortions or congenital infection for a vast number of domestic animals and humans, leading to economic loss in veterinary sciences, as well as severe consequences for immunocompromised patients. Bidens pilosa Linné has been used in ethnopharmacology for treatment of diseases, as malaria, diabetes and hepatitis, in addition to its use as antioxidant, antiallergic, anti-inflammatory, and antiviral. The components of this plant have never been studied before for treatment of toxoplasmosis, and the conventional drugs currently used to treat this disease have high degree of toxicity. Thus, the aim of this study was to evaluate the effect of B. pilosa against T. gondii, by analyzing a total extract of this plant in parallel with a fraction obtained by precipitation in acetone. Also, it was assessed if the acetonic fraction could present lectinic activity, followed by its identification by mass spectrometry. It was observed with the experimental models designed that both total extract and acetonic fraction of B. pilosa were able to control T. gondii infection by in vitro and in vivo experiments, in addition to their low toxicity to host cells. Both total extract and acetonic fraction of this plant display capacity to impair replication of T. gondii tachyzoites. Interesting, the B. pilosa acetonic fraction treatment for 10 days after infection decreases significantly the number of T. gondii brain cyst in comparison with controls. The protein isolated from B. pilosa acetonic fraction was characterized as a novel lectin identified as maturase K. Taken together, these findings open new perspectives to treat patients infected by T. gondii. Future studies will be necessary to investigate the precise mechanism underlying the control of T. gondii infection to impair the replication of this parasite in the host cells after treatment with B. pilosa maturase K.

Promising Plant-Derived Adjuvants in the Development of Coccidial Vaccines

Coccidial parasites cause medical and veterinary diseases worldwide, frequently leading to severe illness and important economic losses. At present, drugs, chemotherapeutics and prophylactic vaccines are still missing for most of the coccidial infections. Moreover, the development and administration of drugs and chemotherapeutics against these diseases would not be adequate in livestock, since they may generate unacceptable residues in milk and meat that would avoid their commercialization. In this scenario, prophylactic vaccines emerge as the most suitable approach. Subunit vaccines have proven to be biologically safe and economically viable, allowing researchers to choose among the best antigens against each pathogen. However, they are generally poorly immunogenic and require the addition of adjuvant compounds to the vaccine formulation. During the last decades, research involving plant immunomodulatory compounds has become an important field of study based on their potential pharmaceutical applications. Some plant molecules such as saponins, polysaccharides, lectins and heat shock proteins are being explored as candidates for adjuvant/carriers formulations. Moreover, plant-derived immune stimulatory compounds open the possibility to attain the main goal in adjuvant research: a safe and non-toxic adjuvant capable of strongly boosting and directing immune responses that could be incorporated into different vaccine formulations, including mucosal vaccines. Here, we review the immunomodulatory properties of several plant molecules and discuss their application and future perspective as adjuvants in the development of vaccines against coccidial infections.

Lectins as Promising Therapeutics for the Prevention and Treatment of HIV and Other Potential Coinfections

Human immunodeficiency virus-acquired immunodeficiency syndrome (HIV/AIDS) remains a global health problem. Current therapeutics specifically target the viral pathogen at various stages of its life cycle, although complex interactions between HIV and other pathogenic organisms are evident. Targeting HIV and concomitant infectious pathogens simultaneously, both by therapeutic regimens and in prevention strategies, would help contain the AIDS pandemic. Lectins, a ubiquitous group of proteins that specifically bind glycosylated molecules, are interesting compounds that could be used for this purpose, with demonstrated anti-HIV properties. In addition, potential coinfecting pathogens, including other enveloped viruses, bacteria, yeasts and fungi, and protozoa, display sugar-coated macromolecules on their surfaces, making them potential targets of lectins. This review summarizes the currently available findings suggesting that lectins should be further developed to simultaneously fight the AIDS pandemic and concomitant infections in HIV infected individuals.

Targeting the Immune System with Plant Lectins to Combat Microbial Infections

The arsenal of drugs available to treat infections caused by eukaryotic and prokaryotic microbes has been declining exponentially due to antimicrobial resistance phenomenon, leading to an urgent need to develop new therapeutic strategies. Host-directed immunotherapy has been reported as an attractive option to treat microbial infections. It consists in the improvement of host defenses by increasing the expression of inflammatory mediators and/or controlling of inflammation-induced tissue injury. Although the in vitro antimicrobial and immunomodulatory activities of lectins have been extensively demonstrated, few studies have evaluated their in vivo effects on experimental models of infections. This review aims to highlight the experimental use of immunomodulatory plant lectins to improve the host immune response against microbial infections. Lectins have been used in vivo both prophylactically and therapeutically resulting in the increased survival of mice under microbial challenge. Other studies successfully demonstrated that lectins could be used in combination with parasite antigens in order to induce a more efficient immunization. Therefore, these plant lectins represent new candidates for management of microbial infections. Furthermore, immunotherapeutic studies have improved our knowledge about the mechanisms involved in host–pathogen interactions, and may also help in the discovery of new drug targets.

Treatment with pCramoll Alone and in Combination with Fluconazole Provides Therapeutic Benefits in C. gattii Infected Mice

Cryptococcus gattii is one of the main causative agents of cryptococcosis in immunocompetent individuals. Treatment of the infection is based on the use of antimycotics, however, the toxicity of these drugs and the increase of drug-resistant strains have driven the search for more effective and less toxic therapies for cryptococcosis. pCramoll are isolectins purified from seeds of Cratylia mollis, a native forage plant from Brazil, which has become a versatile tool for biomedical application. We evaluated the effect of pCramoll alone and in combination with fluconazole for the treatment of mice infected with C. gatti. pCramoll alone or in combination with fluconazole increased the survival, reduced the morbidity and improved mice behavior i.e., neuropsychiatric state, motor behavior, autonomic function, muscle tone and strength and reflex/sensory function. These results were associated with (i) decreased pulmonary and cerebral fungal burden and (ii) increased inflammatory infiltrate and modulatory of IFNγ, IL-6, IL-10, and IL-17A cytokines in mice treated with pCramoll. Indeed, bone marrow-derived macrophages pulsed with pCramoll had increased ability to engulf C. gattii, with an enhanced production of reactive oxygen species and decrease of intracellular fungal proliferation. These findings point toward the use of pCramoll in combination with fluconazole as a viable, alternative therapy for cryptococcosis management.