Production and characterization of monoclonal antibodies against Toxoplasma gondii ROP18 with strain-specific reactivity

TgMIC6 inhibition of autophagy is partially responsible for the phenotypic differences between Chinese 1 Toxoplasma gondii strains

Chinese1 is the predominant Toxoplasma gondii lineage in China, and significant phenotypic differences are observed within the lineage. WH3 and WH6 are two representative strains of Chinese 1, which exhibit divergent virulence and pathogenicity in mice. However, virulence determinants and their modulating mechanisms remain elusive. A global genome expression analysis of the WH3 and WH6 transcriptional profiles identified microneme secretory protein 6 (MIC6), which may be associated with the phenotypic difference observed in WH3. In the present study, the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 genome-editing technique was used to generate a T. gondii microneme secretory protein (TgMIC6) knockout in WH3. Wild-type mice and different mouse and human cell lines were infected with the WH3, WH3-Δmic6, and WH6 strains. The survival rate of mice, related cytokine levels in serum, and the proliferation of parasites were observed. These results suggested that TgMIC6 is an important effector molecule that determines the differential virulence of WH3 in vivo and in vitro. Furthermore, MIC6 may enhance WH3 virulence via inhibition of host cell autophagy and activation of key molecules in the epidermal growth factor receptor (EGFR)-Akt-mammalian target of rapamycin (mTOR) classical autophagy pathway. CD40L was cleared in vivo by i.p injection of CD40L monoclonal antibody, and it was found that the virulence of WH3-Δmic6 to mice was restored to a certain extent in the absence of CD40L. This study elucidates the virulence determinants and immune escape strategies of Toxoplasma gondii in China. Moreover, these data will aid the development of effective strategies for the prevention and control of toxoplasmosis.

Enhancing the therapeutic potential of P29 protein-targeted monoclonal antibodies in the management of alveolar echinococcosis through CDC-mediated mechanisms

Alveolar echinococcosis (AE) is a highly lethal helminth infection. Current chemotherapeutic strategies for AE primarily involve the use of benzimidazoles (BZs) such as mebendazole (MDZ) and albendazole (ABZ), which exhibit limited efficacy. In a previous study, the vaccine of recombinant Echinococcus granulosus P29 (rEgP29) showed significant immunoprotection against E. granulosus in both mice and sheep. In the current study, we utilized hybridoma technology to generate five monoclonal antibodies (mAbs) against P29, among which 4G10F4 mAb exhibited the highest antigen-specific binding capacity. This mAb was selected for further investigation of anti-AE therapy, both in vivo and in vitro. In vitro, 4G10F4 inhibited a noteworthy inhibition of E. multilocularis protoscoleces and primary cells viability through complement-dependent cytotoxicity (CDC) mechanism. In vivo, two experiments were conducted. In the first experiment, mice were intraperitoneally injected with Em protoscoleces, and subsequently treated with 4G10F4 mAb (2.5/5/10 mg/kg) at 12 weeks postinfection once per week for 8 times via tail vein injection. Mice that were treated with 4G10F4 mAb only in dosage of 5mg/kg exhibited a significant lower mean parasite burden (0.89±0.97 g) compared to isotype mAb treated control mice (2.21±1.30 g). In the second experiment, mice were infected through hepatic portal vein and treated with 4G10F4 mAb (5mg/kg) at one week after surgery once per week for 8 times. The numbers of hepatic metacestode lesions of the 4G10F4 treatment group were significantly lower in comparison to the isotype control group. Pathological analysis revealed severe disruption of the inner structure of the metacestode in both experiments, particularly affecting the germinal and laminated layers, resulting in the transformation into infertile vesicles after treatment with 4G10F4. In addition, the safety of 4G10F4 for AE treatment was confirmed through assessment of mouse weight and evaluation of liver and kidney function. This study presents antigen-specific monoclonal antibody immunotherapy as a promising therapeutic approach against E. multilocularis induced AE.

Immune system roles in pathogenesis, prognosis, control, and treatment of Toxoplasma gondii infection

Toxoplasma gondii is the protozoan causative agent of toxoplasmosis in humans and warm-blooded animals. Recent studies have illustrated that the immune system plays a pivotal role in the pathogenesis of toxoplasmosis by triggering immune cytokines like IL-12, TNF-α, and IFN-γ and immune cells like DCs, Th1, and Th17. On the other hand, some immune components can serve as prognosis markers of toxoplasmosis. In healthy people, the disease is often asymptomatic, but immunocompromised people and newborns may suffer severe symptoms and complications. Therefore, the immune prognostic markers may provide tools to measure the disease progress and help patients to avoid further complications. Immunotherapies using monoclonal antibody, cytokines, immune cells, exosomes, novel vaccines, and anti-inflammatory molecules open new horizon for toxoplasmosis treatment. In this review article, we discussed the immunopathogenesis, prognosis, and immunotherapy of Toxoplasma gondii infection.

Toxoplasma gondii induces MLTC-1 apoptosis via ERS pathway

Toxoplasma gondii (T. gondii) is a serious intracellular parasite and mammalian infection can damage the reproductive system and lead to apoptosis of Murine Leydig tumor cells (MLTC-1); however, the mechanism is unclear. The testis Leydig cell is the main testosterone synthesis cell in male mammals. We studied the mechanism of T. gondii infection on Leydig cell apoptosis in vitro. MLTC-1 were divided into control and experimental groups. Experiment group cells and tachyzoites were co-cultured, in a 1:20 ratio, for 3, 6, 9, and 12 h. T. gondii entered the cells and caused lesions at 12 h. Flow cytometry showed that the apoptosis rate of the experiment group increased with time and was significantly higher (P < 0.05) than the control group. RT-qPCR and western blot demonstrated that the expression of P53, Caspase-3, and Bax were significantly increased at 12 h (P < 0.05). Bcl-2 expression was significantly increased at 12 h (P < 0.05). The ER stress (ERS) pathway was important in cell apoptosis. RT-qPCR and western blot showed that the expression of CHOP was significantly increased at 12 h (P < 0.05). These data indicate that T. gondii induced MLTC-1 cell apoptosis may occur via the ERS pathway.

Monoclonal Antibodies for Protozoan Infections: A Future Reality or a Utopic Idea?

Following the SARS-CoV-2 pandemic, several clinical trials have been approved for the investigation of the possible use of mAbs, supporting the potential of this technology as a therapeutic approach for infectious diseases. The first monoclonal antibody (mAb), Muromonab CD3, was introduced for the prevention of kidney transplant rejection more than 30 years ago; since then more than 100 mAbs have been approved for therapeutic purposes. Nonetheless, only four mAbs are currently employed for infectious diseases: Palivizumab, for the prevention of respiratory syncytial virus (RSV) infections, Raxibacumab and Obiltoxaximab, for the prophylaxis and treatment against anthrax toxin and Bezlotoxumab, for the prevention of Clostridium difficile recurrence. Protozoan infections are often neglected diseases for which effective and safe chemotherapies are generally missing. In this context, drug resistance and drug toxicity are two crucial problems. The recent advances in bioinformatics, parasite genomics, and biochemistry methodologies are contributing to better understand parasite biology, which is essential to guide the development of new therapies. In this review, we present the efforts that are being made in the evaluation of mAbs for the prevention or treatment of leishmaniasis, Chagas disease, malaria, and toxoplasmosis. Particular emphasis will be placed on the potential strengths and weaknesses of biological treatments in the control of these protozoan diseases that are still affecting hundreds of thousands of people worldwide.