Corrigendum: Two small-molecule inhibitors of Toxoplasma gondii proliferation in vitro.

[This corrects the article DOI: 10.3389/fcimb.2023.1145824.].

Two small-molecule inhibitors of Toxoplasma gondii proliferation in vitro.

Background: Toxoplasmosis caused by Toxoplasma gondii is a globally distributed zoonosis. Most infections appear asymptomatic in immunocompetent individuals, but toxoplasmosis can be fatal in fetuses and immunocompromised adults. There is an urgent need to research and develop effective and low-toxicity anti-T. gondii drugs because of some defects in current clinical anti-T. gondii drugs, such as limited efficacy, serious side effects and drug resistance. Methods: In this study, 152 autophagy related compounds were evaluated as anti-T. gondii drugs. The activity of ß-galactosidase assay based on luminescence was used to determine the inhibitory effect on parasite growth. At the same time, MTS assay was used to further detect the effects of compounds with over 60% inhibition rate on host cell viability. The invasion, intracellular proliferation, egress and gliding abilities of T. gondii were tested to assess the inhibitory effect of the chosen drugs on the distinct steps of the T. gondii lysis cycle. Results: The results showed that a total of 38 compounds inhibited parasite growth by more than 60%. After excluding the compounds affecting host cell activity, CGI-1746 and JH-II-127 were considered for drug reuse and further characterized. Both CGI-1746 and JH-II-127 inhibited tachyzoite growth by 60%, with IC50 values of 14.58 ± 1.52 and 5.88 ± 0.23 µM, respectively. TD50 values were 154.20 ± 20.15 and 76.39 ± 14.32 µM, respectively. Further research found that these two compounds significantly inhibited the intracellular proliferation of tachyzoites. Summarize the results, we demonstrated that CGI-1746 inhibited the invasion, egress and especially the gliding abilities of parasites, which is essential for the successful invasion of host cells, while JH-II-127 did not affect the invasion and gliding ability, but seriously damaged the morphology of mitochondria which may be related to the damage of mitochondrial electron transport chain. Discussion: Taken together, these findings suggest that both CGI-1746 and JH-II-127 could be potentially repurposed as anti-T. gondii drugs, lays the groundwork for future therapeutic strategies.

[Preparation and identification of polyclonal antibody against small peptides of beta-tubulin of Toxoplasma gondii].

The amino acid sequences of beta-tubulin from Toxoplasma gondii stains (GT1 and ME49) and human were aligned by ClustalW2 software. Based on the alignment result, the C-terminal peptides of beta-tubulin of T. gondii were artificially synthesized. Rabbits were immunized with 0.5 mg synthesized peptides for five times at 2-week intervals. Serum samples were collected at the second week after the final immunization, and were analyzed for specific antibodies by ELISA. Finally, the specific-beta-tubulin polyclonal antibody was evaluated by Western blotting with the total protein of RH strain, ME49 strain, and PRU strain of T. gondii, respectively. The results showed that beta-tubulin of T. gondii stains (GT1 and ME49) shared 100% amino-acid sequence identity, and there was 98% amino acid homology between T. gondii and human. The main variable region was the C-terminus. After the fifth immunization, the titers of polyclonal antibody reached 1 : 52,800. Western blotting result indicated that the specific-beta-tubulin polyclonal antibody reacted with beta-tubulin in all the three strains (RH, ME49, and PRU), respectively.

[Preparation and antigenicity analysis of recombinant aegyptin-like protein of Aedes albopictus].

OBJECTIVE: To clone and express the aegyptin-like protein (alALP) encoding gene from Aedes albopictus salivary gland, and analyze its antigenicity. METHODS: The homology, secondary structure and antigen peptides of alALP and aegyptin protein (GenBank No. ABF18122.1) was analyzed by bioinformatics software tools. Total RNA was extracted from Ae. albopictus salivary gland. The coding region of alALP (GenBank No. AY826121) was amplified by PCR. RT-PCR product was digested with restriction enzyme and ligated into a pGEX-6P-1 vector. The recombinant pGEX-6P-1-alALP plasmid was transformed into E. coli BL21 and induced by IPTG. The recombinant soluble GST-alALP fusion protein was purified with Glutathione Sepharose 4B. The expression product was analyzed by SDS-PAGE and Western blotting. Mice were immunized each with 60 microg purified GST-alALP at every 2 weeks for 3 times, and mouse anti-GST-alALP serum was prepared. Western blotting assay with mice anti-GST-alALP serum and serum of mice exposed to Ae. albopictus bites was used to analyze its antigenicity. RESULTS: Bioinformatics prediction results showed that alALP and aegyptin had 65.58% homology with a similar secondary structure, and a conservative polypeptide. The product of RT-PCR was 762 bp. The recombinant plasmid pGEX-6P-1-alALP was confirmed by double restriction enzyme digestion, PCR and sequencing. SDS-PAGE and Western blotting analysis showed that the bacteria containing recombinant plasmid pGEX-6p-1-alALP expressed a soluble recombinant fusion protein (M(r) 56 000) after being induced with IPTG. Western blotting analysis revealed that GST-alALP protein was recognized by mouse anti-GST-alALP serum and serum of mice ex- posed to Ae. albopictus bites. CONCLUSION: Mature peptide gene of alALP can be expressed in prokaryotic expression system, and the recombinant protein shows antigenicity.

[Preparation and application of the polyclonal antibody of Toxoplasma gondii autophagy protein 8 (TgAtg8)].

OBJECTIVE: To prepare and evaluate specific-TgAtg8 polyclonal antibody. METHODS: The known Saccharomyces cerevisiae Atg protein sequences were used to identify Toxoplasma gondii homologous protein through bioinformatics analysis. TgAtg8 cDNA was amplified and cloned into prokaryotic expression vector pGEX-6p-1. The constructed pGEX-6p-1-TgAtg8 was transformed into E. coli BL21 cells and induced with IPTG for expression. The expression product was analyzed through SDS-PAGE and Western blotting. The recombinant TgAtg8 protein with an N-terminal glutathione-S transferase tag was used to immunize rabbits and raise specific polyclonal antibody against TgAtg8. Subsequently, the antibody was applied for Western blotting and IFA assay. RESULTS: Recombinant expression plasmid of pGEX-6p-1-TgAtg8 was confirmed correct by restriction enzyme digestion and sequencing. SDS-PAGE and Western blotting analysis showed that the recombinant TgAtg8 protein with the predicted molecular weight (M(r)40000) was expressed highly in E. coli BL21. After immunization, the specific antibodies against TgAtg8 protein were produced. The anti-TgAtg8 polyclonal antibody reacted specifically with TgAtg8 fusion protein or endogenous TgAtg8. Importantly, IFA assay determined that the TgAtg8 signal was generally distributed throughout the cytoplasm of the tachyzoites. However, the green fluorescence signal gathered into one or more green spots after induction of autophagy. CONCLUSION: The specific polyclonal antibody against TgAtg8 could be used to observe the dynamics of autophagosome formation in T. gondii, which is useful tool to investigate the autophagic machinery in this parasite.

[Cloning and expression of Toxoplasma gondii autophagy-related protein 3 gene and preparation of its polyclonal antibody].

OBJECTIVE: To clone and express autophagy-related protein 3 (TgAtg3) gene of Toxoplasma gondii, and obtain the specific polyclonal antibody against TgAtg3. METHODS: TgAtg3 cDNA was inserted into prokaryotic expression vector pET28a. After identification, the constructed plasmid pET28a-TgAtg3 was transformed into E. coli Rosetta cells, and induced by special induction medium for expression of the protein. The recombinant protein was purified via Ni-NTA affinity chromatography. Western blotting assay was performed with anti-His tag mouse monoclonal antibody as the primary antibody. Rabbits were immunized with 125 µg purified TgAtg recombinant protein. Each rabbit received 4 immunizations at 2-week intervals with the same dose of antigen. The specific anti-TgAtg3 polyclonal antibody was obtained, and analyzed by Western blotting and indirect immunofluorescence assay (IFA). RESULTS: pET28a-TgAtg3 plasmid was identified by restriction enzyme digestion, PCR amplification and sequencing. SDS-PAGE and Western blotting analysis showed that the recombinant TgAtg3 protein (about Mr 44,000) was expressed in E. coli Rosetta cells. TgAtg3 protein from tachyzoite lysates was recognized by the specific anti-TgAtg3 polyclonal antibody. IFA assay determined that the specific polyclonal antibody bound to TgAtg3 protein from the cytoplasm of tachyzoites. CONCLUSION: The obtained soluble polyclonal antibody against TgAtg3 can specifically react to the endogenous TgAtg3 protein.

Development-specific differences in the proteomics of Angiostrongylus cantonensis.

Angiostrongyliasis is an emerging communicable disease. Several different hosts are required to complete the life cycle of Angiostrongylus cantonensis. However, we lack a complete understanding of variability of proteins across different developmental stages and their contribution to parasite survival and progression. In this study, we extracted soluble proteins from various stages of the A. cantonensis life cycle [female adults, male adults, the fifth-stage female larvae (FL5), the fifth-stage male larvae (ML5) and third-stage larvae (L3)], separated those proteins using two-dimensional difference gel electrophoresis (2D-DIGE) at pH 4-7, and analyzed the gel images using DeCyder 7.0 software. This proteomic analysis produced a total of 183 different dominant protein spots. Thirty-seven protein spots were found to have high confidence scores (>95%) by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Comparative proteomic analyses revealed that 29 spots represented cytoskeleton-associated proteins and functional proteins. Eight spots were unnamed proteins. Twelve protein spots that were matched to the EST of different-stage larvae of A. cantonensis were identified. Two genes and the internal control 18s were chosen for quantitative real-time PCR (qPCR) and the qPCR results were consistent with those of the DIGE studies. These findings will provide a new basis for understanding the characteristics of growth and development of A. cantonensis and the host-parasite relationship. They may also assist searches for candidate proteins suitable for use in diagnostic assays and as drug targets for the control of eosinophilic meningitis caused by A. cantonensis.

[A diffusion tensor magnetic resonance imaging study of age-related cerebral white matter diffusion anisotropy in normal human adult].

OBJECTIVE: To investigate the correlation between cerebral white matter fraction anisotropy (FA) in normal human adults using the diffusion tensor magnetic resonance (MR) imaging (DTI). METHODS: Forty-five adults with normal cerebral white matter MRI findings in 3 age groups (n=15), namely 25 approximately 35 years (young), 45 approximately 55 years (middle-aged) and 65 years or above (elderly), underwent conventional MRI and diffusion tensor MR imaging. FA was measured in different regions of interest (ROIs) including the genu and splenium of the corpus callosum, posterior limb and anterior limb of the internal capsule, centrum semiovale, frontal white matter, thalamus and head of the caudate nucleus. RESULTS: The FA values of the corresponding regions were similar between the left and right hemispheres. The FA value in the genu of the corpus callosum, centrum semiovale and the frontal white matter decreased with age, showing significant differences between the 3 age groups (P<0.05). The FA value in the splenium of the corpus callosum decreased significantly with age, with significant differences between the elderly and young groups and between the elderly and middle-aged groups (P<0.05). The values in the posterior limb and anterior limb of the internal capsule also decreased significantly with age as shown by comparison between the elderly and young groups (P<0.05). No significant difference was found in the FA value of the thalamus and head of the caudate nucleus between the three groups (P>0.05). CONCLUSION: The FA values decrease with age, especially in the genu of corpus callosum, centrum semiovale and frontal white matter. The patient's age and age-related white matter degradation must be considered in DTI-based diagnosis of cerebral diseases.