Assessment of tissue levels of miR-146a and proinflammatory cytokines in experimental cerebral toxoplasmosis following atovaquone and clindamycin treatment: An in vivo study

BACKGROUND

Despite recent advances for treating cerebral toxoplasmosis (CT), monitoring the parasite burden and treatment response is still challenging. miRNAs are small non-coding RNAs with regulatory functions that can be used in diagnosis and treatment monitoring. We investigated the changes in miR-146a, BAG-1 gene, IL-6, and IL-10 tissue levels in the brain of BALB/c mice with chronic CT caused by the PRU strain of T. gondii following anti-parasitic and antibiotic treatment.

METHOD

Fifty-three 6-to 8-week-old BALB/c mice were infected using intraperitoneal inoculation of cerebral cysts of T. gondii PRU strain and then divided into five groups as follows: group 1 included mice treated with 100 mg/kg/d Atovaquone (AT), group 2 included mice treated with 400 mg/kg/d clindamycin (CL), group 3 included mice treated with combination therapy (AT + CL), group 4 included infected untreated mice as a positive control (PC), and; group 5 included uninfected untreated mice as negative control (NC). After the completion of the treatment course, tissue level of mir-146a, miR-155, BAG-1 gene, IL-6, and IL-10 was investigated with real-time polymerase chain reaction. The IL-6/IL-10 ratio was calculated as an indicator of immune response. Moreover, brain cyst numbers were counted on autopsy samples.

RESULTS

miR-146a, IL-6, IL-10, and BAG-1 genes were expressed in PC, but not in the NC group; miR-146a, IL-6, IL-10, and BAG-1 gene expression were significantly lower in AT, CL, and AT + CL compared with PC. MiR-146a and BAG-1 levels in AT and CL were not different statistically, however, they both had lower levels compared to AT + CL (P < 0.01). There was no difference in the expression of IL-6 and IL-10 between treatment groups. BAG-1 expression was significantly lower in AT, than in CL and AT + CL (P < 0.0089 and < 0.002, respectively). The PC group showed a higher ratio of IL-6/IL-10, although this increase was not statistically significant. It is noteworthy that the treatment with AT reduced this ratio; in the inter-group comparison, this ratio showed a decrease in the AT and AT + CL compared to the PC. The number of brain tissue cysts was significantly lower in AT, CL, and AT + CL, than in PC (p < 0.0001). AT had significantly lower brain cysts than CL and AT + CL (P < 0.0001).

CONCLUSION

It seems that the factors studied in the current research (microRNA and cytokines) are a suitable index for evaluating the response to antiparasitic and antibiotic treatment. However, more studies should be conducted in the future to confirm our findings.

Introduction of protocols for mass production of Toxoplasma gondii tachyzoites of the genotype II PRU strain

Background

Few investigations of genotype II of Toxoplasma gondii, the most prevalent form of the Toxoplasma parasite in humans, have been carried out on due to the rapid conversion of tachyzoites to bradyzoites in its life cycle. The current study aimed to create animal and in vitro models for production of the tachyzoites of the Prugniaud (PRU) genotype II strain.

Methods

To develop an immunocompromised model and obtain tachyzoites of the PRU strain, BALB/c mice were orally treated with dexamethasone (10 mg/kg), cyclophosphamide (36 mg/kg), and cyclosporine (18 mg/kg) from 5 days prior to inoculation. Then, 10-15 tissue cysts of PRU strain were inoculated intraperitoneally into the mice. The tachyzoites obtained from mice were then cultivated in a HeLa cell culture. The resulting yield of tachyzoites was cryopreserved in 92% fetal calf serum, 8% dimethyl sulfoxide. The infectivity of these tachyzoites was evaluated using in vivo and in vitro examinations.

Results

Numerous tachyzoites were observed in the peritoneal fluid of the immunosuppressed mice within 10-15 days after inoculation, and many tachyzoites were harvested from the HeLa cell culture. Trypan Blue staining showed 80% viability of the tachyzoites recovered from cryopreservation and this was confirmed by HeLa cell culture. In addition, mice infected intraperitoneally with the recovered tachyzoites presented with cysts in the brain after 2 months.

Conclusion

We have developed an animal model for mass production of T. gondii tachyzoites of the PRU strain. This method can provide fresh viable tachyzoites of Toxoplasma gondii for use as and when required in future investigations.