The Study of the Cytopathic Effects of Blastocystis sp., ST1-3 and 6 Isolated from Subjects Referred to Medical Laboratories in HT29 Cell Line

Blastocystis sp., is one of the most common intestinal protozoan parasites found in both human and animal fecal samples. The pathogenicity and cytopathic effects of subtypes ST1-3 and 6 of Blastocystis sp., on gastrointestinal cell line are unclear. This study aimed to investigate the impacts of intra- subtype variations on the apoptosis and cytopathic effects on the HT-29 cell line in 2019 at the Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

This study was an experimental investigation of Blastocystis sp., subtypes 1-3 and 6, which were isolated from stool samples of 30 symptomatic and subtypes 1-3 from 25 asymptomatic subjects. After purifying and counting the microorganisms, lysate of Blastocystis sp., was prepared from 1 × 105 of the microorganism by three freeze- thaw cycles in liquid nitrogen and a 37°C water bath. Then, the lysates of subtypes of Blastocystis were co-incubated with the HT-29 cell line for 48h. Finally, the cell proliferation rate was measured using an MTT dye assay. For measuring the statistical differences in the cell proliferation based on subtypes as well as symptoms, One- way ANOVA test incorporated with GraphPad Prism was applied.

The results clearly indicated that all Blastocystis sp., subtypes, compared to non-treated control (NTC), had a cytopathic/inhibitory effect on HT-29 cells growth. The lowest cytopathic effect was seen in ST1 isolated from symptomatic patients (17.11%), while the highest was seen in ST1 isolated from asymptomatic patients (25%). Indeed, ST2 showed milder cytopathic effects in the HT-29 cell line compared to ST1, 3, and 6. However, there was no statistical correlation between subtypes as well as symptoms and cytopathic effect.

Although there was no statistically significant correlation between subtypes and the cytopathic effect, immunologic responses of hosts seem to play a critical role against Blastocystis sp. Our findings showed milder effects of Blastocystis sp., ST2 compared to the other subtypes; however, intra-subtype variations in the pathogenicity of the protist remain unclear, and further investigations are needed.