Proteaese activity of Blastocystis hominis subtype3 in symptomatic and asymptomatic patients

Abstract

Despite accumulating evidence indicating that Blastocystis hominis is pathogenic and that cysteine proteases are involved in its pathogenesis, few researches discussed the protease activity of B. hominis genetic subtypes. Therefore, the present study aims to identify the underlying pathogenic role of the proteases of B. hominis subtype 3 at different molecular weights in correlation to gastrointestinal symptoms. Of 65 patients with various clinical presentations referred to our laboratory for stool examination, 26 (40%) were B. hominis positive by stool culture. Of 26 (group I) B. hominis patients, 18 (69.2%) were symptomatic (group IA) and 8(30.8%) were asymptomatic (group IB). Of 25 normal control group (group II), 5 (20%) were B. hominis positive. Subtype 3 was the only genotype recovered by polymerase chain reaction. Of 26 patients in group I, 19 (73.1%) were immunocompetent and 7 (26.9%) were immunocompromised. Protease activities of B. hominis subtype 3 were recognized at 32-kDa (46.2%), 39-kDa (7.7%), 120-kDa (38.5%), 140-kDa (11.5%), and 215-kDa (19.2%) bands in gelatin sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Proteases were recognized in 17 (94.4%) out of 18 symptomatic Blastocystis patients versus 2 (25.0%) out of 8 asymptomatic patients. Proteases at 32 kDa were reported in 61.1% of symptomatic versus 12.5% of asymptomatic patients. It was concluded that proteases of B. hominis genetic subtype 3, particularly those at 32 kDa, could be considered a virulence factor that is responsible for protein degradation and have a possible pathogenic role in host immune evasion.

Prevalence and Genotype Analysis of Blastocystis hominis in Iran: A Systematic Review and Meta-Analysis

“…There has been less attention to B. hominis in the diagnostic and training field in Iran and clinicians do not believe in pathogenicity and its treatment that may play a role in increasing its prevalence. Result of only three genomic studies that were performed in Iran (36,60,64) are similar to many studies performed in other regions of the world that have reported ST3 as the most common subtype of B. hominis in the world (7% -92%) (78,79). Some researchers have attributed ST3 to urticaria, HIV and cancer (80).…”

“…Although, the second and third subtypes were ST1 and ST5, they have not been reported in all studies in Iran. Furthermore, ST1 is known as a pathogenic subtype in patients with gastrointestinal symptoms (20,78,79). Mostly, ST5 has been found in cattle and pigs (2) and it has been reported in some regions such as Sweden (82).…”

Blastocystis Hominis Infection Pathogenic or Commensal: Short Review

“…31,32 The most studied morphological form is amoeboid in pathogenic members. 33,34 Subtype alone does not explain the pathogenicity. Hydrolytic enzymes and proteases secreted by Blastocystis lead to secretion of interleukin-8 by activating the gut mucosa, responsible for gastrointestinal symptoms.…”

Blastocystis Hominis: a Mysterious and Commonly Disregarded Parasite

“…These are asymptomatic individualsthere are many more asymptomatic cases than those with symptomatic B. hominis infection [27,30,41,56,64].…”

“…One study has proposed that 32kDa proteases of ST3 could be the virulent factors responsible for protein degradation, while another study has found that a B. hominis 29 kDa antigen could be used as a pathogenicity marker, enabling differentiation of symptomatic from asymptomatic B. hominis infections [39,40]. Increased IgA levels have been described in symptomatic individuals with B. hominis infection, compared to healthy asymptomatic carriers of B. hominis [41].…”