Abstract
Blastocystis hominis is highly prevalent with respiratory allergies among Egyptian children. Yet, little is known about the possible immunological relationship. Aims of this study were to measure complement-3 (C-3), total and specific IgE to intestinal allergens in patients' serum regarding the identified B. hominis genotypes. In a cross-sectional study, three hundred children (150 asthmatics and 150 non asthmatics) participated in the study from both sexes, mean age 7.5 ± SD (3-4) years after a questionnaire administration. PCR-based genotyping of B. hominis selective in vitro cultivation was performed. C-3, total and specific IgE were all measured in patients' serum utilizing ELISA. Blastocystosis was detected in 100 out of 300 children, 65 (43.3%) out of 150 asthmatics and 35 (23.3%) out of 150 non-asthmatics. Vacuolar forms were the most prevalent in both direct wet mount and stool cultures. Forty (61.5%) out 65 asthmatics and 5 (14.2%) out of 35 non-asthmatics were ≥ 5 organisms/HPF. Sex and irritable bowel disease were statistically insignificant (p value < 0.05). Urticaria was coincided in 15.4% of asthmatics and 8.6% of non-asthmatics. Of 100 cases of blastocystosis, eighty-four were genotype-3 and sixteen were genotype-4. Out of these, 55 cases of genotype-3 and 6 cases of genotype-4 were asthmatics. Positive C-3 serum levels were in 46 (54.81%) of genotype-3 and 2 (12.5%) of genotype-4. High total IgE levels in 30 (35.7%) out of 84 cases of genotype-3 and 4 (25%) out of 16 cases of genotype-4. Positive specific IgE was in 25 (29.8%) of genotype-3 and 3 (18.75%) of genotype-4. Genotype-3 was of higher infection intensity (p value = 0.0001). In conclusion, B. hominis possess a hidden allergy triggering impact that can be obscured by simultaneous high (total and specific) IgE levels towards specific common intestinal allergens. Blastocystosis induces allergy by increasing C-3 serum levels in a genotype-dependent manner being higher in genotype-3. Virulence of genotype-3 seems to stand beyond increased parasite intensity and wide absorption of intestinal allergens that indirectly elevate IgE serum levels.