Frequency of Genotypes and Allelic Polymorphisms of Vitamin D Receptor in Egyptian Psoriatic Patients and Their Association With Disease Severity, Immune Modulation of IL-22 Levels and The Response to Topical Calcipotriol Treatment

Abstract

Objective: This study was performed to determine the genotype and allelic frequencies (polymorphisms) of the four genes of vitamin D receptor (VDR) among Egyptian psoriatic patients and healthy controls to explore their association with disease severity (PASI) score and immune modulation of IL-22 cytokine and to predict the response to topical calcipotriol treatment. Patients and Methods: The frequencies of the four VDR gene polymorphisms (FokI, ApaI, TaqI, and BsmI) in blood samples of 51 adult Egyptian patients with psoriasis vulgaris and 50 healthy controls were evaluated using restriction fragment length polymorphism (RFLP)-PCR. Serum levels of IL-22 were measured by ELISA. Results: The most frequent genotype (wild) in the studied patients was Apa1; AA (88.2%) followed by Fok1; FF (47.1%) and Taq1; TT (47%), while Bsm1; BB genotype was (27.7%). The most frequent allele polymorphisms either in one allele (Bb) or both alleles (bb) in psoriatic patients were 72.5%, followed by Ff, ff (52.9%) and Tt, tt (52.9%). The less frequent allelic polymorphism was Aa, aa (27.7%). Insignificant differences in the frequency of genotype (wild) and allelic polymorphisms were detected between patients and controls ( P > 0.05). A significantly higher serum concentration of IL-22 (ng/mL) was detected in patients than controls ( P = 0.001). Further, 66.6% of patients displayed a clinical response, while 33.4% were non-responders. A significantly higher expression of TaqI polymorphism was detected in (100%) of non-responders ( P < 0.001), which was also correlated with disease severity (r = 0.515, P < 0.01). Conclusion: These results suggest that the VDR TaqI polymorphism is the only gene correlated to psoriasis susceptibility in the Egyptian population, and affects the response to topical calcipotriol treatment but does not affect IL-22 immune modulation.