Does 24bp Duplication of Human CHIT1 Gene (Chitotriosidase1) Predispose to Filarial Chyluria? A Case-Control Study

Duplication mutation in CHIT1 gene is associated with poor response to medical therapy in patients affected with filarial chyluria

We explore the impact of CHIT1 gene mutation on clinical, biochemical parameters and response to outcome (remission/failure) of medical treatment in North Indian filarial chyluria (FC) patients. Data of 101 subjects of FC treated medically between March 2013 and April 2016 in whom CHIT1 gene polymorphism was determined were analyzed. Filarial etiology was confirmed by DEC-provocative test, immuno-chromatographic test and IgG/IgM-combo rapid antibody test. CHIT1 gene polymorphism was genotyped by polymerase chain reaction. Of 101 patients (mean age, 36.9±10.28 years; male: female, 3:1.2), 66 experienced remission (Group-A) while 35 experienced relapse or failed to respond (Group-B). A significant association was observed between CHIT1 genotypes and higher grade of disease (p= 0.001). Wild-type, heterozygous and homozygous mutant frequencies of CHIT1 genotypes were 78.6%, 72.5% and 27.8% in remission and 21.4%, 27.5% and 72.2%, in recurrence/failure, respectively. Our results showed that patients with mutant genotype (TT) of CHIT1 gene showed significantly higher rate of recurrence or failure to medical therapy than wild type (HH) genotypes [OR (95% CI) = 9.53 (1.84-49.21), p=0.011]. This preliminary study showed the impact of CHIT1 gene variants on treatment outcome in FC patients. This observation needs to be confirmed using studies with larger numbers of FC patients.

Genetic association of MBL-2 gene polymorphisms with Filarial chyluria

Lymphatic filariasis has become a significant public health issue in North India. The association of polymorphisms in MBL2 gene with filarial chyluria (FC) is evaluated in the North Indian patients for the first time. Hence, a tertiary care hospital based case-control study was conducted in north India where FC is endemic. Therefore, 186 confirmed patients of FC as cases and 210 age-, sex- and residence-matched subjects as controls were enrolled for the study. Filarial etiology was confirmed using diethylcarbamazine (DEC)-provocation test, immune chromatographic test and IgG/IgM antibody test. MBL2 gene polymorphisms at codon 54 and -221 promoter region were genotyped by PCR followed by RFLP. Wild-type, heterozygous and homozygous mutant frequencies of MBL2 genotype at the codon 54 were 57.5%, 32.8% and 9.7% in the case group and 62.9%, 30.5% and 6.7%, in controls, respectively. The same at the -221 position were 51.1%, 44.1% and 4.8% in FC patients and 44.3%, 40.0% and 15.7% in controls, respectively. Thus, results no significant association between MBL2 polymorphism at codon 54 and FC. However, polymorphism at the -221 promoter region is linked with FC with a significant odd-ratio of 0.27 (confidence interval at 95% was 0.12-0.59; p<0.001). This preliminary finding is intriguing for further confirmation using a larger study with more patients.

The Genetic Polymorphisms of 24 Base Pair Duplication and Point G102S of Human Chitotriosidase to Bancroftian Filariasis at the Thai⁻Myanmar Border

Lymphatic filariasis, caused by lymphatic filarial parasites, Wuchereria bancrofti, and Brugia malayi, causes significant morbidity and disability to 120 million people in the tropics and subtropics. Chitin has an important role for embryogenesis in adult worms and is a component of microfilaria sheath. Human chitotriosidase (CHIT1) is a chitin-degrading enzyme which provides a protective role against chitin-containing pathogens. Here, we determined the association of CHIT1 polymorphisms with susceptibility to bancroftian filariasis (BF) in 88 individuals at the Thai–Myanmar border. Two common polymorphisms of CHIT1, contributing inactive CHIT protein, including 24 base pair (24 bp) duplication in exon 10, and p. G102S in exon 4 were genotyped by allele-specific Polymerase Chain Reaction (PCR) and PCR sequencing, respectively. Unexpectedly, genotype frequencies of 24 bp duplication insertion homozygous (INS/INS) were significantly higher in endemic normal (EN) (40.0%) than BF patients (31.4%). In contrast, genotype frequencies of p. G102S homozygous (A/A) in BF patients (21.6%) was higher than in EN (19.0%) without statistical difference. Mutant allele frequencies of 24 bp duplication were 0.6125 (98/160) and p. G102S were 0.392 (69/176). Genotype and allele frequencies of CHIT1, 24 bp duplication, and p. G102S, showed no association with BF patients.