Interaction between antibiotic use and MS4A2 gene polymorphism on childhood eczema: a prospective birth cohort study

A birth cohort study was carried out at two large tertiary hospitals in Shanghai from 2012 to 2015. One thousand fifty-six women who had a singleton pregnancy and planned to live in Shanghai for at least 2 years were recruited. Trained research nurses conducted face-to-face interviews to collect parental information on atopy, education levels and family income. Newborn’s birth information from hospital records along with umbilical cord blood were collected at birth by research nurses. Then the children were followed up for 2 years and their medical history of eczema and epidemiologic information were collected by questionnaire. Five hundred ninety-seven Chinese Han children who completed the 2 years of follow-up were included in this study. Written informed consent was obtained from parents and / or legal guardians for all the subjects who are under 16. This study was approved by the Ethics Committees of the two participating hospitals, Xinhua Hospital and the International Peace Maternity & Child Health Hospital, and conducted according to the principles in the Declaration of Helsinki.

Each study subject was followed up at 6 months, 1 year and 2 years of age. At six-month follow-up, an internet-based questionnaire survey was conducted to collect children’s history of eczema via the standardized International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire, which had been validated and adapted in China [14, 15]. Information on antibiotic use and environmental exposures, including home pet sitting, secondhand smoke exposure and home decoration was also collected. At one-year and two-year follow-up visits, face-to-face questionnaire interviews were conducted to collect similar information as that at six-month follow-up.

The diagnostic criteria for eczema were: itchy rash on the flexural sites (the folds of the elbows, behind the knees or in front of the ankles), face, or around the neck or ears, and itchy rash coming and going for at least 6 months, based on the UK working party’s diagnostic criteria [16]. Two dermatologists diagnosed eczema independently for all the subjects based on the questionnaires, with disagreements resolved by consensus.

This study focused on four candidate genes, including IL13, IL4, MS4A2 and IL4RA, which are key inflammatory genes associated with IgE levels [7‐12]. Within these genes, six known functional single-nucleotide polymorphisms (SNPs) with minor allele frequency greater than 10% based on Chinese population [17] were chosen for analysis, as shown in Table 1.

Genomic DNA was obtained from umbilical cord blood with the QIAamp DNA Blood Mini Kit (Qiagen, Hilden, Germany). SNP genotyping was performed using matrix-assisted laser desorption / ionization time of flight mass spectrometry (MALDI-TOF MS) [18] (MassArray iPLEX; Sequenom, San Diego, CA, USA). Genotyping call rate for each SNP exceeded 99%. 5% of the samples were blindly retested and concordance rate for duplicate genotyping was greater than 98%.

Associations of epidemiologic factors with eczema were assessed by multivariate logistic regression adjusting for potential confounders. Each SNP was tested for Hardy–Weinberg equilibrium in the study subjects with the χ² test, and associations of the SNPs with eczema were also evaluated using multivariate logistic regression. Gene - environment interaction on eczema was examined by χ² tests. A two-tailed P value of 0.05 or less was considered statistically significant. All analyses were performed using SPSS version 17.0 (IBM Corp., Armonk, NY, USA).

Among the 597 children, 168 were diagnosed with eczema after 2 years of follow-up while the others were not. Characteristics of the study subjects were presented in Table 2. Antibiotic use was found significantly associated with development of childhood eczema after adjusting for multiple child and parental characteristics (P = 3.75E-4, odds ratio (OR) = 2.02). However, baby’s gender, gestational age, birth weight, delivery mode, parity, home pet sitting, in-home secondhand smoke exposure, home decoration, family income, parental atopy and education level were not found associated with eczema by multivariate logistic regression (P > 0.05).

All the SNPs met Hardy-Weinberg equilibrium criteria (p > 0.05). The genetic models (additive, dominant and recessive models) were tested for the SNPs. Among the six SNPs, only MS4A2 rs569108 was found associated with childhood eczema (P < 0.05), and its most significant association with the disease was under additive model. Association test results under additive model were shown in Table 3. MS4A2 rs569108 GG genotype was found significantly associated with eczema (P = 1.68E-02, OR = 4.66). No significant associations were found between the other five SNPs and eczema (P > 0.05).

Table 4 shows that children with both antibiotic use and MS4A2 rs569108 GG genotype were more likely to develop eczema than those without antibiotic use and GG homozygote (P = 1.49E-02, OR = 6.24), and also more likely to develop eczema than those with only antibiotic use or GG genotype (OR = 6.24 VS. 2.04 or 4.68).