1. HLA Class II alleles and Environmental Associations with NMO in Indian Population
Pandit L, Malli C, D’Cunha A, Mustafa S, Kunder R. KS Hegde Medical Academy, Nitte University, Mangalore, Karnataka, India.
Abstract
Methods
Results
Objectives: To determine HLA- DRB1& DQB1 allele associations with NMO. Additionally the role of childhood exposure to smoking, infections, diet and sun exposure were evaluated.
Method: 93 adult patients (47.3% seropositive for NMO-IgG by CBA) with relapsing NMO/ NMOSD disorders were chosen. DRB1& DQBI allele genotyping was performed in all patients and 200 healthy controls by PCR. Environmental exposure history was obtained using a validated questionnaire.
Results: NMO patients had significant allele frequency for HLA- DRB1* (p corrected = , OR= 4.15, CI= ). The common haplotype seen was DRB1*03- DQB1*0201 (p= 0.03, OR= 1.74). Vegetarian diet (p= 0.001) and poor sun exposure (p= 0.01) in childhood were significantly associated with NMO.
Conclusions: Genetic and environmental association may be present for NMO in Indian population. Larger studies are necessary to replicate these preliminary results
HLA Class II allele genotyping: HLA- DRB1 & DQB1 genotyping was done by polymerase chain reaction with sequence specific probes . Alleles that were DRB1*1501/1502 positive by this low resolution typing technique were sequenced for accurately determining HLA- DRB1*1501 status. Results were compared with 164 MS patients. Results were analyzed using UNPHASED
Environmental exposure: A validated questionnaire was used to collect environmental exposure history in 93 patients ( mean age 33.03±12.7) and gender & age matched controls ( mean age 33.92± 11.9).
Quantity of sun exposure between patients and controls were compared using wilcoxon rank sum test (median and interquartile intervals).
Categorical variables were analyzed by chi square test. Quantity of sun exposure were further divided into quartiles of the distribution among the control population . Risk of disease was evaluated using Cox regression model.
Environmental factor
NMO cases (n=93)
NMO controls (n=186)
p value
Diet -Veg
26/93 ( 28%)
18/ (9.6 %)
0.001
Vaccination (unvaccinated)
7/93 ( 7.7%)
6/ (3.2%)
0.26
Mumps
13/87 (15.0%)
28/ (16.3%)
0.87
Chickenpox
38/87 (43.7%)
78/ (45.3%)
0.88
Measles
8/87 ( 9.2%)
4/ ( 2.3%)
0.02 TB
3/87 ( 3.4%)
0/ ( 0%)
Passive smoking
20/ 93 (21.5%)
39/ (21%)
0.98
Quantity of sun exposure (median & IQR)
( )
( )
0.01
Objectives
Results
Vegetarian diet ( 0.001) and quantity of sun exposure (0.01) were
significantly present in NMO patients when compared to controls.
2. No environmental factor evaluated in this study was associated with
risk of disease.
It is unclear whether there are genetic and environmental associations with Neuromyelitis Optica (NMO) particularly in Indian population. The objectives of this study were
Objective I: To determine HLA- DRBI & DQB1 allele frequency in 93 patients with relapsing NMO/NMOSD and 200 unrelated controls .
Objective II: To determine associations between following environmental exposures in childhood ( ≤ 18 years) with NMO
Common childhood infections in the tropics such as measles, mumps, TB, chicken pox and Herpes zoster (disorders for which colloquial terms exist ).
Vaccination history Type of Diet – Vegetarian/ Non Vegetarian
Quantity of sun exposure ( Number of hours spent outdoors X percentage body surface area exposed)
Smoking ( passive & active) ( Using a validated questionnaire in 93 patients and186 healthy matched controls).
DRB1 allele frequency in cases ( n= 93) and controls ( n= 200 )
DRB1
Allele
Case
Control
Ca-Freq
Co-Freq OR
95%Lo
95%Hi
puncorrected
*01 13 27
0.069
0.068 1
0.9658
*03 22 11
0.118
0.028
4.154
1.647
10.48
0.0001
*04 49
0.125
0.551
0.232
1.305
0.0307
*07 18 54
0.096
0.137
0.692
0.285
1.68
0.1128
*08 6 12
0.032
0.030
1.038
0.341
3.162
0.9220
*10 24
0.129
0.061
2.077
0.866
4.978
0.0086
*11 7
0.037
0.045
0.807
0.267
2.436
0.6233
*12 19 16
0.102
0.040
2.466
0.970
6.27
0.0059
*13 14 40
0.075
0.726
0.289
1.829
0.2774
*14 15 48
0.080
0.122
0.649
1.577
0.0992
15:01 44
0.086
0.112
0.755
0.323
1.765
0.2900
15:02 39
0.099
0.745
0.293
1.891
0.2814
Conclusions
HLA- DRB1*03 has shown significant association with NMO patients from different geographic regions and include European, Afro Caribbean , Brazilian and Indian populations . HLA- DRB1*15:01 is known to be the principal risk allele for MS in most populations studied worldwide including India.
Genetic susceptibility for Idiopathic demyelinating disorders may be the same across populations. Environmental influences warrant detailed study in order to further understand differences in geographic prevalence of these disorders.
Overall NMO patients had significant allele frequency for DRB1*03 which persisted for NMO IgG sero positive patients ( pcorrected = 0.03, OR= 6.75, CI= ) only.
The common haplotype seen was DRB1*03- DQB1*0201 (p= 0.03, OR= 1.74)
MS patients had modest association with DRB1*15: 01 (pcorrected = 0.02; OR= 1.54; CI= )
Acknowledgement
This study was funded by the Department of Science and Technolgy, Government of India ( SR/SO/HS/127/2010).