AB0013 HLA ASSOCIATION WITH SYSTEMIC SCLEROSIS (SSc) IN NORTH INDIAN POPULATION AND FAMILIAL INHERITANCE PATTERNS
Authors: S. Machhua, R. Minz, S. K. Sharma, H. Singh, Y. Kumar, S. Anand, S. Handa, S. Singh
Journal: Annals of the Rheumatic Diseases (2020)

Background: It is widely believed that SSc develops in an individual with a permissive genetic makeup.Genetic influences have long been suspected to impact SSc. In families with a history of SSc, the incidence of disease can range from 1.5 to 1.7% (1). There are several reports of familial occurrence and certain alleles of the HLA system have been associated with the disease (2).No Indian data pertaining to genetic basis of systemic sclerosis is present. Understanding the genetic basis of the disease will help us in defining the biomarkers of the disease in the population that can help in early diagnosis and prognosis. Objectives: To study HLA association with Systemic sclerosis (SSc) in North Indian Population and its genetic susceptibility to familial systemic sclerosis. Methods: A total of 150 SSc patients diagnosed by following ACR and EULAR criteria and 150 control subjects, were genotyped for HLA-A, B, DRB1, DQB1 loci by Luminex® 200 Instrument (USA). The association of alleles with disease susceptibility was tested by Chi-square test and Fisher’s exact test. HLA Typing for HLA class I (A, B, C) and II(DR,DQ,DP) for familial study of systemic sclerosis in 2 families was performed by Next Generation Sequencing(NGS) with illumina MiniSeq using MIA FORA NGS Kits from IMMUCOR. Antinuclear patterns (ANA) and specific antibodies were detected by indirect Immunofluorescence and Immunoblot (Euroline, Germany). Results: Strong disease associations were observed for haplotypes A*24(OR=1.7;&lt; 0.02), A*32(OR=2.8;&lt; 0.02), B*35(OR=1.7;&lt; 0.03), DRB1*11(OR=2.1;&lt; 0.007). The reduced frequencies of haplotypes A*68(P&lt; 0.05), DRB1*10(P&lt; 0.05), DRB1*12 (P&lt;0.00) among patients suggested a protective association. There was no statistical association found with HLA DQB*1. Through NGS we observed that in the 1 st family haplotypes HLA –A*11, 32, 24; B* 51, 55, 35; C*-14, 04; DRB1*15, 04; DQB1*05, 03; DPB1*04, 26 appears in affected family members with serological abnormalities.In the 2 nd family both mother and daughter had same set of haplotypes except DQB1 with serological abnormalities. The haplotypes DPB1*04 was present in all the diseased individuals of both the families (Fig. 1 and table 1). Table 1. NGS HLA typing report A B C DRB1 DQB1 DPB1 F1 11 24 35 15 04 04 15 15 05 05 02 26 F2 11 32 51 55 14 04 15 04 05 03 04 04 F3 11 24 35 55 04 04 15 15 05 05 26 04 F4 32 11 51 15 14 04 15 04 05 03 02 04 F5 24 33 35 44 04 07 15 07 05 02 26 14 F6 11 24 35 55 04 04 15 15 05 05 04 26 F7 11 24 35 55 04 04 15 15 05 05 04 26 F8 24 32 51 35 14 04 04 15 03 05 26 04 F9 11 32 51 55 14 04 15 04 05 03 04 04 F10 11 33 44 52 07 12 11 07 02 03 04 13 F11 11 33 44 52 07 12 11 07 03 03 04 13 Fig. 1 Conclusion: The risk alleles A*24, 32; B*35; DRB1*11 were found to be associated with North Indian cohort of SSc, while the protecting alleles were A*68; DRB1*10, 12.These risk alleles were present in the SSc affected family members and the protective alleles were absent in the same. Surprisingly, even healthy members carried the same risk alleles but did not manifest the disease or have serological evidence of the same. We have not excluded occurrence of disease at a later age, as presently the healthy siblings are young. Thus our study indicates that though HLA association are found with SSc but many other factors like HLA (HLA *C, DPB1*) or non HLA genes as wells as epigenetic factors might also play a role in disease manifestation and severity. References: [1]Luo Y, Wang Y, Wang Q, et al . Systemic sclerosis: genetics and epigenetics. J Autoimmun.2013; 41:161–67. [2]de Juan MD 1 , Belzunegui J, Belmonte I, Barado J, Figueroa M, Cancio J, Vidal S, Cuadrado E. An immunogenetic study of familial scleroderma. Ann Rheum Dis. 1994 Sep; 53(9):614-7. Acknowledgments: The technical help of Mr.Manoj Kumar and Mr.Vinkesh are hereby gratefully acknowledged Indian Council of Medical Research(Funding of Fellowship) Disclosure of Interests: None declared