Novel FCN2 Variants and Haplotypes are Associated with Rheumatic Heart Disease Jaydeep A. Badarukhiya, 1 Nitin Tupperwar, 1 Sheikh Nizamuddin, 2,3 Anil Kumar Mulpur, 4 and Kumarasamy Thangaraj 1,5,i Ficolins are pattern recognition molecules that are involved in innate immune defense. Ficonin-2 (FCN2) has a specific affinity for lipoteichoic acid present in the cell wall of Streptococcus pyogenes, an etiological agent for rheumatic heart disease (RHD). We have estimated FCN2 serum levels and analyzed the functional variants of FCN2 in 400 RHD patients, 617 healthy controls, and 581 individuals belonged to various ethnic populations, who are inhabited in various geographical regions of India. Our study revealed that the FCN2 -986A and +6359T alleles were the risk factors for RHD susceptibility ( p = 0.0007 for -986G>A; p = 0.0004 for +6359C>T). The haplotype AGGT ( p = 0.0024) was observed to be a risk factor for RHD susceptibility, and the haplotype GGAC ( p = 0.002) was found to confer protection against RHD. The level of serum FCN2 was significantly higher in controls ( p < 0.0001) and in controls with GGAC haplotypes ( p < 0.0001). The frequency of the risk alleles -986A and +6359T was found to be more prevalent in Northern and North-Western (Indo-European) India. The protective GGAC haplotype was found more prevalent in Eastern (Tibeto-Burman) and South-Western (Dra- vidian) India. Alleles -986A and +6359T were in positive correlation with the prevalence of RHD (regression coefficient = 1.84 and 1.94, respectively), whereas GGAC haplotype was in negative correlation with prevalence of RHD (regression coefficient =-1.71). In conclusion, we found that low level of serum ficolin-2 is significantly associated with RHD. Further, FCN2 -986A and +6359T alleles and AGGT haplotype are associated with in- creased susceptibility to RHD, while GGAC haplotype is associated with moderate protection against RHD. Keywords: FCN2, RHD, MVR, DVR, Streptococcus Introduction S treptococcus pyogenes also known as group A strep- tococcus (GAS) are the etiological agent for rheumatic fever (RF) and its most severe consequence is rheumatic heart disease (RHD). The underlying mechanism behind the RF is the autoimmune response to GAS antigens, where sub- sets of B and T lymphocytes recognize self-antigens at different sites of the body. Throat infection caused by S. pyogenes augments an inflammatory reaction, character- ized by the secretion of several inflammatory cytokines by peripheral mononuclear cells followed by the antibody re- sponse and infiltration of B and T cells that leads to inflam- matory lesions causing damage to the valve, which finally results in RHD (Roberts et al., 2001). The RHD remains a primary health issue in developing countries, although it has been eradicated from the devel- oped countries (Gordis, 1985; Massell et al., 1988; Longo- Mbenza et al., 1998; Meira et al., 2005; Carapetis et al., 2016; Yusuf et al., 2017). RHD affects *16 million people globally and leads to the premature death of about 300,000 individuals every year (Carapetis et al., 2005b). In the year 2015, India had the highest number of RHD patients (13.17 million) with 119,100 deaths (Watkins et al., 2017). Host genetic susceptibility/resistance to RHD is one of the important factors, which requires extensive investiga- tions. Variations in the genes that encode for the molecules that are important for adaptive and innate immunity are being linked to the susceptibility to the RF and RHD (Guilherme et al., 2012). The molecules of an early innate immune re- sponse are reported to have variations in the following genes: mannose-binding lectin ( MBL2) (Reason et al., 2006), ficolin-2 (FCN2) (Messias-Reason et al., 2009), immunoglobulin gamma Fc region receptor II-a (FCGRIIA) 1 CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India. 2 Department of Urology, Medical Center-University of Freiburg, Freiburg, Germany. 3 German Cancer Consortium (DKTK) Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg, Germany. 4 Department of Cardiothoracic Surgery, Sunshine Hospitals, Hyderabad, India. 5 Centre for DNA Fingerprinting and Diagnostics, Hyderabad, India. i ORCID ID (https://orcid.org/0000-0002-0075-0106). DNA AND CELL BIOLOGY Volume 40, Number 10, 2021 ª Mary Ann Liebert, Inc. Pp. 1338–1348 DOI: 10.1089/dna.2021.0478 1338 Downloaded by 54.236.23.176 from www.liebertpub.com at 10/16/21. For personal use only.