The microbiome and rheumatic heart disease: current knowledge and future perspectives.

Rheumatic heart disease (RHD) is a cardiovascular disease caused by an autoimmune response to group A Streptococcus (GAS) infection resulting in the damage of heart valves. RHD is the most commonly acquired heart disease among children and young adults with a global burden of over 40 million cases accounting for 306,000 deaths annually. Inflammation in the heart valves caused due to molecular mimicry between the GAS antigens and host cardiac proteins is facilitated by cytokines, cross-reactive antibodies and CD4+ T cells. The complex interaction between genetic and environmental factors linked with erratic events leads to the loss of immunological tolerance and autoimmunity in RHD. Despite extensive research on the etiopathogenesis of RHD, the precise mechanism underpinning the initiation of acute rheumatic fever (ARF) to the progression of RHD still remains elusive. Mounting evidences support the contribution of the human microbiome in the development of several immune-mediated diseases including rheumatoid arthritis, juvenile idiopathic arthritis, Kawasaki disease, inflammatory bowel disease and type 1 diabetes. The microbiome and their metabolites could play a crucial role in the integrity of the epithelial barrier, development of the immune system, inflammation and differentiation of T cell subsets. Consequently, microbiome dysbiosis might result in autoimmunity by molecular mimicry, epitope spreading and bystander activation. This review discusses various aspects of the interaction between the microbiome and the immune system in order to reveal causative links relating dysbiosis and autoimmune diseases with special emphasis on RHD.

Association of HLA-DRB1 Alleles with Rheumatic Fever and Rheumatic Heart Disease: A Meta-analysis.

BACKGROUND: Rheumatic fever (RF) and its sequel rheumatic heart disease (RHD) is an autoimmune disease caused by an abnormal host immune response to group A streptococcus (GAS) infection. The HLA class II molecules are entailed in immune-mediated infectious, inflammatory, and autoimmune diseases including RHD. However, HLA class II genes are reported to be associated with RF/RHD across different populations with a very little consistency. OBJECTIVE: The aim of the study is to investigate the association between HLA class II genes and RF/RHD by meta-analysis. METHODS: A comprehensive literature search was conducted to identify all relevant case-control studies published before December 31, 2019. The data were extracted using standardized form and pooled odds ratio (OR) with 95% confidence interval (CI) are calculated to assess the strength of the association between HLA class II genes and RF/RHD. RESULTS: Thirteen studies for HLA-DRB1 alleles (1065 patients and 1691 controls) and eight studies for HLA-DQB1 alleles (644 patients and 1088 controls) were finally included. The meta-analysis showed a significantly higher frequency of HLA-DRB1*07 allele (OR = 1.68, P < .0001) in RF/RHD patients when compared to controls, while the frequency of HLA-DRB1*15 allele (OR = 0.60, P = .03) was significantly lower in RF/RHD patients than in controls. However, there were no significant differences in the frequency of HLA-DQB1 alleles between RF/RHD patients and controls. CONCLUSIONS: The results of the meta-analysis suggest that the differential presentation of autoimmune peptides by HLA-DRB1*07 (susceptible) and HLA-DRB1*15 (protective) alleles with different affinities may play a crucial role in the pathogenesis of RF/RHD.

Association of HLA-G 3'UTR 14-bp Ins/Del polymorphism with breast cancer among South Indian women.

AIM: Human leucocyte antigen-G (HLA-G) and tumour necrosis factor-alpha (TNF-α) are potent immune mediators implicated in the pathogenesis of breast cancer. The polymorphisms in the 3' untranslated region (3'UTR) of HLA-G and promoter region of TNF-α are well known to influence their expression levels and may consequently contribute to varied disease predisposition. Therefore, in the present study, we explored the effect of HLA-G 3'UTR (14-bp Ins/Del and +3142 C/G) and TNF-α promoter (-238 G/A and -308 G/A) polymorphisms on breast cancer risk among South Indian women. METHODS: A total of 342 women (100 patients with breast cancer, 142 patients with benign breast disorder and 100 healthy women volunteers) were enrolled for this study. Genotyping of HLA-G and TNF-α polymorphisms were performed by direct PCR DNA amplification and amplification refractory mutation system PCR methods, respectively. RESULTS: Significantly higher frequencies of HLA-G 14-bp Ins allele and Ins/+3142G haplotype were observed in patients with breast cancer than healthy controls (OR=1.56, Pc=0.036) and patients with benign breast disorder (OR=1.47, Pc=0.046). Similarly, subgroup analysis based on age at diagnosis (age≤50 years and >50 years) of breast cancer revealed higher frequencies of 14-bp Ins allele and Ins/+3142G haplotype in the patients of age >50 years than healthy controls (OR=1.77, Pc=0.03). Additionally, the extended haplotypes and multifactor dimensionality reduction analysis of the studied polymorphisms revealed significant contribution of HLA-G 14-bp Ins/Del polymorphism towards breast cancer risk. CONCLUSION: The findings of the present study suggest that the HLA-G 14-bp Ins/Del polymorphism could influence breast cancer pathogenesis among South Indian women.

Combination of ramipril and rutin alleviate alloxan induced diabetic nephropathy targeting multiple stress pathways in vivo.

Diabetic nephropathy (DN) is considered as one of the major microvascular complications of diabetes mellitus (DM) which leads to end stage renal disease (ESRD). Even though existing therapeutic options are effective in decreasing albuminuria, drugs targeting the preservation of GFR and prevention of ESRD may provide better strategy for the treatment. Since metabolic disorders are multifactorial, poly-herbal medications, and drug-herbal combination are in demand. Therefore, the present work is focused on the combinatorial renoprotective effect of rutin and ramipril on alloxan induced DN in experimental rats. Male Wistar rats were divided into five groups, group I-control, group II-diabetic rats, group III-diabetic rats treated with ramipril, group IV-diabetic rats treated with rutin, group V-diabetic rats treated with ramipril and rutin for a period of six weeks. Results revealed administration of alloxan induced hyperglycemia and alteration in antioxidant profile. However, combination of a bioflavonoid with an Angiotensin converting enzyme (ACE) inhibitor administration restored the antioxidant status in experimental DN rats. Over-expression of ACE, TGF-ß1 and decreased podocin expression in diabetic rats was significantly reversed in rats administered with both ramipril and rutin. In addition to attentuating oxidative stress and fibrosis, combinatorial therapy significantly down-regulated endoplasmic reticulum stress markers GRP78 and CHOP. Notably, combination of both ramipril and rutin in low doses reduced the side effects than the administration of monotherapy alone. Histopathological results revealed that combinatorial therapy was associated with a reduction in tubulointerstitial injury. The current study contributes the understanding of the multifactorial nature of DN and implies combinatorial treatment of ACE inhibitor with an antioxidant will be a promising therapeutic strategy for DN by their mechanism of action targeting various pathophysiological changes and stress pathways.

Inhibitory natural killer cell receptor KIR3DL1 with its ligand Bw4 constraints HIV-1 disease among South Indians.

OBJECTIVE: To investigate the role of genotypic and phenotypic characteristics of killer cell immunoglobulin-like receptors (KIRs) and their human leukocyte antigen (HLA) class-1 ligands in HIV-1 disease progression. STUDY DESIGN AND METHODS: This is a nested case-control study including 347 HIV seropositive (HIV-1+) individuals from South India constituting 45 long-term nonprogressors (LTNPs) and 302 disease progressors. KIR genotyping was performed by multiplex sequence-specific primer-directed PCR (SSP-PCR). Phenotypic expressions of KIR3DL1/S1 was studied using multiparametric flow cytometry assay. HLA-Bw4 and Bw6 epitopes were determined by ARMS-PCR. HLA-Bw4I80, HLA-Bw4T80, HLA-C1, HLA-C2, and HLA-Aw4 were genotyped using SSP-PCR. Serum levels of IFN-γ was quantified using ELISA method. RESULTS: Overall, 37 different KIR genotypes were observed and the distribution of genotypes with AB-AB (OR = 2.2, P = 0.033) constellations showed significant increase among LTNPs. The frequencies of 3DL1-2DL3-2DL5 (OR = 2.2, Pc = 0.031), 3DL1-Bw4/Aw4 (OR = 2.49, Pc = 0.019), homozygous Bw4 (OR = 2.422, Pc = 0.011) were observed higher in LTNPs and 2DS1-2DS2-2DS3 (OR =  0.475, Pc = 0.03), homozygous Bw6 (OR = 0.413, Pc = 0.011) were higher in the disease progressors. Flow cytometry assay showed the increased expression and maintenance of 3DL1/S1+NK cells in LTNPs (P = 0.0001). Further the expansion of 3DS1+NK cells was higher than 3DL1+NK cells in the heterozygous 3DL1/S1 LTNPs (P = 0.001). CONCLUSION: The inhibitory receptor 3DL1 with Bw4 and its A-haplotype defining KIR genes (2DL3/L5) confers protection against HIV-1 disease progression. An increased expression and maintenance of 3DL1/S1+ natural killer cells may contribute to the efficient activation of the natural killer cells and subsequent long-term nonprogression (LTNPn) to the disease.

Lack of Association Between TNF-α, IFN-γ, IL-10 Gene Polymorphisms and Rheumatic Heart Disease in South Indian Population.

BACKGROUND: Proinflammatory and anti-inflammatory cytokines play a crucial role in the development and maintenance of immune mediated inflammatory diseases including rheumatic heart disease (RHD). Polymorphisms in tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and interleukin (IL)-10 genes influence the differential cytokine expression as well as the pathogenesis of various inflammatory and autoimmune diseases. OBJECTIVE: The aim of the study is to investigate the association between TNF-α, IFN-γ, and IL-10 gene polymorphisms and RHD in South Indian population. MATERIALS AND METHODS: TNF-α (-308, -238), IFN-γ (+874), and IL-10 (-1082, -819, -592) gene polymorphisms were determined in 100 patients with RHD and 127 healthy siblings by PCR. RESULTS: There was no significant difference in the genotype, allele, and haplotype frequencies of TNF-α, IFN-γ, and IL-10 polymorphisms between RHD patients and healthy siblings. CONCLUSION: The present study suggests that TNF-α, IFN-γ, and IL-10 gene variants may not be associated with the development of RHD in South Indian population.

Association of IL17 and IL23R gene polymorphisms with rheumatic heart disease in South Indian population.

BACKGROUND: IL-23/Th17 signaling pathway plays a crucial role in the cell-mediated immune response against bacterial infections and also in the pathogenesis of inflammatory and autoimmune diseases. Recent studies indicate that Th17 cell-associated cytokines are involved in the progression and maintenance of valvular lesions in rheumatic heart disease (RHD). Variants in the genes of cytokines that are potentially involved in Th17 response may influence interindividual differences in their expression levels, thereby contributing to the pathogenesis of immune-mediated diseases such as RHD. OBJECTIVE: The aim of the study is to investigate the association of IL17A, IL17F, and IL23R gene variants with the risk perception of RHD. METHODS: A total of 225 individuals (99 RHD patients and 126 healthy siblings) were recruited for the study. The IL17A (rs2275913), IL17F (rs763780), and IL23R (rs10889677) polymorphisms were determined by polymerase chain reaction restriction fragment length polymorphisms and amplification-refractory mutation system-polymerase chain reaction methods, respectively. RESULTS: The frequency of IL17A (rs2275913) A/A genotype was significantly high in pooled RHD patients (odds ratio [OR] = 2.76; pc = 0.021), rheumatic fever (RF) patients (OR = 14.5; pc = 0.0001), and mitral valvular lesions patients (OR = 2.74; pc = 0.039) when compared to healthy siblings. However, the IL17F (rs763780) and IL23R (rs10889677) polymorphisms did not show any association with RHD. CONCLUSIONS: The results suggest that IL17A (rs2275913) polymorphism is associated with the development of RF/RHD in South Indian population. Further studies are required to substantiate the association of these genes with the disease risk.

"HLA-G 3'UTR gene polymorphisms and rheumatic heart disease: a familial study among South Indian population".

BACKGROUND: Rheumatic heart disease (RHD) is an autoimmune disease where cross reactive CD4+ T cells are involved in the pathogenesis of valvular damage. Human Leukocyte Antigen-G (HLA-G), an immunosuppressive molecule playing a crucial role in the inhibition of T cell response is associated with the pathogenesis of various autoimmune and inflammatory diseases. Genetic polymorphisms within the 3'untranslated region (UTR) of HLA-G influences its expression and thus disease pathogenesis. Hence, the present study aims to unravel the association of 14 bp Ins/Del (rs66554220) and +3142 C/G (rs1063320) polymorphisms in 3' UTR of HLA-G with RHD. METHODS: This familial study consists of 99 RHD families (99 RHD patients, 140 parents and 126 healthy siblings). The 14 bp Ins/Del and +3142 C/G polymorphisms were evaluated by PCR using sequence specific primers and its transmission disequilibrium (TD) was tested by TD test in 70 trio families. RESULTS: The frequency of +3142 C/C genotype was high in patients with combined valvular lesions (CVL) (OR = 5.88; pc = 0.012) and pooled RHD patients (P: OR = 2.76; p = 0.043; pc = 0.076) when compared to healthy siblings. Under the additive (OR = 5.50; pc = 0.026) and recessive genetic model (OR = 5.88; pc = 0.012), the +3142 C/C genotype was significantly associated with CVL in patients. CONCLUSION: The results suggest that the +3142 C/C genotype may be associated with minor risk for the development of RHD and is more likely to influence the severity of the disease.

Predominance of B haplotype associated KIR genes in Tamil Speaking Dravidians.

Killer cell immunoglobulin like receptors (KIRs) are a group of activating (aKIRs) and inhibitory receptors (iKIRs) expressed on subsets of lymphoid cells. Their interaction with HLA class I molecules modulate the innate and adaptive immune response against infections and malignancies. KIR haplotypes varies in gene content and also at allelic level, thereby, distinguishing individuals and populations. Hence, the present study is aimed to determine the KIR gene diversity in Piramalai Kallar (PK) population of South India. The PK population shows diverged KIR gene frequencies and novel haplotypes than other South Indian populations. 52 different KIR gene profiles were identified and 18 of them were new in this population. In phylogenetic analysis the study population is positioned between African and Iranian population in the clade, which supports the South African ancestry of Indian population.