Integrated analyses of a major histocompatibility complex, methylation and transcribed ultra-conserved regions in systemic lupus erythematosus

Long Noncoding RNA HCP5, a Hybrid HLA Class I Endogenous Retroviral Gene: Structure, Expression, and Disease Associations

The HCP5 RNA gene (NCBI ID: 10866) is located centromeric of the HLA-B gene and between the MICA and MICB genes within the major histocompatibility complex (MHC) class I region. It is a human species-specific gene that codes for a long noncoding RNA (lncRNA), composed mostly of an ancient ancestral endogenous antisense 3′ long terminal repeat (LTR, and part of the internal pol antisense sequence of endogenous retrovirus (ERV) type 16 linked to a human leukocyte antigen (HLA) class I promoter and leader sequence at the 5′-end. Since its discovery in 1993, many disease association and gene expression studies have shown that HCP5 is a regulatory lncRNA involved in adaptive and innate immune responses and associated with the promotion of some autoimmune diseases and cancers. The gene sequence acts as a genomic anchor point for binding transcription factors, enhancers, and chromatin remodeling enzymes in the regulation of transcription and chromatin folding. The HCP5 antisense retroviral transcript also interacts with regulatory microRNA and immune and cellular checkpoints in cancers suggesting its potential as a drug target for novel antitumor therapeutics.

The prevalence of HLA alleles in a lupus nephritis population

BACKGROUND

Systemic lupus erythematosus (SLE) is a severe autoimmune disease that involves multiple organ systems. Lupus nephritis (LN) is a complication of SLE and is associated with poor survival and high morbidity. Many genomic studies have been performed worldwide, and several histocompatibility leukocyte antigen (HLA) loci are linked to lupus susceptibility.

OBJECTIVE

The present study evaluated the association of HLA alleles in a lupus patient population, LN group and control group. The second objective evaluated whether HLA allele match or mismatch influenced kidney graft survival in a kidney transplanted lupus population.

METHODS

This study was a retrospective study of 2 major groups: general lupus patients (GSLE - n = 108) and a control group (GControl - n = 216). Both groups were also divided into subgroups.

RESULTS

The control group was divided into two subgroups: a healthy control group (HeCTRL) and transplant control group (TxCTRL). The GSLE group was composed of transplanted lupus patients (TxSLE) and non-transplanted lupus patients (nTxSLE). Comparison of the demographics between groups did not reveal differences between ethnicity and gender. A difference in the prevalence of three alleles, B*08, DRB1*08 and DRB1*15, was observed. These alleles were more prevalent in the lupus subgroups compared to the control groups. Five-year survival was not different between patients carrying the allele DRB1*15 in either group (overall p = 0.075; TxSLE p = 0.419; TxCTRL = 0.309). The presence of the match with this allele in the receptor was evaluated and did not demonstrate any difference in graft survival in both groups (p = 0.146) or when analyzed separately in each group (TxCTRL p = 0.739; TxSLE = 0.297).

CONCLUSION

This study demonstrated that the presence of HLA-DRB1*15 was a strong factor that predisposed patients to the development of SLE and LN, but did not influence kidney graft survival.