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Polymorphic genotypes of the HRES-1 human endogenous retrovirus locus correlate with systemic lupus erythematosus and
C Magistrelli1, E Samoilova, R K Agarwal
1Departments of Medicine, Microbiology and Immunology, and Pathology State University of New York Health Science Center, College of Medicine, SUNY HSC, 750 East Adams Street, Syracuse, NY 13210, USA.
Abstract:
Antinuclear autoantibodies are a hallmark of systemic lupus erythematosus (SLE). Autoantibodies to HRES-1/p28, a 28 000 M(r) nuclear protein, commonly occur in patients with SLE. HRES-1 is a single-copy endogenous retroviral element mapped to human Chromosome 1 at q42. A polymorphic Hin dIII site defines two different allelic forms of the genomic locus. The HRES-1/1 probe [5.5 kilobases (kb)] anneals to three polymorphic fragments and three genotypes can be differentiated: I, 5.5 kb fragment only; II, 3.7 kb and 1.8 kb fragments only; and III, all three polymorphic fragments. By cloning of the HRES-1 locus from homozygous type I and type II human DNA samples, the polymorphic Hin dIII site was identified as a G to C transition at position 653 of the long terminal repeat region. Family studies showed that Hin dIII genotypes of the HRES-1 locus are inherited in a Mendelian pattern. The relative frequency of genotype I with respect to genotype III was 3.1-fold lower in patients with SLE (14:40=0.35) in comparison to 100 ethnically matched control donors (47:43=1.09; P=0.0084). Frequency of genotype I vs genotype II alleles was lower in SLE (68/52) than in normal donors (137/63; P=0.033), suggesting that a genotype I allele of the HRES-1 locus may be protective against SLE. Western blot seroreactivity with recombinant HRES-1/p28 was noted in 4/14 (29%) of genotype I patients and 13/19 (68%) of genotype III patients (P<0.025). These data raise the possibility that the HRES-1 element or a gene in linkage disequilibrium with this genomic locus may influence autoimmunity in SLE.