The immunogenetics of smallpox vaccination.

We hypothesized that individuals who develop fever after smallpox vaccination have genetically determined differences in their immune responses to vaccinia virus. We looked for an association between the development of fever and single-nucleotide polymorphisms (SNPs) in 19 candidate genes in 346 individuals previously assessed for clinical responses to smallpox vaccination. Fever after smallpox vaccination is associated with specific haplotypes in the interleukin (IL)-1 gene complex and in the IL18 gene. A haplotype in the IL4 gene was highly significant for reduced susceptibility to the development of fever after vaccination among vaccinia-naive individuals. Our results indicate that certain haplotypes in the IL-1 gene complex and in IL18 and IL4 predict an altered likelihood of the development of fever after smallpox vaccination. Our findings also raise the possibility that these same haplotypes may identify individuals at risk for the development of fever after receipt of other live virus vaccines, providing information that could be useful in anticipating and preventing more-serious adverse events.

Localization of PSORS1 to a haplotype block harboring HLA-C and distinct from corneodesmosin and HCR.

Psoriasis is a complex inflammatory disease of the skin affecting 1-2% of the Caucasian population. Associations with alleles from the HLA class I region (now known as PSORS1), particularly HLA-Cw*0602, were described over 20 years ago. However, extensive linkage disequilibrium (LD) within this region has made it difficult to identify the true susceptibility allele from this region. A variety of genes and regions from a 238-kb interval extending from HLA-B to corneodesmosin (CDSN) have been proposed to harbor PSORS1. In order to identify the minimum block of LD in the MHC class I region associated with psoriasis we performed a comprehensive case/control and family-based association study on 242 Northern European psoriasis families and two separate European control populations. High resolution HLA typing of HLA-A, -B and -C alleles was performed, in addition to the genotyping of 18 polymorphic microsatellites and 36 SNPs from a 772-kb segment of the HLA class I region harboring the previously described interval. This corresponded on average to one SNP every 7 kb in the candidate 238 kb region. With all tests, the association was the strongest with single markers and haplotypes from a block of LD harboring HLA-C and SNP n.9. Logistic regression analyses indicated that association seen with candidate genes from the interval such as CDSN and HCR was entirely dependent on association with HLA-Cw*0602 and SNP n.9-G alleles. The previously reported association with CDSN and HCR was observed to be due to the existence of the associated alleles lying on the most commonly over-transmitted haplotype. Rare over-transmitted haplotypes also harbored HLA-Cw*12 alleles. HLA-Cw*12 family members are closely related to HLA Cw*0602, sharing identical sequences in their alpha-2 domains, peptide-binding pockets A, D and E and all 3' introns. The introduction of a potential binding site for the RUNX/AML family of transcription factors in intron 7, is also specific to these HLA-C alleles. These variants need to be investigated further for their role as PSORS1.

The Tetratricopeptide repeat domain 7 gene is mutated in flaky skin mice: a model for psoriasis, autoimmunity, and anemia.

The flaky skin (fsn) mutation in mice causes pleiotropic abnormalities including psoriasiform dermatitis, anemia, hyper-IgE, and anti-dsDNA autoantibodies resembling those detected in systemic lupus erythematosus. The fsn mutation was mapped to an interval of 3.9 kb on chromosome 17 between D17Mit130 and D17Mit162. Resequencing of known and predicted exons and regulatory sequences from this region in fsn/fsn and wild-type mice indicated that the mutation is due to the insertion of an endogenous retrovirus (early transposon class) into intron 14 of the Tetratricopeptide repeat (TPR) domain 7 (Ttc7) gene. The insertion leads to reduced levels of wild-type Ttc7 transcripts in fsn mice and the insertion of an additional exon derived from the retrovirus into the majority of Ttc7 mRNAs. This disrupts one of the TPRs within TTC7 and may affect its interaction with an as-yet unidentified protein partner. The Ttc7 is expressed in multiple types of tissue including skin, kidney, spleen, and thymus, but is most abundant in germinal center B cells and hematopoietic stem cells, suggesting an important role in the development of immune system cells. Its role in immunologic and hematologic disorders should be further investigated.

Novel immunoglobulin superfamily gene cluster, mapping to a region of human chromosome 17q25, linked to psoriasis susceptibility.

Chromosome 17q25 harbors a susceptibility locus for psoriasis ( PSORS2). This locus may overlap with loci for atopic dermatitis and rheumatoid arthritis. To further refine the location of PSORS2, we genotyped 242 primarily nuclear families for 15 polymorphic microsatellites mapping to chromosome 17q23-q25. Non-parametric linkage analysis revealed a linkage peak lying close to a novel cluster of genes from the immunoglobulin (Ig) superfamily. This cluster spans >250 kb and harbors five CMRF35-like genes and a sixth inhibitory receptor ( CMRF35H) with three ITIM motifs that is transcribed in the opposite direction from the rest. The Ig domains encoded by these genes are most similar to those of the TREM (triggering receptor expressed selectively in myeloid cells) molecules, NKp44 and the polymeric immunoglobulin receptor. CMRF35-like genes are only expressed in sub-populations of cells of the myeloid lineage. In order to investigate the association of this region with psoriasis, we genotyped the families for 13 novel microsatellites and 19 SNPs from the region of linkage. A maximum NPL of 1.6 ( P=0.05) was obtained within the interval. Two SNP-based haplotypes revealed some evidence for association with psoriasis. One spanned CMRF35H and includes a non-synonymous polymorphism within CMRF35H (R111Q) (TDT P=0.03). The second was a three-locus haplotype lying within the first intron of CMRF35A2 ( TREM5) (TDT P=0.04). The novel markers described here will facilitate additional linkage and association studies between the CMRF35 family and disease.

Paternal origins of complete hydatidiform moles proven by whole genome single-nucleotide polymorphism haplotyping.

Complete hydatidiform moles (CHMs) are diploid tumors that result from fertilization of an empty ovum by a haploid 23,X sperm. In most cases, the resulting duplication of the genome gives rise to a 46,XX genotype and is thought to be androgenetic in origin. If this hypothesis is correct, then the genotypes of all polymorphic markers in CHMs should be homozygous. We used a dense set of single-nucleotide polymorphism (SNP) markers, evenly spaced throughout the genome, to definitively test this hypothesis. We genotyped genomic DNA samples from five CHMs and their corresponding maternal samples with 1494 SNP markers using high-density microarrays (HuSNP). As predicted, the maternal samples were heterozygous at >25% of the markers, which is consistent with the expected average heterozygosity of this panel of SNPs. In contrast, the five CHM samples were heterozygous at <0.75% of the SNP markers, which shows that these diploid tumors consist of a duplicated set of chromosomes. Because the CHM genotypes represent the haplotypes of their genomes, our results show that long-range haplotypes can be obtained easily with this resource and that a collection of such samples is a simple way to obtain reference haplotypes for association studies in various populations.