An extended HLA-D region haplotype associated with celiac disease

Celiac disease has one of the strongest associations with HLA (human leukocyte antigen) class II markers of the known HLA-linked diseases. This association is primarily with the class II serologic specificities HLA-DR3 and -DQw2. We previously described a restriction fragment length polymorphism (RFLP) characterized by the presence of a 4.0-kilobase Rsa I fragment derived from an HLA class II beta-chain gene, which distinguishes the class II HLA haplotype of celiac disease patients from those of many serologically matched controls. We now report the isolation of this beta-chain gene from a bacteriophage genomic library constructed from the DNA of a celiac disease patient. Based on restriction mapping and differential hybridization with class II cDNA and oligonucleotide probes, this gene was identified as one encoding an HLA-DP beta chain. This celiac disease-associated HLA-DP beta-chain gene was flanked by HLA-DP alpha-chain genes and, therefore, was probably in its normal chromosomal location. The HLA-DP alpha-chain genes of celiac disease patients also were studied by RFLP analysis; 84% of HLA-DR3, -DQw2 patients had a 16-kb Xba I fragment that was present in only 36% of HLA-DR3, -DQw2 controls. Moreover, 79% of these patients had both alpha- and beta-chain polymorphisms in contrast to 27% of controls. Thus, celiac disease is associated with a subset of HLA-DR3, -DQw2 haplotypes characterized by HLA-DP alpha- and beta-chain gene RFLPs. Within the celiac-disease patient population, the joint segregation of these HLA-DP genes with those encoding the serologic specificities HLA-DR3 and -DQw2 indicates: (i) that the class II HLA haplotype associated with celiac disease is extended throughout the entire HLA-D region, and (ii) that celiac-disease susceptibility genes may reside as far centromeric on this haplotype as the HLA-DP subregion.

Production of murine leukemia virus in the immunodeficient wasted mutant mouse is associated with the wst allele

The recessive mutation "wasted" (wst) is responsible for a neuroimmunological syndrome and premature death in homozygous wst/wst mice. In contrast, +/wst heterozygotes appear phenotypically normal. The present study assessed the production of endogenous murine leukemia virus (MuLV) in lymphoid organs of homozygous wasted (wst/wst), heterozygous wasted (+/wst) and control wild type (+/+) mice. Neither mutant nor control mice produced ecotropic MuLV. In contrast, lymphoid organs from wst/wst and +/wst mice produced endogenous xenotropic MuLV. MuLV production was not detectable in the same organs of +/+ control mice. +/wst heterozygotes produced xenotropic MuLV in the thymus, spleen and mesenteric lymph nodes but not in the bone marrow. Wst/wst mutants produced xenotropic MuLV, but only in the thymus. These findings demonstrate an association between the production of endogenous xenotropic MuLV and the wasted mutation.

Spurious DNA blot hybridization resulting from bacterial contamination of primary tissue preparations

We have observed, by Southern blot hybridization, numerous episomes in DNA prepared from tumors grown as athymic mouse xenografts. These extrachromosomal DNAs were present in multiple copies and existed as relaxed and supercoiled conformational isomers. The episomes were readily detected with pBR322 plasmid probes, but not with purified plasmid inserts. Subsequently, four species of bacteria were isolated from tumor xenografts, suggesting that the pBR322 related episomes which we observed were bacterial DNAs, copurified during the isolation of xenograft DNA. This finding illustrates a potential problem which may be encountered in blot hybridizations utilizing nucleic acids from primary tissue preparations.

Rapid identification of hybridization probes for chromosomal walking

The presence of repeated elements in restriction fragments used as hybridization probes for chromosomal walking poses a major obstacle to the success of this gene-cloning strategy. This report describes a simple and rapid means of identifying restriction fragments devoid of repeated sequences and therefore useful as hybridization probes for chromosomal walking. Restriction fragments derived from a genomic DNA clone are Southern blotted and hybridized to nick-translated total genomic [32P]DNA. Fragments of the genomic clone that contain high abundance sequences (i.e., repeated elements) hybridize strongly to their nick-translated counterparts, which, due to their high copy number, comprise a significant proportion of the total genomic DNA probe. Conversely, fragments containing single-copy or low-abundance sequences do not hybridize, as their nick-translated counterparts are poorly represented in the total genomic DNA probe. These latter fragments, by virtue of their low-abundance sequences, are well suited as probes for chromosomal walking. Ensuring the absence of repeated elements in restriction fragments prior to their purification and utilization as chromosomal walking probes results in marked savings of time, effort and materials.

An HLA-D region restriction fragment length polymorphism associated with celiac disease

This study is the first to describe a molecular marker that distinguishes the celiac disease HLA-D region haplotype from a serologically identical haplotype in unaffected controls. Using a DQ beta chain cDNA probe and the restriction endonuclease Rsa I, we have detected a polymorphic 4.0 kb fragment which, in DQw2 individuals, is associated with a 40-fold increased relative risk of developing celiac disease. This finding should permit the identification of the celiac disease susceptibility gene(s) in the HLA-D region and facilitate a more precise dissection of the molecular and immunogenetic mechanisms involved in the pathogenesis of that disease.

Toxicity of ricin, diphtheria toxin and alpha-Amanitin for Acanthamoeba castellanii (1983)

Selective cytotoxic agents, highly specific antibody coupled to potent toxin molecules, could, theoretically, be useful in the treatment of protozoan infections. To examine this possibility we began to synthesize immunotoxins for a model protozoan system, Acanthamoeba castellanii. We report here the selection of a suitable toxic moiety for this system. alpha-Amanitin was toxic for the amoeba, effecting a 50% decrease in in vivo protein synthesis at approximately 20 microM. However, the chemical modification of alpha-amanitin necessary for its covalent attachment to antibody molecules reduced A. castellanii toxicity to the extent that alpha-amanitin is unsuitable as a toxic moiety in the synthesis of A. castellanii immunotoxins. Ricin and diphtheria toxin were non-toxic for the amoeba. In addition, A. castellanii cell-free protein biosynthesis, unlike that of any other eukaryotic system examined to date, was resistant to inhibition by ricin A chain. However, diphtheria toxin A chain inhibited A. castellanii cell-free protein synthesis by 50% at 2.5 nM. The inhibition of diphtheria toxin was NAD+ dependent, suggesting that ADP-ribosylation of EF-2 could be the cause of the inhibition as it is in mammalian cell lines. The toxicity of diphtheria toxin A chain is sufficient for its use in the synthesis of immunotoxins for A. castellanii.