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Biomedical subjects

D Middleton

Publications and source records attributed to D Middleton.

At least 37 records · Page 2Linked to original sources
PubMed2001

Mismatched human leukocyte antigen alleles protect against heterosexual HIV transmission.

Genetic variation at the human leukocyte antigen (HLA) loci has been shown to be an important risk factor for progression to HIV disease, but its significance in infection is less well understood. We have investigated its role in HIV transmission in a cohort of individuals at risk for heterosexual infection. Analysis of over 80 individuals revealed that that the degree of concordance at HLA A, B, and DR loci differs significantly between transmitting and nontransmitting couples at risk for heterosexual HIV transmission (p <.02), suggesting that allogeneic immune responses may confer a degree of protection against HIV infection. Analysis of the frequencies of specific alleles at the A, B, and DR loci revealed a significantly higher frequency of HLA DR5 among exposed uninfected individuals, relative to population controls.

Alleles↗
PubMed2001

Association between polymorphism in regulatory region of gene encoding tumour necrosis factor alpha and risk of Alzheimer's disease and vascular dementia: a case-control study.

BACKGROUND: Deposition of beta-amyloid in the brains of patients with Alzheimer's disease is thought to precede a chain of events that leads to an inflammatory response by the brain. We postulated that genetic variation in the regulatory region of the gene for the proinflammatory cytokine tumour necrosis factor alpha (TNF-alpha) leads to increased risk of Alzheimer's disease and vascular dementia. METHODS: A polymorphism in the regulatory region of the TNF-alpha gene was analysed in a case-control study. The polymorphism (C-850T) was typed in 242 patients with sporadic Alzheimer's disease, 81 patients with vascular dementia, 61 stroke patients without dementia, and 235 normal controls. These groups of individuals were also genotyped for the apolipoprotein E polymorphism, and the vascular dementia and stroke groups were typed at the HLA-DR locus. FINDINGS: The distribution of TNF-alpha genotypes in the vascular dementia group differed significantly from that in the stroke and normal control groups, giving an odds ratio of 2.51 (95% CI 1.49-4.21) for the development of vascular dementia for individuals with a CT or TT genotype. Logistic regression analysis indicated that the possession of the T allele significantly increased the risk of Alzheimer's disease associated with carriage of the apolipoprotein E epsilon4 allele (odds ratio 2.73 [1.68-4.44] for those with apolipoprotein E epsilon4 but no TNF-alpha T, vs 4.62 [2.38-8.96] for those with apolipoprotein E epsilon4 and TNF-alpha T; p=0.03). INTERPRETATION: Possession of the TNF-alpha T allele significantly increases the risk of vascular dementia, and increases the risk of Alzheimer's disease associated with apolipoprotein E. Although further research is needed, these findings suggest a potential role for anti-inflammatory therapy in vascular dementia and Alzheimer's disease, and perhaps especially in patients who have had a stroke.

Aged↗
PubMed2001

Analysis of the distribution of HLA-B alleles in populations from five continents.

A two stage PCR-SSOP typing procedure, that permitted HLA-B allele assignment, was applied to DNA samples obtained from six diverse populations -Brazilian, Mexican (Series and Mestizos), Cuban (Caucasoid and Mulatto), South African Zulu, Omani, and Singapore Chinese. HLA-B allele frequencies and HLA-A/B two locus haplotype frequencies were compiled for each population.

Alleles↗
PubMed2001

Mitochondrial DNA polymorphism: its role in longevity of the Irish population.

The mtDNA genome has been implicated as playing a pivotal role in determining the longevity and success of the human lifespan. A PCR-RFLP methodology was used to identify polymorphic restriction enzyme sites within a 2643 bp region of the mtDNA genome and a table of genetic haplotypes for a healthy aged and a younger control cohort of patients was constructed. Forty-six different mtDNA haplotypes and 11 groups of related haplotypes were identified across the two age groups but statistical analysis failed to show any significant associations. The European J haplogroup, previously reported to be associated with longevity, was not found at an increased frequency within the Irish aged population (P=0.36). However, the haplotypes comprising the J haplogroup could be differentiated into two distinct branches by the presence or absence of the two polymorphic restriction sites, 16,389g and 16,000g. The branch of haplotypes defined by 16,389g displayed a significant increased frequency in the aged samples (8%) compared to the controls (1%), P=0.015. Inversely, the branch of haplotypes defined by 16,000g displayed a significant decreased frequency in the aged samples (4%) compared to the controls (13%), P=0.011. The polymorphism (mt5178A) associated with longevity in the Japanese was not found in the Irish population, while the polymorphism (mt9055A) associated with successful ageing in the French centenarians was found at an increased frequency in the Irish aged population (9%) compared to the younger control group (5%), but failed to reach a level of statistical significance, P=0.164.

Adult↗
PubMed2001

Comparative pathology of the diseases caused by Hendra and Nipah viruses.

Information on the pathogenesis and transmissibility of Hendra and Nipah viruses was obtained by comparing their histopathology. Both viruses induced syncytial cells in vascular tissues and they were primarily vasotropic and/or neurotropic, generating interstitial pneumonia or encephalitis. Nipah virus in pigs was also epitheliotropic in respiratory epithelium and thus contagious.

Animals↗
PubMed2001

The influence of transforming growth factor-beta1 gene polymorphisms on the severity of gingival overgrowth associated with concomitant use of cyclosporin A and a calcium channel blocker.

BACKGROUND: The purpose of this study was to determine whether the prevalence and severity of gingival overgrowth in renal transplant recipients concomitantly treated with cyclosporin and a calcium channel blocker was associated with functional polymorphisms within the signal sequence of the transforming growth factor-(TGF)beta1 gene. METHODS: The extent and severity of gingival overgrowth for 164 renal transplant recipients immunosuppressed with cyclosporin A and concomitantly taking a calcium channel blocker since transplant were entered into the study (86 in Manchester, 78 in Belfast). Two biallelic polymorphisms of the TGF-beta1 gene were studied at position +869, codon 10 (leucine to proline substitution), and position +915, codon 25 (arginine to proline substitution). RESULTS: Subjects who were homozygous for proline at codon 10 had significantly higher overgrowth scores than those who were heterozygous (P= 0.03) or homozygous for leucine (P= 0.01). Subjects who were heterozygous (arginine/proline) at codon 25 had a significantly higher (P= 0.04) gingival overgrowth score than those who were homozygous for arginine. Logistic regression analysis indicated that for codon 25 independent predictors of severe gingival overgrowth were the heterozygous arginine/proline genotype (P= 0.009) and whether the individual was young (P= 0.05). CONCLUSIONS: Polymorphisms in the TGF-beta1 gene influence the expression of gingival overgrowth in renal transplant recipients concomitantly treated with cyclosporin and a calcium channel blocker. The polymorphism in the TGF-beta1 gene at codon 25 represented an independent genetic determinant of severe gingival overgrowth in the susceptible subjects studied.

Adult↗
PubMed2000

Parvovirus B19 in kidney transplant patients.

Renal transplant patients were screened for the presence of parvovirus B19, before transplantation and monthly for 4 months after transplantation, by means of a sensitive nested PCR assay. Upon screening plasma from 110 patients, we found that two asymptomatic patients were B19 DNA positive. One of these patients was PCR positive in the plasma sample taken 2 months after transplantation; the plasma contained anti-B19 IgG antibodies before transplant and throughout the follow-up period, with an increase in the IgG level in the second posttransplant sample coinciding with the detection of B19 DNA. IgM antibodies to B19 were not detected in this patient. Because, for this patient, the donor's spleen DNA was also B19 DNA positive, we suspect B19 transmission from the donor and limited B19 replication, inasmuch as this patient already had a primed immune response to B19. The other patient was PCR positive in the pretransplant and in the plasma sample taken 1 month after transplant and contained a strong anti-B19 IgG response in the pretransplant sample and throughout the follow-up period-and anti-B19 IgM antibodies were not detected before or after transplantation. By testing samples taken from this patient at 2 weeks, 2 months, and 3 months before transplantation, we were able to determine that the infection occurred shortly before transplantation. Unexpectedly, this graft failed and was removed 2 days after transplantation despite a negative cross-match. A pathological examination of the kidney indicated acute vascular rejection, suggesting a possible role for B19 in this complication.

Antibodies, Viral↗
PubMed2000

Effect of a dCTP:dTTP pool imbalance on DNA replication fidelity in Friend murine erythroleukemia cells.

Nucleotide pool imbalances have been reported to affect the fidelity of DNA replication and repair in prokaryotic and eukaryotic cells. We have reported previously that the mutagen-hypersensitive thymidine kinase (TK)-deficient Friend erythroleukemia (FEL) cells (subclones 707BUF and 707BUE), have a more than sixfold increase in the dCTP:dTTP pool ratio when compared to that of wild-type, TK-positive (TK(+)) clone 707 cells. In this study we present the results of an investigation of the effect of the dCTP:dTTP pool imbalance on the accuracy of DNA replication within 707BUF cells. We examined the spontaneous mutation spectra occurring at the adenine phosphoribosyltransferase (aprt) locus within clone 707 (TK(+)) and 707BUF (TK(-)) FEL cells. Mutations recovered at the aprt locus in FEL cells comprised: base substitutions (43:73), frameshifts (14:13.5), and deletions (43:13.5) [clone 707 (TK(+)):707BUF (TK(-)), respectively, expressed as percentages]. A comparison of the mutation spectra obtained for the two cell lines did not reveal any significant increase in misincorporation of dCTP, the nucleotide in excess, in 707BUF (TK(-)) cells, during DNA replication synthesis. These data suggest that the dCTP:dTTP pool imbalance does not alter the fidelity of DNA replication synthesis in 707BUF (TK(-)) FEL cells. Rather, the predominance of GC --> AT transitions (53%) in the 707BUF (TK(-)) spectrum may reflect a reduced efficiency of repair by uracil DNA glycosylase of uracil residues within these cells.

Adenine Phosphoribosyltransferase↗
PubMed2000

Analysis of the distribution of HLA-A alleles in populations from five continents.

The variation and frequency of HLA-A genotypes were established by PCR-SSOP typing in diverse geographically distributed populations: Brazilian, Colombian Kogui, Cuban, Mexican, Omani, Singapore Chinese, and South African Zulu. HLA-A allelic families with only one allele were identified for HLA-A*01, -A*23, -A*25, -A*31, -A*32, -A*36, -A*43, -A*69, -A*80; and with two alleles for HLA-A*03, -A*11, -A*26, -A*29, -A*33, -A*34, and -A*66. Greater variation was detected for HLA-A*02, -A*24, and -A*68 allele families. Colombian Kogui and Mexican Seris showed the least diversity with respect to HLA-A alleles, albeit with small numbers tested, with only four and five HLA-A alleles identified, respectively. It would appear by their presence in all populations studied, either rural or indigenous, that certain alleles are very important in pathogen peptide presentation.

Africa↗
PubMed2000

Frequency of HLA-B alleles in a Caucasoid population determined by a two-stage PCR-SSOP typing strategy.

High resolution PCR-SSOP typing methods for HLA-B identification have been established and applied to a Northern Ireland population, using large enough numbers to give dependable allele frequencies. The six systems, which operate independently of each other, are intended for use as secondary typing systems following HLA-B identification with a medium resolution PCR-SSOP technique.

Alleles↗
PubMed2000

Development of a PCR-SSOP approach capable of defining the natural killer cell inhibitory receptor (KIR) gene sequence repertoires.

A molecular typing method based on polymerase chain reaction (PCR) amplification of three different target domains (immunoglobulin domains 1 and 3, and the transmembrane-cytoplasmic domain), followed by hybridisation with 26 digoxigenin-labelled sequence-specific oligonucleotide probes (SSOP) has been established for the polymorphic killer inhibitory receptor (KIR) genes. In addition to identifying the 12 KIR subfamilies, our PCR-SSOP typing approach could also distinguish the putative alleles, NKB1 and NKAT3, that comprise the KIR3DL1 subfamily. Ninety unrelated blood donors and 13 families (52 individuals), including both parents, were subjected to our KIR PCR-SSOP typing approach. All 12 KIR subfamilies, including a 2DS5 variant sequence, were present in the 90 individuals and displayed varied phenotype frequencies: 2DL1 (0.96), 2DL2 (0.31), 2DL3 (0.95), 2DS1 (0.56) 2DS2 (0.51), 2DS3 (0.27), 2DS4 (0.96), 2DS5v (0.35), 3DS1 (0.47), 3DL1 (0.96), 3DL2 (1.0) and 2DL4 (1.0). A total of 23 different KIR phenotypes were defined in this study, and 10 of these were only found on one occasion in one individual, indicating considerable diversity in the KIR phenotype profiles within the Irish population. Most individuals (93%) possessed the complement of inhibitory KIR specificities for the three well-defined HLA-B and -C ligands. An unusual probe pattern for 3DS1 was observed in 3 individuals indicating a variant 3DS1 gene sequence with changes at nucleotide positions 1185-1186, within the cytoplasmic domain. Sequencing analysis revealed a new single nucleotide polymorphism in exon 3 of 3DL1 NKB1(195, G-A) and a 22-bp deletion polymorphism in exon 5 of 2DS4 (nucleotides 777-798 deleted). A number of strong KIR associations were observed, namely 2DL1 with 2DL3, 2DS4 with 3DL1, 2DL2 with 2DS1/2DS2/2DS3, 2DS1 with 2DS3/2DS5v/3DS1, 2DS2 with 2DS3 and 2DS5v with 3DS1. Analysis of the KIR segregation observed in the 13 families confirmed these strong associations and permitted the definition of a number of partial KIR haplotypes, e.g. 2DL2-2DS1-2DS2-2DS3-3DL1. The segregation analysis concluded that at least 3 distinct gene loci encode 2DL1-4 and at least 4 gene loci encode the non-inhibitory KIR2DS1-2DS5. In the case of 3DL1-2 and 3DS1, our data suggests 3 gene loci, one for each subfamily.

Humans↗
PubMed2000

HLA class II typing of whole genome amplified mouth swab DNA.

Postal collection of mouth swabs provides a cheap and convenient means of DNA sampling but hitherto has not provided sufficient genetic material for HLA typing by polymerase chain reaction using sequence-specific primers (PCR-SSP). This study examined the feasibility of collecting mouth swabs from a test population by post, amplifying the DNA by whole genome amplification and genotyping for selected HLA class II alleles. We optimised a strategy for whole genome amplification or primer extension preamplification using a random 15 base pair primer which resulted in a 1,000-fold increase in DNA template. The amplified DNA was of sufficient quality for analysis of selected HLA Class II alleles by PCR-SSP and PCR using sequence-specific oligonucleotide probes. To test the reliability of our data, blood DNA from 30 individuals in 10 families, previously tested for all DRB1 alleles in a routine diagnostic laboratory, was then tested in our laboratory for DRB1 *03 and *04 following whole genome amplification. Further whole genome amplified product from another 10 families was tested for DRB1 *03, *04 in our laboratory and then tested for all DRB1 alleles in a routine diagnostic laboratory. One repeat typing was required to achieve 100% concordance between laboratories. Amplification of whole genome amplified DNA by PCR-SSP was then extended successfully to low-resolution HLA DRB1, DQA1, DQB1 and DPB1 typing. Mouth swab collection by post, followed by whole genome amplification of DNA provides an effective strategy for genetic analysis of large cohorts. We have optimised conditions for HLA class II typing on whole genome amplified DNA collected by mouth swab, but this method could potentially be applied to low concentrations of DNA from other sources.

Adult↗
PubMed2000

Genetic polymorphism of IL-12 p40 gene in immune-mediated disease.

Understanding of the genetic basis of autoimmune diseases is currently incomplete. Cytokine gene polymorphisms warrant consideration as factors explaining variation in the human immune and inflammatory responses and as candidate susceptibility genes for related pathological states. Interleukin 12 (IL-12) is a key regulator of the polarisation of immune responses to T helper 1 or 2 categories and plays a role in autoimmune and infectious diseases. Using a bioinformatic strategy, we aligned cDNA and expressed sequence tag sequences to identify putative polymorphic regions of the IL-12 p40 gene. Position 1188 in the 3' untranslated region (UTR) was polymorphic with the frequency of the common allele around 80% in healthy UK Caucasoids. PCR genotyping of multiple Caucasoid groups and an African group showed significant population variation. In a case-control design, the polymorphism was not associated with rheumatoid arthritis, Felty's syndrome or large granular lymphocyte syndrome with arthritis or multiple sclerosis. A nonsignificant increase in the B allele frequency was observed in the rare large granular lymphocyte syndrome without arthritis (odds ratio 2.02 95% CI 0.95-4.3). This new genetic marker could be useful in anthropological studies and should be investigated in other autoimmune, allergic, inflammatory and infectious diseases.

Alleles↗