A structural variant of the human interferon-gamma gene.

The first structural IFNG variant, G54D (c.287G>A, ss105106770), located in the second exon, was identified.

YAC/BAC contig spanning the MHC class III region of cattle.

A contig of the class III region of the bovine major histocompatibility complex (MHC) was established from bacterial and yeast artificial chromosomes using PCR and BAC-end sequencing. The marker content of individual clones was determined by gene and BAC-end specific PCR, and the location of genes and BAC-ends was confirmed analyzing somatic hybrid cells. A comparative analysis indicated that the content and order of MHC class III genes is strongly conserved between cattle and other mammalian species. Fluorescence in situ hybridization localized the bovine class III region to BTA23q21-->q22. The results show that the collection of sequenced BAC-ends is a powerful resource for generating high-resolution comparative chromosome maps.

No associations of human pulmonary tuberculosis with Sp110 variants.

BACKGROUND: After a recent report on the role of the Ipr1 gene in mediating innate immunity in a mouse model of Mycobacterium tuberculosis infection, the human Ipr1 homologue, Sp110, was considered a promising candidate for an association study in human tuberculosis. METHODS: In a sample of >1000 sputum positive, HIV negative West African patients with pulmonary tuberculosis and >1000 exposed, apparently healthy controls, we have genotyped 21 Sp110 gene variants that were either available from public databases, including HapMap data, or identified by DNA re-sequencing. RESULTS: No significant differences in the frequencies of any of the 21 variants were observed between patients and controls. This applied also for HapMap tagging variants and the corresponding haplotypes, when including sliding window analyses with three adjacent variants, and when stratifying controls for positivity and negativity according to the results of intradermal tuberculin (purified protein derivative, PPD) skin tests. DNA re-sequencing revealed 13 novel Sp110 variants in the 5'-UTR, exons, and adjacent intronic regions. CONCLUSIONS: Based on the results obtained in this case-control study, the hypothesis that Sp110 variants and haplotypes might be associated with distinct phenotypes of human M tuberculosis infection is doubtful.

Pre-treatment with chloroquine and parasite chloroquine resistance in Ghanaian children with severe malaria.

BACKGROUND: Self-medication with anti-malarial drugs is widespread, and chloroquine (CQ) resistance is increasing. The effect of these factors on the incidence and presentation of severe malaria is uncertain. AIM: To investigate subtype of severe malaria, duration of illness, previous CQ treatment and prevalence of Plasmodium falciparum CQ-resistance markers among children presenting with severe malaria to a teaching hospital in Ghana. DESIGN: Prospective clinical study. METHODS: Consecutive patients (n = 189) presenting with severe malaria were examined clinically, and blood was taken for routine haematology and malaria films. Plasma and blood cells were stored and subsequently analysed by ELISA for CQ levels (n = 168) and by PCR and restriction digest for P. falciparum chloroquine resistance transporter gene (pfcrt) mutations (n = 139). RESULTS: Of 47 presenting with cerebral malaria, 21 had severe anaemia and 13 respiratory distress (RDS). Twenty-nine had prostration or RDS alone, 41 severe anaemia with prostration or RDS, and 72 severe anaemia not associated with coma, prostration or RDS. Of the patients studied, 77% had CQ in their plasma, and 88% were carrying P. falciparum with a CQ-resistance genotype. Significant associations were found (i) between the CQ-resistance genotype of parasites and plasma CQ levels, (ii) between the presence of CQ in plasma and the reported duration of illness, and (iii) between the reported duration of illness and the occurrence of severe but otherwise uncomplicated anaemia. DISCUSSION: There was extensive prior CQ use in our patients presenting with severe malaria, and a high prevalence of parasites with the CQ-resistance genotype. CQ resistance in P. falciparum may contribute to the development of severe but otherwise uncomplicated anaemia in this setting.

Relevance of ex vivo blood lymphocyte assay for in vivo lymphocyte function.

Determinations of in vitro proliferative and secretory activities of peripheral blood cells are used widely for research in clinical immunology but, to our knowledge, have not been evaluated as to their power to reflect in vivo activities quantitatively. Here, we addressed this question by quantitatively correlating the in vitro secretion of interleukin (IL)-5 by peripheral blood cells to the in vivo activity of IL-5 as reflected by peripheral-blood eosinophil counts. Studying 458 humans exposed to transmission of the nematode Onchocerca volvulus, IL-5 was measured in the supernatants of 0.02-ml whole-blood cells cultured in the presence of O. volvulus extract or mitogen. O. volvulus-reactive IL-5 secretion was correlated significantly to blood eosinophilia in a quantitative manner explaining 15.1% (95% CI 8.3-19.9%) of the variability of eosinophil counts. Interestingly, correlations were obtained only if parasite counts were included in the calculation using multiple regression analysis. The results show that in vitro assays of minute amounts of blood lymphocytes may quantitatively reflect activities of the entire lymphocyte population in vivo.

The species Mycobacterium africanum in the light of new molecular markers.

The findings of recent studies addressing the molecular characteristics of Mycobacterium tuberculosis complex isolates have initiated a discussion on the classification of M. africanum, especially of those isolates originating from East Africa (cluster F, subtype II) and displaying phenotypic and biochemical characteristics more similar to those of M. tuberculosis. To further address this question, we analyzed a representative collection of 63 M. tuberculosis complex strains comprising 30 M. africanum subtype I strains, 20 M. africanum subtype II strains, 10 randomly chosen M. tuberculosis isolates, and type strains of M. tuberculosis, M. bovis, and M. africanum for the following biochemical and molecular characteristics: single-nucleotide polymorphisms (SNPs) in gyrB and narGHJI and the presence or absence of RD1, RD9, and RD12. For all molecular markers analyzed, subtype II strains were identical to the M. tuberculosis strains tested. In contrast, the subtype I strains as well as the M. africanum type strain showed unique combinations of SNPs in gyrB and genomic deletions (the absence of RD9 and the presence of RD12), which proves their independence from M. tuberculosis and M. bovis. Accordingly, all subtype I strains displayed main biochemical characteristics included in the original species description of M. africanum. We conclude that the isolates from West Africa were proved to be M. africanum with respect to the phenotypic and genetic markers analyzed, while the isolates from East Africa must be regarded as phenotypic variants of M. tuberculosis (genotype Uganda). We propose the addition of the molecular characteristics defined here to the species description of M. africanum, which will allow clearer species differentiation in the future.

High mortality of infant bacteraemia clinically indistinguishable from severe malaria.

BACKGROUND: Early recognition of children at highest risk of dying and the targeting of appropriate drug therapy are vital to the improvement of paediatric care in developing countries. This will rely upon the development of simple clinically-based algorithms and treatment guidelines. AIM: To determine the role of bacteraemia in children presenting with clinical signs and symptoms of severe malaria. DESIGN: Retrospective analysis of blood culture results following prospective data collection. METHODS: We studied 251 children presenting with symptoms and signs of severe malaria to a tertiary referral centre in Ghana. Blood was taken for malaria blood films, bacterial culture and haemograms. RESULTS: On the basis of clinical signs alone, malaria-film-positive (n = 182) and -negative (n = 69) patients were indistinguishable. Some 40% of film-negative patients were bacteraemic, vs. 12% of film-positive patients. Severe malaria and bacteraemia were not positively associated. Film-negative bacteraemic patients had a mortality of 39%, primarily affecting the age group <30 months. DISCUSSION: Infants presenting with symptoms and signs of severe malaria but a negative malaria film require immediate antibiotic treatment.

Promoter haplotypes of the interleukin-10 gene influence proliferation of peripheral blood cells in response to helminth antigen.

Since interleukin (IL)-10 is a key mediator of immunosuppression, and immunosuppression is considered an important element of helminth infection, we studied variants of the putative IL-10 gene promoter in 337 individuals from 130 families heavily exposed to infection by the tissue nematode Onchocerca volvulus. As shown by transmission disequilibrium tests, variants of the IL-10 promoter at positions -1082(G/A), -819(C/T), and -592(C/A) in the haplotype of ATA were significantly associated with high peripheral blood cell (PBC) proliferative responses to O. volvulus antigen (OvAg). No associations were observed using phytohemagglutinin-induced PBC proliferation or with qualitative or quantitative phenotypes of onchocerciasis or onchocerciasis-related skin disease. The findings are compatible with the hypothesis that the ATA haplotype causes a decrease in IL-10 production by OvAg-reactive type-1 regulatory T-lymphocytes, thereby alleviating the suppression of other T cells. To our knowledge, this is the first time that an influence of IL-10 promoter variants is shown on the adaptive immune response.

[Genetics of susceptibility and resistance to tuberculosis]. / Genetik der Empfänglichkeit und Resistenz gegenüber Tuberkulose.

As shown in twin studies, the inherited predisposition plays an important role in tuberculosis. Genetic influences may be specified in two ways. First, variants of genes whose products are involved in apparently disease-relevant pathways may be tested in population-based studies. Applying this approach, associations with pulmonary tuberculosis have been reported for variants of the genes encoding mannose-binding protein, the vitamin-D receptor, natural-resistance associated macrophage protein 1, interferon-gamma, of HLA alleles and of the interleukin-1 gene cluster. Second, genetic influences can be identified by genome-wide studies of members of affected families. Thus, linkage has been found between pulmonary tuberculosis and as yet undefined genetic variants on chromosome 15q and the X chromosome. Further genomic regions of interest have been identified in mouse models.

Cutaneous pathology in onchocerciasis associated with pronounced systemic T-helper 2-type responses to Onchocerca volvulus.

BACKGROUND: Of 18 million people world-wide who are infested with the tissue nematode Onchocerca volvulus, more than 30% are considered to have skin lesions, the pathomechanisms of which are poorly understood. OBJECTIVES: To relate skin changes associated with onchocerciasis to parasitological findings and systemic cellular immune responses. METHODS: In the course of a genetic study, 691 members of 241 families exposed to hyperendemic O. volvulus transmission and free of other filarial or schistosomal infestations were studied clinically, by counting palpable Onchocerca nodules and skin microfilariae, by measuring peripheral blood cell (PBC) counts and total serum IgE, and by determining PBC in vitro proliferation and cytokine secretion in response to O. volvulus antigen. RESULTS: Of 691 individuals studied, 219 presented with onchocerciasis-associated skin changes. The groups of individuals with and without skin lesions neither differed in prevalences nor in average numbers of microfilariae. Compared with individuals without skin lesions, pronounced systemic T-helper (Th) 2-type responses were found with a trend of increasing intensity in the order of depigmentation, papular dermatitis, atrophy and lichenified dermatitis. Differences between the groups were most pronounced for serum IgE, less so for eosinophilia, and relatively weak for PBC proliferation and interleukin-5 secretion. CONCLUSIONS: Skin lesions in onchocerciasis are associated with a spectrum of increasing generalized Th2-type responses ranging from low reactivities in cases of depigmentation alone to strong reactivities in cases of lichenification.

Variability of the CD36 gene in West Africa.

Studying 12 selected individuals from a malaria-endemic area in West Africa, 24 variants of the CD36 gene were found, 21 of them novel ones. These included three single-nucleotide substitutions causing non-conservative amino acid exchanges E123K, T174A, and I271T as well as a three base pair (bp) insertion resulting in the addition of an asparagine residue (N232-233ins). The E123K variant was located within the putative ligand-binding domain for oxidized low density lipoprotein, while the other substitutions resided outside any of the binding sites for reaction partners mapped on CD36 so far. Twelve single-nucleotide polymorphisms (SNPs) were identified in untranslated parts of the exons and in introns. Five additional SNPs were located in the promoter region whereby -144G-->T, -53G-->T, and -2A-->G alter putative binding sites for the transcription factors purine factor (PuF), phorbol ester-responsive element AP-2, and CCAAT/enhancer-binding protein. A G-->T exchange at position -50 appears to introduce a new recognition site for PuF. Calculations of nucleotide diversity revealed extraordinarily high numbers for all parts of the gene, which may, however, to some extent be due to the selection of individuals studied.

Pattern of connexin 26 (GJB2) mutations causing sensorineural hearing impairment in Ghana.

Mutations of the connexin 26 gene (GJB2) were studied in 365 apparently unrelated individuals with profound nonsyndromic, sensorineural hearing impairment from Ghana, West Africa. Among 121 mutated chromosomes found, 110 carried the previously described R143W mutation. A total of 6 novel mutations: L79P, V178A, R184Q, A197S, I203K, and L214P, were identified, whereby I203K was based on a dinucleotide exchange and R184Q appeared to be dominant. The GJB2 variants found in Ghana tend to comprise less nonsense and frameshift mutations and more mutations located in the C-terminal half of the molecule than the variants found in other parts of the world.

Two novel mutations R653H and E230K in the Mediterranean fever gene associated with disease.

Familial Mediterranean fever (FMF) is an autosomal recessive disorder caused by mutations in the Mediterranean fever gene (MEFV). We describe two novel missense mutations in MEFV, R653H and E230K. Both were found in compound heterozygosity with the mutation M694V in single Turkish patients with clinical syndromes characteristic for FMF. DNA sequencing and PCR-RFLP typing of the families confirmed the mutations and verified recessive modes of inheritance.

Malariometric update for the rainforest and savanna of Ashanti region, Ghana.

The epidemiological features of human infection with Plasmodium were studied in a community-based survey of 35 villages in the Ashanti region of Ghana. The overall prevalences of malarial parasitaemia in subjects aged > or = 2 years were 50.72% in forest areas and 49.72% in savanna. Plasmodium falciparum was the predominant species everywhere, followed by P. malariae in the savanna and P. ovale in the forest. The highest prevalence of asexual parasitaemia (of any species) occurred in the youngest age-group (2-9 years). The geometric mean intensities of parasitaemia among the parasitaemic (i.e. the parasite density indices) were 557, 640 and 452 parasites/microliter for P. falciparum, P. ovale and P. malariae, respectively. For each Plasmodium species encountered, the mean intensity of parasitaemia decreased with age. Mixed infections were observed in 24% and 30% of the parasitaemic subjects from the forest and savanna, respectively. Those infected with P. falciparum were more likely to carry P. ovale (odds ratio = 2.02) or P. malariae (odds ratio = 2.63) than those who were not infected with P. falciparum. Mean intensities of the parasitaemias in mixed infections were substantially higher than the sums of those in the corresponding single infections. When comparing villages, parasite density indices were found to be correlated with the prevalences of parasitaemia (r = 0.56).

Delayed-type hypersensitivity reactions to Onchocerca volvulus antigens in exposed and non-exposed African individuals.

Although considered of critical importance, the mode of helper T-lymphocyte function in Onchocerca volvulus infection is still unclear including the role of the Th1/Th2 dichotomy. We studied the delayed-type hypersensitivity (DTH) reaction, which is the classical Th1 response, to O. volvulus antigens in Africans exposed and not exposed to the infection. DTH reactions were found in a small percentage of patients with generalized onchocerciasis, but in a high percentage of patients with localized onchocerciasis, in putatively immune subjects, and also in non-exposed individuals, which may be due to cross-reactivity with other nematodes. These findings support the notions of (i) prenatal influence of maternal O. volvulus infection preventing development of Th1 responses and/or (ii) suppression of Th1 responses by the infection itself.

Physical assignment of the bovine MHC class IIa and class IIb genes.

Screening of a bovine yeast artificial chromosome (YAC) library revealed two clones which contain most of the class II genes of the major histocompatibility complex (MHC) known to date. The YACs were mapped by fluorescence in situ hybridization (FISH) and characterized for the class II genes they contain. We found that the classic class II genes BoLA- DQA, -DQB, -DRA, and -DRB3 are located at BTA 23q21 and the non-classic class II genes DYA, DIB, LMP2, LMP7, TAP2, BoLA-DOB, -DMA, -DMB, and -DNA are located at BTA 23q12-->q13. These two different mapping locations confirm and extend previous findings of a gross physical distance between classic and non-classic MHC class II genes in cattle.

Evidence for an additional cattle DQB locus.

Studying the genetic polymorphism of the major histocompatibility complex class II genes in cattle, we identified a sequence (KUH1) which resembles those encoding class II beta chains. The gene was shown to be transcribed in peripheral blood leukocytes. Sequence comparisons, Southern blot, and phylogenetic analyses indicate that (1) KUH1 represents a distinct DQB locus, which we propose to designate BoLA-DQB5, (2) DQB5 constitutes an ancient DQB locus which diverged from a common ancestor gene prior to the duplication resulting in DQB1 and DQB2, (3) DQB5 is associated with haplotypes which contain DQA5 and a duplicated DQ region.

Evidence for an additional cattle DQA locus, BoLA-DQA5.

Studying the genetic polymorphism of the major histocompatibility complex class II genes in cattle, we identified an allele (BNI13) which encodes a typical class II alpha chain. Its transcription was confirmed by RNA analysis. Sequence comparisons, Southern blot, and phylogenetic analyses indicate that (1) BNI13 represents a distinct DQA locus which we propose to designate BoLA-DQA5, (2) BoLA-DQA1 and BoLA-DQA5 separated after the divergence of BoLA-DQA1 and BoLA-DQA2, but prior to the separation of sheep DQA1 and cattle DQA1, and (3) DQA5 is distributed among various cattle breeds but is confined to certain haplotypes.