MCP1 haplotypes associated with protection from pulmonary tuberculosis

<p>Abstract</p> <p>Background</p> <p>The monocyte chemoattractant protein 1 (MCP-1) is involved in the recruitment of lymphocytes and monocytes and their migration to sites of injury and cellular immune reactions. In a Ghanaian tuberculosis (TB) case-control study group, associations of the <it>MCP1 </it>-362C and the <it>MCP1 </it>-2581G alleles with resistance to TB were recently described. The latter association was in contrast to genetic effects previously described in study groups originating from Mexico, Korea, Peru and Zambia. This inconsistency prompted us to further investigate the <it>MCP1 </it>gene in order to determine causal variants or haplotypes genetically and functionally.</p> <p>Results</p> <p>A 14 base-pair deletion in the first <it>MCP1 </it>intron, int1del554-567, was strongly associated with protection against pulmonary TB (OR = 0.84, CI 0.77-0.92, P_corrected= 0.00098). Compared to the wildtype combination, a haplotype comprising the -2581G and -362C promoter variants and the intronic deletion conferred an even stronger protection than did the -362C variant alone (OR = 0.78, CI 0.69-0.87, P_nominal= 0.00002; adjusted P_global= 0.0028). In a luciferase reporter gene assay, a significant reduction of luciferase gene expression was observed in the two constructs carrying the <it>MCP1 </it>mutations -2581 A or G plus the combination -362C and int1del554-567 compared to the wildtype haplotype (P = 0.02 and P = 0.006). The associated variants, in particular the haplotypes composed of these latter variants, result in decreased MCP-1 expression and a decreased risk of pulmonary TB.</p> <p>Conclusions</p> <p>In addition to the results of the previous study of the Ghanaian TB case-control sample, we have now identified the haplotype combination -2581G/-362C/int1del554-567 that mediates considerably stronger protection than does the <it>MCP1 </it>-362C allele alone (OR = 0.78, CI 0.69-0.87 vs OR = 0.83, CI 0.76-0.91). Our findings in both the genetic analysis and the reporter gene study further indicate a largely negligible role of the variant at position -2581 in the Ghanaian population studied.</p

Autophagy Gene Variant IRGM −261T Contributes to Protection from Tuberculosis Caused by Mycobacterium tuberculosis but Not by M. africanum Strains

The human immunity-related GTPase M (IRGM) has been shown to be critically involved in regulating autophagy as a means of disposing cytosolic cellular structures and of reducing the growth of intracellular pathogens in vitro. This includes Mycobacterium tuberculosis, which is in agreement with findings indicating that M. tuberculosis translocates from the phagolysosome into the cytosol of infected cells, where it becomes exposed to autophagy. To test whether IRGM plays a role in human infection, we studied IRGM gene variants in 2010 patients with pulmonary tuberculosis (TB) and 2346 unaffected controls. Mycobacterial clades were classified by spoligotyping, IS6110 fingerprinting and genotyping of the pks1/15 deletion. The IRGM genotype −261TT was negatively associated with TB caused by M. tuberculosis (OR 0.66, CI 0.52–0.84, Pnominal 0.0009, Pcorrected 0.0045) and not with TB caused by M. africanum or M. bovis (OR 0.95, CI 0.70–1.30. P 0.8). Further stratification for mycobacterial clades revealed that the protective effect applied only to M. tuberculosis strains with a damaged pks1/15 gene which is characteristic for the Euro-American (EUAM) subgroup of M. tuberculosis (OR 0.63, CI 0.49–0.81, Pnominal 0.0004, Pcorrected 0.0019). Our results, including those of luciferase reporter gene assays with the IRGM variants −261C and −261T, suggest a role for IRGM and autophagy in protection of humans against natural infection with M. tuberculosis EUAM clades. Moreover, they support in vitro findings indicating that TB lineages capable of producing a distinct mycobacterial phenolic glycolipid that occurs exclusively in strains with an intact pks1/15 gene inhibit innate immune responses in which IRGM contributes to the control of autophagy. Finally, they raise the possibility that the increased frequency of the IRGM −261TT genotype may have contributed to the establishment of M. africanum as a pathogen in the West African population

Variant G57E of Mannose Binding Lectin Associated with Protection against Tuberculosis Caused by Mycobacterium africanum but not by M. tuberculosis

Structural variants of the Mannose Binding Lectin (MBL) cause quantitative and qualitative functional deficiencies, which are associated with various patterns of susceptibility to infectious diseases and other disorders. We determined genetic MBL variants in 2010 Ghanaian patients with pulmonary tuberculosis (TB) and 2346 controls and characterized the mycobacterial isolates of the patients. Assuming a recessive mode of inheritance, we found a protective association between TB and the MBL2 G57E variant (odds ratio 0.60, confidence interval 0.4–0.9, P 0.008) and the corresponding LYQC haplotype (Pcorrected 0.007) which applied, however, only to TB caused by M. africanum but not to TB caused by M. tuberculosis. In vitro, M. africanum isolates bound recombinant human MBL more efficiently than did isolates of M. tuberculosis. We conclude that MBL binding may facilitate the uptake of M. africanum by macrophages, thereby promoting infection and that selection by TB may have favoured the spread of functional MBL deficiencies in regions endemic for M. africanum

Association of gene variants of the 5q31-33 chromosomal region with the incidence of malaria and anemia in children from Ghana

In dieser Arbeit wurde die Genregion 5q31-33 auf Assoziationen mit der Inzidenz von Malaria und Anämie bei Kindern aus Ghana untersucht. Als Kandidaten wurden Einzelmutationen der Gene Interleukin 4 (IL4), Interleukin 13 (IL13) und des Gens des beta2-adrenergen Rezeptors ADRB2 (ADRB2) ausgewählt.Eine in vorherigen Studien bereits beschriebene negative Assoziation einer Einzelmutationen an Position -1112 der IL13-Promotorregion mit dem Auftreten schwerer Anämien im Verlauf von Malaria wurde teilweise repliziert. Ein Thymin an dieser Position ist auch in dieser Studie tendenziell mit einem Schutz vor moderaten Anämien verbunden, allerdings haben die Träger dieser Genvariante gleichzeitig ein im Vergleich zum Wildtyp erhöhtes Risiko für das Auftreten von Plasmodium-falciparum-Parasitämien. Diese konträren Beobachtungen lassen sich möglicherweise durch eine gesteigerte Hämatopoese erklären. So ist vorstellbar, dass die bei Trägern der Genvariante IL13-1112T im Vergleich zum Wildtyp häufigeren Parasitämien eine kompensatorische Steigerung der Hämatopoese zur Folge haben, wodurch sich wiederum ein Schutz vor dem Auftreten schwerer Anämien erklären ließe.Weiterhin wurden Assoziationen mehrerer unabhängiger Einzelvarianten der ADRB2-Promotor- und 3'-UTR-Region mit dem Auftreten von Malaria-Episoden nachgewiesen. Möglicherweise wird durch diese Varianten die Expression des ADRB2-Gens und damit die Dichte von beta2-adrenergen Rezeptoren auf Erythrozyten beeinflusst. Dies könnte bei der Kontrolle von P.-falciparum-Infektionen und der Entstehung der Malaria eine Rolle spielen, da die Parasiten bei der Invasion der Erythrozyten funktionelle Teile des ADRB2-Rezeptors nutzen.Somit wurden mehrere genetische Assoziationen identifiziert, die unabhängig voneinander Einfluss auf den Verlauf einer Malaria nehmen können.Während im Falle der Promotor-Variante an Position -1112 des IL13-Gens eine bereits bekannte genetische Assoziation nicht eindeutig repliziert werden konnte, wirft der genaue Zusammenhang zwischen den beiden beobachteten Effekten, Schutz vor Anämie, aber gleichzeitig das erhöhte Risiko einer Parasitämie, noch Fragen auf, die in dieser Arbeit nicht abschließend beantwortet werden konnten und durch funktionelle Untersuchungen geklärt werden sollten. Im Falle des ADRB2-Gens wird ein bereits an Mäusen in vivo beschriebener Mechanismus auf der Ebene der genetischen Assoziationsuntersuchung am Menschen bestätigt

Genotyping of IRGM tetranucleotide promoter oligorepeats by fluorescence resonance energy transfer

Fluorescence resonance energy transfer (FRET) genotyping has been well established for the rapid assessment of single nucleotide polymorphisms (SNPs) and deletions. A design is presented that allows the typing of short tandem oligo repeat sequences using the LightTyper/LightCycler system. The protocol was evaluated and applied to the typing of a tetranucleotide promoter repeat of the human gene encoding the immunity-related GTPase family, M (IRGM) molecule in >2000 individuals from Ghana, West Africa