Design and application of a core genome multilocus sequence typing scheme for investigation of Legionnaires' disease incidents.

Sequence-based typing (SBT) for Legionella pneumophila (Lp) has dramatically improved Legionnaires' disease (LD) cluster investigation. Microbial whole genome sequencing (WGS) is a promising modality for investigation but sequence analysis methods are neither standardised, nor agreed. We sought to develop a WGS-based typing scheme for Lp using de novo assembly and a genome-wide gene-by-gene approach (core genome multilocus sequence typing, cgMLST). We analysed 17 publicly available Lp genomes covering the whole species variation to define a core genome (1,521 gene targets) which was validated using 21 additional published genomes. The genomes of 12 Lp strains implicated in three independent cases of paediatric humidifier-associated LD were subject to cgMLST together with three 'outgroup' strains. cgMLST was able to resolve clustered strains and clearly identify related and unrelated strains. Thus, a cgMLST scheme was readily achievable and provided high-resolution analysis of Lp strains. cgMLST appears to have satisfactory discriminatory power for LD cluster analysis and is advantageous over mapping followed by single nucleotide polymorphism (SNP) calling as it is portable and easier to standardise. cgMLST thus has the potential for becoming a gold standard tool for LD investigation. Humidifiers pose an ongoing risk as vehicles for LD and should be considered in cluster investigation and control efforts.

Loss-of-function mutations within the IL-2 inducible kinase ITK in patients with EBV-associated lymphoproliferative diseases.

The purpose of this study was the appraisal of the clinical and functional consequences of germline mutations within the gene for the IL-2 inducible T-cell kinase, ITK. Among patients with Epstein-Barr virus-driven lymphoproliferative disorders (EBV-LPD), negative for mutations in SH2D1A and XIAP (n=46), we identified two patients with R29H or D500T,F501L,M503X mutations, respectively. Human wild-type (wt) ITK, but none of the mutants, was able to rescue defective calcium flux in murine Itk(-/-) T cells. Pulse-chase experiments showed that ITK mutations lead to varying reductions of protein half-life from 25 to 69% as compared with wt ITK (107 min). The pleckstrin homology domain of wt ITK binds most prominently to phosphatidylinositol monophosphates (PI(3)P, PI(4)P, PI(5)P) and to lesser extend to its double or triple phosphorylated derivates (PIP2, PIP3), interactions which were dramatically reduced in the patient with the ITK(R29H) mutant. ITK mutations are distributed over the entire protein and include missense, nonsense and indel mutations, reminiscent of the situation in its sister kinase in B cells, Bruton's tyrosine kinase.

Array-based sequence capture and next-generation sequencing for the identification of primary immunodeficiencies.

Primary immunodeficiencies are genetic disorders in which components of immunological pathways are either missing or dysregulated. With the advent of next-generation sequencing, testing for genes in conditions with a heterogeneous genetic background seems more promising. We designed a custom microarray with 385K probe capacity to capture exons of 395 human genes, known or predicted to be associated with primary immunodeficiency and immune regulation. Enriched target DNA was sequenced using a GS FLX Titanium 454 platform. The patients selected were likely to have an underlying immunodeficiency. In one patient with hepatosplenomegaly, recurrent infections and an elevated IgM level, sequence analysis of the patient and his two unaffected parents identified ATM (ataxia telangiectasia mutated) as the underlying defect. In a second child with a clinical SCID phenotype, we detected a mutation in the ARTEMIS gene after focusing on SCID-associated genes. 454 sequencing yielded 152,000-397,000 high-quality reads per patient. 78-99% of the targeted nucleotides were covered at least one time, 76-82% at least five times. Array-based sequence capture expands our capacities to sequence large targeted DNA regions in a less laborious and time-consuming approach. Our array was capable to find the underlying genetic defect in two patients with suspected primary immunodeficiency. Upcoming whole-exome sequencing definitely will add more valuable data, but bioinformatical analysis and validation of variants already pose major challenges.

iNKT cell frequency in peripheral blood of Caucasian children and adolescent: the absolute iNKT cell count is stable from birth to adulthood.

Human invariant natural killer T cells (iNKT cells) are a unique population of T cells that express a semi-invariantly rearranged T cell receptor (TCR) and are involved in a variety of immunoregulatory processes. We assessed the frequency of peripheral blood iNKT cells in 64 healthy Caucasian children from 7 months to 18 years of age and five cord blood samples by flow cytometry. iNKT cells were measured as CD3(+) cells co-expressing TCRVα24 and TCRVß11 and using the monoclonal antibody 6B11, which recognizes specifically their invariant TCR rearrangement. The absolute number of iNKT cells ranged from 86 to 10,499 (CD3(+) /TCRVα24(+) / TCRVß11(+)) and 233 to 11,167 (CD3(+) /6B11(+)) iNKT cells per millilitre of blood. This range is stable from birth to adulthood. The relative iNKT cell count was found to be 0.003-0.71% (CD3(+) /TCRVα24/TCRVß11) and 0.019-0.776% (CD3/6B11) of peripheral blood T cells and shows only a slight increase with age.