Complementarity between targeted real-time specific PCR and conventional broad-range 16S rDNA PCR in the syndrome-driven diagnosis of infectious diseases.

Molecular tools have shown an added value in the diagnosis of infectious diseases, in particular for those caused by fastidious intracellular microorganisms, or in patients receiving antibiotics before sampling. If 16S rDNA amplification had been gradually implemented in microbiology laboratories, specific real-time polymerase chain reaction (PCR) would have permitted an increase in the sensitivity of molecular methods and a reduction of contamination. Herein, we report our experience in the diagnosis of infectious diseases over two years, during which 32,948 clinical samples from 18,056 patients were received from France and abroad. Among these samples, 81,476 PCRs were performed, of which 1,192 were positive. Molecular techniques detected intracellular microorganisms in 31.3 % of respiratory samples, 27.8 % of endocarditis samples and 51.9 % of adenitis samples. Excluding intracellular bacteria, 25 % of the positive samples in this series were sterile in culture. Conventional broad-range PCR permitted the identification of fastidious and anaerobic microorganisms, but specific real-time PCR showed a significant superiority in the diagnosis of osteoarticular infections, in particular for those caused by Kingella kingae and Staphylococcus aureus, and for endocarditis diagnosis, specifically when Streptococcus gallolyticus and Staphylococcus aureus were involved. The sensitivity of conventional broad-range PCR was 62.9 % concerning overall diagnoses for which both techniques had been performed. These findings should lead microbiologists to focus on targeted specific real-time PCR regarding the clinical syndrome. Finally, syndrome-driven diagnosis, which consists of testing a panel of microorganisms commonly involved for each syndrome, permitted the establishment of 31 incidental diagnoses.

Two nucleotides immediately upstream of the essential A6G3 slippery sequence modulate the pattern of G insertions during Sendai virus mRNA editing.

Editing of paramyxovirus P gene mRNAs occurs cotranscriptionally and functions to fuse an alternate downstream open reading frame to the N-terminal half of the P protein. G residues are inserted into a short G run contained within a larger purine run (AnGn) in this process, by a mechanism whereby the transcribing polymerase stutters (i.e., reads the same template cytosine more than once). Although Sendai virus (SeV) and bovine parainfluenza virus type 3 (bPIV3) are closely related, the G insertions in their P mRNAs are distributed differently. SeV predominantly inserts a single G residue within the G run of the sequence 5' AACAAAAAAGGG, whereas bPIV3 inserts one to six G's at roughly equal frequency within the sequence 5' AUUAAAAAAGGGG (differences are underlined). We have examined how the cis-acting editing sequence determines the number of G's inserted, both in a transfected cell system using minigenome analogues and by generating recombinant viruses. We found that the presence of four rather than three G's in the purine run did not affect the distribution of G insertions. However, when the underlined AC of the SeV sequence was replaced by the UU found in bPIV3, the editing phenotype from both the minigenome and the recombinant virus resembled that found in natural bPIV3 infections (i.e., a significant fraction of the mRNAs contained two to six G insertions). The two nucleotides located just upstream of the polypurine tract are thus key determinants of the editing phenotype of these viruses. Moreover, the minimum number of A residues that will promote SeV editing phenotype is six but can be reduced to five when the upstream AC is replaced by UU. A model for how the upstream dinucleotide controls the insertion phenotype is presented.

Split activity of interleukin-10 on antigen capture and antigen presentation by human dendritic cells: definition of a maturative step.

Human CD1+ CD14- dendritic cells (DC) can be derived from CD14+ monocytes using granulocyte/monocyte colony-stimulating factor and interleukin (IL)-4. We have previously shown that IL-10 pre-treatment of such DC significantly inhibited their antigen-presenting capacity to CD4+ T cell clones. In this study, we further analyze how IL-10 influences antigen presentation. We first investigated whether IL-10 could alter the early stage of antigen presentation, the capture of antigen. This can be mediated by mannose receptor (MR)-mediated endocytosis and by fluid-phase uptake through macropinocytosis. IL-10-treated DC showed an enhancement of both mechanisms of antigen capture, as indicated by the increase of fluorescein isothiocyanate-dextran uptake through MR and lucifer yellow uptake. However, IL-10-treated DC, irradiated or glutaraldehyde-fixed, were less efficient than untreated DC in stimulating mixed leukocyte reaction as well as in inducing the activation of peptide-specific T cell clones, indicating that IL-10 achieves its effects mainly by modifying the cell surface phenotype of DC. HLA class I and II, as well as intercellular adhesion molecule (ICAM)-1, lymphocyte function-associated antigen-3, B7-1, B7-2 and ICAM-3 expression were either significantly increased or essentially unchanged, and the ability to bind the epitope recognized by the T cell clones was also unaffected regardless of IL-10 treatment. Our study also indicates that as-yet unidentified accessory molecules may play an essential role in T cell activation. Thus, the IL-10-treated DC possess an increased capacity to capture antigen, with a concomitant decreased stimulatory activity. Our study suggests that IL-10-treated DC have the characteristics of highly immature DC (high capture ability, low stimulatory potency) and may represent an early maturative step of human DC of monocytic origin.