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BACKGROUND: In recent years an increase of the incidence of nosocomial outbreaks caused by noroviruses has been observed throughout Sweden, with high peaks noted in the winter seasons 2002/2003 and ...

Background Viral diarrhea remains a major cause of childhood morbidity and mortality worldwide. Although rotavirus was extensively studied in China, few comprehensive studies of all viral agents related to diarrhea in children have been conducted. Objectives Our study was performed to investigate the role of enteric viruses in acute diarrhea in our country and to evaluate methods that could be used in routine diagnostics. Study design One hundred stool samples were collected from children under 5 years of age seeking medical care for acute diarrhea during the winter season 2000/2001 in Beijing Children's Hospital. All specimens were initially screened microscopically for leucocytes/red blood cells. Samples with negative results were analyzed for virus presence using commercial EIAs and/or in-house RT-PCRs. Results At least one viral agent was found in 67% of the specimens. The frequency of rotavirus, astrovirus, norovirus and enteric adenovirus was 59%, 8%, 6% and 2%, respectively. Dual infections were found in 9.0% (6/67) of the positive samples. The results from rotavirus and astrovirus EIAs were concordant with those of rotavirus and astrovirus RT-PCRs. Conclusions Enteric viruses play an important role in pediatric diarrhea during the winter season in China. A combination of microscopic examination of stool samples with specific EIA assays to detect virus antigen in stool specimens may be suitable for routine diagnostics.

The mucosal immune system identifies and fights invading pathogens, while allowing non-pathogenic organisms to persist. Mechanisms of pathogen/non-pathogen discrimination are poorly understood, as is the contribution of human genetic variation in disease susceptibility. We describe here a new, IRF3-dependent signaling pathway that is critical for distinguishing pathogens from normal flora at the mucosal barrier. Following uropathogenic E. coli infection, Irf3−/− mice showed a pathogen-specific increase in acute mortality, bacterial burden, abscess formation and renal damage compared to wild type mice. TLR4 signaling was initiated after ceramide release from glycosphingolipid receptors, through TRAM, CREB, Fos and Jun phosphorylation and p38 MAPK-dependent mechanisms, resulting in nuclear translocation of IRF3 and activation of IRF3/IFNβ-dependent antibacterial effector mechanisms. This TLR4/IRF3 pathway of pathogen discrimination was activated by ceramide and by P-fimbriated E. coli, which use ceramide-anchored glycosphingolipid receptors. Relevance of this pathway for human disease was supported by polymorphic IRF3 promoter sequences, differing between children with severe, symptomatic kidney infection and children who were asymptomatic bacterial carriers. IRF3 promoter activity was reduced by the disease-associated genotype, consistent with the pathology in Irf3−/− mice. Host susceptibility to common infections like UTI may thus be strongly influenced by single gene modifications affecting the innate immune response., Author Summary The host immune system must identify pathogens and defeat them through TLR-dependent signaling pathway activation, while distinguishing them from commensal flora. Contrary to current dogma, the host cannot solely use “pattern recognition” since the microbial molecules involved in such recognition are present on pathogens and commensals alike. We identify here a pathogen-specific mechanism of TLR4 activation and signaling intermediates in this pathway, leading to IRF3-dependent transcription of innate immune response genes. We show in knockout mice that Irf3 deficiency causes severe tissue pathology and that effector functions controlled by IFNβ are involved. Finally, in highly disease-prone pyelonephritis patients we found a high frequency of IRF3 promoter polymorphism compared to asymptomatic bacterial carriers or controls. The polymorphisms influenced promoter activity in reporter assays, suggesting that they are functionally important. Urinary tract infections are among the most common bacterial infections in man, and are a major cause of morbidity and mortality. A subset of disease-prone individuals is at risk for recurrent disease, severe renal dysfunction and end-stage renal disease. At present, there is no method to identify disease-prone infants and to prevent future morbidity and renal damage. The genetic and functional studies described here indicate that genetic variation in IRF3 influences individual susceptibility to kidney infection and might serve as a new tool for future risk assessment in this patient group.

The allergen Can f 2 from dog (Canis familiaris) present in saliva, dander and fur is an important cause of allergic sensitization worldwide. Here, the production, isolation, crystallization and preliminary X-ray diffraction analysis of two crystal forms of recombinant Can f 2 are reported. The first crystal form belonged to space group C222, with unit-cell parameters a = 68.7, b = 77.3, c = 65.1 A, and diffracted to 1.55 A resolution, while the second crystal form belonged to space group C2, with unit-cell parameters a = 75.7, b = 48.3, c = 68.7 A, beta = 126.5 degrees , and diffracted to 2.1 A resolution. Preliminary data analysis indicated the presence of a single molecule in the asymmetric unit for both crystal forms.

In recent years an increase of the incidence of nosocomial outbreaks caused by noroviruses has been observed throughout Sweden, with high peaks noted in the winter seasons 2002/2003 and 2004/2005, respectively.To phylogenetically characterize norovirus strains causing nosocomial outbreaks from 1997 to 2005 and estimate the impact of norovirus-like disease on the Swedish health care system during the peak season 2002/2003 when a new variant of norovirus occurred.Stool samples from 115 randomly selected nosocomial outbreaks occurring during 1997--2005 throughout Sweden were studied by RT-PCR and sequencing. In addition, to investigate the impact on the health-care system, a questionnaire was distributed to infection control units (n=90) serving all Swedish hospitals, nursing homes and other health-care institutions during the largest epidemic of nosocomial outbreaks.Sequencing of 279 nucleotides of the norovirus RNA polymerase gene in stools containing norovirus RNA showed that strains belonging to the GII.4 genotype dominated. Each of the two large epidemics was due to a new variant within this cluster. The questionnaire revealed that 30,000-35,000 episodes of nosocomial norovirus-like infections occurred in 80 of 82 major Swedish hospitals affected in 2002/2003.New norovirus variants within the cluster GGII.4 may have a major impact on the health-care system.

Helicobacter pylori binds a number of host cell proteins, including the plasma protein plasminogen, which is the proenzyme of the serine protease plasmin. Two H. pylori plasminogen-binding proteins have been described; however, no genes were identified. Here we report the use of a phage display library to clone two genes from the H. pylori CCUG 17874 genome that mediate binding to plasminogen. DNA sequence analysis of one of these genes revealed 96.6% homology with H. pylori 26695 HP0508. A subsequent database search revealed that the amino acid sequence of a lysine-rich C-terminal segment of HP0508 is identical to the C terminus of HP0863. Recombinant proteins expressed from HP0508 and HP0863 bound plasminogen specifically and in a lysine-dependent manner. We designate these genes pgbA and pgbB , respectively. These proteins are expressed by a variety of H. pylori strains, have surface-exposed domains, and do not inhibit plasminogen activation. These results indicate that pgbA and pgbB may allow H. pylori to coat its exterior with plasminogen, which subsequently can be activated to plasmin. The surface acquisition of protease activity may enhance the virulence of H. pylori .

A new term 'receptin', derived from recipere (lat.), is proposed to denote microbial binding proteins that interact with mammalian target proteins. An example of such a 'receptin' is staphyloccocal protein A which binds to the Fc part of many mammalian immunoglobulins. Several other types of 'receptins' are listed. This term may easily be distinguished from the similar term 'receptor', describing a binding site on a cell surface, mostly eukaryotic, where a secondary effect is induced inside the cell upon binding to a ligand. A receptin, however, does not necessarily have to induce a secondary event. Receptins include so called MSCRAMMs, adhesins, and also engineered receptins, affibodies, and engineered ligands. It denotes any protein of microbial origin, cell-bound or soluble, which can bind to a mammalian protein. It fulfills the need for an umbrella terminology for a large group of binding structures. In contrast, the term 'lectin' represents a group of proteins with affinity for carbohydrate structures. The new term 'receptin' includes a number of key microbial proteins involved in host-parasite interactions and in virulence. Some receptins are promising vaccine candidates.

Fibronectin is a large glycoprotein (Mr = 420 – 480 k) found in the extracellular matrix and in body fluids. In the monomeric form the glycoprotein is composed of two similar polypeptides linked together at the C-terminal ends by disulfide bonds. In the extracellular matrix fibronectin is found in fibrillar structures which also appear to contain collagens and glycosaminoglycans. Fibronectin can bind directly to collagens and glycosaminoglycans via distinct binding sites. (For reviews on fibronectin structure, see references 1 and 2).

Binding of cells of Staphylococcus aureus to fibronectin, which may represent a mechanism of host tissue adherence, involves a fibronectin-receptor protein present on the bacterial surface. Cloning of a gene coding for a staphylococcal fibronectin-binding protein and construction of a fusion protein with fibronectin-binding properties was previously reported from our laboratory. We have now sequenced the gene and deduced a primary sequence of the fibronectin-binding protein. The protein resembles other cell-wall-associated proteins on Gram-positive bacteria in that it (i) appears to be anchored in the cell membrane via its C-terminal end, (ii) contains a proline-rich repeating unit outside the membrane anchor, and (iii) contains a long (36-amino acid) signal sequence at the N terminus. The fibronectin-binding activity has been localized to a domain composed of a 38-amino acid unit repeated completely three times and partially a fourth time; the identity between the three 38-amino acid sequences varies from 42 to 87%. Three synthetic peptides mimicking the structure of each 38-amino acid unit were constructed. All three peptides interacted with fibronectin, as indicated by their ability to inhibit binding of fibronectin to staphylococcal cells, whereas an unrelated 37-amino acid peptide showed no inhibitory activity.