Determinants of frequent and infrequent STI testing and STI diagnosis related to test frequency among men who have sex with men in the eastern part of the Netherlands: a 6-year retrospective study.

Men who have sex with men (MSM) remain vulnerable to sexually transmitted infections (STIs) and are advised to be tested at least twice a year. The aim of this study was to assess the determinants of test frequency and their associations with an STI diagnosis

Versatile vector suite for the extracytoplasmic production and purification of heterologous His-tagged proteins in Lactococcus lactis

Recent studies have shown that the Gram-positive bacterium Lactococcus lactis can be exploited for the expression of heterologous proteins; however, a versatile set of vectors suitable for inducible extracellular protein production and subsequent purification of the expressed proteins by immobilized metal affinity chromatography was so far lacking. Here we describe three novel vectors that, respectively, facilitate the nisin-inducible production of N- or C-terminally hexa-histidine (His(6))-tagged proteins in L. lactis. One of these vectors also encodes a tobacco etch virus (TEV) protease cleavage site allowing removal of the N-terminal His(6)-tag from expressed proteins. Successful application of the developed vectors for protein expression, purification and/or functional studies is exemplified with six different cell wall-bound or secreted proteins from Staphylococcus aureus. The results show that secretory production of S. aureus proteins is affected by the position, N- or C-terminal, of the His(6)-tag. This seems to be due to an influence of the His(6)-tag on protein stability. Intriguingly, the S. aureus IsdB protein, which is phosphorylated in S. aureus, was also found to be phosphorylated when heterologously produced in L. lactis, albeit not on the same Tyr residue. This implies that this particular post-translational protein modification is to some extent conserved in S. aureus and L. lactis. Altogether, we are confident that the present vector set combined with the L. lactis expression host has the potential to become a very useful tool in optimization of the expression, purification and functional analysis of extracytoplasmic bacterial proteins

Common Scaling Patterns in Intertrade Times of U. S. Stocks

We analyze the sequence of time intervals between consecutive stock trades of thirty companies representing eight sectors of the U. S. economy over a period of four years. For all companies we find that: (i) the probability density function of intertrade times may be fit by a Weibull distribution; (ii) when appropriately rescaled the probability densities of all companies collapse onto a single curve implying a universal functional form; (iii) the intertrade times exhibit power-law correlated behavior within a trading day and a consistently greater degree of correlation over larger time scales, in agreement with the correlation behavior of the absolute price returns for the corresponding company, and (iv) the magnitude series of intertrade time increments is characterized by long-range power-law correlations suggesting the presence of nonlinear features in the trading dynamics, while the sign series is anti-correlated at small scales. Our results suggest that independent of industry sector, market capitalization and average level of trading activity, the series of intertrade times exhibit possibly universal scaling patterns, which may relate to a common mechanism underlying the trading dynamics of diverse companies. Further, our observation of long-range power-law correlations and a parallel with the crossover in the scaling of absolute price returns for each individual stock, support the hypothesis that the dynamics of transaction times may play a role in the process of price formation.Comment: 8 pages, 5 figures. Presented at The Second Nikkei Econophysics Workshop, Tokyo, 11-14 Nov. 2002. A subset appears in "The Application of Econophysics: Proceedings of the Second Nikkei Econophysics Symposium", editor H. Takayasu (Springer-Verlag, Tokyo, 2003) pp.51-57. Submitted to Phys. Rev. E on 25 June 200

Differential epitope recognition in the immunodominant staphylococcal antigen A of Staphylococcus aureus by mouse versus human IgG antibodies

The immunodominant staphylococcal antigen A (IsaA) is a potential target for active or passive immunization against the important human pathogen _Staphylococcus aureus_. Consistent with this view, monoclonal antibodies against IsaA were previously shown to be protective against _S. aureus_ infections in mouse models. Further, patients with the genetic blistering disease epidermolysis bullosa (EB) displayed high IsaA-specific IgG levels that could potentially be protective. Yet, mice actively immunized with IsaA were not protected against _S. aureus_ infection. The present study was aimed at explaining these differences in IsaA-specific immune responses. By epitope mapping, we show that the protective human monoclonal antibody (humAb) 1D9 recognizes a conserved 62-residue N-terminal domain of IsaA. The same region of IsaA is recognized by IgGs in EB patient sera. Further, we show by immunofluorescence microscopy that this N-terminal IsaA domain is exposed on the _S. aureus_ cell surface. In contrast to the humAb 1D9 and IgGs from EB patients, the non-protective IgGs from mice immunized with IsaA were shown to predominantly bind the C-terminal domain of IsaA. Altogether, these observations focus attention on the N-terminal region of IsaA as a potential target for future immunization against _S. aureus_

Low anti-staphylococcal IgG responses in granulomatosis with polyangiitis patients despite long-term Staphylococcus aureus exposure

Chronic nasal carriage of the bacterium Staphylococcus aureus in patients with the autoimmune disease granulomatosis with polyangiitis (GPA) is a risk factor for disease relapse. To date, it was neither known whether GPA patients show similar humoral immune responses to S. aureus as healthy carriers, nor whether specific S. aureus types are associated with GPA. Therefore, this study was aimed at assessing humoral immune responses of GPA patients against S. aureus antigens in relation to the genetic diversity of their nasal S. aureus isolates. A retrospective cohort study was conducted, including 85 GPA patients and 18 healthy controls (HC). Humoral immune responses against S. aureus were investigated by determining serum IgG levels against 59 S. aureus antigens. Unexpectedly, patient sera contained lower anti-staphylococcal IgG levels than sera from HC, regardless of the patients' treatment, while total IgG levels were similar or higher. Furthermore, 210 S. aureus isolates obtained from GPA patients were characterized by different typing approaches. This showed that the S. aureus population of GPA patients is highly diverse and mirrors the general S. aureus population. Our combined findings imply that GPA patients are less capable of mounting a potentially protective antibody response to S. aureus than healthy individuals