Chlamydia trachomatis is an obligate intracellular bacterial pathogen that infects hundreds of millions of individuals globally, causing blinding trachoma and sexually transmitted disease. More effective chlamydial control measures are needed, but progress toward this end has been severely hampered by the lack of a tenable chlamydial genetic system. Here, we describe a reversegenetic approach to create isogenic C. trachomatis mutants. C. trachomatis was subjected to low-level ethyl methanesulfonate mutagenesis to generate chlamydiae that contained less then one mutation per genome. Mutagenized organisms were expanded in small subpopulations that were screened for mutations by digesting denatured and reannealed PCR amplicons of the target gene with the mismatch specific endonuclease CEL I. Subpopulations with mutations were then sequenced for the target region and plaque-cloned if the desired mutation was detected. We demonstrate the utility of this approach by isolating a tryptophan synthase gene (trpB) null mutant that was otherwise isogenic to its parental clone as shown by de novo genome sequencing. The mutant was incapable of avoiding the anti-microbial effect of IFN-γ-induced tryptophan starvation. The ability to genetically manipulate chlamydiae is a major advancement that will enhance our understanding of chlamydial pathogenesis and accelerate the development of new anti-chlamydial therapeutic control measures. Additionally, this strategy could be applied to other medically important bacterial pathogens with no or difficult genetic systems.genetics | mutation screen

The prevalence of human cytomegalovirus (HCMV) pp65-, pp150-, IE1-exon4-, gB- and pp28-specific cytotoxic T lymphocyte (CTL) responses was compared among 34 healthy individuals, grouped by neutralizing antibody titers. Moderately and highly seropositive donors showed predominantly pp65- and IE1-exon4-specific CTL responses (92% and 76% of the donors, respectively), with similar precursor frequencies in the 2 donors tested. In addition, highly seropositive and a few moderately seropositive donors showed CTL responses to gB and pp150 (33% and 30% of the donors, respectively). No individual recognized pp28 as a target in the CTL assay. Phenotypic analysis revealed a mixed effector population of CD4+ and CD8+ (1 donor) or only CD8+ cells for pp65-specific effectors (2 donors). IE1-exon4- and pp150-specific effectors were CD8+ (2 donors and 1 donor, respectively), whereas gB-specific CTLs were CD4+ (1 donor). These data may help to design a cellular immunity-based vaccine effective against HCMV diseases.

Background-Studies have suggested that the prevalence of antibodies against heat-shock proteins (HSPs), Chlamydia pneumoniae (Cpn), and cytomegalovirus (CMV) is associated with coronary artery disease (CAD), but the independent or joint effects of human (h) HSP60 antibodies and these pathogens in patients have not been fully elucidated. Methods and Results-A total of 405 subjects (276 patients with CAD and 129 control individuals) were tested for serum antibodies to hHSP60, Cpn, and CMV immediate-early-1 (IE1) antigens. Patients were also assessed for serum cholesterol, triglyceride levels, and smoking habit. Significantly elevated levels of antibodies to hHSP60 and Cpn but not to CMV-IE1 antigens were documented in CAD patients. Multiple logistic regression analysis and subanalyses of selected subjects showed that these associations were independent of age, sex, smoking, and serum lipid levels. Antibodies to hHSP60 and Cpn did not correlate quantitatively; however, the relative risk of disease development was substantially increased in subjects with high antibody levels to both hHSP60 and Cpn, reaching an odds ratio of 82.0 (95% CI 10.6 to 625.0). Conclusions-High levels of antibodies to hHSP60 and Cpn are independent risk factors for coronary atherosclerosis, but their simultaneous presence substantially increases the risk for disease development.

Background-The possible association between coronary artery disease (CAD) and Chlamydia pneumoniae (C pneumoniae) infection is controversial. On the basis of the recent suggestion that mannose-binding lectin (MBL) variant alleles are related to an increased risk of severe atherosclerosis, and on the in vitro interaction of MBL with C pneumoniae, we asked whether MBL might contribute to CAD in conjunction with C pneumoniae. Methods and Results-Antibodies to C pneumoniae were measured by immunofluorescence and MBL alleles were determined by polymerase chain reaction technique in samples from 210 patients with CAD and 257 healthy subjects from Hungary collected between 1995 and 1996. A higher percentage of patients with CAD were anti-C pneumoniae positive as compared with the control group (Pϭ0.058). However, at logistic regression analysis adjusted to age, sex, and serum lipid levels, this difference was confined only to subjects carrying MBL variant alleles (Pϭ0.035, odds ratio 2.63, [95% CI: 1.07 to 6.45]). In contrast, no significant difference was seen in those homozygous for the normal MBL allele (Pϭ0.412). During a 65Ϯ5.8-month follow-up period, major outcomes (new myocardial infarction, and/or bypass operation or cardiovascular death) occurred in 11 C pneumoniae positive and 3 C pneumoniae negative patients. In the C pneumoniae positive group, the odds ratio of development of outcomes was 3.27 (95% CI: 1.10 to 9.71, Pϭ0.033) in the carriers of the MBL variant alleles compared with the homozygous carriers of the normal MBL allele. Conclusions-These results indicate that infection with C pneumoniae leads mainly to the development and progression of severe CAD in patients with variation in the MBL gene.

Background and Purpose-Mannose-binding lectin (MBL) is thought to influence the pathophysiology of cardiovascular disease by decreasing the risk of advanced atherosclerosis and by contributing to enhanced ischemia reperfusion injury. Thus, we investigated the role of MBL in restenosis after eversion endarterectomy in patients with severe carotid atherosclerosis. Methods-In a prospective study, 123 patients who underwent carotid endarterectomy were followed-up by carotid duplex scan (CDS) sonography for 14 months. In a retrospective study, we examined 17 patients and 29 patients, respectively, who had or had not at least 50% restenosis 29 months after carotid eversion endarterectomy. MBL genotypes were analyzed by a polymerase chain reaction-based method, and MBL serum concentrations were measured. Results-In the prospective study in the patients homozygous for the normal MBL genotype, CDS values were significantly higher after 14 months of follow-up compared with the values measured 6 weeks after surgery (PϽ0.001).In contrast, only a slight increase was registered in patients carrying MBL variant alleles. The differences were much more pronounced in female than in male patients. Similar differences were observed when patients with high and low MBL serum concentrations were compared. In the retrospective study, a significant increase in the frequency of MBL variant genotypes was observed in patients not experiencing restenosis compared with the patients with restenosis (Pϭ0.007). Conclusions-These

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