Olaimatu S. Mahdi

The p47 GTPases Iigp2 and Irgb10 Regulate Innate Immunity and Inflammation to Murine Chlamydia psittaci Infection

C57BL/6J mice were 105-fold more resistant to Chlamydia psittaci infection than DBA/2J mice by LD100 determinations. Linkage analysis using BXD recombinant inbred strains revealed a single effector locus at a 1.5-Mbp region on chromosome 11 encoding a cluster of three p47 GTPases (Irgb10, Igtp, and Iigp2). Western blots of infected tissue showed that Irgb10 was elevated in resistant mice and one of the two possible Iigp2 protein isoforms was preferentially expressed in susceptible mice. The BXD39 strain, susceptible at Irgb10 and resistant at Iigp2, had an intermediate phenotype implicating the nonredundant role of these p47 GTPases. C57BL/6J and DBA/2J exhibited a difference in IFN-γ-dependent chlamydial control, which was reversible by Iigp2 small interfering RNA knockdown. Microarrays of infected peritoneal lavage revealed >10-fold up-regulation of neutrophil-recruiting chemokines in susceptible mice and >100-fold increase in macrophage differentiation genes in resistant mice, indicating that the susceptibility pattern involves the stimulation of different inflammatory cell-recruiting pathways. Massive neutrophil recruitment was seen in susceptible mice by histology and flow cytometry, and neutrophil chemokine receptor (CXCR2) knockout mice on a susceptible background survived a lethal challenge, confirming that neutrophil recruitment was required for susceptibility. Congenic Igtp knockout mice also susceptible at Irgb10 and Iigp2 on a resistant background recruited neutrophils and succumbed to infection. We conclude that Irgb10 and Iigp2 act together to confer differential susceptibility against murine chlamydial infection. Data indicate that these p47 GTPases have cell-autonomous effects that result in vastly different inflammatory stimulations, leading to either recovery or death.

Serum Immunoglobulin G Antibodies to Chlamydial Heat Shock Protein 60 but Not to Human and Bacterial Homologs Are Associated With Coronary Artery Disease

Background—Evidence for an association between Chlamydia pneumoniae infection and coronary artery disease (CAD) has been reported by numerous studies, cross-reactive heat shock protein (Hsp) antibody responses have been causally linked to CAD, and the severity of chlamydial disease pathogenesis correlates with Hsp serology. Our aim was to determine if chlamydial Hsp (cHsp) antibody responses are predictive of CAD. Methods and Results—Patients were recruited in a case-control study: 250 cases had angiographically significant CAD (stenosis ≥70%), and 250 controls had normal coronary arteries (stenosis <10%). Serum immunoglobulin G reactivity to Hsp10 and Hsp60 antigens (chlamydial, Escherichia coli, and human), and C pneumoniae whole organisms were measured by ELISA. Univariate analysis confirmed that classical CAD risk factors were predictors of CAD. Univariate analysis showed that cHsp60 (P = 0.001, OR 3.9), cHsp10 (P =0.045, OR 3.8), E coli Hsp60 (P =0.04, OR 1.5) and C pneumoniae (P =0.03, OR 1.8) ELISA optical density (OD) values were significantly different between cases and controls. Multivariate analysis found that only upper-quintile cHsp60 seroreactivity remained a significant predictor of CAD after controlling for classical CAD risk factors and seroreactivity to the other antigens (cHsp60 OD, P =0.005, OR 3.9 per OD unit; cHsp60 quintile, 5 versus 1 to 4;P =0.01, OR 2.1). Conclusions—The presence of elevated anti-cHsp60 immunoglobulin G antibodies, but not anti-human or anti–E coli homologs, was independently associated with CAD. This finding argues against previous suggestions that cross-reactive or autoimmune Hsp60 responses may contribute to disease progression. High anti-cHsp60 antibody response appears to identify the subset of patients with chlamydial infection and significant CAD.

Different Growth Rates of Chlamydia trachomatis Biovars Reflect Pathotype

BACKGROUND Despite small genomic differences, Chlamydia trachomatis biovars exhibit diverse disease manifestations and different growth rates in vivo and in cell culture models. METHODS Chlamydial inclusion-forming units were enumerated over time in HeLa cells, to evaluate the length of the developmental cycle for C. trachomatis strains A, B, C, and E/Bour (ocular strains) as well as D, E/UW5/Cx, F, and L2 (genital strains). Prototype strains A, D, and L2 were selected for detailed analysis of reticulate body growth, division, and genomic replication. The impact that changing host cells and that coinfection with different strains has on growth was also assessed. RESULTS The genital strains completed the developmental cycle in 36-44 h, whereas the ocular strains lagged behind considerably. Differences were the result of a longer lag phase (entry plus differentiation) and generation time for the ocular strains. A prototype ocular strain grew faster in conjunctival cells than in cervical cells. Coinfection with genital (D or L2) and ocular strains expedited recovery of the ocular strain. CONCLUSIONS Precise temporal evaluation of the chlamydial developmental cycle for selected genital and ocular C. trachomatis biovars provides a means for investigating genomic differences that define chlamydial pathotype.

Secondary Outcomes of a Pilot Randomized Trial of Azithromycin Treatment for Asthma

Objectives: The respiratory pathogen Chlamydia pneumoniae (C. pneumoniae) produces acute and chronic lung infections and is associated with asthma. Evidence for effectiveness of antichlamydial antibiotics in asthma is limited. The primary objective of this pilot study was to investigate the feasibility of performing an asthma clinical trial in practice settings where most asthma is encountered and managed. The secondary objectives were to investigate (1) whether azithromycin treatment would affect any asthma outcomes and (2) whether C. pneumoniae serology would be related to outcomes. This report presents the secondary results. Design: Randomized, placebo-controlled, blinded (participants, physicians, study personnel, data analysts), allocation-concealed parallel group clinical trial. Setting: Community-based health-care settings located in four states and one Canadian province. Participants: Adults with stable, persistent asthma. Interventions: Azithromycin (six weekly doses) or identical matching placebo, plus usual community care. Outcome Measures: Juniper Asthma Quality of Life Questionnaire (Juniper AQLQ), symptom, and medication changes from baseline (pretreatment) to 3 mo posttreatment (follow-up); C. pneumoniae IgG and IgA antibodies at baseline and follow-up. Results: Juniper AQLQ improved by 0.25 (95% confidence interval; −0.3, 0.8) units, overall asthma symptoms improved by 0.68 (0.1, 1.3) units, and rescue inhaler use decreased by 0.59 (−0.5, 1.6) daily administrations in azithromycin-treated compared to placebo-treated participants. Baseline IgA antibodies were positively associated with worsening overall asthma symptoms at follow-up (p = 0.04), but IgG was not (p = 0.63). Overall asthma symptom improvement attributable to azithromycin was 28% in high IgA participants versus 12% in low IgA participants (p for interaction = 0.27). Conclusions: Azithromycin did not improve Juniper AQLQ but appeared to improve overall asthma symptoms. Larger community-based trials of antichlamydial antibiotics for asthma are warranted.

Emerging strategies in the diagnosis, prevention and treatment of chlamydial infections

Chlamydial infections cause a spectrum of diseases affecting millions of individuals worldwide. Chlamydia trachomatis is the most common sexually transmitted bacterium and the causative agent of trachoma, the leading cause of preventable infectious blindness in the world. The unique intracellular life-cycle and the chronic, persistent nature of chlamydial infections have hindered efforts to develop optimal diagnostic, preventive and treatment strategies for these pathogens. The reported association of C. pneumoniae with atherosclerosis and adult onset asthma suggests that these organisms may play an important role in the aetiology of chronic diseases. Treatment options involving new classes of antibiotics or new versions of existing antibiotics that may provide greater specificity and utility for long-term use against chlamydiae are much needed. In addition, new combinations of therapies are needed to manage existing chronic conditions and at the same time to alleviate any role that chlamydiae could be playing in these conditions. Novel strategies that address these shortcomings are apparent in recent research efforts. This review summarises patent claims of emerging strategies to diagnose, prevent and treat chlamydial infections. In addition, current efforts to develop suitable vaccine candidates are highlighted.