Eva Van Braeckel

Vaccine-induced monoclonal antibodies targeting circumsporozoite protein prevent Plasmodium falciparum infection

Malaria, which is the result of Plasmodium falciparum infection, is a global health threat that resulted in 655,000 deaths and 216 million clinical cases in 2010 alone. Recent phase 3 trials with malaria vaccine candidate RTS,S/AS01 (RTS,S) in children has demonstrated modest efficacy against clinical and severe malaria. RTS,S targets the pre-erythrocytic phase of the disease and induces high antibody titers against the P. falciparum circumsporozoite protein (CSP) and a moderate CD4(+) T cell response. The individual contribution of these adaptive immune responses to protection from infection remains unknown. Here, we found that prophylactic administration of anti-CSP mAbs derived from an RTS,S-vaccinated recipient fully protected mice with humanized livers from i.v.- and mosquito bite–delivered P. falciparum sporozoite challenge. Titers of anti-CSP that conveyed full protection were within the range observed in human RTS,S vaccine recipients. Increasing anti-CSP titers resulted in a dose-dependent reduction of the liver parasite burden. These data indicate that RTS,S-induced antibodies are protective and provide sterilizing immunity against P. falciparum infection when reaching or exceeding a critical plasma concentration.

HIV vaccines: Can CD4+ T cells be of help?

Defining immune correlates of protection against the human immunodeficiency virus (HIV) remains a major challenge. While the role of neutralizing antibodies and CD8+ T cell responses has been widely acknowledged and applied in vaccine development, little vaccine candidates have focused on CD4+ T cells. As the main target of HIV, CD4+ T cells play a pivotal role in HIV infection. An HIV vaccine that elicits strong, multi-specific, polyfunctional and persisting CD4+ T cell responses would therefore have the potential of lowering viral set point when HIV infection occurs or reducing viral load in already infected patients. In a combined approach with neutralizing antibodies and CD8+ T cells, CD4+ T cells cannot only enhance the magnitude, quality and durability of the desired antibody response, but will also provide the help needed to induce and maintain effective antiviral CD8+ T cell responses. In addition, the disease-modifying potential of the CD4+ T cell response, by lowering viral set point and/or viral load and thus probability of transmission, may be beneficial both at the individual and public health level.

AZALEA Trial Highlights Antibiotic Overuse in Acute Asthma Attacks

Asthma affects more than 300 million people worldwide, causing variable symptoms of cough, chest tightness, and exertional or nocturnal dyspnea due to chronic inflammation of the lower airways and bronchial hyperresponsiveness. Acute episodes of worsening respiratory symptoms, called acute exacerbations or asthma attacks, can be life-threatening, and induce important costs, encompassing both direct health care expenses and indirect costs due to absence from work or school. For many decades, asthma attacks have been treated with inhaled shortacting bronchodilators and systemic corticosteroids. There is thus a need for novel therapies which—as add-on treatment to systemic corticosteroids—could hasten clinical and functional recovery in patients experiencing an asthma attack and prevent complications. In this issue of JAMA Internal Medicine, Johnston et al1 report the results of the Azithromycin Against Placebo for Acute Exacerbations of Asthma (AZALEA) trial. In this multicenter, randomized, double-blind, placebo-controlled study in the United Kingdom, they investigated the macrolide azithromycin as a supplement to standard treatment in adult patients presenting to emergency departments (EDs) with an acute asthma exacerbation. Patients were mainly recruited from secondary care hospitals and needed to be enrolled within 48 hours of initial presentation to medical care. Importantly, all patients received a course of oral or systemic corticosteroids. A total of 199 asthma patients (mean age, 40 years; 70% female) were randomized to azithromycin 500 mg daily for 3 days or matching placebo. The primary outcome, that is, diary card asthma symptom score 10 days after randomization, was not different between the azithromycin and placebo groups. Likewise, there were no significant between-group differences in secondary outcomes such as quality-of-life questionnaires, lung function measurements during the exacerbation, or time to a 50% reduction in asthma symptoms. Therefore, addition of azithromycin to standard medical care for acute asthma exacerbations did not result in a statistically or clinically significant benefit. Adverse events were infrequent in both treatment groups, with more gastrointestinal adverse events in the azithromycin group compared with placebo. No data are provided on secondary ED visits or hospital (re-)admissions. In contrast, the Telithromycin, Chlamydophila, and Asthma (TELICAST) study has demonstrated clinical benefit of treatment with telithromycin (800 mg daily for 10 days) vs placebo in acute asthma exacerbations.2 However, severe adverse reactions including liver toxicity limit the use of telithromycin in clinical practice. Why did the AZALEA trial have negative results, whereas the TELICAST study seemed to have positive results? First, there is a crucial difference in trial design: all patients randomized in the AZALEA trial were required to receive systemic corticosteroid treatment, whereas only 34% of randomized patients received corticosteroids in the TELICAST study. Because the beneficial effects of macrolides might be partially attributed to their anti-inflammatory properties, it is difficult to demonstrate benefit on top of the powerful anti-inflammatory effects of systemic corticosteroids, leading to predictably negative results in the AZALEA study as opposed to the TELICAST study. Second, in the AZALEA study only 5% of the azithromycin-treated patients tested positive for current infection with Chlamydophila pneumoniae or Mycoplasma pneumoniae, whereas in the TELICAST study 60% of telithromycin-treated patients had a positive IgM test result for one of these atypical organisms. Because both studies used similar methods of sampling and serological testing, the different prevalences of C pneumoniae infection might have contributed to the different outcomes between the 2 trials. Third, a selection bias occurred in the AZALEA trial because only 199 of 4582 screened patients were randomized, limiting the external validity of the study. Intriguingly, 2044 patients (45% of the enrolled population) were excluded from the trial because they had already received antibiotics. We speculate that patients with an asthma attack who were judged eligible to receive antibiotics by their treating physician would have had a higher likelihood of response to azithromycin treatment than those who were not prescribed antibiotics. Last, the AZALEA study might have had negative results because of the heterogeneity of chronic asthma and acute asthma exacerbations. Long-term therapy with lowdose azithromycin has been shown to be efficacious in preventing exacerbations in several neutrophilic chronic airway diseases, such as cystic fibrosis, bronchiectasis, diffuse panbronchiolitis, chronic obstructive pulmonary disease (COPD), and noneosinophilic severe asthma.3 However, subgroup analysis of the AZALEA study revealed no significant benefit of azithromycin in patients with low blood eosinophil levels. An important finding of the AZALEA study is the high use of antibiotics in adult patients with acute asthma exacerbations, despite the facts that Cochrane reviews have not found sufficient evidence in favor of antimicrobial treatment of acute asthma and that treatment guidelines recommend against routine use of antibiotic therapy. Inappropriate use of antibiotics for acute asthma has been documented in EDs in several countries including the United States, where 22% of acute asthma visits resulted in an antibiotic prescription, and is likely to contribute to increased bacterial antibiotic resistance.4 Restricting the use of antibiotics to those patients with acute exacerbations who will benefit the most is therefore paramount. Because clinical symptoms and signs are nonspecific, accurate biomarkers in blood, sputum, or exhaled breath (eg, Related article AZALEA Trial Highlights Antibiotic Overuse in Acute Asthma Attacks Invited Commentary

Establishing the diagnosis of chronic colonization with Pseudomonas aeruginosa of cystic fibrosis patients: Comparison of the European consensus criteria with genotyping of P. aeruginosa isolates

After antibiotic eradication treatment for a first ever Pseudomonas aeruginosa isolation, the European consensus criteria (ECC) are widely used to assess colonization status with P. aeruginosa in CF-patients. We evaluated to what extent genotyping (GT) of subsequent P. aeruginosa isolates could predict/assess chronic colonization (CC), in comparison with the ECC. METHODS Over a 14-year period, sputa were cultured from 80 CF-patients (age range: 2-51 years), from a first ever isolation of P. aeruginosa onwards. Patients with a positive culture for P. aeruginosa received antibiotic eradication treatment. For the 40 patients for whom three or more P. aeruginosa isolates were available, these isolates were genotyped. RESULTS According to the ECC, 27 out of the 40 patients (67.5%) became CC during the study period (ECC-positive patients). Genotyping confirmed persistence of the same genotype for 25 of these ECC-positive patients. Genotyping indicated persistence of the same genotype for at least two subsequent isolates for 5 out of 13 ECC-negative patients. Culture-positivity characteristics of the 27 ECC-positive patients corresponded well to those of the 30 GT-positive patients, with an overall higher number of positive cultures as well as a shorter interval in between first and second isolate compared to ECC-negative and GT-negative patients. Genotyping indicated persistence of the same genotype on average 9.3 months earlier than CC according to the ECC (P < 0.01). CONCLUSIONS Genotyping of P. aeruginosa isolates confirmed CC for 25 out of 27 ECC-positive patients (92.6% specificity) and predicted CC 9.3 months earlier than the ECC.

An unusual presentation of a case of human psittacosis

Background Chlamydia psittaci is a gram-negative, obligate intracellular organism. Birds are the main reservoir, but also non-avian domestic animals and humans can be infected. In humans it mostly causes respiratory infections due to occupational exposure with varying severity. Sensitive and specific diagnostic tests are needed to define psittacosis in humans as these tests also allow rapid tracing of the animal source. However, diagnosis in humans is often based on time-consuming culture techniques and antibody detection assays as in many countries, the existing molecular diagnostic tests for psittacosis are not reimbursed by the public health insurance. Case presentation An 82-year old female was referred to the hospital with a non-productive cough since four weeks and since one week fever up to 39 °C, myalgia, generalized skin rash, acral edema and generalized weakness under treatment with moxifloxacin. Blood analysis showed signs of inflammation with mild eosinophilia. Chest CT showed multiple peripheral ground glass opacities with consolidation in both lungs. Pulmonary function testing only showed a mild decrease in diffusion capacity. Viral and bacterial serology were negative. As the patient kept a pet parakeet for over ten years, a nested PCR for C. psittaci was performed on a nasopharyngeal swab of the patient and on feces of the parakeet. Both returned positive for the same genotype. Genotyping was performed by a genotype-specific real-time PCR. The patient fully recovered after a ten-day course of azithromycin. Conclusion Due to non-specific signs during psittacosis, early detection of the infection and differentiation from hypersensitivity pneumonitis can be challenging. Culture and antibody titers for C. psittaci have a lower sensitivity than PCR-testing due to several factors. We present a case of human psittacosis (presenting as pneumonia) with diagnosis based on clinical findings confirmed by means of nested PCR. This case suggests the added value of PCR in suspect cases despite negative serology. Our current paper underlines the need for a broader implementation of PCR for early diagnosis of human psittacosis and thus early initiation of correct antibiotic treatment with reduction of morbidity and mortality.

Risk factors and impact of allergic bronchopulmonary aspergillosis in Pseudomonas aeruginosa-negative CF patients

Allergic bronchopulmonary aspergillosis (ABPA) is a major complication in cystic fibrosis (CF) patients. Risk factors for ABPA and clinical deterioration in CF patients, negative for Pseudomonas aeruginosa (Pa), were explored.

Development and validation of an LC tandem MS assay for the quantification of β-lactam antibiotics in the sputum of cystic fibrosis patients

Objectives Antibiotic therapy is of vital importance for the control of infectious exacerbations in cystic fibrosis (CF) patients. However, very little is known regarding the fraction of systemically administered antibiotics reaching the lower respiratory tract secretions. We developed and validated a method to measure the concentrations of piperacillin, ceftazidime, meropenem and aztreonam in CF sputum, and present the validation data. Methods Ultra-performance LC coupled to tandem MS was used. A single sample can be measured in 2.5 min with multiple reaction monitoring in positive electrospray ionization mode. Deuterated internal standards were used and a concentration range of 0.7-160 mg/L was covered. The method was validated according to the EMA guideline on analytical method validation. Results The boundaries within which a reliable measurement in CF sputum can be performed were determined. A few constraints are linked to the instability of the antibiotics in sputum. Piperacillin showed limited stability at room temperature and during freeze-thaw cycles. Autosampler instability was observed after 15 h for aztreonam at low concentrations. Conclusions The method allows a reliable measurement of the selected antibiotics, if precautions are taken regarding the limited stability of piperacillin at room temperature. Due to freeze-thaw instability, piperacillin should always be analysed on the day of sampling. Quick review of the analytical data and reanalysis are needed as low concentrations of aztreonam are not stable in the autosampler.

Case report: a student of Asian origin with Pott’s disease

We describe a case report of a student of Asian origin who presented with fever of unknown origin, cough, recent onset low back pain and weight loss. Initial physical examination was unremarkable. Laboratory results showed inflammation, but extensive testing for bacteriological and viral serology was negative. While the chest Computed Tomography (CT) scan did not show any abnormal findings, pelvic CT scan revealed an osteolytic sacral mass, with extension to the soft tissues and muscles, and concomitant nerve compression. An ultrasonography-guided puncture of the lesion eventually showed Mycobacterium tuberculosis, leading to the diagnosis of tuberculous spondylitis or Pott’s disease. The standard tuberculostatic treatment was applied during 9 months with a good clinical result. Skeletal tuberculosis is not common in Western countries and it can be overlooked in foreign patients with fever of unknown origin.