Bordetella pertussis (Pertussis)

Effectiveness of experimental and commercial pertussis vaccines in the elimination of Bordetella pertussis isolates with different genetic profiles in murine model

The aim of this study was to compare the elimination of Bordetella pertussis clinical isolates, representing different genotypes in relation to alleles encoding virulence factors (MLST-multi-locus antigen sequence typing), MLVA type (multi-locus variable-number tandem repeat analysis) and PFGE group (pulsed-field gel electrophoresis) from the lungs of naive mice or mice were immunised with the commercial whole-cell pertussis vaccine, the acellular pertussis vaccine and the experimental whole-cell pertussis vaccine. Molecular data indicate that the resurgence of pertussis in populations with high vaccine coverage is associated with genomic adaptation of B. pertussis, to vaccine selection pressure. Pertactin-negative B. pertussis isolates were suspected to contribute to the reduced vaccine effectiveness. It was shown that one of the isolates used is PRN deficient. The mice were intranasally challenged with bacterial suspension containing approximately 5 × 10 7 CFU/ml B. pertussis. The immunogenicity of the tested vaccines against PT (pertussis toxin), PRN (pertactin), FHA (filamentous haemagglutinin) and FIM (fimbriae types 2 and 3) was examined. The commercial whole-cell and acellular pertussis vaccines induced an immunity effective at eliminating the genetically different B. pertussis isolates from the lungs. However, the elimination of the PRN-deficient isolate from the lungs of mice vaccinated with commercial vaccines was delayed as compared to the PRN ( +) isolate, suggesting phenotypic differences with the circulating isolates and vaccine strains. The most effective vaccine was the experimental vaccine with the composition identical to that of the strains used for infection.

Whooping cough complicating pulmonary hypertension in pregnancy

We report a case of a previously fit woman who presented at 26 weeks into her fourth pregnancy with a dry cough. Following a nasopharyngeal swab, she was diagnosed with a pertussis infection, and treated with antibiotics. A chest X-ray showed right atrial dilatation and an echocardiogram was scheduled outpatient. However, after re-presenting with worsening cough and dyspnoea, an inpatient echocardiogram was performed which suggested elevated pulmonary pressures with significant tricuspid regurgitation, as confirmed by subsequent cardiac catheterisation. She had an elective caesarean section at 34 weeks and underwent repeat right heart catheterisation which revealed persistent, and likely pre-existing, pulmonary arterial hypertension. This case highlights the importance of thorough assessment of non-obstetric symptoms in pregnancy in formulating alternative differentials, even after a diagnosis has been made, to prevent potentially life-threatening conditions from being missed. It also shows that although often associated, respiratory and cardiac causes may coexist separately.

Modeling Immune Evasion and Vaccine Limitations by Targeted Nasopharyngeal Bordetella pertussis Inoculation in Mice

Conventional pertussis animal models deliver hundreds of thousands of Bordetella pertussis bacteria deep into the lungs, rapidly inducing severe pneumonic pathology and a robust immune response. However, human infections usually begin with colonization and growth in the upper respiratory tract. We inoculated only the nasopharynx of mice to explore the course of infection in a more natural exposure model. Nasopharyngeal colonization resulted in robust growth in the upper respiratory tract but elicited little immune response, enabling prolonged and persistent infection. Immunization with human acellular pertussis vaccine, which prevents severe lung infections in the conventional pneumonic infection model, had little effect on nasopharyngeal colonization. Our infection model revealed that B. pertussis can efficiently colonize the mouse nasopharynx, grow and spread within and between respiratory organs, evade robust host immunity, and persist for months. This experimental approach can measure aspects of the infection processes not observed in the conventional pneumonic infection model.

Pharmacotherapy for Bordetella pertussis infection. II. A synthesis of clinical sciences

Despite the plethora of studies that have examined laboratory susceptibility testing for Bordetella pertussis, assessments of treatment have lagged far behind both in quality and quantity. Macrolides and trimethoprim/sulfamethoxazole historically served the needs of both treatment and prevention, albeit there is still controversy about the degree of protection measured both bacteriologically and clinically. As high-level macrolide resistance has emerged in some geographic regions and since macrolides have been the mainstay of therapy, alternative antibiotics need to be defined for pertussis. In vitro susceptibility testing suggests the potential for several alternatives to macrolides, including trimethoprim/sulfamethoxazole, specific β-lactam agents, chloramphenicol, some quinolones and possibly some tetracyclines. For the latter antibiotics, more clinical studies for treatment and prophylaxis are required in to order to establish bacteriological-clinical correlates for outcome. In the interim, if the clinical circumstances mandate the use of proposed interim alternatives to macrolides, outcomes should be assessed with test of cure by culture, since genetic amplification technologies do not discriminate bacterial viability. Whereas there may be debate in regard to using placebo or macrolides as the controls for alternative antibiotic therapy in geographies where most B. pertussis isolates are antibiotic-susceptible, both placebo and macrolide controls should be assessed along with alternative antibiotics in well-designed controlled studies in regions pressured by macrolide resistance. Outcomes of clinical response and epidemiological patterns of disease should continue to be monitored given the degree of macrolide resistance that is emerging.

Cleft Nucleus Lymphocytosis in Young Infants with Pertussis

This study aims to assess whether the cleft nucleus lymphocytosis could be an early promising clue for the diagnosis of pertussis in young infants. Pertussis (whooping cough) is a severe respiratory disease mainly caused by Bordetella pertussis infection and is characterized by a significant rise in the number of leukocyte and lymphocyte in infants and young children. In this study, the Bordetella pertussis DNA was detected from samples of pharyngeal swab by PCR assay. Levels of serum specific IgM against other respiratory pathogens were detected by Enzyme-linked immunosorbent assay (ELISA) assay. The routine blood test including numbers of leukocytes, lymphocytes, and platelets etc. were tested by automatic hemocyte analyzer (Sysemx XN1000). Besides, the morphology of leucocytes was observed in peripheral blood smear with microscope by Wright-Giemsa stain. Three cases of pertussis with cleft nucleus lymphocytes in young infants were discussed in in the neonatal/pediatric intensive care unit in our hospital. Leukocytosis characterized by lymphocytes, as well as thrombocytosis were observed in all patients. Our results demonstrated that cleft nucleus lymphocytosis accompanied with leukocytosis and lymphocytes would be potent assistant indicators for the early diagnosis of pertussis in young children.

Urgent Bordetella PCR in infants under 3 months, a useful tool in the Pediatric Emergency Department

INTRODUCTION

Whooping cough in patients aged under 3 months has higher rates of morbimortality. Hospitalization and treatment with azithromycin is generally recommended. Many patients with cough without other signs of alarm, are admitted and started antibiotic therapy until a result of Bordetella-PCR is available. This technique, when performed urgently, can provide the diagnosis in a few hours. The objective of this study is to determine if its generalisation in the Emergency Department allows to improve patient management.

METHODS

Retrospective cohort study of patients aged under 3 months who underwent Bordetella-PCR testing from upper respiratory tract secretions since March 2011 to December 2017. From December 2015 the test was performed urgently.

RESULTS

One hundred and fifty-eight PCR were performed, 16 (10%) were positive for B. pertussis. Negative results (142; 90%) were divided in 2 cohorts: conventional-PCR, with 74 cases, and urgent-PCR, with 68 cases. The 2 groups were homogeneous in terms of clinical and analytical characteristics. In the urgent-PCR group there was 18% reduction in chest X-rays performed (P=.008). There were 33 (48.5%) patients admitted in the urgent-PCR group, compared to 49 (66.2%) in the conventional-PCR (P=.042). Antibiotic treatment was initiated in 32% of the patients in the urgent-PCR group compared to 67% in the conventional-PCR group (P=.000047), without observing any significant increase in the number of visits to the Emergency Department or worse clinical performance.

CONCLUSIONS

The introduction of urgent PCR in the Emergency Department is a useful tool in the management of infants under 3 months of age with suspected pertussis, since it can avoid unnecessary admissions, diagnostic tests and antibiotic treatments.

BCG-Induced Cross-Protection and Development of Trained Immunity: Implication for Vaccine Design

The Bacillus Calmette-Guérin (BCG) is a live attenuated tuberculosis vaccine that has the ability to induce non-specific cross-protection against pathogens that might be unrelated to the target disease. Vaccination with BCG reduces mortality in newborns and induces an improved innate immune response against microorganisms other than Mycobacterium tuberculosis, such as Candida albicans and Staphylococcus aureus. Innate immune cells, including monocytes and natural killer (NK) cells, contribute to this non-specific immune protection in a way that is independent of memory T or B cells. This phenomenon associated with a memory-like response in innate immune cells is known as "trained immunity." Epigenetic reprogramming through histone modification in the regulatory elements of particular genes has been reported as one of the mechanisms associated with the induction of trained immunity in both, humans and mice. Indeed, it has been shown that BCG vaccination induces changes in the methylation pattern of histones associated with specific genes in circulating monocytes leading to a "trained" state. Importantly, these modifications can lead to the expression and/or repression of genes that are related to increased protection against secondary infections after vaccination, with improved pathogen recognition and faster inflammatory responses. In this review, we discuss BCG-induced cross-protection and acquisition of trained immunity and potential heterologous effects of recombinant BCG vaccines.

Development of a Pertactin-Coated Beads Approach for Screening of Functional Monoclonal Antibodies

Vaccine manufacturers have recently focused on the development of in vitro potency assays to promote 3R's strategy to replace animal testing. To be able to develop an in vitro potency assay, the immunological characteristics of the monoclonal antibodies used in the assay should be well understood as these antibodies likely reflect the biological activity of a vaccine product. The PRN antigen is one of the immunogenic antigens included in many commercialized acellular pertussis vaccines. Development of an in vitro potency assay for PRN is challenging as the biological properties of PRN are not well understood. In addition, binding of Bordetella pertussis to human cells occurs through multiple bacterial molecules, which makes it very challenging to assess if antibodies contribute to prevention of bacterial adhesion. To overcome these challenges, the functionality of several in-house anti-PRN mAbs has been investigated through a novel approach using PRN-coated beads. We were able to consistently quantify the inhibition of PRN-mediated adhesion for each anti-PRN mAb. Application of the protein-coated beads model has not only enabled screening of functional anti-PRN mAbs but can also be expanded for screening of antibodies against other bacterial or viral antigens.