Examining the Distribution and Impact of Single-Nucleotide Polymorphisms in the Capsular Locus of Streptococcus pneumoniae Serotype 19A

Streptococcus pneumoniae serotype 19A prevalence has increased after the implementation of the PCV7 and PCV10 vaccines. In this study, we have provided, with high accuracy, the genetic diversity of the 19A serotype in a cohort of Dutch invasive pneumococcal disease patients and asymptomatic carriers obtained in the period from 2004 to 2016. The whole genomes of the 338 pneumococcal isolates in this cohort were sequenced and their capsule (cps) loci compared to examine their diversity and determine the impact on the production of capsular polysaccharide (CPS) sugar precursors and CPS shedding. We discovered 79 types with a unique cps locus sequence. Most variation was observed in the rmlB and rmlD genes of the TDP-Rha synthesis pathway and in the wzg gene, which is of unknown function. Interestingly, gene variation in the cps locus was conserved in multiple alleles. Using RmlB and RmlD protein models, we predict that enzymatic function is not affected by the single-nucleotide polymorphisms as identified. To determine if RmlB and RmlD function was affected, we analyzed nucleotide sugar levels using ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC-MS). CPS precursors differed between 19A cps locus subtypes, including TDP-Rha, but no clear correlation was observed. Also, significant differences in multiple nucleotide sugar levels were observed between phylogenetically branched groups. Because of indications of a role for Wzg in capsule shedding, we analyzed if this was affected. No clear indication of a direct role in shedding was found. We thus describe genotypic variety in rmlB, rmlD, and wzg in serotype 19A in the Netherlands, for which we have not discovered an associated phenotype.

Aetiology of acute febrile illness in children in a high malaria transmission area in West Africa

OBJECTIVES

Areas with declining malaria transmission in sub-Saharan Africa have recently witnessed important changes in the aetiology of childhood acute febrile illness (AFI). We describe the aetiology of AFI in a high malaria transmission area in rural Burkina Faso.

METHODS

In a prospective hospital-based diagnostic study, children aged 3 months to 15 years with AFI were recruited and assessed using a systematic diagnostic protocol, including blood cultures, whole blood PCR on a selection of bacterial pathogens, malaria diagnostics and a multiplex PCR on nasopharyngeal swabs targeting 21 viral and 4 bacterial respiratory pathogens.

RESULTS

A total of 589 children with AFI were enrolled from whom an infectious disease was considered in 575 cases. Acute respiratory tract infections, malaria and invasive bacterial infections (IBI) accounted for 179 (31.1%), 175 (30.4%) and 75 (13%) of AFI cases respectively; 16 (21.3%) of IBI cases also had malarial parasitaemia. A viral pathogen was demonstrated from the nasopharynx in 157 children (90.7%) with respiratory tract symptoms. Of all children with viral respiratory tract infections, 154 (92.4% received antibiotics, whereas no antibiotic was provided in 13 (17%) of IBI cases.

CONCLUSIONS

Viral respiratory infections are a common cause of childhood AFI in high malaria transmission areas, next to malaria and IBI. These findings highlight the importance of interventions to improve targeted treatment with antimicrobials. Most patients with viral infections received antibiotics unnecessarily, while a considerable number with IBI did not receive antibiotics.

Multi-component meningococcal serogroup B (MenB)-4C vaccine induces effective opsonophagocytic killing in children with a complement deficiency

Vaccination against meningococcal serogroup B is recommended for patients with a complement deficiency; however, although immunogenicity in this patient group has been shown, efficacy has not yet been established. In this study, we collected serum from children with a complement deficiency in the alternative pathway or in late terminal pathway before and after vaccination with multi‐component meningococcal serogroup B (MenB)‐4C. MenB‐4C is a multi‐component, protein‐based vaccine against MenB consisting of factor H‐binding protein, Neisserial heparin‐binding protein, Neisserial adhesion A and outer membrane vesicles containing Porin A. We assessed the vaccine immunogenicity and vaccine‐mediated protection by a whole cell enzyme‐linked immunosorbent assay with Neisseria meningitidis serogroup B strains H44/76, 5/99 and NZ98/254, which shows that vaccination induced antibody titers against meningococcus. We show that the classical serum bactericidal activity assay with exogenous serum indicates the presence of vaccine‐induced antibodies and capacity to activate complement‐mediated pathogen lysis. However, in children with a late terminal pathway deficiency, no complement‐mediated pathogen lysis was observed when autologous serum was applied in the serum bactericidal activity assay, demonstrating a lack of serum bactericidal activity in children with complement deficiencies. However, MenB‐4C vaccination still induced effective complement‐dependent opsonophagocytic killing against N. meningitidis serogroup B in reconstituted whole blood with autologous serum from children with an alternative pathway or late terminal pathway deficiency. These findings support the recommendation to vaccinate all complement‐deficient children against MenB.

Steroids induce a disequilibrium of secreted interleukin-1 receptor antagonist and interleukin-1β synthesis by human neutrophils

Chronic obstructive pulmonary disease (COPD) is characterised by neutrophilic inflammation in the airways and these neutrophils contribute to the production of inflammatory mediators. Dampening the production of proinflammatory mediators might be an important strategy to treat COPD and glucocorticosteroids are known to do so via inhibition of nuclear factor-κB. However, this pathway is important for the control of pro- and anti-inflammatory genes. We studied the effects of dexamethasone on production and secretion of pro-inflammatory interleukin (IL)-1β and anti-inflammatory secreted IL-1 receptor antagonist (sIL-1Ra) by human neutrophils activated with tumor necrosis factor (TNF)-α. In vitro, TNF-α-stimulated neutrophils produced significant amounts of IL-1β and sIL-1Ra; this production was inhibited by dexamethasone. However, synthesis and secretion of sIL-1Ra was inhibited at lower concentrations dexamethasone compared to IL-1β, which changed the IL-1β:sIL-1Ra ratio significantly. This altered ratio resulted in a more pro-inflammatory condition, as visualised by increased intercellular adhesion molecule-1 expression on human endothelial cells. In vivo, moderate-to-severe COPD patients using inhaled glucocorticosteroids have decreased plasma sIL-Ra levels compared with mild-to-moderate patients not on glucocorticosteroid treatment. In conclusion, dexamethasone induces a pro-inflammatory shift in the IL-1β:sIL-1Ra cytokine balance in neutrophils in vitro, which might contribute to a lack of endogenous anti-inflammatory signals to dampen inflammation in vivo.