Pneumococcal vaccines: an update on current strategies

Recurrent bacterial meningitis in children in the Netherlands: a nationwide surveillance study

OBJECTIVES

This study aimed to estimate the recurrence rate of culture-positive bacterial meningitis in children in the Netherlands.

DESIGN

Nationwide surveillance study, using the database of the Netherlands Reference Laboratory for Bacterial Meningitis to identify patients with culture-positive bacterial meningitis during childhood.

SETTING

The study was based in the Netherlands.

PARTICIPANTS

A total of 9731 children with a first bacterial meningitis episode between 1 July 1987 and 30 June 2019 were identified.

PRIMARY AND SECONDARY OUTCOME MEASURES

Recurrence was defined as a subsequent episode >28 days, or caused by a different pathogen. Annual incidence and incidence rate ratios (IRRs) comparing the periods 1988-2003 and 2004-2019 were calculated. Predictors of recurrent meningitis were assessed using Cox proportional hazards regression.

RESULTS

Sixty-three (0.6%) of the 9731 children with a first bacterial meningitis episode contracted recurrent meningitis. Neisseria meningitidis was the leading pathogen for first meningitis episodes (52%) and Streptococcus pneumoniae for recurrent episodes (52%). The median annual incidence of first episodes per 100 000 children decreased from 11.81 (IQR 11.26-17.60) in 1988-2003 to 2.60 (IQR 2.37-4.07) in 2004-2019 (IRR 0.25, 95% CI 0.23 to 0.26). The incidence of recurrences did not change: 0.06 (IQR 0.02-0.11) in 1988-2003 to 0.03 (IQR 0.00-0.06) in 2004-2019 (IRR 0.65, 95% CI 0.39 to 1.1). Age above 5 years (OR 3.6 (95% CI 1.5 to 8.3)) and a first episode due to Escherichia coli (OR 25.7 (95% CI 7.2 to 92.0)) were associated with higher risks of recurrence.

CONCLUSION

The recurrence rate of childhood bacterial meningitis in the Netherlands was 0.6%. While the incidence rate of first episodes decreased substantially, this was not the case for recurrent episodes. Older age and a first episode due to E. coli were associated with higher recurrence risks.

Beyond the polysaccharide and glycoconjugate vaccines for Streptococcus pneumoniae: Does protein/peptide nanovaccines hold promises?

Streptococcus pneumoniae having almost 98 serotypes and being common cause of acute otitis media, pneumonia, bacteremia, meningitis etc., which results in high mortality and morbidity globally. Although vaccines like PCV-13 and PPV-23 are available, some problems like serotype replacement and poor immunogenicity in children, old age and immunocompromised people has been observed. To overcome these drawbacks protein/peptide-based vaccine can be a good strategy as these provides wide serotype coverage. However, immunogenicity of protein subunit vaccines is lower, that issue can be solved by using adjuvants. Recently nanoparticles as an adjuvant for vaccine delivery being used, which has provided not only good immunogenicity but also improved delivery and efficiency of protein-based vaccines. In this review we have discussed the latest advancement of nanoparticles-based protein/peptide vaccine delivery for Streptococcus pneumoniae.

Management of Invasive Infections in Diabetes Mellitus: A Comprehensive Review

Patients with diabetes often have more invasive infections, which may lead to an increase in morbidity. The hyperglycaemic environment promotes immune dysfunction (such as the deterioration of neutrophil activity, antioxidant system suppression, and compromised innate immunity), micro- and microangiopathies, and neuropathy. A greater number of medical interventions leads to a higher frequency of infections in diabetic patients. Diabetic individuals are susceptible to certain conditions, such as rhino-cerebral mucormycosis or aspergillosis infection. Infections may either be the primary symptom of diabetes mellitus or act as triggers in the intrinsic effects of the disease, such as diabetic ketoacidosis and hypoglycaemia, in addition to increasing morbidity. A thorough diagnosis of the severity and origin of the infection is necessary for effective treatment, which often entails surgery and extensive antibiotic use. Examining the significant issue of infection in individuals with diabetes is crucial. Comprehensive research should examine why infections are more common amongst diabetics and what the preventive treatment strategies could be.

Post-13-Valent Pneumococcal Conjugate Vaccine Dynamics in Young Children of Serotypes Included in Candidate Extended-Spectrum Conjugate Vaccines

After worldwide implementation of 10-valent and 13-valent pneumococcal conjugate vaccines (PCV10/PCV13), a 20-valent PCV (PCV20) was developed. We assessed dynamics of non-PCV13 additional PCV20 serotypes (VT20–13), compared with all other non-VT20 serotypes, in children <2 years of age in late PCV13 (2015–2017) and early PCV (2009–2011) periods. Our prospective population-based multifaceted surveillance included isolates from carriage in healthy children, children requiring chest radiography for lower respiratory tract infections (LRTIs), and children with non-LRTI illness, as well as isolates from acute conjunctivitis, otitis media (OM), and invasive pneumococcal disease (IPD). After PCV13 implementation, VT20–13 increased disproportionally in OM, IPD, and carriage in LRTI. VT20–13/non-VT20 prevalence ratio range was 0.26–1.40. VT20–13 serotypes were more frequently antimicrobial-nonsusceptible than non-VT20 serotypes. The disproportionate increase of VT20–13 in respiratory infections and IPD points to their higher disease potential compared with all other non-VT20 as a group.

Recent updates in COVID-19 with emphasis on inhalation therapeutics: Nanostructured and targeting systems

The current world health threat posed by the novel coronavirus disease of 2019 (COVID-19) calls for the urgent development of effective therapeutic options. COVID-19 needs daunting routes such as nano-antivirals. Hence, the role of nanotechnology is very critical in combating this nano-enemy "virus." Although substantial resources are under ongoing attention for prevention and care, we would like to start sharing with readers our vision of the role of inhaled nanomaterials and targeting systems that can play an important role in the fight against the COVID-19. In this review, we underline the genomic structure of COVID-19, recent modes of virus transmission with measures to control the infection, pathogenesis, clinical presentation of SARS-CoV-2, and how much the virus affects the lung. Additionally, the recent therapeutic approaches for managing COVID-19 with emphasis on the value of nanomaterial-based technical approaches are discussed in this review. This review also focuses on the safe and efficient delivery of useable targeted therapies using designed nanocarriers. Moreover, the effectiveness and availability of active targeting of certain specific receptors expressed on the coronavirus surfaces via tailored ligand nanoparticles are manipulated. It was also highlighted in this review the role of inhaled medicines including antivirals and repurposed drugs for fighting the associated lung disorders and efficiency of developed vaccines. Moreover, the inhalation delivery safety techniques were also highlighted.

On-demand biomanufacturing of protective conjugate vaccines

Conjugate vaccines are among the most effective methods for preventing bacterial infections. However, existing manufacturing approaches limit access to conjugate vaccines due to centralized production and cold chain distribution requirements. To address these limitations, we developed a modular technology for in vitro conjugate vaccine expression (iVAX) in portable, freeze-dried lysates from detoxified, nonpathogenic Escherichia coli. Upon rehydration, iVAX reactions synthesize clinically relevant doses of conjugate vaccines against diverse bacterial pathogens in 1 hour. We show that iVAX-synthesized vaccines against Francisella tularensis subsp. tularensis (type A) strain Schu S4 protected mice from lethal intranasal F. tularensis challenge. The iVAX platform promises to accelerate development of new conjugate vaccines with increased access through refrigeration-independent distribution and portable production.

PspA Diversity, Serotype Distribution and Antimicrobial Resistance of Invasive Pneumococcal Isolates from Paediatric Patients in Shenzhen, China

Introduction

To determine the phenotypes and genotypes of invasive Streptococcus pneumoniae (S. pneumoniae), 108 strains were isolated from paediatric patients with invasive pneumococcal diseases (IPDs) in Shenzhen from 2014 to 2018.

Methods

Serotype profiles were defined by multiplex PCR of the capsule gene. Pneumococcal surface protein A (PspA) classification was performed through pspA gene sequencing. Antimicrobial resistance was examined by broth microdilution. Multilocus sequence typing (MLST) was determined based on next-generation sequencing data.

Results

Eighty-one S. pneumoniae of 17 serotypes were finally collected. The coverage of the 13-conjugated polysaccharide vaccine (PCV13) was 88.9%. After the introduction of PCV13, the nonvaccine serotypes were added by serotypes 15b, 16F and 20. Vaccine serotype 3 increased by four serious cases. The pspA family 1 and pspA family 2 are predominant. The multiple drug resistance rate is 91.3%. None of the nonmeningitis isolates were resistant to penicillin, while 98.8% of all the isolates were resistant to erythromycin.

Discussion

This work characterizes the molecular epidemiology of invasive S. pneumoniae in Shenzhen. Continued surveillance of serotype distribution and antimicrobial susceptibility is necessary to alert antibiotic-resistant nonvaccine serotypes and highly virulent serotypes.

Development of Streptococcus pneumoniae Pan-Group Quorum-Sensing Modulators

The rapid increase in multidrug-resistant pathogens is a major health concern that could bring mankind back to the pre-antibiotic era. Streptococcus pneumoniae is a highly recombinogenic opportunistic pathogen that causes a variety of deadly diseases and rapidly develops resistance to current antibiotic treatments. S. pneumoniae pathogenicity is dependent on a cell-density communication mechanism, or quorum sensing (QS), termed the competence regulon. In this work, we set out to design signal-based QS modulators capable of affecting the two specificity groups found in S. pneumoniae. Through systematic analysis and rational design, we were able to construct peptide-based pan-group QS activators and inhibitors with activities in the nanomolar range. These novel analogues are privileged scaffolds for the development of anti-virulence therapeutics against S. pneumoniae infections.

Risk factor profiles and clinical outcomes for children and adults with pneumococcal infections in Singapore: A need to expand vaccination policy?

Invasive pneumococcal infection is a major cause of morbidity and mortality worldwide despite the availability of pneumococcal vaccines. The aim of this study was to re-evaluate the clinical syndromes, prognostic factors and outcomes for pneumococcal disease in adults and children in Singapore during the period before and after the introduction of the pneumococcal vaccine. We retrospectively analyzed a large cohort of patients admitted to the four main public hospitals in Singapore with S. pneumoniae infection between 1997 and 2013. A total of 889 (64% of all isolates identified in the clinical laboratories) cases were included in the analysis; 561 (63.1%) were adult (≥16 years) cases with a median age of 62 years and 328 (36.9%) were paediatric cases with a median age of 3 years. Bacteraemic pneumonia was the most common syndrome in both groups (69.3% vs. 44.2%), followed by primary bacteraemia without pneumonia (14.3% vs. 13.4%), meningitis (6.4% vs. 7.6%) and non-bacteraemic pneumonia (5.2% vs. 21%). The major serotypes in adults were 3, 4, 6B, 14, 19F and 23F whereas in children they were 14, 6B and 19F, accounting both for nearly half of pneumococcal disease cases. No particular serotype was associated with mortality or severity of the pneumococcal disease. Overall mortality rate was 18.5% in adults and 3% in children. Risk factors for mortality included acute cardiac events in adults, meningitis in children and critical illness and bilateral pulmonary infiltrates in both adults and children. Penicillin resistance was not associated with increased mortality. Our results agree with global reports that the course of pneumococcal disease and its clinical outcome were more severe in adults than in children. The main serotypes causing invasive disease were mostly covered by the vaccines in use. The high mortality rates reflect an urgent need to increase vaccination coverage in both adults and children to tackle this vaccine-preventable infection.

Dietary zinc and the control of Streptococcus pneumoniae infection

Human zinc deficiency increases susceptibility to bacterial infection. Although zinc supplementation therapies can reduce the impact of disease, the molecular basis for protection remains unclear. Streptococcus pneumoniae is a major cause of bacterial pneumonia, which is prevalent in regions of zinc deficiency. We report that dietary zinc levels dictate the outcome of S. pneumoniae infection in a murine model. Dietary zinc restriction impacts murine tissue zinc levels with distribution post-infection altered, and S. pneumoniae virulence and infection enhanced. Although the activation and infiltration of murine phagocytic cells was not affected by zinc restriction, their efficacy of bacterial control was compromised. S. pneumoniae was shown to be highly sensitive to zinc intoxication, with this process impaired in zinc restricted mice and isolated phagocytic cells. Collectively, these data show how dietary zinc deficiency increases sensitivity to S. pneumoniae infection while revealing a role for zinc as a component of host antimicrobial defences.

Zinc deficiency affects one-third of the world’s population and is associated with an increased susceptibility to bacterial infection. Despite this, the molecular basis for how zinc deficiency compromises host control of infection remains to be understood. We show that dietary zinc deficiency impacts host tissue zinc abundances and its mobilization during infection by the major respiratory pathogen Streptococcus pneumoniae. Zinc acts as a direct antimicrobial against the pathogen, mobilized by phagocytic cells as a component of the innate immune response. Although immune activation and infiltration of phagocytic cells is unaffected by host zinc status, the lack of antimicrobial zinc compromises bacterial control in zinc deficient hosts. These findings highlight the importance of zinc sufficiency in resisting bacterial infection.

Serotype and molecular diversity of nasopharyngeal Streptococcus pneumoniae isolates from children before and after vaccination with the ten-valent pneumococcal conjugate vaccine (PCV10) in Ethiopia

Background

Streptococcus pneumoniae is a major human pathogen, and nasopharyngeal colonization is the first step for transmission and pathogenesis of pneumococcal diseases. Ethiopia introduced the 10-valent pneumococcal conjugate vaccine (PCV10) in October 2011. Here we studied nasopharyngeal carriage rates of pneumococci in children and analyzed the serotype and genetic diversity of pneumococcal isolates before first dose and after completion of the vaccine.

Method

A longitudinal study was conducted from February 2013 to November 2016. Totally 789 infants were enrolled at the age of 6 weeks before first dose of PCV10 vaccination, 206 were re-sampled at the age of 9 months, and 201 at 2 years of age after the final dose of PCV10 at the age of 14 weeks. One hundred sixteen children were followed during all the three sampling periods. A total of 422 nasopharyngeal isolates were serotyped using gel diffusion and the Quellung reaction, 325 were typed with pulsed field gel electrophoresis (PFGE), and 12 were selected for multi locus sequence typing (MLST).

Results

Pneumococcal carriage rates at the age of 6 weeks, 9 months and 2 years of age were 26.6% (210/789), 56.8% (117/206) and 48.3% (97/201), respectively. Out of 116 children none of them carried the same strain during the three period and the carriage rate at the age of 6 weeks, 9 months and 2 years were 32.7% (38/116), 59.% (69/116) and 49.1% (57/116) respectively. Totally 59 pneumococcal serotypes were identified among 422 isolates. Serotype 6A (5.0%) dominated followed by 34 (4.5%), 10A (4.0%), 11A (4.0%), 19F (3.8%), 15B (3.8%), 23F (3.6%), and 15A (3.6%). The proportion of non-PCV10 serotypes among the isolates recovered at 6 weeks, 9 months and 2 years was 79.4, 88.9 and 89.7% respectively. Molecular typing of 325 isolates collected at 6 weeks and 9 months of age showed a high genetic diversity.

Conclusion

This study highlights the presence of very diverse serotypes in Ethiopia where non-vaccine serotypes were predominant. Completion of the PCV10 schedule was associated with an approximately 50% reduction of vaccine-type carriage and increase of non-vaccine types. PCV13 would potentially reduce vaccine-type carriage by further 10%.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4024-1) contains supplementary material, which is available to authorized users.

Protection against fatal pneumonia through mucosal and subcutaneous immunization with the pneumococcal SP0148 protein

Streptococcus pneumoniae infection is associated with very high morbidity and mortality throughout the world. Vaccines are an effective measure for the reduction of S. pneumoniae infection. In particular, protein vaccines are attracting increasing attention because of their good immunogenicity and wide coverage of serotypes. Therefore, identifying effective protein vaccine targets is important for protein vaccine development. SP0148 is a promising protein vaccine target for S. pneumoniae and is capable of reducing S. pneumoniae colonization in the nasopharynx of mice through the IL-17A pathway. However, the protective effects of SP0148 in fatal pneumococcal infection have not been evaluated. This study used subcutaneous and nasal immunization routes to systematically evaluate the protective effects of the SP0148 protein in fatal pneumococcal infection. Subcutaneous and nasal mucosal immunization with recombinant SP0148 protein produced effective immune protection against infection with a lethal dose of S. pneumoniae and significantly prolonged survival time and increased the survival rate of mice. Furthermore, nasal immunization with SP0148 induced mouse splenocytes to secrete high levels of the cytokines IFN-γ and IL-17A. Both recombinant SP0148 protein and its antiserum inhibited the adhesion of S.pneumoniae D39 to A549 human lung epithelial cells in a dose-dependent manner. In summary, SP0148 induced mice to produce protective immune responses to fatal S. pneumoniae infection, and our results could contribute to the accumulating data on the use of SP0148 protein vaccines.

Antigen delivery format variation and formulation stability through use of a hybrid vector

A hybrid biological-biomaterial antigen delivery vector comprised of a polymeric shell encapsulating an Escherichia coli core was previously developed for in situ antigen production and subsequent delivery. Due to the engineering capacity of the bacterial core, the hybrid vector provides unique opportunities for immunogenicity optimization through varying cellular localization (cytoplasm, periplasm, cellular surface) and type (protein or DNA) of antigen. In this work, three protein-based hybrid vector formats were compared in which the pneumococcal surface protein A (PspA) was localized to the cytoplasm, surface, and periplasmic space of the bacterial core for vaccination against pneumococcal disease. Furthermore, we tested the hybrid vector's capacity as a DNA vaccine against Streptococcus pneumoniae by introducing a plasmid into the bacterial core to facilitate PspA expression in antigen presenting cells (APCs). Through testing these various formulations, we determined that cytoplasmic accumulation of PspA elicited the strongest immune response (antibody production and protection against bacterial challenge) and enabled complete protection at substantially lower doses when compared to vaccination with PspA + adjuvant. We also improved the storage stability of the hybrid vector to retain complete activity after 1 month at 4 °C using an approach in which hybrid vectors suspended in a microbial freeze drying buffer were desiccated. These results demonstrate the flexibility and robustness of the hybrid vector formulation, which has the potential to be a potent vaccine against S. pneumoniae.

Immunization with outer membrane vesicles displaying conserved surface polysaccharide antigen elicits broadly antimicrobial antibodies

Many microbial pathogens produce a β-(1→6)-linked poly-N-acetyl-d-glucosamine (PNAG) surface capsule, including bacterial, fungal, and protozoan cells. Broadly protective immune responses to this single conserved polysaccharide antigen in animals are possible but only when a deacetylated poly-N-acetyl-d-glucosamine (dPNAG; <30% acetate) glycoform is administered as a conjugate to a carrier protein. Unfortunately, conventional methods for natural extraction or chemical synthesis of dPNAG and its subsequent conjugation to protein carriers can be technically demanding and expensive. Here, we describe an alternative strategy for creating broadly protective vaccine candidates that involved coordinating recombinant poly-N-acetyl-d-glucosamine (rPNAG) biosynthesis with outer membrane vesicle (OMV) formation in laboratory strains of Escherichia coli The glycosylated outer membrane vesicles (glycOMVs) released by these engineered bacteria were decorated with the PNAG glycopolymer and induced high titers of PNAG-specific IgG antibodies after immunization in mice. When a Staphylococcus aureus enzyme responsible for PNAG deacetylation was additionally expressed in these cells, glycOMVs were generated that elicited antibodies to both highly acetylated PNAG (∼95-100% acetate) and a chemically deacetylated dPNAG derivative (∼15% acetate). These antibodies mediated efficient in vitro killing of two distinct PNAG-positive bacterial species, namely S. aureus and Francisella tularensis subsp. holarctica, and mice immunized with PNAG-containing glycOMVs developed protective immunity against these unrelated pathogens. Collectively, our results reveal the potential of glycOMVs for targeting this conserved polysaccharide antigen and engendering protective immunity against the broad range of pathogens that produce surface PNAG.

Identification of SP1683 as a pneumococcal protein that is protective against nasopharyngeal colonization

Serotype-independent protein-based pneumococcal vaccines represent attractive alternatives to capsular polysaccharide-based vaccines. The aim of this study was to identify novel immunogenic proteins from Streptococcus pneumoniae that may be used in protein-based pneumococcal vaccine. An immunoproteomics approach and a humanized severe combined immunodeficient mouse model were used to identify S. pneumoniae proteins that are immunogenic for the human immune system. Among the several proteins identified, SP1683 was selected, recombinantly produced, and infection and colonization murine models were used to evaluate the capacity of SP1683 to elicit protective responses, in comparison to known pneumococcal immunogenic proteins (PhtD and detoxified pneumolysin, dPly). Immunisation with SP1683 elicited a weaker antibody response than immunisation with PhtD and did not provide protection in the model of invasive disease. However, similar to PhtD, it was able to significantly reduce colonization in the mouse model of nasopharyngeal carriage. Treatment with anti-IL17A and anti-IL17F antibodies abolished the protection against colonization elicited by SP1683 or PhtD + dPly, which indicated that the protection afforded in this model was Th17-dependent. In conclusion, intranasal immunization with the pneumococcal protein SP1683 conferred IL17-dependent protection against nasopharyngeal carriage in mice, but systemic immunization did not protect against invasive disease. These results do not support the use of SP1683 as an isolated pneumococcal vaccine antigen. Nevertheless, SP1683 could be used as a first line of defence in formulations combining several proteins.

Korean Red Ginseng enhances pneumococcal Δpep27 vaccine efficacy by inhibiting reactive oxygen species production

Background

Streptococcus pneumoniae, more than 90 serotypes of which exist, is recognized as an etiologic agent of pneumonia, meningitis, and sepsis associated with significant morbidity and mortality worldwide. Immunization with a pneumococcal pep27 mutant (Δpep27) has been shown to confer comprehensive, long-term protection against even nontypeable strains. However, Δpep27 is effective as a vaccine only after at least three rounds of immunization. Therefore, treatments capable of enhancing the efficiency of Δpep27 immunization should be identified without delay. Panax ginseng Mayer has already been shown to have pharmacological and antioxidant effects. Here, the ability of Korean Red Ginseng (KRG) to enhance the efficacy of Δpep27 immunization was investigated.

Methods

Mice were treated with KRG and immunized with Δpep27 before infection with the pathogenic S. pneumoniae strain D39. Total reactive oxygen species production was measured using lung homogenates, and inducible nitric oxide (NO) synthase and antiapoptotic protein expression was determined by immunoblotting. The phagocytic activity of peritoneal macrophages was also tested after KRG treatment.

Results

Compared with the other treatments, KRG significantly increased survival rate after lethal challenge and resulted in faster bacterial clearance via increased phagocytosis. Moreover, KRG enhanced Δpep27 vaccine efficacy by inhibiting reactive oxygen species production, reducing extracellular signal–regulated kinase apoptosis signaling and inflammation.

Conclusion

Taken together, our results suggest that KRG reduces the time required for immunization with the Δpep27 vaccine by enhancing its efficacy.

Nasopharyngeal s. pneumoniae carriage and density in Belgian infants after 9 years of pneumococcal conjugate vaccine programme

BACKGROUND

In Belgium, the infant pneumococcal conjugate vaccine (PCV) programme changed from PCV7 (2007-2011) to PCV13 (2011-2015) and to PCV10 (2015-2016). A 3-year nasopharyngeal carriage study was initiated during the programme switch in 2016. Main objective of the year 1 assessment was to obtain a baseline measurement of pneumococcal carriage prevalence, carriage density, serotype distribution and antibiotic resistance.

MATERIALS/METHODS

Two infant populations aged 6-30 months and without use of antibiotics in the seven days prior to sampling were approached: (1) attending one of 85 randomly selected day-care centres (DCC); (2) presenting with AOM at study-trained general practitioners and paediatricians. Demographic and clinical characteristics were documented and a single nasopharyngeal swab was taken. S. pneumoniae were cultured, screened for antibiotic resistance and serotyped, and quantitative Taqman real-time PCR (qRT-PCR) targeting LytA was performed.

RESULTS

Culture-based (DCC: 462/760; 60.8% - AOM: 27/39; 69.2%) and LytA-based (DCC: 603/753; 80.1% - AOM: 32/39; 82.1%) carriage prevalence was high. Average pneumococcal DNA load in LytA-positive day-care samples was 6.5 × 10⁶ copies/µl (95%CI = 3.9-9.2 × 10⁶, median = 3.5 × 10⁵); DNA load was positively associated with signs of common cold and negatively with previous antibiotic use. Culture-based frequency of 13 pneumococcal vaccine (PCV) serotypes was 5.4% in DCC and 7.7% in AOM, with 19F and 14 being most frequent, and frequencies below 0.5% for serotypes 3, 6A, 19A in both populations. Predominant non-PCV serotypes were 23B and 23A in day-care and 11A in infants with AOM. In day-care, resistance to penicillin was rare (<0.5%) and absent against levofloxacin; 32.7% and 16.9% isolates were cotrimoxazole- and erythromycin-resistant respectively.

CONCLUSION

Four years after PCV13 introduction in the vaccination programme, PCV13 serotype carriage was rare in infants throughout Belgium and penicillin resistance was rare. Continued surveillance in the context of a PCV programme switch is necessary.

Molecular Mechanisms of the Binding and Specificity of Streptococcus Pneumoniae Sortase C Enzymes for Pilin Subunits

Pili are elongated structures that protrude from bacteria and increase their virulence. The Streptococcus pnuenomae pilus island 1 pili are composed of three subunits, RrgA, RrgB, and RrgC, and are assembled by three class C sortase C (SrtC) enzymes: SrtC-1, SrtC-2, and SrtC-3. Pilin subunits are recognized by SrtC proteins through a pentapeptide sorting signal, and while previous studies have sought to characterize the selectivities of SrtC isoforms for these subunits, the molecular mechanisms underlying these interactions remain unclear. Here, we report a series of molecular dynamics simulations of each SrtC enzyme with the sorting signals of RrgA, RrgB, and RrgC to determine the structural and thermodynamic basis of pilin recognition. Results show that, in accordance with previous studies, both SrtC-1 and SrtC-3 are selective for RrgB, while SrtC-2 is selective for RrgA. This specificity is tuned by the sorting signal binding conformation in which the first two residue sidechains complement hydrophobic residues around the active site, while the third residue projects away from the catalytic triad and makes specific interactions based on its charge and reach. Together, these results provided atomic-scale descriptions of the SrtC substrate selectivity mechanisms and extend the emerging model of pilin construction in S. pnuenomae.

The Italian Society for Pediatric Nephrology (SINePe) consensus document on the management of nephrotic syndrome in children: Part I - Diagnosis and treatment of the first episode and the first relapse

This consensus document is aimed at providing an updated, multidisciplinary overview on the diagnosis and treatment of pediatric nephrotic syndrome (NS) at first presentation. It is the first consensus document of its kind to be produced by all the pediatric nephrology centres in Italy, in line with what is already present in other countries such as France, Germany and the USA. It is based on the current knowledge surrounding the symptomatic and steroid treatment of NS, with a view to providing the basis for a separate consensus document on the treatment of relapses. NS is one of the most common pediatric glomerular diseases, with an incidence of around 2-7 cases per 100000 children per year. Corticosteroids are the mainstay of treatment, but the optimal therapeutic regimen for managing childhood idiopathic NS is still under debate. In Italy, shared treatment guidelines were lacking and, consequently, the choice of steroid regimen was based on the clinical expertise of each individual unit. On the basis of the 2015 Cochrane systematic review, KDIGO Guidelines and more recent data from the literature, this working group, with the contribution of all the pediatric nephrology centres in Italy and on the behalf of the Italian Society of Pediatric Nephrology, has produced a shared steroid protocol that will be useful for National Health System hospitals and pediatricians. Investigations at initial presentation and the principal causes of NS to be screened are suggested. In the early phase of the disease, symptomatic treatment is also important as many severe complications can occur which are either directly related to the pathophysiology of the underlying NS or to the steroid treatment itself. To date, very few studies have been published on the prophylaxis and treatment of these early complications, while recommendations are either lacking or conflicting. This consensus provides indications for the prevention, early recognition and treatment of these complications (management of edema and hypovolemia, therapy and prophylaxis of infections and thromboembolic events). Finally, recommendations about the clinical definition of steroid resistance and its initial diagnostic management, as well as indications for renal biopsy are provided.

Nasopharyngeal and Oropharyngeal Colonization by Staphylococcus aureus and Streptococcus pneumoniae and Prognostic Markers in Children with Sickle Cell Disease from the Northeast of Brazil

We investigated the nasopharynx and oropharynx microbiota in sickle cell disease (SCD) to identify the microorganisms, antibiotic sensitivity, prevalent serotypes, and association of with laboratorial markers. Oropharynx/nasopharynx secretions were investigated in 143 SCD children aging 6 months to 17 years. Pathogens were isolated using standard procedures, and laboratorial markers were performed by automated methods. Staphylococcus aureus (S. aureus) was isolated from nasopharynx and oropharynx of 64 and of 17 SCD children respectively. Streptococcus pneumoniae (S. pneumoniae) was isolated from the nasopharynx and oropharynx of eight SCD patients. Serotypes of S. pneumoniae were 19F, 23F, and 14. All isolates were susceptible to penicillin, and patients whose nasopharynx and oropharynx were colonized by S. pneumoniae had high concentrations of aspartate transaminase, alanine transaminase, and ferritin. S. pneumoniae isolated were not penicillin-resistant serotypes suggesting that the use of penicillin for prophylaxis and/or treatment of infections is safe. Our finding of colonization and laboratory evaluation in SCD patients suggests that microorganisms are involved in the modulation of chronic inflammatory. The association of colonized microorganisms and laboratorial markers suggest a new approach to these patients follow-up, and additional studies of microorganism colonization and their association with SCD patients' clinical outcome will improve control and prevention strategies.

Pneumococcal Predictive Proteins Selected by Microbial Genomic Approach Are Serotype Cross-Reactive and Bind to Host Extracellular Matrix Proteins

Streptococcus pneumoniae is a colonizer of the human nasopharynx, which accounts for most of the community-acquired pneumonia cases and can cause non-invasive and invasive diseases. Current available vaccines are serotype-specific and the use of recombinant proteins associated with virulence is an alternative to compose vaccines and to overcome these problems. In a previous work, we describe the identification of proteins in S. pneumoniae by reverse vaccinology and the genetic diversity of these proteins in clinical isolates. It was possible to purify a half of 20 selected proteins in soluble form. The expression of these proteins on the pneumococcal cells surface was confirmed by flow cytometry. We demonstrated that some of these proteins were able to bind to extracellular matrix proteins and were recognized by sera from patients with pneumococcal meningitis infection caused by several pneumococcal serotypes. In this context, our results suggest that these proteins may play a role in pneumococcal pathogenesis and might be considered as potential vaccine candidates.

Immunogenicity and protective immunity against otitis media caused by pneumococcus in mice of Hib conjugate vaccine with PsaA protein carrier

This study evaluated the immunogenicity and protective immunity of a Hemophilus influenzae b (Hib) polysaccharide conjugate vaccine with the pneumococcal surface adhesin A (PsaA) protein carrier in young mice. The Hib polysaccharide was conjugated with the rPsaA protein carrier, which was produced using recombinant DNA technology. A total of 15 young mice aged 3 weeks to 5 weeks were immunized with the conjugate vaccine, and another 15 young mice of the same age were immunized with the licensed Hib-tetanus toxoid (TT) vaccine. Furthermore, the third group of 15 young mice was inoculated with phosphate buffer saline as control. The immunized mice were inoculated with pneumococcus in the middle ear. Results showed that IgG antibody responses against both the PsaA protein and Hib polysaccharide were observed in the Hib-PsaA group. However, no statistical difference was observed in the titer of IgG against the Hib polysaccharide between Hib-PsaA and Hib-TT groups. The elimination rate of pneumococcus and the inflammation of the middle ear showed the effectiveness of protective immunity against otitis media caused by pneumococcus. Our results suggest that the Hib polysaccharide can be successfully conjugated with rPsaA via amide condensation. This new Hib-PsaA conjugate vaccine can induce both anti-PsaA and anti-Hib immune responses in young mice and elicit effective protection against acute otitis media caused by pneumococcus.

Pneumococcal Polysaccharide Vaccination Elicits IgG Anti-A/B Blood Group Antibodies in Healthy Individuals and Patients with Type I Diabetes Mellitus

Hypothesis

Blood group antibodies are natural antibodies that develop early in life in response to cross-reactive environmental antigens in the absence of antigen encounter. Even later in life structural similarities in saccharide composition between environmental antigens such as bacterial polysaccharides and blood group A/B antigens could lead to changes in serum levels, IgM/IgG isotype, and affinity maturation of blood group anti-A/B antibodies. We addressed the question whether immunization with pneumococcal polysaccharide (PnP) vaccine Pneumo 23 Vaccine “Pasteur Merieux” (Pn23) could have such an effect in patients with type I diabetes mellitus (DM I), an autoimmune disease where an aberrant immune response to microbial antigens likely plays a role.

Methods

Anti-PnP IgM and IgG responses were determined by ELISA, and the DiaMed-ID Micro Typing System was used to screen anti-A/B antibody titer before and after Pn23 immunization in 28 healthy individuals and 16 patients with DM I. In addition, surface plasmon resonance (SPR) technology using the Biacore^® device and a synthetic blood group A/B trisaccharide as the antigen was applied to investigate IgM and IgG anti-A/B antibodies and to measure antibody binding dynamics.

Results

All healthy individuals and DM I patients responded with anti-PnP IgM and IgG antibody production 4–6 weeks after Pn23 immunization, while no increase in blood group anti-A/B antibody titer was observed when measured by the DiaMed-ID Micro Typing System. Interestingly, isotype-specific testing by SPR technology revealed an increase in blood group anti-A/B IgG, but not IgM, following Pn23 immunization in both patients and controls. No change in binding characteristics of blood group anti-A/B antibodies could be detected following Pn23 vaccination, supporting the assumption of an increase in IgG antibody titer with no or very little affinity maturation.

Conclusion

The study provides evidence for epitope sharing between pneumococcal polysaccharides and blood group ABO antigens, which leads to a booster of blood group anti-A/B antibodies of the IgG isotype after Pn23 immunization in healthy individuals. Manifest autoimmunity such as present in DM I patients has no additional effect on the cross-reactive antibody response against pneumococcal polysaccharides and blood group antigens.

The effects of differences in pspA alleles and capsular types on the resistance of Streptococcus pneumoniae to killing by apolactoferrin

Pneumococcal surface protein A (PspA) is the only pneumococcal surface protein known to strongly bind lactoferrin on the bacterial surface. In the absence of PspA Streptococcus pneumoniae becomes more susceptible to killing by human apolactoferrin (apo-hLf), the iron-free form of lactoferrin. In the present study we examined diverse strains of S. pneumoniae that differed by 2 logs in their susceptibility to apo-hLf. Among these strains, the amount of apo-hLf that bound to cell surface PspA correlated directly with the resistance of the strain to killing by apo-hLf. Moreover examination of different pspA alleles on shared genetic backgrounds revealed that those PspAs that bound more lactoferrin conferred greater resistance to killing by apo-hLf. The effects of capsule on killing of pneumococci by apo-hLf were generally small, but on one genetic background, however, the lack of capsule was associated with 4-times as much apo-hLf binding and 30-times more resistance to killing by apo-hLf. Overall these finding strongly support the hypothesis that most of the variation in the ability of apo-hLf is dependent on the variation in the binding of apo-hLf to surface PspA and this binding is dependent on variation in PspA as well as variation in capsule which may enhance killing by reducing the binding of apo-hLf to PspA.

The "Lid" in the Streptococcus pneumoniae SrtC1 Sortase Adopts a Rigid Structure that Regulates Substrate Access to the Active Site

Many species of Gram-positive bacteria use sortase enzymes to assemble long, proteinaceous pili structures that project from the cell surface to mediate microbial adhesion. Sortases construct highly stable structures by catalyzing a transpeptidation reaction that covalently links pilin subunits together via isopeptide bonds. Most Gram-positive pili are assembled by class C sortases that contain a "lid", a structurally unique N-terminal extension that occludes the active site. It has been hypothesized that the "lid" in many sortases is mobile and thus capable of readily being displaced from the enzyme to facilitate substrate binding. Here, we show using NMR dynamics measurements, in vitro assays, and molecular dynamics simulations that the lid in the class C sortase from Streptococcus pneumoniae (SrtC1) adopts a rigid conformation in solution that is devoid of large magnitude conformational excursions that occur on mechanistically relevant time scales. Additionally, we show that point mutations in the lid induce dynamic behavior that correlates with increased hydrolytic activity and sorting signal substrate access to the active site cysteine residue. These results suggest that the lid of the S. pneumoniae SrtC1 enzyme has a negative regulatory function and imply that a significant energetic barrier must be surmounted by currently unidentified factors to dislodge it from the active site to initiate pilus biogenesis.

Emergence of Neoteric Serotypes Among Multidrug Resistant Strains of Streptococcus pneumoniae Prevalent in Egypt

Background

Streptococcus pneumoniae is still one of the major causes of morbidity and mortality worldwide. The prevalent serotype distribution had shown variation along different studies conducted at different time intervals. In order to efficiently assess the epidemiology of the diseases for effective preventive and treatment strategies, serotype prevalence need to be periodically reassessed.

Objectives

Conducting a reassessment of the prevalent S. pneumoniae serotypes in Egypt as an essential step in the search for a regional vaccine. In addition, monitoring the antibiotic susceptibility patterns of pneumococcal strains currently causing infections as an evaluation of therapeutic strategies applied.

Materials and Methods

A total of 100 specimens of different sources were collected in Cairo, Egypt, from 2011 to 2013, representing almost all different types of diseases caused by S. pneumoniae such as meningitis, pneumonia, otitis media and sinusitis. Conventional and molecular identification methods were performed, the antimicrobial susceptibility patterns were assessed and serotyping was done using PCR assays to identify the most prevalent types. In addition, detection of certain virulence genes for the most prevalent serotypes was carried out.

Results

Our results revealed that in Egypt, currently, the most prevalent serotypes were serogroup 6 and serotype 19F as they represented 58% of all isolates. High rates of resistance were found to different antibiotic classes. The lytA and psaA genes were found to be more sensitive for S. pneumoniae identification than ply.

Conclusions

Our study illustrates the importance of constantly monitoring the prevalent serotypes in any region in order to aid in the development of more effective vaccines.

A Review of Pneumococcal Vaccines: Current Polysaccharide Vaccine Recommendations and Future Protein Antigens

This review describes development of currently available pneumococcal vaccines, provides summary tables of current pneumococcal vaccine recommendations in children and adults, and describes new potential vaccine antigens in the pipeline. Streptococcus pneumoniae, the bacteria responsible for pneumonia, otitis media, meningitis and bacteremia, remains a cause of morbidity and mortality in both children and adults. Introductions of unconjugated and conjugated pneumococcal polysaccharide vaccines have each reduced the rate of pneumococcal infections caused by the organism S. pneumoniae. The first vaccine developed, the 23-valent pneumococcal polysaccharide vaccine (PPSV23), protected adults and children older than 2 years of age against invasive disease caused by the 23 capsular serotypes contained in the vaccine. Because PPSV23 did not elicit a protective immune response in children younger than 2 years of age, the 7-valent pneumococcal conjugate vaccine (PCV7) containing seven of the most common serotypes from PPSV23 in pediatric invasive disease was developed for use in children younger than 2 years of age. The last vaccine to be developed, the 13-valent pneumococcal conjugate vaccine (PCV13), contains the seven serotypes in PCV7, five additional serotypes from PPSV23, and a new serotype not contained in PPSV23 or PCV7. Serotype replacement with virulent strains that are not contained in the polysaccharide vaccines has been observed after vaccine implementation and stresses the need for continued research into novel vaccine antigens. We describe eight potential protein antigens that are in the pipeline for new pneumococcal vaccines.

A structural snapshot of type II pilus formation in Streptococcus pneumoniae

Pili are fibrous appendages expressed on the surface of a vast number of bacterial species, and their role in surface adhesion is important for processes such as infection, colonization, andbiofilm formation. The human pathogen Streptococcus pneumoniae expresses two different types of pili, PI-1 and PI-2, both of which require the concerted action of structural proteins and sortases for their polymerization. The type PI-1 streptococcal pilus is a complex, well studied structure, but the PI-2 type, present in a number of invasive pneumococcal serotypes, has to date remained less well understood. The PI-2 pilus consists of repeated units of a single protein, PitB, whose covalent association is catalyzed by cognate sortase SrtG-1 and partner protein SipA. Here we report the high resolution crystal structures of PitB and SrtG1 and use molecular modeling to visualize a "trapped" 1:1 complex between the two molecules. X-ray crystallography and electron microscopy reveal that the pneumococcal PI-2 backbone fiber is formed by PitB monomers associated in head-to-tail fashion and that short, flexible fibers can be formed even in the absence of coadjuvant proteins. These observations, obtained with a simple pilus biosynthetic system, are likely to be applicable to other fiber formation processes in a variety of Gram-positive organisms.

Bacterial spectrum of spontaneously ruptured otitis media in the era of pneumococcal conjugate vaccination in Germany

Otitis media is a common pediatric disease and the main reason for antibiotic prescription in children. Before implementation of routine childhood pneumococcal vaccination in Germany, serotypes contained in the seven-valent pneumococcal conjugate vaccine (PCV) were among the most frequent pneumococcal serotypes responsible for acute otitis media (AOM). This report describes the first 3 years of a prospective, multicenter, epidemiological cross-sectional study examining the bacteriology of middle ear fluids (MEF) and nasopharyngeal swabs (NPS) of children 2 months to 5 years of age with spontaneously perforated AOM in the era of routine pneumococcal vaccination. MEF was obtained from 963 subjects; NPS from 877. Reported case numbers steeply decreased over the three study years even though the recruiting base remained the same. Among subjects with relevant bacterial growth in their MEF swabs, 113 (11.7%) had Streptococcus pyogenes, 97 (10.1%) Staphylococcus aureus, 88 (9.1%) Streptococcus pneumoniae, 63 (6.5%) Haemophilus influenzae, and 8 (0.8%) Moraxella catarrhalis. S. pneumoniae isolates decreased from 41 (9.3%) in year 1 to 12 (5.7%) in year 3 (p = 0.128). PCV7 serotypes accounted for only 7.9% (n = 7) of isolated pneumococci. Of the 877 subjects with NPS cultures, 465 (53.0%) carried S. pneumoniae, 314 (35.8%) H. influenzae, 292 (33.3%) M. catarrhalis, and 110 (12.5%) S. pyogenes; 79.4% (n = 765) of the children were vaccinated with at least one dose of PCV. Carriage of pneumococci was slightly lower in vaccinated (47.8%) than in unvaccinated (52.7%) children (p = 0.254). PCV7 serotypes were carried by 9.6% of unvaccinated children but by only 4.2% of vaccinated children, resulting in a 56.3% vaccine effectiveness.

CONCLUSIONS

Following universal PCV7 immunization, a clear epidemiological impact of pneumococcal conjugate vaccination was observed as PCV7 serotypes have almost disappeared among AOM.

Animals devoid of pulmonary system as infection models in the study of lung bacterial pathogens

Biological disease models can be difficult and costly to develop and use on a routine basis. Particularly, in vivo lung infection models performed to study lung pathologies use to be laborious, demand a great time and commonly are associated with ethical issues. When infections in experimental animals are used, they need to be refined, defined, and validated for their intended purpose. Therefore, alternative and easy to handle models of experimental infections are still needed to test the virulence of bacterial lung pathogens. Because non-mammalian models have less ethical and cost constraints as a subjects for experimentation, in some cases would be appropriated to include these models as valuable tools to explore host-pathogen interactions. Numerous scientific data have been argued to the more extensive use of several kinds of alternative models, such as, the vertebrate zebrafish (Danio rerio), and non-vertebrate insects and nematodes (e.g., Caenorhabditis elegans) in the study of diverse infectious agents that affect humans. Here, we review the use of these vertebrate and non-vertebrate models in the study of bacterial agents, which are considered the principal causes of lung injury. Curiously none of these animals have a respiratory system as in air-breathing vertebrates, where respiration takes place in lungs. Despite this fact, with the present review we sought to provide elements in favor of the use of these alternative animal models of infection to reveal the molecular signatures of host-pathogen interactions.

Envelope Structures of Gram-Positive Bacteria

Gram-positive organisms, including the pathogens Staphylococcus aureus, Streptococcus pneumoniae, and Enterococcus faecalis, have dynamic cell envelopes that mediate interactions with the environment and serve as the first line of defense against toxic molecules. Major components of the cell envelope include peptidoglycan (PG), which is a well-established target for antibiotics, teichoic acids (TAs), capsular polysaccharides (CPS), surface proteins, and phospholipids. These components can undergo modification to promote pathogenesis, decrease susceptibility to antibiotics and host immune defenses, and enhance survival in hostile environments. This chapter will cover the structure, biosynthesis, and important functions of major cell envelope components in gram-positive bacteria. Possible targets for new antimicrobials will be noted.

Identification of proteins in Streptococcus pneumoniae by reverse vaccinology and genetic diversity of these proteins in clinical isolates

Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide. Virulence-associated proteins common and conserved among all capsular types now represent the best strategy to combat pneumococcal infections. Our aim was to identify conserved targets in pneumococci that showed positive prediction for lipoprotein and extracellular subcellular location using bioinformatics programs and verify the distribution and the degree of conservation of these targets in pneumococci. These targets can be considered potential vaccine candidate to be evaluated in the future. A set of 13 targets were analyzed and confirmed the presence in all pneumococci tested. These 13 genes were highly conserved showing around >96 % of amino acid and nucleotide identity, but they were also present and show high identity in the closely related species Streptococcus mitis, Streptococcus oralis, and Streptococcus pseudopneumoniae. S. oralis clusters away from S. pneumoniae, while S. pseudopneumoniae and S. mitis cluster closer. The divergence between the selected targets was too small to be observed consistently in phylogenetic groups between the analyzed genomes of S. pneumoniae. The proteins analyzed fulfill two of the initial criteria of a vaccine candidate: targets are present in a variety of different pneumococci strains including different serotypes and are conserved among the samples evaluated.

Role of non-conventional T lymphocytes in respiratory infections: the case of the pneumococcus

Non-conventional T lymphocytes constitute a special arm of the immune system and act as sentinels against pathogens at mucosal surfaces. These non-conventional T cells (including mucosal-associated invariant T [MAIT] cells, gamma delta [γδ] T cells, and natural killer T [NKT] cells) display several innate cell-like features and are rapidly activated by the recognition of conserved, stress-induced, self, and microbial ligands. Here, we review the role of non-conventional T cells during respiratory infections, with a particular focus on the encapsulated extracellular pathogen Streptococcus pneumoniae, the leading cause of bacterial pneumonia worldwide. We consider whether MAIT cells, γδ T cells, and NKT cells might offer opportunities for preventing and/or treating human pneumococcus infections.

Immune responses to pneumococcal pilus RrgA and RrgB antigens and their relationship with pneumococcal carriage in humans

OBJECTIVES

Pneumococcal pilus antigens are shown to be important in pneumococcal pathogenesis and induce protective immunity in animal studies, but data in humans are limited. We aimed to investigate serum and mucosal immune responses to pilus-1 proteins (RrgA and RrgB) and their relationship with pneumococcal carriage in humans.

METHODS

Serum and salivary antibodies to RrgA and RrgB in children and adults were analysed by ELISA and immunoblotting. Induction of B cell antibody responses to RrgA and RrgB in nasopharynx-associated lymphoid tissue was studied by ELISpot assay following stimulation with pneumococcal culture supernatants containing pilus proteins.

RESULTS

Significant levels of serum anti-RrgA and -RrgB antibodies were observed, and anti-RrgA antibody appeared to develop earlier in childhood. Importantly, anti-RrgA IgG titres in both serum and saliva were shown to be higher in culture-negative children than in those who were culture-positive for Streptococcus pneumoniae. Stimulation of adenotonsillar cells with pneumococcal culture supernatant induced significant RrgA- and RrgB-specific antibody secreting cells and antibody production.

CONCLUSIONS

Pneumococcal pilus antigens, particularly RrgA, seem to induce significant serum and mucosal antibody responses that may contribute to natural immunity against pneumococcal carriage in children.

Immunogenicity and safety of 23-valent pneumococcal polysaccharide vaccine as a booster dose in 12- to 18-month-old children primed with 3 doses of 7-valent pneumococcal conjugate vaccine

The current study examined the safety and immunogenicity of 23-valent pneumococcal capsular polysaccharide vaccine (Pneumo23(®) [PPV23], Sanofi Pasteur) as a booster dose in 12- to 18-month-old children primed with heptavalent pneumococcal vaccine (PCV7; Prevnar(®), Pfizer). This was a randomized, observer-blinded, 2-arm, controlled, multicenter phase III study performed in Thailand to assess and describe the immunogenicity and safety of PPV23 as a booster dose in children who had received the 3 primary doses of PCV7, the pneumococcal vaccine available during the study period. Children primed with 3 doses of PCV7 were randomized 1:1 to receive a booster immunization with PPV23 or PCV7. Pneumococcal antibody concentrations were measured by enzyme-linked immunosorbent assay and functional antibody levels by multiplex opsonophagocytosis assay on day 30. A total of 339 children were enrolled. Geometric mean serum antibody concentrations against serotypes common to PCV7 and PPV23 (4, 6B, 9V, 14, 18C, 19F, and 23F) increased in both groups but they were higher for serotypes 4, 9V, 18C, and 19F in the PPV23 group. Opsonization indices increased in both groups for all measured serotypes (1, 6B, 14, 19A, and 23F) and were higher for serotypes 6B, 14, and 23F in the PCV7 group and for serotypes 1 and 19A in PPV23 group. Solicited reactions and unsolicited adverse events were similar in the 2 groups and generally mild and transient. No treatment-related serious adverse events were reported. These results confirm that boosting with PPV23 is immunogenic and well tolerated in healthy toddlers primed with PCV7.

Immunogenicity of individual vaccine components in a bivalent nicotine vaccine differ according to vaccine formulation and administration conditions

Structurally distinct nicotine immunogens can elicit independent antibody responses against nicotine when administered concurrently. Co-administering different nicotine immunogens together as a multivalent vaccine could be a useful way to generate higher antibody levels than with monovalent vaccines alone. The immunogenicity and additivity of monovalent and bivalent nicotine vaccines was studied across a range of immunogen doses, adjuvants, and routes to assess the generality of this approach. Rats were vaccinated with total immunogen doses of 12.5 - 100 μg of 3′-aminomethyl nicotine conjugated to recombinant Pseudomonas exoprotein A (3′-AmNic-rEPA), 6-carboxymethylureido nicotine conjugated to keyhole limpet hemocyanin (6-CMUNic-KLH), or both. Vaccines were administered s.c. in alum or i.p. in Freund’s adjuvant at matched total immunogen doses. When administered s.c. in alum, the contributions of the individual immunogens to total nicotine-specific antibody (NicAb) titers and concentrations were preserved across a range of doses. Antibody affinity for nicotine varied greatly among individuals but was similar for monovalent and bivalent vaccines. However when administered i.p. in Freund’s adjuvant the contributions of the individual immunogens to total NicAb titers and concentrations were compromised at some doses. These results support the possibility of co-administering structurally distinct nicotine immunogens to achieve a more robust immune response than can be obtained with monovalent immunogens alone. Choice of adjuvant was important for the preservation of immunogen component activity.

Viability and virulence of pneumolysin, pneumococcal surface protein A, and pneumolysin/pneumococcal surface protein A mutants in the ear

IMPORTANCE

Understanding how pneumococcal proteins affect the pathology of the middle ear and inner ear is important for the development of new approaches to prevent otitis media and its complications.

OBJECTIVES

To determine the viability and virulence of Streptococcus pneumoniae mutants deficient in pneumolysin (Ply-) and pneumococcal surface protein A (PspA-) in the chinchilla middle ear.

DESIGN

Bullae of chinchillas were inoculated bilaterally with wild-type (Wt), Ply-, PspA-, and Ply-/PspA- strains. Bacterial colony-forming units (CFUs) in middle ear effusions were counted at 48 hours. The CFUs of the PspA- group were also counted at 6 to 36 hours after inoculation. Temporal bone histopathological results were compared.

SETTING AND PARTICIPANTS

Twenty-seven chinchillas in an academic research laboratory.

EXPOSURE

Chinchilla middle ears were inoculated with S pneumoniae to produce sufficient volumes of effusions and noticeable histopathological changes in the ears.

MAIN OUTCOMES AND MEASURES

The CFU counts in the middle ear effusions and histopathological changes were compared to determine the effect of pneumococcal protein mutations on chinchilla ears.

RESULTS

At 48 hours, CFUs in middle ears were increased for the Wt and Ply-/PspA- strains, but Ply- remained near inoculum level. No bacteria were detected in the PspA- group. The CFUs of PspA- decreased over time to a low level at 30 to 36 hours. In vitro, PspA- in Todd-Hewitt broth showed an increase in bacterial growth of 2 logs at 43 hours, indicating PspA- susceptibility to host defenses in vivo. The PspA- and Ply- groups had fewer pathologic findings than the Wt or Ply-/PspA- groups. Histopathological analysis showed significant differences in the number of bacteria in the scala tympani in the Wt group compared with the Ply-, PspA-, and Ply-/PspA- groups. The PspA- strain was the least virulent.

CONCLUSIONS AND RELEVANCE

The PspA- mutant was much less viable and less virulent in the ear than the Wt, Ply-, and Ply-/PspA- strains. There was no significant attenuation in the viability and virulence of the Ply-/PspA- mutant compared with the Wt or single mutants. The viability and virulence of pneumococcal mutants seemed to be protein and organ specific.

On-line prediction of the feeding phase in high-cell density cultivation of rE. coli using constructive neural networks

Streptococcus pneumoniae (pneumococcus) is a bacterium responsible for a wide spectrum of illnesses. The surface of the bacterium consists of three distinctive membranes: plasmatic, cellular and the polysaccharide (PS) capsule. PS capsules may mediate several biological processes, particularly invasive infections of human beings. Prevention against pneumococcal related illnesses can be provided by vaccines. There is a sound investment worldwide in the investigation of a proteic antigen as a possible alternative to pneumococcal vaccines based exclusively on PS. A few proteins which are part of the membrane of the pneumococcus seem to have antigen potential to be part of a vaccine, particularly the PspA. A vital aspect in the production of the intended conjugate pneumococcal vaccine is the efficient production (in industrial scale) of both, the chosen PS serotypes as well as the PspA protein. Growing recombinant Escherichia coli (rE. coli) in high-cell density cultures (HCDC) under a fed-batch regime requires a refined continuous control over various process variables where the on-line prediction of the feeding phase is of particular relevance and one of the focuses of this paper. The viability of an on-line monitoring software system, based on constructive neural networks (CoNN), for automatically detecting the time to start the fed-phase of a HCDC of rE. coli that contains a plasmid used for PspA expression is investigated. The paper describes the data and methodology used for training five different types of CoNNs, four of them suitable for classification tasks and one suitable for regression tasks, aiming at comparatively investigate both approaches. Results of software simulations implementing five CoNN algorithms as well as conventional neural networks (FFNN), decision trees (DT) and support vector machines (SVM) are also presented and discussed. A modified CasCor algorithm, implementing a data softening process, has shown to be an efficient candidate to be part of an on-line HCDC monitoring system for detecting the feeding phase of the HCDC process.

Identification of an outer membrane protein of Salmonella enterica serovar Typhimurium as a potential vaccine candidate for Salmonellosis in mice

We report our investigation of the functions of PagN in Salmonella pathogenesis and its potential as a vaccine candidate. Further investigation conducted in this study indicates that the outer membrane protein PagN is important for Salmonella adhesion/invasion of epithelial cells as well as bacterial virulence. When pagN was deleted from Salmonella enterica serovar Typhimurium (S. Typhimurium), the adhesion and invasion of HT-29 epithelial cells was significantly decreased compared with the wild type strain. Mice infected with the pagN mutant strain exhibited less pathological signs in the intestine and survived longer than the wild-type-infected mice. PagN is widely distributed and conserved among clinical isolates of different Salmonella serovars, making PagN a potential vaccine candidate for Salmonella infection. To elucidate the potential of PagN as a vaccine, we expressed and purified recombinant PagN (rPagN). When rPagN was tested in mice, it provided significant protection against Salmonella infection in vivo. In vitro, anti-PagN serum enhanced clearance of Salmonella, indicating a contribution of PagN-specific antibodies to the killing process. This correlates well with the observed protection of mice immunized with rPagN. Our preliminary results indicate more functions of PagN in S. Typhimurium virulence as well as its potential as a protective vaccine.

Inactivated pep27 mutant as an effective mucosal vaccine against a secondary lethal pneumococcal challenge in mice

Purpose

A pep27 mutant may be able to elicit mucosal immunity against pneumococcal diseases, and could be employed as an inexpensive attenuated vaccine. However, this particular mutant contains an erythromycin-resistance marker. The purpose of the current study is to develop a markerless pep27 mutant and assess whether this inactivated mutant is able to induce mucosal immunity.

Materials and Methods

Mice were vaccinated intranasally with the inactivated markerless pep27 mutant every 2 weeks for a total of three times, after which time serum samples were analyzed for antibody titers. The mice were then challenged with a lethal D39 strain and their survival time was measured. The cross-reactivity of the antisera against pep27 was also compared to other mutant serotypes.

Results

Intranasal immunization of mice with the inactivated markerless pep27 mutant provides effective protection and rapidly cleared bacterial colonization in vivo. Moreover, antisera raised against the pep27 mutant may cross-react with several other serotype strains.

Conclusion

Intranasal immunization with the inactivated pep27 mutant may be able to provide mucosal immunity, and could represent an efficient mucosal vaccine.

Genome analysis of a highly virulent serotype 1 strain of Streptococcus pneumoniae from West Africa

Streptococcus pneumoniae is a leading cause of pneumonia, meningitis, and bacteremia, estimated to cause 2 million deaths annually. The majority of pneumococcal mortality occurs in developing countries, with serotype 1 a leading cause in these areas. To begin to better understand the larger impact that serotype 1 strains have in developing countries, we characterized virulence and genetic content of PNI0373, a serotype 1 strain from a diseased patient in The Gambia. PNI0373 and another African serotype 1 strain showed high virulence in a mouse intraperitoneal challenge model, with 20% survival at a dose of 1 cfu. The PNI0373 genome sequence was similar in structure to other pneumococci, with the exception of a 100 kb inversion. PNI0373 showed only15 lineage specific CDS when compared to the pan-genome of pneumococcus. However analysis of non-core orthologs of pneumococcal genomes, showed serotype 1 strains to be closely related. Three regions were found to be serotype 1 associated and likely products of horizontal gene transfer. A detailed inventory of known virulence factors showed that some functions associated with colonization were absent, consistent with the observation that carriage of this highly virulent serotype is unusual. The African serotype 1 strains thus appear to be closely related to each other and different from other pneumococci despite similar genetic content.

Determination of phenotypes and pneumococcal surface protein A family types of Streptococcus pneumoniae from Malaysian healthy children

BACKGROUND

There is limited information about pneumococcal carriage among healthy children in Malaysia. Therefore, this study was conducted to determine the prevalence rate, serotype distribution, susceptibility pattern, and pneumococcal surface protein A (PspA) family types of Streptococcus pneumoniae isolates in the nasal carriage of children 5 years old or younger in three day care centers in Kuala Lumpur, Malaysia.

METHODS

Nasal swabs were collected from 195 healthy children, age 5 years or younger, from June to December 2010. S pneumoniae was identified by phenotypic and genotypic methods. The serotyping was performed using Pneumotest kit (Statens Serum Institut, Copenhagen, Denmark) and the susceptibility pattern was determined by using the E-test method (AB Biodisk, Solna, Sweden). PspA family typing was done using polymerase chain reaction.

RESULTS

S pneumoniae was found in the nasal carriage of 35.4% of children (69 of 195) and penicillin resistance was found in 23.2% (16 of 69). Among the 69 isolates, multidrug-resistant S pneumoniae (MDRSP) was present in 20.3%. All 16 penicillin-resistant S pneumoniae (PRSP) isolates were resistant to erythromycin and 14 PRSPs (87.5%) were resistant to co-trimoxazole. The six most common serotypes were 6A, 23F, 19A, 6B, 19F, and 15C, which were found in 87% of all isolates. Of the 69 isolates, 24.6% belonged to PspA family 1, 71.0% to PspA family 2, and 4.3% to PspA family 3.

CONCLUSION

Twenty-eight of the isolates (40.6%) belonged to serotypes included in the pneumococcal polysaccharide vaccines (PCV) 7 and 10, whereas 48 (69.5%) were included in PCV13. The high rate of PRSP and MDRSP supports the need for continuing surveillance of pneumococcal carriage. The major PspA families were 1 and 2 (95.7%), thus making them suitable candidates for future vaccines.