Pre-clinical evaluation of a 15-valent pneumococcal conjugate vaccine (PCV15-CRM197) in an infant-rhesus monkey immunogenicity model

Epidemiology of Streptococcus pneumoniae Serotypes in Jordan Amongst Children Younger than the Age of 5: A National Cross-Sectional Study

INTRODUCTION

Streptococcus pneumoniae infections are a major cause of mortality and morbidity worldwide. In Jordan, pneumococcal conjugate vaccines (PCVs) are not included in the national vaccination program. Due to the current availability of several PCVs, including PCV-10, PCV-13, and PCV-15, along with PCV-20, currently undergoing pediatric approvals globally, the decision to introduce PCVs and their selection should be based on valid local data on the common serotypes of Streptococcus pneumoniae.

METHODS

This cross-sectional study aimed to identify the frequency of serotypes of Streptococcus pneumoniae in children aged below 5 years hospitalized with invasive pneumococcal diseases (IPDs), including pneumonia, septicemia, and meningitis, during the study's duration in representative areas of Jordan. Serotyping for culture-positive cases was based on the capsular reaction test, known as the Quellung reaction. qPCR was conducted on the blood samples of patients with lobar pneumonia identified via X-ray or on cerebrospinal fluid for those with a positive latex agglutination test for Streptococcus pneumoniae.

RESULTS

This study was based on the analysis of the serotypes of 1015 Streptococcus pneumoniae cases among children younger than the age of 5: 1006 cases with pneumonia, 6 cases with meningitis, and 3 cases with septicemia. Only 23 culture-positive cases were identified in comparison to 992 lobar pneumonia cases, which were PCR-positive but culture-negative, with a PCR positivity rate of 92%. Serotypes 6B, 6A, 14, and 19F were the most common serotypes identified in this study, with prevalence rates of 16.45%, 13.60%, 12.12%, and 8.18%, respectively. PCV-10, PCV-13, PCV-15, and PCV-20 coverage rates were 45.32%, 61.87%, 64.14%, and 68.47%, respectively.

DISCUSSION

To the best of our knowledge, this is the largest prospective study from the Middle East and one of the largest studies worldwide showing the serotypes of Streptococcus pneumoniae. It reveals the urgency for the introduction of a PCV vaccination in Jordan, utilizing recently developed vaccines with a broader serotype coverage.

Impact of aluminum adjuvants on the stability of pneumococcal polysaccharide-protein conjugate vaccines

Development of a vaccine drug product requires formulation optimization to ensure that the vaccine's effectiveness is preserved upon storage throughout the shelf-life of the product. Although aluminum adjuvants have been widely used in vaccine formulations to safely and effectively potentiate an immune response, careful attention must be directed towards ensuring that the type of aluminum adjuvant does not impact the stability of the antigenic composition. PCV15 is a polysaccharide-protein conjugate vaccine comprising the pneumococcal polysaccharide (PnPs) serotypes (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, 22F, 23F and 33F), each individually conjugated to the protein carrier CRM197. PCV15 was formulated with either amorphous aluminum hydroxyphosphate sulfate adjuvant (AAHS) or aluminum phosphate adjuvant (AP) and examined for both stability and immunogenicity. Using a collection of methods to evaluate vaccine stability, it was discovered that certain PCV15 serotypes (e.g., 6A, 19A, 19F) formulated with AAHS resulted in a reduction of immunogenicity in vivo and a reduction in recoverable dose as tested by an in vitro potency assay. The same polysaccharide-protein conjugates formulated with AP were stable regarding all measures tested. Moreover, the reduction in potency of certain serotypes correlated with chemical degradation of the polysaccharide antigen caused by the aluminum adjuvant as measured by reducing polyacrylamide gel electrophoresis (SDS-PAGE), High-Pressure Size Exclusion Chromatography coupled with UV detection (HPSEC-UV) and ELISA immunoassay. This study suggests a formulation, which includes AAHS, may negatively impact the stability of a pneumococcal polysaccharide-protein conjugate vaccine that contains phosphodiester groups. This decrease in stability would likely result in a decrease in the "active" concentration of antigen dose, and herein, it is shown that such instability directly compromised vaccine immunogenicity in an animal model. The results presented in this study help to explain critical degradation mechanisms of pneumococcal polysaccharide-protein conjugate vaccines.

Real-time in situ monitoring of CRM-197 and polysaccharide conjugation reaction by fluorescence spectroscopy

Aims: Process analytical technology (PAT) is increasingly being adopted within the pharmaceutical industry to build quality into a process. Development of PAT that provides real-time in situ analysis of critical quality attributes are highly desirable for rapid, improved process development. Conjugation of CRM-197 with pneumococcal polysaccharides to produce a desired pneumococcal conjugate vaccine is a significantly intricate process that can tremendously benefit from real-time process monitoring. Methods: In this work, a fluorescence-based PAT methodology is described to elucidate CRM-197-polysacharide conjugation kinetics in real time. Results & conclusion: In this work, a fluorescence-based PAT methodology is described to elucidate CRM-197-polysacharide conjugation kinetics in real time.

Preclinical evaluation of an investigational 21-valent pneumococcal conjugate vaccine, V116, in adult-rhesus monkey, rabbit, and mouse models

Despite the widespread effectiveness of pneumococcal conjugate vaccines on the overall incidence of invasive pneumococcal disease, the global epidemiological landscape continues to be transformed by residual disease from non-vaccine serotypes, thus highlighting the need for vaccines with expanded disease coverage. To address these needs, we have developed V116,an investigational 21-valent non-adjuvanted pneumococcal conjugate vaccine (PCV),containingpneumococcal polysaccharides (PnPs) 3, 6A, 7F, 8, 9N, 10A, 11A,12F, 15A, 16F, 17F, 19A, 20, 22F, 23A, 23B, 24F, 31, 33F, 35B, anda de-O-acetylated 15B(deOAc15B) individually conjugated to the nontoxic diphtheria toxoid CRM197 carrier protein. Preclinical studies evaluated the immunogenicity of V116 inadult monkeys, rabbits, and mice. Following one dose, V116 was found to be immunogenic in preclinical animal species and induced functional antibodies for all serotypes included in the vaccine, in addition to cross-reactive functional antibodies to serotypes 6C and 15B. In these preclinical animal studies, the increased valency of V116 did not result in serotype-specific antibody suppression when compared to lower valent vaccines V114 or PCV13. In addition, when compared with naïve controls, splenocytes from V116 to immunized animals demonstrated significant induction of CRM197-specific T cells in both IFN-γ and IL-4 ELISPOT assays, as well as Th1 and Th2 cytokine induction through in vitro stimulation assays, thus suggesting the ability of V116 to engage T cell dependent immune response pathways to aid in development of memory B cells. V116 also demonstrated significant protection in mice from intratracheal challenge with serotype 24F, a novel serotype not contained in any currently licensed vaccine.

Oral streptococci expressing pneumococci-like cross-reactive capsule types can affect WHO recommended pneumococcal carriage procedure

BACKGROUND

Carriage studies are fundamental to assess the effects of pneumococcal vaccines. Since a large proportion of oral streptococci carry homologs of pneumococcal genes, nonculture-based detection and serotyping of upper respiratory tract (URT) samples can be problematic. Herein, we investigated if culture-free molecular methods could differentiate pneumococci from oral streptococci carried by adults in URT.

METHODS

Paired nasopharyngeal (NP) and oropharyngeal (OP) samples were collected from 100 older adults twice a month for one year. Extracts from the combined NP+OP samples (n=2400) were subjected to lytA real-time PCR. Positive samples were subjected to pure culture isolation followed by species confirmation using multiple approaches. Multibead assay and whole-genome sequencing were used for serotyping.

RESULTS

lytA-PCR was positive in 301 combined NP+OP extracts, 20 of which grew probable pneumococcal-like colonies based on colony morphology and biochemical tests. Multiple approaches confirmed that four isolates were S. pneumoniae, three were S. psuedopneumoniae, and thirteen were S. mitis. Eight nonpneumococcal strains carried pneumococcus-like cps loci (size: ~18 to 25 kb) that showed >70% of nucleotide identity with their pneumococcal counterparts. While investigating the antigenic profile, we found some S. mitis strains (P066 and P107) reacted with both serotype-specific polyclonal (Type 39 and FS17b) and monoclonal (Hyp10AG1 and Hyp17FM1) antisera, whereas some strains (P063 and P074) reacted only with polyclonal antisera (Type 5 and FS35a).

CONCLUSION

The extensive capsular overlap suggests that pneumococcal vaccines could reduce carriage of oral streptococci expressing cross-reactive capsules. Further, direct use of culture-free PCR-based methods in URT samples has limited usefulness for carriage studies.

Immunogenicity of PCV24, an expanded pneumococcal conjugate vaccine, in adult monkeys and protection in mice

Invasive pneumococcal disease (IPD) is responsible for serious illnesses such as bacteremia, sepsis, meningitis, and pneumonia in young children, older adults, and persons with immunocompromising conditions and often leads to death. Although the most recent pneumococcal conjugate vaccines (PCVs) have been designed to target serotypes identified as the primary causative agents of IPD, the epidemiological landscape continues to change stressing the need to develop new PCVs. We have developed an investigational 24-valent PCV (PCV24) including serotypes 1, 2, 3, 4, 5, 6A, 6B, 7F, 8, 9N, 9V, 10A, 11A, 12F, 14, 15B, 17F, 18C, 19A, 19F, 20, 22F, 23F, and 33F all conjugated to CRM197 and evaluated this vaccine in adult monkeys. PCV24 was shown to be immunogenic and induced functional antibody for all vaccine serotypes. Of the serotypes common to PCV13 and V114 (PCV15), PCV24 had a similar immunogenic response with the exceptions of 23F which had higher IgG GMCs for PCV13 and V114, and 7F which had higher GMCs for PCV13. Functional antibody responses were similar for the serotypes in common between PCV24, PCV13 and V114 vaccines, with the exception of serotype 7F which was greater for PCV13. Overall, this study shows that PCV24 provided similar immunogenicity as the lower valent vaccines in adult monkeys with no apparent serotype interference. In addition, PCV24 also provided protection against pneumococcal infection in a mouse challenge model.

Truncated Diphtheria Toxin DT390 Enhances the Humoral Immunogenicity of Porcine Circovirus Type 2 Capsid Antigen in Mice

Porcine circovirus type 2 (PCV2) is the causative agent of PCV-associated disease, which harms the swine industry worldwide. Open reading frame 2 of PCV2 encodes the principal immunogenic capsid (Cap) protein, which induces neutralizing antibodies and protective immunity. Cap has been developed as a subunit vaccine against PCV2 infection, although its use is hindered by low immunogenicity. Here, we hypothesized that the truncated diphtheria toxin DT390 might enhance the immunogenicity of Cap. To verify this hypothesis, we fused Cap with DT390, which was expressed using the unique diphtheria toxin-resistant Pichia pastoris expression system. We assessed the immunogenicity of DT390-Cap using BALB/c mice. DT390-Cap induced significantly higher Cap-specific and neutralizing antibodies than Cap alone with or without the ISA201 adjuvant. DT390-Cap with ISA201 adjuvant induced production of more Cap-specific antibodies and neutralizing antibodies than Ingelvac CircoFLEX (positive control). DT390-Cap induced slightly higher Th2-associated interleukin-4 production than Cap alone but did not affect Th1-associated interferon-γ production. The protection study demonstrated that DT390-Cap induced more effective protective immunity than Cap alone, when challenged with PCV2. The viral loads in the lungs, liver, and thymus in mice immunized using DT390-Cap were significantly lower than in those immunized with the corresponding Cap with or without the ISA201 adjuvant. Taken together, the engineered DT390 effectively enhanced the immunogenicity and protective immunity of Cap in mice. Thus, DT390-Cap is a promising novel vaccine candidate against PCV2 infection.

Cord Blood-Based Approach to Assess Candidate Vaccine Adjuvants Designed for Neonates and Infants

Neonates and infants are particularly susceptible to infections, for which outcomes tend to be severe. Vaccination is a key strategy for preventing infectious diseases, but the protective immunity achieved through vaccination typically is weaker in infants than in healthy adults. One possible explanation for the poor acquisition of vaccine-induced immunity in infants is that their innate immune response, represented by toll-like receptors, is immature. The current system for developing pediatric vaccines relies on the confirmation of their safety and effectiveness in studies involving the use of mature animals or adult humans. However, creating vaccines for neonates and infants requires an understanding of their uniquely immature innate immunity. Here we review current knowledge regarding the innate immune system of neonates and infants and challenges in developing vaccine adjuvants for those children through analyses of cord blood.

Enhanced antipneumococcal antibody electrochemiluminescence assay: validation and bridging to the WHO reference ELISA

Aim: To re-optimize the pneumococcal (Pn) electrochemiluminescence (ECL) assay and to validate and bridge the enhanced assay to the WHO ELISA, to support the Phase III clinical trial program for V114, a 15-valent Pn conjugate vaccine. Materials & methods: The Pn ECL assay was re-optimized, validated and formally bridged to the WHO ELISA. Results: The enhanced Pn ECL assay met all prespecified validation acceptance criteria and demonstrated concordance with the WHO ELISA. The corresponding threshold value remains at 0.35 μg/ml for all 15 serotypes. Conclusion: The enhanced Pn ECL assay has been validated for the measurement of antibodies to 15 Pn capsular polysaccharides and is concordant with the WHO ELISA, supporting its use in clinical trials.

Pneumococci Can Become Virulent by Acquiring a New Capsule From Oral Streptococci

Pneumococcal conjugate vaccines have been successful, but their use has increased infections by nonvaccine serotypes. Oral streptococci often harbor capsular polysaccharide (PS) synthesis loci (cps). Although this has not been observed in nature, if pneumococcus can replace its cps with oral streptococcal cps, it may increase its serotype repertoire. In the current study, we showed that oral Streptococcus strain SK95 and pneumococcal strain D39 both produce structurally identical capsular PS, and their genetic backgrounds influence the amount of capsule production and shielding from nonspecific killing. SK95 is avirulent in a well-established in vivo mouse model. When acapsular pneumococcus was transformed with SK95 cps, the transformant became virulent and killed all mice. Thus, cps from oral Streptococcus strains can make acapsular pneumococcus virulent, and interspecies cps transfer should be considered a potential mechanism of serotype replacement. Our findings, along with publications from the US Centers for Disease Control and Prevention, highlight potential limitations of the 2013 World Health Organization criterion for studying pneumococcal serotypes carried without isolating bacteria. We show that an oral streptococcal strain, SK95, and a pneumococcal strain, D39, both produce chemically identical capsular PS. We also show that transferring SK95 cps into noncapsulated, avirulent pneumococcus gave it the capacity for virulence in a mouse model.

Optimization and validation of a microcolony multiplexed opsonophagocytic killing assay for 15 pneumococcal serotypes

Background: To streamline and improve throughput, the agar-based multiplexed opsonophagocytic killing assay (MOPA) was optimized and validated on a microcolony platform for use in the Phase III clinical trial program for V114, an MSD 15-valent pneumococcal conjugate vaccine candidate. Results & methodology: The precision, dilutional linearity and specificity of the microcolony MOPA (mMOPA) were assessed for each serotype in validation experiments. All prespecified acceptance criteria on assay performance were satisfied. Accuracy was assessed by testing 007sp and the US FDA reference panel and comparing to consensus values. The mMOPA produced comparable results to other opsonophagocytic killing assays/MOPAs. Conclusion: The mMOPA is suitable for measuring functional antibodies in adult and pediatric samples. Benefits include throughput, reduced analyst-to-analyst variability and automation potential.

Preclinical in vitro and in vivo profile of a highly-attenuated, broadly efficacious pneumolysin genetic toxoid

Pneumolysin is a highly conserved, cholesterol-dependent cytolysin that is an important Streptococcus pneumoniae virulence factor and an attractive target for vaccine development. To attenuate pneumolysin toxicity, a genetic toxoid was constructed with two amino acid changes, G293S and L460D, termed PLY-D, that reduced cytolytic activity > 125,000-fold. In mice, PLY-D elicited high anti-PLY IgG antibody titers that neutralized the cytolytic activity of the wild-type toxin in vitro. To evaluate the protective efficacy of PLY-D, mice were immunized intramuscularly and then challenged intranasally with a lethal dose of 28 clinical isolates of S. pneumoniae originating from different geographical locations, disease states (i.e. bacteremia, pneumonia), or body sites (i.e. sputum, blood). PLY-D immunization conferred significant protection from challenge with 17 of 20 serotypes (85%) and 22 of 28 strains (79%). Further, we demonstrated that immunization with PLY-D provided statistically significant improvement in survival against challenge with serotype 4 and 18C strains compared to mice immunized with a pneumococcal conjugate vaccine Prevnar 13® (PCV13). Co-administration of PLY-D and PCV13 conferred greater protection against challenge with a serotype 6B strain than immunization with either vaccine alone. These data indicate that PLY-D is a broadly protective antigen with the potential to serve as a serotype-independent vaccine against invasive pneumococcal disease either alone or in combination with PCVs.

Immunogenicity Comparison of a Next Generation Pneumococcal Conjugate Vaccine in Animal Models and Human Infants

BACKGROUND

Evaluation of a pneumococcal conjugate vaccine (PCV) in an animal model provides an initial assessment of the performance of the vaccine prior to evaluation in humans. Cost, availability, study duration, cross-reactivity and applicability to humans are several factors which contribute to animal model selection. PCV15 is an investigational 15-valent PCV which includes capsular polysaccharides from pneumococcal serotypes (ST) 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, 22F, 23F and 33F all individually conjugated to cross-reactive material 197 (CRM197).

METHODS

Immunogenicity of PCV15 was evaluated in infant rhesus macaques (IRM), adult New Zealand white rabbits (NZWR) and CD1 mice using multiplexed pneumococcal electrochemiluminescent (Pn ECL) assay to measure serotype-specific IgG antibodies, multiplexed opsonophagocytosis assay (MOPA) to measure serotype-specific functional antibody responses and bacterial challenge in mice to evaluate protection against a lethal dose of S. pneumoniae.

RESULTS

PCV15 was immunogenic and induced both IgG and functional antibodies to all 15 vaccine serotypes in all animal species evaluated. PCV15 also protected mice from S. pneumoniae serotype 14 intraperitoneal challenge. Opsonophagocytosis assay (OPA) titers measured from sera of human infants vaccinated with PCV15 in a Phase 2 clinical trial showed a good correlation with that observed in IRM (rs=0.69, P=0.006), a medium correlation with that of rabbits (rs=0.49, P=0.06), and no correlation with that of mice (rs=0.04, P=0.89). In contrast, there was no correlation in serum IgG levels between human infants and animal models.

CONCLUSIONS

These results demonstrate that PCV15 is immunogenic across multiple animal species, with IRM and human infants showing the best correlation for OPA responses.

Nasopharyngeal pneumococcal carriage in healthy Turkish children after 13-valent conjugated pneumococcal vaccine implementation in the national immunization program

BACKGROUND

In Turkey, pneumococcal conjugated vaccine (PCV) was introduced to the national immunization program as PCV7 in 2008, and was replaced with PCV13 in 2011. The aims of this study were to investigate the effects of PCV13 on nasopharyngeal pneumococcal carriage (NPC) by determining the serotype distribution, and to identify risk factors for carriage, in healthy Turkish children.

METHODS

This prospective study was conducted on 500 healthy children aged 0-13 years between April and November 2014. Nasopharyngeal swab samples were taken, and molecular method for capsular serotyping was performed by multiplex PCR.

RESULTS

Of 500 children, 43.4% were unvaccinated with a PCV (7- or 13-valent), 56.6% were vaccinated and The NPC rate was found to be 9.8%. Of 49 positive Streptococcus pneumoniae isolates, 26 (53%) were PCV13 vaccine strains (VSs), and 17 (34.7%) were non-VS. Six isolates (12.2%) were not typeable by the method applied. The most common serotypes detected were serotype 3 (18.3%), serotype 19F (14.2%), serotype 6A/B (8.1%), serotype 11A (8.1%), and serotype 15B (8.1%). The total coverage rate of the PCV13 serotypes was 60.4%.

CONCLUSION

A significant decrease in carriage rate was detected within three years after the introduction of PCV13 in Turkey. However, the nasopharyngeal carriage of PCV13 strains was found to be interestingly high.

Impact of the 13-valent pneumococcal conjugate vaccine on the incidences of acute otitis media, recurrent otitis media and tympanostomy tube insertion in children after its implementation into the national immunization program in Turkey

The aim of this study was to investigate changes in the incidences of acute otitis media (AOM), recurrent AOM (rAOM) and tympanostomy tube (TT) insertion in children following the introduction of 13-valent pneumococcal conjugate vaccine (PCV13) into the national immunization program (NIP) of Turkey in April 2011. National coverage for the PCV7 was 97% in 2009, 93% in 2010, 96% in 2011 and for the PVC13 was 97% in 2012, 97% in 2013, 96% in 2014, 97% in 2015, 98% in 2016, and 96% in 2017 for Turkish children younger than 12 months of age. A total of 499932 pediatric visits were recorded, and AOM was diagnosed in 23005 (4.6%) children. The incidence of AOM in children ≤5 years of age decreased from 10700/100000 (2011) to 4712/100000 (2017), with a significant decreasing trend (p < .001, r = -0.965). When the mean annual incidences of AOM between the transition period of PCV13 (years 2011/2012) were compared with those of a post-PCV13 period (years 2016/2017) for children ≤5 years of age, the incidence of AOM was found to be decreased by 54% (p = 0.013). The mean incidence of TT insertion was found to be decreased by 65% (p = 0.003) between the transition period of PCV13 and a post-PCV13 period for children ≤5 years of age. On the other hand, rAOM incidence was found to be increased in whole pediatric age groups. Our study showed a significant decrease in the incidences of AOM and TT insertion in children ≤5 years old after implementation of PCV13 in the NIP in Turkey.

Impact of the introduction of a 13-valent pneumococcal vaccine on pneumococcal serotypes in non-invasive isolates from 2007 to 2016 at a teaching hospital in Japan

PURPOSE

To prevent severe invasive pneumococcal infection, pneumococcal conjugate vaccines (PCVs) were introduced in Japan in 2010, and in 2013 a pneumococcal 13-valent conjugate vaccine (PCV13) was included in the routine vaccination schedule for infants. In this study, we analysed the antimicrobial susceptibilities and capsular types of pneumococci isolated from non-invasive patient sites from 2007 to 2016 to assess the impact of the introduction of PCV13.

METHODOLOGY

A total of 618 pneumococcal isolates collected at a teaching hospital from 2007 to 2016 were used. These isolates were characterized by capsular typing, multilocus sequence typing and antimicrobial susceptibility testing.

RESULTS

Capsular typing indicated that, after the introduction of the PCV, the proportion of PCV13 serotypes decreased (P<0.01), while non-PCV13 serotypes became diverse. In particular, increases in 22 F, 15A and 23A were noted among non-PCV13 serotypes. Regarding antimicrobial susceptibility, the non-susceptibility rate to penicillin of pneumococci that showed higher minimum inhibitory concentrations (MICs) than the susceptibility breakpoint decreased, and pneumococci tended to become susceptible. However, all type 23A pneumococci and 77.8  % of type 15A pneumococci showed the reverse trend, with low susceptibility to penicillin. Furthermore, all 15A and 23A isolates had macrolide resistance genes.

CONCLUSION

These data suggest that PCVs can prevent infections caused by PCV serotypes. However, since non-PCV13-type pneumococci, in particular 15A and 23A, which have acquired multidrug resistance, have already emerged over time, the development of a novel vaccine targeting a broader spectrum of pneumococci is warranted.

International genomic definition of pneumococcal lineages, to contextualise disease, antibiotic resistance and vaccine impact

BACKGROUND

Pneumococcal conjugate vaccines have reduced the incidence of invasive pneumococcal disease, caused by vaccine serotypes, but non-vaccine-serotypes remain a concern. We used whole genome sequencing to study pneumococcal serotype, antibiotic resistance and invasiveness, in the context of genetic background.

METHODS

Our dataset of 13,454 genomes, combined with four published genomic datasets, represented Africa (40%), Asia (25%), Europe (19%), North America (12%), and South America (5%). These 20,027 pneumococcal genomes were clustered into lineages using PopPUNK, and named Global Pneumococcal Sequence Clusters (GPSCs). From our dataset, we additionally derived serotype and sequence type, and predicted antibiotic sensitivity. We then measured invasiveness using odds ratios that relating prevalence in invasive pneumococcal disease to carriage.

FINDINGS

The combined collections (n = 20,027) were clustered into 621 GPSCs. Thirty-five GPSCs observed in our dataset were represented by >100 isolates, and subsequently classed as dominant-GPSCs. In 22/35 (63%) of dominant-GPSCs both non-vaccine serotypes and vaccine serotypes were observed in the years up until, and including, the first year of pneumococcal conjugate vaccine introduction. Penicillin and multidrug resistance were higher (p < .05) in a subset dominant-GPSCs (14/35, 9/35 respectively), and resistance to an increasing number of antibiotic classes was associated with increased recombination (R2 = 0.27 p < .0001). In 28/35 dominant-GPSCs, the country of isolation was a significant predictor (p < .05) of its antibiogram (mean misclassification error 0.28, SD ± 0.13). We detected increased invasiveness of six genetic backgrounds, when compared to other genetic backgrounds expressing the same serotype. Up to 1.6-fold changes in invasiveness odds ratio were observed.

INTERPRETATION

We define GPSCs that can be assigned to any pneumococcal genomic dataset, to aid international comparisons. Existing non-vaccine-serotypes in most GPSCs preclude the removal of these lineages by pneumococcal conjugate vaccines; leaving potential for serotype replacement. A subset of GPSCs have increased resistance, and/or serotype-independent invasiveness.

Pneumococcal vaccines

Streptococcus pneumoniae continues to take a heavy toll on childhood mortality and morbidity across the developing world. An estimated 10.6 million invasive pneumococcal diseases (IPDs) occur every year, with nearly 1 million deaths in children under 5 years of age. Introduction of vaccines in the childhood immunisation programme in developed world has brought down the incidence of the disease considerably. However, childhood immunocompromising illnesses including HIV have increased the risk of IPD several folds. There is also a growing concern on the increasing antibiotic resistance among these invasive strains to penicillin, other beta-lactams and macrolides, making treatment difficult and expensive. It is estimated that about 62% of IPD worldwide is caused by the 10 most common serotypes. Although the ranking of individual pneumococcal serotypes causing serious disease varies among nations, the 7-13 serotypes included in pneumococcal conjugate vaccines (PCVs) may prevent 50%-80% of all paediatric pneumococcal diseases globally. The World Health Organization has recommended the use of PCV-10/13 in the national immunisation programmes (NIPs) of developing countries. Four doses of PCV-13 have been recommended by the US Association of Pediatrics and Centers for Disease Control and Prevention, at intervals of each 2 months for the first 6 months and by the 12^th to 15^th months after birth. This is expected to reduce the morbidity and mortality associated with IPD and simultaneously decrease colonisation with circulating antibiotic-resistant strains in immunized communities. Nevertheless, continued surveillance of antimicrobial resistance in non-vaccine serotypes is necessary to prevent the resurgence of resistance. Other virulence factors which are not serotype specific also need to be studied to overcome the drawbacks of serotype-specific pneumococcal vaccines. PCV-13 was launched during May 2017 under the NIP of five Indian states with the highest pneumococcal diseases in the country and is expected to be rolled out in the other parts of the country in the coming days.

Effectiveness of pneumococcal conjugate vaccines against invasive pneumococcal disease among children under five years of age in Africa: A systematic review

BACKGROUND

Despite the widespread implementation of the pneumococcal conjugate vaccine, Streptococcus pneumoniae remains the leading cause of severe pneumonia associated with mortality among children less than 5 years of age worldwide, with the highest mortality rates recorded in Africa and Asia. However, information on the effectiveness and prevalence of vaccine serotypes post-roll out remains scarce in most African countries. Hence, this systematic review aimed to describe what is known about the decline of childhood invasive pneumococcal disease post-introduction of the pneumococcal conjugate vaccine in Africa.

METHODS

This systematic review included articles published between 2009 and 2018 on the implementation of the pneumococcal conjugate vaccine in Africa. We searched PubMed, Scopus and African Index Medicus for articles in English. Studies on implementation programmes of pneumococcal conjugate vaccine 10/13, with before and after data from different African countries, were considered eligible. The review followed the procedures published in PROSPERO (ID = CRD42016049192).

RESULTS

In total, 2,280 studies were identified through electronic database research, and only 8 studies were eligible for inclusion in the final analysis. Approximately half (n = 3) of these studies were from South Africa. The overall decline in invasive pneumococcal disease ranged from 31.7 to 80.1%. Invasive pneumococcal diseases caused by vaccine serotypes declined significantly, the decline ranged from 35.0 to 92.0%. A much higher decline (55.0-89.0%) was found in children below 24 months of age. Of all vaccine serotypes, the relative proportions of serotypes 1, 5 and 19A doubled following vaccine roll out.

INTERPRETATION

Following the introduction of the pneumococcal conjugate vaccine, a significant decline was observed in invasive pneumococcal disease caused by vaccine serotypes. However, data on the effectiveness in this region remain scarce, meriting continued surveillance to assess the effectiveness of pneumococcal vaccination to improve protection against invasive pneumococcal disease.

Validation of a Multiplexed Opsonophagocytic Assay for 11 Additional Pneumococcal Serotypes and Its Application to Functional Antibody Evaluation Induced by Pneumococcal Polysaccharide Vaccine

BACKGROUND

Various pneumococcal vaccines have been evaluated for immunogenicity by opsonophagocytic assay (OPA). A multiplexed OPA (MOPA) for 13 pneumococcal serotypes was developed by Nahm and Burton, and expanded to 26 serotypes in 2012. The development of new conjugate vaccines with increased valence has necessitated expanded MOPAs to include these additional serotypes. In this study, we validated this expanded MOPA platform and applied to measure antibodies against 11 additional serotypes (2, 8, 9N, 10A, 11A, 12F, 15B, 17F, 20B, 22F, and 33F) in human sera.

METHODS

All materials, including serum, complement, bacterial master stocks, and HL-60 cells, were evaluated for assay optimization. Following optimization, the assay was validated for accuracy, specificity, and intra- and inter-assay precision with sera from adult donors following standard protocols. The assay was applied to evaluate functional antibodies of 42 sera immunized with 23-valent pneumococcal polysaccharide vaccine (PPV23).

RESULTS

The expanded MOPA platform was specific for all serotypes, with the exception of serotype 20. The assay results were highly correlated with those obtained from single-serotype OPA, indicating acceptable accuracy. The coefficients of variation were 7%-24% and 13%-39% in tests of intra- and inter-assay precision, respectively, using three quality-control samples. A MOPA that included 11 additional serotypes in the PPV23 was established and validated with respect to accuracy, specificity, and precision. The opsonic indices of immune sera were obtained using this validated assay.

CONCLUSION

The expanded MOPA will be useful for evaluation of the immunogenicity of PPV23 and future conjugate vaccine formulations.

Prevalence of Nasopharyngeal Carriage, Serotype Distribution, and Antimicrobial Resistance of Streptococcus pneumoniae among Children with Chronic Diseases

The aim of this study was to evaluate the prevalence of nasopharyngeal (NP) carriage and the serotype distribution and antimicrobial resistance of Streptococcus pneumoniae in children with chronic diseases, which predisposes them to invasive pneumococcal disease in comparison with that in healthy children. A cross-sectional prevalence study was performed between February 2015 and February 2016 in Istanbul, Turkey. We enrolled 1,024 children with chronic diseases and 394 healthy children aged 0-18 years. The overall prevalence of S. pneumoniae NP (SPNP) carriage was 9.8%, with 8.4% in healthy children and 10.3% in children with chronic diseases. The prevalence rates of SPNP carriage were 17.5%, 13.5%, 10.5%, 9.3%, 8.6%, 8.6%, 8%, 6.7%, and 4%, respectively, in each of the following risk groups: primary immunodeficiency, asthma, chronic renal failure, congenital heart disease, chronic lung disease, leukemia, nephrotic syndrome, solid organ tumors, and type 1 diabetes mellitus. In the multivariate analysis, a history of otitis media within the last year, a history of pneumonia within the last year, and more than one sibling under 8 years of age were found to be independent risk factors for SPNP carriage.

Production and efficacy of a low-cost recombinant pneumococcal protein polysaccharide conjugate vaccine

Streptococcus pneumoniae is the leading cause of bacterial pneumonia. Although this is a vaccine preventable disease, S. pneumoniae still causes over 1 million deaths per year, mainly in children under the age of five. The biggest disease burden is in the developing world, which is mainly due to unavailability of vaccines due to their high costs. Protein polysaccharide conjugate vaccines are given routinely in the developed world to children to induce a protective antibody response against S. pneumoniae. One of these vaccines is Prevnar13, which targets 13 of the 95 known capsular types. Current vaccine production requires growth of large amounts of the 13 serotypes, and isolation of the capsular polysaccharide that is then chemically coupled to a protein, such as the diphtheria toxoid CRM197, in a multistep expensive procedure. In this study, we design, purify and produce novel recombinant pneumococcal protein polysaccharide conjugate vaccines in Escherichia coli, which act as mini factories for the low-cost production of conjugate vaccines. Recombinant vaccine efficacy was tested in a murine model of pneumococcal pneumonia; ability to protect against invasive disease was compared to that of Prevnar13. This study provides the first proof of principle that protein polysaccharide conjugate vaccines produced in E. coli can be used to prevent pneumococcal infection. Vaccines produced in this manner may provide a low-cost alternative to the current vaccine production methodology.

A Simple Approach to Pneumococcal Vaccination in Adults

Streptococcus pneumoniae is a bacterium responsible for a spectrum of diseases including lobar pneumonia, meningitis, otitis media, and sinusitis. Invasive pneumococcal disease is responsible for significant morbidity and mortality across the world. Concerted efforts led to the development of two vaccinations, Pneumova × 23 and Prevnar 13, for the prevention of pneumococcal disease. The Advisory Committee on Immunization Practices of the US Centers for Disease Control and Prevention provides vaccination schedules for predisposed adults, but the proposed schedules remain a challenge to health-care providers. We performed a systematic review in PubMed and these specialty group websites to present the pathophysiology of pneumococcal disease, outline different pneumococcal vaccinations, and condense recommendations for vaccination administration.

Pneumococcal Vaccines - How Many Serotypes are Enough?

Streptococcus pneumoniae causes meningitis, pneumonia, septicemia, arthritis, sinusitis and otitis media specially in children and over 65 y age groups. It contributes significantly to under-five mortality and morbidity worldwide as well as in India. Use of pneumococcal vaccine seems to be the most effective measure to decrease the disease burden and reduction of under-five mortality. Many countries have already included Pneumococcal Conjugate Vaccines (PCV) in their National Immunization Programmes (NIP). Government of India has announced recently to include PCV13 in NIP in a phased manner. Superiority of a vaccine over the other depends upon serotype coverage, vaccine efficacy, cost effectiveness and safety profile. These facts will be discussed for the vaccines available in India. Further research is warranted to know the disease burden and develop vaccines to have more serotype coverage.

PCR-based discrimination of emerging Streptococcus pneumoniae serotypes 22F and 33F

Serotyping of Streptococcus pneumoniae is important to monitor disease epidemiology and assess the impact of pneumococcal vaccines. Traditionally, the Quellung reaction used serotype-specific antibodies to classify S. pneumoniae based on differences in capsular antigens. More recently, PCR-based serotype deduction relying on serotype-specific capsule biosynthesis genes has been broadly applied for pneumococcal surveillance. However, PCR-based serotyping lacks discrimination for certain S. pneumoniae serotypes, including the differentiation of serotype 22F from 22A, and serotype 33F from 33A and 37. Serotypes 22F and 33F are emerging serotypes that are absent in the currently licensed 13-valent pneumococcal conjugate vaccine, but present in the new candidate 15-valent formulation. This study validated novel PCR reactions to detect and discriminate S. pneumoniae serotypes 22F and 33F. In order to differentiate S. pneumoniae serotypes 22F or 33F from genetically similar serotypes, two novel PCR reactions were designed and validated. The specificity of all PCR targets was evaluated using all 92 different S. pneumoniae serotypes, as well as 32 other streptococci. Reproducibility was evaluated using geographically and genetically diverse strains of S. pneumoniae serotypes 22F and 22A, or serotypes 33F, 33A, and 37 that were previously characterized by reputable reference laboratories. Overall, S. pneumoniae serotypes 22F and 33F could be accurately and reproducibly be detected and discriminated using PCR alone. Such a molecular serotyping approach provides a valuable diagnostic tool that is feasible in any molecular laboratory, to enable pneumococcal serotype surveillance and subsequent assessment of the impact of the new 15-valent candidate pneumococcal vaccine.

Targeting Type IV Secretion System Proteins to Combat Multidrug-Resistant Gram-positive Pathogens

For many gram-positive pathogens, conjugative plasmid transfer is an important means of spreading antibiotic resistance . Therefore, the search for alternative treatments to fight and prevent infections caused by these bacteria has become of major interest. In the present study, we evaluated the protein TraM, from the conjugative plasmid pIP501, as a potential vaccine candidate. Anti-TraM antiserum mediated in vitro opsonophagocytic killing of the strain harboring the pIP501 plasmid and also proved to be cross-reactive against other clinically relevant enterococcal and staphylococcal strains. Specificity of antibodies toward TraM was confirmed by results of an opsonophagocytic inhibition assay and Western blot. In addition, conjugative transfer experiments proved that TraM is essential for the transfer of pIP501. Finally, immunization with either TraM or anti-TraM antiserum reduced significantly the colony counts in mice livers, demonstrating that TraM is a promising vaccine candidate against enterococci and other gram-positive pathogens.

The response to Typhi Vi vaccination is compromised in individuals with primary immunodeficiency

Measurement of an individuals ability to respond to polysaccharide antigens is a crucial test to determine adaptive immunity. Currently the response to Pneumovax^® is utilized but with the success of Prevnar^®, measurement of the response to Pneumovax may be challenging. The aim of the study was to assess the response to Typhi Vi vaccination in both children and adult control groups and patients with primary immunodeficiency (PID). In the control groups, >95% of the individuals had pre Typhi Vi vaccination concentrations <100 U/mL and there was significant increase in concentration post Typhi Vi vaccination (p<0.0001) with>94% achieving ≥3 fold increase in concentration (FI). The response to Typhi Vi vaccination was significantly lower in both children (p = 0.006) and adult (p = 0.002) PID groups when compared to their control groups. 11% and 55% of the children and adult PID groups respectively did not obtain a response >3FI. There were no significant differences between the responses obtained in the children and adult PID groups. When all individuals with PID were separated into those with either hypogammaglobulinemia (HYPO) or common variable immunodeficiency (CVID), both groups had a significantly lower median FI than the control group (19, 95%CI 5–56 vs 59, 95%CI 7–237; p = 0.01 and 1, 95%CI 1–56 vs 32, 95%CI 5–136; p = 0.005). Further, a >3FI differentiated the antibody responses between both the CVID and HYPO groups and their control groups (AUC: 0.83, 95%CI: 0.65–1.00, p = 0.005 and 0.81, 95% CI: 0.65–0.97, p = 0.01). The data suggests that measurement of the response to Typhi Vi vaccination could represent a complementary assay for the assessment of the response to a polysaccharide vaccine.

Position of O-Acetylation within the Capsular Repeat Unit Impacts the Biological Properties of Pneumococcal Serotypes 33A and 33F

Streptococcus pneumoniae (pneumococcus) produces many capsule types that differ in their abilities to evade host immune recognition. To explain these serotype-dependent protective capacities, many studies have investigated capsular thickness or the interaction of the capsule with complement proteins, but the effects of small chemical modifications of the capsule on its function have not been studied. One small chemical modification found frequently among pneumococcal capsules is O-acetylation. Pneumococcal serotype 33A has two membrane-bound O-acetyltransferase genes, wciG and wcjE A 33A wcjE-deficient variant, 33F, occurs naturally and is increasing in prevalence in the wake of widespread conjugate vaccine use, but no wciG-deficient variants have been reported. To study the biological consequence of the loss of O-acetylation, we created wciG-deficient variants in both serotypes 33A and 33F, which we named 33X1 (ΔwciG) and 33X2 (ΔwciG ΔwcjE). Serotypes 33X1 and 33X2 express novel capsule types based on serological and biochemical analyses. We found that loss of WcjE-mediated O-acetylation appears not to affect cell wall shielding, since serotypes 33A and 33F exhibit comparable nonspecific opsonophagocytic killing, biofilm production, and adhesion to nasopharyngeal cells, though serotype 33F survived short-term drying better than serotype 33A. Loss of WciG-mediated O-acetylation in serotypes 33X1 and 33X2, however, resulted in a phenotype resembling that of nonencapsulated strains: increased cell wall accessibility, increased nonspecific opsonophagocytic killing, enhanced biofilm formation, and increased adhesion to nasopharyngeal cells. We conclude that WciG-mediated, but not WcjE-mediated, O-acetylation is important for producing protective capsules in 33A and that small chemical changes to the capsule can drastically affect its biological properties.

TLR7/8 adjuvant overcomes newborn hyporesponsiveness to pneumococcal conjugate vaccine at birth

Infection is the most common cause of mortality in early life, and immunization is the most promising biomedical intervention to reduce this burden. However, newborns fail to respond optimally to most vaccines. Adjuvantation is a key approach to enhancing vaccine immunogenicity, but responses of human newborn leukocytes to most candidate adjuvants, including most TLR agonists, are functionally distinct. Herein, we demonstrate that 3M-052 is a locally acting lipidated imidazoquinoline TLR7/8 agonist adjuvant in mice, which, when properly formulated, can induce robust Th1 cytokine production by human newborn leukocytes in vitro, both alone and in synergy with the alum-adjuvanted pneumococcal conjugate vaccine 13 (PCV13). When admixed with PCV13 and administered i.m. on the first day of life to rhesus macaques, 3M-052 dramatically enhanced generation of Th1 CRM-197-specific neonatal CD4⁺ cells, activation of newborn and infant Streptococcus pneumoniae polysaccharide-specific (PnPS-specific) B cells as well as serotype-specific antibody titers, and opsonophagocytic killing. Remarkably, a single dose at birth of PCV13 plus 0.1 mg/kg 3M-052 induced PnPS-specific IgG responses that were approximately 10-100 times greater than a single birth dose of PCV13 alone, rapidly exceeding the serologic correlate of protection, as early as 28 days of life. This potent immunization strategy, potentially effective with one birth dose, could represent a new paradigm in early life vaccine development.

Immunogenicity differences of a 15-valent pneumococcal polysaccharide conjugate vaccine (PCV15) based on vaccine dose, route of immunization and mouse strain

Pneumococcal disease continues to be a medical need even with very effective vaccines on the market. Globally, there are extensive research efforts to improve serotype coverage with novel vaccines; therefore, conducting preclinical studies in different animal models becomes essential. The work presented herein focuses on evaluating a 15-valent pneumococcal conjugate vaccine (PCV15) in mice. Initially we evaluated several doses of PCV15 in Balb/c mice. The optimal vaccine dose was determined to be 0.4μg per pneumococcal polysaccharide (PS) (0.8μg of 6B) for subsequent studies. This PS dose was chosen for PCV evaluation in mice based on antibody levels determined by multiplexed electrochemiluminescent (ECL) assays, T-cell responses following in vitro stimulation with CRM197 peptides and protection from pneumococcal challenge. We then selected four mouse strains for evaluation: Balb/c, C3H/HeN, CD1 and Swiss Webster (SW), immunized with PCV15 by either intraperitoneal (IP) or intramuscular (IM) routes. We assessed IgG responses by ECL assays and functional antibody activity by multiplexed opsonophagocytic assays (MOPA). Every mouse strain evaluated responded to all 15 serotypes contained in the vaccine. Mice tended to have lower responses to serotypes 6B, 23F and 33F. The IP route of immunization resulted in higher antibody titers for most serotypes in Balb/c, C3H and SW. CD1 mice tended to respond similarly for most serotypes, regardless of route of immunization. Similar trends were observed with the four mouse strains when evaluating functional antibody activity. Given the differences in antibody responses based on mouse strain and route of immunization, it is critical to evaluate pneumococcal vaccines in multiple animal models to determine the optimal formulation before moving to clinical trials.

Vaccination for the control of childhood bacterial pneumonia - Haemophilus influenzae type b and pneumococcal vaccines

Pneumonia in childhood is endemic in large parts of the world and in particular, in developing countries, as well as in many indigenous communities within developed nations. Haemophilus influenzae type b and Streptococcus pneumoniae conjugate vaccines are currently available against the leading bacterial causes of pneumonia. The use of the vaccines in both industrialised and developing countries have shown a dramatic reduction in the burden of pneumonia and invasive disease in children. However, the greatest threat facing pneumococcal conjugate vaccine effectiveness is serotype replacement. The current vaccines provide serotype-specific, antibody-mediated protection against only a few of the 90+ capsule serotypes. Therefore, there has been a focus in recent years to rapidly advance technologies that will result in broader disease coverage and more affordable vaccines that can be used in developing countries. The next generation of pneumococcal vaccines have advanced to clinical trials.

The impact of a pneumococcal conjugate vaccination program on the nasopharyngeal carriage, serotype distribution and antimicrobial resistance of Streptococcus pneumoniae among healthy children in Turkey

BACKGROUND

The 7-valent conjugate pneumococcal vaccine (PCV7) was introduced by the Turkey National Immunization Program in 2008 and replaced by the PCV13 in 2011. We assessed the impact of PCV vaccination on the nasopharyngeal (NP) carriage, serotype distribution and antimicrobial resistance of Streptococcus pneumoniae (SP) among healthy Turkish children.

METHODS

A prospective surveillance study was performed between September 2011 and September 2013 in Istanbul, Turkey. NP swabs, demographic data, and vaccination statuses were obtained from 2165 healthy children aged 0-18years. Pneumococcal carriage was defined by a positive culture; serotyping was performed via multiplex conventional PCR, and the antibiotic susceptibilities of the isolates were determined based on the minimum inhibitory concentration (MIC) values of the Clinical Laboratory Standards Institute (CLSI).

RESULTS

The prevalence of pneumococcal carriage was 6.4%. The carriage rates were 8%, 7%, and 5% in the following age groups: 0-24months, 25-60months, and >60months, respectively. The carriage rate was significantly higher in the 0-24month age group than in the >60months age group (p=0.03). Sixty percent of the children were not vaccinated with any PCV; 4%, 2%, and 4% received at least 1, 2 or 3 doses and 30% children received the full schedule (4 doses) of either PCV7 or PCV13. Among the isolated S. pneumoniae strains, 45% were of the non-vaccine type (NVT) and 55% were of the vaccine type (VT). The children who received at least a single PCV dose had significantly lower odds of colonization via VT serotypes than the non-vaccinated children [odds ratio: 0.61 (95% confidence interval=0.41-0.91), p=0.01]. The percentages of the serotypes covered by PCV7 and PCV13 were 51% and 56%, respectively. The most frequently isolated serotypes were 6A/B/C (n=22, 16.5%), 19F (n=18, 13.5%), 23F (n=15, 11.2%), serotype 9V/A (n=10, 7.5%), 12F (n=5, 4.5%), 15A/F (n=7, 4.5%) and 22 A/F (n=6, 4.5%). Using the meningitis criteria and the MIC, 62% of the isolates were resistant to penicillin and 13% were non-sensitive to ceftriaxone. Erythromycin and clindamycin resistance were 43% and 31%, respectively.

CONCLUSION

We shown that following nation-wide PCV vaccination, S. pneumoniae NP carriage was decreased.

Next generation protein based Streptococcus pneumoniae vaccines

All currently available Streptococcus pneumoniae (Spn) vaccines have limitations due to their capsular serotype composition. Both the 23-valent Spn polysaccharide vaccine (PPV) and 7, 10, or 13-valent Spn conjugate vaccines (PCV-7, 10, -13) are serotype-based vaccines and therefore they elicit only serotype-specific immunity. Emergence of replacement Spn strains expressing other serotypes has consistently occurred following introduction of capsular serotype based Spn vaccines. Furthermore, capsular polysaccharide vaccines are less effective in protection against non-bacteremic pneumonia and acute otitis media (AOM) than against invasive pneumococcal disease (IPD). These shortcomings of capsular polysaccharide-based Spn vaccines have created high interest in development of non-serotype specific protein-based vaccines that could be effective in preventing both IPD and non-IPD infections. This review discusses the progress to date on development of Spn protein vaccine candidates that are highly conserved by all Spn strains, are highly conserved, exhibit maximal antigenicity and minimal reactogenicity to replace or complement the current capsule-based vaccines. Key to development of a protein based Spn vaccine is an understanding of Spn pathogenesis. Based on pathogenesis, a protein-based Spn vaccine should include one or more ingredients that reduce NP colonization below a pathogenic inoculum. Elimination of all Spn colonization may not be achievable or even advisable. The level of expression of a target protein antigen during pathogenesis is another key to the success of protein based vaccines.. As with virtually all currently licensed vaccines, production of a serum antibody response in response to protein based vaccines is anticipated to provide protection from Spn infections. A significant advantage that protein vaccine formulations can offer over capsule based vaccination is their potential benefits associated with natural priming and boosting to all strains of Spn. One of the most universal and comprehensive approaches of identifying novel vaccine candidates is the investigation of human sera from different disease stages of natural infections. Antigens that are robustly reactive in preliminary human serum screening constitute a pathogen-specific antigenome. This strategy has identified a number of Spn protein vaccine candidates that are moving forward in human clinical trials.

Invasive pneumococcal disease in patients with haematological malignancies before routine use of conjugate vaccines in Finland

The baseline national invasive pneumococcal disease (IPD) incidence rate, serotype distribution and serotype coverage of pneumococcal vaccines were evaluated in patients with Hodgkin's and non-Hodgkin's lymphomas, myeloma and leukaemia within 1 year after haematological diagnosis during 1995-2002, before introduction of pneumococcal conjugate vaccines. Pneumococcal serotype distribution among these patients was different from serotypes causing IPD in the general population. The serotype coverages of PCV13 and PPSV23 were 57% and 64%, respectively, lower than in the general population. This reflects a higher predisposition to IPD in vaccinated patients with haematological malignancies and possibly less benefit of herd immunity gained with the wide use of pneumococcal conjugate vaccines in the general population. This data will be useful as a baseline for determining the future role of adult PCV vaccination in these patient groups.

Changing trends in serotype distribution and antimicrobial susceptibility of Streptococcus pneumoniae causing invasive diseases in Central Thailand, 2009-2012

To describe the trends in serotype distribution and antimicrobial susceptibility of S. pneumoniae causing invasive pneumococcal diseases (IPD) we tested 238 pneumococci isolates from normally sterile sites between 2009 and 2012 and compared these findings with previous data collected within our network. Serotyping was performed for 15 serotypes contained in the 7-,10-, 13-, and experimental 15-valent pneumococcal conjugate vaccines (PCV). The most common serotypes found were 6B (13.9%), 19A (12.6%), 14 (8.0%), 18C (5.9%), and 6A (3.8%); and 39.9% were non-PCV15 serotypes. One of 81 patients with available data had breakthrough infection with vaccine serotype (19F). There was a significant increase of serotype 19A among children ≤5 years (5.6% in 2000-2009 vs 18.3% in 2009-2012, P = 0.003). The all-age serotype coverage was 36.4%, 41.5%, 59.3%, and 59.7% for PCV7, PCV10, PCV13, and PCV 15, respectively. The corresponding coverage in children ≤5 years were 46.4%, 48.8%, 73.2%, and 73.2% respectively. High susceptibilities to penicillin (89.7%), cefotaxime (95.7%), cefditoren (90.2% by Spanish breakpoints), ofloxacin (97.9%), and levofloxacin (100%), but low to cefdinir (50.0%), cefditoren (45.1% by US-FDA breakpoints), macrolides (<50%), clindamycin (67.7%), tetracycline (41.4%), and trimethoprim-sulfamethoxazole (32.4%) were observed. Serotype 19A was less susceptible to penicillin (80.0 vs 91.2%, P = 0.046), cefditoren (66.7 vs 95.5% by Spanish breakpoints, P = 0.004), and tetracycline (9.1 vs 45.5%, P = 0.024) than non-19A isolates. These data emphasize the need for continued surveillance to monitor changes in serotypes as well as antimicrobial susceptibilities in order to guide strategies for prevention and treatment.

Emerging, Non-PCV13 Serotypes 11A and 35B of Streptococcus pneumoniae Show High Potential for Biofilm Formation In Vitro

Background

Since the use of pneumococcal conjugate vaccines PCV7 and PCV13 in children became widespread, invasive pneumococcal disease (IPD) has dramatically decreased. Nevertheless, there has been a rise in incidence of Streptococcus pneumoniae non-vaccine serotypes (NVT) colonising the human nasopharynx. Nasopharyngeal colonisation, an essential step in the development of S. pneumoniae-induced IPD, is associated with biofilm formation. Although the capsule is the main pneumococcal virulence factor, the formation of pneumococcal biofilms might, in fact, be limited by the presence of capsular polysaccharide (CPS).

Methodology/Principal Findings

We used clinical isolates of 16 emerging, non-PCV13 serotypes as well as isogenic transformants of the same serotypes. The biofilm formation capacity of isogenic transformants expressing CPSs from NVT was evaluated in vitro to ascertain whether this trait can be used to predict the emergence of NVT. Fourteen out of 16 NVT analysed were not good biofilm formers, presumably because of the presence of CPS. In contrast, serotypes 11A and 35B formed ≥45% of the biofilm produced by the non-encapsulated M11 strain.

Conclusions/Significance

This study suggest that emerging, NVT serotypes 11A and 35B deserve a close surveillance.

Automated capillary Western dot blot method for the identity of a 15-valent pneumococcal conjugate vaccine

Simple Western is a new technology that allows for the separation, blotting, and detection of proteins similar to a traditional Western except in a capillary format. Traditionally, identity assays for biological products are performed using either an enzyme-linked immunosorbent assay (ELISA) or a manual dot blot Western. Both techniques are usually very tedious, labor-intensive, and complicated for multivalent vaccines, and they can be difficult to transfer to other laboratories. An advantage this capillary Western technique has over the traditional manual dot blot Western method is the speed and the automation of electrophoresis separation, blotting, and detection steps performed in 96 capillaries. This article describes details of the development of an automated identity assay for a 15-valent pneumococcal conjugate vaccine, PCV15-CRM197, using capillary Western technology.

Assessment of multidrug resistance, clonality and virulence in non-PCV-13 Streptococcus pneumoniae serotypes in Canada, 2011-13

OBJECTIVES

Serotype replacement in Streptococcus pneumoniae following the implementation of a new vaccine has been associated with the emergence of non-vaccine serotypes as prominent causes of invasive pneumococcal disease (IPD). The aim of this study was to characterize specific non-PCV-13 serotypes 15A, 22F, 33F and 35B from IPD, isolated in Canada post-PCV-13 introduction in 2010.

METHODS

Of 3802 IPD isolates collected from across Canada in 2011-13, 18.4% were found to be serotypes 15A, 22F, 33F and 35B. These 699 isolates were subjected to antimicrobial susceptibility testing, PFGE, MLST, molecular detection of pneumococcal pili and comparison with Pneumococcal Molecular Epidemiology Network (PMEN) clones.

RESULTS

This study demonstrated clonal spread of specific STs, including MDR ST63 and its Sweden(15A)-25-related variants, the increasingly common ST433 and a variant of piliated, penicillin-non-susceptible ST558, related to PMEN clone Utah(35B)-24 (ST377). New STs of serotype 33F were identified. Several potential capsular switching events were identified within these serotypes.

CONCLUSIONS

Non-PCV-13 serotype 22F is increasing in Canada through the rapid clonal expansion of ST433. Numerous new STs associated with serotype 33F indicate the potential divergence of the serotype. Serotypes 15A and 35B in Canada are related to international clones of S. pneumoniae.

Carbohydrate-Based Vaccines: An Overview

Vaccination is one of the key developments in the fight against infectious diseases. It is based on the principle that immunization with pathogen-derived antigens provides protection from the respective infection by inducing an antigen-specific immune response. The discovery by Avery and Heidelberger in the 1920s that capsular polysaccharides (CPS) from Streptococcus pneumoniae are immunoreactive was the starting point of the development of carbohydrate-based vaccines. CPS-specific neutralizing antibodies were found to mediate protection against S. pneumoniae infection. Since the majority of bacterial pathogens carry a dense array of polysaccharides on their surface, the carbohydrate-based vaccine approach was applied to a variety of bacterial strains. The first CPS-based vaccines against S. pneumoniae were licensed in the 1940s. The increasing emergence of antibiotic-resistant bacterial strains since the 1960s boosted the development of carbohydrate-based vaccines and led to the approval of CPS-based vaccines against Neisseria meningitidis, Haemophilus influenzae type b (Hib), and Salmonella typhi. Meanwhile, it was observed that CPS generally do not elicit protective antibody responses in children below the age of 2 years who are at the greatest risk of infection. As a consequence, studies refocused on the conjugation of oligosaccharides to proteins in order to increase vaccine immunogenicity which led to the introduction of the first glycoconjugate vaccine against Hib in 1987. Due to the success of the first glycoconjugate vaccines, higher valent formulations were developed against numerous bacterial infections to achieve broad serotype coverage. Current research also focuses on the development of carbohydrate-based vaccines against other pathogens such as viruses, fungi, protozoan parasites, or helminths.

Glycoconjugate vaccines: an update

INTRODUCTION

Globally, the three main pathogens causing serious infections are Haemophilus influenzae type b, Streptococcus pneumoniae and Neisseria meningitidis. Over the last 5 years, new vaccines protecting against these bacteria have been developed and introduced in various countries.

AREAS COVERED

This review describes the recently licensed glycoconjugates being used to protect against these encapsulated bacteria. Immunogenicity and safety data that led to licensure or licensure expansion of these glycoconjugates are discussed in addition to the resultant impact on the disease burden.

EXPERT OPINION

The maintenance of robust immunisation programmes with high uptake rates is important in maintaining low rates of disease. Epidemiological surveillance systems are essential in monitoring any changes in infectious disease trends and in identifying emerging infections such as from non-typeable H. influenzae, pneumococcal serotype replacement disease and changes in the epidemiology of meningococcal serogroups. This is important to guide future vaccine development. Accessibility of these glycoconjugate vaccines in resource poor regions, which bear the highest disease burden from these pathogens, remains challenging largely due to high vaccine pricing. Recent aids from public and private funding, tiered vaccine pricing and the transfer of vaccine technology have helped in introducing these vaccines where they are most needed.

Evaluation of swabbing methods for estimating the prevalence of bacterial carriage in the upper respiratory tract: a cross sectional study

OBJECTIVES

Bacterial carriage in the upper respiratory tract is usually asymptomatic but can lead to respiratory tract infection (RTI), meningitis and septicaemia. We aimed to provide a baseline measure of Streptococcus pneumoniae, Moraxella catarrhalis, Pseudomonas aeruginosa, Staphylococcus aureus, Haemophilus influenzae and Neisseria meningitidis carriage within the community. Self-swabbing and healthcare professional (HCP) swabbing were compared.

DESIGN

Cross-sectional study.

SETTING

Individuals registered at 20 general practitioner practices within the Wessex Primary Care Research Network South West, UK.

PARTICIPANTS

10,448 individuals were invited to participate; 5394 within a self-swabbing group and 5054 within a HCP swabbing group. Self-swabbing invitees included 2405 individuals aged 0-4 years and 3349 individuals aged ≥5 years. HCP swabbing invitees included 1908 individuals aged 0-4 years and 3146 individuals aged ≥5 years.

RESULTS

1574 (15.1%) individuals participated, 1260 (23.4%, 95% CI 22.3% to 24.5%) undertaking self-swabbing and 314 (6.2%, 95% CI 5.5% to 6.9%) undertaking HCP-led swabbing. Participation was lower in young children and more deprived practice locations. Swab positivity rates were 34.8% (95% CI 32.2% to 37.4%) for self-taken nose swabs (NS), 19% (95% CI 16.8% to 21.2%) for self-taken whole mouth swabs (WMS), 25.2% (95% CI 20.4% to 30%) for nasopharyngeal swabs (NPS) and 33.4% (95% CI 28.2% to 38.6%) for HCP-taken WMS. Carriage rates of S. aureus were highest in NS (21.3%). S. pneumoniae carriage was highest in NS (11%) and NPS (7.4%). M. catarrhalis carriage was highest in HCP-taken WMS (28.8%). H. influenzae and P. aeruginosa carriage were similar between swab types. N. meningitidis was not detected in any swab. Age and recent RTI affected carriage of S. pneumoniae and H. influenzae. Participant costs were lower for self-swabbing (£41.21) versus HCP swabbing (£69.66).

CONCLUSIONS

Higher participation and lower costs of self-swabbing as well as sensitivity of self-swabbing favour this method for use in large population-based respiratory carriage studies.

Serological and molecular capsular typing, antibiotic susceptibility of Streptococcus pneumoniae isolates from invasive and non-invasive infections

Streptococcus pneumoniae causes life threatening infections and necessitate for impediment and controlling disease; to conquer this, information is needed about serotype distribution and patterns of antibiotic resistance. The present study was to determine the serotype distribution of S. pneumoniae isolated from the entire age group individual and to correlate this distribution with susceptibility. Cases of pneumococcal infections have been reviewed for serotyping and antibiotic susceptibility. Out of 117 pneumococcal isolates 45 (39%) were penicillin-resistant, 84 (72%) were erythromycin-resistant and 100% were co-trimoxazole resistant. The most frequently isolated serotypes were 23F, 19F, 14, 6B, 5, 6A, 19A and 9V. PCV7, PCV10 and PCV13 coverage was 68%, 79%, 87%, respectively. Similarly, there was similarity in PCV7 coverage for non invasive isolates (64.5%) and invasive isolates (72.2%). The study state that common pneumococcal serotypes were present in similar ways as reported in literature. A continuous survey of pneumococcal infected population is requirement and necessity for success of vaccination.