Systematic review of the clinical development of group B streptococcus serotype-specific capsular polysaccharide-based vaccines

Using Surface Immunogenic Protein as a Carrier Protein to Elicit Protective Antibody to Multiple Serotypes for Candidate Group B Streptococcal Glycan Conjugate Vaccines

Group B Streptococcus (GBS) is a life-threatening opportunistic pathogen, particularly in pregnant women, infants, and the elderly. Currently, maternal vaccination is considered the most viable long-term option for preventing GBS mother-to-infant infection, and two polysaccharide conjugate vaccines utilizing CRM197 as a carrier protein have undergone clinical phase II trials. Surface immunogenic protein (Sip), present in all identified serotypes of GBS strains so far, is a protective surface protein of GBS. In this study, the type Ia capsular polysaccharide (CPS) of GBS was utilized as a model to develop candidate antigens for a polysaccharide conjugate vaccine by coupling it with the Sip of GBS and the traditional carrier protein CRM197. Serum analysis from immunized New Zealand rabbits and CD1 mice revealed that there was no significant difference in antibody titers between the Ia-Sip group and Ia-CRM197 group; however, both were significantly higher than those observed in the Ia polysaccharide group. Opsonophagocytosis and passive immune protection results using rabbit serum indicated no significant difference between the Ia-Sip and Ia-CRM197 groups, both outperforming the Ia polysaccharide group. Furthermore, serum from the Ia-Sip group had a cross-protective effect on multiple types of GBS strains. The challenge test results in CD1 mice demonstrated that the Ia-Sip group provided complete protection against lethal doses of bacteria and also showed cross-protection against type III strain. Our study demonstrates for the first time that Ia-Sip is immunogenic and provides serotype-independent protection in glycan conjugate vaccines, which also indicates Sip may serve as an excellent carrier protein for GBS glycan conjugate vaccines and provide cross-protection against multiple GBS strains.

Development of risk prediction nomogram for neonatal sepsis in Group B Streptococcus-colonized mothers: a retrospective study

Neonatal clinical sepsis is recognized as a significant health problem, This study sought to identify a predictive model of risk factors for clinical neonatal sepsis. A retrospective study was conducted from 1 October 2018 to 31 March 2023 in a large tertiary hospital in China. Neonates were divided into patients and controls based on the occurrence of neonatal sepsis. A multivariable model was used to determine risk factors and construct models.The utilization and assessment of model presentation were conducted using Norman charts and web calculators, with a focus on model differentiation, calibration, and clinical applicability (DCA). Furthermore, the hospital's data from 1 April 2023 to 1 January 2024 was utilized for internal validation. In the modelling dataset, a total of 339 pairs of mothers and their newborns were included in the study and divided into two groups: patients (n = 84, 24.78%) and controls (n = 255, 75.22%). Logistic regression analysis was performed to examine the relationship between various factors and outcome. The results showed that maternal age < 26 years (odds ratio [OR] = 2.16, 95% confidence interval [CI] 1.06-4.42, p = 0.034), maternal gestational diabetes (OR = 2.17, 95% CI 1.11-4.27, p = 0.024), forceps assisted delivery (OR = 3.76, 95% CI 1.72-5.21, p = 0.032), umbilical cord winding (OR = 1.75, 95% CI 1.32-2.67, p = 0.041) and male neonatal sex (OR = 1.59, 95% CI 1.00-2.62, p = 0.050) were identified as independent factors influencing the outcome of neonatal clinical sepsis. A main effects model was developed incorporating these five significant factors, resulting in an area under the curve (AUC) value of 0.713 (95% CI 0.635-0.773) for predicting the occurrence of neonatal clinical sepsis. In the internal validation cohort, the AUC value of the model was 0.711, with a 95% CI of 0.592-0.808. A main effects model incorporating the five significant factors was constructed to help healthcare professionals make informed decisions and improve clinical outcomes.

Early-onset group B streptococcal disease in African countries and maternal vaccination strategies

Invasive group B streptococcal (GBS) disease is the commonest perinatally-acquired bacterial infection in newborns; the burden is higher in African countries where intrapartum antibiotic prophylaxis strategies are not feasible. In sub-Saharan Africa, almost one in four newborns with GBS early-onset disease will demise, and one in ten survivors have moderate or severe neurodevelopmental impairment. A maternal GBS vaccine to prevent invasive GBS disease in infancy is a pragmatic and cost-effective preventative strategy for Africa. Hexavalent polysaccharide protein conjugate and Alpha family surface protein vaccines are undergoing phase II clinical trials. Vaccine licensure may be facilitated by demonstrating safety and immunological correlates/thresholds suggestive of protection against invasive GBS disease. This will then be followed by phase IV effectiveness studies to assess the burden of GBS vaccine preventable disease, including the effect on all-cause neonatal infections, neonatal deaths and stillbirths.

Gamma-Irradiated Non-Capsule Group B Streptococcus Promotes T-Cell Dependent Immunity and Provides a Cross-Protective Reaction

Group B Streptococcus (GBS) is a Gram-positive bacterium commonly found in the genitourinary tract and is also a leading cause of neonatal sepsis and pneumonia. Despite the current antibiotic prophylaxis (IAP), the disease burdens of late-onset disease in newborns and non-pregnant adult infections are increasing. Recently, inactivation of the pathogens via gamma radiation has been proven to eliminate their replication ability but cause less damage to the antigenicity of the key epitopes. In this study, the non-capsule GBS strain was inactivated via radiation (Rad-GBS) or formalin (Che-GBS), and we further determined its immunogenicity and protective efficacy as vaccines. Notably, Rad-GBS was more immunogenic and gave rise to higher expression of costimulatory molecules in BMDCs in comparison with Che-GBS. Flow cytometric analysis revealed that Rad-GBS induced a stronger CD4+ IFN-γ+ and CD4+IL-17A+ population in mice. The protective efficacy was measured through challenge with the highly virulent strain CNCTC 10/84, and the adoptive transfer results further showed that the protective role is reversed by functionally neutralizing antibodies and T cells. Finally, cross-protection against challenges with prevalent serotypes of GBS was induced by Rad-GBS. The higher opsonophagocytic killing activity of sera against multiple serotypes was determined in sera from mice immunized with Rad-GBS. Overall, our results showed that the inactivated whole-cell encapsulated GBS could be an alternative strategy for universal vaccine development against invasive GBS infections.

Serotype Distribution, Virulence Determinants and Antimicrobial Susceptibility of Streptococcus agalactiae Isolated from Young Infants

Background: Streptococcus agalactiae (Group B Streptococcus, GBS) is the most common cause of serious infections in the first 3 months of life worldwide. The pathogenicity of GBS is closely related to serotypes, surface proteins and virulence factors, and the distribution of them may vary temporally and geographically. However, data related to GBS surface proteins and virulence determinants in China are very few. The aim of this study is to investigate the genetic characteristics of clinical GBS isolates from infected infants. Methods: We recovered GBS isolates from infected infants younger than 3 months during 2017−2021 at Maternal and Child Health Hospital of Hubei Province in China. We assessed the GBS serotypes, surface proteins, virulence determinants and antibiotic resistance genes distribution, by Multilocus sequence typing (MLST) and whole-genome sequencing analysis. Results: Among 97 isolates (81 EOD and 16 LOD), 5 serotypes were detected. Serotype III was the most represented (49.5%), followed by type Ib (20.6%). The isolates belonged to 17 different sequence types (STs) that grouped into the 8 clonal complexes (CCs). The most frequently identified ST was ST17 (23.7%). The most predominant surface protein of alpha-protein-like (alp) family (one of the protein components of the GBS surface antigen, resistant to trypsin) present was Rib (41.2%), which was mainly detected in serotype III. The srr1, which encodes Srr1 protein, was identified in 54.6% of isolates. The hvgA encoding for hypervirulent GBS adhesin can be detected in all 24 serotype III GBS. Among the pilus islands genes, 50% and 58.8% of the isolates were positive for pi-1 and pi-2a genes, respectively. The presence of pi-2b was mainly associated with serotype III/CC17 strains; 56.7% of isolates carried tetM, tetO/tetL, ermB antibiotic resistant genes. Among all the virulence genes detected, the cfb-cylE-lmb-pavA pattern was the main virulence gene profile (81.4%), mainly in serotype III/CC17. Conclusions: The whole genomic sequencing data revealed the high variation in surface proteins, determining virulence and antibiotic resistance in clinical isolates from 97 GBS infected infants. These data provide insightful characteristics of genetic features of GBS. Constant epidemiological surveillance is warranted to provide information on the GBS pathogenic dynamics and antibiotic resistance profiles in the surveyed areas for improving therapeutic outcomes.

Changes in Group B Streptococcus Colonization among Pregnant Women before and after the Onset of the COVID-19 Pandemic in Brazil

Group B Streptococcus (GBS) is a leading cause of neonatal infections. The genitourinary and gastrointestinal tract of pregnant women are the main source of transmission to newborns. This work investigated the prevalence and characterized GBS from pregnant women in Rio de Janeiro, Brazil, comparing the periods before (January 2019 to March 2020; 521) and during (May 2020 to March 2021; 285) the COVID-19 pandemic. GBS was detected in 10.8% of anovaginal samples. Considering scenarios before and during the pandemic, GBS colonization rate significantly decreased (13.8% vs. 5.3%; p = 0.0001). No clinical and sociodemographic aspect was associated with GBS carriage (p > 0.05). A total of 80%, 13.8% and 4.6% GBS strains were non-susceptible to tetracycline, erythromycin and clindamycin, respectively. Serotype Ia was the most frequent (47.7%), followed by V (23.1%), II (18.4%), III (7.7%) and Ib (3.1%). An increasing trend of serotypes Ib and V, as well as of antimicrobial resistance rates, and a decreasing trend of serotypes II and III, were observed after the pandemic onset, albeit not statistically significant (p > 0.05). The reduction in GBS colonization rates and alterations in GBS serotypes and resistance profiles during the pandemic were not due to changes in the sociodemographic profile of the population. Considering that control and preventive measures related to the COVID-19 pandemic onset have impacted other infectious diseases, these results shed light on the need for the continuous surveillance of GBS among pregnant women in the post-pandemic era.

Impact of industry sponsorship on the quality of systematic reviews of vaccines: a cross-sectional analysis of studies published from 2016 to 2019

BACKGROUND

Systematic reviews (SRs) provide the highest level of evidence and inform evidence-based decision making in health care. Earlier studies found association with industry to be negatively associated with methodological quality of SRs. However, this has not been investigated in SRs on vaccines.

METHODS

We performed a systematic literature search using MEDLINE and EMBASE in March 2020. The results were restricted to those published between 2016 and 2019 with no language restrictions. Study characteristics were extracted by one person and checked by an experienced reviewer. The methodological quality of the SRs was assessed with the AMSTAR 2 tool by multiple reviewers after a calibration exercise was performed. A summary score for each SR was calculated. The Mann-Whitney U test and Fisher's exact test were performed to compare both groups.

RESULTS

Out of 185 SRs that met all inclusion criteria, 27 SRs were industry funded. Those were matched with 30 non-industry funded SRs resulting in a total sample size of 57. The mean AMSTAR 2 summary score across all SRs was 0.49. Overall, the median AMSTAR 2 summary score was higher for the non-industry funded SRs than for the industry-funded SRs (0.62 vs. 0.36; p < .00001). Lower ratings for industry funded SRs were consistent across all but one AMSTAR 2 item, though significantly lower only for three specific items.

CONCLUSION

The methodological quality of SRs in vaccination is comparable to SRs in other fields, while it is still suboptimal. We are not able to provide a satisfactory explanation why industry funded SRs had a lower methodological quality than non-industry funded SRs over recent years. Industry funding is an important indicator of methodological quality for vaccine SRs and should be carefully considered when appraising SR quality.

Late-onset Group B Streptococcus Bacteremia Evaluated in the Pediatric Emergency Department and Risk Factors for Severe Infection

BACKGROUND

To describe the infants presenting to pediatric emergency departments (PEDs) and diagnosed with group B Streptococcus (GBS) late-onset disease (LOD) bacteremia and identify risk factors for severe infection and pediatric intensive care unit (PICU) admission.

METHODS

Observational study and subanalysis of a multicenter prospective registry. Setting: pediatric emergency department. Inclusion criteria: infants between 7 and 89 days of age with positive blood culture for GBS seen between 2011 and 2016 at any of 22 Spanish PEDs. Main outcome: risk factors (clinical and laboratory variables) for severe infection (sepsis/septic shock or meningitis) and PICU admission. Second, the prevalence of poor outcomes (acute complications, sequelae or death).

RESULTS

Among 118 patients with LOD, 74 (62.7%) presented a severe infection: 66 sepsis/septic shock (11 with associated meningitis) and 8 meningitis. Thirty-five patients (29.7%) were admitted to a PICU. An altered Pediatric Assessment Triangle (PAT) upon arrival and leukopenia were the only independent risk factors for severe infection [odds ratio (OR): 43.6; 95% confidence interval (CI): 8.1-235.7, P < 0.01] and PICU admission (OR: 11.6; 95% CI: 1.5-91.4; P < 0.019), respectively. Six patients (5.1%) developed a poor outcome, including 2 deaths (1.7%); all had an altered PAT, elevated procalcitonin (range 4.7-100 ng/ml), and were diagnosed with sepsis/septic shock and admitted to a PICU. Four developed leukopenia.

CONCLUSIONS

Infants with GBS LOD frequently develop sepsis/septic shock and bacterial meningitis, associated with non-negligible morbidity and mortality. Clinical appearance was the only risk factor for severe infection, whereas leukopenia was related to PICU admission.

Transmission of Group B Streptococcus in late-onset neonatal disease: a narrative review of current evidence

Group B streptococcus (GBS) late-onset disease (LOD, occurring from 7 through 89 days of life) is an important cause of sepsis and meningitis in infants. The pathogenesis and modes of transmission of LOD to neonates are yet to be elucidated. Established risk factors for the incidence of LOD include maternal GBS colonisation, young maternal age, preterm birth, HIV exposure and African ethnicity. The mucosal colonisation by GBS may be acquired perinatally or in the postpartum period from maternal or other sources. Growing evidence has demonstrated the predominant role of maternal sources in the transmission of LOD. Intrapartum antibiotic prophylaxis (IAP) to prevent early-onset disease reduces neonatal GBS colonisation during delivery; however, a significant proportion of IAP-exposed neonates born to GBS-carrier mothers acquire the pathogen at mucosal sites in the first weeks of life. GBS-infected breast milk, with or without presence of mastitis, is considered a potential vehicle for transmitting GBS. Furthermore, horizontal transmission is possible from nosocomial and other community sources. Although unfrequently reported, nosocomial transmission of GBS in the neonatal intensive care unit is probably less rare than is usually believed. GBS disease can sometime recur and is usually caused by the same GBS serotype that caused the primary infection. This review aims to discuss the dynamics of transmission of GBS in the neonatal LOD.

Applicability of the GAIA Maternal and Neonatal Outcome Case Definitions for the Evaluation of Adverse Events Following Vaccination in Pregnancy in High-income Countries

BACKGROUND

The Brighton Collaboration Global Alignment of Immunization Safety in Pregnancy (GAIA) project developed case definitions for the assessment of adverse events in mothers and infants following maternal immunization. This study evaluated the applicability of these definitions to data collected in routine clinical care and research trial records across 7 sites in high-resource settings.

METHODS

Data collection forms were designed and used to retrospectively abstract the key elements of the GAIA definitions from records for 5 neonatal and 5 maternal outcomes, as well as gestational age. Level of diagnostic certainty was assessed by the data abstractor and an independent clinician, and then verified by Automated Brighton Case logic. The ability to assign a level of diagnostic certainty for each outcome and the positive predictive value (PPV) for their respective ICD-10 codes were evaluated.

RESULTS

Data from 1248 case records were abstracted: 624 neonatal and 622 maternal. Neonatal outcomes were most likely to be assessable and assigned by the level of diagnostic certainty. PPV for preterm birth, low birth weight, small for gestational age and respiratory distress were all above 75%. Maternal outcomes for preeclampsia and fetal growth restriction showed PPV over 80%. However, microcephaly (neonatal outcome) and dysfunctional labor (maternal outcome) were often nonassessable, with low PPVs.

CONCLUSIONS

The applicability of GAIA case definitions to retrospectively ascertain and classify maternal and neonatal outcomes was variable among sites in high-resource settings. The implementation of the case definitions is largely dependent on the type and quality of documentation in clinical and research records in both high- and low-resource settings. While designed for use in the prospective evaluation of maternal vaccine safety, the GAIA case definitions would likely need to be specifically adapted for observational studies using alternative sources of data, linking various data sources and allowing flexibility in the ascertainment of the elements and levels of certainty of the case definition.

Updates in prevention policies of early-onset group B streptococcal infection in newborns

Invasive disease owing to group B Streptococcus (GBS) is a major cause of illness and death among newborns. Maternal GBS colonization of gastrointestinal tract and/or vagina is the primary risk factor for neonatal GBS early-onset disease (EOD). In Europe and America, there are marked declines in neonatal GBS-EOD through widespread implementation of guidelines for maternal GBS screening and subsequent intrapartum antibiotic prophylaxis (IAP). The key measures necessary for prevention of GBS-EOD include correct specimen collection and processing, nucleic acid amplification testing (NAAT) for GBS identification, regimens for mothers with premature rupture of membranes (PROM), preterm labor or penicillin allergy, and coordination between obstetrics and pediatrics. Antibiotic prophylaxis has some disadvantages, so researchers should develop other preventive measures. Maternal vaccines to prevent perinatal GBS infection are currently under development. However, as large, population-based sampling studies are rarely conducted, the colonization rate and the disease burden of GBS in perinatal period are poorly understood in developing countries. The harm of GBS to newborns has been recognized in recent years in mainland China, but authorized prevention measures are still lacking. In order to enhance the understanding of GBS-EOD prevention, the most recent guidelines updates by the American College of Obstetricians and Gynecologists (ACOG) and American Academy of Pediatrics (AAP) in 2019-2020 are summarized in this article.

Retrospective analysis of neonatal deaths secondary to infections in England and Wales, 2013-2015

OBJECTIVE

To estimate the overall and infection-related neonatal mortality rate and the pathogens responsible using electronic death registrations.

DESIGN

Retrospective analysis of national electronic death registrations data.

SETTING

England and Wales.

PATIENTS

Neonates aged <28 days.

MAIN OUTCOME MEASURES

Overall and infection-related mortality rate per 1000 live births in term, preterm (28-36 weeks) and extremely preterm (<28 weeks) neonates; the contribution of infections and specific pathogens; comparison with mortality rates in 2003-2005.

RESULTS

The neonatal mortality rate during 2013-2015 (2.4/1000 live births; 5095 deaths) was 31% lower than in 2003-2005 (3.5/1000; 6700 deaths). Infection-related neonatal mortality rate in 2013-2015 (0.32/1000; n=669) was 20% lower compared with 2003-2015 (0.40/1000; n=768), respectively. Infections were responsible for 13.1% (669/5095) of neonatal deaths during 2013-2015 and 11.5% (768/6700) during 2003-2005. Of the infection-related deaths, 44.2% (296/669) were in term, 19.9% (133/669) preterm and 35.9% (240/669) extremely preterm neonates. Compared with term infants (0.15/1000 live births), infection-related mortality rate was 5.9-fold (95% CI 4.7 to 7.2) higher in preterm (0.90/1000) and 188-fold (95% CI 157 to 223) higher in extremely preterm infants (28.7/1000) during 2013-2015. A pathogen was recorded in 448 (67%) registrations: 400 (89.3%) were bacterial, 37 (8.3%) viral and 11 (2.4%) fungal. Group B streptococcus (GBS) was reported in 30.4% (49/161) of records that specified a bacterial infection and 7.3% (49/669) of infection-related deaths.

CONCLUSIONS

Overall and infection-related neonatal mortality rates have declined, but the contribution of infection and of specific pathogens has not changed. Further preventive measures, including antenatal GBS vaccine may be required to prevent the single most common cause of infection-related deaths in neonates.

Polysaccharide Chemistry in Drug Delivery, Endocrinology, and Vaccines

Polysaccharides, due to their outstanding properties, have attracted the attention of researchers, working in the biomedical field and especially of those working in drug delivery. Modified/functionalized polysaccharides further increase the importance for various applications. Delivery of therapeutics for diverse ailments in different endocrine glands and hormones safely, is a focal point of researchers working in the field. Among the routes followed, the transdermal route is preferred due to non-exposure of active moieties to the harsh gastric environment and first-pass metabolism. This review starts with the overview of polysaccharides used for the delivery of various therapeutic agents. Advantages of polysaccharides used in the transdermal route are addressed in detail. Types of polysaccharides will be elaborated through examples, and in this context, special emphasis will be on the polysaccharides being used for synthesis of the membranes/films. Techniques employed for their modification to design novel carriers for therapeutics delivery will also be discussed. The review will end with a brief discussion on recent developments and future perspectives for delivery of therapeutic agents, and vaccine development.

Invasive Bacterial Infections in Subjects with Genetic and Acquired Susceptibility and Impacts on Recommendations for Vaccination: A Narrative Review

The WHO recently endorsed an ambitious plan, “Defeating Meningitis by 2030”, that aims to control/eradicate invasive bacterial infection epidemics by 2030. Vaccination is one of the pillars of this road map, with the goal to reduce the number of cases and deaths due to Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae and Streptococcus agalactiae. The risk of developing invasive bacterial infections (IBI) due to these bacterial species includes genetic and acquired factors that favor repeated and/or severe invasive infections. We searched the PubMed database to identify host risk factors that increase the susceptibility to these bacterial species. Here, we describe a number of inherited and acquired risk factors associated with increased susceptibility to invasive bacterial infections. The burden of these factors is expected to increase due to the anticipated decrease in cases in the general population upon the implementation of vaccination strategies. Therefore, detection and exploration of these patients are important as vaccination may differ among subjects with these risk factors and specific strategies for vaccination are required. The aim of this narrative review is to provide information about these factors as well as their impact on vaccination against the four bacterial species. Awareness of risk factors for IBI may facilitate early recognition and treatment of the disease. Preventive measures including vaccination, when available, in individuals with increased risk for IBI may prevent and reduce the number of cases.

Genomic characteristics of Streptococcus agalactiae based on the pan-genome orthologous group analysis according to invasiveness and capsular genotype

OBJECTIVE

Following the construction of a bacterial pan-genome from the whole genome sequences on a web-based pipeline, all coding DNA sequences (CDSs) can be clustered into pan-genome orthologous groups (POGs), which is a similar approach to comparative genome hybridization on glass microscope slides. We aimed to clarify the genomic characteristics of Streptococcus agalactiae based on the POG analysis.

METHODS

Sixty-six S. agalactiae isolates obtained from invasive specimens (blood and cerebrospinal fluid) and non-invasive specimens (urine and vaginal discharge) between 2010 and 2017 in Korea were subjected to whole genome sequencing (WGS). Based on the WGS data, we conducted the POG analysis and constructed a phylogenetic tree along with capsular polysaccharide (CPS) genotyping. We compared the genomics of invasive vs. non-invasive isolates, as well as CPS III vs. non-CPS III genotypes.

RESULTS

Predicted pan- and core-genome sizes were 3416 and 1658 genes, respectively. We found four clusters consisting of CPS genotypes (III, VIII, Ib/VI, and Ia) in the phylogenetic tree. There were significant differences in two metabolic pathways specific to invasiveness, and in six metabolic pathways specific to CPS III type produced by CDSs.

CONCLUSION

Our observations reveal the pan- and core-genome sizes, four clusters of genomes distributed by CPS genotypes, and unique CDS features of S. agalactiae by comparative genomics in terms of invasiveness and CPS genotype.

Safety and Immunogenicity of a Second Dose of an Investigational Maternal Trivalent Group B Streptococcus Vaccine in Nonpregnant Women 4-6 Years After a First Dose: Results From a Phase 2 Trial

Background

Maternal immunization against group B streptococcus (GBS) could protect infants from invasive GBS disease. Additional doses in subsequent pregnancies may be needed. We evaluated the safety and immunogenicity of a second dose of an investigational trivalent CRM₁₉₇-glycoconjugate GBS vaccine (targeting serotypes Ia/Ib/III), administered to nonpregnant women 4–6 years postdose 1.

Methods

Healthy women either previously vaccinated with 1 dose of trivalent GBS vaccine 4–6 years before enrollment (n = 53) or never GBS vaccinated (n = 27) received a single trivalent GBS vaccine injection. Adverse events (AEs) were recorded. Serotype-specific (Ia/Ib/III) anti-GBS antibodies were measured by multiplex immunoassay prevaccination and 30/60 days postvaccination.

Results

AEs were reported with similar rates after a first or second dose; none were serious. Of previously GBS-vaccinated women, 92%–98% had anti-GBS concentrations that exceeded an arbitrary threshold (8 µg/mL) for each serotype 60 days postdose 2 vs 36%–56% postdose 1 in previously non–GBS-vaccinated women. Of previously GBS-vaccinated women with undetectable baseline (predose 1) anti-GBS levels, 90%–98% reached this threshold postdose 2. For each serotype, anti-GBS geometric mean concentrations (GMCs) 30/60 days postdose 2 in previously GBS-vaccinated women were ≥200-fold higher than baseline GMCs. Among women with undetectable baseline anti-GBS levels, postdose 2 GMCs in previously GBS-vaccinated women exceeded postdose 1 GMCs in previously non–GBS-vaccinated women (≥7-fold).

Conclusions

A second trivalent GBS vaccine dose administered 4–6 years postdose 1 was immunogenic with a favorable safety profile. Women with undetectable preexisting anti-GBS concentrations may benefit from a sufficiently spaced second vaccine dose.

Clinical Trials Registration

NCT02690181

Protection of the Newborn Through Vaccination in Pregnancy

Newborns and infants are at risk for severe infections with some pathogens (eg, Bordetella pertussis, influenza, respiratory syncytial virus, group B Streptococcus) during early life. To decrease this window of high susceptibility to some infections during early life and protect young infants, vaccination in pregnancy against some vaccine-preventable diseases (eg, influenza, pertussis, tetanus) has been recommended in an increasing number of countries with notable success. In addition, recent advances have been made in developing vaccines for pregnant women with the aim of reducing the respiratory syncytial virus and group B Streptococcus burden in infancy. In this article, we review the vaccines currently recommended during pregnancy and their benefits to newborns and infants. We also discuss progress made in the development of other vaccines that are expected to be evaluated in pregnant women in the near future.

Stratified Management for Bacterial Infections in Late Preterm and Term Neonates: Current Strategies and Future Opportunities Toward Precision Medicine

Bacterial infections remain a major cause of morbidity and mortality in the neonatal period. Therefore, many neonates, including late preterm and term neonates, are exposed to antibiotics in the first weeks of life. Data on the importance of inter-individual differences and disease signatures are accumulating. Differences that may potentially influence treatment requirement and success rate. However, currently, many neonates are treated following a "one size fits all" approach, based on general protocols and standard antibiotic treatment regimens. Precision medicine has emerged in the last years and is perceived as a new, holistic, way of stratifying patients based on large-scale data including patient characteristics and disease specific features. Specific to sepsis, differences in disease susceptibility, disease severity, immune response and pharmacokinetics and -dynamics can be used for the development of treatment algorithms helping clinicians decide when and how to treat a specific patient or a specific subpopulation. In this review, we highlight the current and future developments that could allow transition to a more precise manner of antibiotic treatment in late preterm and term neonates, and propose a research agenda toward precision medicine for neonatal bacterial infections.

Safety and immunogenicity of an investigational maternal trivalent group B streptococcus vaccine in pregnant women and their infants: Results from a randomized placebo-controlled phase II trial

BACKGROUND

This study evaluated the safety and immunogenicity of an investigational trivalent group B streptococcus (GBS) vaccine in US pregnant women, transplacental serotype-specific antibody transfer and persistence in infants, and serotype-specific antibodies in breast milk.

METHODS

This randomized, observer-blind, placebo-controlled trial administered one dose of trivalent GBS vaccine (n = 49) or placebo (n = 26) to healthy pregnant 18-40-year-old women at 24^0/7-34^6/7 weeks' gestation. Women were enrolled from March 2014 to August 2015. Safety follow-up continued through postpartum day 180. Primary immunogenicity objectives were to evaluate serotype Ia/Ib/III-specific immunoglobulin G (IgG) levels in sera from women on day 1 (pre-vaccination), day 31, delivery and postpartum days 42 and 90, and from infants at birth (cord blood), days 42 and 90. Antibody transfer ratios (cord blood/maternal sera at delivery) and serotype-specific secretory immunoglobulin A (sIgA) and IgG in breast milk after delivery and on postpartum days 42 and 90 were evaluated. The planned sample size was not based on statistical assumptions for this descriptive study.

RESULTS

Baseline characteristics were similar between groups. Serious adverse events were reported for 16% of GBS-vaccinated women and 15% of their infants, and 15% of placebo recipients and 12% of their infants; none were fatal or deemed vaccine-related. Serotype-specific IgG geometric mean concentrations (GMCs) were 13-23-fold higher in vaccine vs placebo recipients on day 31 and persisted until postpartum day 90. Median antibody concentrations were substantially higher in women with detectable pre-vaccination antibody concentrations. Antibody transfer ratios in the vaccine group were 0.62-0.82. Infant IgG GMCs and breast milk sIgA GMCs were higher in the vaccine vs the placebo group at all timepoints.

CONCLUSIONS

Maternal immunization with the trivalent GBS vaccine in US women had a favorable safety profile, elicited antibodies that were transplacentally transferred and persisted in infants for a minimum of 3 months.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov, NCT02046148.

Global Perspectives on Immunization During Pregnancy and Priorities for Future Research and Development: An International Consensus Statement

Immunization during pregnancy has been recommended in an increasing number of countries. The aim of this strategy is to protect pregnant women and infants from severe infectious disease, morbidity and mortality and is currently limited to tetanus, inactivated influenza, and pertussis-containing vaccines. There have been recent advancements in the development of vaccines designed primarily for use in pregnant women (respiratory syncytial virus and group B Streptococcus vaccines). Although there is increasing evidence to support vaccination in pregnancy, important gaps in knowledge still exist and need to be addressed by future studies. This collaborative consensus paper provides a review of the current literature on immunization during pregnancy and highlights the gaps in knowledge and a consensus of priorities for future research initiatives, in order to optimize protection for both the mother and the infant.

Galleria mellonella as an infection model for the multi-host pathogen Streptococcus agalactiae reflects hypervirulence of strains associated with human invasive disease

Streptococcus agalactiae, or group B Streptococcus (GBS), infects diverse hosts including humans and economically important species such as cattle and fishes. In the context of human health, GBS is a major cause of neonatal infections and an emerging cause of invasive disease in adults and of foodborne disease in Southeast Asia. Here we show that GBS is able to establish a systemic infection in Galleria mellonella larvae that is associated with extensive bacterial replication and dose-dependent larval survival. This infection model is suitable for use with GBS isolates from both homeothermic and poikilothermic hosts. Hypervirulent sequence types (ST) associated with invasive human disease in neonates (ST17) or adults (ST283) show increased virulence in this model, indicating it may be useful in studying GBS virulence determinants, albeit with limitations for some host-specific virulence factors. In addition, we demonstrate that larval survival can be afforded by antibiotic treatment and so the model may also be useful in the development of novel anti-GBS strategies. The use of G. mellonella in GBS research has the potential to provide a low-cost infection model that could reduce the number of vertebrates used in the study of GBS infection.

High Rate of Serotype V Streptococcus agalactiae Carriage in Pregnant Women in Botswana

Maternal rectovaginal colonization is the major risk factor for early-onset neonatal sepsis due to Group B Streptococcus (GBS), a major cause of early life morbidity and mortality. Transmission generally occurs perinatally from colonized mothers to infants. Vaccines targeting a subset of GBS serotypes are under development, but GBS epidemiology remains poorly understood in many African nations. We performed a cross-sectional study of GBS colonization among pregnant women at two sites in Botswana, a country with minimal prior GBS carriage data. We found a rectovaginal colonization rate of 19%, comparable with studies in other regions; however, we also noted a striking predominance of serotype V (> 45% of strains). Although further studies are required to delineate the burden of invasive GBS disease in Botswana and the generalizability of type V epidemiology, these data provide a useful baseline for understanding the potential local impact of GBS prevention strategies, including vaccines.

Group B Streptococcus serotypes Ia and V induce differential vaginal immune responses that may contribute to long term colonization of the female reproductive tract

PROBLEM

Group B Streptococcus (GBS) is a common colonizer of the female genital tract at the time of pregnancy and has been associated with severe neonatal infections. Despite trials for GBS vaccines already being underway, the factors influencing vaginal GBS colonization and clearance are currently poorly understood.

METHOD OF STUDY

Within this study, we investigated the host immune responses to GBS infections in mice that affect GBS vaginal colonization and clearance. Cervicovaginal swabs were used to measure vaginal GBS persistence, and vaginal cytokine responses were measured using the BioPlex^® system. Lymphocytes isolated from spleens were stimulated with UV-killed GBS to examine systemic cellular responses. Additional in vitro cellular experiments using human vaginal epithelial cells were also performed, examining the effect pregnancy level hormones had on GBS adhesion, invasion, and cytokine responses.

RESULTS

We observed significant differences in the ability of GBS serotype V infections to persist, compared with GBS serotype Ia vaginal infections. Vaginal cytokine response examination identified temporal changes in cytokine production (IL10, IFNγ, IL6, IL1β, and TNFα) in relation to GBS serotype and clearance or colonization. Lymphocyte proliferation assays also revealed robust cellular immune responses to GBS vaginal infections irrespective of clearance or colonization. In vitro human cellular analyses also identified that vaginal epithelial cell line cytokine production was suppressed in the presence of hormones despite no alteration in adhesion/invasion.

CONCLUSION

Here, we establish previously unknown, serotype specific, temporal immune responses which may be associated with vaginal GBS colonization or clearance in the female genital tract.

Management of Infants at Risk for Group B Streptococcal Disease

Group B streptococcal (GBS) infection remains the most common cause of neonatal early-onset sepsis and a significant cause of late-onset sepsis among young infants. Administration of intrapartum antibiotic prophylaxis is the only currently available effective strategy for the prevention of perinatal GBS early-onset disease, and there is no effective approach for the prevention of late-onset disease. The American Academy of Pediatrics joins with the American College of Obstetricians and Gynecologists to reaffirm the use of universal antenatal microbiologic-based testing for the detection of maternal GBS colonization to facilitate appropriate administration of intrapartum antibiotic prophylaxis. The purpose of this clinical report is to provide neonatal clinicians with updated information regarding the epidemiology of GBS disease as well current recommendations for the evaluation of newborn infants at risk for GBS disease and for treatment of those with confirmed GBS infection. This clinical report is endorsed by the American College of Obstetricians and Gynecologists (ACOG), July 2019, and should be construed as ACOG clinical guidance.