Safety and immunogenicity of a prototype recombinant alpha-like protein subunit vaccine (GBS-NN) against Group B Streptococcus in a randomised placebo-controlled double-blind phase 1 trial in healthy adult women

Virulence and pathogenicity of group B Streptococcus: Virulence factors and their roles in perinatal infection

This review summarizes key virulence factors associated with group B Streptococcus (GBS), a significant pathogen particularly affecting pregnant women, fetuses, and infants. Beginning with an introduction to the historical transition of GBS from a zoonotic pathogen to a prominent cause of human infections, particularly in the perinatal period, the review describes major disease manifestations caused by GBS, including sepsis, meningitis, chorioamnionitis, pneumonia, and others, linking each to specific virulence mechanisms. A detailed exploration of the genetic basis for GBS pathogenicity follows, emphasizing the roles of capsules in pathogenesis and immune evasion. The paper also examines the molecular structures and functions of key GBS surface proteins, such as pili, serine-rich repeat proteins, and fibrinogen-binding proteins, which facilitate colonization and disease. Additionally, the review discusses the significance of environmental sensing and response systems, like the two-component systems, in adapting GBS to different host environments. We conclude by addressing current efforts in vaccine development, underscoring the need for effective prevention strategies against this pervasive pathogen.

Clinical and regulatory development strategies for GBS vaccines intended for maternal immunisation in low- and middle-income countries

Group B Streptococcus (GBS) is a leading cause of infant mortality, particularly in low- and middle-income countries (LMICs). Several maternal GBS vaccine candidates, aimed at protecting infants, are progressing through clinical trials. The World Health Organisation (WHO) aims to ensure equitable access to safe, effective, and affordable vaccines of assured quality in LMICs, by facilitating regulatory pathways. An alternate approval pathway, based on safety and an immunological endpoint thought to predict clinical benefit (commonly referred to as serological threshold of risk reduction [SToRR]), is being considered for GBS maternal vaccines. Since this approach is new to many LMICs regulators and policymakers, WHO organized consultative meetings at national, regional, and global levels to discuss the feasibility and potential challenges of approving a GBS vaccine based on safety and immunogenicity data alone. These consultations focused on evidence supporting SToRR, their use as endpoints to infer protection, and post-licensure requirements. The aim of the consultations was to reduce the delay between vaccine development, licensure, policy recommendations and use in high-burden LMICs.

Association of serum anti-gbs2106 protein immunoglobulin G (IgG) in newborns and risk reduction of invasive group B streptococcus disease during early infancy

BACKGROUND

Human immunoglobulin G (IgG) directed against Group B streptococcus (GBS) epitopes is transferred transplacentally from the mother to the fetus. A GBS putative protein, gbs2106, has been previously identified as a potential GBS protein antigen vaccine candidate. However, its genetic prevalence and surface expression in GBS-isolates has not been evaluated. In this study, we evaluated the prevalence, surface expression and association of maternal-acquired serum anti-gbs2106 IgG in newborns and risk reduction of infant invasive GBS disease through to 90 days of age in a South African-based cohort.

METHODS

We conducted a nested case-control study within a previously established birth cohort that was designed to investigate serological markers associated with risk reduction of invasive GBS disease. In the parent study, additional cases were identified through a hospital surveillance system which included infants diagnosed with culture-confirmed invasive GBS disease outside the original cohort study. In this current study, surface expression of gbs2106 was analyzed on recto-vaginal colonizing isolates from mothers whose infants remained healthy, and on isolates from infants who developed invasive GBS disease. Flow cytometry was used to determine surface expression levels. The anti-gbs2106 IgG in maternal and infant or cord blood was measured using a bead-based assay on the Luminex platform.

RESULTS

The gbs2106 gene was present on all colonizing GBS-isolates from women in the control group and infant invasive GBS-isolates. The gbs2106 protein was expressed on 81.6 % (71/87) and 82.2 % (48/58) of maternal colonizing isolates and invasive GBS-isolates, respectively. There was a strong positive correlation (r = 0.855, p < 0.0001) of maternal and cord serum anti-gbs2106 IgG levels, with the combined cord to maternal anti-gbs2106 IgG geometric mean concentration ratio being 0.9 (IQR 0.7-1.1). Serum anti-gbs2106 IgG geometric mean concentrations in the infants were lower among the invasive disease cases (158.7 arbitrary units [AU]/ml; 95 %CI: 102.3-246.2) compared with controls (304.8 AU/ml; 95 %CI: 226.8-409.8; p = 0.012).

CONCLUSION

Our study demonstrates an inverse association between infant serum anti-gbs2106 IgG and risk of invasive GBS disease, indicating gbs2106 protein as a potential vaccine candidate.

Group B streptococcal infections in pregnancy and early life

SUMMARYBacterial infections with Group B Streptococcus (GBS) are an important cause of adverse outcomes in pregnant individuals, neonates, and infants. GBS is a common commensal in the genitourinary and gastrointestinal tracts and can be detected in the vagina of approximately 20% of women globally. GBS can infect the fetus either during pregnancy or vaginal delivery resulting in preterm birth, stillbirth, or early-onset neonatal disease (EOD) in the first week of life. The mother can also become infected with GBS leading to postpartum endometritis, and rarely, maternal sepsis. An invasive GBS infection of the neonate may present after the first week of life (late-onset disease, LOD) through transmission from caregivers, breast milk, and other sources. Invasive GBS infections in neonates can result in sepsis, pneumonia, meningitis, neurodevelopmental impairment, death, and lifelong disability. A policy of routine screening for GBS rectovaginal colonization in well-resourced countries can trigger the administration of intrapartum antibiotic prophylaxis (IAP) when prenatal testing is positive, which drastically reduces rates of EOD. However, many countries do not routinely screen pregnant women for GBS colonization but may administer IAP in cases with a high risk of EOD. IAP does not reduce rates of LOD. A global vaccination campaign is needed to reduce the significant burden of invasive GBS disease that remains among infants and pregnant individuals. In this narrative review, we provide a comprehensive overview of the global impact of GBS colonization and infection, virulence factors and pathogenesis, and current and future prophylactics and therapeutics.

Diversity in Naturally Acquired Immunity to Group B Streptococcus: A Comparative Study of Women From Bangladesh, Malawi, and the United Kingdom

BACKGROUND

Significant disparities in group B Streptococcus (GBS) colonization and neonatal disease rates have been documented across different geographic regions. For example, Bangladesh reports notably lower rates as compared with the United Kingdom and Malawi. This study investigates whether this epidemiologic variability correlates with the immune response to GBS in these regions.

METHODS

Qualitative and quantitative analyses of naturally acquired immunoglobulin G (IgG) antibodies against GBS capsular polysaccharide and the Alp protein family were conducted in serum samples from women of childbearing age in the United Kingdom, Bangladesh, and Malawi. The efficacy of these antibodies in clearing vaginal colonization or protecting newborns from GBS infection was assessed with humanized mouse models.

RESULTS

Bangladeshi women displayed the highest diversity in serotype distribution, with elevated IgG levels in the serum against GBS capsular polysaccharides Ia, Ib, II, III, IV, and V, as well as Alp family proteins. In contrast, Malawian sera demonstrated the weakest antibody response. Bangladeshi sera also showed heightened IgG-mediated complement deposition, opsonophagocytic killing, and neonatal Fc receptor binding while tested against capsular polysaccharide Ib. In a humanized neonatal Fc receptor mouse model, Bangladeshi sera led to faster clearance of GBS virulent serotype Ib vaginal colonization. Additionally, offspring from dams passively immunized with Bangladeshi sera demonstrated notably increased survival rates.

CONCLUSIONS

This study demonstrates significant variability in the immune response to GBS across different geographic regions. These findings underscore the importance of understanding GBS-induced immune response in diverse populations, which may significantly affect vaccine efficacy in these regions.

Vaccines in Dermatology-Present and Future: A Review

Dermatological vaccines have emerged as critical tools in preventing and managing a wide spectrum of skin conditions ranging from infectious diseases to malignancies. By synthesizing evidence from existing literature, this review aims to comprehensively evaluate the efficacy, safety, and immunogenicity of vaccines used in dermatology, including both approved vaccines and those currently being researched. Vaccines discussed in this paper include those targeting dermatoses and malignancies (e.g., acne vulgaris, atopic dermatitis, and melanoma); infectious diseases (e.g., human papillomavirus (HPV); varicella zoster virus (VZV); herpes zoster (HZ); warts; smallpox; mpox (monkeypox); hand, foot, and mouth disease (HFMD); candidiasis and Group B Streptococcus (GBS); and neglected tropical diseases (e.g., Buruli ulcer, leprosy, and leishmaniasis). Through this review, we aim to provide a detailed understanding of the role of vaccines in dermatology, identify knowledge gaps, and propose areas for future research.

Bioinformatics analysis to design a multi-epitope mRNA vaccine against S. agalactiae exploiting pathogenic proteins

Antibiotic resistance in bacterial pathogen infections is a growing global issue that occurs due to their adaptation to changing environmental conditions. Therefore, producing an efficient vaccine as an alternative approach can improve the immune system, eradicate related pathogens, and overcome this growing problem. Streptococcus agalactiae belongs to group B Streptococcus (GBS). Colonization of GBS during pregnancy is a significant risk factor for infants and young children. S. agalactiae infected population exhibits resistance to beta-lactams, including penicillin and the second-line antibiotics erythromycin and clindamycin. On the other hand, there are currently no commercial vaccines against this pathogen. Vaccination of pregnant women is a highly effective method to protect newborns and infants from S. agalactiae infection, and it has been identified as an urgent demand by the World Health Organization. This study employed various immunoinformatic tools to develop an effective vaccine that could trigger both humoral and cell-mediated immunity and prevent disease. For this purpose, three conserved antigenic proteins of the main pathogenic strains of S. agalactiae were utilized to predict CTL, HTL, and B-cell epitopes for producing an mRNA vaccine against different strains of S. agalactiae. The selected epitopes were fused using proper linkers. The Resuscitation promoting factor E (RpfE) sequence was incorporated in the designed vaccine construct as an adjuvant to boost its immune response. Different physicochemical characteristics of the final designed vaccine, modeling of the three-dimensional structure, molecular docking, molecular dynamics simulation, and immunological response simulation were screened following vaccine administration in an in vivo model. Computational immune simulation data identified that IgG1, IgM, INF γ, IL-2, T helper, and B-cell populations increased significantly after vaccination. These findings suggested that the vaccine candidate may provide good protection against S. agalactiae infection. However, experimental and animal model studies are required for additional validation and implementation in human vaccination programs.

Genomic characterization and resistance features of Streptococcus agalactiae isolated from non-pregnant adults in Shandong, China

BACKGROUND

Streptococcus agalactiae is a recognized pathogen that primarily affects infants and pregnant women. However, its increasingly important role in causing invasive infections among non-pregnant adults has become a significant health concern due to the severity and variety of its clinical impacts.

METHODS

Nonduplicate S. agalactiae clinical strains associated with clinical infections (n = 139) were isolated from non-pregnant adults in Shandong, China. Antibiotic susceptibility testing, whole-genome sequencing and genomic analyses were conducted to characterize the genome and identify resistance features of these strains.

RESULTS

The strains exhibited universal susceptibility to penicillin, ampicillin, cefotaxime, meropenem, linezolid and vancomycin. Notably, high resistance rates were observed for erythromycin (91.4%), clindamycin (89.2%), levofloxacin (84.2%), tetracycline (54.0%) and, to a lesser extent, chloramphenicol (12.9%). Serotyping revealed seven serotypes and one non-typeable strain. Serotypes Ia, Ib, III and V predominated, representing 95.7% of the strains. Nineteen sequence types were categorized into seven clonal complexes, with CC10 being the most prevalent at 48.9%. The resistance genes mreA (100%), ermB (70.5%) and tetM (46.0%) were commonly detected. All the isolates carried at least one pilus backbone determinant and one alpha-like protein gene, with the PI-1+PI-2a and the bca gene being the most frequent at 84.2% and 54.7%, respectively.

CONCLUSIONS

While S. agalactiae strains in non-pregnant adults retain sensitivity to β-lactam antibiotics, the elevated resistance to erythromycin, clindamycin, levofloxacin and tetracycline is concerning. Given the growing elderly population worldwide, the burden of S. agalactiae infections is significant. Continuous surveillance of serotype distribution and antibiotic resistance patterns is imperative for targeted prevention and therapeutic strategies.

Enrichment culture evaluation and characterization of Streptococcus agalactiae among pregnant women in Japan

Introduction. Maternal screening tests and prophylactic antibiotics are important to prevent neonatal and infant group B streptococcal (GBS) infections.Hypothesis/Gap Statement. The performance of enrichment broth media for GBS screening that are available in Japan is unclear. Whole-genome data of GBS isolates from pregnant women in Japan is lacking.Aim. The aim of this study was to compare the protocol performance of six enrichment broths and two subculture agar plates, which were all available in Japan, for GBS detection. In addition, we showed whole-genome data of GBS isolates from pregnant women in Japan.Methodology. We collected 133 vaginal-rectal swabs from pregnant women visiting clinics and hospitals in Nagasaki Prefecture, Japan, and compared the protocol performance of 6 enrichment broths and 2 subculture agar plates. All GBS isolates collected in this study were subjected to whole-genome sequencing analysis.Results. We obtained 133 vaginal-rectal swabs from pregnant women at 35-37 weeks of gestation from 8 private clinics and 2 local municipal hospitals within Nagasaki Prefecture, Japan. The detection rate of the protocol involving the six enrichment broths and subsequent subcultures varied between 95.5 and 100 %, depending on the specific choice of enrichment broth. The GBS carriage rate among pregnant women in this region was 18.8 %. All 25 isolates derived from the swabs were susceptible to penicillin, whereas 48 and 36 % of the isolates demonstrated resistance to erythromycin and clindamycin, respectively. The distribution of serotypes was highly diverse, encompassing seven distinct serotypes among the isolates, with the predominant serotype being serotype V (n = 8). Serotype V isolates displayed a tendency towards increased resistance to erythromycin and clindamycin, with all resistant isolates containing the ermB gene.Conclusion. There was no difference in performance among the culture protocols evaluated in this study. GBS strains isolated from pregnant women appeared to have greater genomic diversity than GBS strains detected in neonates/infants with invasive GBS infections. To confirm this result, further studies with larger sample sizes are needed.

Current research update on group B streptococcal infection related to obstetrics and gynecology

Group B streptococcal (GBS) is a Gram-positive bacterium that is commonly found in the gastrointestinal tract and urogenital tract. GBS infestation during pregnancy is a significant contributor to maternal and neonatal morbidity and mortality globally. This article aims to discuss the infectious diseases caused by GBS in the field of obstetrics and gynecology, as well as the challenges associated with the detection, treatment, and prevention of GBS.

Distributions of candidate vaccine Targets, virulence Factors, and resistance features of invasive group B Streptococcus using Whole-Genome Sequencing: A Multicenter, population-based surveillance study

BACKGROUND

Group B Streptococcus (GBS) is a leading cause of morbidity and mortality in young infants worldwide. This study aimed to investigate candidate GBS vaccine targets, virulence factors, and antimicrobial resistance determinants.

METHODS

We used whole-genome sequencing to characterize invasive GBS isolates from infants < 3 months of age obtained from a multicenter population-based study conducted from 2015 to 2021 in China.

RESULTS

Overall, seven serotypes were detected from 278 GBS isolates, four (Ia, Ib, III, V) of which accounted for 97.8 %. We detected 30 sequence types (including 10 novel types) that were grouped into six clonal complexes (CCs: CC1, CC10, CC17, CC19, CC23 and CC651); three novel ST groups in CC17 were detected, and the rate of CC17, considered a hyperinvasive neonatal clone complex, was attached to 40.6 % (113/278). A total of 98.9 % (275/278) of isolates harbored at least one alpha-like protein gene. All GBS isolates contained at least one of three pilus backbone determinants and the pilus types PI-2b and PI-1 + PI-2a accounted for 79.8 % of the isolates. The 112 serotype III/CC17 GBS isolates were all positive for hvgA. Most of the isolates (75.2 %) were positive for serine-rich repeat glycoprotein determinants (srr1or srr2). Almost all isolates possessed cfb (99.6 %), c1IE (100 %), lmb (95.3 %) or pavA (100 %) gene. Seventy-seven percent of isolates harboured more than three antimicrobial resistance genes with 28.4 % (79/278) gyrA quinoloneresistancedeterminants mutation, 83.8 % (233/278) carrying tet cluster genes and 77.3 % (215/278) carrying erm genes which mediated fluoroquinolone, tetracycline and clindamycin resistance, respectively."

CONCLUSIONS

The findings from this large whole-genome sequence of GBS isolates establish important baseline data required for further surveillance and evaluating the impact of future vaccine candidates.

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.

The immunogenicity and safety of Group B Streptococcal maternal vaccines: A systematic review

PURPOSE

To systematically review immunogenicity and safety data of maternal group B streptococcal (GBS) vaccines in published clinical trials until July 2023.

METHODS

EMBASE, MEDLINE, Cochrane Library and clinicaltrial.gov. databases were searched for clinical studies that reported immunogenicity and/or safety of GBS vaccine in non-pregnant adults, pregnant women and infants between 1st of January 1996 to 31st of July 2023. Pairs of reviewers independently selected, data extracted, and assessed the risk of bias of the studies. Discrepancies were resolved by consensus. (PROSPERO CRD42020185213).

RESULTS

We retrieved 1472 records from the literature search; 20 studies and 6 sub-studies were included, involving 4440 non-pregnant participants and 1325 pregnant women with their newborns. There was a significantly higher IgG Geometric Mean Concentration (GMC) and IgG placental transfer ratios in vaccinated compared to placebo groups, with peak response 4-8 weeks after vaccination. Placental transfer ratio varied from 0.4 to 1.4 across five studies. The different clinical trials used different assays that limited direct comparison. There were no significant differences in the risk of serious adverse events (adjusted OR 0.73; 95 % CI 0.49-1.07), serious adverse events leading to withdrawal (adjusted OR 0.44; 95 % CI 0.13-1.51), and systemic illness or fever (adjusted OR 1.05; 95 % CI 0.26-4.19) between the vaccine and placebo groups.

CONCLUSIONS

The published clinical trials show significant IgG GMC response in subjects receiving the conjugated capsular polysaccharide and surface subunit protein vaccines compared to placebo. In current clinical trials of experimental GBS maternal vaccines, there have been no observed serious adverse events of special interest directly linked to vaccination.

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.

[Recent research on the epidemiology and preventive strategies of neonatal group B Streptococcus infection in the latest decade]

Currently, the main strategy for preventing neonatal group B Streptococcus (GBS) infection is prenatal screening combined with intrapartum antibiotic prophylaxis, which has effectively reduced the incidence of neonatal GBS early-onset disease. However, the burden of GBS infection is still significant. The intrapartum antibiotic prophylaxis strategy has limitations such as inducing antibiotic resistance and inability to effectively prevent GBS late-onset disease. It is crucial to develop and evaluate other prevention strategies, while paying close attention to assessing penicillin allergy in pregnant women and how to prevent GBS infection in neonates with negative maternal GBS screening. In recent years, there has been some progress in GBS vaccines and related immunological research, and the use of specific vaccines is expected to significantly reduce GBS infection in neonates.

Safety and immunogenicity of the group B streptococcus vaccine AlpN in a placebo-controlled double-blind phase 1 trial

Group B streptococcus (GBS) is a leading cause of life-threatening neonatal infections and subsets of adverse pregnancy outcomes. Essentially all GBS strains possess one allele of the alpha-like protein (Alp) family. A maternal GBS vaccine, consisting of the fused N-terminal domains of the Alps αC and Rib (GBS-NN), was recently demonstrated to be safe and immunogenic in healthy adult women. To enhance antibody responses to all clinically relevant Alps, a second-generation vaccine has been developed (AlpN), also containing the N-terminal domain of Alp1 and the one shared by Alp2 and Alp3. In this study, the safety and immunogenicity of AlpN is assessed in a randomized, double-blind, placebo-controlled, and parallel-group phase I study, involving 60 healthy non-pregnant women. AlpN is well tolerated and elicits similarly robust and persistent antibody responses against all four Alp-N-terminal domains, resulting in enhanced opsonophagocytic killing of all Alp serotypes covered by the vaccine.

Association of infant Rib and Alp1 surface protein N-terminal domain immunoglobulin G and invasive Group B Streptococcal disease in young infants

BACKGROUND

Vaccine development for Group B Streptococcus (GBS), a common cause of invasive disease in early-infancy and adverse pregnancy outcomes, include exploring widely-expressed GBS surface proteins as vaccine epitopes. We investigated the association between natural infant serum IgG against the RibN and Alp1N domains and risk of invasive GBS disease caused by isolates expressing these proteins.

METHODS

We analyzed maternal and infant serum samples from GBS disease cases and infants born to GBS-colonized women controls. Bayesian modelling was used to calculate the GBS homotypic IgG concentration associated with risk reduction of invasive disease in the infant.

RESULTS

PCR-based typing of 85 GBS invasive isolates showed 46 and 24 possessing the gene for Rib and Alp1, respectively. These were matched to 46 and 36 infant controls whose mothers were colonized with GBS expressing Rib and Alp1, respectively. RibN IgG geometric mean concentrations (GMC) were lower in cases than controls among infants (0.01; 95 %CI: 0.01-0.02 vs 0.04; 95 %CI: 0.03-0.06; p < 0.001), no significant difference was found between maternal RibN IgG GMC in cases compared to controls. Alp1N IgG GMC was also lower in infant cases (0.02; 95 %CI: 0.01-0.03) than controls (0.05; 95 %CI: 0.04-0.07; p < 0.001); albeit not so in mothers. An infant IgG threshold ≥ 0.428 and ≥ 0.112 µg/mL was associated with 90 % risk reduction of invasive GBS disease due to Rib and Alp1 expressing strains, respectively.

DISCUSSION

Lower serum RibN and Alp1N IgG GMC were evident in infants with invasive GBS disease compared with controls born to women colonized with GBS expressing the homotypic protein. These data support the evaluation of Alp family proteins as potential vaccine candidates against invasive GBS disease.

Group B streptococcus virulence factors associated with different clinical syndromes: Asymptomatic carriage in pregnant women and early-onset disease in the newborn

Background

Group B streptococcus (GBS) harbors many virulence factors but there is limited data regarding their importance in colonization in pregnancy and early-onset disease (EOD) in the newborn. We hypothesized that colonization and EOD are associated with different distribution and expression of virulence factors.

Methods

We studied 36 GBS EOD and 234 GBS isolates collected during routine screening. Virulence genes (pilus-like structures-PI-1, PI-2a, PI-2b; rib and hvgA) presence and expression were identified by PCR and qRT-PCR. Whole genome sequencing (WGS) and comparative genomic analyses were used to compare coding sequences (CDSs) of colonizing and EOD isolates.

Results

Serotype III (ST17) was significantly associated with EOD and serotype VI (ST1) with colonization. hvgA and rib genes were more prevalent among EOD isolates (58.3 and 77.8%, respectively; p < 0.01). The pilus loci PI-2b and PI-2a were more prevalent among EOD isolates (61.1%, p < 0.01), while the pilus loci PI-2a and PI-1 among colonizing isolates (89.7 and 93.1% vs. 55.6 and 69.4%, p < 0.01). qRT PCR analysis revealed that hvgA was barely expressed in colonizing isolates, even though the gene was detected. Expression of the rib gene and PI-2b was two-fold higher in EOD isolates compared to colonizing isolates. Transcription of PI-2a was three-fold higher in colonizing isolates compared to EOD isolates. ST17 isolates (associated with EOD) had a smaller genome size compared ST1 and the genome was more conserved relative to the reference strain and ST17 isolates. In a multivariate logistic regression analysis virulence factors independently associated with EOD were serotype 3, and PI-1 and PI-2a was protective.

Conclusion

There was a significant difference in the distribution of hvg A, rib, and PI genes among EOD (serotype III/ST17) and colonizing (serotype VI/ST1) isolates suggesting an association between invasive disease and these virulence factors. Further study is needed to understand the contribution of these genes to GBS virulence.

Group B Streptococcus: Virulence Factors and Pathogenic Mechanism

Group B Streptococcus (GBS) or Streptococcus agalactiae is a major cause of neonatal mortality. When colonizing the lower genital tract of pregnant women, GBS may cause premature birth and stillbirth. If transmitted to the newborn, it may result in life-threatening illnesses, including sepsis, meningitis, and pneumonia. Moreover, through continuous evolution, GBS can use its original structure and unique factors to greatly improve its survival rate in the human body. This review discusses the key virulence factors that facilitate GBS invasion and colonization and their action mechanisms. A comprehensive understanding of the role of virulence factors in GBS infection is crucial to develop better treatment options and screen potential candidate molecules for the development of the vaccine.

Sublingual immunisation with GBS serotype III capsular polysaccharide-tetanus toxoid conjugate vaccine induces systemic and mucosal antibody responses which are opsonophagocytic and inhibit GBS colonisation of vaginal epithelial cells

No vaccines are currently licensed against Group B streptococcus (GBS), an important cause of morbidity and mortality in babies and adults. Using a mouse model, and in vitro opsonophagocytosis and colonisation assays, we evaluated the potential of a sublingually-administered polysaccharide-conjugate vaccine against GBS serotype III. Sublingual immunisation of mice with 10 µg of GBS conjugate vaccine once a week for 5 weeks induced a substantial systemic IgG anti-polysaccharide response which was similar to the level induced by subcutaneous immunsation. In addition, sublingual immunisation also induced mucosal (IgA) antibody responses in the mouth, intestines and vagina. Immune sera and intestinal washes were functionally active at mediating killing of the homologous GBS serotype III in an opsonophagocytosis assay. In addition, intestinal and vaginal washes inhibited the colonisation of mouse vaginal epithelial cells by the vaccine homologous strain. These results suggest that, in addition to the induction of high levels of IgG antibodies that could be transduced from the immunised mother to the foetus to protect the newborn against GBS infection, sublingual immunisation can elicit a substantial mucosal antibody response which might play an important role in the prevention of GBS colonisation in immunised women, thereby eliminating the risk of GBS transmission from the mother to the baby during pregnancy or at birth.

Molecular Epidemiology of Group B Streptococci in Lithuania Identifies Multi-Drug Resistant Clones and Sporadic ST1 Serotypes Ia and Ib

Streptococcus agalactiae (Group B Streptococcus, GBS) is a leading cause of neonatal infections. Yet, detailed assessment of the genotypic and phenotypic factors associated with GBS carriage, mother-to-baby transmission, and GBS infection in neonates and adults is lacking. Understanding the distribution of GBS genotypes, including the predominance of different serotypes, antimicrobial resistance (AMR) genes, and virulence factors, is likely to help to prevent GBS diseases, as well as inform estimates of the efficacy of future GBS vaccines. To this end, we set out to characterise GBS isolates collected from pregnant and non-pregnant women in Kaunas region in Lithuania. Whole genome sequences of 42 GBS isolates were analysed to determine multi-locus sequence typing (MLST), the presence of acquired AMR and surface protein genes, and the phylogenetic relatedness of isolates. We identified serotypes Ia (42.9%, 18/42), III (33.3%, 14/42), V (21.4%, 9/42), and a single isolate of serotype Ib. Genomic analyses revealed high diversity among the isolates, with 18 sequence types (STs) identified, including three novel STs. 85.7% (36/42) of isolates carried at least one AMR gene: tetM or tetO (35/42), ermB or lsaC (8/42) and ant6-Ia and aph3-III (2/42). This study represents the first genomic analysis of GBS isolated from women in Lithuania and contributes to an improved understanding of the global spread of GBS genotypes and phenotypes, laying the foundations for future GBS surveillance in Lithuania.

A Recombinant Alpha-Like Protein Subunit Vaccine (GBS-NN) Provides Protection in Murine Models of Group B Streptococcus Infection

BACKGROUND

Group B Streptococcus (GBS) transmission during pregnancy causes preterm labor, stillbirths, fetal injury, or neonatal infections. Rates of adult infections are also rising. The GBS-NN vaccine, engineered by fusing N-terminal domains of GBS Alpha C and Rib proteins, is safe in healthy, nonpregnant women, but further assessment is needed for use during pregnancy. Here, we tested GBS-NN vaccine efficacy using mouse models that recapitulate human GBS infection outcomes.

METHODS

Following administration of GBS-NN vaccine or adjuvant, antibody profiles were compared by ELISA. Vaccine efficacy was examined by comparing infection outcomes in GBS-NN vaccinated versus adjuvant controls during systemic and pregnancy-associated infections, and during intranasal infection of neonatal mice following maternal vaccination.

RESULTS

Vaccinated mice had higher GBS-NN-specific IgG titers versus controls. These antibodies bound alpha C and Rib on GBS clinical isolates. Fewer GBS were recovered from systemically challenged vaccinated mice versus controls. Although vaccination did not eliminate GBS during ascending infection in pregnancy, vaccinated dams experienced fewer in utero fetal deaths. Additionally, maternal vaccination prolonged neonatal survival following intranasal GBS challenge.

CONCLUSIONS

These findings demonstrate GBS-NN vaccine efficacy in murine systemic and perinatal GBS infections and suggest that maternal vaccination facilitates the transfer of protective antibodies to neonates.

Rectovaginal Colonization with Serotypes of Group B Streptococci with Reduced Penicillin Susceptibility among Pregnant Women in León, Nicaragua

Group B Streptococci (GBS) are important causes of neonatal sepsis and meningitis globally. To elucidate the potential benefits of maternal GBS vaccines, data is needed on the epidemiology of maternal GBS rectovaginal colonization, distribution of serotypes, and resistance to intrapartum antibiotic prophylaxis (IAP). We collected rectal and vaginal samples from 305 pregnant women in León, Nicaragua between 35 and 40 weeks gestation. Samples were cultured for GBS and confirmed using latex agglutination. GBS isolates underwent serotyping by quantitative polymerase chain reaction, and antimicrobial susceptibility testing by disk diffusion and microdilution following Clinical Laboratory Standard Institute guidelines. Sixty-three women (20.7%) were colonized with GBS in either the rectum or the vagina. Of 91 GBS isolates collected from positive cultures, most were serotypes II (28.6%), Ia (27.5%), and III (20.9%). Most GBS isolates (52.9%) were resistant to penicillin, the first-line prophylactic antibiotic. Penicillin resistance was highly correlated with resistance to vancomycin, ceftriaxone, and meropenem. The results of our study suggest that one-fifth of pregnant women in the urban area of León, Nicaragua are colonized with GBS and risk transmitting GBS to their offspring during labor. High resistance to commonly available antibiotics in the region suggests that prophylactic maternal GBS vaccination would be an effective alternative to IAP.

Toward the development of a protein-based group B Streptococcus vaccine

Clinical trials of protein-based vaccines to prevent Group B streptococcal infections are underway. In this issue of Cell Reports Medicine, Pawlowski et al.1 provide an extensive characterization of the immune response generated by the recently tested GBS-NN vaccine.

A group B Streptococcus alpha-like protein subunit vaccine induces functionally active antibodies in humans targeting homotypic and heterotypic strains

Maternal vaccination is a promising strategy for preventing neonatal disease caused by group B Streptococcus. The safety and immunogenicity of the prototype vaccine GBS-NN, a fusion protein consisting of the N-terminal domains of the alpha-like proteins (Alp) αC and Rib, were recently evaluated favorably in healthy adult women in a phase 1 trial. Here we demonstrate robust immunoglobulin G (IgG) and immunoglobulin A (IgA) responses against αC and Rib, as well as against the heterotypic Alp family members Alp1–Alp3. IgA and heterotypic IgG responses are more variable between subjects and correlate with pre-existing immunity. Vaccine-induced IgG mediates opsonophagocytic killing and prevents bacterial invasion of epithelial cells. Like the vaccine-induced response, naturally acquired IgG against the vaccine domains is dominated by IgG1. Consistent with the high IgG1 cross-placental transfer rate, naturally acquired IgG against both domains reaches higher concentrations in neonatal than maternal blood, as assessed in a separate group of non-vaccinated pregnant women and their babies.

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GBS-NN subunit vaccine broadly elicits IgG1 to homotypic αC and Rib N-terminal domains

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IgA and heterotypic IgG responses occur in vaccinees with pre-existing immunity

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Abs mediate opsonophagocytic killing and prevent bacterial epithelial cell invasion

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IgG against αC-N and Rib-N is transferred efficiently across the placenta

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.

Immunogenic Proteins of Group B Streptococcus-Potential Antigens in Immunodiagnostic Assay for GBS Detection

Streptococcus agalactiae (Group B Streptococcus, GBS) is an opportunistic pathogen, which asymptomatically colonizes the gastrointestinal and genitourinary tract of up to one third of healthy adults. Nevertheless, GBS carriage in pregnant women may lead to several health issues in newborns causing life threatening infection, such as sepsis, pneumonia or meningitis. Recommended GBS screening in pregnant women significantly reduced morbidity and mortality in infants. Nevertheless, intrapartum antibiotic prophylaxis, recommended following the detection of carriage or in case of lack of a carriage test result for pregnant women who demonstrate certain risk factors, led to the expansion of the adverse phenomenon of bacterial resistance to antibiotics. In our paper, we reviewed some immunogenic GBS proteins, i.e., Alp family proteins, β protein, Lmb, Sip, BibA, FsbA, ScpB, enolase, elongation factor Tu, IMPDH, and GroEL, which possess features characteristic of good candidates for immunodiagnostic assays for GBS carriage detection, such as immunoreactivity and specificity. We assume that they can be used as an alternative diagnostic method to the presently recommended bacteriological cultivation and MALDI.

Bacterial and Host Determinants of Group B Streptococcal Vaginal Colonization and Ascending Infection in Pregnancy

Group B streptococcus (GBS) is a gram-positive bacteria that asymptomatically colonizes the vaginal tract. However, during pregnancy maternal GBS colonization greatly predisposes the mother and baby to a wide range of adverse outcomes, including preterm birth (PTB), stillbirth, and neonatal infection. Although many mechanisms involved in GBS pathogenesis are partially elucidated, there is currently no approved GBS vaccine. The development of a safe and effective vaccine that can be administered during or prior to pregnancy remains a principal objective in the field, because current antibiotic-based therapeutic strategies do not eliminate all cases of invasive GBS infections. Herein, we review our understanding of GBS disease pathogenesis at the maternal-fetal interface with a focus on the bacterial virulence factors and host defenses that modulate the outcome of infection. We follow GBS along its path from an asymptomatic colonizer of the vagina to an invasive pathogen at the maternal-fetal interface, noting factors critical for vaginal colonization, ascending infection, and vertical transmission to the fetus. Finally, at each stage of infection we emphasize important host-pathogen interactions, which, if targeted therapeutically, may help to reduce the global burden of GBS.