Prevention of systemic infections caused by group B streptococcus and Staphylococcus aureus by multivalent polysaccharide-protein conjugate vaccines

Maternal GBS vaccination for preventing group B streptococcus disease in newborns: A mini review of current evidence

Group B streptococcus (GBS) poses a significant threat to neonates, leading to morbidity and mortality. Intrapartum antibiotics, although effective, have limitations, prompting the exploration of maternal vaccination. This study reviews the current evidence for maternal GBS vaccination in the prevention of early-onset GBS disease in newborns. A search on Google Scholar, PubMed, and Scopus identified studies assessing the impact of maternal GBS vaccination on early-onset GBS disease. Inclusion criteria comprised English-language clinical trials or observational studies. Data extraction included study details, immunogenicity profiles, effectiveness, safety outcomes, and relevant findings. Qualitative synthesis was employed for data analysis. Five studies meeting the inclusion criteria were reviewed. Maternal GBS vaccines demonstrated efficacy with sustained immunogenicity. Adverse events, although documented, were predominantly non-severe. Variability in immune responses and maternal-to-infant antibody ratios show the need for tailored vaccination approaches. Long-term follow up and surveillance are essential to assess persistence and identify unintended effects. Positive outcomes in vaccine efficacy support GBS vaccination integration into maternal health programs. Implementation challenges in diverse healthcare infrastructures require tailored approaches, especially in resource-limited settings. Overcoming cultural barriers and ensuring healthcare provider awareness are crucial for successful vaccination.

Meningococcal PorB induces a robust and diverse antigen specific T cell response as a vaccine adjuvant

Vaccines formulated with adjuvant have been effective against numerous infectious diseases, almost always due to induction of functional antibodies that recognizes the pathogen of interest. There is an unmet clinical need for vaccine adjuvants that induce T cells responses to potentially enhance protection against malignancies and intracellular pathogens, where a humoral response, alone, may not be adequate for protection. In this study, we demonstrate that a TLR2 ligand-based adjuvant, meningococcal PorB, has broad immunostimulatory activity with the ability to induce a robust and diverse vaccine antigen specific T cell response. We demonstrate that a vaccine formulated with PorB admixed with ovalbumin induces a wide variety of antigen specific antibody subclasses and effector molecules (MIG, MCP-1, IP-10, MIP-1α, KC & IL-2) with known roles for inducing T cell responses, along with elevated levels of Th1 and Th2 type cytokines upon antigen stimulation. We confirmed production of these cytokines by examining the antigen-specific T cells induced by PorB in vivo. After two immunizations with vaccine formulated with PorB/OVA, antigen-specific CD4 and CD8 T cells were significantly increased in numbers and produced IL-4 or IFN-γ upon ex vivo antigen re-stimulation. Finally, in a Listeria mouse infection model, vaccine formulated with PorB significantly reduced the bacterial burden upon a low dose infection and increased survival upon a high dose infection with recombinant Listeria monocytogenes engineered to express OVA (rLmOVA), a pathogen that requires OVA-antigen specific cytotoxic CD8 T cells for clearance. In summary, PorB is able to induce antigen specific broad B and T cell responses, illustrating its potential as a potent and new vaccine adjuvant.

Group B streptococcal immunisation of pregnant women for the prevention of early and late onset Group B streptococcal infection of the neonate as well as adult disease

INTRODUCTION

Early onset neonatal Group B streptococcal disease is preventable. Intrapartum antibiotic prophylaxis has resulted in a significant reduction in neonatal mortality and morbidity. National guidelines for the selection of women eligible for intrapartum antibiotic prophylaxis, whether screening-based or risk-based, differ according to the local burden of disease. Despite the introduction of intrapartum antibiotic prophylaxis, there remains a significant burden of disease, which can be resolved by better adherence to guidelines, rapid identification of maternal colonization or in the future, vaccination. Areas covered: The introduction of a vaccine to women in the third trimester is likely to further reduce the burden of disease and provide benefits beyond the prevention of early neonatal disease, including meningitis and disability following late onset disease. Development of specific polyvalent vaccines continues, but testing has challenges and may require surrogate markers or molecular-based techniques to manipulate antigenicity and immunogenicity. Expert commentary: Group B streptococcal vaccination using conjugated polyvalent vaccines against the major disease causing serotypes of Group B streptococcus, either alone, or in combination with a policy of intrapartum antibiotic prophylaxis, may decrease the burden of Group B streptococcus beyond that achieved by current use of intrapartum antibiotic prophylaxis alone.

Natural acquired humoral immunity against serotype-specific group B Streptococcus rectovaginal colonization acquisition in pregnant women

Group B Streptococcus (GBS) rectovaginal colonization in pregnant women is associated with invasive GBS disease in newborns, preterm delivery and stillbirths. We studied the association of GBS serotype-specific capsular polysaccharide (CPS) antibody on new acquisition and clearance of rectovaginal GBS colonization in pregnant women from 20 weeks until 37 to 40 weeks' gestation. Serum serotype-specific CPS IgG antibody concentration was measured by multiplex enzyme-linked immunosorbent assay and opsonophagocytic activity (OPA) titres. Rectovaginal swabs were evaluated for GBS colonization, using standard culture methods and serotyping by latex agglutination, at five to six weekly intervals. Higher serotype III CPS antibody concentration was associated with lower risk of rectovaginal acquisition of serotype III during pregnancy (p 0.009). Furthermore, serotype-specific OPA titres to Ia and III were higher in women who remained free of GBS colonization throughout the study compared to those who acquired the homotypic serotype (p <0.001 for both serotypes). Serum CPS IgG values of ≥1μg/mL for serotype V and ≥3μg/mL for serotypes Ia and III were significantly associated with protection against rectovaginal acquisition of the homotypic serotype. A GBS vaccine that induces sufficient capsular antibody in pregnant women, including high OPA titres, could protect against rectovaginal colonization during the latter half of pregnancy.

Risk factors for group B streptococcal genitourinary tract colonization in pregnant women

OBJECTIVE

To identify risk factors for group B streptococcus (GBS) colonization in pregnancy, hypothesizing that health care workers may have increased risk.

METHODS

Population-based, case-control study comparing 40,459 cases of GBS colonization, identified from Washington State birth certificate data linked to hospital discharge data for live births between 1997 and 2002, with 84,268 controls matched by year of delivery by multivariable logistic regression.

RESULTS

After adjustment for confounders, the following characteristics were independently associated with increased maternal GBS colonization: health care occupation (odds ratio [OR] 1.22, 95% confidence interval [CI] 1.07-1.38), black race (OR 1.54, 95% CI 1.36-1.74), overweight (OR 1.07, 95% CI 1.01-1.12), obesity (OR 1.20, 95% CI 1.13-1.28), severe obesity (OR 1.45, 95% CI 1.28-1.63), median income greater than lowest quintile (OR 1.29, 95% CI 1.20-1.39 for fifth versus first quintile), some high school education (OR 1.21, 95% CI 1.05-1.40), high school graduate (OR 1.35, 95% CI 1.16-1.56), and adequate prenatal care (OR 1.14, 95% CI 1.06-1.24). Hispanic women (OR 0.88, 95% CI 0.80-0.96) and smokers (OR for 1-10 cigarettes per day 0.90, 95% CI 0.83-0.97) had a decreased odds of colonization.

CONCLUSION

Health care workers, black women, and women with high body mass index may be at greater risk of GBS colonization in pregnancy. However, any increases in risk are modest and the association between a health care occupation and GBS colonization needs to be investigated further.

A history of neonatal group B streptococcus with its related morbidity and mortality rates in the United States

The history of neonatal sepsis related to early onset group B streptococcus (GBS) emerged in the early 1970s. The neonatal mortality rate was 55% for those neonates with invasive GBS disease. The first adopted guidelines by the medical community to prevent early onset GBS were developed in the 1990s. One year after implementation of the guidelines, the mortality rate dropped to approximately 5%. Despite the great accomplishments in reducing the mortality rate, GBS remains the number one cause of infant morbidity and mortality in the United States.

Staphylococcus aureus types 5 and 8 capsular polysaccharide-protein conjugate vaccines

BACKGROUND

Staphylococcus aureus, the first or second most common pathogen isolated from patients, is capsulated; there are at least 12 capsular types, and types 5 and 8 comprise approximately 85% of blood. Types 5 and 8, composed of a trisaccharide repeat unit including a mannose uronic acid and 2 fucoses, are non-immunogenic. As protein conjugates, they induce opsonophagocytic antibodies that confer type-specific active and passive protection in mice.

METHODS

A phase II study of patients with end-stage renal disease showed that these conjugates induced approximately one third of the immunoglobulin G antibody of healthy individuals. Increasing the dose to 100 microg of polysaccharide induced levels similar to that in healthy individuals injected with 25 microg.

RESULTS

In a double-blinded randomized and controlled study of patients undergoing renal dialysis, the conjugates induced statistically significant protection against bacteremia for as long as 10 months after immunization. The estimated protective level was 80 microg Ab/mL. At re-injection approximately 2 years later, 83 of 83 recipients responded with protective levels.

CONCLUSIONS

Conjugate vaccine-induced antibodies to the types 5 and 8 capsular polysaccharide antibodies of S aureus prevent bacteremia caused by this pathogen. The extent and duration of conjugate-induced immunity can be extended by re-immunization approximately 1 year later. Studies of patients undergoing cardiovascular surgery who would be immunized with the staphylococcus conjugates when they are immunologically intact are planned.

Effects of intrapartum antimicrobial prophylaxis for prevention of group-B-streptococcal disease on the incidence and ecology of early-onset neonatal sepsis

Sepsis occurring in the first week of life can be a devastating neonatal problem. Group B streptococci (GBS) and enterobacteriaceae are the main causes of early-onset sepsis in more developed countries. Intrapartum antimicrobial prophylaxis (IAP) has lowered the incidence of early-onset GBS sepsis by 50-80%. However, there are concerns that the use of IAP may select for infections caused by enterobacteriaceae, including some strains resistant to antimicrobials. We explored potential associations between IAP use and changes in the causes of early-onset sepsis. We concluded that there have been substantial declines in the incidence of early-onset infections due to GBS and, in some settings, other bacteria. Increases in the frequencies of non-GBS or antimicrobial-resistant early-onset sepsis have been limited to preterm, low-birthweight, or very-low-birthweight neonates. We propose systematic monitoring of early-onset sepsis, coupled with targeted research, to inform periodic reassessment of prevention strategies.

Use of a Staphylococcus aureus conjugate vaccine in patients receiving hemodialysis

BACKGROUND

In patients with decreased resistance to infection, Staphylococcus aureus is a major cause of bacteremia and its complications. The capsular polysaccharides are essential for the pathogenesis of and immunity to S. aureus infection and are targets for vaccines.

METHODS

In a double-blind trial involving patients with end-stage renal disease who were receiving hemodialysis, we evaluated the safety, immunogenicity, and efficacy of a vaccine with S. aureus type 5 and 8 capsular polysaccharides conjugated to nontoxic recombinant Pseudomonas aeruginosa exotoxin A. Between April 1998 and August 1999, 1804 adult patients at 73 hemodialysis centers were randomly assigned to receive a single intramuscular injection of either vaccine or saline. IgG antibodies to S. aureus type 5 and 8 capsular polysaccharides were measured for up to two years, and episodes of S. aureus bacteremia were recorded. Efficacy was estimated by comparing the incidence of S. aureus bacteremia in the patients who received the vaccine with the incidence in the control patients.

RESULTS

Reactions to the vaccine were generally mild to moderate, and most resolved within two days. The capsular polysaccharides elicited an antibody response of at least 80 microg per milliliter (the estimated minimal level conferring protection) in 80 percent of patients for type 5 and in 75 percent of patients for type 8. The efficacy during weeks 3 to 54 was only 26 percent (P=0.23). However, between weeks 3 and 40 after vaccination, S. aureus bacteremia developed in 11 of 892 patients in the vaccine group who could be evaluated for bacteremia, as compared with 26 of 906 patients in the control group (estimate of efficacy, 57 percent; 95 percent confidence interval, 10 to 81 percent; nominal P=0.02).

CONCLUSIONS

In patients receiving hemodialysis, a conjugate vaccine can confer partial immunity against S. aureus bacteremia for approximately 40 weeks, after which protection wanes as antibody levels decrease.

Neonatal group B streptococcal disease: how infection control teams can contribute to prevention efforts

Group B streptococcal (GBS) disease is a leading cause of morbidity and mortality among newborns. Many cases of newborn GBS disease can be prevented by the administration of intrapartum antibiotic prophylaxis. Current consensus guidelines for prevention of perinatal GBS disease have led to substantial declines in the incidence of GBS disease occurring in newborns <7 days of age (early-onset disease). Despite declines in the incidence of early-onset disease, approximately 20% of pregnant women are colonized with GBS at the time of labor and thus have the risk of transmitting the bacteria to their newborns. Consequently, continued and improved implementation of prevention efforts is essential. Infection control teams can contribute uniquely to prevention of perinatal GBS disease by serving as hospital champions of GBS disease prevention. In particular, teams can coordinate with administration and staff to encourage establishment and effective implementation of GBS prevention policies; facilitate improved laboratory processing of prenatal GBS screening specimens; monitor any adverse consequences of increased use of intrapartum antibiotics within the hospital; and investigate GBS cases that occur to determine whether they could have been prevented. By spearheading efforts to improve implementation of perinatal GBS disease prevention at the hospital level, hospital epidemiologists and infection control practitioners can play an important role in reducing the burden of early-onset GBS disease.

Group B streptococcal disease in the era of intrapartum antibiotic prophylaxis

BACKGROUND

Group B streptococcal infections are a leading cause of neonatal mortality, and they also affect pregnant women and the elderly. Many cases of the disease in newborns can be prevented by the administration of prophylactic intrapartum antibiotics. In the 1990s, prevention efforts increased. In 1996, consensus guidelines recommended use of either a risk-based or a screening-based approach to identify candidates for intrapartum antibiotics. To assess the effects of the preventive efforts, we analyzed trends in the incidence of group B streptococcal disease from 1993 to 1998.

METHODS

Active, population-based surveillance was conducted in selected counties of eight states. A case was defined by the isolation of group B streptococci from a normally sterile site. Census and live-birth data were used to calculate the race-specific incidence of disease; national projections were adjusted for race.

RESULTS

Disease in infants less than seven days old accounted for 20 percent of all 7867 group B streptococcal infections. The incidence of early-onset neonatal infections decreased by 65 percent, from 1.7 per 1000 live births in 1993 to 0.6 per 1000 in 1998. The excess incidence of early-onset disease in black infants, as compared with white infants, decreased by 75 percent. Projecting our findings to the entire United States, we estimate that 3900 early-onset infections and 200 neonatal deaths were prevented in 1998 by the use of intrapartum antibiotics. Among pregnant girls and women, the incidence of invasive group B streptococcal disease declined by 21 percent. The incidence among nonpregnant adults did not decline.

CONCLUSIONS

Over a six-year period, there has been a substantial decline in the incidence of group B streptococcal disease in newborns, including a major reduction in the excess incidence of these infections in black infants. These improvements coincide with the efforts to prevent perinatal disease by the wider use of prophylactic intrapartum antibiotics.

Synthesis of microcapsule by Staphylococcus aureus is not responsive to environmental phosphate concentrations

The polysaccharide microcapsule of Staphylococcus aureus has been reported to be differentially expressed depending on growth conditions, with phosphate concentration being the critical environmental component. This study evaluated the effect of growth of a serotype 8 strain of S. aureus in phosphate-replete and phosphate-limiting media on microcapsule production. The presence of the cell wall polymers microcapsule and teichoic acid was measured by both gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry. Production of microcapsule was unaffected by changes in the environmental phosphate concentration. There was, additionally, no evidence for a shift from teichoic acid to teichuronic acid synthesis.

Epidemiology of group B streptococcal disease in the United States: shifting paradigms

Since its emergence 25 years ago, group B streptococcus has become recognized as a cause of serious illness in newborns, pregnant women, and adults with chronic medical conditions. Heavy colonization of the genital tract with group B streptococcus also increases the risk that a woman will deliver a preterm low-birthweight infant. Early-onset infections (occurring at < 7 days of age) are associated with much lower fatality than when they were first described, and their incidence is finally decreasing as the use of preventive antibiotics during childbirth increases among women at risk. New serotypes of group B streptococcus have emerged as important pathogens in adults and newborns. Clinical and laboratory practices--in obstetrics, pediatrics, and clinical microbiology--have an impact on disease and/or its prevention, and protocols established at the institutional level appear to be critical tools for the reduction of perinatal disease due to group B streptococcus. Since intrapartum antibiotics will prevent at best only a portion of the full burden of group B streptococcal disease, critical developments in vaccine evaluation, including study of polysaccharide-protein conjugate vaccines, offer the potential for enhanced prevention in the relatively near future.

Properties of human anti-group B streptococcal type III capsular IgG antibody

The group B streptococcus is the commonest cause of bacterial infection in the newborn. In an attempt to prevent these infections, various vaccines are in development, most of which contain at least one of the capsular carbohydrates of the bacterium. We present new detailed data on the natural human antibody response to the type III capsular carbohydrate as we believe it is important to ascertain equivalent data for any new candidate vaccine in order to predict efficacy. We demonstrate that naturally occurring IgG is opsonically active in a complement-dependent manner, that fractions of differing avidity isolated from single donors have broadly similar opsonic activity, that the clonotypes from four individuals are restricted in number to a maximum of 15, and that binding kinetics ascertained using a resonant mirror biosensor show that specific antibodies have a moderately high affinity (mean Kd = 1.1e-8 M).

Staphylococcus aureus vaccination for dialysis patients--an update

Staphylococcus aureus infections are a major cause in both hemodialysis and peritoneal dialysis patients. The availability of a safe and effective protective vaccine would be of great benefit to these patients, but attempts at using vaccines consisting of inactivated whole cells have been unsuccessful. This article discusses an alternate approach to S. aureus vaccine design using a capsular polysaccharide conjugate and preliminary results in hemodialysis and peritoneal patients.