Anti-pneumococcal antibody titre measurement: what useful information does it yield?

Serotype 3 Antibody Response and Antibody Functionality Compared to Serotype 19A Following 13-Valent Pneumococcal Conjugate Immunization in Children

BACKGROUND

Prevention of infections in children vaccinated with 13-valent pneumococcal conjugate vaccine (PCV13) may be less effective against serotype 3 than 19A.

OBJECTIVE

The aim of this study was to to determine differences in IgG and functional antibody for serotype 3 versus 19A following PCV13 immunization, in IgG antibody levels induced by PCV13 compared to naturally-induced immunity, and assess effectiveness of PCV13 against serotype 3 and 19A in prevention of acute otitis media (AOM) and colonization among 6-36-month-old children.

METHODS

Samples were from a prospective, longitudinal, observational cohort study conducted in Rochester, NY. Pneumococcal detection was by culture. 713 serum were tested for antibody levels by enzyme-linked immunosorbent assay, 68 for functional antibody by opsonophagocytosis and 47 for antibody avidity by thiocyanate bond disruption. PCV13 effectiveness in preventing AOM and colonization was determined by comparison of pre-PCV13 detection of serotypes 3 and 19A to post-PCV13.

RESULTS

The proportion of children who reached the antibody threshold of ≧0.35 µg/mL after PCV13 was higher for serotype 19A than serotype 3. Only serotype 19A showed significant increase in PCV13-induced opsonophagocytosis assay titers and antibody avidity. Serotype 3 naturally-induced immune children showed a positive trend of increase in antibody level as children got older, but not PCV13-immunized children. PCV13 effectiveness was not identified in preventing AOM or colonization for serotype 3 but effectiveness of 19A was confirmed.

CONCLUSIONS

PCV13 elicits lower antibody levels and lower effectiveness to serotype 3 versus serotype 19A. Post-PCV13-induced antibody levels for serotype 3 are likely insufficient to prevent AOM and colonization in most young children.

No Waning of Pneumococcal Vaccine Responses over Time in People with Inflammatory Arthritis: Findings from a Single Centre Cohort

BACKGROUND

Vaccination against pneumococcus reduces the risk of infective events, hospitalisation, and death in individual with inflammatory arthritis, particularly in those on immunomodulating therapy who are at risk of worse outcomes from pneumococcal disease. The objective of this study was to investigate the serological protection following vaccination against pneumococcal serovars over time. Methods: This was a single centre, retrospective cohort study of individuals with rheumatoid arthritis, psoriatic arthritis, or axial spondylarthritis who had previously received the PPSV23 polysaccharide pneumococcal vaccine (Pneumovax). Data were retrieved between January 2021 to August 2023. Dates of previous pneumococcal vaccination were identified using linked primary care records. Serum serotype levels were collected. The primary outcome was serological response defined as a titre ≥0.35 mcg/mL in at least five from a total of 12 evaluated pneumococcal serovars, examined using a Luminex platform. Multivariate logistic regression models adjusting for age, gender, ethnicity, co-morbidities, and the use of prednisolone, conventional synthetic and biological DMARDs were used to determine the odds of a sustained serological response according to time categorised into ≤5 years, 5-10 years, and ≥10 years since vaccination. Results: Serological response was measured in 296 individuals with inflammatory arthritis, with rheumatoid arthritis the most common diagnosis (74% of patients). The median time between pneumococcal vaccine administration and serological assessment was 6 years (interquartile range 2.4 to 9.9). A positive serological response to at least 5 serovars was present in 195/296 (66%) of patients. Time since vaccination did not significantly associate with serological protection compared with those vaccinated <5 years, the adjusted ORs of vaccine response was 1.15 (95% CI 0.64 to 2.07) in those 5-10 years and 1.26 (95% CI: 0.64 to 2.48) in those vaccinated over 10 years ago. No individual variable from the multivariate model reached statistical significance as an independent predictor of vaccine response, although steroid use at the time of vaccine had a consistent detrimental impact on serological immunity. Conclusions: We demonstrated that antibody titres following vaccination against pneumococcal serovars do not appear to wane over time. It appears more critical to focus on maximising the initial vaccine response, which is known to be diminished in this patient population.

Naturally-induced serum antibody levels in children to pneumococcal polysaccharide 15B that correlate with protection from nasopharyngeal colonization but anti-serotype 15B antibody has low functional cross-reactivity with serotype 15C

BACKGROUND

Serotypes 15B and 15C have been added to new different pneumococcal-conjugate vaccines (PCV20 and V116, respectively). We determined a serum anti-15B antibody level that would be a correlate of protection (COP) against nasopharyngeal colonization and assessed functional cross-reactivity against serotype 15B and 15C in children following natural immunization.

METHOD

IgG-antibody to serotype 15B polysaccharide was measured by ELISA in 341 sera from 6 to 36 month old children collected before, at the time of, and after pneumococcal colonization caused by serotypes 15B and 15C. 155 age-matched controls who had no detected colonization caused by serotype 15B or 15C strains were used as controls. A two-step method was used for construction of COP models: a generalized estimating equation followed by logistic-regression. Opsonophagocytic (OPA) assays assessed functional cross-reactivity between serotypes 15B and 15C.

RESULTS

The derived COP for prevention of colonization was 1.18 µg/ml for serotype 15B and 0.63 µg/ml for serotype 15C, with a predictive probability of 80 %. Antibody levels did not correlate with OPA titers. 30 % of child samples, with moderate to high amounts of ELISA-measured antibody, showed no OPA titer against either serotype 15B or 15C. For remaining samples, very low or no functional cross-reactivity between serotypes 15B and 15C was measured.

CONCLUSIONS

A COP for prevention of colonization in young children based on naturally-induced antibody levels was derived for serotypes 15B and 15C that differed. Antibody levels correlated poorly with OPA titers and low functional cross-reactivity between serotypes 15B and 15C in child sera was observed.

Estimation of baseline IgG antibody levels to 23 pneumococcal vaccine-type capsular polysaccharides in healthy vaccine naïve Indian adults

Since immunological responses to pneumococcal vaccines are assessed by a fold-increase in antibody levels relative to pre-immunization levels, it is therefore critical to determine baseline antibody levels to establish putative threshold as a measure of normal response. Herein, for the first time, we measured baseline IgG antibody levels in 108 healthy unvaccinated Indian adults using WHO-recommended ELISA. Median baseline IgG concentration ranged between 0.54 µg/mL to 12.35 µg/mL. Highest levels of baseline capsule polysaccharide (cPS)-specific IgG were found against types 14, 19A, and 33F. Whereas, lowest baseline IgG levels were observed against types 3, 4, and 5. Overall, ∼79 % of study population had median baseline IgG levels ≥1.3 µg/mL against 74 % of cPS's. Substantial baseline antibody levels in unvaccinated adults were observed. The study would be critical in bridging gaps in baseline immunogenicity data and may offer a valuable foundation for evaluating immune response of Indian adults to pneumococcal vaccination.

Specific antibody deficiency to pneumococcal polysaccharide in a young adult with recurrent respiratory infections: a case report

Specific antibody deficiency against pneumococcal serotypes was detected in a patient with recurrent episodes of fever. A 21-year-old man presented with a two-month history of recurrent episodes of fever and shaking chills. He was diagnosed with recurrent episodes of pneumonia caused by Streptococcus pneumoniae serotype 19A and treated with amoxicillin. Serotype-specific antibodies were not produced against most of the serotypes, which were consistent with moderate specific antibody deficiency. After pneumococcal 13-valent conjugate vaccination and pneumococcal polysaccharide vaccination, he adequately responded to the infecting serotype with an antibody titer of 1.1 µg/mL. There were eventually no recurrent episodes of fever with pneumonia.

Pathogenesis of Streptococcus pneumoniae serotype 3 during natural colonization and infections among children and its IgG correlate of protection in a mouse model

Current licensed pneumococcal conjugate vaccines (PCVs) are effective against pneumococcal diseases caused by the serotypes contained in the PCvs However; several studies evaluating pneumococcal colonization and acute otitis-media (AOM) prevention in young children vaccinated with PCV13, observed less effectiveness against serotype-3. One possible reason for less effectiveness may be release of the capsular polysaccharide (CPS) of serotype-3 (CPS-3) as an immune evasion mechanism. Here we evaluated free CPS-3 levels released from 6 clinical isolates from young children compared to WU2 strain and to serotype-19A CPS (CPS-19A) released in vitro when interacting with nasopharyngeal, middle-ear and lung cell-lines. Clinical serotype-3 strains showed greater release of CPS than WU2 with the interaction to 2 cell-lines and all 6 clinical serotype-19A strains. We next evaluated CPS-3 vs CPS-19A levels in middle-ear fluid (MEF) and the nasopharynx (NP) of young children and found higher levels of CPS-3 compared to CPS-19A in MEF during AOM but not in NP secretions during colonization. With anti-CPS-3 IgG in MEF and NP secretions at time of health and onset of AOM, a significant negative correlation (r = -0.75, p < 0.05) between unbound anti-CPS-3 IgG levels and free- anti-CPS-3 in MEF were found, and a significant lower detection of unbound anti-CPS-3 IgG in NP at the time of health with serotype-3 SPN (p < 0.05) compared to irrelevant SPN serotypes were found. In a mouse model of AOM and pneumonia, we sought a correlate of protection against serotype-3 infection using human serum-derived anti-CPS-3 IgG. We conclude that serotype-3 clinical isolates from children release more capsule than WU2 strains or 19A strains during in vitro testing; release more capsule in the MEF of children during AOM than serotype 19A; unbound anti-CPS-3 IgG levels negatively correlate with free-anti-CPS-3; and a level of 2.8 µg/ml anti-CPS-3 antibody protects mice from AOM and pneumonia but not colonization.

Durability of Antibody Response after Primary Pneumococcal Double-Dose Prime-Boost Vaccination in Adult Kidney Transplant Recipients and Candidates: 18-Month Follow-Up in a Non-Blinded, Randomised Clinical Trial

Background: Pneumococcal prime-boost vaccination is recommended for solid organ transplant recipients and candidates. The long-term durability of the antibody (AB) response is unknown. The same applies to a dose-dependent immune response. Methods: We studied the durability of the vaccine response after 18 months in kidney transplant recipients (KTRs) and patients on the kidney transplant waiting list (WLPs). Both groups received either a normal dose (ND) or a double dose (DD) of the 13-valent pneumococcal conjugate vaccine and the 23-valent pneumococcal polysaccharide vaccine. The average pneumococcal AB geometric mean concentration (GMC) was evaluated. A level ≥ 1 mg/L was considered protective against invasive pneumococcal disease (IPD). Results: Sixty WLPs and 70 KTRs were included. The proportion of participants protected declined from 52% to 33% in WLPs and from 29% to 16% in KTRs, with the previously significant dose-effect in WLPs no longer present (40% DD vs. 27% ND; p = 0.273). Average pneumococcal AB GMCs remained significantly above baseline levels (all groups p ≤ 0.001). Drug-induced immunosuppression diminished the vaccine dose-effect. Conclusions: At follow-up, the pneumococcal prime-boost vaccination still provided significantly elevated average pneumococcal AB GMCs in both populations. Though the proportion of participants protected against IPD in WLP-DD and WLP-ND were statistically comparable, a DD may still be recommended for WLPs (EudraCT: 2016-004123-23).

Serum antibody levels to pneumococcal polysaccharides 22F, 33F, 19A and 6A that correlate with protection from colonization and acute otitis media in children

BACKGROUND

Serotypes 22F and 33F have been added to a new pneumococcal-conjugate vaccine (PCV-15) because of their prevalence in causing invasive pneumococcal diseases (IPD).

METHOD

We measured anti-polysaccharide 22F, 33F, 19A and 6A antibodies in children before and after pneumococcal colonization and acute otitis media (AOM) episodes caused by these specific-serotypes. A two-step method for construction of correlate of protection (COP) models included using a generalized estimating equation for the relationship between antibody level, age and colonization history followed by logistic-regression modelling that included colonization or AOM episodes as independent variables, and age adjusted antibody level as the predictor.

RESULTS

A vaccine-induced serum antibody level of 0.45 μg/ml for 22F, 0.51 μg/ml for 6A and 4.1 μg/ml for 19A correlated with prevention of pneumococcal colonization by respective serotypes (insufficient number of cases for 33F to find COP against colonization). Antibody levels of 0.25 μg/ml for 22F, 33F and 6A and 2 μg/ml for 19A correlated with prevention of AOM by the respective serotypes.

CONCLUSIONS

A COP threshold of anti-22F, 33F, 19A and 6A serum antibodies for NP colonization and AOM in young children can be derived using GEE and logistic regression modelling.

Utility of immunology, microbiology, and helminth investigations in clinical assessment of severe asthma

OBJECTIVE

Systematic assessment of patients with potential severe asthma is key to identification of treatable traits and optimal management. Assessment of antimicrobial immune function is part of that assessment at many centers although there is little evidence-base on its added value in clinical assessment of this patient group. As part of reviewing our local pathway, we have retrospectively reviewed these tests in 327 consecutive referrals to our severe asthma service, in an evaluation to describe the utility of these tests and allow refinement of the local guideline for patient assessment.

METHODS AND RESULTS

Serum immunoglobulin concentrations were in the normal range in most patients though 12 patients had serum IgG < 5.5 g/L and many had suboptimal anti-Haemophilus (127 of 249 patients tested) and anti-Pneumococcal (111 of 239) immune responses. As expected many patients had evidence of sensitization to Aspergillus although specific IgG was not confined to those with evidence of allergic sensitization/allergic bronchopulmonary aspergillosis (ABPA). Eighteen of 277 patients tested had serological evidence of Strongyloides infection. Bacteria and/or yeast were cultured from the sputum in 76 out of 110 patients productive of sputum, and the most common microbes cultured were Candida sp. (44 patients), Staphylococcus aureus (21 patients), Haemophilus influenzae (18 patients).

CONCLUSIONS

Many patients had evidence of infection, colonization, or sensitization to potential pathogens relevant to asthma. Strongyloides infection was evident in several patients, which may be a major issue when considering the risk of hyper-infection following immunosuppression and supports our local screening strategy.

Isolating polysaccharide IgG pneumococcal antibody responses by pre-adsorption of conjugate vaccine serotypes: A modified approach for the conjugate vaccine era

BACKGROUND

Assessment of pure polysaccharide response to the 23-valent pneumococcal polysaccharide vaccine (PPV23) can be biased by previous exposure to the conjugate vaccine (PCV). We applied pre-analytical modification to the existing ELISA by pre-incubating serum with PCV.

METHODS

PCV-adsorbed and non-adsorbed sera were prepared before measuring the concentration of anti-pneumococcal capsular polysaccharide (PCP) IgG antibodies by the whole pneumococcal ELISA. Paired pre and post-pneumococcal vaccination sera from 73 subjects were analyzed and the baseline anti-PCP IgG for each sample was subtracted from the post-vaccination value to measure vaccine responses. Absolute change in titers and fold changes were then compared between both methods.

RESULTS

In the PCV-vaccinated group (n = 28), pre-adsorption with PCV significantly reduced the vaccine responses compared to non-adsorbed sera [median increase in anti-PCP titers: 27.55 mg/l and 45.98 mg/l, respectively]. In addition, the median fold change dropped significantly from 3.026 to 2.313. In PPV23-vaccinated immunocompetent subjects (n = 28) there was a significant difference in anti-PCP responses with PCV adsorption [median values: 73.71 mg/l without and 51.04 mg/l with adsorption]. All the antibody deficiency patients (n = 17) displayed poor PPV23 responses. Although PPV23 responsiveness was not statistically different between both methods, we have observed a trend for lower anti-PCP IgG titers in PCV-adsorbed sera compared to non-adsorbed ones. Serotype-specific IgG analysis using a multiplexed bead-based immunoassay performed on 10 paired samples confirmed that the adsorption observed is specific to PCV serotypes.

CONCLUSION

Pre-analytical modification to the conventional ELISA by removing the PCV-specific serotypes may differentiate true polysaccharide response from recall response induced by previous PCV vaccination.

Pneumococcal antibody protection in patients with autoimmune inflammatory rheumatic diseases with varying vaccination status

Objectives: The aims of this cross-sectional study were to assess the pneumococcal antibody coverage in patients with autoimmune inflammatory rheumatic disease (AIRD) and to identify predictors associated with inadequate protective antibody levels. Method: Antibodies to 12 serotypes occurring in the commonly applied pneumococcal vaccines in Denmark were measured in AIRD patients with a diagnosis of rheumatoid arthritis, spondyloarthritis, or psoriatic arthritis attending the Department of Rheumatology at the North Denmark Regional Hospital. Immunization against pneumococcal infection was defined as a geometric mean level ≥ 1 μg antibodies/mL. Clinical information about vaccination status and disease/treatment history was retrieved from the medical file system. Results: Results of antibody measurement and vaccination status were available from 346 AIRD patients, of whom 200 (58%) were registered as receiving pneumococcal vaccination, whereas the remaining 146 patients (42%) were not. Of all 346 patients, only 61 (18%) were measured with an adequate level of protective antibodies (30% vs 1%, respectively). Methotrexate treatment at the time of vaccination and increasing age were identified as predictors of poor vaccination outcome in multiple logistic regression analysis. Conclusions: This post-vaccination study showed that less than one-fifth of the AIRD patients are adequately protected against pneumococcal infection, although the immunization programme had been implemented in more than half of the study population. Development of improved vaccination strategies is required to achieve a higher immunization coverage rate and more efficient lasting antibody response.

Focusing on Good Responders to Pneumococcal Polysaccharide Vaccination in General Hospital Patients Suspected for Immunodeficiency. A Decision Tree Based on the 23-Valent Pneumococcal IgG Assay

Background and Aim: Recently, the 23-valent IgG-assay was suggested as screening assay to identify poor responders to pneumococcal polysaccharide (PnPS)-vaccination with the serotype-specific assay as a second-line test. However, in a low pre-test probability general hospital setting predicting good responders could be more valuable to reduce the number of samples needing serotyping. Methods: Serotype-specific PnPS antibody-assays were performed for suspected immunodeficiency in two Dutch general hospitals (Jeroen Bosch Hospital, 's-Hertogenbosch; Elisabeth Tweesteden Hospital, Tilburg). 23-Valent PnPS antibody-assays were subsequently performed in archived material. Data were analyzed using receiver operating characteristic curves (AUC) and agreement indices (ICC). Results: Sera of 284 patients (348 samples) were included; 23-valent IgG-titres and the corresponding sum of PnPS-serotype specific antibodies showed moderate correlation (ICC = 0.63). In 232 conjugated-pneumococcal-vaccine-naïve patients (270 samples), a random 23-valent IgG-titer could discriminate between samples with and without ≥7/11, ≥7/13, or ≥6/9 pneumococcal serotypes when both cut-off values 0.35 and 1.0 μg/ml were used (AUC 0.86 and 0.92, respectively). All patients with a pre-immunization-titer ≥38.2 μg/ml and/or post-immunization-titer ≥96.1 μg/ml and none with a post-immunization-titer ≤38.5 μg/ml exhibited a good response to PnPS vaccination. Using these breakpoints as screening test to predict good responders, only 24% of patients would require further serotyping, as opposed to 68% if breakpoints to predict poor responders would have been used. Conclusion: In a low pre-test probability setting, the 23-valent IgG-assay proved to be a reliable screening test for good responders in conjugated-pneumococcal-vaccine-naïve patients, reducing the overall number of patient samples needing further serotyping, thus reducing overall costs of pneumococcal vaccination response assessment.

Immunogenicity of sequential 13-valent conjugated and 23-valent unconjugated pneumococcal vaccines in a population of children with lupus

Pneumococcal vaccination is recommended as a quality indicator for management of children with systemic lupus erythematosus. Literature on the immunogenicity of pneumococcal vaccines (PCVs) in children is scant. We sought to prospectively evaluate via an observational study, the immunogenicity to sequential children with lupus. Out of a cohort of 26 patients, approximately 65% achieved > 70% vaccinated serotype antibody levels of > 1.3 mcg/dL following PCV13, and of 22 patients followed through PPSV23 vaccination, 59% achieved the same. Patients with rituximab exposure in the 6 months prior to a vaccination were more likely to not achieve protective serotype levels ( p < 0.01 for PCV13, trend p = 0.07 for PPSV23). Three of 22 patients with no apparent risk factors did not achieve protective serotype levels. Non-responders to PCV13 generally did not respond to PPSV23. Retrospective healthy controls achieved 100% protective levels in response to PPSV23 vaccination, with 95% of serotypes being > 1.3 mcg/dL. Thus, sequential 13- and 23-valent pneumococcal vaccines achieve protective status for approximately two thirds of pediatric lupus patients in our population. Lack of response to vaccine may be secondary to induced or inherent functional impairments in the patient.

Measuring immune responses to pneumococcal vaccines

Quantitative assays that measure immune response to pneumococcal vaccines are not only important for the evaluation of vaccine immunogenicity and efficacy, but are also utilized in the clinical diagnosis of immune deficiency syndromes. Analytical methods have progressed in order to meet changing demands in both of these areas, from early methods to ELISA, and most recently multiplex bead array assays and opsonophagocytosis assays (OPA). It is necessary to understand the evolution of such techniques and the criteria for their interpretation in order to better inform the application of currently available methods, and to guide future investigation into assay development.

Invasive pneumococcal infections in pediatric liver-small bowel-pancreas transplant recipients

Children undergoing LSBPTx are at increased risk of IPI due to splenectomy. We aimed to describe the clinical features and outcomes of IPI in pediatric LSBPTx recipients. Between 2008 and 2016, 122 LSBPTx children at our center were retrospectively reviewed. Nine patients had 12 episodes of IPI; the median age at first infection was 3.5 years (range: 1.5-7.1 years). The median time from transplant to first infection was 3 years (range: 0.8-5.8 years). Clinical presentation included as follows: pneumonia (n = 1), bacteremia/sepsis (n = 7), pneumonia with sepsis (n = 1), meningitis with sepsis (n = 2), pneumonia and meningitis with sepsis (n = 1). The overall risk for IPI was 7.4% or 0.9% per year. The mortality rate was 22%. Seven (78%) children had received at least one dose of PCV13, four (44%) patients had received 23-valent pneumococcal polysaccharide vaccine prior to IPI. All patients were on oral penicillin prophylaxis. In conclusion, despite partial or complete pneumococcal immunization and reported antimicrobial prophylaxis, IPI in LSBPTx children can have a fatal outcome. Routine monitoring of pneumococcal serotype antibodies to determine the timing for revaccination might be warranted to ensure protective immunity in these transplant recipients.

The effect of splenectomy on the levels of PCV-13-induced memory B- and T cells

AIM

Splenectomised patients are associated with lifelong risk of fatal overwhelming post-splenectomy infection (OPSI), which is mostly caused by Streptococcus pneumoniae. Today OPSI cases can still be reported even in patients with appropriate vaccination. In our study, the levels of vaccine-specific memory B- and T cells were compared between control and splenectomised patients to enlighten the underlying reason.

MATERIALS AND METHODS

Five healthy and 14 post-traumatic splenectomised individuals were vaccinated with 13-valent pneumococcal conjugate vaccine (PCV-13) followed by 23-valent pneumococcal polysaccharide vaccine (PPV-23). The levels of memory B- and T cells were compared by ELISPOT analysis.

RESULTS

Splenectomised patients generated reduced levels of memory IgG B cells in response to PCV-13 vaccination, while the memory IFN-γ T-cell levels were undetectable in asplenic patients. This was despite the detection of vaccine-induced memory T-cell levels in control patients, which were analysed simultaneously following the same experimental protocol.

CONCLUSION

Our results suggest that spleen is important, but not essential, for survival and/or generation of memory IgG B cells. In contrast, it seems to be indispensable for PCV-13-specific memory T_H 1-cell levels. Studies enhancing the levels of vaccine-induced memory cells and further enlightening the immune responses in asplenic individuals are required to develop more effective vaccination strategies against OPSI.

Principles of vaccine potency assays

Compared with biologics, vaccine potency assays represent a special challenge due to their unique compositions, multivalency, long life cycles and global distribution. Historically, vaccines were released using in vivo potency assays requiring immunization of dozens of animals. Modern vaccines use a variety of newer analytical tools including biochemical, cell-based and immunochemical methods to measure potency. The choice of analytics largely depends on the mechanism of action and ability to ensure lot-to-lot consistency. Live vaccines often require cell-based assays to ensure infectivity, whereas recombinant vaccine potency can be reliably monitored with immunoassays. Several case studies are presented to demonstrate the relationship between mechanism of action and potency assay. A high-level decision tree is presented to assist with assay selection.

A case series evaluating the serological response of adult asthma patients to the 23-valent pneumococcal polysaccharide vaccine

BACKGROUND

Asthma is an independent risk factor for invasive pneumococcal disease; however, the immune response of adult asthma patients to pneumococcal vaccination is unknown. We explore the serologic response of patients with moderate to severe asthma to the 23-valent pneumococcal polysaccharide vaccine (PPSV23).

METHODS

Seventeen moderate to severe adult asthma patients that had not been vaccinated against pneumococcus over the 5 previous years were prospectively recruited from a tertiary care asthma clinic. Serum was analyzed for the presence of antibodies to five capsular polysaccharide (CP) antigens (6B, 9V, 19A, 19F, 23F) before and 4 weeks after PPSV23 vaccination.

RESULTS

There was a wide variability in baseline anti-CP antibody concentrations. Other than for serotype 19A, our patients frequently have baseline anti-CP antibody concentrations below 1 µg/mL (35% for serotype 19F, 41% for serotypes 9V and 23F, and 59% for serotype 6B). All post-vaccination geometric mean antibody concentrations were significantly higher than baseline. In the 31 tests where the baseline antibody concentration was <1 µg/mL, 77.4% had at least a twofold increase post-vaccination. Despite this, a large proportion of post-vaccination anti-CP antibody concentrations remained <1 µg/mL (51.6% of tests). Nine patients had at least one anti-CP antibody concentration <1 µg/mL post-vaccination. There was no difference between these patients and the remaining eight patients in demographic or clinical variables.

CONCLUSIONS

Patients with moderate to severe asthma have variable baseline and low post-vaccination antibody concentrations to common CP antigens included in the PPSV23 vaccine. The clinical relevance of these observations remains to be determined since the threshold concentration in adults required for clinical protection from invasive pneumococcal disease is uncertain.

Exploring novel sero-epidemiological tools-Effect of different storage conditions on longitudinal stability of microarray slides comprising influenza A-, measles- and Streptococcus pneumoniae antigens

In this study we evaluated the long-term stability of a microarray-based serological screening platform, containing antigens of influenza A, measles and Streptococcus pneumoniae, as part of a preparedness research program aiming to develop assays for syndromic disease detection. Spotted microarray slides were kept at four different storage regimes with varying temperature and humidity conditions. We showed that under the standard storage condition in a temperature-controlled (21°C) and desiccated environment (0% relative humidity), microarray slides remained stable for at least 22 months without loss of antigen quality, whereas the other three conditions (37°C, desiccated; Room temperature, non-desiccated; Frozen, desiccated) produced acceptable results for some antigens (influenza A, S.pneumoniae), but not for others (measles). We conclude that these arrays for multiplex antibody testing can be prepared and stored for prolonged periods of time, which aids laboratory-preparedness and facilitates sero-epidemiological studies.

Practical review of immunizations in adult patients with cancer

Compared with the general population, patients with cancer in general are more susceptible to vaccine-preventable infections, either by an increased risk due to the malignancy itself or immunosuppressive treatment. The goal of immunizations in these patients is therefore to provide protection against these infections, and to decrease the number of vulnerable patients who can disseminate these organisms. The proper timing of immunization with cancer treatment is key to achieving better vaccine protection. As the oncology field continues to advance, leading to better quality of life and longer survival, immunization and other aspects of preventive medicine ought to move to the frontline in the care of these patients. Herein, we review the vaccines most clinically relevant to patients with cancer, as well as special cases including vaccines after splenectomy, travel immunization and recommendations for family members.

Short and long-term immunogenicity and safety following the 23-valent polysaccharide pneumococcal vaccine in juvenile idiopathic arthritis patients under conventional DMARDs with or without anti-TNF therapy

OBJECTIVES

To assess immunogenicity and safety of the 23-valent polysaccharide pneumococcal vaccine (PPV23) in juvenile idiopathic arthritis (JIA) patients under conventional DMARDs with or without anti-TNF therapy. The influences of demographic data, disease activity and treatment on immune response and the potential deleterious effects of vaccine on disease itself were also evaluated.

METHODS

17 JIA patients immediately pre-etanercept (Group 1) and 10 JIA patients on stable dose of methotrexate (Group 2) received one dose of PPV23. All patients were evaluated pre-vaccination, 2 months and 12 months post-vaccination for seven pneumoccocal serotypes. Serology was performed by enzyme immunoassay and the immunogenicity endpoints included seroprotection (SP), seroconversion (SP) and geometric mean concentration of antibodies(GMC). Clinical and laboratorial parameters of JIA were evaluated before and after vaccination.

RESULTS

Groups 1 and 2 were comparable regarding age, gender, disease duration and other DMARDs use (p>0.05). Pre-immunization SP and GMC were alike in patients with and without anti-TNF therapy (p>0.05). The frequencies of patients achieving adequate vaccine response (seroconversion in ≥50% of all serotypes) at 2 months (53 vs. 30%, p=0.424) and 12 months (36 vs. 40%, p=1.0) were similar in JIA patients with and without anti-TNF therapy. Further comparison of patients with and without adequate response at 2 months revealed no influence of demographic, clinical and laboratorial JIA parameters (p>0.05). Serious adverse events were not observed.

CONCLUSIONS

Anti-TNF therapy in JIA patients does not seem to have an additional deleterious effect on short/long-term PPV23 immunogenicity compared to MTX alone and no influence on disease parameters was observed with this vaccine.

Impact of analytical variability on clinical interpretation of multiplex pneumococcal serology assays

The response to pneumococcal vaccination can be used to assess a patient's humoral immune response to polysaccharide antigens. Multiplex assays measuring serotype-specific levels of pneumococcal antibodies are often used for this purpose, and clinical algorithms have been published to assist in the definition of an adequate immune response. We evaluated whether interlaboratory variability in multiplex pneumococcal serology assays would affect the clinical classification of the immune response. Specimens from 57 patients were analyzed at three reference laboratories with different multiplex assays to measure pneumococcal serology. Analytical correlation and clinical agreement in the classification of a patient's vaccination status by the three methods were compared. Although substantial variation in the quantitative antibody levels measured by different laboratories was seen, the qualitative classification of individual serologic results showed a high degree of agreement between labs and the ultimate classification of a patient as "protected" or "nonprotected" was the same for most patients. The majority of discordant classifications were driven by a systematic bias in results from one of the assays rather than by random error. These data suggest that the use of integrated assessments based on multiple serotypes can compensate for much of the analytical variability seen between laboratories. Knowledge of the analytical performance characteristics of a particular assay is most important when evaluating patients with results near clinical cut points.

Quantification of IgM and IgA anti-pneumococcal capsular polysaccharides by a new ELISA assay: a valuable diagnostic and prognostic tool for common variable immunodeficiency

PURPOSE

Existing ways of assessing CVID patients at risk of pulmonary infections are not universally accepted. The need to identify additional prognostic factors allowed us to evaluate the anti-polysaccharide IgA and IgM responses in 125 CVID patients immunized with the 23-valent pneumococcal polysaccharide (PS) vaccine (Pneumovax(®)).

METHODS

We used a new anti-PS23 IgM and IgA ELISA assay, which evaluates a global response to all 23 polysaccharides contained in Pneumovax(®).

RESULTS

Anti-PS23 IgM and/or IgA antibodies were detectable in a minority of CVID patients. Antibody responses were correlated to B cell subpopulations and serum immunoglobulin concentrations. The non responders had a higher incidence of pneumonia and bronchiectasis and responders had the lowest incidence of respiratory complications.

CONCLUSIONS

This new ELISA assay allows for studying vaccine response in patients on Ig replacement therapy. This test also is an additional method of evaluation of specific antibody responses representing a valuable contribution to identify prognostic marker in CVID patients.

Review of guidelines for the prevention and treatment of infection in patients with an absent or dysfunctional spleen: prepared on behalf of the British Committee for Standards in Haematology by a working party of the Haemato-Oncology task force

Guidelines for the prevention and treatment of infection in patients with an absent or dysfunctional spleen were first published by the British Committee for Standards in Haematology (BCSH) in 1996 and formally reviewed in 2002. Although the guidelines originated from discussion within the BCSH, the intended readership is wide given the multidisciplinary nature of the management of hyposplenism.

Post traumatic splenic function depending on severity of injury and management

Because splenectomy has been linked to overwhelming infection years ago, management of splenic traumatisms has become progressively conservative. To assess the immunological function of the spleen in patients with splenic traumatism of different intensity, 43 patients with splenic injury (grades I through V) undergoing either nonoperative management, splenectomy, splenectomy with autotransplantation, or splenic embolization were analyzed for lymphocyte subpopulations and antibody responses to Streptococcus pneumoniae and Haemophilus influenzae vaccinations. Patients treated with splenectomy exhibited a significant decrease in CD4+ T lymphocytes and in Immunoglobulin (Ig) M(high)IgD(low) B cells (related to T-cell independent responses). Median fluorescence intensity of CD54+ in B cells also was reduced. The percent of IgM(high)IgD(low) B cells-a marker of marginal zone function-was inversely correlated with the number of pitted-red blood cells-a marker of red pulp function loss. IgM anti-S pneumoniae identified those patients with a defective rapid response to polysaccharide antigens. These results reinforce the importance of conservative options in the treatment of splenic traumatism for even a severely damaged organ. Despite the significant differences among the groups reported, it remains difficult to predict the IgM response to S pneumoniae vaccine of the individual patients. Better markers to assess splenic function and vaccination response after severe splenic traumatism-even in patients with nonoperative management-might improve risk assessment for overwhelming postsplenectomy infection.

Response to conjugate pneumococcal and Haemophilus influenzae type b vaccines in asplenic patients

We determined the immunogenicity of conjugated Haemophilus influenzae type b and pneumococcal vaccines by quantitative analysis of the antibody response in asplenic patients. To that end, we vaccinated 92 patients with a conjugated Hib vaccine and 54 received two doses of conjugated pneumococcal vaccine (PCV7), followed at six months by a plain polysaccharide pneumococcal vaccine (PPV23). Antibody concentrations were measured before and three weeks after vaccination. After one dose of pneumococcal conjugate vaccine, 46% of the patients reached the antibody threshold of ≥ 1.0 μg/mL for all 7 tested vaccine serotypes. This percentage rose to 54% after the second dose of PCV7 and did not increase further after PPV23. Over 90% of patients had antibody concentrations ≥ 1.0 μg/mL for at least 5 out of the 7 conjugated pneumococcal serotypes after 2 doses of PCV7. For serotypes, included in the PPV23 vaccine only, 25% (PPS3)-100% (PPS19A) of the patients reached antibody concentrations ≥ 1.0 μg/mL after one dose of PPV23. For Hib, 97% of the patients reached the threshold concentration of ≥ 1.0 μg/mL after one dose of vaccine. It can be concluded that the majority of asplenic patients had a sufficient response to conjugated vaccines against Streptococcus pneumoniae and Hib, reflected by a ≥ 1.0 μg/mL antibody response. Inclusion of conjugated pneumococcal polysaccharide vaccines might be of additional value in the vaccination schedule for asplenic patients because of their high immunogenicity.

Streptococcal Infections

The streptococci are a large heterogeneous group of gram-positive spherically shaped bacteria widely distributed in nature. They include some of the most important agents of human disease as well as members of the normal human flora. Some streptococci have been associated mainly with disease in animals, while others have been domesticated and used for the culture of buttermilk, yogurt, and certain cheeses. Those known to cause human disease comprise two broad categories: First are the pyogenic streptococci, including the familiar β-hemolytic streptococci and the pneumococcus. These organisms are not generally part of the normal flora but cause acute, often severe, infections in normal hosts. Second are the more diverse enteric and oral streptococci, which are nearly always part of the normal flora and which are more frequently associated with opportunistic infections.

Memory B cells and pneumococcal antibody after splenectomy

Splenectomized patients are susceptible to bloodstream infections with encapsulated bacteria, potentially due to loss of blood filtering but also defective production of anticarbohydrate Ab. Recent studies propose that a lack of Ab is related to reduced numbers of IgM(+) CD27(+) memory B cells found after splenectomy. To test this, we analyzed CD27(+) memory B cell subsets, IgG, and IgM pneumococcal Ab responses in 26 vaccinated splenectomized subjects in comparison to memory B cell subsets and Ab responses in healthy controls. As shown previously, the splenectomized autoimmune subjects had fewer total, isotype switched, and IgM(+) CD27(+) memory B cells as compared with controls, but there was no difference in memory B cells subsets between controls and splenectomized subjects with spherocytosis. There was no difference between the geometric mean IgG Ab response between normal controls and splenectomized subjects (p = 0.51; p = 0.81). Control subjects produced more IgM Ab than splenectomized autoimmune subjects (p = 0.01) but the same levels as subjects with spherocytosis (p = 0.15.) There was no correlation between memory B cell subsets and IgG or IgM Ab responses for controls or splenectomized subjects. These data suggest that splenectomy alone may not be the sole reason for loss of memory B cells and reduced IgM antipneumococcal Ab. Because subjects with autoimmunity had splenectomy at a significantly older age than participants with spherocytosis, these data suggest that an age-related loss of extra splenic sites necessary for the maintenance or function of memory B cells may lead to impaired immunity in these subjects.

Optimal assessment of the ability of children with recurrent respiratory tract infections to produce anti-polysaccharide antibodies

Specific anti-polysaccharide antibody deficiency (SPAD) is an immune disorder. Diagnostic criteria have not yet been defined clearly. One hundred and seventy-six children evaluated for recurrent respiratory tract infections were analysed retrospectively. For each subject, specific anti-pneumococcal antibodies had been measured with two enzyme-linked immunosorbent assays (ELISAs), one overall assay (OA) using the 23-valent pneumococcal polysaccharide vaccine (23-PPSV) as detecting antigen and the other purified pneumococcal polysaccharide serotypes (serotype-specific assay, SSA) (serotypes 14, 19F and 23F). Antibody levels were measured before (n = 176) and after (n = 93) immunization with the 23-PPSV. Before immunization, low titres were found for 138 of 176 patients (78%) with OA, compared to 20 of 176 patients (11%) with the SSA. We found a significant correlation between OA and SSA results. After immunization, 88% (71 of 81) of the patients considered as responders in the OA test were also responders in the SSA; 93% (71 of 76) of the patients classified as responders according to the SSA were also responders in the OA. SPAD was diagnosed in 8% (seven of 93) of patients on the basis of the absence of response in both tests. Thus, we propose to use OA as a screening test for SPAD before 23-PPSV immunization. After immunization, SSA should be used only in case of a low response in OA. Only the absence of or a very low antibody response detected by both tests should be used as a diagnostic criterion for SPAD.