A radioimmunoassay for immunologic phenomena in pneumococcal disease and for the antibody response to pneumococcal vaccines. I. Method for the radioimmunoassay of anticapsular antibodies and comparison with other techniques

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.

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.

Assessing the Immunogenic Response of a Single Center's Pneumococcal Vaccination Protocol in Sickle Cell Disease

Sickle cell disease (SCD) is the most common inherited hematologic disorder in the United States. Patients with SCD are at increased risk of invasive pneumococcal disease and are reliant on both early penicillin prophylaxis and antipneumococcal vaccination for prevention of infection. Although studies examining vaccine response have demonstrated a drop-off of titer response after 3 years, an optimal vaccination regimen has not been identified. Our study sought to assess the immunogenicity of our center's pneumococcal vaccination strategy, which included Prevnar (PCV-7) (before the introduction of PCV-13) followed by Pneumovax (PPV-23) given routinely at 2 and 5 years of age and then every 5 years thereafter. Our goal was to assess vaccine response in a population of patients with SCD who had received vaccines according to this regimen using multiplex bead analysis. Our study demonstrated a significant percentage of persons with SCD do not maintain a sufficient vaccination response to PPV-23 for 5 years. Our study revealed that only 36% of patients had protective levels of antipneumococcal antibody titers at an average of 37 months after vaccination. Most alarmingly, within the group of patients with subtherapeutic titers, 64% demonstrated vaccine response to <25% of the tested serotypes. These findings were significantly associated with duration of time since last vaccine administration, but the mean age of lack of response was below the 3-year window where vaccine response was previously reported to wane. Our results indicate antipneumococcal immunity may not be optimally maintained using this vaccination strategy in patients with SCD leaving them vulnerable to invasive pneumococcal disease. Many pediatric hematologists stop prophylactic penicillin at 5 years of age making these results alarming. We recommend further investigation into an optimal vaccine schedule and monitoring of antipneumococcal titers in at-risk patients.

Use and clinical interpretation of pneumococcal antibody measurements in the evaluation of humoral immune function

Pneumococcal vaccination is a commonly used technique for assessing the humoral immune status of a patient suspected of having immunodeficiency. Interpretation of what constitutes an adequate response, however, can be challenging. This is due to the complexity of the data generated from serotype-specific assays, historical variations in the assays used to measure pneumococcal antibodies, and varying recommendations on the relevant cut points that define response. In this review, we summarize the historical evolution of assays used for this purpose and discuss the analytical considerations that have influenced published data. We also examine current clinical recommendations for defining an adequate response to vaccination, with a particular focus on the interpretation of serotype-specific data generated by multiplex assays.

Immune defects in the risk of infection and response to vaccination in monoclonal gammopathy of undetermined significance and multiple myeloma

The plasma cell proliferative disorders monoclonal gammopathy of undetermined significance (MGUS) and malignant multiple myeloma (MM) are characterized by an accumulation of transformed clonal plasma cells in the bone marrow and production of monoclonal immunoglobulin. They typically affect an older population, with median age of diagnosis of approximately 70 years. In both disorders, there is an increased risk of infection due to the immunosuppressive effects of disease and conjointly of therapy in MM, and response to vaccination to counter infection is compromised. The underlying factors in a weakened immune response in MGUS and MM are as yet not fully understood. A confounding factor is the onset of normal aging, which quantitatively and qualitatively hampers humoral immunity to affect response to infection and vaccination. In this review, we examine the status of immune alterations in MGUS and MM and set these against normal aging immune responses. We focus primarily on quantitative and functional aspects of B-cell immunity. Furthermore, we review the current knowledge relating to susceptibility to infectious disease in MGUS and MM, and how efficacy of conventional vaccination is affected by proliferative disease-related and therapy-related factors.

The immunogenicity of pneumococcal polysaccharides in infants and children: a meta-regression

The immunogenicity of plain (not conjugated) pneumococcal polysaccharides in children and infants was reviewed using a systematic literature search. Immunogenicity was defined as the fold-increase in serotype specific antibody concentration after a single dose of plain polysaccharide vaccine in unprimed subjects. Meta-regression was used to calculate the influence of study treatments including subject age, sampling time, dosage, immunization route, vaccine composition and study location. Immunogenicity increased with age for all serotypes, and the increase was more rapid in the first 11 months of life. Study location was the next most significant study variable, with higher responses in countries with lower GDP. A flat dose-response curve was observed over a range from 5 to 50 μg polysaccharide. Serotypes 6A, 6B, 14, 19F and 23F were significantly less immunogenic than serotypes 2, 3, 4, 7F, 8, 9N, 9V and 18C in 11 month old children, but continued to increase in immunogenicity with age until reaching similar levels at 6 years. Some proposed T-independent immune mechanisms could explain the differences in serotype immunogenicity.

Induction and measurement of in vivo antibody responses

The capacity of the human immune system to mount an antibody response following in vivo immunization with a protein or polysaccharide antigen is a revealing indication of the overall integrity of both the B and T cell arms of the immune system. As such, in vivo immunization followed by measurement of the antibody response is an appropriate test of immune function in the various acquired and congenital immunodeficiencies and in a host of other conditions affecting the immune system. This unit describes procedures for in vivo immunization and for the measurement of the subsequent immune response using an ELISA technique.

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

Measuring and interpretation of the immune response to pneumococcal polysaccharides is a complex field, owing to the diversity of the pneumococcal polysaccharide capsular types, different vaccine formulations including both polysaccharide and conjugate vaccines, diverse pneumococcal serological assays, lack of immunogenicity data for the conjugate in a number of at-risk groups and complex vaccine schedules. Even the reasons for performing pneumococcal serology can be complex, as assays may be performed for one of two reasons: either to assess an individual's immune status to the pneumococcus or to discriminate between normal and abnormal humoral immunity. This review details a history of the pneumococcal serological assays and provides some insight into when serology can prove useful, including vaccination data for certain at-risk groups.

Enzyme-linked immunosorbent assay for measuring antibodies to pneumococcal polysaccharides for the PNEUMOVAX 23 vaccine: assay operating characteristics and correlation to the WHO international assay

The Merck pneumococcal (Pn) enzyme-linked immunosorbent assays (ELISAs) for measuring antibodies to 12 serotypes (serotypes 1, 3, 4, 6B, 7F, 8, 9V, 12F, 14, 18C, 19F, and 23F) were validated in 1999. Merck Laboratories developed the Pn assays using 10 microg/ml C polysaccharide, 100 microg/ml Pn polysaccharide (PnPs) 25, and 100 microg/ml PnPs 72 for preadsorption of samples, standards, and controls in order to improve the specificity to the Pn serotypes in the vaccine. The Pn assays utilize postimmunization sera obtained from subjects immunized with PNEUMOVAX 23 as standards for measuring immunoglobulin G concentrations in sera obtained from vaccine clinical trials with adults and infants. This material was calibrated to the Pn reference standard serum, 89SF, subjected to the Merck Pn ELISA adsorbants. Comparisons were made between the Merck Pn assay and the international Pn assay, showing moderate agreement between the two assay formats. This work describes the test procedures and operating characteristics of the Merck Pn assays and the results of experiments performed to compare the Merck Pn ELISAs to the international Pn ELISAs.

IgA deficiency: clinical correlates and responses to pneumococcal vaccine

We surveyed historical and laboratory data for 127 IgA-deficient patients (ages 2-67), referred to an immunology clinic; the commonest medical history was recurrent respiratory infections (50%), followed by autoimmunity (28%) asthma and allergy (13%). Fifty-two subjects have been given a pneumococcal vaccination; vaccine responses to 12 serotypes were significantly related to serum IgG2 levels (P = 0.004). Six immunized IgA/IgG2-deficient subjects produced insignificant amounts of antibodies to these pneumococcal serotypes; 10 others with normal IgG2 levels also had subnormal vaccine responses. IgA-deficient patients who had at least one B8 allele (n = 19) had a significantly greater response to this vaccine than the HLA-B8-negative subjects (n = 24) (P = 0.024). There was no relationship between a history of recurring infections and pneumococcal vaccine responses; HLA status was not related to a history of autoimmunity.

A mutation in Bruton's tyrosine kinase as a cause of selective anti-polysaccharide antibody deficiency

Children and adults can have recurrent infection with invasive encapsulated bacterial pathogens such as Streptococcus pneumoniae as a result of a selective inability to respond to polysaccharide antigens. We have identified a mutation in the gene encoding Bruton's tyrosine kinase in a male patient with selective anti-polysaccharide antibody deficiency.

Clostridium difficile recombinant toxin A repeating units as a carrier protein for conjugate vaccines: studies of pneumococcal type 14, Escherichia coli K1, and Shigella flexneri type 2a polysaccharides in mice

Unlike the native protein, a nontoxic peptide (repeating unit of the native toxin designated rARU) from Clostridium difficile toxin A (CDTA) afforded an antigen that could be bound covalently to the surface polysaccharides of pneumococcus type 14, Shigella flexneri type 2a, and Escherichia coli K1. The yields of these polysaccharide-protein conjugates were significantly increased by prior treatment of rARU with succinic anhydride. Conjugates, prepared with rARU or succinylated (rARUsucc), were administered to mice by a clinically relevant dosage and immunization scheme. All conjugates elicited high levels of serum immunoglobulin G both to the polysaccharides and to CDTA. Conjugate-induced anti-CDTA had neutralizing activity in vitro and protected mice challenged with CDTA, similar to the rARU alone. Conjugates prepared with succinylated rARU, therefore, have potential for serving both as effective carrier proteins for polysaccharides and for preventing enteric disease caused by C. difficile.

Antibody response of pneumococcal vaccine: need for booster dosing?

The approved pneumococcal vaccine comprises purified capsular polysaccharide of 23 stereotypes that account for more than 90% of the invasive pneumococcal infections in the USA. It induces adequate anti-polysaccharide IgG antibody levels to most or all of the component polysaccharide antigens in immunocompetent adults. Elderly adults respond about equally well to vaccination as do younger adults. Pneumococcal antibody declines over time, often below 1 month post-vaccination levels, and sometimes about to pre-primary vaccination levels. Second doses of vaccine satisfactorily boost antibody levels in healthy adults, but not in immunocompromised adults or children. The rate of antibody decline differs for the differing capsular stereotypes. In time, pneumococcal antibody wanes in all healthy persons perhaps increasing their risk of serious pneumococcal disease. Elderly and high risk persons face the highest risk of death from invasive pneumococcal disease, supporting the proposition that for these groups revaccination with pneumococcal vaccine at regular intervals may provide the needed increased measure of protection.

Impaired IgG antibody production to pneumococcal polysaccharides in patients with ataxia-telangiectasia

Various factors seem to be etiologic in the susceptibility to sinopulmonary infections in ataxia-telangiectasia (A-T) patients, i.e., low serum and salivary IgA, low serum IgG2, and even aspiration of saliva. S. pneumoniae is a common pathogen responsible from pulmonary infections and impaired antibody response to polysaccharide antigens is seen in patients with IgG2 and IgA deficiency as well as patients with CVID and WAS. We studied IgG-type antibody production to six pneumococcal serotypes in 29 A-T patients by ELISA before and 3-4 weeks after pneumococcal vaccine. The response was considered positive when the antibody titer was >10 U/ml but weak when the titer was 10-20 U/ml. Twenty-two of 29 (76%) patients did not respond to any of the serotypes, 5 (17%) showed a positive response to one serotype, 1 (3.4%) to two serotypes, and 1 (3.4%) to four serotypes. With conversion to gravimetric units (ng IgG/ml) and >1800 ng/ml (300 ng Ab N/ml) considered a positive response, 5 of 29 (17.2%) patients showed a positive response (300 ng ab N/ml) to two or fewer serotypes. All patients tested produced IgG antibody to tetanus toxoid. Sixteen of 27 (59.3%) patients had low IgG2 and four (14.8%) had low IgG3 levels, while 18 (62.1%) of 29 patients had low serum IgA. No correlation was found either between serum Ig isotype levels and antipolysaccharide antibody response or between susceptibility to infection and antibody production. The mechanism responsible for disturbed antipolysaccharide (TI-2 antigen) antibody production in patients with A-T needs to be investigated. It may provide additional information on the function of the ATM gene product and be helpful in clarifying the role of B cells and contribution of T cells in TI-2 responses.

A flow cytometric opsonophagocytic assay for measurement of functional antibodies elicited after vaccination with the 23-valent pneumococcal polysaccharide vaccine

Opsonophagocytosis is the primary mechanism for clearance of pneumococci from the host, and the measurement of opsonophagocytic antibodies appears to correlate with vaccine-induced protection. We developed a semiautomated flow cytometric opsonophagocytosis assay using HL-60 granulocytes as effector cells and nonviable 5, 6-carboxyfluorescein, succinimidyl ester-labeled Streptococcus pneumoniae (serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F) as bacterial targets. The flow cytometric opsonophagocytosis assay was highly reproducible (for 87% of repetitive assays the titers were within 1 dilution of the median titer) and serotype specific, with >/=97% inhibition of opsonophagocytic titer by addition of homologous serotype-specific polysaccharide. In general, opsonophagocytic titers were not significantly inhibited by the presence of either heterologous pneumococcal polysaccharide or penicillin in the serum. The flow cytometric assay could reproducibly measure functional antibody activity in prevaccination (n = 28) and postvaccination (n = 36) serum specimens from healthy adult volunteers vaccinated with the 23-valent pneumococcal polysaccharide vaccine. When compared with a standardized manual viable opsonophagocytic assay, a high correlation (r = 0.89; P </= 0.01) was found between the two assays for the seven serotypes tested. The flow cytometric assay is rapid ( approximately 4 h) with high throughput ( approximately 50 serum samples per day per technician) and provides a reproducible measurement of serotype-specific functional antibodies, making it a highly suitable assay for the evaluation of the immune responses elicited by pneumococcal vaccines.

Use of highly encapsulated Streptococcus pneumoniae strains in a flow-cytometric assay for assessment of the phagocytic capacity of serotype-specific antibodies

A phagocytosis assay for Streptococcus pneumoniae based on flow cytometry (FACS) with human polymorphonuclear cells and human complement was developed for the study of human vaccination antisera. Human prevaccination sera already contain high levels of C-polysaccharide (C-PS) antibodies, which are not protective in humans but which might give false positive results in a flow-cytometry-based assay. Cultures of S. pneumoniae grown to log phase on three consecutive days, followed by heat inactivation, yielded stable and highly encapsulated strains for serotypes 6A, 6B, 14, 19F, and 23F. As a result, only serotype-specific antibodies were able to facilitate phagocytosis of these strains, whereas no phagocytosis was observed with antibodies against C-PS or pneumococcal surface proteins. No, or weak, phagocytosis was observed with human prevaccination sera, whereas in general, postvaccination antisera facilitated phagocytosis. A highly significant correlation was observed between enzyme-linked immunosorbent assay titers and FACS phagocytosis titers (r = 0.98, P < 0.001) for serotype 23F pneumococci with human vaccination antisera. For all serotypes, interassay variation was below 10%. Major advantages of this assay over the classical killing assay are that (i) limited amounts of sera are required (10 microliter per titration curve), (ii) 600 samples can be processed in one day by one person, and (iii) cells can be fixed and measurement of the samples can be performed up to 1 week later.

Isotypes and opsonophagocytosis of pneumococcus type 6B antibodies elicited in infants and adults by an experimental pneumococcus type 6B-tetanus toxoid vaccine

Streptococcus pneumoniae is a major respiratory pathogen of infants, children, and the elderly. Polysaccharide vaccines have been useful in adult populations but do not elicit protective immunity in infants and young children. To enhance their immunogenicity, vaccines of pneumococcal polysaccharides conjugated to proteins are being developed. In this study antibody levels and opsonic activities were compared in sera of infants and adults injected with pneumococcal polysaccharide type 6B (Pn6B) conjugated to tetanus toxoid (TT) (Pn6B-TT). Healthy infants were injected with Pn6B-TT; group A was injected at 3, 4, and 6 months of age, and group B was injected at 7 and 9 months of age. A booster injection was given at 18 months. Adults were injected once. Antibodies were measured by enzyme-linked immunosorbent assay and radioimmunoassay, and their functional activities were measured by opsonophagocytosis of radiolabelled pneumococci. In adults, increases in immunoglobulin M (IgM), IgG, IgA, IgG1, and IgG2 to Pn6B were observed. Infants reached adult levels of IgG1 anti-Pn6B after the primary injections. After the booster injection the infant groups had total IgG- and IgM-Pn6B antibody levels similar to those of adults. After the booster injection, IgG1 was the dominant infant anti-Pn6B isotype and at a level higher than in vaccinated adults, but IgA and IgG2 antibodies remained at very low levels. Opsonic activity increased significantly after Pn6B-TT injections; the highest infant sera showed opsonic activity comparable to that of vaccinated adults. Overall, opsonic activity correlated best with total and IgG anti-Pn6B antibodies (r = 0.741, r = 0.653, respectively; n = 35) and was highest in sera with high levels of all Pn6B antibody isotypes. The results indicate the protective potential of a pneumococcal 6B polysaccharide protein conjugate vaccine for young infants.

Immune responses of splenectomized trauma patients to the 23-valent pneumococcal polysaccharide vaccine at 1 versus 7 versus 14 days after splenectomy

OBJECTIVES

Pneumococcal polysaccharide vaccine is given after emergency splenectomy for trauma to lessen the risk of overwhelming postsplenectomy sepsis. This study was undertaken to determine optimal timing of vaccine administration as determined by serum type-specific polysaccharide antibody concentration titer and functional activity of the resulting antibodies.

METHODS

Fifty-nine consecutive patients undergoing splenectomy after trauma were randomized to receive pneumococcal vaccine postoperatively at 1, 7, or 14 days. Immunoglobulin G serum antibody concentrations against serogroup 4 and serotypes 6B, 19F, and 23F were measured before vaccination and 4 weeks postvaccination. Antibody concentrations were determined by enzyme-linked immunosorbent assay, and functional antibody by opsonophagocytosis. Results were compared with a normal adult control group (n = 12).

RESULTS

Postvaccination enzyme-linked immunosorbent assay immunoglobulin G antibody concentrations for all serogroups and serotypes studied were not significantly different in splenectomized patients and control subjects. Postvaccination functional antibody activity was significantly reduced in early vaccination groups (serotype 6B excepted). However, with the exception of 19F, all titers for the 14-day group approached those of the control subjects (p > 0.05). Fold-increases of opsonophagocytic titers for serogroup 4 and serotypes 6B and 19F showed progressive increases with delay in vaccination. Except for serotype 23F, the number of postsplenectomy patients with opsonophagocytic titers <64 significantly decreased with a delay in vaccination (14 days).

CONCLUSIONS

Postvaccination immunoglobulin G serum antibody concentrations were not significantly different from normal control subjects regardless of the time of vaccination (1, 7, or 14 days). Although concentrations approach normal, functional antibody activity was significantly lower. Better functional antibody responses against the serogroup and serotypes studied seemed to occur with delayed (14-day) vaccination.

Response to pneumococcal immunization in children with and without recurrent infections

Many children with recurrent sinopulmonary infections fail to mount an adequate humoral response following immunization with polysaccharide antigens. At present there are no controlled studies comparing responses to pneumococcal immunization in children with recurrent infections and a healthy, age-matched cohort. Immunological evaluation was performed on 66 children with recurrent sinopulmonary infections, aged 2-5 years (mean 3.06 +/- 0.92). A control group included 28 healthy, age-matched controls (mean 3.14 +/- 0.88 years). Both groups were immunized with 23 valent pneumococcal vaccine, and titers were measured before and 4 weeks after immunization. Antibody levels to 12 pneumococcal serotypes were measured via radioimmunoassay. Geometric preimmunization mean titers in the control group were 215.5 +/- 157 ngAbN/ml rising to 989.5 +/- 745 ngAbN/ml compared to 77.71 +/- 38.4 ngAbN/ml increasing to 446.7 +/- 406 ngAbN/ml in the study group (p < .05). Serotypes 3, 4, 7F, 8, 9N, and 18C were the most immunogenic, while serotypes 6A and 14 were the least. Overall, the control group responded to 7.71 +/- 1.24 serotypes versus 5.1 +/- 2.0 in the study group (p < .05), where postimmunization titers at least doubled and rose to > or = 300 ngAbN/ml. All controls responded to at least five or more serotypes, 26/28 responded to 6 or more. In contrast, only 38/66 (57%) of study patients responded to five or more serotypes, and only 27/66 (41%) responded to at least 6 of 12. Preimmunization titers of greater than 300 ngAbN/ml were present in 30% (102/336) of the control serotypes; however, only 53 of these (52%) doubled post immunization; 22% of the elevated titers decreased post immunization. Markedly elevated titers > or = 500 ngAbN/ml were present in 20% (69/336) of the preimmunization serotypes, only 39% of these doubled post immunization. Twenty-three valent pneumococcal vaccine is immunogenic in young, healthy children. A significant percentage of children with recurrent sinopulmonary infections fail to produce adequate serotype specific antibodies following pneumococcal immunization.

Standardization of an opsonophagocytic assay for the measurement of functional antibody activity against Streptococcus pneumoniae using differentiated HL-60 cells

Host protection against pneumococcal disease i primarily mediated by phagocytosis. We developed and standardized an opsonophagocytic assay using HL-60 cells (human promyelocytic leukemia cells). Fifty-five serum samples were analyzed for the presence of functional antibody against seven pneumococcal serogroups or serotypes (4, 6B, 9V, 14, 18C, 19F, and 23F) by using differentiated HL-60 cells (granulocytes) and peripheral blood leukocytes (PBLs). Six of the 55 serum samples were from unvaccinated adult volunteers, 31 serum samples were from adults who received one dose of the 14-valent or the 23-valent polysaccharide vaccine, and 18 serum samples were from 16-month-old infants who received four doses of an investigational 7-valent polysaccharide-protein conjugate vaccine. The results of an opsonophagocytic assay with HL-60 cells correlated highly with those of an assay with PBLs as effector cells (median r for seven serotypes = 0.87: P < 0.01). Opsonophagocytic titers were compared with the immunoglobulin G antibody concentrations determined by enzyme-linked immunosorbent assay (ELISA). The r values for serogroups or serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F were 0.61, 0.60, 0.67 0.90, 0.61, 0.39, and 0.57, respectively, when HL-60 cells were used as effector cells and 0.56, 0.47, 0.61, 0.90, 0.71, 0.31, and 0.62, respectively, when PBLs were used. The assay requires small amounts of serum (40 microliters per serotype), making this test suitable for assaying infant sera. Culturable cells aid in assay standardization and likely reduce donor-to-donor variability. This standardized assay, in combination with the standardized ELISA, can be used to evaluate current and developing pneumococcal vaccines, in which functional opsonophagocytic antibody activity may correlate with protection against pneumococcal disease.

Immune responses of infants vaccinated with serotype 6B pneumococcal polysaccharide conjugated with tetanus toxoid

BACKGROUND

Streptococcus pneumoniae is a major cause of meningitis, bacteremia, pneumonia and otitis media. Pneumococcal polysaccharides are not immunogenic in infants, but improved immunogenicity of polysaccharide-protein conjugates has been demonstrated. Antibiotic-resistant pneumococci have increased the need for an effective vaccine.

OBJECTIVE

To study the safety and immunogenicity of a pneumococcal type 6B polysaccharidetetanus toxoid conjugate (Pn6B-TT) in infants and to assess the function of antibodies.

METHODS

Healthy infants were injected, Group A at 3, 4 and 6 months (n = 21) and Group B at 7 and 9 months (n = 19). Booster injection was given at 18 months. Antibodies were measured by enzyme-linked immunosorbent assay and radioimmunoassay, and functional activity was measured by opsonization of radiolabeled pneumococci. Nasopharyngeal cultures were obtained.

RESULTS

No significant adverse reactions were observed. Pn6B-IgG (enzyme-linked immunosorbent assay) increased to a geometric mean of 0.62 microgram/ml (P = 0.367, compared with prevaccination titers) in Group A at 7 months and 1.22 micrograms/ml (P < 0.001) in Group B at 10 months. Total Pn6B antibodies (radioimmunoassay) were 44 ng of antibody N/ml (P < 0.053) in Group A and 211 ng of antibody N/ml (P < 0.001) in Group B. A smaller increase in IgM and IgA anti-Pn6B was observed. Reinjection at 18 months elicited booster responses in total and IgG anti-Pn6B; 62% of those in Group A and 79% of those in Group B had > 300 ng of antibody N/ml. Opsonic activity, after initial and booster vaccinations, correlated with Pn6B-antibody titers. Three infants with nasopharyngeal cultures repeatedly positive for serogroup 6 had poor serum IgG responses.

CONCLUSION

Our results demonstrate that Pn6B-TT is safe, elicits functional antibodies and memory responses in infants.

Preimmunization and postimmunization pneumococcal antibody titers in children with recurrent infections

BACKGROUND

Patients with recurrent infections and normal IgG levels may have an abnormal response to pneumococcal polysaccharides. The ability to develop antibodies against different pneumococcal polysaccharides develops gradually in the first years of life, but the sequence of development and the influence of preexisting antibody titers has not been defined.

METHODS

Preimmunization and postimmunization IgG antibody titers against pneumococcal serotypes 3, 7F, 9N, and 14 were evaluated in a population of 100 1- to 18-year-old children referred to a pediatric allergy-immunology clinic because of recurrent respiratory infections. None of the patients had a known immunodeficiency syndrome; all had normal total IgG levels. Postimmunization antibody levels were obtained 4 to 6 weeks after immunization. Patients less than/=5 years of age who failed to develop antibody levels above 200 ng Ab N/mL against any serotype and older patients who failed to develop these levels against a second serotype in addition to serotype 3 were considered for IgG replacement therapy.

RESULTS

Prior to immunization, 50% of 51 patients did not have protective antibody levels against any of the serotypes tested. Immunization induced a high response to serotype 3 in all age groups, but responses to serotypes 7F and 14 increased with age. Five of 78 patients (6.4%) failed to develop protective antibody levels against any serotype tested. Three of these patients had clinical criteria that justified the use of IgG replacement therapy; all improved. Three patients were re-immunized 1 to 2 years after the first immunization and all developed protective levels of antibodies against serotype 3 after the second immunization.

CONCLUSION

We conclude that, although measurement of antibody levels against pneumococcal serotype 3 allows a good differentiation of patients who are able to develop anti-polysaccharide antibodies from those who are not, further studies of the development of specific antibodies against other vaccine serotypes in normal populations of different ages are needed to define a normal response to pneumococcal polysaccharides.

Anti-pneumococcal antibody levels three to seven years after first booster immunization in children with sickle cell disease, and after a second booster

We measured pneumococcal antibody levels in 55 patients (ages 7 to 20 years) with sickle cell disease 3 to 7 years after the first booster immunization. Only 6 of the children had protective levels of antibodies (> 300 ng/ml) against all 12 serotypes tested. Thirty-two children (58%) had suboptimal levels against 1 to 3 serotypes; 17 had suboptimal levels against 4 to 10 serotypes. Ten patients from the latter group (ages 13 to 17 years) received a second booster 6 to 8 years after the first booster immunization, and had a marked increase in antibody levels against all serotypes with the exception of serotypes 3 and 4 in two patients and serotype 6A in one patient.

Immunodeficiency in long-term survivors of acute lymphoblastic leukemia treated with Berlin-Frankfurt-Münster therapy

OBJECTIVE

To determine whether the immune systems of long-term survivors of acute lymphoblastic leukemia (ALL) have persistent immune defects after Berlin-Frankfurt-Münster (BFM) treatment.

STUDY DESIGN

We evaluated the cellular and humoral immune responses of 13 children with ALL in complete remission and off modified protocol treatment for 2 or more years. All patients had received complete immunizations for measles, mumps, rubella, and poliovirus before ALL developed. They were challenged with Haemophilus influenzae type B (Hib) and Pneumococcus vaccines after baseline serum samples were obtained. We also determined in vivo humoral immune responses to bacteria and viruses that cause common pediatric diseases.

RESULTS

Compared with age-matched control subjects, the long-term survivors of ALL had a significant difference in the presence of protective antibodies to measles (p < 0.0001) and polioviruses (p < 0.0001) in their baseline sera; more than half had no protective antibodies to one or more previously administered vaccines or related infections. Most produced protective concentrations of specific antibody after reimmunization, but some were repeatedly unable to make protective antibodies, or mount a normal antibody response, despite natural disease and/or revaccination. Four children had significant infections.

CONCLUSIONS

Long-term survivors of ALL who had BFM treatment may have persistent immune defects with respect to common childhood bacterial and viral diseases they previously had, or vaccines they received.

Immunologic Defects in Patients with Chronic Recurrent Sinusitis: Diagnosis and Management

Twenty patients with chronic refractory sinusitis or rhinitis were identified to have immune defects on the basis of total immunoglobulin level, immunoglobulin G subclass, and vaccine response. Eight patients were immunoglobulin A deficient, five had low immunoglobulin levels with vaccine hyporesponse, and four had low immunoglobulin levels with normal vaccine responses. Three subjects showed isolated immunoglobulin G1 deficiency. Demographic variables such as age, sex, infection pattern, and any other related disorders were studied retrospectively, which may have contributed to the diagnosis. An immunologic screen was essential for the diagnosis of immunodeficiency in these patients. Treatment options included prophylactic antibiotics, management of associated allergies, functional endoscopic sinus surgery, and replacement therapy with immunoglobulin in selected patients.

Immunology in the pediatrician's office

The development of antibody-mediated immunity is reflected in the maturation of B lymphocytes, in the changing levels of total immunoglobulins, and in the development of specific antibodies first to proteins and then sequentially to different types of polysaccharides. The measurement of anti-pneumococcal antibodies allows us to recognize specific antibody deficiencies, which need to be differentiated from normal developmental phases in the maturation of antibody-mediated immunity. The recognition of the late phase of IgE mediated allergic reactions is important to understanding the chronic manifestations of allergy. Chronic manifestations of allergy are frequently missed because they do not appear to be clearly related to acute triggers of allergic reactions. These conditions can be appropriately diagnosed, prevented, and treated, however, when the mechanisms of the late manifestations of allergy are understood. The integration of knowledge about the development of immunity and of allergic diseases enhances the pediatrician's ability to care for patients with immunologic abnormalities.

Immune responses of young mice to pneumococcal type 9V polysaccharide-tetanus toxoid conjugate

Pneumococcal type 9V polysaccharide (PS), contained in the current pneumococcal vaccine, induces only a weak antibody response in young children and therefore is not an effective vaccine for young children. To increase its immunogenicity, a conjugate of PS to a protein carrier, tetanus toxoid (TT), was prepared. To quantify the immune response, mouse anti-9V PS immunoglobulin G (IgG) and IgM reference standards were established. Young mice immunized at 2 weeks of age produced IgM antibody in response to 9V PS alone or 9V PS conjugated to TT. However, only the 9V PS-TT conjugate induced an IgG antibody response and an anamnestic effect. Thus, a covalent linkage between TT and 9V PS was required for isotype switching from IgM to IgG. 9V PS-TT adsorbed with aluminum hydroxide adjuvant resulted in a fivefold or greater increase in the IgG antibody level. We also studied the effect of maternal immunization on the immune response of young mice to 9V PS-TT. Maternal immunization before mating or before mating and during gestation primed 2-week-old progeny given two injections of 9V PS-TT to produce more IgM antibody than progeny from unimmunized mothers. The IgG antibody level of neonates at birth was similar to that observed in the mothers and was probably passive antibody. These results indicate that maternal immunization with an optimum dose of a PS-protein conjugate before and/or during pregnancy, followed by immunization of the offspring with the conjugate, could provide young children with an enhanced IgM antibody response to pneumococcal PSs.

Immunogenicity of the 23-valent pneumococcal polysaccharide vaccine in Alaska Native chronic alcoholics compared with nonalcoholic Native and non-Native controls

PURPOSE

This study was designed to evaluate the immunogenicity of the 23-valent pneumococcal polysaccharide vaccine in Alaska Native chronic alcoholics and compare these responses with those in age- and sex-matched nonalcoholic, Native and non-Native control subjects.

PATIENTS AND METHODS

Native alcoholic patients were recruited from the inpatient medical service and outpatient clinics. Healthy age- and sex-matched Alaska Native and non-Native nonalcoholics were recruited from hospital employees. At the initial visit, a standardized questionnaire, the Alcohol Dependency Scale, was administered to all participants. Participants were examined for liver diseases; blood was drawn for liver function tests and prevaccination pneumococcal antibody levels. Charts of all Native participants were reviewed for alcohol-related diseases. Participants received one dose of the 23-valent pneumococcal vaccine at the time of the initial visit and returned 20 to 55 days after immunization for liver function tests and pneumococcal antibody level measurement. Serotype-specific pneumococcal antibody levels were measured by radioimmunoassay. Logistic regression analysis was used to examine the proportion of persons whose serotype-specific antibody level doubled following vaccination. A model including adjustments for age, sex, and initial antibody level was used to examine the effect of alcohol status and ethnicity on response to the vaccine. Eighty-five persons completed the study. Of these, 41 were chronic alcoholics and 44 were nonalcoholic. Of these, 21 were Alaska Natives and 23 were non-Natives.

RESULTS

Before vaccination, the geometric mean titers (GMTs) were similar in all 3 groups but were slightly higher in Native alcoholic participants for 11 of 12 serotypes tested. For 11 or more serotypes tested, 46% of alcoholics and 27% of nonalcoholics had total antibody levels at or above 500 nanograms of antibody nitrogen per milliliter (p = 0.11). After vaccination, the GMTs were higher in nonalcoholic than in alcoholic participants for serotypes 3, 7F, and 19F (p < 0.05). When Natives and non-Natives were compared, non-Natives had higher antibody levels than Native participants for 10 of 12 serotypes. After vaccination, 83% of alcoholics and 91% of nonalcoholics had pneumococcal antibody levels of more than 500 nanograms of antibody nitrogen per milliliter for at least 11 serotypes. When responses consisting of a twofold or greater increase in antibody level were compared, a greater proportion of nonalcoholics than alcoholics responded to serotypes 3, 4, 7F, 8, and 19F. This difference was significant for types 3 and 19F only (p < 0.05). In alcoholics there was a direct correlation between pneumococcal antibody level and age both before and after vaccination. This was significant before vaccination for serotypes 4, 6B, 18C, and 23F, and after vaccination for these types and for types 1 and 19F. In nonalcoholics there was a correlation between age and antibody response, following vaccination, for serotype 9N and 18C. Alcoholic males had antibody levels higher than that in females for most serotypes, but significantly so only for serotype 12F before vaccination, and for type 14 after vaccination. There were no sex differences seen among nonalcoholics, and no differences in response to vaccine could be detected in patients with or without liver dysfunction.

CONCLUSION

In this study of Alaska Natives with chronic alcoholism, Native and non-Native participants responded adequately to immunization with the 23-valent pneumococcal vaccine, although significant differences in some serotypes were evident.

Immunogenicity of conjugate vaccines consisting of pneumococcal capsular polysaccharide types 6B, 14, 19F, and 23F and a meningococcal outer membrane protein complex

In an effort to prepare pneumococcal (Pn) capsular polysaccharide (Ps) vaccines that would be immunogenic in infants, covalent conjugates were prepared for Pn types 6B, 14, 19F, and 23F. Each Ps type was covalently bound to an outer membrane protein complex from Neisseria meningitidis serogroup B and evaluated for immunogenicity in mice and infant monkeys. The conjugates induced specific anti-Ps antibody responses in mice and in infant rhesus and African green monkeys; a conjugate of 6B and outer membrane protein complex was immunogenic at Ps doses as low as 20 ng. Although low levels of the Pn group-common cell wall polysaccharide were present in all type-specific Ps preparations, anti-cell wall polysaccharide responses induced by covalent conjugates were < 1% of the total anti-Ps response after two doses of vaccine. In contrast, the anti-cell wall polysaccharide response of a noncovalent conjugate represented 41% of the anti-Ps response after two doses. Relative T-cell dependence, a requirement for the human target population of infants less than 18 months old, was demonstrated for all four Pn Ps conjugates in an athymic mouse model. Therefore, these Pn Ps-outer membrane protein complex conjugate vaccines are excellent candidates for evaluation in human infants.

Synthesis of a conjugate vaccine composed of pneumococcus type 14 capsular polysaccharide bound to pertussis toxin

Type 14 is one of the common types isolated from patients of all ages with infections caused by Streptococcus pneumoniae. Its capsular polysaccharide (Pn14) is composed of a neutrally charged tetrasaccharide repeat unit. Pn14 does not elicit protective levels of antibodies in infants and children and is a less than optimal immunogen of the 23-valent vaccine for adults. Pertussis toxin (PT) is both a virulence factor and protective antigen of Bordetella pertussis: it is not soluble at neutral pH and forms insoluble complexes with acidic polysaccharides. Both Pn14 and PT are potential components of vaccines for infants and children. Accordingly, a synthetic scheme was devised to prepare a conjugate of Pn14 and PT. An adipic acid hydrazide derivative of Pn14 was bound to PT at pH 3.9 by carbodiimide-mediated condensation. The conjugation procedure inactivated the PT as assayed by CHO cell and histamine-sensitizing activity. The Pn14-PT conjugate elicited antibodies in mice to Pn14 at levels estimated to be protective in humans and elicited neutralizing antibodies to PT. We plan to evaluate Pn14-PT clinically.

Purification and immunogenicity of genetically obtained pneumolysin toxoids and their conjugation to Streptococcus pneumoniae type 19F polysaccharide

As part of an ongoing study concerned with improving human vaccines against Streptococcus pneumoniae, the genes for two defined pneumolysin (PL) toxoids (pneumolysoids), Pd-A (PL with a Cys----Gly substitution at amino acid 428) and Pd-B (PL with a Trp----Phe substitution at position 433), were inserted into the high-expression vector pKK233-2 in Escherichia coli and the pneumolysoids were purified. Groups of mice which had been immunized with either Pd-A, Pd-B, or native PL purified from S. pneumoniae were then challenged either intranasally or intraperitoneally with virulent pneumococci. Mice in all immunized groups survived significantly longer than sham-immunized controls. Both pneumolysoids were more effective than PL as protective immunogens. Pneumolysoid Pd-B was conjugated covalently with pneumococcal type 19F capsular polysaccharide (19F PS), and the immunogenicities of both the protein and the PS moieties of the conjugate in mice were determined. Significant anti-PL titers were obtained, and the immunogenicity of the 19F PS moiety was markedly enhanced compared with that of unconjugated PS. Conjugation also appears to have converted the 19F PS into an antigen capable of inducing a booster effect. These results support the notion that the efficacy of human, PS-based antipneumococcal vaccines might be improved by supplementation with pneumolysoid in the form of a covalent pneumolysoid-PS conjugate.

Western blot analysis of immunoglobulin G antibodies to pneumococcal protein antigens in healthy adults

Using the Western Blot technique, sera from apparently healthy individuals were shown to contain antibodies against pneumococcal protein antigens of different molecular weights. A remarkable correlation was found to exist between the number of protein bands stained and the level of antibodies to type-specific carbohydrate antigens and C-polysaccharide. The findings suggest that the presence of antibodies against protein antigens reflects past infection with pneumococci.

Quantitative relationship between anticapsular antibody measured by enzyme-linked immunosorbent assay or radioimmunoassay and protection of mice against challenge with Streptococcus pneumoniae serotype 4

We have recently shown that a substantial proportion of antibody to pneumococcal polysaccharide as measured by enzyme-linked immunosorbent assay (ELISA) or radioimmunoassay is removed by adsorption with pneumococcal cell wall polysaccharide (CWPS). The present study was undertaken to validate the hypothesis that only serotype-specific antibody that remains after adsorption with CWPS provides protection against pneumococcal infection. Serum samples were obtained from human subjects before and after they had been vaccinated with pneumococcal polysaccharide vaccine. Antibody to Streptococcus pneumoniae serotype 4 was measured by ELISA without adsorption or after adsorption of serum with CWPS. Groups of mice were injected with graded doses of serum and then challenged intraperitoneally with 10, 100, or 1,000 50% lethal doses (LD50) of S. pneumoniae serotype 4. Without adsorption, prevaccination sera from five healthy adults appeared to contain up to 33 micrograms of antibody to S. pneumoniae serotype 4 antigen per ml; adsorption with CWPS removed all detectable antibody, and pretreating mice with up to 0.1 ml of these sera (less than or equal to 3.3 micrograms of antibody) failed to protect them against challenge with 100 LD50. In contrast, postvaccination sera contained 2.9 to 30 micrograms of antibody per ml that was not removed by adsorption. Diluting sera to administer desired amounts of serotype-specific immunoglobulin G showed a significant relationship between protection and antibody remaining after adsorption (P less than 0.05 by linear regression analysis); 150 ng was uniformly protective against 1,000 LD50, and 50 ng was protective against 100 LD50. These studies have, for the first time, quantitated the amount of serotype-specific antibody that protects mice against challenge with S. pneumoniae type 4. In light of these observations, it is necessary to reassess current concepts regarding the presence of antipneumococcal antibody in the unvaccinated population, responses to pneumococcal vaccination, and protective levels of immunoglobulin G.

Monitoring of the response of elderly individuals to pneumococcal vaccination with the aid of a novel ELISA

An ELISA for assessing pneumococcal anticapsular antibodies in human sera is described. Sensitization was carried out by adding to avidin-coated polystyrene plates biotinylated capsular polyosides. This ELISA was used for the determination of anticapsular antibody levels in pre- and post-immunization sera from 20 elderly individuals. The anticapsular antibody titres differed significantly in sera taken prior to and after vaccination. Eighteen of the 20 sera tested showed mean fold increases of the antibody level greater than 2 (2.1 to 21.0) as a result of vaccination. Since morbidity and mortality rates from S. pneumoniae infections are high in the elderly, immunization should be systematically performed. However, the elderly subject is frequently immunosuppressed, and it is therefore advisable to control the result of the vaccination, using a simple procedure, such as the one described here.

The effects of capsular polysaccharide on the capacity of serum to support the killing of type 3 Streptococcus pneumoniae by human neutrophils

To assess the effects of purified capsular polysaccharide from type 3 S. pneumoniae (PPS-3) on the capacity of serum to support pneumococcal killing by human neutrophils, varying concentrations of PPS-3 (0.01-100 micrograms/ml) were incubated (4 degrees C) with pooled serum for 30 min, and the resulting preparation, termed absorbed serum, was evaluated in bactericidal and phagocytic assays. The ability of serum to promote the killing of type 3 S. pneumoniae was significantly reduced at greater than or equal to 1.0 micrograms/ml PPS-3; similarly, serum absorbed with greater than or equal to 1.0 micrograms/ml PPS-2 failed to support the killing of type 2 S. penumoniae. However, the impact of these penumococcal polysaccharides was serotype specific, since the killing of type 3 S. pneumoniae was not impaired in serum absorbed with PPS-2, and the killing of type 2 S. pneumoniae was not attenuated in serum treated with PPS-3. The failure of serum absorbed with PPS-3 to promote the killing of type 3 S. pneumoniae was primarily a consequence of impaired bacterial ingestion; the reduction in phagocytosis was associated with parallel changes in superoxide anion release. The defects in phagocytosis and killing induced by PPS-3 were not associated with alterations in classical or alternative complement pathway activity; however, they were highly correlated with changes in serum antibody levels to the polysaccharide. The addition of polyclonal human IgG to serum treated with PPS-3 did not restore its capacity to support killing; however, preopsonization of the bacterium with the IgG preparation did partially correct the deficiency. Finally, neutrophils preincubated with serum containing greater than or equal to 10.0 micrograms/ml PPS-3 exhibited an impaired bactericidal activity against type 3 S. pneumoniae. Thus, these studies demonstrate that the presence of PPS-3 decreases the capacity of serum to support the killing of type 3 S. pneumoniae by absorbing immunoglobulins and by generating factors that interfere with neutrophil function.

Pneumococcal vaccination: work to date and future prospects

In our opinion, the conclusion from all these studies is that pneumococcal polysaccharides in the form in which they have been administered are relatively poor immunogens when compared, for example, to certain proteins such as tetanus toxoid. Had pneumococcal vaccination been the success that might reasonably have been predicted, there would be no argument, this many years later, over its merits. Although polysaccharide vaccines appear to have been effective in mass vaccination programs and in epidemic situations where presumably healthy adults have been involved, it has been more difficult to document their efficacy in individuals who are most in need of them, namely those with aberrant or senescent immune systems. There seems to be no disagreement that antibody at some concentration (the precise level remains to be determined) will, in general, be associated with protection, although in any one individual, for a variety of reasons, infection with a vaccine serotype might still occur. Thus, the clear direction for the future should be not to argue further the merits of currently available vaccine preparations, but rather to work rapidly and efficiently to develop and test new and more effective polysaccharide antigens. Studies in the past 10 years have shown that the polyribosyl ribitolphosphate (PRP) of Haemophilus influenzae type b is a far more effective antigen when conjugated to diphtheria toxoid. For example, in a study in our laboratory, vaccination of healthy young adults with PRP-conjugated diphtheria toxoid yielded serum antibody levels 10- to 100-fold higher than after PRP alone. Responses may be even better if other proteins are used.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum antibody response in adult volunteers elicited by injection of Streptococcus pneumoniae type 12F polysaccharide alone or conjugated to diphtheria toxoid

Conjugates of an uronic acid-containing capsular polysaccharide (CP), pneumococcous type 12F (Pn12F) bound to diphtheria toxoid (DT), were studied for safety and immunogenicity in adult volunteers. In mice, these conjugates, prepared with the same lot of DT and Pn12F-40234-006, a homogenous CP of high molecular weight, or Pn12-812408, a polydisperse CP with lower-molecular-weight material, were more immunogenic than the Pn12F alone and had T-cell dependent properties (A. Fattom, W. F. Vann, S.C. Szu, A. Sutton, X. Li, B. Bryla, G. Schiffman, J. B. Robbins, and R. Schneerson, Infect. Immun. 56:2292-2298, 1988). Adult volunteers, randomized into three groups, were injected either with one of these two conjugates or with Pnu-Imune, the 23 valent pneumococcus vaccine containing 25 micrograms of Pn12F as one of its components. Volunteers were injected two times, 4 weeks apart, with the Pn12F-DT conjugates and once with the Pnu-Imune. Side reactions following injection of the conjugates of Pnu-Imune were mild and short-lived. At 4 weeks and at 7 months after the first injection, higher levels of Pn12F antibodies were found in the volunteers injected with the conjugates than in the Pnu-Imune group (P less than 0.001). The conjugate prepared with the higher-molecular-weight Pn12F elicited higher levels of antibodies than the conjugate prepared with a lower-molecular-weight Pn12F preparation (P = 0.05). Both conjugates elicited about a 13-fold rise in DT antibodies.

Analysis of the optimal conditions for the adsorption of type III pneumococcal polysaccharide to plastic for use in solid-phase ELISA

An economical, sensitive enzyme-linked immunosorbent assay (ELISA) method for measuring all isotypes of immunoglobulin specific for type III pneumococcal polysaccharide (SSS-III) is described, using 96-well polystyrene microtiter plates coated directly with antigen. To achieve substantial binding of SSS-III to plastic plates, the polysaccharide had to be dissolved in a buffer (0.1 M Hepes) of pH 4.0 or less. Optimal conditions for adsorption of SSS-III to plates were found to be pH 3.5 and a concentration of 1.0 microgram SSS-III/ml (0.1 microgram/well). Under these conditions, murine anti-SSS-III polyclonal or monoclonal antibodies could be detected to a limit of about 5-10 ng/ml. The implications of these findings for assays that use mixtures of polysaccharides adsorbed to plastic plates are discussed.

Relationship between serum IgG2 concentrations and antibody responses to pneumococcal polysaccharides in children with chronic chest symptoms

We measured IgG-class antibodies to 12 pneumococcal antigens pre- and post-immunization with polyvalent pneumococcal vaccine in 31 children who had experienced chronic chest symptoms. The purpose of the study was to determine the relation of IgG subclasses, especially IgG2, to the subjects' antibody responses to bacterial polysaccharide antigens, to see if measuring IgG subclasses would predict these responses. Twenty-nine children (90%) had low or low-normal levels of one or more IgG subclasses, including 20 out of 31 (65%) with low or low-normal levels of IgG2. Children studied had a relatively poor increase in levels of antibody to 10 of the 12 pneumococcal vaccine antigens investigated. Both pre- and post-immunization antibody levels were related to pre-immune serum concentrations of IgG2. Pre-immunization antibody levels were strongly related to post-immunization levels; when post-immunization antibody levels were adjusted for pre-immunization levels by partial correlation, the correlation between anticapsular antibody level post-immunization and IgG2 was no longer significant. Thus, in children with chronic chest symptoms, levels of antibody measured at a random interval after natural exposure to these bacterial polysaccharide antigens are related to levels of IgG2 subclass, but antibody increases after vaccination appear to be affected more by other factors.

Synthesis and immunological properties of conjugates composed of group B streptococcus type III capsular polysaccharide covalently bound to tetanus toxoid

A synthetic scheme for covalently binding group B streptococcus type III to tetanus toxoid (TT), using adipic acid dihydrazide as a spacer, is described. Type III alone or as a conjugate with TT was injected subcutaneously into laboratory mice, and the type-specific and TT antibody responses elicited by these immunogens were assayed. Type III-TT elicited significantly higher levels of type-specific antibodies after each immunization than did the type III alone. These levels were related to the dosage of the conjugate, enhanced by Freund adjuvant, and exhibited booster responses. Type III alone elicited only immunoglobulin M (IgM) antibodies in Swiss albino mice and mostly IgM and low levels of IgG antibodies of the IgG3 subclass in BALB/c mice. Type III-TT conjugates, in contrast, elicited mostly IgG antibodies in both strains of mice. IgA type III antibodies were not detected. The first two immunizations with the conjugates elicited type III antibodies in the IgG1 and in the IgG3 subclasses. Low levels of IgG2a type III antibodies were detected after a third injection of type III-TT. Conjugate-induced antibodies facilitated opsonization of group B streptococcus type III organisms and did not react with the structurally related pneumococcus type 14. TT alone or as a component of type III-TT induced mostly antibodies of the IgG class: IgG1 levels were the highest of the four subclasses. No IgA TT antibodies were detected. The conjugation procedure, therefore, enhanced the immunogenicity of and conferred T-cell dependent properties to the type III while preserving the immunogenicity of the TT component. The T-cell dependent properties of the conjugates were responsible for stimulating IgG type III antibodies which could be boosted. Evaluation of type III-TT conjugates in antibody-negative women of child-bearing age is planned.

Quantitation of IgG antibody to Streptococcus pneumoniae vaccine by ELISA and FAST-ELISA using tyraminated antigen

We examined two ELISA methods for measuring antibodies to Streptococcus pneumoniae using tyraminated S. pneumoniae polysaccharide types 3, 7N, 9F and 14 as antigens. The ELISA has the usual format with a relatively long incubation time whereas the FAST-ELISA has a short incubation time and employs a different solid-phase configuration. We showed that both techniques can be used for the detection of antibodies to S. pneumoniae polysaccharides. Although its analytical sensitivity is about 1/10 of that of the ELISA, the FAST-ELISA is sufficiently sensitive to distinguish protective from unprotective levels of antibodies to the types of S. pneumoniae studied. In studying pre- and post-immunization response, we showed that type 3 is the most immunogenic.