Dose-ranging study of a single injection of pneumococcal conjugate vaccine (1 ×, 2 ×, or 4 ×) in healthy subjects aged 70 years or older.

Healthy adults aged ≥ 70 years (N=443) with no history of pneumococcal vaccination received 7- or 9-valent pneumococcal conjugate vaccine (PCV7 or PCV9) at 1 × (PCV7 only), 2 × (PCV7+PCV9), or 4 × (2 × PCV7+2 × PCV9) dosage in a randomised, open-label study evaluating pneumococcal protein conjugate vaccine (PnC). Controls received 23-valent pneumococcal polysaccharide vaccine (PPV). Both geometric mean concentration enzyme-linked immunosorbent assay and opsonophagocytic activity antibody titres assessed 1 month after vaccination were significantly increased over baseline titres for all PCV7 serotypes, with a trend toward a dose-dependent immune response. Local reactions for the 4 × dose, but not the 2 × dose, were statistically significantly higher than for the 1 × dose. No treatment-related serious adverse events occurred.

Comparison of pneumococcal conjugate polysaccharide and free polysaccharide vaccines in elderly adults: conjugate vaccine elicits improved antibacterial immune responses and immunological memory.

BACKGROUND: High functional antibody responses, establishment of immunologic memory, and unambiguous efficacy in infants suggest that an initial dose of conjugated pneumococcal polysaccharide (PnC) vaccine may be of value in a comprehensive adult immunization strategy. METHODS: We compared the immunogenicity and safety of 7-valent PnC vaccine (7vPnC) with that of 23-valent pneumococcal polysaccharide vaccine (PPV) in adults >/=70 years of age who had not been previously vaccinated with a pneumococcal vaccine. One year later, 7vPnC recipients received a booster dose of either 7vPnC (the 7vPnC/7vPnC group) or PPV (the 7vPnC/PPV group), and PPV recipients received a booster dose of 7vPnC (the PPV/7vPnC group). Immune responses were compared for each of the 7 serotypes common to both vaccines. RESULTS: Antipolysaccharide enzyme-linked immunosorbent assay antibody concentrations and opsonophagocytic assay titers to the initial dose of 7vPnC were significantly greater than those to the initial dose of PPV for 6 and 5 of 7 serotypes, respectively (P < .01 and P < .05, respectively). 7vPnC/7vPnC induced antibody responses that were similar to those after the first 7vPnC inoculation, and 7vPnC/PPV induced antibody responses that were similar to or greater than antibody responses after administration of PPV alone; PPV/7vPnC induced significantly lower antibacterial responses, compared with those induced by 7vPnC alone, for all serotypes (P < .05). CONCLUSION: In adults, an initial dose of 7vPnC is likely to elicit higher and potentially more effective levels of antipneumococcal antibodies than is PPV. In contrast with PPV, for which the induction of hyporesponsiveness was observed when used as a priming dose, 7vPnC elicits an immunological state that permits subsequent administration of 7vPnC or PPV to maintain functional antipolysaccharide antibody levels.

Evaluation of the indirect effects of a pneumococcal vaccine in a community-randomized study.

When a sufficiently high proportion of a population is immunized with a vaccine, reduction in secondary transmission of disease can confer significant protection to unimmunized population members. We propose a straightforward method to estimate the degree of this indirect effect of vaccination in the context of a community-randomized vaccine trial. A conditional logistic regression model that accounts for within-randomization unit correlation over time is described, which models risk of disease as a function of community-level covariates. The approach is applied to an example data set from a pneumococcal conjugate vaccine study, with study arm and immunization levels forming the covariates of interest for the investigation of indirect effects.

Safety and antibody persistence following Haemophilus influenzae type b conjugate or pneumococcal polysaccharide vaccines given before pregnancy in women of childbearing age and their infants.

BACKGROUND: Immunization of healthy women before pregnancy is a potential approach to providing increased levels of maternal antibody to newborns to protect them from infections occurring during the perinatal period and first months of life. METHODS: Healthy nonpregnant Pima Indian women of childbearing age were randomized to receive one of two Haemophilus influenzae type b (Hib) conjugate vaccines [HbOC or Hib-meningococcal outer membrane protein complex (OMP)] or a 23-valent pneumococcal polysaccharide vaccine (PnPs). Infants received Hib-OMP vaccine at 2, 4 and 12 months of age. Vaccine safety and immunogenicity was evaluated in the women and their infants. RESULTS: Anti-polyribose ribitol phosphate antibody titers were significantly higher in women in both Hib conjugate vaccine groups than in the pneumococcal vaccine group throughout the 37-month observation period. Antibody responses to HbOC vaccine were significantly higher than those to Hib-OMP. A subsequent booster dose of each Hib conjugate vaccine induced reactions and antibody responses similar to those of the first dose. Infants born to mothers immunized with Hib vaccines compared with PnPs had significantly higher polyribose ribitol phosphate-specific IgG antibody titers at birth and 2 months of age but lower antibody responses to Hib-OMP at 6 months and similar titers before and after boosting with Hib-OMP at 1 year of age. By contrast women immunized with PnPs did not have significantly elevated concentrations of pneumococcal-specific antibody at delivery, and their infants had pneumococcal antibody titers similar to those of infants born to mothers who did not receive pneumococcal vaccine before pregnancy. CONCLUSION: Hib conjugate vaccine given to women before pregnancy significantly increased the proportion of infants who had protective Hib antibody levels at birth and 2 months of age.

A multi-laboratory evaluation of an enzyme-linked immunoassay quantitating human antibodies to Streptococcus pneumoniae polysaccharides.

An enzyme-linked immunoassay (EIA) is described and evaluated which quantitates human antibodies to serotype specific S. pneumoniae polysaccharide (PnPs) in human sera. Based on the observations previously described by Koskela (1), native PnPs are used as coating antigens and sera are absorbed with a soluble pneumococcal absorbant material containing C-polysaccharide (CPs) to ensure measurement of serotype specific anti-PnPs antibodies. The robustness of this method was evaluated by ten laboratories using the same reagents, protocol, and five human serum samples. Reproducible antibody values were obtained for IgM, IgG, and IgA antibodies to five different PnPs serotypes, 3, 6B, 14, 19F, and 23F. The overall mean percent coefficients of variation in this interlaboratory study for all five selotype specific anti-PnPs determinations with the five coded sera were 30% for IgG, 3/% for IgM, and 36% for IgA. This assay can be standardized for quantitation of serotype specific anti-PnPs antibodies, allowing comparison of antibody values in vaccine trials evaluating pneumococcal vaccines.

Design of a group-randomized Streptococcus pneumoniae vaccine trial.

A group-randomized, double-masked, phase III trial of a Streptococcus pneumoniae conjugate vaccine is being conducted in American Indian populations in the southwestern United States. Approximately 9000 infants will be enrolled in the primary efficacy cohort with vaccine allocation determined by community of residence. The trial is designed to continue until 48 cases of invasive pneumococcal disease due to vaccine serotypes have accumulated. Thirty-eight geographically and socially distinct areas were randomized within blocks formed by population size and geographic location. This design affords the opportunity to capture the effects of herd immunity (indirect effects) by estimating the impact of the vaccine intervention on nonimmunized infants. Group-randomized trials have challenging design and analysis features, many of which are discussed here in the context of the first such trial designed to lead to licensure of a drug or biologic in the United States.

Geographical differences in invasive pneumococcal disease rates and serotype frequency in young children.

The development of glycoconjugate vaccines for Streptococcus pneumoniae that are effective in very young children has renewed interest in identification of which among the more than 90 pneumococcal serotypes are most likely to cause invasive pneumococcal disease (IPD). Serotype distribution is thought to vary geographically, even between regions as socioeconomically similar as western Europe and North America. To explain these variations, we note the considerable variation that exists between reported rates of IPD in young children in the USA and west European countries. We postulate that this variation is attributable to different blood-culture rates and practices, and that mild IPD is probably underdiagnosed and under-reported in western Europe. On the basis of a comparison of serotype distributions between the two regions, we also postulate that those serotypes found at similar frequencies in both regions are virulent and rarely cause mild disease. As a result, reported distributions of IPD serotypes, especially when expressed as percentages, might be strongly skewed by the distribution of clinical presentations in a particular study population.

Inhibition of ATP-induced surfactant exocytosis by dihydropyridine (DHP) derivatives: a non-stereospecific, photoactivated effect and independent of L-type Ca2+ channels.

Purinergic stimulation of surfactant secretion via exocytosis of lamellar bodies is mediated by an elevation of the intracellular Ca2+ concentration ([Ca2+](i)). We tested the dihydropyridine (DHP) analogues isradipine (+/-enantiomers), nifedipine and Bay K 8644 (racemic forms) on ATP-induced surfactant secretion and [Ca2+](i) in single type II cells, using FM1-43 and fura-2 fluorescence. None of the DHPs (2 microM) had an effect on ATP-induced surfactant secretion in the dark. They did, however, inhibit secretion in a concentration-dependent manner during illumination, particularly with UV light. This effect was not stereospecific, because it was mimicked by (-)-isradipine. In addition, (+)- or (-)-isradipine, but not nifedipine or Bay K 8644, elicited a slow increase of [Ca2+](i) during illumination with UV light, which was reversible by exposure to dark. None of the DHPs inhibited the ATP-induced Ca2+ signal. In perforated patch clamp experiments, depolarizing voltage steps did not induce L-type Ca2+ (Sr(2+)) currents, even in the presence of the agonist Bay K 8644 (1 microM). We conclude that impairment of ATP-induced surfactant secretion by all tested DHPs and alterations of Ca2+ homeostasis by isradipine are photoactivated effects, independent of L-type Ca2+ channels.

Efficacy of a pneumococcal conjugate vaccine against acute otitis media.

BACKGROUND: Ear infections are a common cause of illness during the first two years of life. New conjugate vaccines may be able to prevent a substantial portion of cases of acute otitis media caused by Streptococcus pneumoniae. METHODS: We enrolled 1662 infants in a randomized, double-blind efficacy trial of a heptavalent pneumococcal polysaccharide conjugate vaccine in which the carrier protein is the nontoxic diphtheria-toxin analogue CRM197. The children received either the study vaccine or a hepatitis B vaccine as a control at 2, 4, 6, and 12 months of age. The clinical diagnosis of acute otitis media was based on predefined criteria, and the bacteriologic diagnosis was based on a culture of middle-ear fluid obtained by myringotomy. RESULTS: Of the children who were enrolled, 95.1 percent completed the trial. With the pneumococcal vaccine, there were more local reactions than with the hepatitis B vaccine but fewer than with the combined whole-cell diphtheria-tetanus-pertussis and Haemophilus influenzae type b vaccine that was administered simultaneously. There were 2596 episodes of acute otitis media during the follow-up period between 6.5 and 24 months of age. The vaccine reduced the number of episodes of acute otitis media from any cause by 6 percent (95 percent confidence interval, -4 to 16 percent [the negative number indicates a possible increase in the number of episodes]), culture-confirmed pneumococcal episodes by 34 percent (95 percent confidence interval, 21 to 45 percent), and the number of episodes due to the serotypes contained in the vaccine by 57 percent (95 percent confidence interval, 44 to 67 percent). The number of episodes attributed to serotypes that are cross-reactive with those in the vaccine was reduced by 51 percent, whereas the number of episodes due to all other serotypes increased by 33 percent. CONCLUSIONS: The heptavalent pneumococcal polysaccharide-CRM197 conjugate vaccine is safe and efficacious in the prevention of acute otitis media caused by the serotypes included in the vaccine.

Efficacy, safety and immunogenicity of heptavalent pneumococcal conjugate vaccine in children. Northern California Kaiser Permanente Vaccine Study Center Group.

OBJECTIVE: To determine the efficacy, safety and immunogenicity of the heptavalent CRM197 pneumococcal conjugate vaccine against invasive disease caused by vaccine serotypes and to determine the effectiveness of this vaccine against clinical episodes of otitis media. METHODS: The Wyeth Lederle Heptavalent CRM197 (PCV) was given to infants at 2, 4, 6 and 12 to 15 months of age in a double blind trial; 37,868 children were randomly assigned 1:1 to receive either the pneumococcal conjugate vaccine or meningococcus type C CRM197 conjugate. The primary study outcome was invasive disease caused by vaccine serotype. Other outcomes included overall impact on invasive disease regardless of serotype, effectiveness against clinical otitis media visits and episodes, impact against frequent and severe otitis media and ventilatory tube placement. In addition the serotype-specific efficacy against otitis media was estimated in an analysis of spontaneously draining ears. RESULTS: In the interim analysis in August, 1998, 17 of the 17 cases of invasive disease caused by vaccine serotype in fully vaccinated children and 5 of 5 of partially vaccinated cases occurred in the control group for a vaccine efficacy of 100%. Blinded case ascertainment was continued until April, 1999. As of that time 40 fully vaccinated cases of invasive disease caused by vaccine serotype had been identified, all but 1 in controls for an efficacy of 97.4% (95% confidence interval, 82.7 to 99.9%), and 52 cases, all but 3 in controls in the intent-to-treat analysis for an efficacy of 93.9% (95% confidence interval, 79.6 to 98.5%). There was no evidence of any increase of disease caused by nonvaccine serotypes. Efficacy for otitis media against visits, episodes, frequent otitis and ventilatory tube placement was 8.9, 7.0, 9.3 and 20.1% with P < 0.04 for all. In the analysis of spontaneously draining ears, serotype-specific effectiveness was 66.7%. CONCLUSION: This heptavalent pneumococcal conjugate appears to be highly effective in preventing invasive disease in young children and to have a significant impact on otitis media.

Which pneumococcal serogroups cause the most invasive disease: implications for conjugate vaccine formulation and use, part I.

We analyzed >70 recent data sets to compare the serogroups causing invasive pneumococcal disease (IPD) with those represented in conjugate vaccine formulations. Five to 8 and 10-11 serogroups comprise at least 75% of pneumococcal isolates from young children and older children/adults, respectively, in each geographic region. Serogroups in the 7-valent formulation (4, 6, 9, 14, 18, 19, and 23) cause 70%-88% of IPD in young children in the United States and Canada, Oceania, Africa, and Europe, and <65% in Latin America and Asia. Serogroups in the 9-valent formulation (7-valent+1, 5) cause 80%-90% of IPD in each region except Asia (66%). Serogroup 1 accounts for >6% of IPD in each region, including Europe, except the United States and Canada and Oceania. In contrast, several serogroups not found in 7-, 9-, and 11-valent conjugate formulations are significant causes of disease in older children/adults. Nevertheless, each conjugate formulation could prevent a substantial IPD burden in each region and age group.

The contribution of specific pneumococcal serogroups to different disease manifestations: implications for conjugate vaccine formulation and use, part II.

To assess whether certain serogroups of Streptococcus pneumoniae are preferentially associated with specific disease manifestations, we analyzed all recent pneumococcal disease studies and assessed the relative frequency of isolation of each serogroup by clinical site (as a proxy for different disease states). In all age groups, serogroups 1 and 14 were more often isolated from blood, and serogroups 6, 10, and 23 were more often isolated from cerebrospinal fluid (CSF); in young children, serogroups 3, 19, and 23 were more often isolated from middle ear fluid (MEF). Serogroups represented in conjugate vaccines were isolated slightly less frequently from CSF than from blood or MEF. Nonetheless, serogroups in the 9-valent conjugate vaccine formulation still comprised approximately 75% of pneumococcal isolates from the CSF of young children in Europe and in the United States and Canada. These analyses indicate that pneumococcal conjugate vaccines could potentially prevent a substantial proportion of episodes of bacteremic disease, pneumonia, meningitis, and otitis media, especially in young children.

Evaluation of a guinea pig model to assess interference in the immunogenicity of different components of a combination vaccine comprising diphtheria, tetanus and acellular pertussis (DTaP) vaccine and haemophilus influenzae type b capsular polysaccharide conjugate vaccine.

A guinea pig model to assess the immunogenicity of a combination vaccine containing diphtheria, tetanus and acellular pertussis (DTaP) vaccine and Haemophilus influenzae type b (Hib) capsular polysaccharide conjugated to tetanus toxoid (HibT) was evaluated comparatively with the mouse immunogenicity test to study the effect of combining these antigens on the immunogenicity of various components. The immunogenicity test in mice was performed by subcutaneous injection of groups of 10 animals twice at an interval of four weeks with 1/10 of a single human dose of various formulations of combination vaccines, DTaP or HibT vaccine. The animals were bled at 4 and 6 weeks and IgG or total antibodies to various components were determined by ELISA or RIA. The guinea pig immunogenicity model included groups of animals injected subcutaneously twice at an interval of six weeks with 1.5 times the single human dose of various formulations. The animals were bled at 4, 6 and 8 weeks and serum samples were tested for antibodies to various components by ELISA, RIA and/or neutralization tests. Additionally, potency of tetanus and diphtheria components was assessed as per the US Food and Drug Administration's regulations. Aluminium phosphate (AIPO(4)) adsorbed HibT vaccine or HibT as a combination with AIPO(4)adsorbed DTaP vaccine showed significant increases in IgG antibodies to tetanus toxin in mice as well increased tetanus antitoxin levels in guinea pigs as compared to soluble HibT vaccine. In general, combining DTaP and HibT vaccines did not affect the antibody levels to tetanus and diphtheria toxoids whereas DTaP-HibT combination vaccine elicited significantly lower IgG antibodies to pertussis toxin and filamentous haemagglutinin than DTaP vaccine alone, particularly after first injection. Mice showed similar Hib antibody responses for the combination and HibT alone whereas guinea pigs consistently showed lower anamnestic responses to Hib for combination formulations than for HibT alone. Reducing the amount of HibT and/or tetanus toxoid in the combination formulations reduced this suppression of Hib antibody response in guinea pigs. Suppression of Hib antibody response in combination vaccines has also been reported from recent clinical trials. Based on the results from this study, it appears that the guinea pig model may be able to predict the human response to various components of combination vaccines.

Simultaneous vitamin A administration at routine immunization contact enhances antibody response to diphtheria vaccine in infants younger than six months.

A randomized, double-blind, placebo-controlled trial was conducted to evaluate the effect of simultaneous vitamin A supplementation and diphtheria, pertussis and tetanus (DPT) vaccination on the antibody levels. Infants aged 6-17 wk (n = 56) were randomly given 15 mg oral vitamin A or placebo at the time of their DPT immunization. Three such doses were given at monthly intervals. Immunoglobulin (Ig) G antibodies to diphtheria, pertussis and tetanus were assayed on enrollment and 1 mo after the third dose. Baseline antibody concentrations to diphtheria, pertussis and tetanus did not differ between the vitamin A-supplemented and placebo-treated groups. The postdose antibody to diphtheria level was significantly greater in the vitamin A than in the placebo-treated group. The geometric mean +/- SEM antibody levels (mg/L) were 22.9 +/- 1.2 and 11.0 +/- 1.3 in the vitamin A and placebo groups, respectively (P = 0.029). The postsupplementation concentrations of antibodies to pertussis and tetanus did not differ between the two groups. These results suggest that antibody response to diphtheria vaccination was potentiated by simultaneous vitamin A administration and DPT immunization.

Safety and immunogenicity of heptavalent pneumococcal CRM197 conjugate vaccine in infants and toddlers.

OBJECTIVES: The objectives of this study were (1) to determine the safety and immunogenicity of heptavalent pneumococcal CRM197 conjugate (PNCRM7) vaccine in infants and (2) to determine the effect of concurrent hepatitis B immunization during the primary series and the effect of concurrent diphtheria and tetanus toxoid and acellular pertussis [DTaP (ACEL-IMUNE)] and conjugate CRM197 Haemophilus influenzae type b [HbOC (HibTITER) immunization at time of the booster dose on the safety and immunogenicity of PNCRM7and these other concurrently administered vaccines. METHODS: This was a randomized double-blinded study in 302 healthy infants in the Northern California Kaiser Permanente (NCKP) Health Plan. Infants received either PNCRM7 vaccine or meningococcal group C conjugate vaccine as a control at 2, 4 and 6 months of age and a booster at 12 to 15 months of age. Study design permitted the evaluation of immunology and safety of concurrent administration of routine vaccines. Antibody titers were determined on blood samples drawn before and 1 month after the primary series and the booster dose. RESULTS: After the third dose of PNCRM7 geometric mean concentrations (GMCs) ranged from 1.01 for serotype 9V to 3.72 microg/ml for serotype 14. More than 90% of all subjects had a post-third dose titer of > or =0.15 microg/ml for all serotypes, and the percentage of infants with a post-third dose titer of > or =1.0 microg/ml ranged from 51% for type 9V to 89% for type 14. After the PNCRM7 booster dose, the GMCs of all seven serotypes increased significantly over both post-Dose 3 and pre-Dose 4 antibody levels. In the primary series there were no significant differences in GMCs of pneumococcal antibodies between the subjects given PN-CRM7 alone or concurrently with hepatitis B vaccine. At the toddler dose concurrent administration of PNCRM7 and DTaP and HbOC resulted in a near conventional threshold for statistical significance of a post-Dose 4 GMC for serotype 23F [alone 6.75 mirog/ml vs. concurrent 4.11 microg/ml (P = 0.057)] as well as significantly lower antibody GMCs for H. influenza polyribosylribitol phosphate, diphtheria toxoid, pertussis toxin and filamentous hemagglutinin. For all antigens there were no differences between study groups in defined antibody titers that are considered protective. CONCLUSION: We conclude that PNCRM7 vaccine was safe and immunogenic. When this vaccine was administered concurrently at the booster dose with DTaP and HbOC vaccines, lower antibody titers were noted for some of the antigens when compared with the antibody response when PNCRM7 was given separately. Because the GMCs of the booster responses were all generally high and all subjects achieved similar percentages above predefined antibody titers, these differences are probably not clinically significant.

Treatment of severe pertussis: a study of the safety and pharmacology of intravenous pertussis immunoglobulin.

BACKGROUND: Pertussis in infants is often severe, resulting in complications and prolonged hospitalization. Treatment is limited to supportive care. Antibiotics do not significantly alter the course of the disease. Therapies directed at pertussis toxin, a major virulence factor of Bordetella pertussis, might be beneficial. This study examines the safety and pharmacology of intravenous pertussis immunoglobulin (P-IGIV), which has high levels of pertussis toxin antibodies. METHODS: P-IGIV was prepared as a 4% IgG solution from the pooled plasma from donors immunized with inactivated pertussis toxoid. The IgG pertussis toxin antibody concentration of 733 microg/ml is >7-fold higher than contained in conventional intravenous immunoglobulin products. Children with presumptive pertussis were allocated to one of three treatment doses of P-IGIV. RESULTS: Twenty-six of 30 enrolled children had confirmed pertussis. There were no adverse events associated with P-IGIV except one patient who had transient hypotension that responded to an infusion rate decrease. P-IGIV doses of 1500, 750 and 250 mg/kg achieved > or =4-fold, 3-fold and >2-fold rises in peak geometric mean titers of pertussis toxin IgG antibodies, respectively. P-IGIV exhibited a half-life of 38.4 days and a volume of distribution of 87.8 ml/kg. All three treatment groups showed declines in lymphocytosis (P < 0.05) and paroxysmal coughing by the third day after P-IGIV infusion compared with preinfusion values. CONCLUSION: P-IGIV is safe and achieves high pertussis toxin antibody titers in infants. This study provides data for a prospective, controlled trial of P-IGIV.

Protective effects of pertussis immunoglobulin (P-IGIV) in the aerosol challenge model.

Pertussis in infants is often severe, resulting in prolonged hospitalization. Treatment is limited to supportive care. Antibiotics do not significantly alter the course of the disease unless administered during the catarrhal phase. Therapies directed at pertussis toxin, a major virulence factor of Bordetella pertussis, may be beneficial. This study uses the aerosol challenge model to further examine the protective effects of P-IGIV, a new intravenous immunoglobulin product, which has high levels of pertussis toxin antibodies. P-IGIV was prepared as a 4% immunoglobulin G (IgG) solution from the pooled donor plasma from donors immunized with inactivated pertussis toxoid. The IgG pertussis toxin antibody concentration in P-IGIV is >7-fold higher than conventional intravenous immunoglobulin products. In the aerosol challenge model, P-IGIV-treated mice exhibited a dose-dependent decrease in mortality when monitored for 28 days postchallenge. P-IGIV in doses of 2,800, 1,400, and 350 mg/kg significantly reduced mortality compared to saline (P < 0.01)- and human IGIV (P < 0.01)-treated controls. The 50% protective dose of pertussis toxin antibodies in P-IGIV was 147 microg/ml. Recovery of weight gain and normalization of leukocyte counts occurred in all P-IGIV-treated groups but did not exhibit dose-dependent characteristics. Even after 7 days of infection, P-IGIV reversed the effects of pertussis in mice. This study provides further evidence that pertussis toxin antibodies not only play a role in passive protection but can also reverse symptoms of established disease in mice. We feel that P-IGIV deserves further evaluation in children hospitalized with severe pertussis.

Normal IgG and impaired IgM responses to polysaccharide vaccines in asplenic patients.

Asplenic patients are at increased risk for life-threatening infections with polysaccharide-encapsulated organisms, and reports of responses to polysaccharide vaccines have been conflicting. Thirty-six asplenic patients and 15 healthy controls were immunized with pneumococcal, Haemophilus influenzae type b (Hib), and meningococcal vaccines. Antibody concentrations to Hib and pneumococcal serotypes 14 and 18C were measured by ELISA. IgG antibody responses to all three antigens were similar in asplenic patients and controls at 28 days following immunization. In contrast, asplenic patients had significantly lower IgM concentrations in response to Hib (P<.05) and to both pneumococcal serotypes 14 (P<. 005) and 18C (P<.001). IgA anti-Hib antibody was also lower in the asplenic group, as was total anti-Hib antibody measured by RIA. These results document that IgG responses to polysaccharide vaccines are normal in asplenic patients. The impaired IgM responses of these patients may explain conflicting reports from studies that measured only total antibody-binding concentrations.

A simple and rapid method for measuring unconjugated capsular polysaccharide (PRP) of Haemophilus influenzae type b in PRP-tetanus toxoid conjugate vaccine.

The authors developed a simple and rapid method for quantitation of free capsular polysaccharide of Haemophilus influenzae type b (polyribosyl ribitol phosphate, PRP) in PRP-tetanus toxoid conjugate vaccine based on acid precipitation of tetanus toxoid (TT). Acid hydrolysis of PRP during the assay was not detected. The conditions used in the assay did not precipitate unconjugated PRP or adipic acid dihydrazide derivatized PRP. The method was highly reliable, reproducible and sensitive. The accuracy of the assay was confirmed by spiking known amounts of unconjugated PRP to PRP-TT conjugate preparations. A PRP-TT preparation, incubated at 37 degrees C for 6 months showing most of the PRP as unconjugated (87% determined by this method), was not immunogenic in mice for the PRP component even after two injections. In contrast, the same preparation held at 4 degrees C for 20 months, showing 17% unconjugated PRP, induced IgG antibodies to PRP which were boosted after second injection. Therefore, this method is very useful to evaluate the stability of PRP-TT conjugate vaccine. The assay may be useful for characterizing other polysaccharide-protein conjugate vaccines.

PCPP as a parenteral adjuvant for diverse antigens.

The adjuvanticity of the phosphazene polymer, poly[di(carboxylatophenoxy) phosphazene] (PCPP) was examined with a diverse collection of immunogens. PCPP proved to be a potent adjuvant for trivalent influenza virus vaccine, tetanus toxoid, hepatitis B surface antigen, herpes simplex virus glycoprotein gD2 and the capsular polysaccharide, polyribosylribitolphosphate, from Haemophilus influenzae type b. Taken together these results clearly demonstrate the general utility of PCPP as an adjuvant. Furthermore, PCPP was a superior adjuvant at least with TT compared to similar negatively charged polyanions, polymethylacrylic acid and polyacrylic acid.