[Show abstract][Hide abstract] ABSTRACT: 7vCRM (Pfizer, Inc.) and PHiD-CV (GlaxoSmithKline Biologicals) are two pneumococcal conjugate vaccines licensed for the prevention of invasive pneumococcal disease and acute otitis media caused by the vaccine serotypes of Streptococcus pneumoniae. Neither vaccine contains serotype 19A, but both contain the closely related serotype 19F. No decrease in the incidence of serotype 19A disease has been observed following the introduction of 7vCRM, suggesting that this serotype 19F-containing vaccine provides limited cross-protection against serotype 19A. To investigate the impact that conjugation methods may have on antipolysaccharide immune responses and to determine whether this limited cross-protection is characteristic of the serotype 19F polysaccharide or rather of the 19F-CRM (cross-reacting material) conjugate, we compared naturally induced antibodies against serotypes 19F and 19A with antibodies induced after vaccination with different pneumococcal conjugate vaccines. We found that conjugation of the serotype 19F polysaccharide using reductive amination (as in 7vCRM) resulted in the formation of at least one additional epitope that is not present in the native form of the 19F polysaccharide or following 19F conjugation using a bifunctional spacer (as in the prototype vaccine 7vOMPC) or cyanylation (as in PHiD-CV). We also found that pneumococcal vaccines conjugated using cyanylation induce more opsonophagocytic antibodies against serotype 19F and a considerably higher level of cross-opsonophagocytic antibodies against serotype 19A than vaccines conjugated using reductive amination. In conclusion, these results suggest that the conjugation method can influence the functionality of the antibodies induced against the homologous serotype 19F and the cross-reactive serotype 19A of S. pneumoniae.
[Show abstract][Hide abstract] ABSTRACT: A unique multicomponent vaccine against serogroup B meningococci incorporates the novel genome-derived proteins fHbp, NHBA, and NadA that may vary in sequence and level of expression. Measuring the effectiveness of such vaccines, using the accepted correlate of protection against invasive meningococcal disease, could require performing the serum bactericidal assay (SBA) against many diverse strains for each geographic region. This approach is impractical, especially for infants, where serum volumes are very limited. To address this, we developed the meningococcal antigen typing system (MATS) by combining a unique vaccine antigen-specific ELISA, which detects qualitative and quantitative differences in antigens, with PorA genotyping information. The ELISA correlates with killing of strains by SBA and measures both immunologic cross-reactivity and quantity of the antigens NHBA, NadA, and fHbp. We found that strains exceeding a threshold value in the ELISA for any of the three vaccine antigens had ≥80% probability of being killed by immune serum in the SBA. Strains positive for two or more antigens had a 96% probability of being killed. Inclusion of multiple different antigens in the vaccine improves breadth of coverage and prevents loss of coverage if one antigen mutates or is lost. The finding that a simple and high-throughput assay correlates with bactericidal activity is a milestone in meningococcal vaccine development. This assay allows typing of large panels of strains and prediction of coverage of protein-based meningococcal vaccines. Similar assays may be used for protein-based vaccines against other bacteria.
Proceedings of the National Academy of Sciences 10/2010; 107(45):19490-5. DOI:10.1073/pnas.1013758107 · 9.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The steps to produce, purify and control an immunogenic Brazilian conjugate vaccine against group C meningococcus (MenCPS-TT) using hydrazide-activated tetanus toxoid were developed. The conjugation methodology reduced the reaction time easily allowing scale-up. One freeze-dried pilot vaccine lot purified by tangential filtration, showed satisfactory quality control results including safety and stability. The pilot vaccine was immunogenic in mice in a dose-dependent fashion generating a 10-20-fold rise in IgG response in mice. The vaccine also induced high bactericidal titers. Vaccine concentrations of 1 and 0.1 microg showed higher avidity indices, suggesting induction of immunologic memory. These results support initiation of Phase I clinical studies with the MenCPS-TT conjugate vaccine.
[Show abstract][Hide abstract] ABSTRACT: Understanding the specificity of antibody response to Neisseria meningitidis serogroup B (Men B) is a key requirement for the development of an effective vaccine. This study was designed to investigate the antigen specificity of murine IgG1 and IgG2b antibodies induced by different primary immunization schedules and the booster dose with the Cuban Men B vaccine. Immunoblotting analyses were performed using outer membrane vesicles (OMV) from the vaccine strain (B:4,7:P1.19,15). IgG subclasses binding to PorA, PorB and RmpM were determined by digital scanning of the immunoreactive bands. Bactericidal antibody response after vaccination was also evaluated. The results indicated that IgG2b anti-PorA was the main antibody response induced by two doses of the vaccine. A primary series of three doses was found important for increasing IgG2b as well as IgG1 to PorB and RmpM. The fourth dose favoured the recognition of RmpM as detected by the increase of specific IgG1 and IgG2b. IgG subclasses anti-PorA did not change significantly if animals received two, three or four doses of the vaccine during the primary immunization or after the booster dose for all vaccine groups. The booster response to PorB and RmpM of groups BC2 and BC3 showed a significant increase in IgG2b levels compared with the primary response. However, the recall and the primary response of group BC4 were similar, suggesting a saturated dose-effect response after four doses of vaccine. The same was seen for bactericidal antibody response when human complement source was used in the assay.
[Show abstract][Hide abstract] ABSTRACT: Immunodeficiency is a barrier to successful vaccination in individuals with cancer and chronic infection. We performed a randomized phase 1/2 study in lymphopenic individuals after high-dose chemotherapy and autologous hematopoietic stem cell transplantation for myeloma. Combination immunotherapy consisting of a single early post-transplant infusion of in vivo vaccine-primed and ex vivo costimulated autologous T cells followed by post-transplant booster immunizations improved the severe immunodeficiency associated with high-dose chemotherapy and led to the induction of clinically relevant immunity in adults within a month after transplantation. Immune assays showed accelerated restoration of CD4 T-cell numbers and function. Early T-cell infusions also resulted in significantly improved T-cell proliferation in response to antigens that were not contained in the vaccine, as assessed by responses to staphylococcal enterotoxin B and cytomegalovirus antigens (P < 0.05). In the setting of lymphopenia, combined vaccine therapy and adoptive T-cell transfer fosters the development of enhanced memory T-cell responses.
Nature Medicine 12/2005; 11(11):1230-7. DOI:10.1038/nm1310 · 27.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Opsonophagocytosis is a correlate of protection that measures the functional activity of vaccine-induced antibodies. A standardized opsonophagocytosis assay (OPA) should be used as part of the evaluation of current and future pneumococcal (Pnc) polysaccharide (Ps)-based vaccines. We enrolled five laboratories to evaluate a previously standardized viability OPA. Each laboratory was provided with a detailed OPA protocol, seven target Pnc strains (serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F), two quality control sera and 12 paired sera (blinded) from adult donors who received one dose of the 23-valent Pnc Ps vaccine. Laboratories sent their results to the Centers for Disease Control and Prevention for analysis. Sera were tested in duplicate (single run), and the results were averaged to yield a single OPA titer (> or = 50% killing) for each serum sample. The percentage of sera within one or two dilutions of the calculated median OPA titer was determined for each laboratory and for each serotype. In general, laboratories were capable of detecting OPA titers within one or two dilutions of the median for at least 75 and 88%, respectively, of the sera tested. The level of agreement with the median OPA titers varied depending on the participating laboratory (overall agreement = 0.8 [99% confidence interval = 0.75 to 0.85]). All OPA median titers reported for quality control sera were within one dilution of the expected titer. We conclude that this OPA can be done in multiple laboratories with a high degree of interlaboratory reproducibility.
[Show abstract][Hide abstract] ABSTRACT: The specificity of the immune response to the 23-valent pneumococcal-polysaccharide (PS) vaccine in healthy adults and to a pneumococcal conjugate vaccine in infants was examined by measuring immunoglobulin G (IgG) antibody titers by enzyme-linked immunosorbent assay (ELISA) and the opsonophagocytosis assay. ELISA measures total antipneumococcal IgG titers including the titers of functional and nonfunctional antibodies, while the opsonophagocytosis assay measures only functional-antibody titers. Twenty-four pairs of pre- and post-pneumococcal vaccination sera from adults were evaluated (ELISA) for levels of IgG antibodies against serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F. Twelve of the pairs were also examined (opsonophagocytosis assay) for their functional activities. The correlation coefficients between assay results for most types ranged from 0.75 to 0.90, but the correlation coefficient was only about 0.6 for serotypes 4 and 19F. The specificities of these antibodies were further examined by the use of competitive ELISA inhibition. A number of heterologous polysaccharides (types 11A, 12F, 15B, 22F, and 33A) were used as inhibitors. Most of the sera tested showed cross-reacting antibodies, in addition to those removed by pneumococcal C PS absorption. Our data suggest the presence of a common epitope that is found on most pneumococcal PS but that is not absorbed by purified C PS. Use of a heterologous pneumococcal PS (22F) to adsorb the antibodies to the common epitope increased the correlation between the IgG ELISA results and the opsonophagocytosis assay results. The correlation coefficient improve from 0.66 to 0.92 for type 4 and from 0.63 to 0.80 for type 19F. These common-epitope antibodies were largely absent in infants at 7 months of age, suggesting the carbohydrate nature of the epitope.
[Show abstract][Hide abstract] ABSTRACT: Although meningococcal disease is rare in industrialized nations, Neisseria meningitidis holds a prominent position amongst pediatric infections because of the dramatic clinical presentation of the disease, high mortality, epidemic potential and the recent disappearance of many other important infectious diseases in developed countries through improvements in public health and vaccination. The precise nature of natural immunity to meningococci remains unknown, although a complex interaction between the organism and nasopharyngeal mucosal barrier, innate immune mechanisms and acquired immunity is involved. Study of the mechanisms of natural immunity may provide the key to development of vaccines that can reduce the burden of disease in early childhood.
[Show abstract][Hide abstract] ABSTRACT: Alternative strategies exist for prevention of group B Neisseria meningitidis (meningococcal) disease through vaccination (see Chapters 5 , 8 , 13 , 14 in this volume). However, the most promising approach to date has been the use of outer-membrane vesicle (OMV) vaccines for induction of bactericidal antibodies against cell-surface outer-membrane proteins (OMPs).
Methods in molecular medicine 01/2001; 66:81-107. DOI:10.1385/1-59259-148-5:81
[Show abstract][Hide abstract] ABSTRACT: The porin proteins of Neisseria meningitidis are important components of outer membrane protein (OMP) vaccines. The class 3 porin gene, porB, of a novel serogroup B, serotype 4, 15 isolate from Chile (Ch501) was found to be VR1-4, VR2-15, VR3-15 and VR4-15 by porB variable region (VR) typing. Rabbit immunization studies using outer membrane vesicles revealed immunodominance of individual PorB (class 3) VR epitopes. The predominant anti-Ch501 PorB response was directed to the VR1 epitope. Anti-PorB VR1 mediated killing was suggested by the bactericidal activity of Ch501 anti-sera against a type 4 strain not expressing PorA or class 5 OMPs. Studies that examine the molecular epidemiology of individual porB VRs, and the immune responses to PorB epitopes, may contribute to the development of broadly protective group B meningococcal vaccines.
[Show abstract][Hide abstract] ABSTRACT: Pneumococcal conjugate vaccines will eventually be licensed after favorable results from phase III efficacy trials. After licensure of a conjugate vaccine for invasive pneumococcal disease in infants, new conjugate vaccines will likely be licensed primarily on the basis of immunogenicity data rather than clinical efficacy. Analytical methods must therefore be developed, evaluated, and validated to compare immunogenicity results accurately within and between laboratories for different vaccines. At present no analytical technique is uniformly accepted and used in vaccine evaluation studies to determine the acceptable level of agreement between a laboratory result and the assigned value for a given serum sample. This multicenter study describes the magnitude of agreement among 12 laboratories quantifying an identical series of 48 pneumococcal serum specimens from 24 individuals (quality-control sera) by a consensus immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) developed for this study. After provisional or trial antibody concentrations were assigned to the quality-control serum samples for this study, four methods for comparison of a series of laboratory-determined values with the assigned concentrations were evaluated. The percent error between assigned values and laboratory-determined concentrations proved to be the most informative of the four methods. We present guidelines that a laboratory may follow to analyze a series of quality-control sera to determine if it can reproduce the assigned antibody concentrations within an acceptable level of tolerance. While this study focused on a pneumococcal IgG ELISA, the methods that we describe are easily generalizable to other immunological assays.
Journal of Clinical Microbiology 07/2000; 38(6):2043-50. · 3.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Antibodies reactive with C polysaccharide (PS) were found in healthy adults, pneumococcal patients, and vaccinees. These antibodies
were not directed to the phosphocholine determinant of the C PS, as they appear to be in mice, since the human antibodies
were inhibitable only with C PS. We found another population of phosphocholine-specific antibodies inhibitable only by phosphocholine
and related compounds.
Infection and Immunity 05/2000; 68(4):2333-7. DOI:10.1128/IAI.68.4.2333-2337.2000 · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Group B Streptococcus (GBS) is one of the most common organisms causing neonatal sepsis as well as serious infections in adults. Serotyping the organism is important in studying the epidemiology of the disease as well as deciding a course of treatment. There are several methods available for serotyping. Most of them need high-titered sera and are not quantitative. We are reporting a new inhibition enzyme-linked immunosorbent assay (ELISA) for serotyping which is sensitive and specific compared to the conventional methods but does not need high-titered serotype-specific antisera, as the specificity is controlled by the polysaccharide coating on the ELISA plates. The method can also be quantitative, and we have measured polysaccharide elaborated by different serotype V strains. Thus, the inhibition ELISA method will be useful in serotyping for epidemiological studies, assessing virulence, and performing strain selection for vaccine production.
Journal of Clinical Microbiology 09/1999; 37(8):2564-7. · 3.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We measured the capacity to opsonize Streptococcus pneumoniae serotype 6B and estimated the concentration of immunoglobulin G anti-6B capsular polysaccharide (PS) antibodies in 25 pre- and postimmune sera from adults immunized with a pneumococcal PS vaccine. We first studied two postvaccination serum samples displaying less opsonophagocytic capacity than expected. The majority of anti-6B antibodies in the two samples reacted with the capsular PSs of several unrelated serotypes (2, 4, 9V, 19F, and 23F) and with the lysate of noncapsulated S. pneumoniae bacteria but not with C-PS. The non-type-specific antibodies accounted for at least one-half of anti-6B antibodies in 40% of prevaccination sera and 10% of postvaccination sera from adults. The non-type-specific antibodies could be demonstrated in the enzyme-linked immunosorbent assays (ELISAs) for pneumococcal antibodies to other serotypes (4, 9V, 18C, 19F, and 23F). The nonspecific antibodies appear to bind a contaminant(s) in the current preparations of capsular PS. ELISA for antibodies to pneumococcal capsules may not be serotype specific for some samples.
[Show abstract][Hide abstract] ABSTRACT: The presence of immunoglobulin G (IgG) antibodies against group B streptococcus (GBS) type III polysaccharide (PS) has been correlated with protection against GBS disease. The GBS type III PS is structurally similar to the pneumococcal type 14 PS, differing only in the presence of sialic acid residues. Four different preparations of GBS type III PS were evaluated for their specificity in enzyme-linked immunosorbent assay (ELISA): free PS, free PS mixed with methylated human serum albumin (mHSA), PS conjugated to biotin and PS conjugated to human serum albumin. Three groups of human sera were used to evaluate these PS preparations: sera from recipients of a GBS PS vaccine, sera from women receiving a GBS type III PS-tetanus toxoid conjugate vaccine, and sera from nonimmunized healthy women of childbearing age. Estimated antibody concentrations were different depending on the PS preparation used. Using any of the four preparations, we were able to measure </=0.05 micrograms of IgG antibody to the GBS type III PS per ml. The specificity of the assay was determined by competitive inhibition with homologous and heterologous PS. The pneumococcal type 14 PS did not inhibit binding of antibody to the native GBS type III PS in sera from adults receiving the GBS PS vaccine or in sera from nonimmunized adults (except serum G9). The pneumococcal type 14 PS inhibited 50% in sera from recipients of GBS type III conjugate vaccine and in serum G9 when GBS type III PS conjugated to biotin or to HSA was used as antigen in ELISA. These data show that free GBS type III PS or PS mixed with mHSA is a sensitive and specific antigen for ELISA and that conjugation can alter the antigenic specificity of a PS.
Infection and Immunity 01/1999; 66(12):5848-53. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Neisseria meningitidis isolates are conventionally classified by serosubtyping, which characterizes the reactivities of the PorA outer membrane protein variable-region (VR) epitopes with monoclonal antibodies (MAbs). A newer method (PorA VR typing) uses predicted amino acid sequences derived from DNA sequence analysis. The resulting classification schemes are not standardized, offering conflicting and sometimes irreconcilable data from the two methods. In this paper, we propose a standardization of the PorA VR typing nomenclature that incorporates serologic information from traditional PorA serosubtyping with molecular data from predicted VR sequences. We performed a comprehensive literature and database search, generating a collection of strains and DNA sequences that reflects the diversity within PorA that exists to date. We have arranged this information in a comprehensive logical model that includes both serosubtype and PorA VR type assignments. Our data demonstrate that the current panel of serosubtype-defining MAbs underestimates PorA VR variability by at least 50%. Our proposal for VR typing is informative because amino acid sequence and serologic information, when serosubtype-defining MAbs are available, can be deduced simultaneously from the PorA VR designation. This scheme will be useful in future classification and applied epidemiologic studies of N. meningitidis, being a systematic way of selecting PorA vaccine candidates and analyzing vaccine coverage and failure.
[Show abstract][Hide abstract] ABSTRACT: Immunocompromise caused by HIV-1 infection increases the importance of receipt of routine childhood vaccines to prevent infections such as invasive Haemophilus influenzae type B (Hib) disease. The objectives of the study were to evaluate the immunogenicity of Hib conjugate vaccines among HIV-infected children according to clinical and immunologic disease progression as well as viral load.
The concentration of antibody to polyribosylribitol phosphate (PRP) was measured at approximately 9 and 24 months of age in plasma specimens from children of HIV-infected women enrolled in the Women and Infants Transmission Study.
Among 227 children (35 HIV-infected, 192 uninfected) at the 9-month study visit who were known to have received age-appropriate immunization with CRM197 mutant Corynebacterium diphtheriae protein-conjugated Hib vaccine, geometric mean antibody concentrations were lower among HIV-infected children (1.64 microg/ml) than among uninfected children (2.70 microg/ml), although the difference was not statistically significant. Anti-PRP antibody concentrations did not vary significantly among these HIV-infected children with predominantly mild-moderate disease progression according to clinical category, immunologic stage or viral load (P > or = 0.48). The proportion of children with antibody concentrations > or = 1.0 microg/ml did not vary significantly according to HIV infection status (73% uninfected, 74% infected) or, if infected, clinical or immunologic disease progression or viral load. Similar results were obtained among 127 children (17 HIV-infected, 110 uninfected) eligible for analysis at the 24-month study visit. Changes in antibody concentrations over time (between 9 and 24 months of age) did not differ significantly among 10 HIV-infected as compared with 72 uninfected children (P=0.81).
These results suggest that HIV-infected children with predominantly mild-moderate disease progression respond reasonably well in terms of a quantitative antibody response to Hib conjugate vaccines during the first 2 years of life. Research to further characterize the immune response to Hib conjugate vaccines and to further delineate the "durability" of anti-PRP antibody concentrations beyond 2 years of life should be pursued.
[Show abstract][Hide abstract] ABSTRACT: The current serological typing scheme for Neisseria meningitidis is not comprehensive; a proportion of isolates are not serotypeable. DNA sequence analysis and predicted amino acid sequences were used to characterize the structures of variable-region (VR) epitopes on N. meningitidis PorB proteins (PorB VR typing). Twenty-six porB gene sequences were obtained from GenBank and aligned with 41 new sequences. Primary amino acid structures predicted from those genes were grouped into 30 VR families of related variants that displayed at least 60% similarity. We correlated VR families with monoclonal antibody (MAb) reactivities, establishing a relationship between VR families and epitope locations for 15 serotype-defining MAbs. The current panel of serotype-defining MAbs underestimates by at least 50% the PorB VR variability because reagents for several major VR families are lacking or because a number of VR variants within some families are not recognized by serotype-defining MAbs. These difficulties, also reported for serosubtyping based on the PorA protein, are shown as inconsistent results between serological and sequence analyses, leading to inaccurate strain identification and incomplete epidemiological data. The information from this study enabled the expansion of the panel of MAbs currently available for serotyping, by including MAbs of previously undetermined specificities. Use of the expanded serotype panel enabled us to improve the sensitivity of serotyping by resolving a number of formerly nonserotypeable strains. In most cases, this information can be used to predict the VR family placement of unknown PorB proteins without sequencing the entire porB gene. PorB VR typing complements serotyping, and a combination of both techniques may be used for full characterization of meningococcal strains. The present work represents the most complete and integrated data set of PorB VR sequences and MAb reactivities of serogroup B and C meningococci produced to date.
[Show abstract][Hide abstract] ABSTRACT: An enzyme-linked immunosorbent assay (ELISA) and the antibody concentrations assigned to different pneumococcal capsular polysaccharide types were used to estimate concentrations of antibody to additional pneumococcal types in reference serum 89SF and to confirm assigned antibody values. This was possible because the slopes of curves of antibody binding to all polysaccharide types evaluated (1, 3, 4, 5, 6B, 7F, 9V, 14, 18C, 19F, and 23F) were similar. The point estimates for total anti-pneumococcal antibody and immunoglobulin G (IgG) antibody determined by cross-standardization by an ELISA based on use of methylated human serum albumin (mHSA) to improve the efficiency of polysaccharide binding to the ELISA plate differed by less than 40% from those reported by Quataert et al. (Clin. Diagn. Lab. Immunol. 2:590-597, 1995) for types 1, 4, 6B, 7F, 9V, 14, 18C, and 23F. However, large differences were found between the assigned values and those obtained by our mHSA ELISA for types 3 and 19F. The mHSA ELISA and the direct polysaccharide coat ELISA may not measure antibodies to the same epitopes on polysaccharides of types 3 and 19F. The functional importance of these different antibody specificities is being investigated. We have thus confirmed the assigned IgG antibody values for most types by a different method and have extended antibody assignments to several additional types.